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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
 
 /*
  * Common eBPF ELF object loading operations.
  *
  * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
  * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
  * Copyright (C) 2015 Huawei Inc.
  * Copyright (C) 2017 Nicira, Inc.
  * Copyright (C) 2019 Isovalent, Inc.
  */
 
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
 #include <libgen.h>
 #include <inttypes.h>
 #include <limits.h>
 #include <string.h>
 #include <unistd.h>
 #include <endian.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <ctype.h>
 #include <asm/unistd.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/bpf.h>
 #include <linux/btf.h>
 #include <linux/filter.h>
 #include <linux/limits.h>
 #include <linux/perf_event.h>
 #include <linux/ring_buffer.h>
 #include <linux/version.h>
 #include <sys/epoll.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
 #include <sys/utsname.h>
 #include <sys/resource.h>
 #include <libelf.h>
 #include <gelf.h>
 #include <zlib.h>
 
 #include "libbpf.h"
 #include "bpf.h"
 #include "btf.h"
 #include "str_error.h"
 #include "libbpf_internal.h"
 #include "hashmap.h"
 #include "bpf_gen_internal.h"
 
 #ifndef BPF_FS_MAGIC
 #define BPF_FS_MAGIC        0xcafe4a11
 #endif
 
 #define BPF_INSN_SZ (sizeof(struct bpf_insn))
 
 /* vsprintf() in __base_pr() uses nonliteral format string. It may break
  * compilation if user enables corresponding warning. Disable it explicitly.
  */
 #pragma GCC diagnostic ignored "-Wformat-nonliteral"
 
 #define __printf(a, b)  __attribute__((format(printf, a, b)))
 
 static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
 static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);
 
 static const char * const attach_type_name[] = {
     [BPF_CGROUP_INET_INGRESS]   = "cgroup_inet_ingress",
     [BPF_CGROUP_INET_EGRESS]    = "cgroup_inet_egress",
     [BPF_CGROUP_INET_SOCK_CREATE]   = "cgroup_inet_sock_create",
     [BPF_CGROUP_INET_SOCK_RELEASE]  = "cgroup_inet_sock_release",
     [BPF_CGROUP_SOCK_OPS]       = "cgroup_sock_ops",
     [BPF_CGROUP_DEVICE]     = "cgroup_device",
     [BPF_CGROUP_INET4_BIND]     = "cgroup_inet4_bind",
     [BPF_CGROUP_INET6_BIND]     = "cgroup_inet6_bind",
     [BPF_CGROUP_INET4_CONNECT]  = "cgroup_inet4_connect",
     [BPF_CGROUP_INET6_CONNECT]  = "cgroup_inet6_connect",
     [BPF_CGROUP_INET4_POST_BIND]    = "cgroup_inet4_post_bind",
     [BPF_CGROUP_INET6_POST_BIND]    = "cgroup_inet6_post_bind",
     [BPF_CGROUP_INET4_GETPEERNAME]  = "cgroup_inet4_getpeername",
     [BPF_CGROUP_INET6_GETPEERNAME]  = "cgroup_inet6_getpeername",
     [BPF_CGROUP_INET4_GETSOCKNAME]  = "cgroup_inet4_getsockname",
     [BPF_CGROUP_INET6_GETSOCKNAME]  = "cgroup_inet6_getsockname",
     [BPF_CGROUP_UDP4_SENDMSG]   = "cgroup_udp4_sendmsg",
     [BPF_CGROUP_UDP6_SENDMSG]   = "cgroup_udp6_sendmsg",
     [BPF_CGROUP_SYSCTL]     = "cgroup_sysctl",
     [BPF_CGROUP_UDP4_RECVMSG]   = "cgroup_udp4_recvmsg",
     [BPF_CGROUP_UDP6_RECVMSG]   = "cgroup_udp6_recvmsg",
     [BPF_CGROUP_GETSOCKOPT]     = "cgroup_getsockopt",
     [BPF_CGROUP_SETSOCKOPT]     = "cgroup_setsockopt",
     [BPF_SK_SKB_STREAM_PARSER]  = "sk_skb_stream_parser",
     [BPF_SK_SKB_STREAM_VERDICT] = "sk_skb_stream_verdict",
     [BPF_SK_SKB_VERDICT]        = "sk_skb_verdict",
     [BPF_SK_MSG_VERDICT]        = "sk_msg_verdict",
     [BPF_LIRC_MODE2]        = "lirc_mode2",
     [BPF_FLOW_DISSECTOR]        = "flow_dissector",
     [BPF_TRACE_RAW_TP]      = "trace_raw_tp",
     [BPF_TRACE_FENTRY]      = "trace_fentry",
     [BPF_TRACE_FEXIT]       = "trace_fexit",
     [BPF_MODIFY_RETURN]     = "modify_return",
     [BPF_LSM_MAC]           = "lsm_mac",
     [BPF_LSM_CGROUP]        = "lsm_cgroup",
     [BPF_SK_LOOKUP]         = "sk_lookup",
     [BPF_TRACE_ITER]        = "trace_iter",
     [BPF_XDP_DEVMAP]        = "xdp_devmap",
     [BPF_XDP_CPUMAP]        = "xdp_cpumap",
     [BPF_XDP]           = "xdp",
     [BPF_SK_REUSEPORT_SELECT]   = "sk_reuseport_select",
     [BPF_SK_REUSEPORT_SELECT_OR_MIGRATE]    = "sk_reuseport_select_or_migrate",
     [BPF_PERF_EVENT]        = "perf_event",
     [BPF_TRACE_KPROBE_MULTI]    = "trace_kprobe_multi",
 };
 
 static const char * const link_type_name[] = {
     [BPF_LINK_TYPE_UNSPEC]          = "unspec",
     [BPF_LINK_TYPE_RAW_TRACEPOINT]      = "raw_tracepoint",
     [BPF_LINK_TYPE_TRACING]         = "tracing",
     [BPF_LINK_TYPE_CGROUP]          = "cgroup",
     [BPF_LINK_TYPE_ITER]            = "iter",
     [BPF_LINK_TYPE_NETNS]           = "netns",
     [BPF_LINK_TYPE_XDP]         = "xdp",
     [BPF_LINK_TYPE_PERF_EVENT]      = "perf_event",
     [BPF_LINK_TYPE_KPROBE_MULTI]        = "kprobe_multi",
     [BPF_LINK_TYPE_STRUCT_OPS]      = "struct_ops",
 };
 
 static const char * const map_type_name[] = {
     [BPF_MAP_TYPE_UNSPEC]           = "unspec",
     [BPF_MAP_TYPE_HASH]         = "hash",
     [BPF_MAP_TYPE_ARRAY]            = "array",
     [BPF_MAP_TYPE_PROG_ARRAY]       = "prog_array",
     [BPF_MAP_TYPE_PERF_EVENT_ARRAY]     = "perf_event_array",
     [BPF_MAP_TYPE_PERCPU_HASH]      = "percpu_hash",
     [BPF_MAP_TYPE_PERCPU_ARRAY]     = "percpu_array",
     [BPF_MAP_TYPE_STACK_TRACE]      = "stack_trace",
     [BPF_MAP_TYPE_CGROUP_ARRAY]     = "cgroup_array",
     [BPF_MAP_TYPE_LRU_HASH]         = "lru_hash",
     [BPF_MAP_TYPE_LRU_PERCPU_HASH]      = "lru_percpu_hash",
     [BPF_MAP_TYPE_LPM_TRIE]         = "lpm_trie",
     [BPF_MAP_TYPE_ARRAY_OF_MAPS]        = "array_of_maps",
     [BPF_MAP_TYPE_HASH_OF_MAPS]     = "hash_of_maps",
     [BPF_MAP_TYPE_DEVMAP]           = "devmap",
     [BPF_MAP_TYPE_DEVMAP_HASH]      = "devmap_hash",
     [BPF_MAP_TYPE_SOCKMAP]          = "sockmap",
     [BPF_MAP_TYPE_CPUMAP]           = "cpumap",
     [BPF_MAP_TYPE_XSKMAP]           = "xskmap",
     [BPF_MAP_TYPE_SOCKHASH]         = "sockhash",
     [BPF_MAP_TYPE_CGROUP_STORAGE]       = "cgroup_storage",
     [BPF_MAP_TYPE_REUSEPORT_SOCKARRAY]  = "reuseport_sockarray",
     [BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE]    = "percpu_cgroup_storage",
     [BPF_MAP_TYPE_QUEUE]            = "queue",
     [BPF_MAP_TYPE_STACK]            = "stack",
     [BPF_MAP_TYPE_SK_STORAGE]       = "sk_storage",
     [BPF_MAP_TYPE_STRUCT_OPS]       = "struct_ops",
     [BPF_MAP_TYPE_RINGBUF]          = "ringbuf",
     [BPF_MAP_TYPE_INODE_STORAGE]        = "inode_storage",
     [BPF_MAP_TYPE_TASK_STORAGE]     = "task_storage",
     [BPF_MAP_TYPE_BLOOM_FILTER]     = "bloom_filter",
 };
 
 static const char * const prog_type_name[] = {
     [BPF_PROG_TYPE_UNSPEC]          = "unspec",
     [BPF_PROG_TYPE_SOCKET_FILTER]       = "socket_filter",
     [BPF_PROG_TYPE_KPROBE]          = "kprobe",
     [BPF_PROG_TYPE_SCHED_CLS]       = "sched_cls",
     [BPF_PROG_TYPE_SCHED_ACT]       = "sched_act",
     [BPF_PROG_TYPE_TRACEPOINT]      = "tracepoint",
     [BPF_PROG_TYPE_XDP]         = "xdp",
     [BPF_PROG_TYPE_PERF_EVENT]      = "perf_event",
     [BPF_PROG_TYPE_CGROUP_SKB]      = "cgroup_skb",
     [BPF_PROG_TYPE_CGROUP_SOCK]     = "cgroup_sock",
     [BPF_PROG_TYPE_LWT_IN]          = "lwt_in",
     [BPF_PROG_TYPE_LWT_OUT]         = "lwt_out",
     [BPF_PROG_TYPE_LWT_XMIT]        = "lwt_xmit",
     [BPF_PROG_TYPE_SOCK_OPS]        = "sock_ops",
     [BPF_PROG_TYPE_SK_SKB]          = "sk_skb",
     [BPF_PROG_TYPE_CGROUP_DEVICE]       = "cgroup_device",
     [BPF_PROG_TYPE_SK_MSG]          = "sk_msg",
     [BPF_PROG_TYPE_RAW_TRACEPOINT]      = "raw_tracepoint",
     [BPF_PROG_TYPE_CGROUP_SOCK_ADDR]    = "cgroup_sock_addr",
     [BPF_PROG_TYPE_LWT_SEG6LOCAL]       = "lwt_seg6local",
     [BPF_PROG_TYPE_LIRC_MODE2]      = "lirc_mode2",
     [BPF_PROG_TYPE_SK_REUSEPORT]        = "sk_reuseport",
     [BPF_PROG_TYPE_FLOW_DISSECTOR]      = "flow_dissector",
     [BPF_PROG_TYPE_CGROUP_SYSCTL]       = "cgroup_sysctl",
     [BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE] = "raw_tracepoint_writable",
     [BPF_PROG_TYPE_CGROUP_SOCKOPT]      = "cgroup_sockopt",
     [BPF_PROG_TYPE_TRACING]         = "tracing",
     [BPF_PROG_TYPE_STRUCT_OPS]      = "struct_ops",
     [BPF_PROG_TYPE_EXT]         = "ext",
     [BPF_PROG_TYPE_LSM]         = "lsm",
     [BPF_PROG_TYPE_SK_LOOKUP]       = "sk_lookup",
     [BPF_PROG_TYPE_SYSCALL]         = "syscall",
 };
 
 static int __base_pr(enum libbpf_print_level level, const char *format,
              va_list args)
 {
     if (level == LIBBPF_DEBUG)
         return 0;
 
     return vfprintf(stderr, format, args);
 }
 
 static libbpf_print_fn_t __libbpf_pr = __base_pr;
 
 libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn)
 {
     libbpf_print_fn_t old_print_fn = __libbpf_pr;
 
     __libbpf_pr = fn;
     return old_print_fn;
 }
 
 __printf(2, 3)
 void libbpf_print(enum libbpf_print_level level, const char *format, ...)
 {
     va_list args;
 
     if (!__libbpf_pr)
         return;
 
     va_start(args, format);
     __libbpf_pr(level, format, args);
     va_end(args);
 }
 
 static void pr_perm_msg(int err)
 {
     struct rlimit limit;
     char buf[100];
 
     if (err != -EPERM || geteuid() != 0)
         return;
 
     err = getrlimit(RLIMIT_MEMLOCK, &limit);
     if (err)
         return;
 
     if (limit.rlim_cur == RLIM_INFINITY)
         return;
 
     if (limit.rlim_cur < 1024)
         snprintf(buf, sizeof(buf), "%zu bytes", (size_t)limit.rlim_cur);
     else if (limit.rlim_cur < 1024*1024)
         snprintf(buf, sizeof(buf), "%.1f KiB", (double)limit.rlim_cur / 1024);
     else
         snprintf(buf, sizeof(buf), "%.1f MiB", (double)limit.rlim_cur / (1024*1024));
 
     pr_warn("permission error while running as root; try raising 'ulimit -l'? current value: %s\n",
         buf);
 }
 
 #define STRERR_BUFSIZE  128
 
 /* Copied from tools/perf/util/util.h */
 #ifndef zfree
 # define zfree(ptr) ({ free(*ptr); *ptr = NULL; })
 #endif
 
 #ifndef zclose
 # define zclose(fd) ({          \
     int ___err = 0;         \
     if ((fd) >= 0)          \
         ___err = close((fd));   \
     fd = -1;            \
     ___err; })
 #endif
 
 static inline __u64 ptr_to_u64(const void *ptr)
 {
     return (__u64) (unsigned long) ptr;
 }
 
 int libbpf_set_strict_mode(enum libbpf_strict_mode mode)
 {
     /* as of v1.0 libbpf_set_strict_mode() is a no-op */
     return 0;
 }
 
 __u32 libbpf_major_version(void)
 {
     return LIBBPF_MAJOR_VERSION;
 }
 
 __u32 libbpf_minor_version(void)
 {
     return LIBBPF_MINOR_VERSION;
 }
 
 const char *libbpf_version_string(void)
 {
 #define __S(X) #X
 #define _S(X) __S(X)
     return  "v" _S(LIBBPF_MAJOR_VERSION) "." _S(LIBBPF_MINOR_VERSION);
 #undef _S
 #undef __S
 }
 
 enum reloc_type {
     RELO_LD64,
     RELO_CALL,
     RELO_DATA,
     RELO_EXTERN_VAR,
     RELO_EXTERN_FUNC,
     RELO_SUBPROG_ADDR,
     RELO_CORE,
 };
 
 struct reloc_desc {
     enum reloc_type type;
     int insn_idx;
     union {
         const struct bpf_core_relo *core_relo; /* used when type == RELO_CORE */
         struct {
             int map_idx;
             int sym_off;
         };
     };
 };
 
 /* stored as sec_def->cookie for all libbpf-supported SEC()s */
 enum sec_def_flags {
     SEC_NONE = 0,
     /* expected_attach_type is optional, if kernel doesn't support that */
     SEC_EXP_ATTACH_OPT = 1,
     /* legacy, only used by libbpf_get_type_names() and
      * libbpf_attach_type_by_name(), not used by libbpf itself at all.
      * This used to be associated with cgroup (and few other) BPF programs
      * that were attachable through BPF_PROG_ATTACH command. Pretty
      * meaningless nowadays, though.
      */
     SEC_ATTACHABLE = 2,
     SEC_ATTACHABLE_OPT = SEC_ATTACHABLE | SEC_EXP_ATTACH_OPT,
     /* attachment target is specified through BTF ID in either kernel or
      * other BPF program's BTF object */
     SEC_ATTACH_BTF = 4,
     /* BPF program type allows sleeping/blocking in kernel */
     SEC_SLEEPABLE = 8,
     /* BPF program support non-linear XDP buffer */
     SEC_XDP_FRAGS = 16,
 };
 
 struct bpf_sec_def {
     char *sec;
     enum bpf_prog_type prog_type;
     enum bpf_attach_type expected_attach_type;
     long cookie;
     int handler_id;
 
     libbpf_prog_setup_fn_t prog_setup_fn;
     libbpf_prog_prepare_load_fn_t prog_prepare_load_fn;
     libbpf_prog_attach_fn_t prog_attach_fn;
 };
 
 /*
  * bpf_prog should be a better name but it has been used in
  * linux/filter.h.
  */
 struct bpf_program {
     char *name;
     char *sec_name;
     size_t sec_idx;
     const struct bpf_sec_def *sec_def;
     /* this program's instruction offset (in number of instructions)
      * within its containing ELF section
      */
     size_t sec_insn_off;
     /* number of original instructions in ELF section belonging to this
      * program, not taking into account subprogram instructions possible
      * appended later during relocation
      */
     size_t sec_insn_cnt;
     /* Offset (in number of instructions) of the start of instruction
      * belonging to this BPF program  within its containing main BPF
      * program. For the entry-point (main) BPF program, this is always
      * zero. For a sub-program, this gets reset before each of main BPF
      * programs are processed and relocated and is used to determined
      * whether sub-program was already appended to the main program, and
      * if yes, at which instruction offset.
      */
     size_t sub_insn_off;
 
     /* instructions that belong to BPF program; insns[0] is located at
      * sec_insn_off instruction within its ELF section in ELF file, so
      * when mapping ELF file instruction index to the local instruction,
      * one needs to subtract sec_insn_off; and vice versa.
      */
     struct bpf_insn *insns;
     /* actual number of instruction in this BPF program's image; for
      * entry-point BPF programs this includes the size of main program
      * itself plus all the used sub-programs, appended at the end
      */
     size_t insns_cnt;
 
     struct reloc_desc *reloc_desc;
     int nr_reloc;
 
     /* BPF verifier log settings */
     char *log_buf;
     size_t log_size;
     __u32 log_level;
 
     struct bpf_object *obj;
 
     int fd;
     bool autoload;
     bool mark_btf_static;
     enum bpf_prog_type type;
     enum bpf_attach_type expected_attach_type;
 
     int prog_ifindex;
     __u32 attach_btf_obj_fd;
     __u32 attach_btf_id;
     __u32 attach_prog_fd;
 
     void *func_info;
     __u32 func_info_rec_size;
     __u32 func_info_cnt;
 
     void *line_info;
     __u32 line_info_rec_size;
     __u32 line_info_cnt;
     __u32 prog_flags;
 };
 
 struct bpf_struct_ops {
     const char *tname;
     const struct btf_type *type;
     struct bpf_program **progs;
     __u32 *kern_func_off;
     /* e.g. struct tcp_congestion_ops in bpf_prog's btf format */
     void *data;
     /* e.g. struct bpf_struct_ops_tcp_congestion_ops in
      *      btf_vmlinux's format.
      * struct bpf_struct_ops_tcp_congestion_ops {
      *  [... some other kernel fields ...]
      *  struct tcp_congestion_ops data;
      * }
      * kern_vdata-size == sizeof(struct bpf_struct_ops_tcp_congestion_ops)
      * bpf_map__init_kern_struct_ops() will populate the "kern_vdata"
      * from "data".
      */
     void *kern_vdata;
     __u32 type_id;
 };
 
 #define DATA_SEC ".data"
 #define BSS_SEC ".bss"
 #define RODATA_SEC ".rodata"
 #define KCONFIG_SEC ".kconfig"
 #define KSYMS_SEC ".ksyms"
 #define STRUCT_OPS_SEC ".struct_ops"
 
 enum libbpf_map_type {
     LIBBPF_MAP_UNSPEC,
     LIBBPF_MAP_DATA,
     LIBBPF_MAP_BSS,
     LIBBPF_MAP_RODATA,
     LIBBPF_MAP_KCONFIG,
 };
 
 struct bpf_map_def {
     unsigned int type;
     unsigned int key_size;
     unsigned int value_size;
     unsigned int max_entries;
     unsigned int map_flags;
 };
 
 struct bpf_map {
     struct bpf_object *obj;
     char *name;
     /* real_name is defined for special internal maps (.rodata*,
      * .data*, .bss, .kconfig) and preserves their original ELF section
      * name. This is important to be be able to find corresponding BTF
      * DATASEC information.
      */
     char *real_name;
     int fd;
     int sec_idx;
     size_t sec_offset;
     int map_ifindex;
     int inner_map_fd;
     struct bpf_map_def def;
     __u32 numa_node;
     __u32 btf_var_idx;
     __u32 btf_key_type_id;
     __u32 btf_value_type_id;
     __u32 btf_vmlinux_value_type_id;
     enum libbpf_map_type libbpf_type;
     void *mmaped;
     struct bpf_struct_ops *st_ops;
     struct bpf_map *inner_map;
     void **init_slots;
     int init_slots_sz;
     char *pin_path;
     bool pinned;
     bool reused;
     bool autocreate;
     __u64 map_extra;
 };
 
 enum extern_type {
     EXT_UNKNOWN,
     EXT_KCFG,
     EXT_KSYM,
 };
 
 enum kcfg_type {
     KCFG_UNKNOWN,
     KCFG_CHAR,
     KCFG_BOOL,
     KCFG_INT,
     KCFG_TRISTATE,
     KCFG_CHAR_ARR,
 };
 
 struct extern_desc {
     enum extern_type type;
     int sym_idx;
     int btf_id;
     int sec_btf_id;
     const char *name;
     bool is_set;
     bool is_weak;
     union {
         struct {
             enum kcfg_type type;
             int sz;
             int align;
             int data_off;
             bool is_signed;
         } kcfg;
         struct {
             unsigned long long addr;
 
             /* target btf_id of the corresponding kernel var. */
             int kernel_btf_obj_fd;
             int kernel_btf_id;
 
             /* local btf_id of the ksym extern's type. */
             __u32 type_id;
             /* BTF fd index to be patched in for insn->off, this is
              * 0 for vmlinux BTF, index in obj->fd_array for module
              * BTF
              */
             __s16 btf_fd_idx;
         } ksym;
     };
 };
 
 struct module_btf {
     struct btf *btf;
     char *name;
     __u32 id;
     int fd;
     int fd_array_idx;
 };
 
 enum sec_type {
     SEC_UNUSED = 0,
     SEC_RELO,
     SEC_BSS,
     SEC_DATA,
     SEC_RODATA,
 };
 
 struct elf_sec_desc {
     enum sec_type sec_type;
     Elf64_Shdr *shdr;
     Elf_Data *data;
 };
 
 struct elf_state {
     int fd;
     const void *obj_buf;
     size_t obj_buf_sz;
     Elf *elf;
     Elf64_Ehdr *ehdr;
     Elf_Data *symbols;
     Elf_Data *st_ops_data;
     size_t shstrndx; /* section index for section name strings */
     size_t strtabidx;
     struct elf_sec_desc *secs;
     int sec_cnt;
     int maps_shndx;
     int btf_maps_shndx;
     __u32 btf_maps_sec_btf_id;
     int text_shndx;
     int symbols_shndx;
     int st_ops_shndx;
 };
 
 struct usdt_manager;
 
 struct bpf_object {
     char name[BPF_OBJ_NAME_LEN];
     char license[64];
     __u32 kern_version;
 
     struct bpf_program *programs;
     size_t nr_programs;
     struct bpf_map *maps;
     size_t nr_maps;
     size_t maps_cap;
 
     char *kconfig;
     struct extern_desc *externs;
     int nr_extern;
     int kconfig_map_idx;
 
     bool loaded;
     bool has_subcalls;
     bool has_rodata;
 
     struct bpf_gen *gen_loader;
 
     /* Information when doing ELF related work. Only valid if efile.elf is not NULL */
     struct elf_state efile;
 
     struct btf *btf;
     struct btf_ext *btf_ext;
 
     /* Parse and load BTF vmlinux if any of the programs in the object need
      * it at load time.
      */
     struct btf *btf_vmlinux;
     /* Path to the custom BTF to be used for BPF CO-RE relocations as an
      * override for vmlinux BTF.
      */
     char *btf_custom_path;
     /* vmlinux BTF override for CO-RE relocations */
     struct btf *btf_vmlinux_override;
     /* Lazily initialized kernel module BTFs */
     struct module_btf *btf_modules;
     bool btf_modules_loaded;
     size_t btf_module_cnt;
     size_t btf_module_cap;
 
     /* optional log settings passed to BPF_BTF_LOAD and BPF_PROG_LOAD commands */
     char *log_buf;
     size_t log_size;
     __u32 log_level;
 
     int *fd_array;
     size_t fd_array_cap;
     size_t fd_array_cnt;
 
     struct usdt_manager *usdt_man;
 
     char path[];
 };
 
 static const char *elf_sym_str(const struct bpf_object *obj, size_t off);
 static const char *elf_sec_str(const struct bpf_object *obj, size_t off);
 static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx);
 static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name);
 static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn);
 static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn);
 static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn);
 static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx);
 static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx);
 
 void bpf_program__unload(struct bpf_program *prog)
 {
     if (!prog)
         return;
 
     zclose(prog->fd);
 
     zfree(&prog->func_info);
     zfree(&prog->line_info);
 }
 
 static void bpf_program__exit(struct bpf_program *prog)
 {
     if (!prog)
         return;
 
     bpf_program__unload(prog);
     zfree(&prog->name);
     zfree(&prog->sec_name);
     zfree(&prog->insns);
     zfree(&prog->reloc_desc);
 
     prog->nr_reloc = 0;
     prog->insns_cnt = 0;
     prog->sec_idx = -1;
 }
 
 static bool insn_is_subprog_call(const struct bpf_insn *insn)
 {
     return BPF_CLASS(insn->code) == BPF_JMP &&
            BPF_OP(insn->code) == BPF_CALL &&
            BPF_SRC(insn->code) == BPF_K &&
            insn->src_reg == BPF_PSEUDO_CALL &&
            insn->dst_reg == 0 &&
            insn->off == 0;
 }
 
 static bool is_call_insn(const struct bpf_insn *insn)
 {
     return insn->code == (BPF_JMP | BPF_CALL);
 }
 
 static bool insn_is_pseudo_func(struct bpf_insn *insn)
 {
     return is_ldimm64_insn(insn) && insn->src_reg == BPF_PSEUDO_FUNC;
 }
 
 static int
 bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog,
               const char *name, size_t sec_idx, const char *sec_name,
               size_t sec_off, void *insn_data, size_t insn_data_sz)
 {
     if (insn_data_sz == 0 || insn_data_sz % BPF_INSN_SZ || sec_off % BPF_INSN_SZ) {
         pr_warn("sec '%s': corrupted program '%s', offset %zu, size %zu\n",
             sec_name, name, sec_off, insn_data_sz);
         return -EINVAL;
     }
 
     memset(prog, 0, sizeof(*prog));
     prog->obj = obj;
 
     prog->sec_idx = sec_idx;
     prog->sec_insn_off = sec_off / BPF_INSN_SZ;
     prog->sec_insn_cnt = insn_data_sz / BPF_INSN_SZ;
     /* insns_cnt can later be increased by appending used subprograms */
     prog->insns_cnt = prog->sec_insn_cnt;
 
     prog->type = BPF_PROG_TYPE_UNSPEC;
     prog->fd = -1;
 
     /* libbpf's convention for SEC("?abc...") is that it's just like
      * SEC("abc...") but the corresponding bpf_program starts out with
      * autoload set to false.
      */
     if (sec_name[0] == '?') {
         prog->autoload = false;
         /* from now on forget there was ? in section name */
         sec_name++;
     } else {
         prog->autoload = true;
     }
 
     /* inherit object's log_level */
     prog->log_level = obj->log_level;
 
     prog->sec_name = strdup(sec_name);
     if (!prog->sec_name)
         goto errout;
 
     prog->name = strdup(name);
     if (!prog->name)
         goto errout;
 
     prog->insns = malloc(insn_data_sz);
     if (!prog->insns)
         goto errout;
     memcpy(prog->insns, insn_data, insn_data_sz);
 
     return 0;
 errout:
     pr_warn("sec '%s': failed to allocate memory for prog '%s'\n", sec_name, name);
     bpf_program__exit(prog);
     return -ENOMEM;
 }
 
 static int
 bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
              const char *sec_name, int sec_idx)
 {
     Elf_Data *symbols = obj->efile.symbols;
     struct bpf_program *prog, *progs;
     void *data = sec_data->d_buf;
     size_t sec_sz = sec_data->d_size, sec_off, prog_sz, nr_syms;
     int nr_progs, err, i;
     const char *name;
     Elf64_Sym *sym;
 
     progs = obj->programs;
     nr_progs = obj->nr_programs;
     nr_syms = symbols->d_size / sizeof(Elf64_Sym);
     sec_off = 0;
 
     for (i = 0; i < nr_syms; i++) {
         sym = elf_sym_by_idx(obj, i);
 
         if (sym->st_shndx != sec_idx)
             continue;
         if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
             continue;
 
         prog_sz = sym->st_size;
         sec_off = sym->st_value;
 
         name = elf_sym_str(obj, sym->st_name);
         if (!name) {
             pr_warn("sec '%s': failed to get symbol name for offset %zu\n",
                 sec_name, sec_off);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         if (sec_off + prog_sz > sec_sz) {
             pr_warn("sec '%s': program at offset %zu crosses section boundary\n",
                 sec_name, sec_off);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         if (sec_idx != obj->efile.text_shndx && ELF64_ST_BIND(sym->st_info) == STB_LOCAL) {
             pr_warn("sec '%s': program '%s' is static and not supported\n", sec_name, name);
             return -ENOTSUP;
         }
 
         pr_debug("sec '%s': found program '%s' at insn offset %zu (%zu bytes), code size %zu insns (%zu bytes)\n",
              sec_name, name, sec_off / BPF_INSN_SZ, sec_off, prog_sz / BPF_INSN_SZ, prog_sz);
 
         progs = libbpf_reallocarray(progs, nr_progs + 1, sizeof(*progs));
         if (!progs) {
             /*
              * In this case the original obj->programs
              * is still valid, so don't need special treat for
              * bpf_close_object().
              */
             pr_warn("sec '%s': failed to alloc memory for new program '%s'\n",
                 sec_name, name);
             return -ENOMEM;
         }
         obj->programs = progs;
 
         prog = &progs[nr_progs];
 
         err = bpf_object__init_prog(obj, prog, name, sec_idx, sec_name,
                         sec_off, data + sec_off, prog_sz);
         if (err)
             return err;
 
         /* if function is a global/weak symbol, but has restricted
          * (STV_HIDDEN or STV_INTERNAL) visibility, mark its BTF FUNC
          * as static to enable more permissive BPF verification mode
          * with more outside context available to BPF verifier
          */
         if (ELF64_ST_BIND(sym->st_info) != STB_LOCAL
             && (ELF64_ST_VISIBILITY(sym->st_other) == STV_HIDDEN
             || ELF64_ST_VISIBILITY(sym->st_other) == STV_INTERNAL))
             prog->mark_btf_static = true;
 
         nr_progs++;
         obj->nr_programs = nr_progs;
     }
 
     return 0;
 }
 
 __u32 get_kernel_version(void)
 {
     /* On Ubuntu LINUX_VERSION_CODE doesn't correspond to info.release,
      * but Ubuntu provides /proc/version_signature file, as described at
      * https://ubuntu.com/kernel, with an example contents below, which we
      * can use to get a proper LINUX_VERSION_CODE.
      *
      *   Ubuntu 5.4.0-12.15-generic 5.4.8
      *
      * In the above, 5.4.8 is what kernel is actually expecting, while
      * uname() call will return 5.4.0 in info.release.
      */
     const char *ubuntu_kver_file = "/proc/version_signature";
     __u32 major, minor, patch;
     struct utsname info;
 
     if (access(ubuntu_kver_file, R_OK) == 0) {
         FILE *f;
 
         f = fopen(ubuntu_kver_file, "r");
         if (f) {
             if (fscanf(f, "%*s %*s %d.%d.%d\n", &major, &minor, &patch) == 3) {
                 fclose(f);
                 return KERNEL_VERSION(major, minor, patch);
             }
             fclose(f);
         }
         /* something went wrong, fall back to uname() approach */
     }
 
     uname(&info);
     if (sscanf(info.release, "%u.%u.%u", &major, &minor, &patch) != 3)
         return 0;
     return KERNEL_VERSION(major, minor, patch);
 }
 
 static const struct btf_member *
 find_member_by_offset(const struct btf_type *t, __u32 bit_offset)
 {
     struct btf_member *m;
     int i;
 
     for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
         if (btf_member_bit_offset(t, i) == bit_offset)
             return m;
     }
 
     return NULL;
 }
 
 static const struct btf_member *
 find_member_by_name(const struct btf *btf, const struct btf_type *t,
             const char *name)
 {
     struct btf_member *m;
     int i;
 
     for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
         if (!strcmp(btf__name_by_offset(btf, m->name_off), name))
             return m;
     }
 
     return NULL;
 }
 
 #define STRUCT_OPS_VALUE_PREFIX "bpf_struct_ops_"
 static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
                    const char *name, __u32 kind);
 
 static int
 find_struct_ops_kern_types(const struct btf *btf, const char *tname,
                const struct btf_type **type, __u32 *type_id,
                const struct btf_type **vtype, __u32 *vtype_id,
                const struct btf_member **data_member)
 {
     const struct btf_type *kern_type, *kern_vtype;
     const struct btf_member *kern_data_member;
     __s32 kern_vtype_id, kern_type_id;
     __u32 i;
 
     kern_type_id = btf__find_by_name_kind(btf, tname, BTF_KIND_STRUCT);
     if (kern_type_id < 0) {
         pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
             tname);
         return kern_type_id;
     }
     kern_type = btf__type_by_id(btf, kern_type_id);
 
     /* Find the corresponding "map_value" type that will be used
      * in map_update(BPF_MAP_TYPE_STRUCT_OPS).  For example,
      * find "struct bpf_struct_ops_tcp_congestion_ops" from the
      * btf_vmlinux.
      */
     kern_vtype_id = find_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX,
                         tname, BTF_KIND_STRUCT);
     if (kern_vtype_id < 0) {
         pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n",
             STRUCT_OPS_VALUE_PREFIX, tname);
         return kern_vtype_id;
     }
     kern_vtype = btf__type_by_id(btf, kern_vtype_id);
 
     /* Find "struct tcp_congestion_ops" from
      * struct bpf_struct_ops_tcp_congestion_ops {
      *  [ ... ]
      *  struct tcp_congestion_ops data;
      * }
      */
     kern_data_member = btf_members(kern_vtype);
     for (i = 0; i < btf_vlen(kern_vtype); i++, kern_data_member++) {
         if (kern_data_member->type == kern_type_id)
             break;
     }
     if (i == btf_vlen(kern_vtype)) {
         pr_warn("struct_ops init_kern: struct %s data is not found in struct %s%s\n",
             tname, STRUCT_OPS_VALUE_PREFIX, tname);
         return -EINVAL;
     }
 
     *type = kern_type;
     *type_id = kern_type_id;
     *vtype = kern_vtype;
     *vtype_id = kern_vtype_id;
     *data_member = kern_data_member;
 
     return 0;
 }
 
 static bool bpf_map__is_struct_ops(const struct bpf_map *map)
 {
     return map->def.type == BPF_MAP_TYPE_STRUCT_OPS;
 }
 
 /* Init the map's fields that depend on kern_btf */
 static int bpf_map__init_kern_struct_ops(struct bpf_map *map,
                      const struct btf *btf,
                      const struct btf *kern_btf)
 {
     const struct btf_member *member, *kern_member, *kern_data_member;
     const struct btf_type *type, *kern_type, *kern_vtype;
     __u32 i, kern_type_id, kern_vtype_id, kern_data_off;
     struct bpf_struct_ops *st_ops;
     void *data, *kern_data;
     const char *tname;
     int err;
 
     st_ops = map->st_ops;
     type = st_ops->type;
     tname = st_ops->tname;
     err = find_struct_ops_kern_types(kern_btf, tname,
                      &kern_type, &kern_type_id,
                      &kern_vtype, &kern_vtype_id,
                      &kern_data_member);
     if (err)
         return err;
 
     pr_debug("struct_ops init_kern %s: type_id:%u kern_type_id:%u kern_vtype_id:%u\n",
          map->name, st_ops->type_id, kern_type_id, kern_vtype_id);
 
     map->def.value_size = kern_vtype->size;
     map->btf_vmlinux_value_type_id = kern_vtype_id;
 
     st_ops->kern_vdata = calloc(1, kern_vtype->size);
     if (!st_ops->kern_vdata)
         return -ENOMEM;
 
     data = st_ops->data;
     kern_data_off = kern_data_member->offset / 8;
     kern_data = st_ops->kern_vdata + kern_data_off;
 
     member = btf_members(type);
     for (i = 0; i < btf_vlen(type); i++, member++) {
         const struct btf_type *mtype, *kern_mtype;
         __u32 mtype_id, kern_mtype_id;
         void *mdata, *kern_mdata;
         __s64 msize, kern_msize;
         __u32 moff, kern_moff;
         __u32 kern_member_idx;
         const char *mname;
 
         mname = btf__name_by_offset(btf, member->name_off);
         kern_member = find_member_by_name(kern_btf, kern_type, mname);
         if (!kern_member) {
             pr_warn("struct_ops init_kern %s: Cannot find member %s in kernel BTF\n",
                 map->name, mname);
             return -ENOTSUP;
         }
 
         kern_member_idx = kern_member - btf_members(kern_type);
         if (btf_member_bitfield_size(type, i) ||
             btf_member_bitfield_size(kern_type, kern_member_idx)) {
             pr_warn("struct_ops init_kern %s: bitfield %s is not supported\n",
                 map->name, mname);
             return -ENOTSUP;
         }
 
         moff = member->offset / 8;
         kern_moff = kern_member->offset / 8;
 
         mdata = data + moff;
         kern_mdata = kern_data + kern_moff;
 
         mtype = skip_mods_and_typedefs(btf, member->type, &mtype_id);
         kern_mtype = skip_mods_and_typedefs(kern_btf, kern_member->type,
                             &kern_mtype_id);
         if (BTF_INFO_KIND(mtype->info) !=
             BTF_INFO_KIND(kern_mtype->info)) {
             pr_warn("struct_ops init_kern %s: Unmatched member type %s %u != %u(kernel)\n",
                 map->name, mname, BTF_INFO_KIND(mtype->info),
                 BTF_INFO_KIND(kern_mtype->info));
             return -ENOTSUP;
         }
 
         if (btf_is_ptr(mtype)) {
             struct bpf_program *prog;
 
             prog = st_ops->progs[i];
             if (!prog)
                 continue;
 
             kern_mtype = skip_mods_and_typedefs(kern_btf,
                                 kern_mtype->type,
                                 &kern_mtype_id);
 
             /* mtype->type must be a func_proto which was
              * guaranteed in bpf_object__collect_st_ops_relos(),
              * so only check kern_mtype for func_proto here.
              */
             if (!btf_is_func_proto(kern_mtype)) {
                 pr_warn("struct_ops init_kern %s: kernel member %s is not a func ptr\n",
                     map->name, mname);
                 return -ENOTSUP;
             }
 
             prog->attach_btf_id = kern_type_id;
             prog->expected_attach_type = kern_member_idx;
 
             st_ops->kern_func_off[i] = kern_data_off + kern_moff;
 
             pr_debug("struct_ops init_kern %s: func ptr %s is set to prog %s from data(+%u) to kern_data(+%u)\n",
                  map->name, mname, prog->name, moff,
                  kern_moff);
 
             continue;
         }
 
         msize = btf__resolve_size(btf, mtype_id);
         kern_msize = btf__resolve_size(kern_btf, kern_mtype_id);
         if (msize < 0 || kern_msize < 0 || msize != kern_msize) {
             pr_warn("struct_ops init_kern %s: Error in size of member %s: %zd != %zd(kernel)\n",
                 map->name, mname, (ssize_t)msize,
                 (ssize_t)kern_msize);
             return -ENOTSUP;
         }
 
         pr_debug("struct_ops init_kern %s: copy %s %u bytes from data(+%u) to kern_data(+%u)\n",
              map->name, mname, (unsigned int)msize,
              moff, kern_moff);
         memcpy(kern_mdata, mdata, msize);
     }
 
     return 0;
 }
 
 static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
 {
     struct bpf_map *map;
     size_t i;
     int err;
 
     for (i = 0; i < obj->nr_maps; i++) {
         map = &obj->maps[i];
 
         if (!bpf_map__is_struct_ops(map))
             continue;
 
         err = bpf_map__init_kern_struct_ops(map, obj->btf,
                             obj->btf_vmlinux);
         if (err)
             return err;
     }
 
     return 0;
 }
 
 static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
 {
     const struct btf_type *type, *datasec;
     const struct btf_var_secinfo *vsi;
     struct bpf_struct_ops *st_ops;
     const char *tname, *var_name;
     __s32 type_id, datasec_id;
     const struct btf *btf;
     struct bpf_map *map;
     __u32 i;
 
     if (obj->efile.st_ops_shndx == -1)
         return 0;
 
     btf = obj->btf;
     datasec_id = btf__find_by_name_kind(btf, STRUCT_OPS_SEC,
                         BTF_KIND_DATASEC);
     if (datasec_id < 0) {
         pr_warn("struct_ops init: DATASEC %s not found\n",
             STRUCT_OPS_SEC);
         return -EINVAL;
     }
 
     datasec = btf__type_by_id(btf, datasec_id);
     vsi = btf_var_secinfos(datasec);
     for (i = 0; i < btf_vlen(datasec); i++, vsi++) {
         type = btf__type_by_id(obj->btf, vsi->type);
         var_name = btf__name_by_offset(obj->btf, type->name_off);
 
         type_id = btf__resolve_type(obj->btf, vsi->type);
         if (type_id < 0) {
             pr_warn("struct_ops init: Cannot resolve var type_id %u in DATASEC %s\n",
                 vsi->type, STRUCT_OPS_SEC);
             return -EINVAL;
         }
 
         type = btf__type_by_id(obj->btf, type_id);
         tname = btf__name_by_offset(obj->btf, type->name_off);
         if (!tname[0]) {
             pr_warn("struct_ops init: anonymous type is not supported\n");
             return -ENOTSUP;
         }
         if (!btf_is_struct(type)) {
             pr_warn("struct_ops init: %s is not a struct\n", tname);
             return -EINVAL;
         }
 
         map = bpf_object__add_map(obj);
         if (IS_ERR(map))
             return PTR_ERR(map);
 
         map->sec_idx = obj->efile.st_ops_shndx;
         map->sec_offset = vsi->offset;
         map->name = strdup(var_name);
         if (!map->name)
             return -ENOMEM;
 
         map->def.type = BPF_MAP_TYPE_STRUCT_OPS;
         map->def.key_size = sizeof(int);
         map->def.value_size = type->size;
         map->def.max_entries = 1;
 
         map->st_ops = calloc(1, sizeof(*map->st_ops));
         if (!map->st_ops)
             return -ENOMEM;
         st_ops = map->st_ops;
         st_ops->data = malloc(type->size);
         st_ops->progs = calloc(btf_vlen(type), sizeof(*st_ops->progs));
         st_ops->kern_func_off = malloc(btf_vlen(type) *
                            sizeof(*st_ops->kern_func_off));
         if (!st_ops->data || !st_ops->progs || !st_ops->kern_func_off)
             return -ENOMEM;
 
         if (vsi->offset + type->size > obj->efile.st_ops_data->d_size) {
             pr_warn("struct_ops init: var %s is beyond the end of DATASEC %s\n",
                 var_name, STRUCT_OPS_SEC);
             return -EINVAL;
         }
 
         memcpy(st_ops->data,
                obj->efile.st_ops_data->d_buf + vsi->offset,
                type->size);
         st_ops->tname = tname;
         st_ops->type = type;
         st_ops->type_id = type_id;
 
         pr_debug("struct_ops init: struct %s(type_id=%u) %s found at offset %u\n",
              tname, type_id, var_name, vsi->offset);
     }
 
     return 0;
 }
 
 static struct bpf_object *bpf_object__new(const char *path,
                       const void *obj_buf,
                       size_t obj_buf_sz,
                       const char *obj_name)
 {
     struct bpf_object *obj;
     char *end;
 
     obj = calloc(1, sizeof(struct bpf_object) + strlen(path) + 1);
     if (!obj) {
         pr_warn("alloc memory failed for %s\n", path);
         return ERR_PTR(-ENOMEM);
     }
 
     strcpy(obj->path, path);
     if (obj_name) {
         libbpf_strlcpy(obj->name, obj_name, sizeof(obj->name));
     } else {
         /* Using basename() GNU version which doesn't modify arg. */
         libbpf_strlcpy(obj->name, basename((void *)path), sizeof(obj->name));
         end = strchr(obj->name, '.');
         if (end)
             *end = 0;
     }
 
     obj->efile.fd = -1;
     /*
      * Caller of this function should also call
      * bpf_object__elf_finish() after data collection to return
      * obj_buf to user. If not, we should duplicate the buffer to
      * avoid user freeing them before elf finish.
      */
     obj->efile.obj_buf = obj_buf;
     obj->efile.obj_buf_sz = obj_buf_sz;
     obj->efile.maps_shndx = -1;
     obj->efile.btf_maps_shndx = -1;
     obj->efile.st_ops_shndx = -1;
     obj->kconfig_map_idx = -1;
 
     obj->kern_version = get_kernel_version();
     obj->loaded = false;
 
     return obj;
 }
 
 static void bpf_object__elf_finish(struct bpf_object *obj)
 {
     if (!obj->efile.elf)
         return;
 
     elf_end(obj->efile.elf);
     obj->efile.elf = NULL;
     obj->efile.symbols = NULL;
     obj->efile.st_ops_data = NULL;
 
     zfree(&obj->efile.secs);
     obj->efile.sec_cnt = 0;
     zclose(obj->efile.fd);
     obj->efile.obj_buf = NULL;
     obj->efile.obj_buf_sz = 0;
 }
 
 static int bpf_object__elf_init(struct bpf_object *obj)
 {
     Elf64_Ehdr *ehdr;
     int err = 0;
     Elf *elf;
 
     if (obj->efile.elf) {
         pr_warn("elf: init internal error\n");
         return -LIBBPF_ERRNO__LIBELF;
     }
 
     if (obj->efile.obj_buf_sz > 0) {
         /* obj_buf should have been validated by bpf_object__open_mem(). */
         elf = elf_memory((char *)obj->efile.obj_buf, obj->efile.obj_buf_sz);
     } else {
         obj->efile.fd = open(obj->path, O_RDONLY | O_CLOEXEC);
         if (obj->efile.fd < 0) {
             char errmsg[STRERR_BUFSIZE], *cp;
 
             err = -errno;
             cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
             pr_warn("elf: failed to open %s: %s\n", obj->path, cp);
             return err;
         }
 
         elf = elf_begin(obj->efile.fd, ELF_C_READ_MMAP, NULL);
     }
 
     if (!elf) {
         pr_warn("elf: failed to open %s as ELF file: %s\n", obj->path, elf_errmsg(-1));
         err = -LIBBPF_ERRNO__LIBELF;
         goto errout;
     }
 
     obj->efile.elf = elf;
 
     if (elf_kind(elf) != ELF_K_ELF) {
         err = -LIBBPF_ERRNO__FORMAT;
         pr_warn("elf: '%s' is not a proper ELF object\n", obj->path);
         goto errout;
     }
 
     if (gelf_getclass(elf) != ELFCLASS64) {
         err = -LIBBPF_ERRNO__FORMAT;
         pr_warn("elf: '%s' is not a 64-bit ELF object\n", obj->path);
         goto errout;
     }
 
     obj->efile.ehdr = ehdr = elf64_getehdr(elf);
     if (!obj->efile.ehdr) {
         pr_warn("elf: failed to get ELF header from %s: %s\n", obj->path, elf_errmsg(-1));
         err = -LIBBPF_ERRNO__FORMAT;
         goto errout;
     }
 
     if (elf_getshdrstrndx(elf, &obj->efile.shstrndx)) {
         pr_warn("elf: failed to get section names section index for %s: %s\n",
             obj->path, elf_errmsg(-1));
         err = -LIBBPF_ERRNO__FORMAT;
         goto errout;
     }
 
     /* Elf is corrupted/truncated, avoid calling elf_strptr. */
     if (!elf_rawdata(elf_getscn(elf, obj->efile.shstrndx), NULL)) {
         pr_warn("elf: failed to get section names strings from %s: %s\n",
             obj->path, elf_errmsg(-1));
         err = -LIBBPF_ERRNO__FORMAT;
         goto errout;
     }
 
     /* Old LLVM set e_machine to EM_NONE */
     if (ehdr->e_type != ET_REL || (ehdr->e_machine && ehdr->e_machine != EM_BPF)) {
         pr_warn("elf: %s is not a valid eBPF object file\n", obj->path);
         err = -LIBBPF_ERRNO__FORMAT;
         goto errout;
     }
 
     return 0;
 errout:
     bpf_object__elf_finish(obj);
     return err;
 }
 
 static int bpf_object__check_endianness(struct bpf_object *obj)
 {
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
     if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
         return 0;
 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
     if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
         return 0;
 #else
 # error "Unrecognized __BYTE_ORDER__"
 #endif
     pr_warn("elf: endianness mismatch in %s.\n", obj->path);
     return -LIBBPF_ERRNO__ENDIAN;
 }
 
 static int
 bpf_object__init_license(struct bpf_object *obj, void *data, size_t size)
 {
     /* libbpf_strlcpy() only copies first N - 1 bytes, so size + 1 won't
      * go over allowed ELF data section buffer
      */
     libbpf_strlcpy(obj->license, data, min(size + 1, sizeof(obj->license)));
     pr_debug("license of %s is %s\n", obj->path, obj->license);
     return 0;
 }
 
 static int
 bpf_object__init_kversion(struct bpf_object *obj, void *data, size_t size)
 {
     __u32 kver;
 
     if (size != sizeof(kver)) {
         pr_warn("invalid kver section in %s\n", obj->path);
         return -LIBBPF_ERRNO__FORMAT;
     }
     memcpy(&kver, data, sizeof(kver));
     obj->kern_version = kver;
     pr_debug("kernel version of %s is %x\n", obj->path, obj->kern_version);
     return 0;
 }
 
 static bool bpf_map_type__is_map_in_map(enum bpf_map_type type)
 {
     if (type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
         type == BPF_MAP_TYPE_HASH_OF_MAPS)
         return true;
     return false;
 }
 
 static int find_elf_sec_sz(const struct bpf_object *obj, const char *name, __u32 *size)
 {
     Elf_Data *data;
     Elf_Scn *scn;
 
     if (!name)
         return -EINVAL;
 
     scn = elf_sec_by_name(obj, name);
     data = elf_sec_data(obj, scn);
     if (data) {
         *size = data->d_size;
         return 0; /* found it */
     }
 
     return -ENOENT;
 }
 
 static int find_elf_var_offset(const struct bpf_object *obj, const char *name, __u32 *off)
 {
     Elf_Data *symbols = obj->efile.symbols;
     const char *sname;
     size_t si;
 
     if (!name || !off)
         return -EINVAL;
 
     for (si = 0; si < symbols->d_size / sizeof(Elf64_Sym); si++) {
         Elf64_Sym *sym = elf_sym_by_idx(obj, si);
 
         if (ELF64_ST_TYPE(sym->st_info) != STT_OBJECT)
             continue;
 
         if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
             ELF64_ST_BIND(sym->st_info) != STB_WEAK)
             continue;
 
         sname = elf_sym_str(obj, sym->st_name);
         if (!sname) {
             pr_warn("failed to get sym name string for var %s\n", name);
             return -EIO;
         }
         if (strcmp(name, sname) == 0) {
             *off = sym->st_value;
             return 0;
         }
     }
 
     return -ENOENT;
 }
 
 static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
 {
     struct bpf_map *map;
     int err;
 
     err = libbpf_ensure_mem((void **)&obj->maps, &obj->maps_cap,
                 sizeof(*obj->maps), obj->nr_maps + 1);
     if (err)
         return ERR_PTR(err);
 
     map = &obj->maps[obj->nr_maps++];
     map->obj = obj;
     map->fd = -1;
     map->inner_map_fd = -1;
     map->autocreate = true;
 
     return map;
 }
 
 static size_t bpf_map_mmap_sz(const struct bpf_map *map)
 {
     long page_sz = sysconf(_SC_PAGE_SIZE);
     size_t map_sz;
 
     map_sz = (size_t)roundup(map->def.value_size, 8) * map->def.max_entries;
     map_sz = roundup(map_sz, page_sz);
     return map_sz;
 }
 
 static char *internal_map_name(struct bpf_object *obj, const char *real_name)
 {
     char map_name[BPF_OBJ_NAME_LEN], *p;
     int pfx_len, sfx_len = max((size_t)7, strlen(real_name));
 
     /* This is one of the more confusing parts of libbpf for various
      * reasons, some of which are historical. The original idea for naming
      * internal names was to include as much of BPF object name prefix as
      * possible, so that it can be distinguished from similar internal
      * maps of a different BPF object.
      * As an example, let's say we have bpf_object named 'my_object_name'
      * and internal map corresponding to '.rodata' ELF section. The final
      * map name advertised to user and to the kernel will be
      * 'my_objec.rodata', taking first 8 characters of object name and
      * entire 7 characters of '.rodata'.
      * Somewhat confusingly, if internal map ELF section name is shorter
      * than 7 characters, e.g., '.bss', we still reserve 7 characters
      * for the suffix, even though we only have 4 actual characters, and
      * resulting map will be called 'my_objec.bss', not even using all 15
      * characters allowed by the kernel. Oh well, at least the truncated
      * object name is somewhat consistent in this case. But if the map
      * name is '.kconfig', we'll still have entirety of '.kconfig' added
      * (8 chars) and thus will be left with only first 7 characters of the
      * object name ('my_obje'). Happy guessing, user, that the final map
      * name will be "my_obje.kconfig".
      * Now, with libbpf starting to support arbitrarily named .rodata.*
      * and .data.* data sections, it's possible that ELF section name is
      * longer than allowed 15 chars, so we now need to be careful to take
      * only up to 15 first characters of ELF name, taking no BPF object
      * name characters at all. So '.rodata.abracadabra' will result in
      * '.rodata.abracad' kernel and user-visible name.
      * We need to keep this convoluted logic intact for .data, .bss and
      * .rodata maps, but for new custom .data.custom and .rodata.custom
      * maps we use their ELF names as is, not prepending bpf_object name
      * in front. We still need to truncate them to 15 characters for the
      * kernel. Full name can be recovered for such maps by using DATASEC
      * BTF type associated with such map's value type, though.
      */
     if (sfx_len >= BPF_OBJ_NAME_LEN)
         sfx_len = BPF_OBJ_NAME_LEN - 1;
 
     /* if there are two or more dots in map name, it's a custom dot map */
     if (strchr(real_name + 1, '.') != NULL)
         pfx_len = 0;
     else
         pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1, strlen(obj->name));
 
     snprintf(map_name, sizeof(map_name), "%.*s%.*s", pfx_len, obj->name,
          sfx_len, real_name);
 
     /* sanitise map name to characters allowed by kernel */
     for (p = map_name; *p && p < map_name + sizeof(map_name); p++)
         if (!isalnum(*p) && *p != '_' && *p != '.')
             *p = '_';
 
     return strdup(map_name);
 }
 
 static int
 bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map);
 
 static int
 bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
                   const char *real_name, int sec_idx, void *data, size_t data_sz)
 {
     struct bpf_map_def *def;
     struct bpf_map *map;
     int err;
 
     map = bpf_object__add_map(obj);
     if (IS_ERR(map))
         return PTR_ERR(map);
 
     map->libbpf_type = type;
     map->sec_idx = sec_idx;
     map->sec_offset = 0;
     map->real_name = strdup(real_name);
     map->name = internal_map_name(obj, real_name);
     if (!map->real_name || !map->name) {
         zfree(&map->real_name);
         zfree(&map->name);
         return -ENOMEM;
     }
 
     def = &map->def;
     def->type = BPF_MAP_TYPE_ARRAY;
     def->key_size = sizeof(int);
     def->value_size = data_sz;
     def->max_entries = 1;
     def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_KCONFIG
              ? BPF_F_RDONLY_PROG : 0;
     def->map_flags |= BPF_F_MMAPABLE;
 
     pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n",
          map->name, map->sec_idx, map->sec_offset, def->map_flags);
 
     map->mmaped = mmap(NULL, bpf_map_mmap_sz(map), PROT_READ | PROT_WRITE,
                MAP_SHARED | MAP_ANONYMOUS, -1, 0);
     if (map->mmaped == MAP_FAILED) {
         err = -errno;
         map->mmaped = NULL;
         pr_warn("failed to alloc map '%s' content buffer: %d\n",
             map->name, err);
         zfree(&map->real_name);
         zfree(&map->name);
         return err;
     }
 
     /* failures are fine because of maps like .rodata.str1.1 */
     (void) bpf_map_find_btf_info(obj, map);
 
     if (data)
         memcpy(map->mmaped, data, data_sz);
 
     pr_debug("map %td is \"%s\"\n", map - obj->maps, map->name);
     return 0;
 }
 
 static int bpf_object__init_global_data_maps(struct bpf_object *obj)
 {
     struct elf_sec_desc *sec_desc;
     const char *sec_name;
     int err = 0, sec_idx;
 
     /*
      * Populate obj->maps with libbpf internal maps.
      */
     for (sec_idx = 1; sec_idx < obj->efile.sec_cnt; sec_idx++) {
         sec_desc = &obj->efile.secs[sec_idx];
 
         switch (sec_desc->sec_type) {
         case SEC_DATA:
             sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
             err = bpf_object__init_internal_map(obj, LIBBPF_MAP_DATA,
                                 sec_name, sec_idx,
                                 sec_desc->data->d_buf,
                                 sec_desc->data->d_size);
             break;
         case SEC_RODATA:
             obj->has_rodata = true;
             sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
             err = bpf_object__init_internal_map(obj, LIBBPF_MAP_RODATA,
                                 sec_name, sec_idx,
                                 sec_desc->data->d_buf,
                                 sec_desc->data->d_size);
             break;
         case SEC_BSS:
             sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
             err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS,
                                 sec_name, sec_idx,
                                 NULL,
                                 sec_desc->data->d_size);
             break;
         default:
             /* skip */
             break;
         }
         if (err)
             return err;
     }
     return 0;
 }
 
 
 static struct extern_desc *find_extern_by_name(const struct bpf_object *obj,
                            const void *name)
 {
     int i;
 
     for (i = 0; i < obj->nr_extern; i++) {
         if (strcmp(obj->externs[i].name, name) == 0)
             return &obj->externs[i];
     }
     return NULL;
 }
 
 static int set_kcfg_value_tri(struct extern_desc *ext, void *ext_val,
                   char value)
 {
     switch (ext->kcfg.type) {
     case KCFG_BOOL:
         if (value == 'm') {
             pr_warn("extern (kcfg) '%s': value '%c' implies tristate or char type\n",
                 ext->name, value);
             return -EINVAL;
         }
         *(bool *)ext_val = value == 'y' ? true : false;
         break;
     case KCFG_TRISTATE:
         if (value == 'y')
             *(enum libbpf_tristate *)ext_val = TRI_YES;
         else if (value == 'm')
             *(enum libbpf_tristate *)ext_val = TRI_MODULE;
         else /* value == 'n' */
             *(enum libbpf_tristate *)ext_val = TRI_NO;
         break;
     case KCFG_CHAR:
         *(char *)ext_val = value;
         break;
     case KCFG_UNKNOWN:
     case KCFG_INT:
     case KCFG_CHAR_ARR:
     default:
         pr_warn("extern (kcfg) '%s': value '%c' implies bool, tristate, or char type\n",
             ext->name, value);
         return -EINVAL;
     }
     ext->is_set = true;
     return 0;
 }
 
 static int set_kcfg_value_str(struct extern_desc *ext, char *ext_val,
                   const char *value)
 {
     size_t len;
 
     if (ext->kcfg.type != KCFG_CHAR_ARR) {
         pr_warn("extern (kcfg) '%s': value '%s' implies char array type\n",
             ext->name, value);
         return -EINVAL;
     }
 
     len = strlen(value);
     if (value[len - 1] != '"') {
         pr_warn("extern (kcfg) '%s': invalid string config '%s'\n",
             ext->name, value);
         return -EINVAL;
     }
 
     /* strip quotes */
     len -= 2;
     if (len >= ext->kcfg.sz) {
         pr_warn("extern (kcfg) '%s': long string '%s' of (%zu bytes) truncated to %d bytes\n",
             ext->name, value, len, ext->kcfg.sz - 1);
         len = ext->kcfg.sz - 1;
     }
     memcpy(ext_val, value + 1, len);
     ext_val[len] = '\0';
     ext->is_set = true;
     return 0;
 }
 
 static int parse_u64(const char *value, __u64 *res)
 {
     char *value_end;
     int err;
 
     errno = 0;
     *res = strtoull(value, &value_end, 0);
     if (errno) {
         err = -errno;
         pr_warn("failed to parse '%s' as integer: %d\n", value, err);
         return err;
     }
     if (*value_end) {
         pr_warn("failed to parse '%s' as integer completely\n", value);
         return -EINVAL;
     }
     return 0;
 }
 
 static bool is_kcfg_value_in_range(const struct extern_desc *ext, __u64 v)
 {
     int bit_sz = ext->kcfg.sz * 8;
 
     if (ext->kcfg.sz == 8)
         return true;
 
     /* Validate that value stored in u64 fits in integer of `ext->sz`
      * bytes size without any loss of information. If the target integer
      * is signed, we rely on the following limits of integer type of
      * Y bits and subsequent transformation:
      *
      *     -2^(Y-1) <= X           <= 2^(Y-1) - 1
      *            0 <= X + 2^(Y-1) <= 2^Y - 1
      *            0 <= X + 2^(Y-1) <  2^Y
      *
      *  For unsigned target integer, check that all the (64 - Y) bits are
      *  zero.
      */
     if (ext->kcfg.is_signed)
         return v + (1ULL << (bit_sz - 1)) < (1ULL << bit_sz);
     else
         return (v >> bit_sz) == 0;
 }
 
 static int set_kcfg_value_num(struct extern_desc *ext, void *ext_val,
                   __u64 value)
 {
     if (ext->kcfg.type != KCFG_INT && ext->kcfg.type != KCFG_CHAR &&
         ext->kcfg.type != KCFG_BOOL) {
         pr_warn("extern (kcfg) '%s': value '%llu' implies integer, char, or boolean type\n",
             ext->name, (unsigned long long)value);
         return -EINVAL;
     }
     if (ext->kcfg.type == KCFG_BOOL && value > 1) {
         pr_warn("extern (kcfg) '%s': value '%llu' isn't boolean compatible\n",
             ext->name, (unsigned long long)value);
         return -EINVAL;
 
     }
     if (!is_kcfg_value_in_range(ext, value)) {
         pr_warn("extern (kcfg) '%s': value '%llu' doesn't fit in %d bytes\n",
             ext->name, (unsigned long long)value, ext->kcfg.sz);
         return -ERANGE;
     }
     switch (ext->kcfg.sz) {
         case 1: *(__u8 *)ext_val = value; break;
         case 2: *(__u16 *)ext_val = value; break;
         case 4: *(__u32 *)ext_val = value; break;
         case 8: *(__u64 *)ext_val = value; break;
         default:
             return -EINVAL;
     }
     ext->is_set = true;
     return 0;
 }
 
 static int bpf_object__process_kconfig_line(struct bpf_object *obj,
                         char *buf, void *data)
 {
     struct extern_desc *ext;
     char *sep, *value;
     int len, err = 0;
     void *ext_val;
     __u64 num;
 
     if (!str_has_pfx(buf, "CONFIG_"))
         return 0;
 
     sep = strchr(buf, '=');
     if (!sep) {
         pr_warn("failed to parse '%s': no separator\n", buf);
         return -EINVAL;
     }
 
     /* Trim ending '\n' */
     len = strlen(buf);
     if (buf[len - 1] == '\n')
         buf[len - 1] = '\0';
     /* Split on '=' and ensure that a value is present. */
     *sep = '\0';
     if (!sep[1]) {
         *sep = '=';
         pr_warn("failed to parse '%s': no value\n", buf);
         return -EINVAL;
     }
 
     ext = find_extern_by_name(obj, buf);
     if (!ext || ext->is_set)
         return 0;
 
     ext_val = data + ext->kcfg.data_off;
     value = sep + 1;
 
     switch (*value) {
     case 'y': case 'n': case 'm':
         err = set_kcfg_value_tri(ext, ext_val, *value);
         break;
     case '"':
         err = set_kcfg_value_str(ext, ext_val, value);
         break;
     default:
         /* assume integer */
         err = parse_u64(value, &num);
         if (err) {
             pr_warn("extern (kcfg) '%s': value '%s' isn't a valid integer\n", ext->name, value);
             return err;
         }
         if (ext->kcfg.type != KCFG_INT && ext->kcfg.type != KCFG_CHAR) {
             pr_warn("extern (kcfg) '%s': value '%s' implies integer type\n", ext->name, value);
             return -EINVAL;
         }
         err = set_kcfg_value_num(ext, ext_val, num);
         break;
     }
     if (err)
         return err;
     pr_debug("extern (kcfg) '%s': set to %s\n", ext->name, value);
     return 0;
 }
 
 static int bpf_object__read_kconfig_file(struct bpf_object *obj, void *data)
 {
     char buf[PATH_MAX];
     struct utsname uts;
     int len, err = 0;
     gzFile file;
 
     uname(&uts);
     len = snprintf(buf, PATH_MAX, "/boot/config-%s", uts.release);
     if (len < 0)
         return -EINVAL;
     else if (len >= PATH_MAX)
         return -ENAMETOOLONG;
 
     /* gzopen also accepts uncompressed files. */
     file = gzopen(buf, "r");
     if (!file)
         file = gzopen("/proc/config.gz", "r");
 
     if (!file) {
         pr_warn("failed to open system Kconfig\n");
         return -ENOENT;
     }
 
     while (gzgets(file, buf, sizeof(buf))) {
         err = bpf_object__process_kconfig_line(obj, buf, data);
         if (err) {
             pr_warn("error parsing system Kconfig line '%s': %d\n",
                 buf, err);
             goto out;
         }
     }
 
 out:
     gzclose(file);
     return err;
 }
 
 static int bpf_object__read_kconfig_mem(struct bpf_object *obj,
                     const char *config, void *data)
 {
     char buf[PATH_MAX];
     int err = 0;
     FILE *file;
 
     file = fmemopen((void *)config, strlen(config), "r");
     if (!file) {
         err = -errno;
         pr_warn("failed to open in-memory Kconfig: %d\n", err);
         return err;
     }
 
     while (fgets(buf, sizeof(buf), file)) {
         err = bpf_object__process_kconfig_line(obj, buf, data);
         if (err) {
             pr_warn("error parsing in-memory Kconfig line '%s': %d\n",
                 buf, err);
             break;
         }
     }
 
     fclose(file);
     return err;
 }
 
 static int bpf_object__init_kconfig_map(struct bpf_object *obj)
 {
     struct extern_desc *last_ext = NULL, *ext;
     size_t map_sz;
     int i, err;
 
     for (i = 0; i < obj->nr_extern; i++) {
         ext = &obj->externs[i];
         if (ext->type == EXT_KCFG)
             last_ext = ext;
     }
 
     if (!last_ext)
         return 0;
 
     map_sz = last_ext->kcfg.data_off + last_ext->kcfg.sz;
     err = bpf_object__init_internal_map(obj, LIBBPF_MAP_KCONFIG,
                         ".kconfig", obj->efile.symbols_shndx,
                         NULL, map_sz);
     if (err)
         return err;
 
     obj->kconfig_map_idx = obj->nr_maps - 1;
 
     return 0;
 }
 
 const struct btf_type *
 skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
 {
     const struct btf_type *t = btf__type_by_id(btf, id);
 
     if (res_id)
         *res_id = id;
 
     while (btf_is_mod(t) || btf_is_typedef(t)) {
         if (res_id)
             *res_id = t->type;
         t = btf__type_by_id(btf, t->type);
     }
 
     return t;
 }
 
 static const struct btf_type *
 resolve_func_ptr(const struct btf *btf, __u32 id, __u32 *res_id)
 {
     const struct btf_type *t;
 
     t = skip_mods_and_typedefs(btf, id, NULL);
     if (!btf_is_ptr(t))
         return NULL;
 
     t = skip_mods_and_typedefs(btf, t->type, res_id);
 
     return btf_is_func_proto(t) ? t : NULL;
 }
 
 static const char *__btf_kind_str(__u16 kind)
 {
     switch (kind) {
     case BTF_KIND_UNKN: return "void";
     case BTF_KIND_INT: return "int";
     case BTF_KIND_PTR: return "ptr";
     case BTF_KIND_ARRAY: return "array";
     case BTF_KIND_STRUCT: return "struct";
     case BTF_KIND_UNION: return "union";
     case BTF_KIND_ENUM: return "enum";
     case BTF_KIND_FWD: return "fwd";
     case BTF_KIND_TYPEDEF: return "typedef";
     case BTF_KIND_VOLATILE: return "volatile";
     case BTF_KIND_CONST: return "const";
     case BTF_KIND_RESTRICT: return "restrict";
     case BTF_KIND_FUNC: return "func";
     case BTF_KIND_FUNC_PROTO: return "func_proto";
     case BTF_KIND_VAR: return "var";
     case BTF_KIND_DATASEC: return "datasec";
     case BTF_KIND_FLOAT: return "float";
     case BTF_KIND_DECL_TAG: return "decl_tag";
     case BTF_KIND_TYPE_TAG: return "type_tag";
     case BTF_KIND_ENUM64: return "enum64";
     default: return "unknown";
     }
 }
 
 const char *btf_kind_str(const struct btf_type *t)
 {
     return __btf_kind_str(btf_kind(t));
 }
 
 /*
  * Fetch integer attribute of BTF map definition. Such attributes are
  * represented using a pointer to an array, in which dimensionality of array
  * encodes specified integer value. E.g., int (*type)[BPF_MAP_TYPE_ARRAY];
  * encodes `type => BPF_MAP_TYPE_ARRAY` key/value pair completely using BTF
  * type definition, while using only sizeof(void *) space in ELF data section.
  */
 static bool get_map_field_int(const char *map_name, const struct btf *btf,
                   const struct btf_member *m, __u32 *res)
 {
     const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
     const char *name = btf__name_by_offset(btf, m->name_off);
     const struct btf_array *arr_info;
     const struct btf_type *arr_t;
 
     if (!btf_is_ptr(t)) {
         pr_warn("map '%s': attr '%s': expected PTR, got %s.\n",
             map_name, name, btf_kind_str(t));
         return false;
     }
 
     arr_t = btf__type_by_id(btf, t->type);
     if (!arr_t) {
         pr_warn("map '%s': attr '%s': type [%u] not found.\n",
             map_name, name, t->type);
         return false;
     }
     if (!btf_is_array(arr_t)) {
         pr_warn("map '%s': attr '%s': expected ARRAY, got %s.\n",
             map_name, name, btf_kind_str(arr_t));
         return false;
     }
     arr_info = btf_array(arr_t);
     *res = arr_info->nelems;
     return true;
 }
 
 static int build_map_pin_path(struct bpf_map *map, const char *path)
 {
     char buf[PATH_MAX];
     int len;
 
     if (!path)
         path = "/sys/fs/bpf";
 
     len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
     if (len < 0)
         return -EINVAL;
     else if (len >= PATH_MAX)
         return -ENAMETOOLONG;
 
     return bpf_map__set_pin_path(map, buf);
 }
 
 /* should match definition in bpf_helpers.h */
 enum libbpf_pin_type {
     LIBBPF_PIN_NONE,
     /* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
     LIBBPF_PIN_BY_NAME,
 };
 
 int parse_btf_map_def(const char *map_name, struct btf *btf,
               const struct btf_type *def_t, bool strict,
               struct btf_map_def *map_def, struct btf_map_def *inner_def)
 {
     const struct btf_type *t;
     const struct btf_member *m;
     bool is_inner = inner_def == NULL;
     int vlen, i;
 
     vlen = btf_vlen(def_t);
     m = btf_members(def_t);
     for (i = 0; i < vlen; i++, m++) {
         const char *name = btf__name_by_offset(btf, m->name_off);
 
         if (!name) {
             pr_warn("map '%s': invalid field #%d.\n", map_name, i);
             return -EINVAL;
         }
         if (strcmp(name, "type") == 0) {
             if (!get_map_field_int(map_name, btf, m, &map_def->map_type))
                 return -EINVAL;
             map_def->parts |= MAP_DEF_MAP_TYPE;
         } else if (strcmp(name, "max_entries") == 0) {
             if (!get_map_field_int(map_name, btf, m, &map_def->max_entries))
                 return -EINVAL;
             map_def->parts |= MAP_DEF_MAX_ENTRIES;
         } else if (strcmp(name, "map_flags") == 0) {
             if (!get_map_field_int(map_name, btf, m, &map_def->map_flags))
                 return -EINVAL;
             map_def->parts |= MAP_DEF_MAP_FLAGS;
         } else if (strcmp(name, "numa_node") == 0) {
             if (!get_map_field_int(map_name, btf, m, &map_def->numa_node))
                 return -EINVAL;
             map_def->parts |= MAP_DEF_NUMA_NODE;
         } else if (strcmp(name, "key_size") == 0) {
             __u32 sz;
 
             if (!get_map_field_int(map_name, btf, m, &sz))
                 return -EINVAL;
             if (map_def->key_size && map_def->key_size != sz) {
                 pr_warn("map '%s': conflicting key size %u != %u.\n",
                     map_name, map_def->key_size, sz);
                 return -EINVAL;
             }
             map_def->key_size = sz;
             map_def->parts |= MAP_DEF_KEY_SIZE;
         } else if (strcmp(name, "key") == 0) {
             __s64 sz;
 
             t = btf__type_by_id(btf, m->type);
             if (!t) {
                 pr_warn("map '%s': key type [%d] not found.\n",
                     map_name, m->type);
                 return -EINVAL;
             }
             if (!btf_is_ptr(t)) {
                 pr_warn("map '%s': key spec is not PTR: %s.\n",
                     map_name, btf_kind_str(t));
                 return -EINVAL;
             }
             sz = btf__resolve_size(btf, t->type);
             if (sz < 0) {
                 pr_warn("map '%s': can't determine key size for type [%u]: %zd.\n",
                     map_name, t->type, (ssize_t)sz);
                 return sz;
             }
             if (map_def->key_size && map_def->key_size != sz) {
                 pr_warn("map '%s': conflicting key size %u != %zd.\n",
                     map_name, map_def->key_size, (ssize_t)sz);
                 return -EINVAL;
             }
             map_def->key_size = sz;
             map_def->key_type_id = t->type;
             map_def->parts |= MAP_DEF_KEY_SIZE | MAP_DEF_KEY_TYPE;
         } else if (strcmp(name, "value_size") == 0) {
             __u32 sz;
 
             if (!get_map_field_int(map_name, btf, m, &sz))
                 return -EINVAL;
             if (map_def->value_size && map_def->value_size != sz) {
                 pr_warn("map '%s': conflicting value size %u != %u.\n",
                     map_name, map_def->value_size, sz);
                 return -EINVAL;
             }
             map_def->value_size = sz;
             map_def->parts |= MAP_DEF_VALUE_SIZE;
         } else if (strcmp(name, "value") == 0) {
             __s64 sz;
 
             t = btf__type_by_id(btf, m->type);
             if (!t) {
                 pr_warn("map '%s': value type [%d] not found.\n",
                     map_name, m->type);
                 return -EINVAL;
             }
             if (!btf_is_ptr(t)) {
                 pr_warn("map '%s': value spec is not PTR: %s.\n",
                     map_name, btf_kind_str(t));
                 return -EINVAL;
             }
             sz = btf__resolve_size(btf, t->type);
             if (sz < 0) {
                 pr_warn("map '%s': can't determine value size for type [%u]: %zd.\n",
                     map_name, t->type, (ssize_t)sz);
                 return sz;
             }
             if (map_def->value_size && map_def->value_size != sz) {
                 pr_warn("map '%s': conflicting value size %u != %zd.\n",
                     map_name, map_def->value_size, (ssize_t)sz);
                 return -EINVAL;
             }
             map_def->value_size = sz;
             map_def->value_type_id = t->type;
             map_def->parts |= MAP_DEF_VALUE_SIZE | MAP_DEF_VALUE_TYPE;
         }
         else if (strcmp(name, "values") == 0) {
             bool is_map_in_map = bpf_map_type__is_map_in_map(map_def->map_type);
             bool is_prog_array = map_def->map_type == BPF_MAP_TYPE_PROG_ARRAY;
             const char *desc = is_map_in_map ? "map-in-map inner" : "prog-array value";
             char inner_map_name[128];
             int err;
 
             if (is_inner) {
                 pr_warn("map '%s': multi-level inner maps not supported.\n",
                     map_name);
                 return -ENOTSUP;
             }
             if (i != vlen - 1) {
                 pr_warn("map '%s': '%s' member should be last.\n",
                     map_name, name);
                 return -EINVAL;
             }
             if (!is_map_in_map && !is_prog_array) {
                 pr_warn("map '%s': should be map-in-map or prog-array.\n",
                     map_name);
                 return -ENOTSUP;
             }
             if (map_def->value_size && map_def->value_size != 4) {
                 pr_warn("map '%s': conflicting value size %u != 4.\n",
                     map_name, map_def->value_size);
                 return -EINVAL;
             }
             map_def->value_size = 4;
             t = btf__type_by_id(btf, m->type);
             if (!t) {
                 pr_warn("map '%s': %s type [%d] not found.\n",
                     map_name, desc, m->type);
                 return -EINVAL;
             }
             if (!btf_is_array(t) || btf_array(t)->nelems) {
                 pr_warn("map '%s': %s spec is not a zero-sized array.\n",
                     map_name, desc);
                 return -EINVAL;
             }
             t = skip_mods_and_typedefs(btf, btf_array(t)->type, NULL);
             if (!btf_is_ptr(t)) {
                 pr_warn("map '%s': %s def is of unexpected kind %s.\n",
                     map_name, desc, btf_kind_str(t));
                 return -EINVAL;
             }
             t = skip_mods_and_typedefs(btf, t->type, NULL);
             if (is_prog_array) {
                 if (!btf_is_func_proto(t)) {
                     pr_warn("map '%s': prog-array value def is of unexpected kind %s.\n",
                         map_name, btf_kind_str(t));
                     return -EINVAL;
                 }
                 continue;
             }
             if (!btf_is_struct(t)) {
                 pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
                     map_name, btf_kind_str(t));
                 return -EINVAL;
             }
 
             snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", map_name);
             err = parse_btf_map_def(inner_map_name, btf, t, strict, inner_def, NULL);
             if (err)
                 return err;
 
             map_def->parts |= MAP_DEF_INNER_MAP;
         } else if (strcmp(name, "pinning") == 0) {
             __u32 val;
 
             if (is_inner) {
                 pr_warn("map '%s': inner def can't be pinned.\n", map_name);
                 return -EINVAL;
             }
             if (!get_map_field_int(map_name, btf, m, &val))
                 return -EINVAL;
             if (val != LIBBPF_PIN_NONE && val != LIBBPF_PIN_BY_NAME) {
                 pr_warn("map '%s': invalid pinning value %u.\n",
                     map_name, val);
                 return -EINVAL;
             }
             map_def->pinning = val;
             map_def->parts |= MAP_DEF_PINNING;
         } else if (strcmp(name, "map_extra") == 0) {
             __u32 map_extra;
 
             if (!get_map_field_int(map_name, btf, m, &map_extra))
                 return -EINVAL;
             map_def->map_extra = map_extra;
             map_def->parts |= MAP_DEF_MAP_EXTRA;
         } else {
             if (strict) {
                 pr_warn("map '%s': unknown field '%s'.\n", map_name, name);
                 return -ENOTSUP;
             }
             pr_debug("map '%s': ignoring unknown field '%s'.\n", map_name, name);
         }
     }
 
     if (map_def->map_type == BPF_MAP_TYPE_UNSPEC) {
         pr_warn("map '%s': map type isn't specified.\n", map_name);
         return -EINVAL;
     }
 
     return 0;
 }
 
 static size_t adjust_ringbuf_sz(size_t sz)
 {
     __u32 page_sz = sysconf(_SC_PAGE_SIZE);
     __u32 mul;
 
     /* if user forgot to set any size, make sure they see error */
     if (sz == 0)
         return 0;
     /* Kernel expects BPF_MAP_TYPE_RINGBUF's max_entries to be
      * a power-of-2 multiple of kernel's page size. If user diligently
      * satisified these conditions, pass the size through.
      */
     if ((sz % page_sz) == 0 && is_pow_of_2(sz / page_sz))
         return sz;
 
     /* Otherwise find closest (page_sz * power_of_2) product bigger than
      * user-set size to satisfy both user size request and kernel
      * requirements and substitute correct max_entries for map creation.
      */
     for (mul = 1; mul <= UINT_MAX / page_sz; mul <<= 1) {
         if (mul * page_sz > sz)
             return mul * page_sz;
     }
 
     /* if it's impossible to satisfy the conditions (i.e., user size is
      * very close to UINT_MAX but is not a power-of-2 multiple of
      * page_size) then just return original size and let kernel reject it
      */
     return sz;
 }
 
 static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
 {
     map->def.type = def->map_type;
     map->def.key_size = def->key_size;
     map->def.value_size = def->value_size;
     map->def.max_entries = def->max_entries;
     map->def.map_flags = def->map_flags;
     map->map_extra = def->map_extra;
 
     map->numa_node = def->numa_node;
     map->btf_key_type_id = def->key_type_id;
     map->btf_value_type_id = def->value_type_id;
 
     /* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
     if (map->def.type == BPF_MAP_TYPE_RINGBUF)
         map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
 
     if (def->parts & MAP_DEF_MAP_TYPE)
         pr_debug("map '%s': found type = %u.\n", map->name, def->map_type);
 
     if (def->parts & MAP_DEF_KEY_TYPE)
         pr_debug("map '%s': found key [%u], sz = %u.\n",
              map->name, def->key_type_id, def->key_size);
     else if (def->parts & MAP_DEF_KEY_SIZE)
         pr_debug("map '%s': found key_size = %u.\n", map->name, def->key_size);
 
     if (def->parts & MAP_DEF_VALUE_TYPE)
         pr_debug("map '%s': found value [%u], sz = %u.\n",
              map->name, def->value_type_id, def->value_size);
     else if (def->parts & MAP_DEF_VALUE_SIZE)
         pr_debug("map '%s': found value_size = %u.\n", map->name, def->value_size);
 
     if (def->parts & MAP_DEF_MAX_ENTRIES)
         pr_debug("map '%s': found max_entries = %u.\n", map->name, def->max_entries);
     if (def->parts & MAP_DEF_MAP_FLAGS)
         pr_debug("map '%s': found map_flags = 0x%x.\n", map->name, def->map_flags);
     if (def->parts & MAP_DEF_MAP_EXTRA)
         pr_debug("map '%s': found map_extra = 0x%llx.\n", map->name,
              (unsigned long long)def->map_extra);
     if (def->parts & MAP_DEF_PINNING)
         pr_debug("map '%s': found pinning = %u.\n", map->name, def->pinning);
     if (def->parts & MAP_DEF_NUMA_NODE)
         pr_debug("map '%s': found numa_node = %u.\n", map->name, def->numa_node);
 
     if (def->parts & MAP_DEF_INNER_MAP)
         pr_debug("map '%s': found inner map definition.\n", map->name);
 }
 
 static const char *btf_var_linkage_str(__u32 linkage)
 {
     switch (linkage) {
     case BTF_VAR_STATIC: return "static";
     case BTF_VAR_GLOBAL_ALLOCATED: return "global";
     case BTF_VAR_GLOBAL_EXTERN: return "extern";
     default: return "unknown";
     }
 }
 
 static int bpf_object__init_user_btf_map(struct bpf_object *obj,
                      const struct btf_type *sec,
                      int var_idx, int sec_idx,
                      const Elf_Data *data, bool strict,
                      const char *pin_root_path)
 {
     struct btf_map_def map_def = {}, inner_def = {};
     const struct btf_type *var, *def;
     const struct btf_var_secinfo *vi;
     const struct btf_var *var_extra;
     const char *map_name;
     struct bpf_map *map;
     int err;
 
     vi = btf_var_secinfos(sec) + var_idx;
     var = btf__type_by_id(obj->btf, vi->type);
     var_extra = btf_var(var);
     map_name = btf__name_by_offset(obj->btf, var->name_off);
 
     if (map_name == NULL || map_name[0] == '\0') {
         pr_warn("map #%d: empty name.\n", var_idx);
         return -EINVAL;
     }
     if ((__u64)vi->offset + vi->size > data->d_size) {
         pr_warn("map '%s' BTF data is corrupted.\n", map_name);
         return -EINVAL;
     }
     if (!btf_is_var(var)) {
         pr_warn("map '%s': unexpected var kind %s.\n",
             map_name, btf_kind_str(var));
         return -EINVAL;
     }
     if (var_extra->linkage != BTF_VAR_GLOBAL_ALLOCATED) {
         pr_warn("map '%s': unsupported map linkage %s.\n",
             map_name, btf_var_linkage_str(var_extra->linkage));
         return -EOPNOTSUPP;
     }
 
     def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
     if (!btf_is_struct(def)) {
         pr_warn("map '%s': unexpected def kind %s.\n",
             map_name, btf_kind_str(var));
         return -EINVAL;
     }
     if (def->size > vi->size) {
         pr_warn("map '%s': invalid def size.\n", map_name);
         return -EINVAL;
     }
 
     map = bpf_object__add_map(obj);
     if (IS_ERR(map))
         return PTR_ERR(map);
     map->name = strdup(map_name);
     if (!map->name) {
         pr_warn("map '%s': failed to alloc map name.\n", map_name);
         return -ENOMEM;
     }
     map->libbpf_type = LIBBPF_MAP_UNSPEC;
     map->def.type = BPF_MAP_TYPE_UNSPEC;
     map->sec_idx = sec_idx;
     map->sec_offset = vi->offset;
     map->btf_var_idx = var_idx;
     pr_debug("map '%s': at sec_idx %d, offset %zu.\n",
          map_name, map->sec_idx, map->sec_offset);
 
     err = parse_btf_map_def(map->name, obj->btf, def, strict, &map_def, &inner_def);
     if (err)
         return err;
 
     fill_map_from_def(map, &map_def);
 
     if (map_def.pinning == LIBBPF_PIN_BY_NAME) {
         err = build_map_pin_path(map, pin_root_path);
         if (err) {
             pr_warn("map '%s': couldn't build pin path.\n", map->name);
             return err;
         }
     }
 
     if (map_def.parts & MAP_DEF_INNER_MAP) {
         map->inner_map = calloc(1, sizeof(*map->inner_map));
         if (!map->inner_map)
             return -ENOMEM;
         map->inner_map->fd = -1;
         map->inner_map->sec_idx = sec_idx;
         map->inner_map->name = malloc(strlen(map_name) + sizeof(".inner") + 1);
         if (!map->inner_map->name)
             return -ENOMEM;
         sprintf(map->inner_map->name, "%s.inner", map_name);
 
         fill_map_from_def(map->inner_map, &inner_def);
     }
 
     err = bpf_map_find_btf_info(obj, map);
     if (err)
         return err;
 
     return 0;
 }
 
 static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
                       const char *pin_root_path)
 {
     const struct btf_type *sec = NULL;
     int nr_types, i, vlen, err;
     const struct btf_type *t;
     const char *name;
     Elf_Data *data;
     Elf_Scn *scn;
 
     if (obj->efile.btf_maps_shndx < 0)
         return 0;
 
     scn = elf_sec_by_idx(obj, obj->efile.btf_maps_shndx);
     data = elf_sec_data(obj, scn);
     if (!scn || !data) {
         pr_warn("elf: failed to get %s map definitions for %s\n",
             MAPS_ELF_SEC, obj->path);
         return -EINVAL;
     }
 
     nr_types = btf__type_cnt(obj->btf);
     for (i = 1; i < nr_types; i++) {
         t = btf__type_by_id(obj->btf, i);
         if (!btf_is_datasec(t))
             continue;
         name = btf__name_by_offset(obj->btf, t->name_off);
         if (strcmp(name, MAPS_ELF_SEC) == 0) {
             sec = t;
             obj->efile.btf_maps_sec_btf_id = i;
             break;
         }
     }
 
     if (!sec) {
         pr_warn("DATASEC '%s' not found.\n", MAPS_ELF_SEC);
         return -ENOENT;
     }
 
     vlen = btf_vlen(sec);
     for (i = 0; i < vlen; i++) {
         err = bpf_object__init_user_btf_map(obj, sec, i,
                             obj->efile.btf_maps_shndx,
                             data, strict,
                             pin_root_path);
         if (err)
             return err;
     }
 
     return 0;
 }
 
 static int bpf_object__init_maps(struct bpf_object *obj,
                  const struct bpf_object_open_opts *opts)
 {
     const char *pin_root_path;
     bool strict;
     int err = 0;
 
     strict = !OPTS_GET(opts, relaxed_maps, false);
     pin_root_path = OPTS_GET(opts, pin_root_path, NULL);
 
     err = err ?: bpf_object__init_user_btf_maps(obj, strict, pin_root_path);
     err = err ?: bpf_object__init_global_data_maps(obj);
     err = err ?: bpf_object__init_kconfig_map(obj);
     err = err ?: bpf_object__init_struct_ops_maps(obj);
 
     return err;
 }
 
 static bool section_have_execinstr(struct bpf_object *obj, int idx)
 {
     Elf64_Shdr *sh;
 
     sh = elf_sec_hdr(obj, elf_sec_by_idx(obj, idx));
     if (!sh)
         return false;
 
     return sh->sh_flags & SHF_EXECINSTR;
 }
 
 static bool btf_needs_sanitization(struct bpf_object *obj)
 {
     bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
     bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
     bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
     bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
     bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
     bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
     bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
 
     return !has_func || !has_datasec || !has_func_global || !has_float ||
            !has_decl_tag || !has_type_tag || !has_enum64;
 }
 
 static int bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 {
     bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
     bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
     bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
     bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
     bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
     bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
     bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
     int enum64_placeholder_id = 0;
     struct btf_type *t;
     int i, j, vlen;
 
     for (i = 1; i < btf__type_cnt(btf); i++) {
         t = (struct btf_type *)btf__type_by_id(btf, i);
 
         if ((!has_datasec && btf_is_var(t)) || (!has_decl_tag && btf_is_decl_tag(t))) {
             /* replace VAR/DECL_TAG with INT */
             t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
             /*
              * using size = 1 is the safest choice, 4 will be too
              * big and cause kernel BTF validation failure if
              * original variable took less than 4 bytes
              */
             t->size = 1;
             *(int *)(t + 1) = BTF_INT_ENC(0, 0, 8);
         } else if (!has_datasec && btf_is_datasec(t)) {
             /* replace DATASEC with STRUCT */
             const struct btf_var_secinfo *v = btf_var_secinfos(t);
             struct btf_member *m = btf_members(t);
             struct btf_type *vt;
             char *name;
 
             name = (char *)btf__name_by_offset(btf, t->name_off);
             while (*name) {
                 if (*name == '.')
                     *name = '_';
                 name++;
             }
 
             vlen = btf_vlen(t);
             t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, vlen);
             for (j = 0; j < vlen; j++, v++, m++) {
                 /* order of field assignments is important */
                 m->offset = v->offset * 8;
                 m->type = v->type;
                 /* preserve variable name as member name */
                 vt = (void *)btf__type_by_id(btf, v->type);
                 m->name_off = vt->name_off;
             }
         } else if (!has_func && btf_is_func_proto(t)) {
             /* replace FUNC_PROTO with ENUM */
             vlen = btf_vlen(t);
             t->info = BTF_INFO_ENC(BTF_KIND_ENUM, 0, vlen);
             t->size = sizeof(__u32); /* kernel enforced */
         } else if (!has_func && btf_is_func(t)) {
             /* replace FUNC with TYPEDEF */
             t->info = BTF_INFO_ENC(BTF_KIND_TYPEDEF, 0, 0);
         } else if (!has_func_global && btf_is_func(t)) {
             /* replace BTF_FUNC_GLOBAL with BTF_FUNC_STATIC */
             t->info = BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0);
         } else if (!has_float && btf_is_float(t)) {
             /* replace FLOAT with an equally-sized empty STRUCT;
              * since C compilers do not accept e.g. "float" as a
              * valid struct name, make it anonymous
              */
             t->name_off = 0;
             t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 0);
         } else if (!has_type_tag && btf_is_type_tag(t)) {
             /* replace TYPE_TAG with a CONST */
             t->name_off = 0;
             t->info = BTF_INFO_ENC(BTF_KIND_CONST, 0, 0);
         } else if (!has_enum64 && btf_is_enum(t)) {
             /* clear the kflag */
             t->info = btf_type_info(btf_kind(t), btf_vlen(t), false);
         } else if (!has_enum64 && btf_is_enum64(t)) {
             /* replace ENUM64 with a union */
             struct btf_member *m;
 
             if (enum64_placeholder_id == 0) {
                 enum64_placeholder_id = btf__add_int(btf, "enum64_placeholder", 1, 0);
                 if (enum64_placeholder_id < 0)
                     return enum64_placeholder_id;
 
                 t = (struct btf_type *)btf__type_by_id(btf, i);
             }
 
             m = btf_members(t);
             vlen = btf_vlen(t);
             t->info = BTF_INFO_ENC(BTF_KIND_UNION, 0, vlen);
             for (j = 0; j < vlen; j++, m++) {
                 m->type = enum64_placeholder_id;
                 m->offset = 0;
             }
                 }
     }
 
     return 0;
 }
 
 static bool libbpf_needs_btf(const struct bpf_object *obj)
 {
     return obj->efile.btf_maps_shndx >= 0 ||
            obj->efile.st_ops_shndx >= 0 ||
            obj->nr_extern > 0;
 }
 
 static bool kernel_needs_btf(const struct bpf_object *obj)
 {
     return obj->efile.st_ops_shndx >= 0;
 }
 
 static int bpf_object__init_btf(struct bpf_object *obj,
                 Elf_Data *btf_data,
                 Elf_Data *btf_ext_data)
 {
     int err = -ENOENT;
 
     if (btf_data) {
         obj->btf = btf__new(btf_data->d_buf, btf_data->d_size);
         err = libbpf_get_error(obj->btf);
         if (err) {
             obj->btf = NULL;
             pr_warn("Error loading ELF section %s: %d.\n", BTF_ELF_SEC, err);
             goto out;
         }
         /* enforce 8-byte pointers for BPF-targeted BTFs */
         btf__set_pointer_size(obj->btf, 8);
     }
     if (btf_ext_data) {
         struct btf_ext_info *ext_segs[3];
         int seg_num, sec_num;
 
         if (!obj->btf) {
             pr_debug("Ignore ELF section %s because its depending ELF section %s is not found.\n",
                  BTF_EXT_ELF_SEC, BTF_ELF_SEC);
             goto out;
         }
         obj->btf_ext = btf_ext__new(btf_ext_data->d_buf, btf_ext_data->d_size);
         err = libbpf_get_error(obj->btf_ext);
         if (err) {
             pr_warn("Error loading ELF section %s: %d. Ignored and continue.\n",
                 BTF_EXT_ELF_SEC, err);
             obj->btf_ext = NULL;
             goto out;
         }
 
         /* setup .BTF.ext to ELF section mapping */
         ext_segs[0] = &obj->btf_ext->func_info;
         ext_segs[1] = &obj->btf_ext->line_info;
         ext_segs[2] = &obj->btf_ext->core_relo_info;
         for (seg_num = 0; seg_num < ARRAY_SIZE(ext_segs); seg_num++) {
             struct btf_ext_info *seg = ext_segs[seg_num];
             const struct btf_ext_info_sec *sec;
             const char *sec_name;
             Elf_Scn *scn;
 
             if (seg->sec_cnt == 0)
                 continue;
 
             seg->sec_idxs = calloc(seg->sec_cnt, sizeof(*seg->sec_idxs));
             if (!seg->sec_idxs) {
                 err = -ENOMEM;
                 goto out;
             }
 
             sec_num = 0;
             for_each_btf_ext_sec(seg, sec) {
                 /* preventively increment index to avoid doing
                  * this before every continue below
                  */
                 sec_num++;
 
                 sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
                 if (str_is_empty(sec_name))
                     continue;
                 scn = elf_sec_by_name(obj, sec_name);
                 if (!scn)
                     continue;
 
                 seg->sec_idxs[sec_num - 1] = elf_ndxscn(scn);
             }
         }
     }
 out:
     if (err && libbpf_needs_btf(obj)) {
         pr_warn("BTF is required, but is missing or corrupted.\n");
         return err;
     }
     return 0;
 }
 
 static int compare_vsi_off(const void *_a, const void *_b)
 {
     const struct btf_var_secinfo *a = _a;
     const struct btf_var_secinfo *b = _b;
 
     return a->offset - b->offset;
 }
 
 static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
                  struct btf_type *t)
 {
     __u32 size = 0, off = 0, i, vars = btf_vlen(t);
     const char *name = btf__name_by_offset(btf, t->name_off);
     const struct btf_type *t_var;
     struct btf_var_secinfo *vsi;
     const struct btf_var *var;
     int ret;
 
     if (!name) {
         pr_debug("No name found in string section for DATASEC kind.\n");
         return -ENOENT;
     }
 
     /* .extern datasec size and var offsets were set correctly during
      * extern collection step, so just skip straight to sorting variables
      */
     if (t->size)
         goto sort_vars;
 
     ret = find_elf_sec_sz(obj, name, &size);
     if (ret || !size) {
         pr_debug("Invalid size for section %s: %u bytes\n", name, size);
         return -ENOENT;
     }
 
     t->size = size;
 
     for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
         t_var = btf__type_by_id(btf, vsi->type);
         if (!t_var || !btf_is_var(t_var)) {
             pr_debug("Non-VAR type seen in section %s\n", name);
             return -EINVAL;
         }
 
         var = btf_var(t_var);
         if (var->linkage == BTF_VAR_STATIC)
             continue;
 
         name = btf__name_by_offset(btf, t_var->name_off);
         if (!name) {
             pr_debug("No name found in string section for VAR kind\n");
             return -ENOENT;
         }
 
         ret = find_elf_var_offset(obj, name, &off);
         if (ret) {
             pr_debug("No offset found in symbol table for VAR %s\n",
                  name);
             return -ENOENT;
         }
 
         vsi->offset = off;
     }
 
 sort_vars:
     qsort(btf_var_secinfos(t), vars, sizeof(*vsi), compare_vsi_off);
     return 0;
 }
 
 static int btf_finalize_data(struct bpf_object *obj, struct btf *btf)
 {
     int err = 0;
     __u32 i, n = btf__type_cnt(btf);
 
     for (i = 1; i < n; i++) {
         struct btf_type *t = btf_type_by_id(btf, i);
 
         /* Loader needs to fix up some of the things compiler
          * couldn't get its hands on while emitting BTF. This
          * is section size and global variable offset. We use
          * the info from the ELF itself for this purpose.
          */
         if (btf_is_datasec(t)) {
             err = btf_fixup_datasec(obj, btf, t);
             if (err)
                 break;
         }
     }
 
     return libbpf_err(err);
 }
 
 static int bpf_object__finalize_btf(struct bpf_object *obj)
 {
     int err;
 
     if (!obj->btf)
         return 0;
 
     err = btf_finalize_data(obj, obj->btf);
     if (err) {
         pr_warn("Error finalizing %s: %d.\n", BTF_ELF_SEC, err);
         return err;
     }
 
     return 0;
 }
 
 static bool prog_needs_vmlinux_btf(struct bpf_program *prog)
 {
     if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
         prog->type == BPF_PROG_TYPE_LSM)
         return true;
 
     /* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
      * also need vmlinux BTF
      */
     if (prog->type == BPF_PROG_TYPE_TRACING && !prog->attach_prog_fd)
         return true;
 
     return false;
 }
 
 static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
 {
     struct bpf_program *prog;
     int i;
 
     /* CO-RE relocations need kernel BTF, only when btf_custom_path
      * is not specified
      */
     if (obj->btf_ext && obj->btf_ext->core_relo_info.len && !obj->btf_custom_path)
         return true;
 
     /* Support for typed ksyms needs kernel BTF */
     for (i = 0; i < obj->nr_extern; i++) {
         const struct extern_desc *ext;
 
         ext = &obj->externs[i];
         if (ext->type == EXT_KSYM && ext->ksym.type_id)
             return true;
     }
 
     bpf_object__for_each_program(prog, obj) {
         if (!prog->autoload)
             continue;
         if (prog_needs_vmlinux_btf(prog))
             return true;
     }
 
     return false;
 }
 
 static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
 {
     int err;
 
     /* btf_vmlinux could be loaded earlier */
     if (obj->btf_vmlinux || obj->gen_loader)
         return 0;
 
     if (!force && !obj_needs_vmlinux_btf(obj))
         return 0;
 
     obj->btf_vmlinux = btf__load_vmlinux_btf();
     err = libbpf_get_error(obj->btf_vmlinux);
     if (err) {
         pr_warn("Error loading vmlinux BTF: %d\n", err);
         obj->btf_vmlinux = NULL;
         return err;
     }
     return 0;
 }
 
 static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 {
     struct btf *kern_btf = obj->btf;
     bool btf_mandatory, sanitize;
     int i, err = 0;
 
     if (!obj->btf)
         return 0;
 
     if (!kernel_supports(obj, FEAT_BTF)) {
         if (kernel_needs_btf(obj)) {
             err = -EOPNOTSUPP;
             goto report;
         }
         pr_debug("Kernel doesn't support BTF, skipping uploading it.\n");
         return 0;
     }
 
     /* Even though some subprogs are global/weak, user might prefer more
      * permissive BPF verification process that BPF verifier performs for
      * static functions, taking into account more context from the caller
      * functions. In such case, they need to mark such subprogs with
      * __attribute__((visibility("hidden"))) and libbpf will adjust
      * corresponding FUNC BTF type to be marked as static and trigger more
      * involved BPF verification process.
      */
     for (i = 0; i < obj->nr_programs; i++) {
         struct bpf_program *prog = &obj->programs[i];
         struct btf_type *t;
         const char *name;
         int j, n;
 
         if (!prog->mark_btf_static || !prog_is_subprog(obj, prog))
             continue;
 
         n = btf__type_cnt(obj->btf);
         for (j = 1; j < n; j++) {
             t = btf_type_by_id(obj->btf, j);
             if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL)
                 continue;
 
             name = btf__str_by_offset(obj->btf, t->name_off);
             if (strcmp(name, prog->name) != 0)
                 continue;
 
             t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0);
             break;
         }
     }
 
     sanitize = btf_needs_sanitization(obj);
     if (sanitize) {
         const void *raw_data;
         __u32 sz;
 
         /* clone BTF to sanitize a copy and leave the original intact */
         raw_data = btf__raw_data(obj->btf, &sz);
         kern_btf = btf__new(raw_data, sz);
         err = libbpf_get_error(kern_btf);
         if (err)
             return err;
 
         /* enforce 8-byte pointers for BPF-targeted BTFs */
         btf__set_pointer_size(obj->btf, 8);
         err = bpf_object__sanitize_btf(obj, kern_btf);
         if (err)
             return err;
     }
 
     if (obj->gen_loader) {
         __u32 raw_size = 0;
         const void *raw_data = btf__raw_data(kern_btf, &raw_size);
 
         if (!raw_data)
             return -ENOMEM;
         bpf_gen__load_btf(obj->gen_loader, raw_data, raw_size);
         /* Pretend to have valid FD to pass various fd >= 0 checks.
          * This fd == 0 will not be used with any syscall and will be reset to -1 eventually.
          */
         btf__set_fd(kern_btf, 0);
     } else {
         /* currently BPF_BTF_LOAD only supports log_level 1 */
         err = btf_load_into_kernel(kern_btf, obj->log_buf, obj->log_size,
                        obj->log_level ? 1 : 0);
     }
     if (sanitize) {
         if (!err) {
             /* move fd to libbpf's BTF */
             btf__set_fd(obj->btf, btf__fd(kern_btf));
             btf__set_fd(kern_btf, -1);
         }
         btf__free(kern_btf);
     }
 report:
     if (err) {
         btf_mandatory = kernel_needs_btf(obj);
         pr_warn("Error loading .BTF into kernel: %d. %s\n", err,
             btf_mandatory ? "BTF is mandatory, can't proceed."
                       : "BTF is optional, ignoring.");
         if (!btf_mandatory)
             err = 0;
     }
     return err;
 }
 
 static const char *elf_sym_str(const struct bpf_object *obj, size_t off)
 {
     const char *name;
 
     name = elf_strptr(obj->efile.elf, obj->efile.strtabidx, off);
     if (!name) {
         pr_warn("elf: failed to get section name string at offset %zu from %s: %s\n",
             off, obj->path, elf_errmsg(-1));
         return NULL;
     }
 
     return name;
 }
 
 static const char *elf_sec_str(const struct bpf_object *obj, size_t off)
 {
     const char *name;
 
     name = elf_strptr(obj->efile.elf, obj->efile.shstrndx, off);
     if (!name) {
         pr_warn("elf: failed to get section name string at offset %zu from %s: %s\n",
             off, obj->path, elf_errmsg(-1));
         return NULL;
     }
 
     return name;
 }
 
 static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx)
 {
     Elf_Scn *scn;
 
     scn = elf_getscn(obj->efile.elf, idx);
     if (!scn) {
         pr_warn("elf: failed to get section(%zu) from %s: %s\n",
             idx, obj->path, elf_errmsg(-1));
         return NULL;
     }
     return scn;
 }
 
 static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name)
 {
     Elf_Scn *scn = NULL;
     Elf *elf = obj->efile.elf;
     const char *sec_name;
 
     while ((scn = elf_nextscn(elf, scn)) != NULL) {
         sec_name = elf_sec_name(obj, scn);
         if (!sec_name)
             return NULL;
 
         if (strcmp(sec_name, name) != 0)
             continue;
 
         return scn;
     }
     return NULL;
 }
 
 static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn)
 {
     Elf64_Shdr *shdr;
 
     if (!scn)
         return NULL;
 
     shdr = elf64_getshdr(scn);
     if (!shdr) {
         pr_warn("elf: failed to get section(%zu) header from %s: %s\n",
             elf_ndxscn(scn), obj->path, elf_errmsg(-1));
         return NULL;
     }
 
     return shdr;
 }
 
 static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn)
 {
     const char *name;
     Elf64_Shdr *sh;
 
     if (!scn)
         return NULL;
 
     sh = elf_sec_hdr(obj, scn);
     if (!sh)
         return NULL;
 
     name = elf_sec_str(obj, sh->sh_name);
     if (!name) {
         pr_warn("elf: failed to get section(%zu) name from %s: %s\n",
             elf_ndxscn(scn), obj->path, elf_errmsg(-1));
         return NULL;
     }
 
     return name;
 }
 
 static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn)
 {
     Elf_Data *data;
 
     if (!scn)
         return NULL;
 
     data = elf_getdata(scn, 0);
     if (!data) {
         pr_warn("elf: failed to get section(%zu) %s data from %s: %s\n",
             elf_ndxscn(scn), elf_sec_name(obj, scn) ?: "<?>",
             obj->path, elf_errmsg(-1));
         return NULL;
     }
 
     return data;
 }
 
 static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx)
 {
     if (idx >= obj->efile.symbols->d_size / sizeof(Elf64_Sym))
         return NULL;
 
     return (Elf64_Sym *)obj->efile.symbols->d_buf + idx;
 }
 
 static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx)
 {
     if (idx >= data->d_size / sizeof(Elf64_Rel))
         return NULL;
 
     return (Elf64_Rel *)data->d_buf + idx;
 }
 
 static bool is_sec_name_dwarf(const char *name)
 {
     /* approximation, but the actual list is too long */
     return str_has_pfx(name, ".debug_");
 }
 
 static bool ignore_elf_section(Elf64_Shdr *hdr, const char *name)
 {
     /* no special handling of .strtab */
     if (hdr->sh_type == SHT_STRTAB)
         return true;
 
     /* ignore .llvm_addrsig section as well */
     if (hdr->sh_type == SHT_LLVM_ADDRSIG)
         return true;
 
     /* no subprograms will lead to an empty .text section, ignore it */
     if (hdr->sh_type == SHT_PROGBITS && hdr->sh_size == 0 &&
         strcmp(name, ".text") == 0)
         return true;
 
     /* DWARF sections */
     if (is_sec_name_dwarf(name))
         return true;
 
     if (str_has_pfx(name, ".rel")) {
         name += sizeof(".rel") - 1;
         /* DWARF section relocations */
         if (is_sec_name_dwarf(name))
             return true;
 
         /* .BTF and .BTF.ext don't need relocations */
         if (strcmp(name, BTF_ELF_SEC) == 0 ||
             strcmp(name, BTF_EXT_ELF_SEC) == 0)
             return true;
     }
 
     return false;
 }
 
 static int cmp_progs(const void *_a, const void *_b)
 {
     const struct bpf_program *a = _a;
     const struct bpf_program *b = _b;
 
     if (a->sec_idx != b->sec_idx)
         return a->sec_idx < b->sec_idx ? -1 : 1;
 
     /* sec_insn_off can't be the same within the section */
     return a->sec_insn_off < b->sec_insn_off ? -1 : 1;
 }
 
 static int bpf_object__elf_collect(struct bpf_object *obj)
 {
     struct elf_sec_desc *sec_desc;
     Elf *elf = obj->efile.elf;
     Elf_Data *btf_ext_data = NULL;
     Elf_Data *btf_data = NULL;
     int idx = 0, err = 0;
     const char *name;
     Elf_Data *data;
     Elf_Scn *scn;
     Elf64_Shdr *sh;
 
     /* ELF section indices are 0-based, but sec #0 is special "invalid"
      * section. e_shnum does include sec #0, so e_shnum is the necessary
      * size of an array to keep all the sections.
      */
     obj->efile.sec_cnt = obj->efile.ehdr->e_shnum;
     obj->efile.secs = calloc(obj->efile.sec_cnt, sizeof(*obj->efile.secs));
     if (!obj->efile.secs)
         return -ENOMEM;
 
     /* a bunch of ELF parsing functionality depends on processing symbols,
      * so do the first pass and find the symbol table
      */
     scn = NULL;
     while ((scn = elf_nextscn(elf, scn)) != NULL) {
         sh = elf_sec_hdr(obj, scn);
         if (!sh)
             return -LIBBPF_ERRNO__FORMAT;
 
         if (sh->sh_type == SHT_SYMTAB) {
             if (obj->efile.symbols) {
                 pr_warn("elf: multiple symbol tables in %s\n", obj->path);
                 return -LIBBPF_ERRNO__FORMAT;
             }
 
             data = elf_sec_data(obj, scn);
             if (!data)
                 return -LIBBPF_ERRNO__FORMAT;
 
             idx = elf_ndxscn(scn);
 
             obj->efile.symbols = data;
             obj->efile.symbols_shndx = idx;
             obj->efile.strtabidx = sh->sh_link;
         }
     }
 
     if (!obj->efile.symbols) {
         pr_warn("elf: couldn't find symbol table in %s, stripped object file?\n",
             obj->path);
         return -ENOENT;
     }
 
     scn = NULL;
     while ((scn = elf_nextscn(elf, scn)) != NULL) {
         idx = elf_ndxscn(scn);
         sec_desc = &obj->efile.secs[idx];
 
         sh = elf_sec_hdr(obj, scn);
         if (!sh)
             return -LIBBPF_ERRNO__FORMAT;
 
         name = elf_sec_str(obj, sh->sh_name);
         if (!name)
             return -LIBBPF_ERRNO__FORMAT;
 
         if (ignore_elf_section(sh, name))
             continue;
 
         data = elf_sec_data(obj, scn);
         if (!data)
             return -LIBBPF_ERRNO__FORMAT;
 
         pr_debug("elf: section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
              idx, name, (unsigned long)data->d_size,
              (int)sh->sh_link, (unsigned long)sh->sh_flags,
              (int)sh->sh_type);
 
         if (strcmp(name, "license") == 0) {
             err = bpf_object__init_license(obj, data->d_buf, data->d_size);
             if (err)
                 return err;
         } else if (strcmp(name, "version") == 0) {
             err = bpf_object__init_kversion(obj, data->d_buf, data->d_size);
             if (err)
                 return err;
         } else if (strcmp(name, "maps") == 0) {
             obj->efile.maps_shndx = idx;
         } else if (strcmp(name, MAPS_ELF_SEC) == 0) {
             obj->efile.btf_maps_shndx = idx;
         } else if (strcmp(name, BTF_ELF_SEC) == 0) {
             if (sh->sh_type != SHT_PROGBITS)
                 return -LIBBPF_ERRNO__FORMAT;
             btf_data = data;
         } else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
             if (sh->sh_type != SHT_PROGBITS)
                 return -LIBBPF_ERRNO__FORMAT;
             btf_ext_data = data;
         } else if (sh->sh_type == SHT_SYMTAB) {
             /* already processed during the first pass above */
         } else if (sh->sh_type == SHT_PROGBITS && data->d_size > 0) {
             if (sh->sh_flags & SHF_EXECINSTR) {
                 if (strcmp(name, ".text") == 0)
                     obj->efile.text_shndx = idx;
                 err = bpf_object__add_programs(obj, data, name, idx);
                 if (err)
                     return err;
             } else if (strcmp(name, DATA_SEC) == 0 ||
                    str_has_pfx(name, DATA_SEC ".")) {
                 sec_desc->sec_type = SEC_DATA;
                 sec_desc->shdr = sh;
                 sec_desc->data = data;
             } else if (strcmp(name, RODATA_SEC) == 0 ||
                    str_has_pfx(name, RODATA_SEC ".")) {
                 sec_desc->sec_type = SEC_RODATA;
                 sec_desc->shdr = sh;
                 sec_desc->data = data;
             } else if (strcmp(name, STRUCT_OPS_SEC) == 0) {
                 obj->efile.st_ops_data = data;
                 obj->efile.st_ops_shndx = idx;
             } else {
                 pr_info("elf: skipping unrecognized data section(%d) %s\n",
                     idx, name);
             }
         } else if (sh->sh_type == SHT_REL) {
             int targ_sec_idx = sh->sh_info; /* points to other section */
 
             if (sh->sh_entsize != sizeof(Elf64_Rel) ||
                 targ_sec_idx >= obj->efile.sec_cnt)
                 return -LIBBPF_ERRNO__FORMAT;
 
             /* Only do relo for section with exec instructions */
             if (!section_have_execinstr(obj, targ_sec_idx) &&
                 strcmp(name, ".rel" STRUCT_OPS_SEC) &&
                 strcmp(name, ".rel" MAPS_ELF_SEC)) {
                 pr_info("elf: skipping relo section(%d) %s for section(%d) %s\n",
                     idx, name, targ_sec_idx,
                     elf_sec_name(obj, elf_sec_by_idx(obj, targ_sec_idx)) ?: "<?>");
                 continue;
             }
 
             sec_desc->sec_type = SEC_RELO;
             sec_desc->shdr = sh;
             sec_desc->data = data;
         } else if (sh->sh_type == SHT_NOBITS && strcmp(name, BSS_SEC) == 0) {
             sec_desc->sec_type = SEC_BSS;
             sec_desc->shdr = sh;
             sec_desc->data = data;
         } else {
             pr_info("elf: skipping section(%d) %s (size %zu)\n", idx, name,
                 (size_t)sh->sh_size);
         }
     }
 
     if (!obj->efile.strtabidx || obj->efile.strtabidx > idx) {
         pr_warn("elf: symbol strings section missing or invalid in %s\n", obj->path);
         return -LIBBPF_ERRNO__FORMAT;
     }
 
     /* sort BPF programs by section name and in-section instruction offset
      * for faster search */
     if (obj->nr_programs)
         qsort(obj->programs, obj->nr_programs, sizeof(*obj->programs), cmp_progs);
 
     return bpf_object__init_btf(obj, btf_data, btf_ext_data);
 }
 
 static bool sym_is_extern(const Elf64_Sym *sym)
 {
     int bind = ELF64_ST_BIND(sym->st_info);
     /* externs are symbols w/ type=NOTYPE, bind=GLOBAL|WEAK, section=UND */
     return sym->st_shndx == SHN_UNDEF &&
            (bind == STB_GLOBAL || bind == STB_WEAK) &&
            ELF64_ST_TYPE(sym->st_info) == STT_NOTYPE;
 }
 
 static bool sym_is_subprog(const Elf64_Sym *sym, int text_shndx)
 {
     int bind = ELF64_ST_BIND(sym->st_info);
     int type = ELF64_ST_TYPE(sym->st_info);
 
     /* in .text section */
     if (sym->st_shndx != text_shndx)
         return false;
 
     /* local function */
     if (bind == STB_LOCAL && type == STT_SECTION)
         return true;
 
     /* global function */
     return bind == STB_GLOBAL && type == STT_FUNC;
 }
 
 static int find_extern_btf_id(const struct btf *btf, const char *ext_name)
 {
     const struct btf_type *t;
     const char *tname;
     int i, n;
 
     if (!btf)
         return -ESRCH;
 
     n = btf__type_cnt(btf);
     for (i = 1; i < n; i++) {
         t = btf__type_by_id(btf, i);
 
         if (!btf_is_var(t) && !btf_is_func(t))
             continue;
 
         tname = btf__name_by_offset(btf, t->name_off);
         if (strcmp(tname, ext_name))
             continue;
 
         if (btf_is_var(t) &&
             btf_var(t)->linkage != BTF_VAR_GLOBAL_EXTERN)
             return -EINVAL;
 
         if (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_EXTERN)
             return -EINVAL;
 
         return i;
     }
 
     return -ENOENT;
 }
 
 static int find_extern_sec_btf_id(struct btf *btf, int ext_btf_id) {
     const struct btf_var_secinfo *vs;
     const struct btf_type *t;
     int i, j, n;
 
     if (!btf)
         return -ESRCH;
 
     n = btf__type_cnt(btf);
     for (i = 1; i < n; i++) {
         t = btf__type_by_id(btf, i);
 
         if (!btf_is_datasec(t))
             continue;
 
         vs = btf_var_secinfos(t);
         for (j = 0; j < btf_vlen(t); j++, vs++) {
             if (vs->type == ext_btf_id)
                 return i;
         }
     }
 
     return -ENOENT;
 }
 
 static enum kcfg_type find_kcfg_type(const struct btf *btf, int id,
                      bool *is_signed)
 {
     const struct btf_type *t;
     const char *name;
 
     t = skip_mods_and_typedefs(btf, id, NULL);
     name = btf__name_by_offset(btf, t->name_off);
 
     if (is_signed)
         *is_signed = false;
     switch (btf_kind(t)) {
     case BTF_KIND_INT: {
         int enc = btf_int_encoding(t);
 
         if (enc & BTF_INT_BOOL)
             return t->size == 1 ? KCFG_BOOL : KCFG_UNKNOWN;
         if (is_signed)
             *is_signed = enc & BTF_INT_SIGNED;
         if (t->size == 1)
             return KCFG_CHAR;
         if (t->size < 1 || t->size > 8 || (t->size & (t->size - 1)))
             return KCFG_UNKNOWN;
         return KCFG_INT;
     }
     case BTF_KIND_ENUM:
         if (t->size != 4)
             return KCFG_UNKNOWN;
         if (strcmp(name, "libbpf_tristate"))
             return KCFG_UNKNOWN;
         return KCFG_TRISTATE;
     case BTF_KIND_ENUM64:
         if (strcmp(name, "libbpf_tristate"))
             return KCFG_UNKNOWN;
         return KCFG_TRISTATE;
     case BTF_KIND_ARRAY:
         if (btf_array(t)->nelems == 0)
             return KCFG_UNKNOWN;
         if (find_kcfg_type(btf, btf_array(t)->type, NULL) != KCFG_CHAR)
             return KCFG_UNKNOWN;
         return KCFG_CHAR_ARR;
     default:
         return KCFG_UNKNOWN;
     }
 }
 
 static int cmp_externs(const void *_a, const void *_b)
 {
     const struct extern_desc *a = _a;
     const struct extern_desc *b = _b;
 
     if (a->type != b->type)
         return a->type < b->type ? -1 : 1;
 
     if (a->type == EXT_KCFG) {
         /* descending order by alignment requirements */
         if (a->kcfg.align != b->kcfg.align)
             return a->kcfg.align > b->kcfg.align ? -1 : 1;
         /* ascending order by size, within same alignment class */
         if (a->kcfg.sz != b->kcfg.sz)
             return a->kcfg.sz < b->kcfg.sz ? -1 : 1;
     }
 
     /* resolve ties by name */
     return strcmp(a->name, b->name);
 }
 
 static int find_int_btf_id(const struct btf *btf)
 {
     const struct btf_type *t;
     int i, n;
 
     n = btf__type_cnt(btf);
     for (i = 1; i < n; i++) {
         t = btf__type_by_id(btf, i);
 
         if (btf_is_int(t) && btf_int_bits(t) == 32)
             return i;
     }
 
     return 0;
 }
 
 static int add_dummy_ksym_var(struct btf *btf)
 {
     int i, int_btf_id, sec_btf_id, dummy_var_btf_id;
     const struct btf_var_secinfo *vs;
     const struct btf_type *sec;
 
     if (!btf)
         return 0;
 
     sec_btf_id = btf__find_by_name_kind(btf, KSYMS_SEC,
                         BTF_KIND_DATASEC);
     if (sec_btf_id < 0)
         return 0;
 
     sec = btf__type_by_id(btf, sec_btf_id);
     vs = btf_var_secinfos(sec);
     for (i = 0; i < btf_vlen(sec); i++, vs++) {
         const struct btf_type *vt;
 
         vt = btf__type_by_id(btf, vs->type);
         if (btf_is_func(vt))
             break;
     }
 
     /* No func in ksyms sec.  No need to add dummy var. */
     if (i == btf_vlen(sec))
         return 0;
 
     int_btf_id = find_int_btf_id(btf);
     dummy_var_btf_id = btf__add_var(btf,
                     "dummy_ksym",
                     BTF_VAR_GLOBAL_ALLOCATED,
                     int_btf_id);
     if (dummy_var_btf_id < 0)
         pr_warn("cannot create a dummy_ksym var\n");
 
     return dummy_var_btf_id;
 }
 
 static int bpf_object__collect_externs(struct bpf_object *obj)
 {
     struct btf_type *sec, *kcfg_sec = NULL, *ksym_sec = NULL;
     const struct btf_type *t;
     struct extern_desc *ext;
     int i, n, off, dummy_var_btf_id;
     const char *ext_name, *sec_name;
     Elf_Scn *scn;
     Elf64_Shdr *sh;
 
     if (!obj->efile.symbols)
         return 0;
 
     scn = elf_sec_by_idx(obj, obj->efile.symbols_shndx);
     sh = elf_sec_hdr(obj, scn);
     if (!sh || sh->sh_entsize != sizeof(Elf64_Sym))
         return -LIBBPF_ERRNO__FORMAT;
 
     dummy_var_btf_id = add_dummy_ksym_var(obj->btf);
     if (dummy_var_btf_id < 0)
         return dummy_var_btf_id;
 
     n = sh->sh_size / sh->sh_entsize;
     pr_debug("looking for externs among %d symbols...\n", n);
 
     for (i = 0; i < n; i++) {
         Elf64_Sym *sym = elf_sym_by_idx(obj, i);
 
         if (!sym)
             return -LIBBPF_ERRNO__FORMAT;
         if (!sym_is_extern(sym))
             continue;
         ext_name = elf_sym_str(obj, sym->st_name);
         if (!ext_name || !ext_name[0])
             continue;
 
         ext = obj->externs;
         ext = libbpf_reallocarray(ext, obj->nr_extern + 1, sizeof(*ext));
         if (!ext)
             return -ENOMEM;
         obj->externs = ext;
         ext = &ext[obj->nr_extern];
         memset(ext, 0, sizeof(*ext));
         obj->nr_extern++;
 
         ext->btf_id = find_extern_btf_id(obj->btf, ext_name);
         if (ext->btf_id <= 0) {
             pr_warn("failed to find BTF for extern '%s': %d\n",
                 ext_name, ext->btf_id);
             return ext->btf_id;
         }
         t = btf__type_by_id(obj->btf, ext->btf_id);
         ext->name = btf__name_by_offset(obj->btf, t->name_off);
         ext->sym_idx = i;
         ext->is_weak = ELF64_ST_BIND(sym->st_info) == STB_WEAK;
 
         ext->sec_btf_id = find_extern_sec_btf_id(obj->btf, ext->btf_id);
         if (ext->sec_btf_id <= 0) {
             pr_warn("failed to find BTF for extern '%s' [%d] section: %d\n",
                 ext_name, ext->btf_id, ext->sec_btf_id);
             return ext->sec_btf_id;
         }
         sec = (void *)btf__type_by_id(obj->btf, ext->sec_btf_id);
         sec_name = btf__name_by_offset(obj->btf, sec->name_off);
 
         if (strcmp(sec_name, KCONFIG_SEC) == 0) {
             if (btf_is_func(t)) {
                 pr_warn("extern function %s is unsupported under %s section\n",
                     ext->name, KCONFIG_SEC);
                 return -ENOTSUP;
             }
             kcfg_sec = sec;
             ext->type = EXT_KCFG;
             ext->kcfg.sz = btf__resolve_size(obj->btf, t->type);
             if (ext->kcfg.sz <= 0) {
                 pr_warn("failed to resolve size of extern (kcfg) '%s': %d\n",
                     ext_name, ext->kcfg.sz);
                 return ext->kcfg.sz;
             }
             ext->kcfg.align = btf__align_of(obj->btf, t->type);
             if (ext->kcfg.align <= 0) {
                 pr_warn("failed to determine alignment of extern (kcfg) '%s': %d\n",
                     ext_name, ext->kcfg.align);
                 return -EINVAL;
             }
             ext->kcfg.type = find_kcfg_type(obj->btf, t->type,
                                 &ext->kcfg.is_signed);
             if (ext->kcfg.type == KCFG_UNKNOWN) {
                 pr_warn("extern (kcfg) '%s': type is unsupported\n", ext_name);
                 return -ENOTSUP;
             }
         } else if (strcmp(sec_name, KSYMS_SEC) == 0) {
             ksym_sec = sec;
             ext->type = EXT_KSYM;
             skip_mods_and_typedefs(obj->btf, t->type,
                            &ext->ksym.type_id);
         } else {
             pr_warn("unrecognized extern section '%s'\n", sec_name);
             return -ENOTSUP;
         }
     }
     pr_debug("collected %d externs total\n", obj->nr_extern);
 
     if (!obj->nr_extern)
         return 0;
 
     /* sort externs by type, for kcfg ones also by (align, size, name) */
     qsort(obj->externs, obj->nr_extern, sizeof(*ext), cmp_externs);
 
     /* for .ksyms section, we need to turn all externs into allocated
      * variables in BTF to pass kernel verification; we do this by
      * pretending that each extern is a 8-byte variable
      */
     if (ksym_sec) {
         /* find existing 4-byte integer type in BTF to use for fake
          * extern variables in DATASEC
          */
         int int_btf_id = find_int_btf_id(obj->btf);
         /* For extern function, a dummy_var added earlier
          * will be used to replace the vs->type and
          * its name string will be used to refill
          * the missing param's name.
          */
         const struct btf_type *dummy_var;
 
         dummy_var = btf__type_by_id(obj->btf, dummy_var_btf_id);
         for (i = 0; i < obj->nr_extern; i++) {
             ext = &obj->externs[i];
             if (ext->type != EXT_KSYM)
                 continue;
             pr_debug("extern (ksym) #%d: symbol %d, name %s\n",
                  i, ext->sym_idx, ext->name);
         }
 
         sec = ksym_sec;
         n = btf_vlen(sec);
         for (i = 0, off = 0; i < n; i++, off += sizeof(int)) {
             struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i;
             struct btf_type *vt;
 
             vt = (void *)btf__type_by_id(obj->btf, vs->type);
             ext_name = btf__name_by_offset(obj->btf, vt->name_off);
             ext = find_extern_by_name(obj, ext_name);
             if (!ext) {
                 pr_warn("failed to find extern definition for BTF %s '%s'\n",
                     btf_kind_str(vt), ext_name);
                 return -ESRCH;
             }
             if (btf_is_func(vt)) {
                 const struct btf_type *func_proto;
                 struct btf_param *param;
                 int j;
 
                 func_proto = btf__type_by_id(obj->btf,
                                  vt->type);
                 param = btf_params(func_proto);
                 /* Reuse the dummy_var string if the
                  * func proto does not have param name.
                  */
                 for (j = 0; j < btf_vlen(func_proto); j++)
                     if (param[j].type && !param[j].name_off)
                         param[j].name_off =
                             dummy_var->name_off;
                 vs->type = dummy_var_btf_id;
                 vt->info &= ~0xffff;
                 vt->info |= BTF_FUNC_GLOBAL;
             } else {
                 btf_var(vt)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
                 vt->type = int_btf_id;
             }
             vs->offset = off;
             vs->size = sizeof(int);
         }
         sec->size = off;
     }
 
     if (kcfg_sec) {
         sec = kcfg_sec;
         /* for kcfg externs calculate their offsets within a .kconfig map */
         off = 0;
         for (i = 0; i < obj->nr_extern; i++) {
             ext = &obj->externs[i];
             if (ext->type != EXT_KCFG)
                 continue;
 
             ext->kcfg.data_off = roundup(off, ext->kcfg.align);
             off = ext->kcfg.data_off + ext->kcfg.sz;
             pr_debug("extern (kcfg) #%d: symbol %d, off %u, name %s\n",
                  i, ext->sym_idx, ext->kcfg.data_off, ext->name);
         }
         sec->size = off;
         n = btf_vlen(sec);
         for (i = 0; i < n; i++) {
             struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i;
 
             t = btf__type_by_id(obj->btf, vs->type);
             ext_name = btf__name_by_offset(obj->btf, t->name_off);
             ext = find_extern_by_name(obj, ext_name);
             if (!ext) {
                 pr_warn("failed to find extern definition for BTF var '%s'\n",
                     ext_name);
                 return -ESRCH;
             }
             btf_var(t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
             vs->offset = ext->kcfg.data_off;
         }
     }
     return 0;
 }
 
 static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog)
 {
     return prog->sec_idx == obj->efile.text_shndx && obj->nr_programs > 1;
 }
 
 struct bpf_program *
 bpf_object__find_program_by_name(const struct bpf_object *obj,
                  const char *name)
 {
     struct bpf_program *prog;
 
     bpf_object__for_each_program(prog, obj) {
         if (prog_is_subprog(obj, prog))
             continue;
         if (!strcmp(prog->name, name))
             return prog;
     }
     return errno = ENOENT, NULL;
 }
 
 static bool bpf_object__shndx_is_data(const struct bpf_object *obj,
                       int shndx)
 {
     switch (obj->efile.secs[shndx].sec_type) {
     case SEC_BSS:
     case SEC_DATA:
     case SEC_RODATA:
         return true;
     default:
         return false;
     }
 }
 
 static bool bpf_object__shndx_is_maps(const struct bpf_object *obj,
                       int shndx)
 {
     return shndx == obj->efile.maps_shndx ||
            shndx == obj->efile.btf_maps_shndx;
 }
 
 static enum libbpf_map_type
 bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx)
 {
     if (shndx == obj->efile.symbols_shndx)
         return LIBBPF_MAP_KCONFIG;
 
     switch (obj->efile.secs[shndx].sec_type) {
     case SEC_BSS:
         return LIBBPF_MAP_BSS;
     case SEC_DATA:
         return LIBBPF_MAP_DATA;
     case SEC_RODATA:
         return LIBBPF_MAP_RODATA;
     default:
         return LIBBPF_MAP_UNSPEC;
     }
 }
 
 static int bpf_program__record_reloc(struct bpf_program *prog,
                      struct reloc_desc *reloc_desc,
                      __u32 insn_idx, const char *sym_name,
                      const Elf64_Sym *sym, const Elf64_Rel *rel)
 {
     struct bpf_insn *insn = &prog->insns[insn_idx];
     size_t map_idx, nr_maps = prog->obj->nr_maps;
     struct bpf_object *obj = prog->obj;
     __u32 shdr_idx = sym->st_shndx;
     enum libbpf_map_type type;
     const char *sym_sec_name;
     struct bpf_map *map;
 
     if (!is_call_insn(insn) && !is_ldimm64_insn(insn)) {
         pr_warn("prog '%s': invalid relo against '%s' for insns[%d].code 0x%x\n",
             prog->name, sym_name, insn_idx, insn->code);
         return -LIBBPF_ERRNO__RELOC;
     }
 
     if (sym_is_extern(sym)) {
         int sym_idx = ELF64_R_SYM(rel->r_info);
         int i, n = obj->nr_extern;
         struct extern_desc *ext;
 
         for (i = 0; i < n; i++) {
             ext = &obj->externs[i];
             if (ext->sym_idx == sym_idx)
                 break;
         }
         if (i >= n) {
             pr_warn("prog '%s': extern relo failed to find extern for '%s' (%d)\n",
                 prog->name, sym_name, sym_idx);
             return -LIBBPF_ERRNO__RELOC;
         }
         pr_debug("prog '%s': found extern #%d '%s' (sym %d) for insn #%u\n",
              prog->name, i, ext->name, ext->sym_idx, insn_idx);
         if (insn->code == (BPF_JMP | BPF_CALL))
             reloc_desc->type = RELO_EXTERN_FUNC;
         else
             reloc_desc->type = RELO_EXTERN_VAR;
         reloc_desc->insn_idx = insn_idx;
         reloc_desc->sym_off = i; /* sym_off stores extern index */
         return 0;
     }
 
     /* sub-program call relocation */
     if (is_call_insn(insn)) {
         if (insn->src_reg != BPF_PSEUDO_CALL) {
             pr_warn("prog '%s': incorrect bpf_call opcode\n", prog->name);
             return -LIBBPF_ERRNO__RELOC;
         }
         /* text_shndx can be 0, if no default "main" program exists */
         if (!shdr_idx || shdr_idx != obj->efile.text_shndx) {
             sym_sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, shdr_idx));
             pr_warn("prog '%s': bad call relo against '%s' in section '%s'\n",
                 prog->name, sym_name, sym_sec_name);
             return -LIBBPF_ERRNO__RELOC;
         }
         if (sym->st_value % BPF_INSN_SZ) {
             pr_warn("prog '%s': bad call relo against '%s' at offset %zu\n",
                 prog->name, sym_name, (size_t)sym->st_value);
             return -LIBBPF_ERRNO__RELOC;
         }
         reloc_desc->type = RELO_CALL;
         reloc_desc->insn_idx = insn_idx;
         reloc_desc->sym_off = sym->st_value;
         return 0;
     }
 
     if (!shdr_idx || shdr_idx >= SHN_LORESERVE) {
         pr_warn("prog '%s': invalid relo against '%s' in special section 0x%x; forgot to initialize global var?..\n",
             prog->name, sym_name, shdr_idx);
         return -LIBBPF_ERRNO__RELOC;
     }
 
     /* loading subprog addresses */
     if (sym_is_subprog(sym, obj->efile.text_shndx)) {
         /* global_func: sym->st_value = offset in the section, insn->imm = 0.
          * local_func: sym->st_value = 0, insn->imm = offset in the section.
          */
         if ((sym->st_value % BPF_INSN_SZ) || (insn->imm % BPF_INSN_SZ)) {
             pr_warn("prog '%s': bad subprog addr relo against '%s' at offset %zu+%d\n",
                 prog->name, sym_name, (size_t)sym->st_value, insn->imm);
             return -LIBBPF_ERRNO__RELOC;
         }
 
         reloc_desc->type = RELO_SUBPROG_ADDR;
         reloc_desc->insn_idx = insn_idx;
         reloc_desc->sym_off = sym->st_value;
         return 0;
     }
 
     type = bpf_object__section_to_libbpf_map_type(obj, shdr_idx);
     sym_sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, shdr_idx));
 
     /* generic map reference relocation */
     if (type == LIBBPF_MAP_UNSPEC) {
         if (!bpf_object__shndx_is_maps(obj, shdr_idx)) {
             pr_warn("prog '%s': bad map relo against '%s' in section '%s'\n",
                 prog->name, sym_name, sym_sec_name);
             return -LIBBPF_ERRNO__RELOC;
         }
         for (map_idx = 0; map_idx < nr_maps; map_idx++) {
             map = &obj->maps[map_idx];
             if (map->libbpf_type != type ||
                 map->sec_idx != sym->st_shndx ||
                 map->sec_offset != sym->st_value)
                 continue;
             pr_debug("prog '%s': found map %zd (%s, sec %d, off %zu) for insn #%u\n",
                  prog->name, map_idx, map->name, map->sec_idx,
                  map->sec_offset, insn_idx);
             break;
         }
         if (map_idx >= nr_maps) {
             pr_warn("prog '%s': map relo failed to find map for section '%s', off %zu\n",
                 prog->name, sym_sec_name, (size_t)sym->st_value);
             return -LIBBPF_ERRNO__RELOC;
         }
         reloc_desc->type = RELO_LD64;
         reloc_desc->insn_idx = insn_idx;
         reloc_desc->map_idx = map_idx;
         reloc_desc->sym_off = 0; /* sym->st_value determines map_idx */
         return 0;
     }
 
     /* global data map relocation */
     if (!bpf_object__shndx_is_data(obj, shdr_idx)) {
         pr_warn("prog '%s': bad data relo against section '%s'\n",
             prog->name, sym_sec_name);
         return -LIBBPF_ERRNO__RELOC;
     }
     for (map_idx = 0; map_idx < nr_maps; map_idx++) {
         map = &obj->maps[map_idx];
         if (map->libbpf_type != type || map->sec_idx != sym->st_shndx)
             continue;
         pr_debug("prog '%s': found data map %zd (%s, sec %d, off %zu) for insn %u\n",
              prog->name, map_idx, map->name, map->sec_idx,
              map->sec_offset, insn_idx);
         break;
     }
     if (map_idx >= nr_maps) {
         pr_warn("prog '%s': data relo failed to find map for section '%s'\n",
             prog->name, sym_sec_name);
         return -LIBBPF_ERRNO__RELOC;
     }
 
     reloc_desc->type = RELO_DATA;
     reloc_desc->insn_idx = insn_idx;
     reloc_desc->map_idx = map_idx;
     reloc_desc->sym_off = sym->st_value;
     return 0;
 }
 
 static bool prog_contains_insn(const struct bpf_program *prog, size_t insn_idx)
 {
     return insn_idx >= prog->sec_insn_off &&
            insn_idx < prog->sec_insn_off + prog->sec_insn_cnt;
 }
 
 static struct bpf_program *find_prog_by_sec_insn(const struct bpf_object *obj,
                          size_t sec_idx, size_t insn_idx)
 {
     int l = 0, r = obj->nr_programs - 1, m;
     struct bpf_program *prog;
 
     while (l < r) {
         m = l + (r - l + 1) / 2;
         prog = &obj->programs[m];
 
         if (prog->sec_idx < sec_idx ||
             (prog->sec_idx == sec_idx && prog->sec_insn_off <= insn_idx))
             l = m;
         else
             r = m - 1;
     }
     /* matching program could be at index l, but it still might be the
      * wrong one, so we need to double check conditions for the last time
      */
     prog = &obj->programs[l];
     if (prog->sec_idx == sec_idx && prog_contains_insn(prog, insn_idx))
         return prog;
     return NULL;
 }
 
 static int
 bpf_object__collect_prog_relos(struct bpf_object *obj, Elf64_Shdr *shdr, Elf_Data *data)
 {
     const char *relo_sec_name, *sec_name;
     size_t sec_idx = shdr->sh_info, sym_idx;
     struct bpf_program *prog;
     struct reloc_desc *relos;
     int err, i, nrels;
     const char *sym_name;
     __u32 insn_idx;
     Elf_Scn *scn;
     Elf_Data *scn_data;
     Elf64_Sym *sym;
     Elf64_Rel *rel;
 
     if (sec_idx >= obj->efile.sec_cnt)
         return -EINVAL;
 
     scn = elf_sec_by_idx(obj, sec_idx);
     scn_data = elf_sec_data(obj, scn);
 
     relo_sec_name = elf_sec_str(obj, shdr->sh_name);
     sec_name = elf_sec_name(obj, scn);
     if (!relo_sec_name || !sec_name)
         return -EINVAL;
 
     pr_debug("sec '%s': collecting relocation for section(%zu) '%s'\n",
          relo_sec_name, sec_idx, sec_name);
     nrels = shdr->sh_size / shdr->sh_entsize;
 
     for (i = 0; i < nrels; i++) {
         rel = elf_rel_by_idx(data, i);
         if (!rel) {
             pr_warn("sec '%s': failed to get relo #%d\n", relo_sec_name, i);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         sym_idx = ELF64_R_SYM(rel->r_info);
         sym = elf_sym_by_idx(obj, sym_idx);
         if (!sym) {
             pr_warn("sec '%s': symbol #%zu not found for relo #%d\n",
                 relo_sec_name, sym_idx, i);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         if (sym->st_shndx >= obj->efile.sec_cnt) {
             pr_warn("sec '%s': corrupted symbol #%zu pointing to invalid section #%zu for relo #%d\n",
                 relo_sec_name, sym_idx, (size_t)sym->st_shndx, i);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         if (rel->r_offset % BPF_INSN_SZ || rel->r_offset >= scn_data->d_size) {
             pr_warn("sec '%s': invalid offset 0x%zx for relo #%d\n",
                 relo_sec_name, (size_t)rel->r_offset, i);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         insn_idx = rel->r_offset / BPF_INSN_SZ;
         /* relocations against static functions are recorded as
          * relocations against the section that contains a function;
          * in such case, symbol will be STT_SECTION and sym.st_name
          * will point to empty string (0), so fetch section name
          * instead
          */
         if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && sym->st_name == 0)
             sym_name = elf_sec_name(obj, elf_sec_by_idx(obj, sym->st_shndx));
         else
             sym_name = elf_sym_str(obj, sym->st_name);
         sym_name = sym_name ?: "<?";
 
         pr_debug("sec '%s': relo #%d: insn #%u against '%s'\n",
              relo_sec_name, i, insn_idx, sym_name);
 
         prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx);
         if (!prog) {
             pr_debug("sec '%s': relo #%d: couldn't find program in section '%s' for insn #%u, probably overridden weak function, skipping...\n",
                 relo_sec_name, i, sec_name, insn_idx);
             continue;
         }
 
         relos = libbpf_reallocarray(prog->reloc_desc,
                         prog->nr_reloc + 1, sizeof(*relos));
         if (!relos)
             return -ENOMEM;
         prog->reloc_desc = relos;
 
         /* adjust insn_idx to local BPF program frame of reference */
         insn_idx -= prog->sec_insn_off;
         err = bpf_program__record_reloc(prog, &relos[prog->nr_reloc],
                         insn_idx, sym_name, sym, rel);
         if (err)
             return err;
 
         prog->nr_reloc++;
     }
     return 0;
 }
 
 static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map)
 {
     int id;
 
     if (!obj->btf)
         return -ENOENT;
 
     /* if it's BTF-defined map, we don't need to search for type IDs.
      * For struct_ops map, it does not need btf_key_type_id and
      * btf_value_type_id.
      */
     if (map->sec_idx == obj->efile.btf_maps_shndx || bpf_map__is_struct_ops(map))
         return 0;
 
     /*
      * LLVM annotates global data differently in BTF, that is,
      * only as '.data', '.bss' or '.rodata'.
      */
     if (!bpf_map__is_internal(map))
         return -ENOENT;
 
     id = btf__find_by_name(obj->btf, map->real_name);
     if (id < 0)
         return id;
 
     map->btf_key_type_id = 0;
     map->btf_value_type_id = id;
     return 0;
 }
 
 static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
 {
     char file[PATH_MAX], buff[4096];
     FILE *fp;
     __u32 val;
     int err;
 
     snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
     memset(info, 0, sizeof(*info));
 
     fp = fopen(file, "r");
     if (!fp) {
         err = -errno;
         pr_warn("failed to open %s: %d. No procfs support?\n", file,
             err);
         return err;
     }
 
     while (fgets(buff, sizeof(buff), fp)) {
         if (sscanf(buff, "map_type:\t%u", &val) == 1)
             info->type = val;
         else if (sscanf(buff, "key_size:\t%u", &val) == 1)
             info->key_size = val;
         else if (sscanf(buff, "value_size:\t%u", &val) == 1)
             info->value_size = val;
         else if (sscanf(buff, "max_entries:\t%u", &val) == 1)
             info->max_entries = val;
         else if (sscanf(buff, "map_flags:\t%i", &val) == 1)
             info->map_flags = val;
     }
 
     fclose(fp);
 
     return 0;
 }
 
 bool bpf_map__autocreate(const struct bpf_map *map)
 {
     return map->autocreate;
 }
 
 int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate)
 {
     if (map->obj->loaded)
         return libbpf_err(-EBUSY);
 
     map->autocreate = autocreate;
     return 0;
 }
 
 int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 {
     struct bpf_map_info info = {};
     __u32 len = sizeof(info), name_len;
     int new_fd, err;
     char *new_name;
 
     err = bpf_obj_get_info_by_fd(fd, &info, &len);
     if (err && errno == EINVAL)
         err = bpf_get_map_info_from_fdinfo(fd, &info);
     if (err)
         return libbpf_err(err);
 
     name_len = strlen(info.name);
     if (name_len == BPF_OBJ_NAME_LEN - 1 && strncmp(map->name, info.name, name_len) == 0)
         new_name = strdup(map->name);
     else
         new_name = strdup(info.name);
 
     if (!new_name)
         return libbpf_err(-errno);
 
     new_fd = open("/", O_RDONLY | O_CLOEXEC);
     if (new_fd < 0) {
         err = -errno;
         goto err_free_new_name;
     }
 
     new_fd = dup3(fd, new_fd, O_CLOEXEC);
     if (new_fd < 0) {
         err = -errno;
         goto err_close_new_fd;
     }
 
     err = zclose(map->fd);
     if (err) {
         err = -errno;
         goto err_close_new_fd;
     }
     free(map->name);
 
     map->fd = new_fd;
     map->name = new_name;
     map->def.type = info.type;
     map->def.key_size = info.key_size;
     map->def.value_size = info.value_size;
     map->def.max_entries = info.max_entries;
     map->def.map_flags = info.map_flags;
     map->btf_key_type_id = info.btf_key_type_id;
     map->btf_value_type_id = info.btf_value_type_id;
     map->reused = true;
     map->map_extra = info.map_extra;
 
     return 0;
 
 err_close_new_fd:
     close(new_fd);
 err_free_new_name:
     free(new_name);
     return libbpf_err(err);
 }
 
 __u32 bpf_map__max_entries(const struct bpf_map *map)
 {
     return map->def.max_entries;
 }
 
 struct bpf_map *bpf_map__inner_map(struct bpf_map *map)
 {
     if (!bpf_map_type__is_map_in_map(map->def.type))
         return errno = EINVAL, NULL;
 
     return map->inner_map;
 }
 
 int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
 {
     if (map->obj->loaded)
         return libbpf_err(-EBUSY);
 
     map->def.max_entries = max_entries;
 
     /* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
     if (map->def.type == BPF_MAP_TYPE_RINGBUF)
         map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
 
     return 0;
 }
 
 static int
 bpf_object__probe_loading(struct bpf_object *obj)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     struct bpf_insn insns[] = {
         BPF_MOV64_IMM(BPF_REG_0, 0),
         BPF_EXIT_INSN(),
     };
     int ret, insn_cnt = ARRAY_SIZE(insns);
 
     if (obj->gen_loader)
         return 0;
 
     ret = bump_rlimit_memlock();
     if (ret)
         pr_warn("Failed to bump RLIMIT_MEMLOCK (err = %d), you might need to do it explicitly!\n", ret);
 
     /* make sure basic loading works */
     ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
     if (ret < 0)
         ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
     if (ret < 0) {
         ret = errno;
         cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
         pr_warn("Error in %s():%s(%d). Couldn't load trivial BPF "
             "program. Make sure your kernel supports BPF "
             "(CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is "
             "set to big enough value.\n", __func__, cp, ret);
         return -ret;
     }
     close(ret);
 
     return 0;
 }
 
 static int probe_fd(int fd)
 {
     if (fd >= 0)
         close(fd);
     return fd >= 0;
 }
 
 static int probe_kern_prog_name(void)
 {
     struct bpf_insn insns[] = {
         BPF_MOV64_IMM(BPF_REG_0, 0),
         BPF_EXIT_INSN(),
     };
     int ret, insn_cnt = ARRAY_SIZE(insns);
 
     /* make sure loading with name works */
     ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "test", "GPL", insns, insn_cnt, NULL);
     return probe_fd(ret);
 }
 
 static int probe_kern_global_data(void)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     struct bpf_insn insns[] = {
         BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
         BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
         BPF_MOV64_IMM(BPF_REG_0, 0),
         BPF_EXIT_INSN(),
     };
     int ret, map, insn_cnt = ARRAY_SIZE(insns);
 
     map = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), 32, 1, NULL);
     if (map < 0) {
         ret = -errno;
         cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
         pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
             __func__, cp, -ret);
         return ret;
     }
 
     insns[0].imm = map;
 
     ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
     close(map);
     return probe_fd(ret);
 }
 
 static int probe_kern_btf(void)
 {
     static const char strs[] = "\0int";
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_btf_func(void)
 {
     static const char strs[] = "\0int\0x\0a";
     /* void x(int a) {} */
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
         /* FUNC_PROTO */                                /* [2] */
         BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
         BTF_PARAM_ENC(7, 1),
         /* FUNC x */                                    /* [3] */
         BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0), 2),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_btf_func_global(void)
 {
     static const char strs[] = "\0int\0x\0a";
     /* static void x(int a) {} */
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
         /* FUNC_PROTO */                                /* [2] */
         BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
         BTF_PARAM_ENC(7, 1),
         /* FUNC x BTF_FUNC_GLOBAL */                    /* [3] */
         BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 2),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_btf_datasec(void)
 {
     static const char strs[] = "\0x\0.data";
     /* static int a; */
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
         /* VAR x */                                     /* [2] */
         BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
         BTF_VAR_STATIC,
         /* DATASEC val */                               /* [3] */
         BTF_TYPE_ENC(3, BTF_INFO_ENC(BTF_KIND_DATASEC, 0, 1), 4),
         BTF_VAR_SECINFO_ENC(2, 0, 4),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_btf_float(void)
 {
     static const char strs[] = "\0float";
     __u32 types[] = {
         /* float */
         BTF_TYPE_FLOAT_ENC(1, 4),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_btf_decl_tag(void)
 {
     static const char strs[] = "\0tag";
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
         /* VAR x */                                     /* [2] */
         BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
         BTF_VAR_STATIC,
         /* attr */
         BTF_TYPE_DECL_TAG_ENC(1, 2, -1),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_btf_type_tag(void)
 {
     static const char strs[] = "\0tag";
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),      /* [1] */
         /* attr */
         BTF_TYPE_TYPE_TAG_ENC(1, 1),                /* [2] */
         /* ptr */
         BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 2),   /* [3] */
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_array_mmap(void)
 {
     LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
     int fd;
 
     fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), sizeof(int), 1, &opts);
     return probe_fd(fd);
 }
 
 static int probe_kern_exp_attach_type(void)
 {
     LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE);
     struct bpf_insn insns[] = {
         BPF_MOV64_IMM(BPF_REG_0, 0),
         BPF_EXIT_INSN(),
     };
     int fd, insn_cnt = ARRAY_SIZE(insns);
 
     /* use any valid combination of program type and (optional)
      * non-zero expected attach type (i.e., not a BPF_CGROUP_INET_INGRESS)
      * to see if kernel supports expected_attach_type field for
      * BPF_PROG_LOAD command
      */
     fd = bpf_prog_load(BPF_PROG_TYPE_CGROUP_SOCK, NULL, "GPL", insns, insn_cnt, &opts);
     return probe_fd(fd);
 }
 
 static int probe_kern_probe_read_kernel(void)
 {
     struct bpf_insn insns[] = {
         BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),   /* r1 = r10 (fp) */
         BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),  /* r1 += -8 */
         BPF_MOV64_IMM(BPF_REG_2, 8),        /* r2 = 8 */
         BPF_MOV64_IMM(BPF_REG_3, 0),        /* r3 = 0 */
         BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_probe_read_kernel),
         BPF_EXIT_INSN(),
     };
     int fd, insn_cnt = ARRAY_SIZE(insns);
 
     fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
     return probe_fd(fd);
 }
 
 static int probe_prog_bind_map(void)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     struct bpf_insn insns[] = {
         BPF_MOV64_IMM(BPF_REG_0, 0),
         BPF_EXIT_INSN(),
     };
     int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);
 
     map = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), 32, 1, NULL);
     if (map < 0) {
         ret = -errno;
         cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
         pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
             __func__, cp, -ret);
         return ret;
     }
 
     prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
     if (prog < 0) {
         close(map);
         return 0;
     }
 
     ret = bpf_prog_bind_map(prog, map, NULL);
 
     close(map);
     close(prog);
 
     return ret >= 0;
 }
 
 static int probe_module_btf(void)
 {
     static const char strs[] = "\0int";
     __u32 types[] = {
         /* int */
         BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
     };
     struct bpf_btf_info info;
     __u32 len = sizeof(info);
     char name[16];
     int fd, err;
 
     fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs));
     if (fd < 0)
         return 0; /* BTF not supported at all */
 
     memset(&info, 0, sizeof(info));
     info.name = ptr_to_u64(name);
     info.name_len = sizeof(name);
 
     /* check that BPF_OBJ_GET_INFO_BY_FD supports specifying name pointer;
      * kernel's module BTF support coincides with support for
      * name/name_len fields in struct bpf_btf_info.
      */
     err = bpf_obj_get_info_by_fd(fd, &info, &len);
     close(fd);
     return !err;
 }
 
 static int probe_perf_link(void)
 {
     struct bpf_insn insns[] = {
         BPF_MOV64_IMM(BPF_REG_0, 0),
         BPF_EXIT_INSN(),
     };
     int prog_fd, link_fd, err;
 
     prog_fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL",
                 insns, ARRAY_SIZE(insns), NULL);
     if (prog_fd < 0)
         return -errno;
 
     /* use invalid perf_event FD to get EBADF, if link is supported;
      * otherwise EINVAL should be returned
      */
     link_fd = bpf_link_create(prog_fd, -1, BPF_PERF_EVENT, NULL);
     err = -errno; /* close() can clobber errno */
 
     if (link_fd >= 0)
         close(link_fd);
     close(prog_fd);
 
     return link_fd < 0 && err == -EBADF;
 }
 
 static int probe_kern_bpf_cookie(void)
 {
     struct bpf_insn insns[] = {
         BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_attach_cookie),
         BPF_EXIT_INSN(),
     };
     int ret, insn_cnt = ARRAY_SIZE(insns);
 
     ret = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL", insns, insn_cnt, NULL);
     return probe_fd(ret);
 }
 
 static int probe_kern_btf_enum64(void)
 {
     static const char strs[] = "\0enum64";
     __u32 types[] = {
         BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_ENUM64, 0, 0), 8),
     };
 
     return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                          strs, sizeof(strs)));
 }
 
 static int probe_kern_syscall_wrapper(void);
 
 enum kern_feature_result {
     FEAT_UNKNOWN = 0,
     FEAT_SUPPORTED = 1,
     FEAT_MISSING = 2,
 };
 
 typedef int (*feature_probe_fn)(void);
 
 static struct kern_feature_desc {
     const char *desc;
     feature_probe_fn probe;
     enum kern_feature_result res;
 } feature_probes[__FEAT_CNT] = {
     [FEAT_PROG_NAME] = {
         "BPF program name", probe_kern_prog_name,
     },
     [FEAT_GLOBAL_DATA] = {
         "global variables", probe_kern_global_data,
     },
     [FEAT_BTF] = {
         "minimal BTF", probe_kern_btf,
     },
     [FEAT_BTF_FUNC] = {
         "BTF functions", probe_kern_btf_func,
     },
     [FEAT_BTF_GLOBAL_FUNC] = {
         "BTF global function", probe_kern_btf_func_global,
     },
     [FEAT_BTF_DATASEC] = {
         "BTF data section and variable", probe_kern_btf_datasec,
     },
     [FEAT_ARRAY_MMAP] = {
         "ARRAY map mmap()", probe_kern_array_mmap,
     },
     [FEAT_EXP_ATTACH_TYPE] = {
         "BPF_PROG_LOAD expected_attach_type attribute",
         probe_kern_exp_attach_type,
     },
     [FEAT_PROBE_READ_KERN] = {
         "bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel,
     },
     [FEAT_PROG_BIND_MAP] = {
         "BPF_PROG_BIND_MAP support", probe_prog_bind_map,
     },
     [FEAT_MODULE_BTF] = {
         "module BTF support", probe_module_btf,
     },
     [FEAT_BTF_FLOAT] = {
         "BTF_KIND_FLOAT support", probe_kern_btf_float,
     },
     [FEAT_PERF_LINK] = {
         "BPF perf link support", probe_perf_link,
     },
     [FEAT_BTF_DECL_TAG] = {
         "BTF_KIND_DECL_TAG support", probe_kern_btf_decl_tag,
     },
     [FEAT_BTF_TYPE_TAG] = {
         "BTF_KIND_TYPE_TAG support", probe_kern_btf_type_tag,
     },
     [FEAT_MEMCG_ACCOUNT] = {
         "memcg-based memory accounting", probe_memcg_account,
     },
     [FEAT_BPF_COOKIE] = {
         "BPF cookie support", probe_kern_bpf_cookie,
     },
     [FEAT_BTF_ENUM64] = {
         "BTF_KIND_ENUM64 support", probe_kern_btf_enum64,
     },
     [FEAT_SYSCALL_WRAPPER] = {
         "Kernel using syscall wrapper", probe_kern_syscall_wrapper,
     },
 };
 
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
 {
     struct kern_feature_desc *feat = &feature_probes[feat_id];
     int ret;
 
     if (obj && obj->gen_loader)
         /* To generate loader program assume the latest kernel
          * to avoid doing extra prog_load, map_create syscalls.
          */
         return true;
 
     if (READ_ONCE(feat->res) == FEAT_UNKNOWN) {
         ret = feat->probe();
         if (ret > 0) {
             WRITE_ONCE(feat->res, FEAT_SUPPORTED);
         } else if (ret == 0) {
             WRITE_ONCE(feat->res, FEAT_MISSING);
         } else {
             pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
             WRITE_ONCE(feat->res, FEAT_MISSING);
         }
     }
 
     return READ_ONCE(feat->res) == FEAT_SUPPORTED;
 }
 
 static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
 {
     struct bpf_map_info map_info = {};
     char msg[STRERR_BUFSIZE];
     __u32 map_info_len;
     int err;
 
     map_info_len = sizeof(map_info);
 
     err = bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len);
     if (err && errno == EINVAL)
         err = bpf_get_map_info_from_fdinfo(map_fd, &map_info);
     if (err) {
         pr_warn("failed to get map info for map FD %d: %s\n", map_fd,
             libbpf_strerror_r(errno, msg, sizeof(msg)));
         return false;
     }
 
     return (map_info.type == map->def.type &&
         map_info.key_size == map->def.key_size &&
         map_info.value_size == map->def.value_size &&
         map_info.max_entries == map->def.max_entries &&
         map_info.map_flags == map->def.map_flags &&
         map_info.map_extra == map->map_extra);
 }
 
 static int
 bpf_object__reuse_map(struct bpf_map *map)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     int err, pin_fd;
 
     pin_fd = bpf_obj_get(map->pin_path);
     if (pin_fd < 0) {
         err = -errno;
         if (err == -ENOENT) {
             pr_debug("found no pinned map to reuse at '%s'\n",
                  map->pin_path);
             return 0;
         }
 
         cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
         pr_warn("couldn't retrieve pinned map '%s': %s\n",
             map->pin_path, cp);
         return err;
     }
 
     if (!map_is_reuse_compat(map, pin_fd)) {
         pr_warn("couldn't reuse pinned map at '%s': parameter mismatch\n",
             map->pin_path);
         close(pin_fd);
         return -EINVAL;
     }
 
     err = bpf_map__reuse_fd(map, pin_fd);
     close(pin_fd);
     if (err) {
         return err;
     }
     map->pinned = true;
     pr_debug("reused pinned map at '%s'\n", map->pin_path);
 
     return 0;
 }
 
 static int
 bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
 {
     enum libbpf_map_type map_type = map->libbpf_type;
     char *cp, errmsg[STRERR_BUFSIZE];
     int err, zero = 0;
 
     if (obj->gen_loader) {
         bpf_gen__map_update_elem(obj->gen_loader, map - obj->maps,
                      map->mmaped, map->def.value_size);
         if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG)
             bpf_gen__map_freeze(obj->gen_loader, map - obj->maps);
         return 0;
     }
     err = bpf_map_update_elem(map->fd, &zero, map->mmaped, 0);
     if (err) {
         err = -errno;
         cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
         pr_warn("Error setting initial map(%s) contents: %s\n",
             map->name, cp);
         return err;
     }
 
     /* Freeze .rodata and .kconfig map as read-only from syscall side. */
     if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG) {
         err = bpf_map_freeze(map->fd);
         if (err) {
             err = -errno;
             cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
             pr_warn("Error freezing map(%s) as read-only: %s\n",
                 map->name, cp);
             return err;
         }
     }
     return 0;
 }
 
 static void bpf_map__destroy(struct bpf_map *map);
 
 static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, bool is_inner)
 {
     LIBBPF_OPTS(bpf_map_create_opts, create_attr);
     struct bpf_map_def *def = &map->def;
     const char *map_name = NULL;
     int err = 0;
 
     if (kernel_supports(obj, FEAT_PROG_NAME))
         map_name = map->name;
     create_attr.map_ifindex = map->map_ifindex;
     create_attr.map_flags = def->map_flags;
     create_attr.numa_node = map->numa_node;
     create_attr.map_extra = map->map_extra;
 
     if (bpf_map__is_struct_ops(map))
         create_attr.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
 
     if (obj->btf && btf__fd(obj->btf) >= 0) {
         create_attr.btf_fd = btf__fd(obj->btf);
         create_attr.btf_key_type_id = map->btf_key_type_id;
         create_attr.btf_value_type_id = map->btf_value_type_id;
     }
 
     if (bpf_map_type__is_map_in_map(def->type)) {
         if (map->inner_map) {
             err = bpf_object__create_map(obj, map->inner_map, true);
             if (err) {
                 pr_warn("map '%s': failed to create inner map: %d\n",
                     map->name, err);
                 return err;
             }
             map->inner_map_fd = bpf_map__fd(map->inner_map);
         }
         if (map->inner_map_fd >= 0)
             create_attr.inner_map_fd = map->inner_map_fd;
     }
 
     switch (def->type) {
     case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
     case BPF_MAP_TYPE_CGROUP_ARRAY:
     case BPF_MAP_TYPE_STACK_TRACE:
     case BPF_MAP_TYPE_ARRAY_OF_MAPS:
     case BPF_MAP_TYPE_HASH_OF_MAPS:
     case BPF_MAP_TYPE_DEVMAP:
     case BPF_MAP_TYPE_DEVMAP_HASH:
     case BPF_MAP_TYPE_CPUMAP:
     case BPF_MAP_TYPE_XSKMAP:
     case BPF_MAP_TYPE_SOCKMAP:
     case BPF_MAP_TYPE_SOCKHASH:
     case BPF_MAP_TYPE_QUEUE:
     case BPF_MAP_TYPE_STACK:
         create_attr.btf_fd = 0;
         create_attr.btf_key_type_id = 0;
         create_attr.btf_value_type_id = 0;
         map->btf_key_type_id = 0;
         map->btf_value_type_id = 0;
     default:
         break;
     }
 
     if (obj->gen_loader) {
         bpf_gen__map_create(obj->gen_loader, def->type, map_name,
                     def->key_size, def->value_size, def->max_entries,
                     &create_attr, is_inner ? -1 : map - obj->maps);
         /* Pretend to have valid FD to pass various fd >= 0 checks.
          * This fd == 0 will not be used with any syscall and will be reset to -1 eventually.
          */
         map->fd = 0;
     } else {
         map->fd = bpf_map_create(def->type, map_name,
                      def->key_size, def->value_size,
                      def->max_entries, &create_attr);
     }
     if (map->fd < 0 && (create_attr.btf_key_type_id ||
                 create_attr.btf_value_type_id)) {
         char *cp, errmsg[STRERR_BUFSIZE];
 
         err = -errno;
         cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
         pr_warn("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
             map->name, cp, err);
         create_attr.btf_fd = 0;
         create_attr.btf_key_type_id = 0;
         create_attr.btf_value_type_id = 0;
         map->btf_key_type_id = 0;
         map->btf_value_type_id = 0;
         map->fd = bpf_map_create(def->type, map_name,
                      def->key_size, def->value_size,
                      def->max_entries, &create_attr);
     }
 
     err = map->fd < 0 ? -errno : 0;
 
     if (bpf_map_type__is_map_in_map(def->type) && map->inner_map) {
         if (obj->gen_loader)
             map->inner_map->fd = -1;
         bpf_map__destroy(map->inner_map);
         zfree(&map->inner_map);
     }
 
     return err;
 }
 
 static int init_map_in_map_slots(struct bpf_object *obj, struct bpf_map *map)
 {
     const struct bpf_map *targ_map;
     unsigned int i;
     int fd, err = 0;
 
     for (i = 0; i < map->init_slots_sz; i++) {
         if (!map->init_slots[i])
             continue;
 
         targ_map = map->init_slots[i];
         fd = bpf_map__fd(targ_map);
 
         if (obj->gen_loader) {
             bpf_gen__populate_outer_map(obj->gen_loader,
                             map - obj->maps, i,
                             targ_map - obj->maps);
         } else {
             err = bpf_map_update_elem(map->fd, &i, &fd, 0);
         }
         if (err) {
             err = -errno;
             pr_warn("map '%s': failed to initialize slot [%d] to map '%s' fd=%d: %d\n",
                 map->name, i, targ_map->name, fd, err);
             return err;
         }
         pr_debug("map '%s': slot [%d] set to map '%s' fd=%d\n",
              map->name, i, targ_map->name, fd);
     }
 
     zfree(&map->init_slots);
     map->init_slots_sz = 0;
 
     return 0;
 }
 
 static int init_prog_array_slots(struct bpf_object *obj, struct bpf_map *map)
 {
     const struct bpf_program *targ_prog;
     unsigned int i;
     int fd, err;
 
     if (obj->gen_loader)
         return -ENOTSUP;
 
     for (i = 0; i < map->init_slots_sz; i++) {
         if (!map->init_slots[i])
             continue;
 
         targ_prog = map->init_slots[i];
         fd = bpf_program__fd(targ_prog);
 
         err = bpf_map_update_elem(map->fd, &i, &fd, 0);
         if (err) {
             err = -errno;
             pr_warn("map '%s': failed to initialize slot [%d] to prog '%s' fd=%d: %d\n",
                 map->name, i, targ_prog->name, fd, err);
             return err;
         }
         pr_debug("map '%s': slot [%d] set to prog '%s' fd=%d\n",
              map->name, i, targ_prog->name, fd);
     }
 
     zfree(&map->init_slots);
     map->init_slots_sz = 0;
 
     return 0;
 }
 
 static int bpf_object_init_prog_arrays(struct bpf_object *obj)
 {
     struct bpf_map *map;
     int i, err;
 
     for (i = 0; i < obj->nr_maps; i++) {
         map = &obj->maps[i];
 
         if (!map->init_slots_sz || map->def.type != BPF_MAP_TYPE_PROG_ARRAY)
             continue;
 
         err = init_prog_array_slots(obj, map);
         if (err < 0) {
             zclose(map->fd);
             return err;
         }
     }
     return 0;
 }
 
 static int map_set_def_max_entries(struct bpf_map *map)
 {
     if (map->def.type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && !map->def.max_entries) {
         int nr_cpus;
 
         nr_cpus = libbpf_num_possible_cpus();
         if (nr_cpus < 0) {
             pr_warn("map '%s': failed to determine number of system CPUs: %d\n",
                 map->name, nr_cpus);
             return nr_cpus;
         }
         pr_debug("map '%s': setting size to %d\n", map->name, nr_cpus);
         map->def.max_entries = nr_cpus;
     }
 
     return 0;
 }
 
 static int
 bpf_object__create_maps(struct bpf_object *obj)
 {
     struct bpf_map *map;
     char *cp, errmsg[STRERR_BUFSIZE];
     unsigned int i, j;
     int err;
     bool retried;
 
     for (i = 0; i < obj->nr_maps; i++) {
         map = &obj->maps[i];
 
         /* To support old kernels, we skip creating global data maps
          * (.rodata, .data, .kconfig, etc); later on, during program
          * loading, if we detect that at least one of the to-be-loaded
          * programs is referencing any global data map, we'll error
          * out with program name and relocation index logged.
          * This approach allows to accommodate Clang emitting
          * unnecessary .rodata.str1.1 sections for string literals,
          * but also it allows to have CO-RE applications that use
          * global variables in some of BPF programs, but not others.
          * If those global variable-using programs are not loaded at
          * runtime due to bpf_program__set_autoload(prog, false),
          * bpf_object loading will succeed just fine even on old
          * kernels.
          */
         if (bpf_map__is_internal(map) && !kernel_supports(obj, FEAT_GLOBAL_DATA))
             map->autocreate = false;
 
         if (!map->autocreate) {
             pr_debug("map '%s': skipped auto-creating...\n", map->name);
             continue;
         }
 
         err = map_set_def_max_entries(map);
         if (err)
             goto err_out;
 
         retried = false;
 retry:
         if (map->pin_path) {
             err = bpf_object__reuse_map(map);
             if (err) {
                 pr_warn("map '%s': error reusing pinned map\n",
                     map->name);
                 goto err_out;
             }
             if (retried && map->fd < 0) {
                 pr_warn("map '%s': cannot find pinned map\n",
                     map->name);
                 err = -ENOENT;
                 goto err_out;
             }
         }
 
         if (map->fd >= 0) {
             pr_debug("map '%s': skipping creation (preset fd=%d)\n",
                  map->name, map->fd);
         } else {
             err = bpf_object__create_map(obj, map, false);
             if (err)
                 goto err_out;
 
             pr_debug("map '%s': created successfully, fd=%d\n",
                  map->name, map->fd);
 
             if (bpf_map__is_internal(map)) {
                 err = bpf_object__populate_internal_map(obj, map);
                 if (err < 0) {
                     zclose(map->fd);
                     goto err_out;
                 }
             }
 
             if (map->init_slots_sz && map->def.type != BPF_MAP_TYPE_PROG_ARRAY) {
                 err = init_map_in_map_slots(obj, map);
                 if (err < 0) {
                     zclose(map->fd);
                     goto err_out;
                 }
             }
         }
 
         if (map->pin_path && !map->pinned) {
             err = bpf_map__pin(map, NULL);
             if (err) {
                 zclose(map->fd);
                 if (!retried && err == -EEXIST) {
                     retried = true;
                     goto retry;
                 }
                 pr_warn("map '%s': failed to auto-pin at '%s': %d\n",
                     map->name, map->pin_path, err);
                 goto err_out;
             }
         }
     }
 
     return 0;
 
 err_out:
     cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
     pr_warn("map '%s': failed to create: %s(%d)\n", map->name, cp, err);
     pr_perm_msg(err);
     for (j = 0; j < i; j++)
         zclose(obj->maps[j].fd);
     return err;
 }
 
 static bool bpf_core_is_flavor_sep(const char *s)
 {
     /* check X___Y name pattern, where X and Y are not underscores */
     return s[0] != '_' &&                     /* X */
            s[1] == '_' && s[2] == '_' && s[3] == '_' &&   /* ___ */
            s[4] != '_';                   /* Y */
 }
 
 /* Given 'some_struct_name___with_flavor' return the length of a name prefix
  * before last triple underscore. Struct name part after last triple
  * underscore is ignored by BPF CO-RE relocation during relocation matching.
  */
 size_t bpf_core_essential_name_len(const char *name)
 {
     size_t n = strlen(name);
     int i;
 
     for (i = n - 5; i >= 0; i--) {
         if (bpf_core_is_flavor_sep(name + i))
             return i + 1;
     }
     return n;
 }
 
 void bpf_core_free_cands(struct bpf_core_cand_list *cands)
 {
     if (!cands)
         return;
 
     free(cands->cands);
     free(cands);
 }
 
 int bpf_core_add_cands(struct bpf_core_cand *local_cand,
                size_t local_essent_len,
                const struct btf *targ_btf,
                const char *targ_btf_name,
                int targ_start_id,
                struct bpf_core_cand_list *cands)
 {
     struct bpf_core_cand *new_cands, *cand;
     const struct btf_type *t, *local_t;
     const char *targ_name, *local_name;
     size_t targ_essent_len;
     int n, i;
 
     local_t = btf__type_by_id(local_cand->btf, local_cand->id);
     local_name = btf__str_by_offset(local_cand->btf, local_t->name_off);
 
     n = btf__type_cnt(targ_btf);
     for (i = targ_start_id; i < n; i++) {
         t = btf__type_by_id(targ_btf, i);
         if (!btf_kind_core_compat(t, local_t))
             continue;
 
         targ_name = btf__name_by_offset(targ_btf, t->name_off);
         if (str_is_empty(targ_name))
             continue;
 
         targ_essent_len = bpf_core_essential_name_len(targ_name);
         if (targ_essent_len != local_essent_len)
             continue;
 
         if (strncmp(local_name, targ_name, local_essent_len) != 0)
             continue;
 
         pr_debug("CO-RE relocating [%d] %s %s: found target candidate [%d] %s %s in [%s]\n",
              local_cand->id, btf_kind_str(local_t),
              local_name, i, btf_kind_str(t), targ_name,
              targ_btf_name);
         new_cands = libbpf_reallocarray(cands->cands, cands->len + 1,
                           sizeof(*cands->cands));
         if (!new_cands)
             return -ENOMEM;
 
         cand = &new_cands[cands->len];
         cand->btf = targ_btf;
         cand->id = i;
 
         cands->cands = new_cands;
         cands->len++;
     }
     return 0;
 }
 
 static int load_module_btfs(struct bpf_object *obj)
 {
     struct bpf_btf_info info;
     struct module_btf *mod_btf;
     struct btf *btf;
     char name[64];
     __u32 id = 0, len;
     int err, fd;
 
     if (obj->btf_modules_loaded)
         return 0;
 
     if (obj->gen_loader)
         return 0;
 
     /* don't do this again, even if we find no module BTFs */
     obj->btf_modules_loaded = true;
 
     /* kernel too old to support module BTFs */
     if (!kernel_supports(obj, FEAT_MODULE_BTF))
         return 0;
 
     while (true) {
         err = bpf_btf_get_next_id(id, &id);
         if (err && errno == ENOENT)
             return 0;
         if (err) {
             err = -errno;
             pr_warn("failed to iterate BTF objects: %d\n", err);
             return err;
         }
 
         fd = bpf_btf_get_fd_by_id(id);
         if (fd < 0) {
             if (errno == ENOENT)
                 continue; /* expected race: BTF was unloaded */
             err = -errno;
             pr_warn("failed to get BTF object #%d FD: %d\n", id, err);
             return err;
         }
 
         len = sizeof(info);
         memset(&info, 0, sizeof(info));
         info.name = ptr_to_u64(name);
         info.name_len = sizeof(name);
 
         err = bpf_obj_get_info_by_fd(fd, &info, &len);
         if (err) {
             err = -errno;
             pr_warn("failed to get BTF object #%d info: %d\n", id, err);
             goto err_out;
         }
 
         /* ignore non-module BTFs */
         if (!info.kernel_btf || strcmp(name, "vmlinux") == 0) {
             close(fd);
             continue;
         }
 
         btf = btf_get_from_fd(fd, obj->btf_vmlinux);
         err = libbpf_get_error(btf);
         if (err) {
             pr_warn("failed to load module [%s]'s BTF object #%d: %d\n",
                 name, id, err);
             goto err_out;
         }
 
         err = libbpf_ensure_mem((void **)&obj->btf_modules, &obj->btf_module_cap,
                         sizeof(*obj->btf_modules), obj->btf_module_cnt + 1);
         if (err)
             goto err_out;
 
         mod_btf = &obj->btf_modules[obj->btf_module_cnt++];
 
         mod_btf->btf = btf;
         mod_btf->id = id;
         mod_btf->fd = fd;
         mod_btf->name = strdup(name);
         if (!mod_btf->name) {
             err = -ENOMEM;
             goto err_out;
         }
         continue;
 
 err_out:
         close(fd);
         return err;
     }
 
     return 0;
 }
 
 static struct bpf_core_cand_list *
 bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 local_type_id)
 {
     struct bpf_core_cand local_cand = {};
     struct bpf_core_cand_list *cands;
     const struct btf *main_btf;
     const struct btf_type *local_t;
     const char *local_name;
     size_t local_essent_len;
     int err, i;
 
     local_cand.btf = local_btf;
     local_cand.id = local_type_id;
     local_t = btf__type_by_id(local_btf, local_type_id);
     if (!local_t)
         return ERR_PTR(-EINVAL);
 
     local_name = btf__name_by_offset(local_btf, local_t->name_off);
     if (str_is_empty(local_name))
         return ERR_PTR(-EINVAL);
     local_essent_len = bpf_core_essential_name_len(local_name);
 
     cands = calloc(1, sizeof(*cands));
     if (!cands)
         return ERR_PTR(-ENOMEM);
 
     /* Attempt to find target candidates in vmlinux BTF first */
     main_btf = obj->btf_vmlinux_override ?: obj->btf_vmlinux;
     err = bpf_core_add_cands(&local_cand, local_essent_len, main_btf, "vmlinux", 1, cands);
     if (err)
         goto err_out;
 
     /* if vmlinux BTF has any candidate, don't got for module BTFs */
     if (cands->len)
         return cands;
 
     /* if vmlinux BTF was overridden, don't attempt to load module BTFs */
     if (obj->btf_vmlinux_override)
         return cands;
 
     /* now look through module BTFs, trying to still find candidates */
     err = load_module_btfs(obj);
     if (err)
         goto err_out;
 
     for (i = 0; i < obj->btf_module_cnt; i++) {
         err = bpf_core_add_cands(&local_cand, local_essent_len,
                      obj->btf_modules[i].btf,
                      obj->btf_modules[i].name,
                      btf__type_cnt(obj->btf_vmlinux),
                      cands);
         if (err)
             goto err_out;
     }
 
     return cands;
 err_out:
     bpf_core_free_cands(cands);
     return ERR_PTR(err);
 }
 
 /* Check local and target types for compatibility. This check is used for
  * type-based CO-RE relocations and follow slightly different rules than
  * field-based relocations. This function assumes that root types were already
  * checked for name match. Beyond that initial root-level name check, names
  * are completely ignored. Compatibility rules are as follows:
  *   - any two STRUCTs/UNIONs/FWDs/ENUMs/INTs are considered compatible, but
  *     kind should match for local and target types (i.e., STRUCT is not
  *     compatible with UNION);
  *   - for ENUMs, the size is ignored;
  *   - for INT, size and signedness are ignored;
  *   - for ARRAY, dimensionality is ignored, element types are checked for
  *     compatibility recursively;
  *   - CONST/VOLATILE/RESTRICT modifiers are ignored;
  *   - TYPEDEFs/PTRs are compatible if types they pointing to are compatible;
  *   - FUNC_PROTOs are compatible if they have compatible signature: same
  *     number of input args and compatible return and argument types.
  * These rules are not set in stone and probably will be adjusted as we get
  * more experience with using BPF CO-RE relocations.
  */
 int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
                   const struct btf *targ_btf, __u32 targ_id)
 {
     return __bpf_core_types_are_compat(local_btf, local_id, targ_btf, targ_id, 32);
 }
 
 int bpf_core_types_match(const struct btf *local_btf, __u32 local_id,
              const struct btf *targ_btf, __u32 targ_id)
 {
     return __bpf_core_types_match(local_btf, local_id, targ_btf, targ_id, false, 32);
 }
 
 static size_t bpf_core_hash_fn(const void *key, void *ctx)
 {
     return (size_t)key;
 }
 
 static bool bpf_core_equal_fn(const void *k1, const void *k2, void *ctx)
 {
     return k1 == k2;
 }
 
 static void *u32_as_hash_key(__u32 x)
 {
     return (void *)(uintptr_t)x;
 }
 
 static int record_relo_core(struct bpf_program *prog,
                 const struct bpf_core_relo *core_relo, int insn_idx)
 {
     struct reloc_desc *relos, *relo;
 
     relos = libbpf_reallocarray(prog->reloc_desc,
                     prog->nr_reloc + 1, sizeof(*relos));
     if (!relos)
         return -ENOMEM;
     relo = &relos[prog->nr_reloc];
     relo->type = RELO_CORE;
     relo->insn_idx = insn_idx;
     relo->core_relo = core_relo;
     prog->reloc_desc = relos;
     prog->nr_reloc++;
     return 0;
 }
 
 static const struct bpf_core_relo *find_relo_core(struct bpf_program *prog, int insn_idx)
 {
     struct reloc_desc *relo;
     int i;
 
     for (i = 0; i < prog->nr_reloc; i++) {
         relo = &prog->reloc_desc[i];
         if (relo->type != RELO_CORE || relo->insn_idx != insn_idx)
             continue;
 
         return relo->core_relo;
     }
 
     return NULL;
 }
 
 static int bpf_core_resolve_relo(struct bpf_program *prog,
                  const struct bpf_core_relo *relo,
                  int relo_idx,
                  const struct btf *local_btf,
                  struct hashmap *cand_cache,
                  struct bpf_core_relo_res *targ_res)
 {
     struct bpf_core_spec specs_scratch[3] = {};
     const void *type_key = u32_as_hash_key(relo->type_id);
     struct bpf_core_cand_list *cands = NULL;
     const char *prog_name = prog->name;
     const struct btf_type *local_type;
     const char *local_name;
     __u32 local_id = relo->type_id;
     int err;
 
     local_type = btf__type_by_id(local_btf, local_id);
     if (!local_type)
         return -EINVAL;
 
     local_name = btf__name_by_offset(local_btf, local_type->name_off);
     if (!local_name)
         return -EINVAL;
 
     if (relo->kind != BPF_CORE_TYPE_ID_LOCAL &&
         !hashmap__find(cand_cache, type_key, (void **)&cands)) {
         cands = bpf_core_find_cands(prog->obj, local_btf, local_id);
         if (IS_ERR(cands)) {
             pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld\n",
                 prog_name, relo_idx, local_id, btf_kind_str(local_type),
                 local_name, PTR_ERR(cands));
             return PTR_ERR(cands);
         }
         err = hashmap__set(cand_cache, type_key, cands, NULL, NULL);
         if (err) {
             bpf_core_free_cands(cands);
             return err;
         }
     }
 
     return bpf_core_calc_relo_insn(prog_name, relo, relo_idx, local_btf, cands, specs_scratch,
                        targ_res);
 }
 
 static int
 bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
 {
     const struct btf_ext_info_sec *sec;
     struct bpf_core_relo_res targ_res;
     const struct bpf_core_relo *rec;
     const struct btf_ext_info *seg;
     struct hashmap_entry *entry;
     struct hashmap *cand_cache = NULL;
     struct bpf_program *prog;
     struct bpf_insn *insn;
     const char *sec_name;
     int i, err = 0, insn_idx, sec_idx, sec_num;
 
     if (obj->btf_ext->core_relo_info.len == 0)
         return 0;
 
     if (targ_btf_path) {
         obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL);
         err = libbpf_get_error(obj->btf_vmlinux_override);
         if (err) {
             pr_warn("failed to parse target BTF: %d\n", err);
             return err;
         }
     }
 
     cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
     if (IS_ERR(cand_cache)) {
         err = PTR_ERR(cand_cache);
         goto out;
     }
 
     seg = &obj->btf_ext->core_relo_info;
     sec_num = 0;
     for_each_btf_ext_sec(seg, sec) {
         sec_idx = seg->sec_idxs[sec_num];
         sec_num++;
 
         sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
         if (str_is_empty(sec_name)) {
             err = -EINVAL;
             goto out;
         }
 
         pr_debug("sec '%s': found %d CO-RE relocations\n", sec_name, sec->num_info);
 
         for_each_btf_ext_rec(seg, sec, i, rec) {
             if (rec->insn_off % BPF_INSN_SZ)
                 return -EINVAL;
             insn_idx = rec->insn_off / BPF_INSN_SZ;
             prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx);
             if (!prog) {
                 /* When __weak subprog is "overridden" by another instance
                  * of the subprog from a different object file, linker still
                  * appends all the .BTF.ext info that used to belong to that
                  * eliminated subprogram.
                  * This is similar to what x86-64 linker does for relocations.
                  * So just ignore such relocations just like we ignore
                  * subprog instructions when discovering subprograms.
                  */
                 pr_debug("sec '%s': skipping CO-RE relocation #%d for insn #%d belonging to eliminated weak subprogram\n",
                      sec_name, i, insn_idx);
                 continue;
             }
             /* no need to apply CO-RE relocation if the program is
              * not going to be loaded
              */
             if (!prog->autoload)
                 continue;
 
             /* adjust insn_idx from section frame of reference to the local
              * program's frame of reference; (sub-)program code is not yet
              * relocated, so it's enough to just subtract in-section offset
              */
             insn_idx = insn_idx - prog->sec_insn_off;
             if (insn_idx >= prog->insns_cnt)
                 return -EINVAL;
             insn = &prog->insns[insn_idx];
 
             err = record_relo_core(prog, rec, insn_idx);
             if (err) {
                 pr_warn("prog '%s': relo #%d: failed to record relocation: %d\n",
                     prog->name, i, err);
                 goto out;
             }
 
             if (prog->obj->gen_loader)
                 continue;
 
             err = bpf_core_resolve_relo(prog, rec, i, obj->btf, cand_cache, &targ_res);
             if (err) {
                 pr_warn("prog '%s': relo #%d: failed to relocate: %d\n",
                     prog->name, i, err);
                 goto out;
             }
 
             err = bpf_core_patch_insn(prog->name, insn, insn_idx, rec, i, &targ_res);
             if (err) {
                 pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n",
                     prog->name, i, insn_idx, err);
                 goto out;
             }
         }
     }
 
 out:
     /* obj->btf_vmlinux and module BTFs are freed after object load */
     btf__free(obj->btf_vmlinux_override);
     obj->btf_vmlinux_override = NULL;
 
     if (!IS_ERR_OR_NULL(cand_cache)) {
         hashmap__for_each_entry(cand_cache, entry, i) {
             bpf_core_free_cands(entry->value);
         }
         hashmap__free(cand_cache);
     }
     return err;
 }
 
 /* base map load ldimm64 special constant, used also for log fixup logic */
 #define MAP_LDIMM64_POISON_BASE 2001000000
 #define MAP_LDIMM64_POISON_PFX "200100"
 
 static void poison_map_ldimm64(struct bpf_program *prog, int relo_idx,
                    int insn_idx, struct bpf_insn *insn,
                    int map_idx, const struct bpf_map *map)
 {
     int i;
 
     pr_debug("prog '%s': relo #%d: poisoning insn #%d that loads map #%d '%s'\n",
          prog->name, relo_idx, insn_idx, map_idx, map->name);
 
     /* we turn single ldimm64 into two identical invalid calls */
     for (i = 0; i < 2; i++) {
         insn->code = BPF_JMP | BPF_CALL;
         insn->dst_reg = 0;
         insn->src_reg = 0;
         insn->off = 0;
         /* if this instruction is reachable (not a dead code),
          * verifier will complain with something like:
          * invalid func unknown#2001000123
          * where lower 123 is map index into obj->maps[] array
          */
         insn->imm = MAP_LDIMM64_POISON_BASE + map_idx;
 
         insn++;
     }
 }
 
 /* Relocate data references within program code:
  *  - map references;
  *  - global variable references;
  *  - extern references.
  */
 static int
 bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
 {
     int i;
 
     for (i = 0; i < prog->nr_reloc; i++) {
         struct reloc_desc *relo = &prog->reloc_desc[i];
         struct bpf_insn *insn = &prog->insns[relo->insn_idx];
         const struct bpf_map *map;
         struct extern_desc *ext;
 
         switch (relo->type) {
         case RELO_LD64:
             map = &obj->maps[relo->map_idx];
             if (obj->gen_loader) {
                 insn[0].src_reg = BPF_PSEUDO_MAP_IDX;
                 insn[0].imm = relo->map_idx;
             } else if (map->autocreate) {
                 insn[0].src_reg = BPF_PSEUDO_MAP_FD;
                 insn[0].imm = map->fd;
             } else {
                 poison_map_ldimm64(prog, i, relo->insn_idx, insn,
                            relo->map_idx, map);
             }
             break;
         case RELO_DATA:
             map = &obj->maps[relo->map_idx];
             insn[1].imm = insn[0].imm + relo->sym_off;
             if (obj->gen_loader) {
                 insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
                 insn[0].imm = relo->map_idx;
             } else if (map->autocreate) {
                 insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
                 insn[0].imm = map->fd;
             } else {
                 poison_map_ldimm64(prog, i, relo->insn_idx, insn,
                            relo->map_idx, map);
             }
             break;
         case RELO_EXTERN_VAR:
             ext = &obj->externs[relo->sym_off];
             if (ext->type == EXT_KCFG) {
                 if (obj->gen_loader) {
                     insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
                     insn[0].imm = obj->kconfig_map_idx;
                 } else {
                     insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
                     insn[0].imm = obj->maps[obj->kconfig_map_idx].fd;
                 }
                 insn[1].imm = ext->kcfg.data_off;
             } else /* EXT_KSYM */ {
                 if (ext->ksym.type_id && ext->is_set) { /* typed ksyms */
                     insn[0].src_reg = BPF_PSEUDO_BTF_ID;
                     insn[0].imm = ext->ksym.kernel_btf_id;
                     insn[1].imm = ext->ksym.kernel_btf_obj_fd;
                 } else { /* typeless ksyms or unresolved typed ksyms */
                     insn[0].imm = (__u32)ext->ksym.addr;
                     insn[1].imm = ext->ksym.addr >> 32;
                 }
             }
             break;
         case RELO_EXTERN_FUNC:
             ext = &obj->externs[relo->sym_off];
             insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
             if (ext->is_set) {
                 insn[0].imm = ext->ksym.kernel_btf_id;
                 insn[0].off = ext->ksym.btf_fd_idx;
             } else { /* unresolved weak kfunc */
                 insn[0].imm = 0;
                 insn[0].off = 0;
             }
             break;
         case RELO_SUBPROG_ADDR:
             if (insn[0].src_reg != BPF_PSEUDO_FUNC) {
                 pr_warn("prog '%s': relo #%d: bad insn\n",
                     prog->name, i);
                 return -EINVAL;
             }
             /* handled already */
             break;
         case RELO_CALL:
             /* handled already */
             break;
         case RELO_CORE:
             /* will be handled by bpf_program_record_relos() */
             break;
         default:
             pr_warn("prog '%s': relo #%d: bad relo type %d\n",
                 prog->name, i, relo->type);
             return -EINVAL;
         }
     }
 
     return 0;
 }
 
 static int adjust_prog_btf_ext_info(const struct bpf_object *obj,
                     const struct bpf_program *prog,
                     const struct btf_ext_info *ext_info,
                     void **prog_info, __u32 *prog_rec_cnt,
                     __u32 *prog_rec_sz)
 {
     void *copy_start = NULL, *copy_end = NULL;
     void *rec, *rec_end, *new_prog_info;
     const struct btf_ext_info_sec *sec;
     size_t old_sz, new_sz;
     int i, sec_num, sec_idx, off_adj;
 
     sec_num = 0;
     for_each_btf_ext_sec(ext_info, sec) {
         sec_idx = ext_info->sec_idxs[sec_num];
         sec_num++;
         if (prog->sec_idx != sec_idx)
             continue;
 
         for_each_btf_ext_rec(ext_info, sec, i, rec) {
             __u32 insn_off = *(__u32 *)rec / BPF_INSN_SZ;
 
             if (insn_off < prog->sec_insn_off)
                 continue;
             if (insn_off >= prog->sec_insn_off + prog->sec_insn_cnt)
                 break;
 
             if (!copy_start)
                 copy_start = rec;
             copy_end = rec + ext_info->rec_size;
         }
 
         if (!copy_start)
             return -ENOENT;
 
         /* append func/line info of a given (sub-)program to the main
          * program func/line info
          */
         old_sz = (size_t)(*prog_rec_cnt) * ext_info->rec_size;
         new_sz = old_sz + (copy_end - copy_start);
         new_prog_info = realloc(*prog_info, new_sz);
         if (!new_prog_info)
             return -ENOMEM;
         *prog_info = new_prog_info;
         *prog_rec_cnt = new_sz / ext_info->rec_size;
         memcpy(new_prog_info + old_sz, copy_start, copy_end - copy_start);
 
         /* Kernel instruction offsets are in units of 8-byte
          * instructions, while .BTF.ext instruction offsets generated
          * by Clang are in units of bytes. So convert Clang offsets
          * into kernel offsets and adjust offset according to program
          * relocated position.
          */
         off_adj = prog->sub_insn_off - prog->sec_insn_off;
         rec = new_prog_info + old_sz;
         rec_end = new_prog_info + new_sz;
         for (; rec < rec_end; rec += ext_info->rec_size) {
             __u32 *insn_off = rec;
 
             *insn_off = *insn_off / BPF_INSN_SZ + off_adj;
         }
         *prog_rec_sz = ext_info->rec_size;
         return 0;
     }
 
     return -ENOENT;
 }
 
 static int
 reloc_prog_func_and_line_info(const struct bpf_object *obj,
                   struct bpf_program *main_prog,
                   const struct bpf_program *prog)
 {
     int err;
 
     /* no .BTF.ext relocation if .BTF.ext is missing or kernel doesn't
      * supprot func/line info
      */
     if (!obj->btf_ext || !kernel_supports(obj, FEAT_BTF_FUNC))
         return 0;
 
     /* only attempt func info relocation if main program's func_info
      * relocation was successful
      */
     if (main_prog != prog && !main_prog->func_info)
         goto line_info;
 
     err = adjust_prog_btf_ext_info(obj, prog, &obj->btf_ext->func_info,
                        &main_prog->func_info,
                        &main_prog->func_info_cnt,
                        &main_prog->func_info_rec_size);
     if (err) {
         if (err != -ENOENT) {
             pr_warn("prog '%s': error relocating .BTF.ext function info: %d\n",
                 prog->name, err);
             return err;
         }
         if (main_prog->func_info) {
             /*
              * Some info has already been found but has problem
              * in the last btf_ext reloc. Must have to error out.
              */
             pr_warn("prog '%s': missing .BTF.ext function info.\n", prog->name);
             return err;
         }
         /* Have problem loading the very first info. Ignore the rest. */
         pr_warn("prog '%s': missing .BTF.ext function info for the main program, skipping all of .BTF.ext func info.\n",
             prog->name);
     }
 
 line_info:
     /* don't relocate line info if main program's relocation failed */
     if (main_prog != prog && !main_prog->line_info)
         return 0;
 
     err = adjust_prog_btf_ext_info(obj, prog, &obj->btf_ext->line_info,
                        &main_prog->line_info,
                        &main_prog->line_info_cnt,
                        &main_prog->line_info_rec_size);
     if (err) {
         if (err != -ENOENT) {
             pr_warn("prog '%s': error relocating .BTF.ext line info: %d\n",
                 prog->name, err);
             return err;
         }
         if (main_prog->line_info) {
             /*
              * Some info has already been found but has problem
              * in the last btf_ext reloc. Must have to error out.
              */
             pr_warn("prog '%s': missing .BTF.ext line info.\n", prog->name);
             return err;
         }
         /* Have problem loading the very first info. Ignore the rest. */
         pr_warn("prog '%s': missing .BTF.ext line info for the main program, skipping all of .BTF.ext line info.\n",
             prog->name);
     }
     return 0;
 }
 
 static int cmp_relo_by_insn_idx(const void *key, const void *elem)
 {
     size_t insn_idx = *(const size_t *)key;
     const struct reloc_desc *relo = elem;
 
     if (insn_idx == relo->insn_idx)
         return 0;
     return insn_idx < relo->insn_idx ? -1 : 1;
 }
 
 static struct reloc_desc *find_prog_insn_relo(const struct bpf_program *prog, size_t insn_idx)
 {
     if (!prog->nr_reloc)
         return NULL;
     return bsearch(&insn_idx, prog->reloc_desc, prog->nr_reloc,
                sizeof(*prog->reloc_desc), cmp_relo_by_insn_idx);
 }
 
 static int append_subprog_relos(struct bpf_program *main_prog, struct bpf_program *subprog)
 {
     int new_cnt = main_prog->nr_reloc + subprog->nr_reloc;
     struct reloc_desc *relos;
     int i;
 
     if (main_prog == subprog)
         return 0;
     relos = libbpf_reallocarray(main_prog->reloc_desc, new_cnt, sizeof(*relos));
     if (!relos)
         return -ENOMEM;
     if (subprog->nr_reloc)
         memcpy(relos + main_prog->nr_reloc, subprog->reloc_desc,
                sizeof(*relos) * subprog->nr_reloc);
 
     for (i = main_prog->nr_reloc; i < new_cnt; i++)
         relos[i].insn_idx += subprog->sub_insn_off;
     /* After insn_idx adjustment the 'relos' array is still sorted
      * by insn_idx and doesn't break bsearch.
      */
     main_prog->reloc_desc = relos;
     main_prog->nr_reloc = new_cnt;
     return 0;
 }
 
 static int
 bpf_object__reloc_code(struct bpf_object *obj, struct bpf_program *main_prog,
                struct bpf_program *prog)
 {
     size_t sub_insn_idx, insn_idx, new_cnt;
     struct bpf_program *subprog;
     struct bpf_insn *insns, *insn;
     struct reloc_desc *relo;
     int err;
 
     err = reloc_prog_func_and_line_info(obj, main_prog, prog);
     if (err)
         return err;
 
     for (insn_idx = 0; insn_idx < prog->sec_insn_cnt; insn_idx++) {
         insn = &main_prog->insns[prog->sub_insn_off + insn_idx];
         if (!insn_is_subprog_call(insn) && !insn_is_pseudo_func(insn))
             continue;
 
         relo = find_prog_insn_relo(prog, insn_idx);
         if (relo && relo->type == RELO_EXTERN_FUNC)
             /* kfunc relocations will be handled later
              * in bpf_object__relocate_data()
              */
             continue;
         if (relo && relo->type != RELO_CALL && relo->type != RELO_SUBPROG_ADDR) {
             pr_warn("prog '%s': unexpected relo for insn #%zu, type %d\n",
                 prog->name, insn_idx, relo->type);
             return -LIBBPF_ERRNO__RELOC;
         }
         if (relo) {
             /* sub-program instruction index is a combination of
              * an offset of a symbol pointed to by relocation and
              * call instruction's imm field; for global functions,
              * call always has imm = -1, but for static functions
              * relocation is against STT_SECTION and insn->imm
              * points to a start of a static function
              *
              * for subprog addr relocation, the relo->sym_off + insn->imm is
              * the byte offset in the corresponding section.
              */
             if (relo->type == RELO_CALL)
                 sub_insn_idx = relo->sym_off / BPF_INSN_SZ + insn->imm + 1;
             else
                 sub_insn_idx = (relo->sym_off + insn->imm) / BPF_INSN_SZ;
         } else if (insn_is_pseudo_func(insn)) {
             /*
              * RELO_SUBPROG_ADDR relo is always emitted even if both
              * functions are in the same section, so it shouldn't reach here.
              */
             pr_warn("prog '%s': missing subprog addr relo for insn #%zu\n",
                 prog->name, insn_idx);
             return -LIBBPF_ERRNO__RELOC;
         } else {
             /* if subprogram call is to a static function within
              * the same ELF section, there won't be any relocation
              * emitted, but it also means there is no additional
              * offset necessary, insns->imm is relative to
              * instruction's original position within the section
              */
             sub_insn_idx = prog->sec_insn_off + insn_idx + insn->imm + 1;
         }
 
         /* we enforce that sub-programs should be in .text section */
         subprog = find_prog_by_sec_insn(obj, obj->efile.text_shndx, sub_insn_idx);
         if (!subprog) {
             pr_warn("prog '%s': no .text section found yet sub-program call exists\n",
                 prog->name);
             return -LIBBPF_ERRNO__RELOC;
         }
 
         /* if it's the first call instruction calling into this
          * subprogram (meaning this subprog hasn't been processed
          * yet) within the context of current main program:
          *   - append it at the end of main program's instructions blog;
          *   - process is recursively, while current program is put on hold;
          *   - if that subprogram calls some other not yet processes
          *   subprogram, same thing will happen recursively until
          *   there are no more unprocesses subprograms left to append
          *   and relocate.
          */
         if (subprog->sub_insn_off == 0) {
             subprog->sub_insn_off = main_prog->insns_cnt;
 
             new_cnt = main_prog->insns_cnt + subprog->insns_cnt;
             insns = libbpf_reallocarray(main_prog->insns, new_cnt, sizeof(*insns));
             if (!insns) {
                 pr_warn("prog '%s': failed to realloc prog code\n", main_prog->name);
                 return -ENOMEM;
             }
             main_prog->insns = insns;
             main_prog->insns_cnt = new_cnt;
 
             memcpy(main_prog->insns + subprog->sub_insn_off, subprog->insns,
                    subprog->insns_cnt * sizeof(*insns));
 
             pr_debug("prog '%s': added %zu insns from sub-prog '%s'\n",
                  main_prog->name, subprog->insns_cnt, subprog->name);
 
             /* The subprog insns are now appended. Append its relos too. */
             err = append_subprog_relos(main_prog, subprog);
             if (err)
                 return err;
             err = bpf_object__reloc_code(obj, main_prog, subprog);
             if (err)
                 return err;
         }
 
         /* main_prog->insns memory could have been re-allocated, so
          * calculate pointer again
          */
         insn = &main_prog->insns[prog->sub_insn_off + insn_idx];
         /* calculate correct instruction position within current main
          * prog; each main prog can have a different set of
          * subprograms appended (potentially in different order as
          * well), so position of any subprog can be different for
          * different main programs */
         insn->imm = subprog->sub_insn_off - (prog->sub_insn_off + insn_idx) - 1;
 
         pr_debug("prog '%s': insn #%zu relocated, imm %d points to subprog '%s' (now at %zu offset)\n",
              prog->name, insn_idx, insn->imm, subprog->name, subprog->sub_insn_off);
     }
 
     return 0;
 }
 
 /*
  * Relocate sub-program calls.
  *
  * Algorithm operates as follows. Each entry-point BPF program (referred to as
  * main prog) is processed separately. For each subprog (non-entry functions,
  * that can be called from either entry progs or other subprogs) gets their
  * sub_insn_off reset to zero. This serves as indicator that this subprogram
  * hasn't been yet appended and relocated within current main prog. Once its
  * relocated, sub_insn_off will point at the position within current main prog
  * where given subprog was appended. This will further be used to relocate all
  * the call instructions jumping into this subprog.
  *
  * We start with main program and process all call instructions. If the call
  * is into a subprog that hasn't been processed (i.e., subprog->sub_insn_off
  * is zero), subprog instructions are appended at the end of main program's
  * instruction array. Then main program is "put on hold" while we recursively
  * process newly appended subprogram. If that subprogram calls into another
  * subprogram that hasn't been appended, new subprogram is appended again to
  * the *main* prog's instructions (subprog's instructions are always left
  * untouched, as they need to be in unmodified state for subsequent main progs
  * and subprog instructions are always sent only as part of a main prog) and
  * the process continues recursively. Once all the subprogs called from a main
  * prog or any of its subprogs are appended (and relocated), all their
  * positions within finalized instructions array are known, so it's easy to
  * rewrite call instructions with correct relative offsets, corresponding to
  * desired target subprog.
  *
  * Its important to realize that some subprogs might not be called from some
  * main prog and any of its called/used subprogs. Those will keep their
  * subprog->sub_insn_off as zero at all times and won't be appended to current
  * main prog and won't be relocated within the context of current main prog.
  * They might still be used from other main progs later.
  *
  * Visually this process can be shown as below. Suppose we have two main
  * programs mainA and mainB and BPF object contains three subprogs: subA,
  * subB, and subC. mainA calls only subA, mainB calls only subC, but subA and
  * subC both call subB:
  *
  *        +--------+ +-------+
  *        |        v v       |
  *     +--+---+ +--+-+-+ +---+--+
  *     | subA | | subB | | subC |
  *     +--+---+ +------+ +---+--+
  *        ^                  ^
  *        |                  |
  *    +---+-------+   +------+----+
  *    |   mainA   |   |   mainB   |
  *    +-----------+   +-----------+
  *
  * We'll start relocating mainA, will find subA, append it and start
  * processing sub A recursively:
  *
  *    +-----------+------+
  *    |   mainA   | subA |
  *    +-----------+------+
  *
  * At this point we notice that subB is used from subA, so we append it and
  * relocate (there are no further subcalls from subB):
  *
  *    +-----------+------+------+
  *    |   mainA   | subA | subB |
  *    +-----------+------+------+
  *
  * At this point, we relocate subA calls, then go one level up and finish with
  * relocatin mainA calls. mainA is done.
  *
  * For mainB process is similar but results in different order. We start with
  * mainB and skip subA and subB, as mainB never calls them (at least
  * directly), but we see subC is needed, so we append and start processing it:
  *
  *    +-----------+------+
  *    |   mainB   | subC |
  *    +-----------+------+
  * Now we see subC needs subB, so we go back to it, append and relocate it:
  *
  *    +-----------+------+------+
  *    |   mainB   | subC | subB |
  *    +-----------+------+------+
  *
  * At this point we unwind recursion, relocate calls in subC, then in mainB.
  */
 static int
 bpf_object__relocate_calls(struct bpf_object *obj, struct bpf_program *prog)
 {
     struct bpf_program *subprog;
     int i, err;
 
     /* mark all subprogs as not relocated (yet) within the context of
      * current main program
      */
     for (i = 0; i < obj->nr_programs; i++) {
         subprog = &obj->programs[i];
         if (!prog_is_subprog(obj, subprog))
             continue;
 
         subprog->sub_insn_off = 0;
     }
 
     err = bpf_object__reloc_code(obj, prog, prog);
     if (err)
         return err;
 
     return 0;
 }
 
 static void
 bpf_object__free_relocs(struct bpf_object *obj)
 {
     struct bpf_program *prog;
     int i;
 
     /* free up relocation descriptors */
     for (i = 0; i < obj->nr_programs; i++) {
         prog = &obj->programs[i];
         zfree(&prog->reloc_desc);
         prog->nr_reloc = 0;
     }
 }
 
 static int cmp_relocs(const void *_a, const void *_b)
 {
     const struct reloc_desc *a = _a;
     const struct reloc_desc *b = _b;
 
     if (a->insn_idx != b->insn_idx)
         return a->insn_idx < b->insn_idx ? -1 : 1;
 
     /* no two relocations should have the same insn_idx, but ... */
     if (a->type != b->type)
         return a->type < b->type ? -1 : 1;
 
     return 0;
 }
 
 static void bpf_object__sort_relos(struct bpf_object *obj)
 {
     int i;
 
     for (i = 0; i < obj->nr_programs; i++) {
         struct bpf_program *p = &obj->programs[i];
 
         if (!p->nr_reloc)
             continue;
 
         qsort(p->reloc_desc, p->nr_reloc, sizeof(*p->reloc_desc), cmp_relocs);
     }
 }
 
 static int
 bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
 {
     struct bpf_program *prog;
     size_t i, j;
     int err;
 
     if (obj->btf_ext) {
         err = bpf_object__relocate_core(obj, targ_btf_path);
         if (err) {
             pr_warn("failed to perform CO-RE relocations: %d\n",
                 err);
             return err;
         }
         bpf_object__sort_relos(obj);
     }
 
     /* Before relocating calls pre-process relocations and mark
      * few ld_imm64 instructions that points to subprogs.
      * Otherwise bpf_object__reloc_code() later would have to consider
      * all ld_imm64 insns as relocation candidates. That would
      * reduce relocation speed, since amount of find_prog_insn_relo()
      * would increase and most of them will fail to find a relo.
      */
     for (i = 0; i < obj->nr_programs; i++) {
         prog = &obj->programs[i];
         for (j = 0; j < prog->nr_reloc; j++) {
             struct reloc_desc *relo = &prog->reloc_desc[j];
             struct bpf_insn *insn = &prog->insns[relo->insn_idx];
 
             /* mark the insn, so it's recognized by insn_is_pseudo_func() */
             if (relo->type == RELO_SUBPROG_ADDR)
                 insn[0].src_reg = BPF_PSEUDO_FUNC;
         }
     }
 
     /* relocate subprogram calls and append used subprograms to main
      * programs; each copy of subprogram code needs to be relocated
      * differently for each main program, because its code location might
      * have changed.
      * Append subprog relos to main programs to allow data relos to be
      * processed after text is completely relocated.
      */
     for (i = 0; i < obj->nr_programs; i++) {
         prog = &obj->programs[i];
         /* sub-program's sub-calls are relocated within the context of
          * its main program only
          */
         if (prog_is_subprog(obj, prog))
             continue;
         if (!prog->autoload)
             continue;
 
         err = bpf_object__relocate_calls(obj, prog);
         if (err) {
             pr_warn("prog '%s': failed to relocate calls: %d\n",
                 prog->name, err);
             return err;
         }
     }
     /* Process data relos for main programs */
     for (i = 0; i < obj->nr_programs; i++) {
         prog = &obj->programs[i];
         if (prog_is_subprog(obj, prog))
             continue;
         if (!prog->autoload)
             continue;
         err = bpf_object__relocate_data(obj, prog);
         if (err) {
             pr_warn("prog '%s': failed to relocate data references: %d\n",
                 prog->name, err);
             return err;
         }
     }
 
     return 0;
 }
 
 static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
                         Elf64_Shdr *shdr, Elf_Data *data);
 
 static int bpf_object__collect_map_relos(struct bpf_object *obj,
                      Elf64_Shdr *shdr, Elf_Data *data)
 {
     const int bpf_ptr_sz = 8, host_ptr_sz = sizeof(void *);
     int i, j, nrels, new_sz;
     const struct btf_var_secinfo *vi = NULL;
     const struct btf_type *sec, *var, *def;
     struct bpf_map *map = NULL, *targ_map = NULL;
     struct bpf_program *targ_prog = NULL;
     bool is_prog_array, is_map_in_map;
     const struct btf_member *member;
     const char *name, *mname, *type;
     unsigned int moff;
     Elf64_Sym *sym;
     Elf64_Rel *rel;
     void *tmp;
 
     if (!obj->efile.btf_maps_sec_btf_id || !obj->btf)
         return -EINVAL;
     sec = btf__type_by_id(obj->btf, obj->efile.btf_maps_sec_btf_id);
     if (!sec)
         return -EINVAL;
 
     nrels = shdr->sh_size / shdr->sh_entsize;
     for (i = 0; i < nrels; i++) {
         rel = elf_rel_by_idx(data, i);
         if (!rel) {
             pr_warn(".maps relo #%d: failed to get ELF relo\n", i);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         sym = elf_sym_by_idx(obj, ELF64_R_SYM(rel->r_info));
         if (!sym) {
             pr_warn(".maps relo #%d: symbol %zx not found\n",
                 i, (size_t)ELF64_R_SYM(rel->r_info));
             return -LIBBPF_ERRNO__FORMAT;
         }
         name = elf_sym_str(obj, sym->st_name) ?: "<?>";
 
         pr_debug(".maps relo #%d: for %zd value %zd rel->r_offset %zu name %d ('%s')\n",
              i, (ssize_t)(rel->r_info >> 32), (size_t)sym->st_value,
              (size_t)rel->r_offset, sym->st_name, name);
 
         for (j = 0; j < obj->nr_maps; j++) {
             map = &obj->maps[j];
             if (map->sec_idx != obj->efile.btf_maps_shndx)
                 continue;
 
             vi = btf_var_secinfos(sec) + map->btf_var_idx;
             if (vi->offset <= rel->r_offset &&
                 rel->r_offset + bpf_ptr_sz <= vi->offset + vi->size)
                 break;
         }
         if (j == obj->nr_maps) {
             pr_warn(".maps relo #%d: cannot find map '%s' at rel->r_offset %zu\n",
                 i, name, (size_t)rel->r_offset);
             return -EINVAL;
         }
 
         is_map_in_map = bpf_map_type__is_map_in_map(map->def.type);
         is_prog_array = map->def.type == BPF_MAP_TYPE_PROG_ARRAY;
         type = is_map_in_map ? "map" : "prog";
         if (is_map_in_map) {
             if (sym->st_shndx != obj->efile.btf_maps_shndx) {
                 pr_warn(".maps relo #%d: '%s' isn't a BTF-defined map\n",
                     i, name);
                 return -LIBBPF_ERRNO__RELOC;
             }
             if (map->def.type == BPF_MAP_TYPE_HASH_OF_MAPS &&
                 map->def.key_size != sizeof(int)) {
                 pr_warn(".maps relo #%d: hash-of-maps '%s' should have key size %zu.\n",
                     i, map->name, sizeof(int));
                 return -EINVAL;
             }
             targ_map = bpf_object__find_map_by_name(obj, name);
             if (!targ_map) {
                 pr_warn(".maps relo #%d: '%s' isn't a valid map reference\n",
                     i, name);
                 return -ESRCH;
             }
         } else if (is_prog_array) {
             targ_prog = bpf_object__find_program_by_name(obj, name);
             if (!targ_prog) {
                 pr_warn(".maps relo #%d: '%s' isn't a valid program reference\n",
                     i, name);
                 return -ESRCH;
             }
             if (targ_prog->sec_idx != sym->st_shndx ||
                 targ_prog->sec_insn_off * 8 != sym->st_value ||
                 prog_is_subprog(obj, targ_prog)) {
                 pr_warn(".maps relo #%d: '%s' isn't an entry-point program\n",
                     i, name);
                 return -LIBBPF_ERRNO__RELOC;
             }
         } else {
             return -EINVAL;
         }
 
         var = btf__type_by_id(obj->btf, vi->type);
         def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
         if (btf_vlen(def) == 0)
             return -EINVAL;
         member = btf_members(def) + btf_vlen(def) - 1;
         mname = btf__name_by_offset(obj->btf, member->name_off);
         if (strcmp(mname, "values"))
             return -EINVAL;
 
         moff = btf_member_bit_offset(def, btf_vlen(def) - 1) / 8;
         if (rel->r_offset - vi->offset < moff)
             return -EINVAL;
 
         moff = rel->r_offset - vi->offset - moff;
         /* here we use BPF pointer size, which is always 64 bit, as we
          * are parsing ELF that was built for BPF target
          */
         if (moff % bpf_ptr_sz)
             return -EINVAL;
         moff /= bpf_ptr_sz;
         if (moff >= map->init_slots_sz) {
             new_sz = moff + 1;
             tmp = libbpf_reallocarray(map->init_slots, new_sz, host_ptr_sz);
             if (!tmp)
                 return -ENOMEM;
             map->init_slots = tmp;
             memset(map->init_slots + map->init_slots_sz, 0,
                    (new_sz - map->init_slots_sz) * host_ptr_sz);
             map->init_slots_sz = new_sz;
         }
         map->init_slots[moff] = is_map_in_map ? (void *)targ_map : (void *)targ_prog;
 
         pr_debug(".maps relo #%d: map '%s' slot [%d] points to %s '%s'\n",
              i, map->name, moff, type, name);
     }
 
     return 0;
 }
 
 static int bpf_object__collect_relos(struct bpf_object *obj)
 {
     int i, err;
 
     for (i = 0; i < obj->efile.sec_cnt; i++) {
         struct elf_sec_desc *sec_desc = &obj->efile.secs[i];
         Elf64_Shdr *shdr;
         Elf_Data *data;
         int idx;
 
         if (sec_desc->sec_type != SEC_RELO)
             continue;
 
         shdr = sec_desc->shdr;
         data = sec_desc->data;
         idx = shdr->sh_info;
 
         if (shdr->sh_type != SHT_REL) {
             pr_warn("internal error at %d\n", __LINE__);
             return -LIBBPF_ERRNO__INTERNAL;
         }
 
         if (idx == obj->efile.st_ops_shndx)
             err = bpf_object__collect_st_ops_relos(obj, shdr, data);
         else if (idx == obj->efile.btf_maps_shndx)
             err = bpf_object__collect_map_relos(obj, shdr, data);
         else
             err = bpf_object__collect_prog_relos(obj, shdr, data);
         if (err)
             return err;
     }
 
     bpf_object__sort_relos(obj);
     return 0;
 }
 
 static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id)
 {
     if (BPF_CLASS(insn->code) == BPF_JMP &&
         BPF_OP(insn->code) == BPF_CALL &&
         BPF_SRC(insn->code) == BPF_K &&
         insn->src_reg == 0 &&
         insn->dst_reg == 0) {
             *func_id = insn->imm;
             return true;
     }
     return false;
 }
 
 static int bpf_object__sanitize_prog(struct bpf_object *obj, struct bpf_program *prog)
 {
     struct bpf_insn *insn = prog->insns;
     enum bpf_func_id func_id;
     int i;
 
     if (obj->gen_loader)
         return 0;
 
     for (i = 0; i < prog->insns_cnt; i++, insn++) {
         if (!insn_is_helper_call(insn, &func_id))
             continue;
 
         /* on kernels that don't yet support
          * bpf_probe_read_{kernel,user}[_str] helpers, fall back
          * to bpf_probe_read() which works well for old kernels
          */
         switch (func_id) {
         case BPF_FUNC_probe_read_kernel:
         case BPF_FUNC_probe_read_user:
             if (!kernel_supports(obj, FEAT_PROBE_READ_KERN))
                 insn->imm = BPF_FUNC_probe_read;
             break;
         case BPF_FUNC_probe_read_kernel_str:
         case BPF_FUNC_probe_read_user_str:
             if (!kernel_supports(obj, FEAT_PROBE_READ_KERN))
                 insn->imm = BPF_FUNC_probe_read_str;
             break;
         default:
             break;
         }
     }
     return 0;
 }
 
 static int libbpf_find_attach_btf_id(struct bpf_program *prog, const char *attach_name,
                      int *btf_obj_fd, int *btf_type_id);
 
 /* this is called as prog->sec_def->prog_prepare_load_fn for libbpf-supported sec_defs */
 static int libbpf_prepare_prog_load(struct bpf_program *prog,
                     struct bpf_prog_load_opts *opts, long cookie)
 {
     enum sec_def_flags def = cookie;
 
     /* old kernels might not support specifying expected_attach_type */
     if ((def & SEC_EXP_ATTACH_OPT) && !kernel_supports(prog->obj, FEAT_EXP_ATTACH_TYPE))
         opts->expected_attach_type = 0;
 
     if (def & SEC_SLEEPABLE)
         opts->prog_flags |= BPF_F_SLEEPABLE;
 
     if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_FRAGS))
         opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;
 
     if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
         int btf_obj_fd = 0, btf_type_id = 0, err;
         const char *attach_name;
 
         attach_name = strchr(prog->sec_name, '/');
         if (!attach_name) {
             /* if BPF program is annotated with just SEC("fentry")
              * (or similar) without declaratively specifying
              * target, then it is expected that target will be
              * specified with bpf_program__set_attach_target() at
              * runtime before BPF object load step. If not, then
              * there is nothing to load into the kernel as BPF
              * verifier won't be able to validate BPF program
              * correctness anyways.
              */
             pr_warn("prog '%s': no BTF-based attach target is specified, use bpf_program__set_attach_target()\n",
                 prog->name);
             return -EINVAL;
         }
         attach_name++; /* skip over / */
 
         err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);
         if (err)
             return err;
 
         /* cache resolved BTF FD and BTF type ID in the prog */
         prog->attach_btf_obj_fd = btf_obj_fd;
         prog->attach_btf_id = btf_type_id;
 
         /* but by now libbpf common logic is not utilizing
          * prog->atach_btf_obj_fd/prog->attach_btf_id anymore because
          * this callback is called after opts were populated by
          * libbpf, so this callback has to update opts explicitly here
          */
         opts->attach_btf_obj_fd = btf_obj_fd;
         opts->attach_btf_id = btf_type_id;
     }
     return 0;
 }
 
 static void fixup_verifier_log(struct bpf_program *prog, char *buf, size_t buf_sz);
 
 static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog,
                 struct bpf_insn *insns, int insns_cnt,
                 const char *license, __u32 kern_version, int *prog_fd)
 {
     LIBBPF_OPTS(bpf_prog_load_opts, load_attr);
     const char *prog_name = NULL;
     char *cp, errmsg[STRERR_BUFSIZE];
     size_t log_buf_size = 0;
     char *log_buf = NULL, *tmp;
     int btf_fd, ret, err;
     bool own_log_buf = true;
     __u32 log_level = prog->log_level;
 
     if (prog->type == BPF_PROG_TYPE_UNSPEC) {
         /*
          * The program type must be set.  Most likely we couldn't find a proper
          * section definition at load time, and thus we didn't infer the type.
          */
         pr_warn("prog '%s': missing BPF prog type, check ELF section name '%s'\n",
             prog->name, prog->sec_name);
         return -EINVAL;
     }
 
     if (!insns || !insns_cnt)
         return -EINVAL;
 
     load_attr.expected_attach_type = prog->expected_attach_type;
     if (kernel_supports(obj, FEAT_PROG_NAME))
         prog_name = prog->name;
     load_attr.attach_prog_fd = prog->attach_prog_fd;
     load_attr.attach_btf_obj_fd = prog->attach_btf_obj_fd;
     load_attr.attach_btf_id = prog->attach_btf_id;
     load_attr.kern_version = kern_version;
     load_attr.prog_ifindex = prog->prog_ifindex;
 
     /* specify func_info/line_info only if kernel supports them */
     btf_fd = bpf_object__btf_fd(obj);
     if (btf_fd >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) {
         load_attr.prog_btf_fd = btf_fd;
         load_attr.func_info = prog->func_info;
         load_attr.func_info_rec_size = prog->func_info_rec_size;
         load_attr.func_info_cnt = prog->func_info_cnt;
         load_attr.line_info = prog->line_info;
         load_attr.line_info_rec_size = prog->line_info_rec_size;
         load_attr.line_info_cnt = prog->line_info_cnt;
     }
     load_attr.log_level = log_level;
     load_attr.prog_flags = prog->prog_flags;
     load_attr.fd_array = obj->fd_array;
 
     /* adjust load_attr if sec_def provides custom preload callback */
     if (prog->sec_def && prog->sec_def->prog_prepare_load_fn) {
         err = prog->sec_def->prog_prepare_load_fn(prog, &load_attr, prog->sec_def->cookie);
         if (err < 0) {
             pr_warn("prog '%s': failed to prepare load attributes: %d\n",
                 prog->name, err);
             return err;
         }
         insns = prog->insns;
         insns_cnt = prog->insns_cnt;
     }
 
     if (obj->gen_loader) {
         bpf_gen__prog_load(obj->gen_loader, prog->type, prog->name,
                    license, insns, insns_cnt, &load_attr,
                    prog - obj->programs);
         *prog_fd = -1;
         return 0;
     }
 
 retry_load:
     /* if log_level is zero, we don't request logs initially even if
      * custom log_buf is specified; if the program load fails, then we'll
      * bump log_level to 1 and use either custom log_buf or we'll allocate
      * our own and retry the load to get details on what failed
      */
     if (log_level) {
         if (prog->log_buf) {
             log_buf = prog->log_buf;
             log_buf_size = prog->log_size;
             own_log_buf = false;
         } else if (obj->log_buf) {
             log_buf = obj->log_buf;
             log_buf_size = obj->log_size;
             own_log_buf = false;
         } else {
             log_buf_size = max((size_t)BPF_LOG_BUF_SIZE, log_buf_size * 2);
             tmp = realloc(log_buf, log_buf_size);
             if (!tmp) {
                 ret = -ENOMEM;
                 goto out;
             }
             log_buf = tmp;
             log_buf[0] = '\0';
             own_log_buf = true;
         }
     }
 
     load_attr.log_buf = log_buf;
     load_attr.log_size = log_buf_size;
     load_attr.log_level = log_level;
 
     ret = bpf_prog_load(prog->type, prog_name, license, insns, insns_cnt, &load_attr);
     if (ret >= 0) {
         if (log_level && own_log_buf) {
             pr_debug("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
                  prog->name, log_buf);
         }
 
         if (obj->has_rodata && kernel_supports(obj, FEAT_PROG_BIND_MAP)) {
             struct bpf_map *map;
             int i;
 
             for (i = 0; i < obj->nr_maps; i++) {
                 map = &prog->obj->maps[i];
                 if (map->libbpf_type != LIBBPF_MAP_RODATA)
                     continue;
 
                 if (bpf_prog_bind_map(ret, bpf_map__fd(map), NULL)) {
                     cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
                     pr_warn("prog '%s': failed to bind map '%s': %s\n",
                         prog->name, map->real_name, cp);
                     /* Don't fail hard if can't bind rodata. */
                 }
             }
         }
 
         *prog_fd = ret;
         ret = 0;
         goto out;
     }
 
     if (log_level == 0) {
         log_level = 1;
         goto retry_load;
     }
     /* On ENOSPC, increase log buffer size and retry, unless custom
      * log_buf is specified.
      * Be careful to not overflow u32, though. Kernel's log buf size limit
      * isn't part of UAPI so it can always be bumped to full 4GB. So don't
      * multiply by 2 unless we are sure we'll fit within 32 bits.
      * Currently, we'll get -EINVAL when we reach (UINT_MAX >> 2).
      */
     if (own_log_buf && errno == ENOSPC && log_buf_size <= UINT_MAX / 2)
         goto retry_load;
 
     ret = -errno;
 
     /* post-process verifier log to improve error descriptions */
     fixup_verifier_log(prog, log_buf, log_buf_size);
 
     cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
     pr_warn("prog '%s': BPF program load failed: %s\n", prog->name, cp);
     pr_perm_msg(ret);
 
     if (own_log_buf && log_buf && log_buf[0] != '\0') {
         pr_warn("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
             prog->name, log_buf);
     }
 
 out:
     if (own_log_buf)
         free(log_buf);
     return ret;
 }
 
 static char *find_prev_line(char *buf, char *cur)
 {
     char *p;
 
     if (cur == buf) /* end of a log buf */
         return NULL;
 
     p = cur - 1;
     while (p - 1 >= buf && *(p - 1) != '\n')
         p--;
 
     return p;
 }
 
 static void patch_log(char *buf, size_t buf_sz, size_t log_sz,
               char *orig, size_t orig_sz, const char *patch)
 {
     /* size of the remaining log content to the right from the to-be-replaced part */
     size_t rem_sz = (buf + log_sz) - (orig + orig_sz);
     size_t patch_sz = strlen(patch);
 
     if (patch_sz != orig_sz) {
         /* If patch line(s) are longer than original piece of verifier log,
          * shift log contents by (patch_sz - orig_sz) bytes to the right
          * starting from after to-be-replaced part of the log.
          *
          * If patch line(s) are shorter than original piece of verifier log,
          * shift log contents by (orig_sz - patch_sz) bytes to the left
          * starting from after to-be-replaced part of the log
          *
          * We need to be careful about not overflowing available
          * buf_sz capacity. If that's the case, we'll truncate the end
          * of the original log, as necessary.
          */
         if (patch_sz > orig_sz) {
             if (orig + patch_sz >= buf + buf_sz) {
                 /* patch is big enough to cover remaining space completely */
                 patch_sz -= (orig + patch_sz) - (buf + buf_sz) + 1;
                 rem_sz = 0;
             } else if (patch_sz - orig_sz > buf_sz - log_sz) {
                 /* patch causes part of remaining log to be truncated */
                 rem_sz -= (patch_sz - orig_sz) - (buf_sz - log_sz);
             }
         }
         /* shift remaining log to the right by calculated amount */
         memmove(orig + patch_sz, orig + orig_sz, rem_sz);
     }
 
     memcpy(orig, patch, patch_sz);
 }
 
 static void fixup_log_failed_core_relo(struct bpf_program *prog,
                        char *buf, size_t buf_sz, size_t log_sz,
                        char *line1, char *line2, char *line3)
 {
     /* Expected log for failed and not properly guarded CO-RE relocation:
      * line1 -> 123: (85) call unknown#195896080
      * line2 -> invalid func unknown#195896080
      * line3 -> <anything else or end of buffer>
      *
      * "123" is the index of the instruction that was poisoned. We extract
      * instruction index to find corresponding CO-RE relocation and
      * replace this part of the log with more relevant information about
      * failed CO-RE relocation.
      */
     const struct bpf_core_relo *relo;
     struct bpf_core_spec spec;
     char patch[512], spec_buf[256];
     int insn_idx, err, spec_len;
 
     if (sscanf(line1, "%d: (%*d) call unknown#195896080\n", &insn_idx) != 1)
         return;
 
     relo = find_relo_core(prog, insn_idx);
     if (!relo)
         return;
 
     err = bpf_core_parse_spec(prog->name, prog->obj->btf, relo, &spec);
     if (err)
         return;
 
     spec_len = bpf_core_format_spec(spec_buf, sizeof(spec_buf), &spec);
     snprintf(patch, sizeof(patch),
          "%d: <invalid CO-RE relocation>\n"
          "failed to resolve CO-RE relocation %s%s\n",
          insn_idx, spec_buf, spec_len >= sizeof(spec_buf) ? "..." : "");
 
     patch_log(buf, buf_sz, log_sz, line1, line3 - line1, patch);
 }
 
 static void fixup_log_missing_map_load(struct bpf_program *prog,
                        char *buf, size_t buf_sz, size_t log_sz,
                        char *line1, char *line2, char *line3)
 {
     /* Expected log for failed and not properly guarded CO-RE relocation:
      * line1 -> 123: (85) call unknown#2001000345
      * line2 -> invalid func unknown#2001000345
      * line3 -> <anything else or end of buffer>
      *
      * "123" is the index of the instruction that was poisoned.
      * "345" in "2001000345" are map index in obj->maps to fetch map name.
      */
     struct bpf_object *obj = prog->obj;
     const struct bpf_map *map;
     int insn_idx, map_idx;
     char patch[128];
 
     if (sscanf(line1, "%d: (%*d) call unknown#%d\n", &insn_idx, &map_idx) != 2)
         return;
 
     map_idx -= MAP_LDIMM64_POISON_BASE;
     if (map_idx < 0 || map_idx >= obj->nr_maps)
         return;
     map = &obj->maps[map_idx];
 
     snprintf(patch, sizeof(patch),
          "%d: <invalid BPF map reference>\n"
          "BPF map '%s' is referenced but wasn't created\n",
          insn_idx, map->name);
 
     patch_log(buf, buf_sz, log_sz, line1, line3 - line1, patch);
 }
 
 static void fixup_verifier_log(struct bpf_program *prog, char *buf, size_t buf_sz)
 {
     /* look for familiar error patterns in last N lines of the log */
     const size_t max_last_line_cnt = 10;
     char *prev_line, *cur_line, *next_line;
     size_t log_sz;
     int i;
 
     if (!buf)
         return;
 
     log_sz = strlen(buf) + 1;
     next_line = buf + log_sz - 1;
 
     for (i = 0; i < max_last_line_cnt; i++, next_line = cur_line) {
         cur_line = find_prev_line(buf, next_line);
         if (!cur_line)
             return;
 
         /* failed CO-RE relocation case */
         if (str_has_pfx(cur_line, "invalid func unknown#195896080\n")) {
             prev_line = find_prev_line(buf, cur_line);
             if (!prev_line)
                 continue;
 
             fixup_log_failed_core_relo(prog, buf, buf_sz, log_sz,
                            prev_line, cur_line, next_line);
             return;
         } else if (str_has_pfx(cur_line, "invalid func unknown#"MAP_LDIMM64_POISON_PFX)) {
             prev_line = find_prev_line(buf, cur_line);
             if (!prev_line)
                 continue;
 
             fixup_log_missing_map_load(prog, buf, buf_sz, log_sz,
                            prev_line, cur_line, next_line);
             return;
         }
     }
 }
 
 static int bpf_program_record_relos(struct bpf_program *prog)
 {
     struct bpf_object *obj = prog->obj;
     int i;
 
     for (i = 0; i < prog->nr_reloc; i++) {
         struct reloc_desc *relo = &prog->reloc_desc[i];
         struct extern_desc *ext = &obj->externs[relo->sym_off];
 
         switch (relo->type) {
         case RELO_EXTERN_VAR:
             if (ext->type != EXT_KSYM)
                 continue;
             bpf_gen__record_extern(obj->gen_loader, ext->name,
                            ext->is_weak, !ext->ksym.type_id,
                            BTF_KIND_VAR, relo->insn_idx);
             break;
         case RELO_EXTERN_FUNC:
             bpf_gen__record_extern(obj->gen_loader, ext->name,
                            ext->is_weak, false, BTF_KIND_FUNC,
                            relo->insn_idx);
             break;
         case RELO_CORE: {
             struct bpf_core_relo cr = {
                 .insn_off = relo->insn_idx * 8,
                 .type_id = relo->core_relo->type_id,
                 .access_str_off = relo->core_relo->access_str_off,
                 .kind = relo->core_relo->kind,
             };
 
             bpf_gen__record_relo_core(obj->gen_loader, &cr);
             break;
         }
         default:
             continue;
         }
     }
     return 0;
 }
 
 static int
 bpf_object__load_progs(struct bpf_object *obj, int log_level)
 {
     struct bpf_program *prog;
     size_t i;
     int err;
 
     for (i = 0; i < obj->nr_programs; i++) {
         prog = &obj->programs[i];
         err = bpf_object__sanitize_prog(obj, prog);
         if (err)
             return err;
     }
 
     for (i = 0; i < obj->nr_programs; i++) {
         prog = &obj->programs[i];
         if (prog_is_subprog(obj, prog))
             continue;
         if (!prog->autoload) {
             pr_debug("prog '%s': skipped loading\n", prog->name);
             continue;
         }
         prog->log_level |= log_level;
 
         if (obj->gen_loader)
             bpf_program_record_relos(prog);
 
         err = bpf_object_load_prog(obj, prog, prog->insns, prog->insns_cnt,
                        obj->license, obj->kern_version, &prog->fd);
         if (err) {
             pr_warn("prog '%s': failed to load: %d\n", prog->name, err);
             return err;
         }
     }
 
     bpf_object__free_relocs(obj);
     return 0;
 }
 
 static const struct bpf_sec_def *find_sec_def(const char *sec_name);
 
 static int bpf_object_init_progs(struct bpf_object *obj, const struct bpf_object_open_opts *opts)
 {
     struct bpf_program *prog;
     int err;
 
     bpf_object__for_each_program(prog, obj) {
         prog->sec_def = find_sec_def(prog->sec_name);
         if (!prog->sec_def) {
             /* couldn't guess, but user might manually specify */
             pr_debug("prog '%s': unrecognized ELF section name '%s'\n",
                 prog->name, prog->sec_name);
             continue;
         }
 
         prog->type = prog->sec_def->prog_type;
         prog->expected_attach_type = prog->sec_def->expected_attach_type;
 
         /* sec_def can have custom callback which should be called
          * after bpf_program is initialized to adjust its properties
          */
         if (prog->sec_def->prog_setup_fn) {
             err = prog->sec_def->prog_setup_fn(prog, prog->sec_def->cookie);
             if (err < 0) {
                 pr_warn("prog '%s': failed to initialize: %d\n",
                     prog->name, err);
                 return err;
             }
         }
     }
 
     return 0;
 }
 
 static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf, size_t obj_buf_sz,
                       const struct bpf_object_open_opts *opts)
 {
     const char *obj_name, *kconfig, *btf_tmp_path;
     struct bpf_object *obj;
     char tmp_name[64];
     int err;
     char *log_buf;
     size_t log_size;
     __u32 log_level;
 
     if (elf_version(EV_CURRENT) == EV_NONE) {
         pr_warn("failed to init libelf for %s\n",
             path ? : "(mem buf)");
         return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
     }
 
     if (!OPTS_VALID(opts, bpf_object_open_opts))
         return ERR_PTR(-EINVAL);
 
     obj_name = OPTS_GET(opts, object_name, NULL);
     if (obj_buf) {
         if (!obj_name) {
             snprintf(tmp_name, sizeof(tmp_name), "%lx-%lx",
                  (unsigned long)obj_buf,
                  (unsigned long)obj_buf_sz);
             obj_name = tmp_name;
         }
         path = obj_name;
         pr_debug("loading object '%s' from buffer\n", obj_name);
     }
 
     log_buf = OPTS_GET(opts, kernel_log_buf, NULL);
     log_size = OPTS_GET(opts, kernel_log_size, 0);
     log_level = OPTS_GET(opts, kernel_log_level, 0);
     if (log_size > UINT_MAX)
         return ERR_PTR(-EINVAL);
     if (log_size && !log_buf)
         return ERR_PTR(-EINVAL);
 
     obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name);
     if (IS_ERR(obj))
         return obj;
 
     obj->log_buf = log_buf;
     obj->log_size = log_size;
     obj->log_level = log_level;
 
     btf_tmp_path = OPTS_GET(opts, btf_custom_path, NULL);
     if (btf_tmp_path) {
         if (strlen(btf_tmp_path) >= PATH_MAX) {
             err = -ENAMETOOLONG;
             goto out;
         }
         obj->btf_custom_path = strdup(btf_tmp_path);
         if (!obj->btf_custom_path) {
             err = -ENOMEM;
             goto out;
         }
     }
 
     kconfig = OPTS_GET(opts, kconfig, NULL);
     if (kconfig) {
         obj->kconfig = strdup(kconfig);
         if (!obj->kconfig) {
             err = -ENOMEM;
             goto out;
         }
     }
 
     err = bpf_object__elf_init(obj);
     err = err ? : bpf_object__check_endianness(obj);
     err = err ? : bpf_object__elf_collect(obj);
     err = err ? : bpf_object__collect_externs(obj);
     err = err ? : bpf_object__finalize_btf(obj);
     err = err ? : bpf_object__init_maps(obj, opts);
     err = err ? : bpf_object_init_progs(obj, opts);
     err = err ? : bpf_object__collect_relos(obj);
     if (err)
         goto out;
 
     bpf_object__elf_finish(obj);
 
     return obj;
 out:
     bpf_object__close(obj);
     return ERR_PTR(err);
 }
 
 struct bpf_object *
 bpf_object__open_file(const char *path, const struct bpf_object_open_opts *opts)
 {
     if (!path)
         return libbpf_err_ptr(-EINVAL);
 
     pr_debug("loading %s\n", path);
 
     return libbpf_ptr(bpf_object_open(path, NULL, 0, opts));
 }
 
 struct bpf_object *bpf_object__open(const char *path)
 {
     return bpf_object__open_file(path, NULL);
 }
 
 struct bpf_object *
 bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
              const struct bpf_object_open_opts *opts)
 {
     if (!obj_buf || obj_buf_sz == 0)
         return libbpf_err_ptr(-EINVAL);
 
     return libbpf_ptr(bpf_object_open(NULL, obj_buf, obj_buf_sz, opts));
 }
 
 static int bpf_object_unload(struct bpf_object *obj)
 {
     size_t i;
 
     if (!obj)
         return libbpf_err(-EINVAL);
 
     for (i = 0; i < obj->nr_maps; i++) {
         zclose(obj->maps[i].fd);
         if (obj->maps[i].st_ops)
             zfree(&obj->maps[i].st_ops->kern_vdata);
     }
 
     for (i = 0; i < obj->nr_programs; i++)
         bpf_program__unload(&obj->programs[i]);
 
     return 0;
 }
 
 int bpf_object__unload(struct bpf_object *obj) __attribute__((alias("bpf_object_unload")));
 
 static int bpf_object__sanitize_maps(struct bpf_object *obj)
 {
     struct bpf_map *m;
 
     bpf_object__for_each_map(m, obj) {
         if (!bpf_map__is_internal(m))
             continue;
         if (!kernel_supports(obj, FEAT_ARRAY_MMAP))
             m->def.map_flags ^= BPF_F_MMAPABLE;
     }
 
     return 0;
 }
 
 int libbpf_kallsyms_parse(kallsyms_cb_t cb, void *ctx)
 {
     char sym_type, sym_name[500];
     unsigned long long sym_addr;
     int ret, err = 0;
     FILE *f;
 
     f = fopen("/proc/kallsyms", "r");
     if (!f) {
         err = -errno;
         pr_warn("failed to open /proc/kallsyms: %d\n", err);
         return err;
     }
 
     while (true) {
         ret = fscanf(f, "%llx %c %499s%*[^\n]\n",
                  &sym_addr, &sym_type, sym_name);
         if (ret == EOF && feof(f))
             break;
         if (ret != 3) {
             pr_warn("failed to read kallsyms entry: %d\n", ret);
             err = -EINVAL;
             break;
         }
 
         err = cb(sym_addr, sym_type, sym_name, ctx);
         if (err)
             break;
     }
 
     fclose(f);
     return err;
 }
 
 static int kallsyms_cb(unsigned long long sym_addr, char sym_type,
                const char *sym_name, void *ctx)
 {
     struct bpf_object *obj = ctx;
     const struct btf_type *t;
     struct extern_desc *ext;
 
     ext = find_extern_by_name(obj, sym_name);
     if (!ext || ext->type != EXT_KSYM)
         return 0;
 
     t = btf__type_by_id(obj->btf, ext->btf_id);
     if (!btf_is_var(t))
         return 0;
 
     if (ext->is_set && ext->ksym.addr != sym_addr) {
         pr_warn("extern (ksym) '%s': resolution is ambiguous: 0x%llx or 0x%llx\n",
             sym_name, ext->ksym.addr, sym_addr);
         return -EINVAL;
     }
     if (!ext->is_set) {
         ext->is_set = true;
         ext->ksym.addr = sym_addr;
         pr_debug("extern (ksym) '%s': set to 0x%llx\n", sym_name, sym_addr);
     }
     return 0;
 }
 
 static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
 {
     return libbpf_kallsyms_parse(kallsyms_cb, obj);
 }
 
 static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
                 __u16 kind, struct btf **res_btf,
                 struct module_btf **res_mod_btf)
 {
     struct module_btf *mod_btf;
     struct btf *btf;
     int i, id, err;
 
     btf = obj->btf_vmlinux;
     mod_btf = NULL;
     id = btf__find_by_name_kind(btf, ksym_name, kind);
 
     if (id == -ENOENT) {
         err = load_module_btfs(obj);
         if (err)
             return err;
 
         for (i = 0; i < obj->btf_module_cnt; i++) {
             /* we assume module_btf's BTF FD is always >0 */
             mod_btf = &obj->btf_modules[i];
             btf = mod_btf->btf;
             id = btf__find_by_name_kind_own(btf, ksym_name, kind);
             if (id != -ENOENT)
                 break;
         }
     }
     if (id <= 0)
         return -ESRCH;
 
     *res_btf = btf;
     *res_mod_btf = mod_btf;
     return id;
 }
 
 static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
                            struct extern_desc *ext)
 {
     const struct btf_type *targ_var, *targ_type;
     __u32 targ_type_id, local_type_id;
     struct module_btf *mod_btf = NULL;
     const char *targ_var_name;
     struct btf *btf = NULL;
     int id, err;
 
     id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &mod_btf);
     if (id < 0) {
         if (id == -ESRCH && ext->is_weak)
             return 0;
         pr_warn("extern (var ksym) '%s': not found in kernel BTF\n",
             ext->name);
         return id;
     }
 
     /* find local type_id */
     local_type_id = ext->ksym.type_id;
 
     /* find target type_id */
     targ_var = btf__type_by_id(btf, id);
     targ_var_name = btf__name_by_offset(btf, targ_var->name_off);
     targ_type = skip_mods_and_typedefs(btf, targ_var->type, &targ_type_id);
 
     err = bpf_core_types_are_compat(obj->btf, local_type_id,
                     btf, targ_type_id);
     if (err <= 0) {
         const struct btf_type *local_type;
         const char *targ_name, *local_name;
 
         local_type = btf__type_by_id(obj->btf, local_type_id);
         local_name = btf__name_by_offset(obj->btf, local_type->name_off);
         targ_name = btf__name_by_offset(btf, targ_type->name_off);
 
         pr_warn("extern (var ksym) '%s': incompatible types, expected [%d] %s %s, but kernel has [%d] %s %s\n",
             ext->name, local_type_id,
             btf_kind_str(local_type), local_name, targ_type_id,
             btf_kind_str(targ_type), targ_name);
         return -EINVAL;
     }
 
     ext->is_set = true;
     ext->ksym.kernel_btf_obj_fd = mod_btf ? mod_btf->fd : 0;
     ext->ksym.kernel_btf_id = id;
     pr_debug("extern (var ksym) '%s': resolved to [%d] %s %s\n",
          ext->name, id, btf_kind_str(targ_var), targ_var_name);
 
     return 0;
 }
 
 static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
                         struct extern_desc *ext)
 {
     int local_func_proto_id, kfunc_proto_id, kfunc_id;
     struct module_btf *mod_btf = NULL;
     const struct btf_type *kern_func;
     struct btf *kern_btf = NULL;
     int ret;
 
     local_func_proto_id = ext->ksym.type_id;
 
     kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, &kern_btf, &mod_btf);
     if (kfunc_id < 0) {
         if (kfunc_id == -ESRCH && ext->is_weak)
             return 0;
         pr_warn("extern (func ksym) '%s': not found in kernel or module BTFs\n",
             ext->name);
         return kfunc_id;
     }
 
     kern_func = btf__type_by_id(kern_btf, kfunc_id);
     kfunc_proto_id = kern_func->type;
 
     ret = bpf_core_types_are_compat(obj->btf, local_func_proto_id,
                     kern_btf, kfunc_proto_id);
     if (ret <= 0) {
         pr_warn("extern (func ksym) '%s': func_proto [%d] incompatible with kernel [%d]\n",
             ext->name, local_func_proto_id, kfunc_proto_id);
         return -EINVAL;
     }
 
     /* set index for module BTF fd in fd_array, if unset */
     if (mod_btf && !mod_btf->fd_array_idx) {
         /* insn->off is s16 */
         if (obj->fd_array_cnt == INT16_MAX) {
             pr_warn("extern (func ksym) '%s': module BTF fd index %d too big to fit in bpf_insn offset\n",
                 ext->name, mod_btf->fd_array_idx);
             return -E2BIG;
         }
         /* Cannot use index 0 for module BTF fd */
         if (!obj->fd_array_cnt)
             obj->fd_array_cnt = 1;
 
         ret = libbpf_ensure_mem((void **)&obj->fd_array, &obj->fd_array_cap, sizeof(int),
                     obj->fd_array_cnt + 1);
         if (ret)
             return ret;
         mod_btf->fd_array_idx = obj->fd_array_cnt;
         /* we assume module BTF FD is always >0 */
         obj->fd_array[obj->fd_array_cnt++] = mod_btf->fd;
     }
 
     ext->is_set = true;
     ext->ksym.kernel_btf_id = kfunc_id;
     ext->ksym.btf_fd_idx = mod_btf ? mod_btf->fd_array_idx : 0;
     pr_debug("extern (func ksym) '%s': resolved to kernel [%d]\n",
          ext->name, kfunc_id);
 
     return 0;
 }
 
 static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
 {
     const struct btf_type *t;
     struct extern_desc *ext;
     int i, err;
 
     for (i = 0; i < obj->nr_extern; i++) {
         ext = &obj->externs[i];
         if (ext->type != EXT_KSYM || !ext->ksym.type_id)
             continue;
 
         if (obj->gen_loader) {
             ext->is_set = true;
             ext->ksym.kernel_btf_obj_fd = 0;
             ext->ksym.kernel_btf_id = 0;
             continue;
         }
         t = btf__type_by_id(obj->btf, ext->btf_id);
         if (btf_is_var(t))
             err = bpf_object__resolve_ksym_var_btf_id(obj, ext);
         else
             err = bpf_object__resolve_ksym_func_btf_id(obj, ext);
         if (err)
             return err;
     }
     return 0;
 }
 
 static int bpf_object__resolve_externs(struct bpf_object *obj,
                        const char *extra_kconfig)
 {
     bool need_config = false, need_kallsyms = false;
     bool need_vmlinux_btf = false;
     struct extern_desc *ext;
     void *kcfg_data = NULL;
     int err, i;
 
     if (obj->nr_extern == 0)
         return 0;
 
     if (obj->kconfig_map_idx >= 0)
         kcfg_data = obj->maps[obj->kconfig_map_idx].mmaped;
 
     for (i = 0; i < obj->nr_extern; i++) {
         ext = &obj->externs[i];
 
         if (ext->type == EXT_KSYM) {
             if (ext->ksym.type_id)
                 need_vmlinux_btf = true;
             else
                 need_kallsyms = true;
             continue;
         } else if (ext->type == EXT_KCFG) {
             void *ext_ptr = kcfg_data + ext->kcfg.data_off;
             __u64 value = 0;
 
             /* Kconfig externs need actual /proc/config.gz */
             if (str_has_pfx(ext->name, "CONFIG_")) {
                 need_config = true;
                 continue;
             }
 
             /* Virtual kcfg externs are customly handled by libbpf */
             if (strcmp(ext->name, "LINUX_KERNEL_VERSION") == 0) {
                 value = get_kernel_version();
                 if (!value) {
                     pr_warn("extern (kcfg) '%s': failed to get kernel version\n", ext->name);
                     return -EINVAL;
                 }
             } else if (strcmp(ext->name, "LINUX_HAS_BPF_COOKIE") == 0) {
                 value = kernel_supports(obj, FEAT_BPF_COOKIE);
             } else if (strcmp(ext->name, "LINUX_HAS_SYSCALL_WRAPPER") == 0) {
                 value = kernel_supports(obj, FEAT_SYSCALL_WRAPPER);
             } else if (!str_has_pfx(ext->name, "LINUX_") || !ext->is_weak) {
                 /* Currently libbpf supports only CONFIG_ and LINUX_ prefixed
                  * __kconfig externs, where LINUX_ ones are virtual and filled out
                  * customly by libbpf (their values don't come from Kconfig).
                  * If LINUX_xxx variable is not recognized by libbpf, but is marked
                  * __weak, it defaults to zero value, just like for CONFIG_xxx
                  * externs.
                  */
                 pr_warn("extern (kcfg) '%s': unrecognized virtual extern\n", ext->name);
                 return -EINVAL;
             }
 
             err = set_kcfg_value_num(ext, ext_ptr, value);
             if (err)
                 return err;
             pr_debug("extern (kcfg) '%s': set to 0x%llx\n",
                  ext->name, (long long)value);
         } else {
             pr_warn("extern '%s': unrecognized extern kind\n", ext->name);
             return -EINVAL;
         }
     }
     if (need_config && extra_kconfig) {
         err = bpf_object__read_kconfig_mem(obj, extra_kconfig, kcfg_data);
         if (err)
             return -EINVAL;
         need_config = false;
         for (i = 0; i < obj->nr_extern; i++) {
             ext = &obj->externs[i];
             if (ext->type == EXT_KCFG && !ext->is_set) {
                 need_config = true;
                 break;
             }
         }
     }
     if (need_config) {
         err = bpf_object__read_kconfig_file(obj, kcfg_data);
         if (err)
             return -EINVAL;
     }
     if (need_kallsyms) {
         err = bpf_object__read_kallsyms_file(obj);
         if (err)
             return -EINVAL;
     }
     if (need_vmlinux_btf) {
         err = bpf_object__resolve_ksyms_btf_id(obj);
         if (err)
             return -EINVAL;
     }
     for (i = 0; i < obj->nr_extern; i++) {
         ext = &obj->externs[i];
 
         if (!ext->is_set && !ext->is_weak) {
             pr_warn("extern '%s' (strong): not resolved\n", ext->name);
             return -ESRCH;
         } else if (!ext->is_set) {
             pr_debug("extern '%s' (weak): not resolved, defaulting to zero\n",
                  ext->name);
         }
     }
 
     return 0;
 }
 
 static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path)
 {
     int err, i;
 
     if (!obj)
         return libbpf_err(-EINVAL);
 
     if (obj->loaded) {
         pr_warn("object '%s': load can't be attempted twice\n", obj->name);
         return libbpf_err(-EINVAL);
     }
 
     if (obj->gen_loader)
         bpf_gen__init(obj->gen_loader, extra_log_level, obj->nr_programs, obj->nr_maps);
 
     err = bpf_object__probe_loading(obj);
     err = err ? : bpf_object__load_vmlinux_btf(obj, false);
     err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
     err = err ? : bpf_object__sanitize_and_load_btf(obj);
     err = err ? : bpf_object__sanitize_maps(obj);
     err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
     err = err ? : bpf_object__create_maps(obj);
     err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : target_btf_path);
     err = err ? : bpf_object__load_progs(obj, extra_log_level);
     err = err ? : bpf_object_init_prog_arrays(obj);
 
     if (obj->gen_loader) {
         /* reset FDs */
         if (obj->btf)
             btf__set_fd(obj->btf, -1);
         for (i = 0; i < obj->nr_maps; i++)
             obj->maps[i].fd = -1;
         if (!err)
             err = bpf_gen__finish(obj->gen_loader, obj->nr_programs, obj->nr_maps);
     }
 
     /* clean up fd_array */
     zfree(&obj->fd_array);
 
     /* clean up module BTFs */
     for (i = 0; i < obj->btf_module_cnt; i++) {
         close(obj->btf_modules[i].fd);
         btf__free(obj->btf_modules[i].btf);
         free(obj->btf_modules[i].name);
     }
     free(obj->btf_modules);
 
     /* clean up vmlinux BTF */
     btf__free(obj->btf_vmlinux);
     obj->btf_vmlinux = NULL;
 
     obj->loaded = true; /* doesn't matter if successfully or not */
 
     if (err)
         goto out;
 
     return 0;
 out:
     /* unpin any maps that were auto-pinned during load */
     for (i = 0; i < obj->nr_maps; i++)
         if (obj->maps[i].pinned && !obj->maps[i].reused)
             bpf_map__unpin(&obj->maps[i], NULL);
 
     bpf_object_unload(obj);
     pr_warn("failed to load object '%s'\n", obj->path);
     return libbpf_err(err);
 }
 
 int bpf_object__load(struct bpf_object *obj)
 {
     return bpf_object_load(obj, 0, NULL);
 }
 
 static int make_parent_dir(const char *path)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     char *dname, *dir;
     int err = 0;
 
     dname = strdup(path);
     if (dname == NULL)
         return -ENOMEM;
 
     dir = dirname(dname);
     if (mkdir(dir, 0700) && errno != EEXIST)
         err = -errno;
 
     free(dname);
     if (err) {
         cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
         pr_warn("failed to mkdir %s: %s\n", path, cp);
     }
     return err;
 }
 
 static int check_path(const char *path)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     struct statfs st_fs;
     char *dname, *dir;
     int err = 0;
 
     if (path == NULL)
         return -EINVAL;
 
     dname = strdup(path);
     if (dname == NULL)
         return -ENOMEM;
 
     dir = dirname(dname);
     if (statfs(dir, &st_fs)) {
         cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
         pr_warn("failed to statfs %s: %s\n", dir, cp);
         err = -errno;
     }
     free(dname);
 
     if (!err && st_fs.f_type != BPF_FS_MAGIC) {
         pr_warn("specified path %s is not on BPF FS\n", path);
         err = -EINVAL;
     }
 
     return err;
 }
 
 int bpf_program__pin(struct bpf_program *prog, const char *path)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     int err;
 
     if (prog->fd < 0) {
         pr_warn("prog '%s': can't pin program that wasn't loaded\n", prog->name);
         return libbpf_err(-EINVAL);
     }
 
     err = make_parent_dir(path);
     if (err)
         return libbpf_err(err);
 
     err = check_path(path);
     if (err)
         return libbpf_err(err);
 
     if (bpf_obj_pin(prog->fd, path)) {
         err = -errno;
         cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
         pr_warn("prog '%s': failed to pin at '%s': %s\n", prog->name, path, cp);
         return libbpf_err(err);
     }
 
     pr_debug("prog '%s': pinned at '%s'\n", prog->name, path);
     return 0;
 }
 
 int bpf_program__unpin(struct bpf_program *prog, const char *path)
 {
     int err;
 
     if (prog->fd < 0) {
         pr_warn("prog '%s': can't unpin program that wasn't loaded\n", prog->name);
         return libbpf_err(-EINVAL);
     }
 
     err = check_path(path);
     if (err)
         return libbpf_err(err);
 
     err = unlink(path);
     if (err)
         return libbpf_err(-errno);
 
     pr_debug("prog '%s': unpinned from '%s'\n", prog->name, path);
     return 0;
 }
 
 int bpf_map__pin(struct bpf_map *map, const char *path)
 {
     char *cp, errmsg[STRERR_BUFSIZE];
     int err;
 
     if (map == NULL) {
         pr_warn("invalid map pointer\n");
         return libbpf_err(-EINVAL);
     }
 
     if (map->pin_path) {
         if (path && strcmp(path, map->pin_path)) {
             pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
                 bpf_map__name(map), map->pin_path, path);
             return libbpf_err(-EINVAL);
         } else if (map->pinned) {
             pr_debug("map '%s' already pinned at '%s'; not re-pinning\n",
                  bpf_map__name(map), map->pin_path);
             return 0;
         }
     } else {
         if (!path) {
             pr_warn("missing a path to pin map '%s' at\n",
                 bpf_map__name(map));
             return libbpf_err(-EINVAL);
         } else if (map->pinned) {
             pr_warn("map '%s' already pinned\n", bpf_map__name(map));
             return libbpf_err(-EEXIST);
         }
 
         map->pin_path = strdup(path);
         if (!map->pin_path) {
             err = -errno;
             goto out_err;
         }
     }
 
     err = make_parent_dir(map->pin_path);
     if (err)
         return libbpf_err(err);
 
     err = check_path(map->pin_path);
     if (err)
         return libbpf_err(err);
 
     if (bpf_obj_pin(map->fd, map->pin_path)) {
         err = -errno;
         goto out_err;
     }
 
     map->pinned = true;
     pr_debug("pinned map '%s'\n", map->pin_path);
 
     return 0;
 
 out_err:
     cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
     pr_warn("failed to pin map: %s\n", cp);
     return libbpf_err(err);
 }
 
 int bpf_map__unpin(struct bpf_map *map, const char *path)
 {
     int err;
 
     if (map == NULL) {
         pr_warn("invalid map pointer\n");
         return libbpf_err(-EINVAL);
     }
 
     if (map->pin_path) {
         if (path && strcmp(path, map->pin_path)) {
             pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
                 bpf_map__name(map), map->pin_path, path);
             return libbpf_err(-EINVAL);
         }
         path = map->pin_path;
     } else if (!path) {
         pr_warn("no path to unpin map '%s' from\n",
             bpf_map__name(map));
         return libbpf_err(-EINVAL);
     }
 
     err = check_path(path);
     if (err)
         return libbpf_err(err);
 
     err = unlink(path);
     if (err != 0)
         return libbpf_err(-errno);
 
     map->pinned = false;
     pr_debug("unpinned map '%s' from '%s'\n", bpf_map__name(map), path);
 
     return 0;
 }
 
 int bpf_map__set_pin_path(struct bpf_map *map, const char *path)
 {
     char *new = NULL;
 
     if (path) {
         new = strdup(path);
         if (!new)
             return libbpf_err(-errno);
     }
 
     free(map->pin_path);
     map->pin_path = new;
     return 0;
 }
 
 __alias(bpf_map__pin_path)
 const char *bpf_map__get_pin_path(const struct bpf_map *map);
 
 const char *bpf_map__pin_path(const struct bpf_map *map)
 {
     return map->pin_path;
 }
 
 bool bpf_map__is_pinned(const struct bpf_map *map)
 {
     return map->pinned;
 }
 
 static void sanitize_pin_path(char *s)
 {
     /* bpffs disallows periods in path names */
     while (*s) {
         if (*s == '.')
             *s = '_';
         s++;
     }
 }
 
 int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
 {
     struct bpf_map *map;
     int err;
 
     if (!obj)
         return libbpf_err(-ENOENT);
 
     if (!obj->loaded) {
         pr_warn("object not yet loaded; load it first\n");
         return libbpf_err(-ENOENT);
     }
 
     bpf_object__for_each_map(map, obj) {
         char *pin_path = NULL;
         char buf[PATH_MAX];
 
         if (!map->autocreate)
             continue;
 
         if (path) {
             int len;
 
             len = snprintf(buf, PATH_MAX, "%s/%s", path,
                        bpf_map__name(map));
             if (len < 0) {
                 err = -EINVAL;
                 goto err_unpin_maps;
             } else if (len >= PATH_MAX) {
                 err = -ENAMETOOLONG;
                 goto err_unpin_maps;
             }
             sanitize_pin_path(buf);
             pin_path = buf;
         } else if (!map->pin_path) {
             continue;
         }
 
         err = bpf_map__pin(map, pin_path);
         if (err)
             goto err_unpin_maps;
     }
 
     return 0;
 
 err_unpin_maps:
     while ((map = bpf_object__prev_map(obj, map))) {
         if (!map->pin_path)
             continue;
 
         bpf_map__unpin(map, NULL);
     }
 
     return libbpf_err(err);
 }
 
 int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
 {
     struct bpf_map *map;
     int err;
 
     if (!obj)
         return libbpf_err(-ENOENT);
 
     bpf_object__for_each_map(map, obj) {
         char *pin_path = NULL;
         char buf[PATH_MAX];
 
         if (path) {
             int len;
 
             len = snprintf(buf, PATH_MAX, "%s/%s", path,
                        bpf_map__name(map));
             if (len < 0)
                 return libbpf_err(-EINVAL);
             else if (len >= PATH_MAX)
                 return libbpf_err(-ENAMETOOLONG);
             sanitize_pin_path(buf);
             pin_path = buf;
         } else if (!map->pin_path) {
             continue;
         }
 
         err = bpf_map__unpin(map, pin_path);
         if (err)
             return libbpf_err(err);
     }
 
     return 0;
 }
 
 int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 {
     struct bpf_program *prog;
     int err;
 
     if (!obj)
         return libbpf_err(-ENOENT);
 
     if (!obj->loaded) {
         pr_warn("object not yet loaded; load it first\n");
         return libbpf_err(-ENOENT);
     }
 
     bpf_object__for_each_program(prog, obj) {
         char buf[PATH_MAX];
         int len;
 
         len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
         if (len < 0) {
             err = -EINVAL;
             goto err_unpin_programs;
         } else if (len >= PATH_MAX) {
             err = -ENAMETOOLONG;
             goto err_unpin_programs;
         }
 
         err = bpf_program__pin(prog, buf);
         if (err)
             goto err_unpin_programs;
     }
 
     return 0;
 
 err_unpin_programs:
     while ((prog = bpf_object__prev_program(obj, prog))) {
         char buf[PATH_MAX];
         int len;
 
         len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
         if (len < 0)
             continue;
         else if (len >= PATH_MAX)
             continue;
 
         bpf_program__unpin(prog, buf);
     }
 
     return libbpf_err(err);
 }
 
 int bpf_object__unpin_programs(struct bpf_object *obj, const char *path)
 {
     struct bpf_program *prog;
     int err;
 
     if (!obj)
         return libbpf_err(-ENOENT);
 
     bpf_object__for_each_program(prog, obj) {
         char buf[PATH_MAX];
         int len;
 
         len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
         if (len < 0)
             return libbpf_err(-EINVAL);
         else if (len >= PATH_MAX)
             return libbpf_err(-ENAMETOOLONG);
 
         err = bpf_program__unpin(prog, buf);
         if (err)
             return libbpf_err(err);
     }
 
     return 0;
 }
 
 int bpf_object__pin(struct bpf_object *obj, const char *path)
 {
     int err;
 
     err = bpf_object__pin_maps(obj, path);
     if (err)
         return libbpf_err(err);
 
     err = bpf_object__pin_programs(obj, path);
     if (err) {
         bpf_object__unpin_maps(obj, path);
         return libbpf_err(err);
     }
 
     return 0;
 }
 
 static void bpf_map__destroy(struct bpf_map *map)
 {
     if (map->inner_map) {
         bpf_map__destroy(map->inner_map);
         zfree(&map->inner_map);
     }
 
     zfree(&map->init_slots);
     map->init_slots_sz = 0;
 
     if (map->mmaped) {
         munmap(map->mmaped, bpf_map_mmap_sz(map));
         map->mmaped = NULL;
     }
 
     if (map->st_ops) {
         zfree(&map->st_ops->data);
         zfree(&map->st_ops->progs);
         zfree(&map->st_ops->kern_func_off);
         zfree(&map->st_ops);
     }
 
     zfree(&map->name);
     zfree(&map->real_name);
     zfree(&map->pin_path);
 
     if (map->fd >= 0)
         zclose(map->fd);
 }
 
 void bpf_object__close(struct bpf_object *obj)
 {
     size_t i;
 
     if (IS_ERR_OR_NULL(obj))
         return;
 
     usdt_manager_free(obj->usdt_man);
     obj->usdt_man = NULL;
 
     bpf_gen__free(obj->gen_loader);
     bpf_object__elf_finish(obj);
     bpf_object_unload(obj);
     btf__free(obj->btf);
     btf_ext__free(obj->btf_ext);
 
     for (i = 0; i < obj->nr_maps; i++)
         bpf_map__destroy(&obj->maps[i]);
 
     zfree(&obj->btf_custom_path);
     zfree(&obj->kconfig);
     zfree(&obj->externs);
     obj->nr_extern = 0;
 
     zfree(&obj->maps);
     obj->nr_maps = 0;
 
     if (obj->programs && obj->nr_programs) {
         for (i = 0; i < obj->nr_programs; i++)
             bpf_program__exit(&obj->programs[i]);
     }
     zfree(&obj->programs);
 
     free(obj);
 }
 
 const char *bpf_object__name(const struct bpf_object *obj)
 {
     return obj ? obj->name : libbpf_err_ptr(-EINVAL);
 }
 
 unsigned int bpf_object__kversion(const struct bpf_object *obj)
 {
     return obj ? obj->kern_version : 0;
 }
 
 struct btf *bpf_object__btf(const struct bpf_object *obj)
 {
     return obj ? obj->btf : NULL;
 }
 
 int bpf_object__btf_fd(const struct bpf_object *obj)
 {
     return obj->btf ? btf__fd(obj->btf) : -1;
 }
 
 int bpf_object__set_kversion(struct bpf_object *obj, __u32 kern_version)
 {
     if (obj->loaded)
         return libbpf_err(-EINVAL);
 
     obj->kern_version = kern_version;
 
     return 0;
 }
 
 int bpf_object__gen_loader(struct bpf_object *obj, struct gen_loader_opts *opts)
 {
     struct bpf_gen *gen;
 
     if (!opts)
         return -EFAULT;
     if (!OPTS_VALID(opts, gen_loader_opts))
         return -EINVAL;
     gen = calloc(sizeof(*gen), 1);
     if (!gen)
         return -ENOMEM;
     gen->opts = opts;
     obj->gen_loader = gen;
     return 0;
 }
 
 static struct bpf_program *
 __bpf_program__iter(const struct bpf_program *p, const struct bpf_object *obj,
             bool forward)
 {
     size_t nr_programs = obj->nr_programs;
     ssize_t idx;
 
     if (!nr_programs)
         return NULL;
 
     if (!p)
         /* Iter from the beginning */
         return forward ? &obj->programs[0] :
             &obj->programs[nr_programs - 1];
 
     if (p->obj != obj) {
         pr_warn("error: program handler doesn't match object\n");
         return errno = EINVAL, NULL;
     }
 
     idx = (p - obj->programs) + (forward ? 1 : -1);
     if (idx >= obj->nr_programs || idx < 0)
         return NULL;
     return &obj->programs[idx];
 }
 
 struct bpf_program *
 bpf_object__next_program(const struct bpf_object *obj, struct bpf_program *prev)
 {
     struct bpf_program *prog = prev;
 
     do {
         prog = __bpf_program__iter(prog, obj, true);
     } while (prog && prog_is_subprog(obj, prog));
 
     return prog;
 }
 
 struct bpf_program *
 bpf_object__prev_program(const struct bpf_object *obj, struct bpf_program *next)
 {
     struct bpf_program *prog = next;
 
     do {
         prog = __bpf_program__iter(prog, obj, false);
     } while (prog && prog_is_subprog(obj, prog));
 
     return prog;
 }
 
 void bpf_program__set_ifindex(struct bpf_program *prog, __u32 ifindex)
 {
     prog->prog_ifindex = ifindex;
 }
 
 const char *bpf_program__name(const struct bpf_program *prog)
 {
     return prog->name;
 }
 
 const char *bpf_program__section_name(const struct bpf_program *prog)
 {
     return prog->sec_name;
 }
 
 bool bpf_program__autoload(const struct bpf_program *prog)
 {
     return prog->autoload;
 }
 
 int bpf_program__set_autoload(struct bpf_program *prog, bool autoload)
 {
     if (prog->obj->loaded)
         return libbpf_err(-EINVAL);
 
     prog->autoload = autoload;
     return 0;
 }
 
 const struct bpf_insn *bpf_program__insns(const struct bpf_program *prog)
 {
     return prog->insns;
 }
 
 size_t bpf_program__insn_cnt(const struct bpf_program *prog)
 {
     return prog->insns_cnt;
 }
 
 int bpf_program__set_insns(struct bpf_program *prog,
                struct bpf_insn *new_insns, size_t new_insn_cnt)
 {
     struct bpf_insn *insns;
 
     if (prog->obj->loaded)
         return -EBUSY;
 
     insns = libbpf_reallocarray(prog->insns, new_insn_cnt, sizeof(*insns));
     if (!insns) {
         pr_warn("prog '%s': failed to realloc prog code\n", prog->name);
         return -ENOMEM;
     }
     memcpy(insns, new_insns, new_insn_cnt * sizeof(*insns));
 
     prog->insns = insns;
     prog->insns_cnt = new_insn_cnt;
     return 0;
 }
 
 int bpf_program__fd(const struct bpf_program *prog)
 {
     if (!prog)
         return libbpf_err(-EINVAL);
 
     if (prog->fd < 0)
         return libbpf_err(-ENOENT);
 
     return prog->fd;
 }
 
 __alias(bpf_program__type)
 enum bpf_prog_type bpf_program__get_type(const struct bpf_program *prog);
 
 enum bpf_prog_type bpf_program__type(const struct bpf_program *prog)
 {
     return prog->type;
 }
 
 int bpf_program__set_type(struct bpf_program *prog, enum bpf_prog_type type)
 {
     if (prog->obj->loaded)
         return libbpf_err(-EBUSY);
 
     prog->type = type;
     return 0;
 }
 
 __alias(bpf_program__expected_attach_type)
 enum bpf_attach_type bpf_program__get_expected_attach_type(const struct bpf_program *prog);
 
 enum bpf_attach_type bpf_program__expected_attach_type(const struct bpf_program *prog)
 {
     return prog->expected_attach_type;
 }
 
 int bpf_program__set_expected_attach_type(struct bpf_program *prog,
                        enum bpf_attach_type type)
 {
     if (prog->obj->loaded)
         return libbpf_err(-EBUSY);
 
     prog->expected_attach_type = type;
     return 0;
 }
 
 __u32 bpf_program__flags(const struct bpf_program *prog)
 {
     return prog->prog_flags;
 }
 
 int bpf_program__set_flags(struct bpf_program *prog, __u32 flags)
 {
     if (prog->obj->loaded)
         return libbpf_err(-EBUSY);
 
     prog->prog_flags = flags;
     return 0;
 }
 
 __u32 bpf_program__log_level(const struct bpf_program *prog)
 {
     return prog->log_level;
 }
 
 int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level)
 {
     if (prog->obj->loaded)
         return libbpf_err(-EBUSY);
 
     prog->log_level = log_level;
     return 0;
 }
 
 const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size)
 {
     *log_size = prog->log_size;
     return prog->log_buf;
 }
 
 int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log_size)
 {
     if (log_size && !log_buf)
         return -EINVAL;
     if (prog->log_size > UINT_MAX)
         return -EINVAL;
     if (prog->obj->loaded)
         return -EBUSY;
 
     prog->log_buf = log_buf;
     prog->log_size = log_size;
     return 0;
 }
 
 #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {                \
     .sec = (char *)sec_pfx,                         \
     .prog_type = BPF_PROG_TYPE_##ptype,                 \
     .expected_attach_type = atype,                      \
     .cookie = (long)(flags),                        \
     .prog_prepare_load_fn = libbpf_prepare_prog_load,           \
     __VA_ARGS__                             \
 }
 
 static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_ksyscall(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_usdt(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 
 static const struct bpf_sec_def section_defs[] = {
     SEC_DEF("socket",       SOCKET_FILTER, 0, SEC_NONE),
     SEC_DEF("sk_reuseport/migrate", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, SEC_ATTACHABLE),
     SEC_DEF("sk_reuseport",     SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT, SEC_ATTACHABLE),
     SEC_DEF("kprobe+",      KPROBE, 0, SEC_NONE, attach_kprobe),
     SEC_DEF("uprobe+",      KPROBE, 0, SEC_NONE, attach_uprobe),
     SEC_DEF("uprobe.s+",        KPROBE, 0, SEC_SLEEPABLE, attach_uprobe),
     SEC_DEF("kretprobe+",       KPROBE, 0, SEC_NONE, attach_kprobe),
     SEC_DEF("uretprobe+",       KPROBE, 0, SEC_NONE, attach_uprobe),
     SEC_DEF("uretprobe.s+",     KPROBE, 0, SEC_SLEEPABLE, attach_uprobe),
     SEC_DEF("kprobe.multi+",    KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
     SEC_DEF("kretprobe.multi+", KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
     SEC_DEF("ksyscall+",        KPROBE, 0, SEC_NONE, attach_ksyscall),
     SEC_DEF("kretsyscall+",     KPROBE, 0, SEC_NONE, attach_ksyscall),
     SEC_DEF("usdt+",        KPROBE, 0, SEC_NONE, attach_usdt),
     SEC_DEF("tc",           SCHED_CLS, 0, SEC_NONE),
     SEC_DEF("classifier",       SCHED_CLS, 0, SEC_NONE),
     SEC_DEF("action",       SCHED_ACT, 0, SEC_NONE),
     SEC_DEF("tracepoint+",      TRACEPOINT, 0, SEC_NONE, attach_tp),
     SEC_DEF("tp+",          TRACEPOINT, 0, SEC_NONE, attach_tp),
     SEC_DEF("raw_tracepoint+",  RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
     SEC_DEF("raw_tp+",      RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
     SEC_DEF("raw_tracepoint.w+",    RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
     SEC_DEF("raw_tp.w+",        RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
     SEC_DEF("tp_btf+",      TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),
     SEC_DEF("fentry+",      TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),
     SEC_DEF("fmod_ret+",        TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),
     SEC_DEF("fexit+",       TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF, attach_trace),
     SEC_DEF("fentry.s+",        TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
     SEC_DEF("fmod_ret.s+",      TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
     SEC_DEF("fexit.s+",     TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
     SEC_DEF("freplace+",        EXT, 0, SEC_ATTACH_BTF, attach_trace),
     SEC_DEF("lsm+",         LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
     SEC_DEF("lsm.s+",       LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
     SEC_DEF("lsm_cgroup+",      LSM, BPF_LSM_CGROUP, SEC_ATTACH_BTF),
     SEC_DEF("iter+",        TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),
     SEC_DEF("iter.s+",      TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_iter),
     SEC_DEF("syscall",      SYSCALL, 0, SEC_SLEEPABLE),
     SEC_DEF("xdp.frags/devmap", XDP, BPF_XDP_DEVMAP, SEC_XDP_FRAGS),
     SEC_DEF("xdp/devmap",       XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),
     SEC_DEF("xdp.frags/cpumap", XDP, BPF_XDP_CPUMAP, SEC_XDP_FRAGS),
     SEC_DEF("xdp/cpumap",       XDP, BPF_XDP_CPUMAP, SEC_ATTACHABLE),
     SEC_DEF("xdp.frags",        XDP, BPF_XDP, SEC_XDP_FRAGS),
     SEC_DEF("xdp",          XDP, BPF_XDP, SEC_ATTACHABLE_OPT),
     SEC_DEF("perf_event",       PERF_EVENT, 0, SEC_NONE),
     SEC_DEF("lwt_in",       LWT_IN, 0, SEC_NONE),
     SEC_DEF("lwt_out",      LWT_OUT, 0, SEC_NONE),
     SEC_DEF("lwt_xmit",     LWT_XMIT, 0, SEC_NONE),
     SEC_DEF("lwt_seg6local",    LWT_SEG6LOCAL, 0, SEC_NONE),
     SEC_DEF("sockops",      SOCK_OPS, BPF_CGROUP_SOCK_OPS, SEC_ATTACHABLE_OPT),
     SEC_DEF("sk_skb/stream_parser", SK_SKB, BPF_SK_SKB_STREAM_PARSER, SEC_ATTACHABLE_OPT),
     SEC_DEF("sk_skb/stream_verdict",SK_SKB, BPF_SK_SKB_STREAM_VERDICT, SEC_ATTACHABLE_OPT),
     SEC_DEF("sk_skb",       SK_SKB, 0, SEC_NONE),
     SEC_DEF("sk_msg",       SK_MSG, BPF_SK_MSG_VERDICT, SEC_ATTACHABLE_OPT),
     SEC_DEF("lirc_mode2",       LIRC_MODE2, BPF_LIRC_MODE2, SEC_ATTACHABLE_OPT),
     SEC_DEF("flow_dissector",   FLOW_DISSECTOR, BPF_FLOW_DISSECTOR, SEC_ATTACHABLE_OPT),
     SEC_DEF("cgroup_skb/ingress",   CGROUP_SKB, BPF_CGROUP_INET_INGRESS, SEC_ATTACHABLE_OPT),
     SEC_DEF("cgroup_skb/egress",    CGROUP_SKB, BPF_CGROUP_INET_EGRESS, SEC_ATTACHABLE_OPT),
     SEC_DEF("cgroup/skb",       CGROUP_SKB, 0, SEC_NONE),
     SEC_DEF("cgroup/sock_create",   CGROUP_SOCK, BPF_CGROUP_INET_SOCK_CREATE, SEC_ATTACHABLE),
     SEC_DEF("cgroup/sock_release",  CGROUP_SOCK, BPF_CGROUP_INET_SOCK_RELEASE, SEC_ATTACHABLE),
     SEC_DEF("cgroup/sock",      CGROUP_SOCK, BPF_CGROUP_INET_SOCK_CREATE, SEC_ATTACHABLE_OPT),
     SEC_DEF("cgroup/post_bind4",    CGROUP_SOCK, BPF_CGROUP_INET4_POST_BIND, SEC_ATTACHABLE),
     SEC_DEF("cgroup/post_bind6",    CGROUP_SOCK, BPF_CGROUP_INET6_POST_BIND, SEC_ATTACHABLE),
     SEC_DEF("cgroup/bind4",     CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_BIND, SEC_ATTACHABLE),
     SEC_DEF("cgroup/bind6",     CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_BIND, SEC_ATTACHABLE),
     SEC_DEF("cgroup/connect4",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_CONNECT, SEC_ATTACHABLE),
     SEC_DEF("cgroup/connect6",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_CONNECT, SEC_ATTACHABLE),
     SEC_DEF("cgroup/sendmsg4",  CGROUP_SOCK_ADDR, BPF_CGROUP_UDP4_SENDMSG, SEC_ATTACHABLE),
     SEC_DEF("cgroup/sendmsg6",  CGROUP_SOCK_ADDR, BPF_CGROUP_UDP6_SENDMSG, SEC_ATTACHABLE),
     SEC_DEF("cgroup/recvmsg4",  CGROUP_SOCK_ADDR, BPF_CGROUP_UDP4_RECVMSG, SEC_ATTACHABLE),
     SEC_DEF("cgroup/recvmsg6",  CGROUP_SOCK_ADDR, BPF_CGROUP_UDP6_RECVMSG, SEC_ATTACHABLE),
     SEC_DEF("cgroup/getpeername4",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_GETPEERNAME, SEC_ATTACHABLE),
     SEC_DEF("cgroup/getpeername6",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_GETPEERNAME, SEC_ATTACHABLE),
     SEC_DEF("cgroup/getsockname4",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_GETSOCKNAME, SEC_ATTACHABLE),
     SEC_DEF("cgroup/getsockname6",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_GETSOCKNAME, SEC_ATTACHABLE),
     SEC_DEF("cgroup/sysctl",    CGROUP_SYSCTL, BPF_CGROUP_SYSCTL, SEC_ATTACHABLE),
     SEC_DEF("cgroup/getsockopt",    CGROUP_SOCKOPT, BPF_CGROUP_GETSOCKOPT, SEC_ATTACHABLE),
     SEC_DEF("cgroup/setsockopt",    CGROUP_SOCKOPT, BPF_CGROUP_SETSOCKOPT, SEC_ATTACHABLE),
     SEC_DEF("cgroup/dev",       CGROUP_DEVICE, BPF_CGROUP_DEVICE, SEC_ATTACHABLE_OPT),
     SEC_DEF("struct_ops+",      STRUCT_OPS, 0, SEC_NONE),
     SEC_DEF("sk_lookup",        SK_LOOKUP, BPF_SK_LOOKUP, SEC_ATTACHABLE),
 };
 
 static size_t custom_sec_def_cnt;
 static struct bpf_sec_def *custom_sec_defs;
 static struct bpf_sec_def custom_fallback_def;
 static bool has_custom_fallback_def;
 
 static int last_custom_sec_def_handler_id;
 
 int libbpf_register_prog_handler(const char *sec,
                  enum bpf_prog_type prog_type,
                  enum bpf_attach_type exp_attach_type,
                  const struct libbpf_prog_handler_opts *opts)
 {
     struct bpf_sec_def *sec_def;
 
     if (!OPTS_VALID(opts, libbpf_prog_handler_opts))
         return libbpf_err(-EINVAL);
 
     if (last_custom_sec_def_handler_id == INT_MAX) /* prevent overflow */
         return libbpf_err(-E2BIG);
 
     if (sec) {
         sec_def = libbpf_reallocarray(custom_sec_defs, custom_sec_def_cnt + 1,
                           sizeof(*sec_def));
         if (!sec_def)
             return libbpf_err(-ENOMEM);
 
         custom_sec_defs = sec_def;
         sec_def = &custom_sec_defs[custom_sec_def_cnt];
     } else {
         if (has_custom_fallback_def)
             return libbpf_err(-EBUSY);
 
         sec_def = &custom_fallback_def;
     }
 
     sec_def->sec = sec ? strdup(sec) : NULL;
     if (sec && !sec_def->sec)
         return libbpf_err(-ENOMEM);
 
     sec_def->prog_type = prog_type;
     sec_def->expected_attach_type = exp_attach_type;
     sec_def->cookie = OPTS_GET(opts, cookie, 0);
 
     sec_def->prog_setup_fn = OPTS_GET(opts, prog_setup_fn, NULL);
     sec_def->prog_prepare_load_fn = OPTS_GET(opts, prog_prepare_load_fn, NULL);
     sec_def->prog_attach_fn = OPTS_GET(opts, prog_attach_fn, NULL);
 
     sec_def->handler_id = ++last_custom_sec_def_handler_id;
 
     if (sec)
         custom_sec_def_cnt++;
     else
         has_custom_fallback_def = true;
 
     return sec_def->handler_id;
 }
 
 int libbpf_unregister_prog_handler(int handler_id)
 {
     struct bpf_sec_def *sec_defs;
     int i;
 
     if (handler_id <= 0)
         return libbpf_err(-EINVAL);
 
     if (has_custom_fallback_def && custom_fallback_def.handler_id == handler_id) {
         memset(&custom_fallback_def, 0, sizeof(custom_fallback_def));
         has_custom_fallback_def = false;
         return 0;
     }
 
     for (i = 0; i < custom_sec_def_cnt; i++) {
         if (custom_sec_defs[i].handler_id == handler_id)
             break;
     }
 
     if (i == custom_sec_def_cnt)
         return libbpf_err(-ENOENT);
 
     free(custom_sec_defs[i].sec);
     for (i = i + 1; i < custom_sec_def_cnt; i++)
         custom_sec_defs[i - 1] = custom_sec_defs[i];
     custom_sec_def_cnt--;
 
     /* try to shrink the array, but it's ok if we couldn't */
     sec_defs = libbpf_reallocarray(custom_sec_defs, custom_sec_def_cnt, sizeof(*sec_defs));
     if (sec_defs)
         custom_sec_defs = sec_defs;
 
     return 0;
 }
 
 static bool sec_def_matches(const struct bpf_sec_def *sec_def, const char *sec_name)
 {
     size_t len = strlen(sec_def->sec);
 
     /* "type/" always has to have proper SEC("type/extras") form */
     if (sec_def->sec[len - 1] == '/') {
         if (str_has_pfx(sec_name, sec_def->sec))
             return true;
         return false;
     }
 
     /* "type+" means it can be either exact SEC("type") or
      * well-formed SEC("type/extras") with proper '/' separator
      */
     if (sec_def->sec[len - 1] == '+') {
         len--;
         /* not even a prefix */
         if (strncmp(sec_name, sec_def->sec, len) != 0)
             return false;
         /* exact match or has '/' separator */
         if (sec_name[len] == '\0' || sec_name[len] == '/')
             return true;
         return false;
     }
 
     return strcmp(sec_name, sec_def->sec) == 0;
 }
 
 static const struct bpf_sec_def *find_sec_def(const char *sec_name)
 {
     const struct bpf_sec_def *sec_def;
     int i, n;
 
     n = custom_sec_def_cnt;
     for (i = 0; i < n; i++) {
         sec_def = &custom_sec_defs[i];
         if (sec_def_matches(sec_def, sec_name))
             return sec_def;
     }
 
     n = ARRAY_SIZE(section_defs);
     for (i = 0; i < n; i++) {
         sec_def = &section_defs[i];
         if (sec_def_matches(sec_def, sec_name))
             return sec_def;
     }
 
     if (has_custom_fallback_def)
         return &custom_fallback_def;
 
     return NULL;
 }
 
 #define MAX_TYPE_NAME_SIZE 32
 
 static char *libbpf_get_type_names(bool attach_type)
 {
     int i, len = ARRAY_SIZE(section_defs) * MAX_TYPE_NAME_SIZE;
     char *buf;
 
     buf = malloc(len);
     if (!buf)
         return NULL;
 
     buf[0] = '\0';
     /* Forge string buf with all available names */
     for (i = 0; i < ARRAY_SIZE(section_defs); i++) {
         const struct bpf_sec_def *sec_def = &section_defs[i];
 
         if (attach_type) {
             if (sec_def->prog_prepare_load_fn != libbpf_prepare_prog_load)
                 continue;
 
             if (!(sec_def->cookie & SEC_ATTACHABLE))
                 continue;
         }
 
         if (strlen(buf) + strlen(section_defs[i].sec) + 2 > len) {
             free(buf);
             return NULL;
         }
         strcat(buf, " ");
         strcat(buf, section_defs[i].sec);
     }
 
     return buf;
 }
 
 int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
                  enum bpf_attach_type *expected_attach_type)
 {
     const struct bpf_sec_def *sec_def;
     char *type_names;
 
     if (!name)
         return libbpf_err(-EINVAL);
 
     sec_def = find_sec_def(name);
     if (sec_def) {
         *prog_type = sec_def->prog_type;
         *expected_attach_type = sec_def->expected_attach_type;
         return 0;
     }
 
     pr_debug("failed to guess program type from ELF section '%s'\n", name);
     type_names = libbpf_get_type_names(false);
     if (type_names != NULL) {
         pr_debug("supported section(type) names are:%s\n", type_names);
         free(type_names);
     }
 
     return libbpf_err(-ESRCH);
 }
 
 const char *libbpf_bpf_attach_type_str(enum bpf_attach_type t)
 {
     if (t < 0 || t >= ARRAY_SIZE(attach_type_name))
         return NULL;
 
     return attach_type_name[t];
 }
 
 const char *libbpf_bpf_link_type_str(enum bpf_link_type t)
 {
     if (t < 0 || t >= ARRAY_SIZE(link_type_name))
         return NULL;
 
     return link_type_name[t];
 }
 
 const char *libbpf_bpf_map_type_str(enum bpf_map_type t)
 {
     if (t < 0 || t >= ARRAY_SIZE(map_type_name))
         return NULL;
 
     return map_type_name[t];
 }
 
 const char *libbpf_bpf_prog_type_str(enum bpf_prog_type t)
 {
     if (t < 0 || t >= ARRAY_SIZE(prog_type_name))
         return NULL;
 
     return prog_type_name[t];
 }
 
 static struct bpf_map *find_struct_ops_map_by_offset(struct bpf_object *obj,
                              size_t offset)
 {
     struct bpf_map *map;
     size_t i;
 
     for (i = 0; i < obj->nr_maps; i++) {
         map = &obj->maps[i];
         if (!bpf_map__is_struct_ops(map))
             continue;
         if (map->sec_offset <= offset &&
             offset - map->sec_offset < map->def.value_size)
             return map;
     }
 
     return NULL;
 }
 
 /* Collect the reloc from ELF and populate the st_ops->progs[] */
 static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
                         Elf64_Shdr *shdr, Elf_Data *data)
 {
     const struct btf_member *member;
     struct bpf_struct_ops *st_ops;
     struct bpf_program *prog;
     unsigned int shdr_idx;
     const struct btf *btf;
     struct bpf_map *map;
     unsigned int moff, insn_idx;
     const char *name;
     __u32 member_idx;
     Elf64_Sym *sym;
     Elf64_Rel *rel;
     int i, nrels;
 
     btf = obj->btf;
     nrels = shdr->sh_size / shdr->sh_entsize;
     for (i = 0; i < nrels; i++) {
         rel = elf_rel_by_idx(data, i);
         if (!rel) {
             pr_warn("struct_ops reloc: failed to get %d reloc\n", i);
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         sym = elf_sym_by_idx(obj, ELF64_R_SYM(rel->r_info));
         if (!sym) {
             pr_warn("struct_ops reloc: symbol %zx not found\n",
                 (size_t)ELF64_R_SYM(rel->r_info));
             return -LIBBPF_ERRNO__FORMAT;
         }
 
         name = elf_sym_str(obj, sym->st_name) ?: "<?>";
         map = find_struct_ops_map_by_offset(obj, rel->r_offset);
         if (!map) {
             pr_warn("struct_ops reloc: cannot find map at rel->r_offset %zu\n",
                 (size_t)rel->r_offset);
             return -EINVAL;
         }
 
         moff = rel->r_offset - map->sec_offset;
         shdr_idx = sym->st_shndx;
         st_ops = map->st_ops;
         pr_debug("struct_ops reloc %s: for %lld value %lld shdr_idx %u rel->r_offset %zu map->sec_offset %zu name %d (\'%s\')\n",
              map->name,
              (long long)(rel->r_info >> 32),
              (long long)sym->st_value,
              shdr_idx, (size_t)rel->r_offset,
              map->sec_offset, sym->st_name, name);
 
         if (shdr_idx >= SHN_LORESERVE) {
             pr_warn("struct_ops reloc %s: rel->r_offset %zu shdr_idx %u unsupported non-static function\n",
                 map->name, (size_t)rel->r_offset, shdr_idx);
             return -LIBBPF_ERRNO__RELOC;
         }
         if (sym->st_value % BPF_INSN_SZ) {
             pr_warn("struct_ops reloc %s: invalid target program offset %llu\n",
                 map->name, (unsigned long long)sym->st_value);
             return -LIBBPF_ERRNO__FORMAT;
         }
         insn_idx = sym->st_value / BPF_INSN_SZ;
 
         member = find_member_by_offset(st_ops->type, moff * 8);
         if (!member) {
             pr_warn("struct_ops reloc %s: cannot find member at moff %u\n",
                 map->name, moff);
             return -EINVAL;
         }
         member_idx = member - btf_members(st_ops->type);
         name = btf__name_by_offset(btf, member->name_off);
 
         if (!resolve_func_ptr(btf, member->type, NULL)) {
             pr_warn("struct_ops reloc %s: cannot relocate non func ptr %s\n",
                 map->name, name);
             return -EINVAL;
         }
 
         prog = find_prog_by_sec_insn(obj, shdr_idx, insn_idx);
         if (!prog) {
             pr_warn("struct_ops reloc %s: cannot find prog at shdr_idx %u to relocate func ptr %s\n",
                 map->name, shdr_idx, name);
             return -EINVAL;
         }
 
         /* prevent the use of BPF prog with invalid type */
         if (prog->type != BPF_PROG_TYPE_STRUCT_OPS) {
             pr_warn("struct_ops reloc %s: prog %s is not struct_ops BPF program\n",
                 map->name, prog->name);
             return -EINVAL;
         }
 
         /* if we haven't yet processed this BPF program, record proper
          * attach_btf_id and member_idx
          */
         if (!prog->attach_btf_id) {
             prog->attach_btf_id = st_ops->type_id;
             prog->expected_attach_type = member_idx;
         }
 
         /* struct_ops BPF prog can be re-used between multiple
          * .struct_ops as long as it's the same struct_ops struct
          * definition and the same function pointer field
          */
         if (prog->attach_btf_id != st_ops->type_id ||
             prog->expected_attach_type != member_idx) {
             pr_warn("struct_ops reloc %s: cannot use prog %s in sec %s with type %u attach_btf_id %u expected_attach_type %u for func ptr %s\n",
                 map->name, prog->name, prog->sec_name, prog->type,
                 prog->attach_btf_id, prog->expected_attach_type, name);
             return -EINVAL;
         }
 
         st_ops->progs[member_idx] = prog;
     }
 
     return 0;
 }
 
 #define BTF_TRACE_PREFIX "btf_trace_"
 #define BTF_LSM_PREFIX "bpf_lsm_"
 #define BTF_ITER_PREFIX "bpf_iter_"
 #define BTF_MAX_NAME_SIZE 128
 
 void btf_get_kernel_prefix_kind(enum bpf_attach_type attach_type,
                 const char **prefix, int *kind)
 {
     switch (attach_type) {
     case BPF_TRACE_RAW_TP:
         *prefix = BTF_TRACE_PREFIX;
         *kind = BTF_KIND_TYPEDEF;
         break;
     case BPF_LSM_MAC:
     case BPF_LSM_CGROUP:
         *prefix = BTF_LSM_PREFIX;
         *kind = BTF_KIND_FUNC;
         break;
     case BPF_TRACE_ITER:
         *prefix = BTF_ITER_PREFIX;
         *kind = BTF_KIND_FUNC;
         break;
     default:
         *prefix = "";
         *kind = BTF_KIND_FUNC;
     }
 }
 
 static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
                    const char *name, __u32 kind)
 {
     char btf_type_name[BTF_MAX_NAME_SIZE];
     int ret;
 
     ret = snprintf(btf_type_name, sizeof(btf_type_name),
                "%s%s", prefix, name);
     /* snprintf returns the number of characters written excluding the
      * terminating null. So, if >= BTF_MAX_NAME_SIZE are written, it
      * indicates truncation.
      */
     if (ret < 0 || ret >= sizeof(btf_type_name))
         return -ENAMETOOLONG;
     return btf__find_by_name_kind(btf, btf_type_name, kind);
 }
 
 static inline int find_attach_btf_id(struct btf *btf, const char *name,
                      enum bpf_attach_type attach_type)
 {
     const char *prefix;
     int kind;
 
     btf_get_kernel_prefix_kind(attach_type, &prefix, &kind);
     return find_btf_by_prefix_kind(btf, prefix, name, kind);
 }
 
 int libbpf_find_vmlinux_btf_id(const char *name,
                    enum bpf_attach_type attach_type)
 {
     struct btf *btf;
     int err;
 
     btf = btf__load_vmlinux_btf();
     err = libbpf_get_error(btf);
     if (err) {
         pr_warn("vmlinux BTF is not found\n");
         return libbpf_err(err);
     }
 
     err = find_attach_btf_id(btf, name, attach_type);
     if (err <= 0)
         pr_warn("%s is not found in vmlinux BTF\n", name);
 
     btf__free(btf);
     return libbpf_err(err);
 }
 
 static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
 {
     struct bpf_prog_info info = {};
     __u32 info_len = sizeof(info);
     struct btf *btf;
     int err;
 
     err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
     if (err) {
         pr_warn("failed bpf_obj_get_info_by_fd for FD %d: %d\n",
             attach_prog_fd, err);
         return err;
     }
 
     err = -EINVAL;
     if (!info.btf_id) {
         pr_warn("The target program doesn't have BTF\n");
         goto out;
     }
     btf = btf__load_from_kernel_by_id(info.btf_id);
     err = libbpf_get_error(btf);
     if (err) {
         pr_warn("Failed to get BTF %d of the program: %d\n", info.btf_id, err);
         goto out;
     }
     err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
     btf__free(btf);
     if (err <= 0) {
         pr_warn("%s is not found in prog's BTF\n", name);
         goto out;
     }
 out:
     return err;
 }
 
 static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
                   enum bpf_attach_type attach_type,
                   int *btf_obj_fd, int *btf_type_id)
 {
     int ret, i;
 
     ret = find_attach_btf_id(obj->btf_vmlinux, attach_name, attach_type);
     if (ret > 0) {
         *btf_obj_fd = 0; /* vmlinux BTF */
         *btf_type_id = ret;
         return 0;
     }
     if (ret != -ENOENT)
         return ret;
 
     ret = load_module_btfs(obj);
     if (ret)
         return ret;
 
     for (i = 0; i < obj->btf_module_cnt; i++) {
         const struct module_btf *mod = &obj->btf_modules[i];
 
         ret = find_attach_btf_id(mod->btf, attach_name, attach_type);
         if (ret > 0) {
             *btf_obj_fd = mod->fd;
             *btf_type_id = ret;
             return 0;
         }
         if (ret == -ENOENT)
             continue;
 
         return ret;
     }
 
     return -ESRCH;
 }
 
 static int libbpf_find_attach_btf_id(struct bpf_program *prog, const char *attach_name,
                      int *btf_obj_fd, int *btf_type_id)
 {
     enum bpf_attach_type attach_type = prog->expected_attach_type;
     __u32 attach_prog_fd = prog->attach_prog_fd;
     int err = 0;
 
     /* BPF program's BTF ID */
     if (attach_prog_fd) {
         err = libbpf_find_prog_btf_id(attach_name, attach_prog_fd);
         if (err < 0) {
             pr_warn("failed to find BPF program (FD %d) BTF ID for '%s': %d\n",
                  attach_prog_fd, attach_name, err);
             return err;
         }
         *btf_obj_fd = 0;
         *btf_type_id = err;
         return 0;
     }
 
     /* kernel/module BTF ID */
     if (prog->obj->gen_loader) {
         bpf_gen__record_attach_target(prog->obj->gen_loader, attach_name, attach_type);
         *btf_obj_fd = 0;
         *btf_type_id = 1;
     } else {
         err = find_kernel_btf_id(prog->obj, attach_name, attach_type, btf_obj_fd, btf_type_id);
     }
     if (err) {
         pr_warn("failed to find kernel BTF type ID of '%s': %d\n", attach_name, err);
         return err;
     }
     return 0;
 }
 
 int libbpf_attach_type_by_name(const char *name,
                    enum bpf_attach_type *attach_type)
 {
     char *type_names;
     const struct bpf_sec_def *sec_def;
 
     if (!name)
         return libbpf_err(-EINVAL);
 
     sec_def = find_sec_def(name);
     if (!sec_def) {
         pr_debug("failed to guess attach type based on ELF section name '%s'\n", name);
         type_names = libbpf_get_type_names(true);
         if (type_names != NULL) {
             pr_debug("attachable section(type) names are:%s\n", type_names);
             free(type_names);
         }
 
         return libbpf_err(-EINVAL);
     }
 
     if (sec_def->prog_prepare_load_fn != libbpf_prepare_prog_load)
         return libbpf_err(-EINVAL);
     if (!(sec_def->cookie & SEC_ATTACHABLE))
         return libbpf_err(-EINVAL);
 
     *attach_type = sec_def->expected_attach_type;
     return 0;
 }
 
 int bpf_map__fd(const struct bpf_map *map)
 {
     return map ? map->fd : libbpf_err(-EINVAL);
 }
 
 static bool map_uses_real_name(const struct bpf_map *map)
 {
     /* Since libbpf started to support custom .data.* and .rodata.* maps,
      * their user-visible name differs from kernel-visible name. Users see
      * such map's corresponding ELF section name as a map name.
      * This check distinguishes .data/.rodata from .data.* and .rodata.*
      * maps to know which name has to be returned to the user.
      */
     if (map->libbpf_type == LIBBPF_MAP_DATA && strcmp(map->real_name, DATA_SEC) != 0)
         return true;
     if (map->libbpf_type == LIBBPF_MAP_RODATA && strcmp(map->real_name, RODATA_SEC) != 0)
         return true;
     return false;
 }
 
 const char *bpf_map__name(const struct bpf_map *map)
 {
     if (!map)
         return NULL;
 
     if (map_uses_real_name(map))
         return map->real_name;
 
     return map->name;
 }
 
 enum bpf_map_type bpf_map__type(const struct bpf_map *map)
 {
     return map->def.type;
 }
 
 int bpf_map__set_type(struct bpf_map *map, enum bpf_map_type type)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->def.type = type;
     return 0;
 }
 
 __u32 bpf_map__map_flags(const struct bpf_map *map)
 {
     return map->def.map_flags;
 }
 
 int bpf_map__set_map_flags(struct bpf_map *map, __u32 flags)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->def.map_flags = flags;
     return 0;
 }
 
 __u64 bpf_map__map_extra(const struct bpf_map *map)
 {
     return map->map_extra;
 }
 
 int bpf_map__set_map_extra(struct bpf_map *map, __u64 map_extra)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->map_extra = map_extra;
     return 0;
 }
 
 __u32 bpf_map__numa_node(const struct bpf_map *map)
 {
     return map->numa_node;
 }
 
 int bpf_map__set_numa_node(struct bpf_map *map, __u32 numa_node)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->numa_node = numa_node;
     return 0;
 }
 
 __u32 bpf_map__key_size(const struct bpf_map *map)
 {
     return map->def.key_size;
 }
 
 int bpf_map__set_key_size(struct bpf_map *map, __u32 size)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->def.key_size = size;
     return 0;
 }
 
 __u32 bpf_map__value_size(const struct bpf_map *map)
 {
     return map->def.value_size;
 }
 
 int bpf_map__set_value_size(struct bpf_map *map, __u32 size)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->def.value_size = size;
     return 0;
 }
 
 __u32 bpf_map__btf_key_type_id(const struct bpf_map *map)
 {
     return map ? map->btf_key_type_id : 0;
 }
 
 __u32 bpf_map__btf_value_type_id(const struct bpf_map *map)
 {
     return map ? map->btf_value_type_id : 0;
 }
 
 int bpf_map__set_initial_value(struct bpf_map *map,
                    const void *data, size_t size)
 {
     if (!map->mmaped || map->libbpf_type == LIBBPF_MAP_KCONFIG ||
         size != map->def.value_size || map->fd >= 0)
         return libbpf_err(-EINVAL);
 
     memcpy(map->mmaped, data, size);
     return 0;
 }
 
 const void *bpf_map__initial_value(struct bpf_map *map, size_t *psize)
 {
     if (!map->mmaped)
         return NULL;
     *psize = map->def.value_size;
     return map->mmaped;
 }
 
 bool bpf_map__is_internal(const struct bpf_map *map)
 {
     return map->libbpf_type != LIBBPF_MAP_UNSPEC;
 }
 
 __u32 bpf_map__ifindex(const struct bpf_map *map)
 {
     return map->map_ifindex;
 }
 
 int bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex)
 {
     if (map->fd >= 0)
         return libbpf_err(-EBUSY);
     map->map_ifindex = ifindex;
     return 0;
 }
 
 int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd)
 {
     if (!bpf_map_type__is_map_in_map(map->def.type)) {
         pr_warn("error: unsupported map type\n");
         return libbpf_err(-EINVAL);
     }
     if (map->inner_map_fd != -1) {
         pr_warn("error: inner_map_fd already specified\n");
         return libbpf_err(-EINVAL);
     }
     if (map->inner_map) {
         bpf_map__destroy(map->inner_map);
         zfree(&map->inner_map);
     }
     map->inner_map_fd = fd;
     return 0;
 }
 
 static struct bpf_map *
 __bpf_map__iter(const struct bpf_map *m, const struct bpf_object *obj, int i)
 {
     ssize_t idx;
     struct bpf_map *s, *e;
 
     if (!obj || !obj->maps)
         return errno = EINVAL, NULL;
 
     s = obj->maps;
     e = obj->maps + obj->nr_maps;
 
     if ((m < s) || (m >= e)) {
         pr_warn("error in %s: map handler doesn't belong to object\n",
              __func__);
         return errno = EINVAL, NULL;
     }
 
     idx = (m - obj->maps) + i;
     if (idx >= obj->nr_maps || idx < 0)
         return NULL;
     return &obj->maps[idx];
 }
 
 struct bpf_map *
 bpf_object__next_map(const struct bpf_object *obj, const struct bpf_map *prev)
 {
     if (prev == NULL)
         return obj->maps;
 
     return __bpf_map__iter(prev, obj, 1);
 }
 
 struct bpf_map *
 bpf_object__prev_map(const struct bpf_object *obj, const struct bpf_map *next)
 {
     if (next == NULL) {
         if (!obj->nr_maps)
             return NULL;
         return obj->maps + obj->nr_maps - 1;
     }
 
     return __bpf_map__iter(next, obj, -1);
 }
 
 struct bpf_map *
 bpf_object__find_map_by_name(const struct bpf_object *obj, const char *name)
 {
     struct bpf_map *pos;
 
     bpf_object__for_each_map(pos, obj) {
         /* if it's a special internal map name (which always starts
          * with dot) then check if that special name matches the
          * real map name (ELF section name)
          */
         if (name[0] == '.') {
             if (pos->real_name && strcmp(pos->real_name, name) == 0)
                 return pos;
             continue;
         }
         /* otherwise map name has to be an exact match */
         if (map_uses_real_name(pos)) {
             if (strcmp(pos->real_name, name) == 0)
                 return pos;
             continue;
         }
         if (strcmp(pos->name, name) == 0)
             return pos;
     }
     return errno = ENOENT, NULL;
 }
 
 int
 bpf_object__find_map_fd_by_name(const struct bpf_object *obj, const char *name)
 {
     return bpf_map__fd(bpf_object__find_map_by_name(obj, name));
 }
 
 static int validate_map_op(const struct bpf_map *map, size_t key_sz,
                size_t value_sz, bool check_value_sz)
 {
     if (map->fd <= 0)
         return -ENOENT;
 
     if (map->def.key_size != key_sz) {
         pr_warn("map '%s': unexpected key size %zu provided, expected %u\n",
             map->name, key_sz, map->def.key_size);
         return -EINVAL;
     }
 
     if (!check_value_sz)
         return 0;
 
     switch (map->def.type) {
     case BPF_MAP_TYPE_PERCPU_ARRAY:
     case BPF_MAP_TYPE_PERCPU_HASH:
     case BPF_MAP_TYPE_LRU_PERCPU_HASH:
     case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE: {
         int num_cpu = libbpf_num_possible_cpus();
         size_t elem_sz = roundup(map->def.value_size, 8);
 
         if (value_sz != num_cpu * elem_sz) {
             pr_warn("map '%s': unexpected value size %zu provided for per-CPU map, expected %d * %zu = %zd\n",
                 map->name, value_sz, num_cpu, elem_sz, num_cpu * elem_sz);
             return -EINVAL;
         }
         break;
     }
     default:
         if (map->def.value_size != value_sz) {
             pr_warn("map '%s': unexpected value size %zu provided, expected %u\n",
                 map->name, value_sz, map->def.value_size);
             return -EINVAL;
         }
         break;
     }
     return 0;
 }
 
 int bpf_map__lookup_elem(const struct bpf_map *map,
              const void *key, size_t key_sz,
              void *value, size_t value_sz, __u64 flags)
 {
     int err;
 
     err = validate_map_op(map, key_sz, value_sz, true);
     if (err)
         return libbpf_err(err);
 
     return bpf_map_lookup_elem_flags(map->fd, key, value, flags);
 }
 
 int bpf_map__update_elem(const struct bpf_map *map,
              const void *key, size_t key_sz,
              const void *value, size_t value_sz, __u64 flags)
 {
     int err;
 
     err = validate_map_op(map, key_sz, value_sz, true);
     if (err)
         return libbpf_err(err);
 
     return bpf_map_update_elem(map->fd, key, value, flags);
 }
 
 int bpf_map__delete_elem(const struct bpf_map *map,
              const void *key, size_t key_sz, __u64 flags)
 {
     int err;
 
     err = validate_map_op(map, key_sz, 0, false /* check_value_sz */);
     if (err)
         return libbpf_err(err);
 
     return bpf_map_delete_elem_flags(map->fd, key, flags);
 }
 
 int bpf_map__lookup_and_delete_elem(const struct bpf_map *map,
                     const void *key, size_t key_sz,
                     void *value, size_t value_sz, __u64 flags)
 {
     int err;
 
     err = validate_map_op(map, key_sz, value_sz, true);
     if (err)
         return libbpf_err(err);
 
     return bpf_map_lookup_and_delete_elem_flags(map->fd, key, value, flags);
 }
 
 int bpf_map__get_next_key(const struct bpf_map *map,
               const void *cur_key, void *next_key, size_t key_sz)
 {
     int err;
 
     err = validate_map_op(map, key_sz, 0, false /* check_value_sz */);
     if (err)
         return libbpf_err(err);
 
     return bpf_map_get_next_key(map->fd, cur_key, next_key);
 }
 
 long libbpf_get_error(const void *ptr)
 {
     if (!IS_ERR_OR_NULL(ptr))
         return 0;
 
     if (IS_ERR(ptr))
         errno = -PTR_ERR(ptr);
 
     /* If ptr == NULL, then errno should be already set by the failing
      * API, because libbpf never returns NULL on success and it now always
      * sets errno on error. So no extra errno handling for ptr == NULL
      * case.
      */
     return -errno;
 }
 
 /* Replace link's underlying BPF program with the new one */
 int bpf_link__update_program(struct bpf_link *link, struct bpf_program *prog)
 {
     int ret;
 
     ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog), NULL);
     return libbpf_err_errno(ret);
 }
 
 /* Release "ownership" of underlying BPF resource (typically, BPF program
  * attached to some BPF hook, e.g., tracepoint, kprobe, etc). Disconnected
  * link, when destructed through bpf_link__destroy() call won't attempt to
  * detach/unregisted that BPF resource. This is useful in situations where,
  * say, attached BPF program has to outlive userspace program that attached it
  * in the system. Depending on type of BPF program, though, there might be
  * additional steps (like pinning BPF program in BPF FS) necessary to ensure
  * exit of userspace program doesn't trigger automatic detachment and clean up
  * inside the kernel.
  */
 void bpf_link__disconnect(struct bpf_link *link)
 {
     link->disconnected = true;
 }
 
 int bpf_link__destroy(struct bpf_link *link)
 {
     int err = 0;
 
     if (IS_ERR_OR_NULL(link))
         return 0;
 
     if (!link->disconnected && link->detach)
         err = link->detach(link);
     if (link->pin_path)
         free(link->pin_path);
     if (link->dealloc)
         link->dealloc(link);
     else
         free(link);
 
     return libbpf_err(err);
 }
 
 int bpf_link__fd(const struct bpf_link *link)
 {
     return link->fd;
 }
 
 const char *bpf_link__pin_path(const struct bpf_link *link)
 {
     return link->pin_path;
 }
 
 static int bpf_link__detach_fd(struct bpf_link *link)
 {
     return libbpf_err_errno(close(link->fd));
 }
 
 struct bpf_link *bpf_link__open(const char *path)
 {
     struct bpf_link *link;
     int fd;
 
     fd = bpf_obj_get(path);
     if (fd < 0) {
         fd = -errno;
         pr_warn("failed to open link at %s: %d\n", path, fd);
         return libbpf_err_ptr(fd);
     }
 
     link = calloc(1, sizeof(*link));
     if (!link) {
         close(fd);
         return libbpf_err_ptr(-ENOMEM);
     }
     link->detach = &bpf_link__detach_fd;
     link->fd = fd;
 
     link->pin_path = strdup(path);
     if (!link->pin_path) {
         bpf_link__destroy(link);
         return libbpf_err_ptr(-ENOMEM);
     }
 
     return link;
 }
 
 int bpf_link__detach(struct bpf_link *link)
 {
     return bpf_link_detach(link->fd) ? -errno : 0;
 }
 
 int bpf_link__pin(struct bpf_link *link, const char *path)
 {
     int err;
 
     if (link->pin_path)
         return libbpf_err(-EBUSY);
     err = make_parent_dir(path);
     if (err)
         return libbpf_err(err);
     err = check_path(path);
     if (err)
         return libbpf_err(err);
 
     link->pin_path = strdup(path);
     if (!link->pin_path)
         return libbpf_err(-ENOMEM);
 
     if (bpf_obj_pin(link->fd, link->pin_path)) {
         err = -errno;
         zfree(&link->pin_path);
         return libbpf_err(err);
     }
 
     pr_debug("link fd=%d: pinned at %s\n", link->fd, link->pin_path);
     return 0;
 }
 
 int bpf_link__unpin(struct bpf_link *link)
 {
     int err;
 
     if (!link->pin_path)
         return libbpf_err(-EINVAL);
 
     err = unlink(link->pin_path);
     if (err != 0)
         return -errno;
 
     pr_debug("link fd=%d: unpinned from %s\n", link->fd, link->pin_path);
     zfree(&link->pin_path);
     return 0;
 }
 
 struct bpf_link_perf {
     struct bpf_link link;
     int perf_event_fd;
     /* legacy kprobe support: keep track of probe identifier and type */
     char *legacy_probe_name;
     bool legacy_is_kprobe;
     bool legacy_is_retprobe;
 };
 
 static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe);
 static int remove_uprobe_event_legacy(const char *probe_name, bool retprobe);
 
 static int bpf_link_perf_detach(struct bpf_link *link)
 {
     struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
     int err = 0;
 
     if (ioctl(perf_link->perf_event_fd, PERF_EVENT_IOC_DISABLE, 0) < 0)
         err = -errno;
 
     if (perf_link->perf_event_fd != link->fd)
         close(perf_link->perf_event_fd);
     close(link->fd);
 
     /* legacy uprobe/kprobe needs to be removed after perf event fd closure */
     if (perf_link->legacy_probe_name) {
         if (perf_link->legacy_is_kprobe) {
             err = remove_kprobe_event_legacy(perf_link->legacy_probe_name,
                              perf_link->legacy_is_retprobe);
         } else {
             err = remove_uprobe_event_legacy(perf_link->legacy_probe_name,
                              perf_link->legacy_is_retprobe);
         }
     }
 
     return err;
 }
 
 static void bpf_link_perf_dealloc(struct bpf_link *link)
 {
     struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
 
     free(perf_link->legacy_probe_name);
     free(perf_link);
 }
 
 struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *prog, int pfd,
                              const struct bpf_perf_event_opts *opts)
 {
     char errmsg[STRERR_BUFSIZE];
     struct bpf_link_perf *link;
     int prog_fd, link_fd = -1, err;
 
     if (!OPTS_VALID(opts, bpf_perf_event_opts))
         return libbpf_err_ptr(-EINVAL);
 
     if (pfd < 0) {
         pr_warn("prog '%s': invalid perf event FD %d\n",
             prog->name, pfd);
         return libbpf_err_ptr(-EINVAL);
     }
     prog_fd = bpf_program__fd(prog);
     if (prog_fd < 0) {
         pr_warn("prog '%s': can't attach BPF program w/o FD (did you load it?)\n",
             prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     link = calloc(1, sizeof(*link));
     if (!link)
         return libbpf_err_ptr(-ENOMEM);
     link->link.detach = &bpf_link_perf_detach;
     link->link.dealloc = &bpf_link_perf_dealloc;
     link->perf_event_fd = pfd;
 
     if (kernel_supports(prog->obj, FEAT_PERF_LINK)) {
         DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
             .perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
 
         link_fd = bpf_link_create(prog_fd, pfd, BPF_PERF_EVENT, &link_opts);
         if (link_fd < 0) {
             err = -errno;
             pr_warn("prog '%s': failed to create BPF link for perf_event FD %d: %d (%s)\n",
                 prog->name, pfd,
                 err, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
             goto err_out;
         }
         link->link.fd = link_fd;
     } else {
         if (OPTS_GET(opts, bpf_cookie, 0)) {
             pr_warn("prog '%s': user context value is not supported\n", prog->name);
             err = -EOPNOTSUPP;
             goto err_out;
         }
 
         if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) {
             err = -errno;
             pr_warn("prog '%s': failed to attach to perf_event FD %d: %s\n",
                 prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
             if (err == -EPROTO)
                 pr_warn("prog '%s': try add PERF_SAMPLE_CALLCHAIN to or remove exclude_callchain_[kernel|user] from pfd %d\n",
                     prog->name, pfd);
             goto err_out;
         }
         link->link.fd = pfd;
     }
     if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
         err = -errno;
         pr_warn("prog '%s': failed to enable perf_event FD %d: %s\n",
             prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_out;
     }
 
     return &link->link;
 err_out:
     if (link_fd >= 0)
         close(link_fd);
     free(link);
     return libbpf_err_ptr(err);
 }
 
 struct bpf_link *bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd)
 {
     return bpf_program__attach_perf_event_opts(prog, pfd, NULL);
 }
 
 /*
  * this function is expected to parse integer in the range of [0, 2^31-1] from
  * given file using scanf format string fmt. If actual parsed value is
  * negative, the result might be indistinguishable from error
  */
 static int parse_uint_from_file(const char *file, const char *fmt)
 {
     char buf[STRERR_BUFSIZE];
     int err, ret;
     FILE *f;
 
     f = fopen(file, "r");
     if (!f) {
         err = -errno;
         pr_debug("failed to open '%s': %s\n", file,
              libbpf_strerror_r(err, buf, sizeof(buf)));
         return err;
     }
     err = fscanf(f, fmt, &ret);
     if (err != 1) {
         err = err == EOF ? -EIO : -errno;
         pr_debug("failed to parse '%s': %s\n", file,
             libbpf_strerror_r(err, buf, sizeof(buf)));
         fclose(f);
         return err;
     }
     fclose(f);
     return ret;
 }
 
 static int determine_kprobe_perf_type(void)
 {
     const char *file = "/sys/bus/event_source/devices/kprobe/type";
 
     return parse_uint_from_file(file, "%d\n");
 }
 
 static int determine_uprobe_perf_type(void)
 {
     const char *file = "/sys/bus/event_source/devices/uprobe/type";
 
     return parse_uint_from_file(file, "%d\n");
 }
 
 static int determine_kprobe_retprobe_bit(void)
 {
     const char *file = "/sys/bus/event_source/devices/kprobe/format/retprobe";
 
     return parse_uint_from_file(file, "config:%d\n");
 }
 
 static int determine_uprobe_retprobe_bit(void)
 {
     const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
 
     return parse_uint_from_file(file, "config:%d\n");
 }
 
 #define PERF_UPROBE_REF_CTR_OFFSET_BITS 32
 #define PERF_UPROBE_REF_CTR_OFFSET_SHIFT 32
 
 static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
                  uint64_t offset, int pid, size_t ref_ctr_off)
 {
     struct perf_event_attr attr = {};
     char errmsg[STRERR_BUFSIZE];
     int type, pfd;
 
     if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
         return -EINVAL;
 
     type = uprobe ? determine_uprobe_perf_type()
               : determine_kprobe_perf_type();
     if (type < 0) {
         pr_warn("failed to determine %s perf type: %s\n",
             uprobe ? "uprobe" : "kprobe",
             libbpf_strerror_r(type, errmsg, sizeof(errmsg)));
         return type;
     }
     if (retprobe) {
         int bit = uprobe ? determine_uprobe_retprobe_bit()
                  : determine_kprobe_retprobe_bit();
 
         if (bit < 0) {
             pr_warn("failed to determine %s retprobe bit: %s\n",
                 uprobe ? "uprobe" : "kprobe",
                 libbpf_strerror_r(bit, errmsg, sizeof(errmsg)));
             return bit;
         }
         attr.config |= 1 << bit;
     }
     attr.size = sizeof(attr);
     attr.type = type;
     attr.config |= (__u64)ref_ctr_off << PERF_UPROBE_REF_CTR_OFFSET_SHIFT;
     attr.config1 = ptr_to_u64(name); /* kprobe_func or uprobe_path */
     attr.config2 = offset;       /* kprobe_addr or probe_offset */
 
     /* pid filter is meaningful only for uprobes */
     pfd = syscall(__NR_perf_event_open, &attr,
               pid < 0 ? -1 : pid /* pid */,
               pid == -1 ? 0 : -1 /* cpu */,
               -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
     return pfd >= 0 ? pfd : -errno;
 }
 
 static int append_to_file(const char *file, const char *fmt, ...)
 {
     int fd, n, err = 0;
     va_list ap;
 
     fd = open(file, O_WRONLY | O_APPEND | O_CLOEXEC, 0);
     if (fd < 0)
         return -errno;
 
     va_start(ap, fmt);
     n = vdprintf(fd, fmt, ap);
     va_end(ap);
 
     if (n < 0)
         err = -errno;
 
     close(fd);
     return err;
 }
 
 #define DEBUGFS "/sys/kernel/debug/tracing"
 #define TRACEFS "/sys/kernel/tracing"
 
 static bool use_debugfs(void)
 {
     static int has_debugfs = -1;
 
     if (has_debugfs < 0)
         has_debugfs = access(DEBUGFS, F_OK) == 0;
 
     return has_debugfs == 1;
 }
 
 static const char *tracefs_path(void)
 {
     return use_debugfs() ? DEBUGFS : TRACEFS;
 }
 
 static const char *tracefs_kprobe_events(void)
 {
     return use_debugfs() ? DEBUGFS"/kprobe_events" : TRACEFS"/kprobe_events";
 }
 
 static const char *tracefs_uprobe_events(void)
 {
     return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
 }
 
 static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
                      const char *kfunc_name, size_t offset)
 {
     static int index = 0;
 
     snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
          __sync_fetch_and_add(&index, 1));
 }
 
 static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,
                    const char *kfunc_name, size_t offset)
 {
     return append_to_file(tracefs_kprobe_events(), "%c:%s/%s %s+0x%zx",
                   retprobe ? 'r' : 'p',
                   retprobe ? "kretprobes" : "kprobes",
                   probe_name, kfunc_name, offset);
 }
 
 static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe)
 {
     return append_to_file(tracefs_kprobe_events(), "-:%s/%s",
                   retprobe ? "kretprobes" : "kprobes", probe_name);
 }
 
 static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retprobe)
 {
     char file[256];
 
     snprintf(file, sizeof(file), "%s/events/%s/%s/id",
          tracefs_path(), retprobe ? "kretprobes" : "kprobes", probe_name);
 
     return parse_uint_from_file(file, "%d\n");
 }
 
 static int perf_event_kprobe_open_legacy(const char *probe_name, bool retprobe,
                      const char *kfunc_name, size_t offset, int pid)
 {
     struct perf_event_attr attr = {};
     char errmsg[STRERR_BUFSIZE];
     int type, pfd, err;
 
     err = add_kprobe_event_legacy(probe_name, retprobe, kfunc_name, offset);
     if (err < 0) {
         pr_warn("failed to add legacy kprobe event for '%s+0x%zx': %s\n",
             kfunc_name, offset,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         return err;
     }
     type = determine_kprobe_perf_type_legacy(probe_name, retprobe);
     if (type < 0) {
         err = type;
         pr_warn("failed to determine legacy kprobe event id for '%s+0x%zx': %s\n",
             kfunc_name, offset,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_clean_legacy;
     }
     attr.size = sizeof(attr);
     attr.config = type;
     attr.type = PERF_TYPE_TRACEPOINT;
 
     pfd = syscall(__NR_perf_event_open, &attr,
               pid < 0 ? -1 : pid, /* pid */
               pid == -1 ? 0 : -1, /* cpu */
               -1 /* group_fd */,  PERF_FLAG_FD_CLOEXEC);
     if (pfd < 0) {
         err = -errno;
         pr_warn("legacy kprobe perf_event_open() failed: %s\n",
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_clean_legacy;
     }
     return pfd;
 
 err_clean_legacy:
     /* Clear the newly added legacy kprobe_event */
     remove_kprobe_event_legacy(probe_name, retprobe);
     return err;
 }
 
 static const char *arch_specific_syscall_pfx(void)
 {
 #if defined(__x86_64__)
     return "x64";
 #elif defined(__i386__)
     return "ia32";
 #elif defined(__s390x__)
     return "s390x";
 #elif defined(__s390__)
     return "s390";
 #elif defined(__arm__)
     return "arm";
 #elif defined(__aarch64__)
     return "arm64";
 #elif defined(__mips__)
     return "mips";
 #elif defined(__riscv)
     return "riscv";
 #elif defined(__powerpc__)
     return "powerpc";
 #elif defined(__powerpc64__)
     return "powerpc64";
 #else
     return NULL;
 #endif
 }
 
 static int probe_kern_syscall_wrapper(void)
 {
     char syscall_name[64];
     const char *ksys_pfx;
 
     ksys_pfx = arch_specific_syscall_pfx();
     if (!ksys_pfx)
         return 0;
 
     snprintf(syscall_name, sizeof(syscall_name), "__%s_sys_bpf", ksys_pfx);
 
     if (determine_kprobe_perf_type() >= 0) {
         int pfd;
 
         pfd = perf_event_open_probe(false, false, syscall_name, 0, getpid(), 0);
         if (pfd >= 0)
             close(pfd);
 
         return pfd >= 0 ? 1 : 0;
     } else { /* legacy mode */
         char probe_name[128];
 
         gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
         if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
             return 0;
 
         (void)remove_kprobe_event_legacy(probe_name, false);
         return 1;
     }
 }
 
 struct bpf_link *
 bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
                 const char *func_name,
                 const struct bpf_kprobe_opts *opts)
 {
     DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
     char errmsg[STRERR_BUFSIZE];
     char *legacy_probe = NULL;
     struct bpf_link *link;
     size_t offset;
     bool retprobe, legacy;
     int pfd, err;
 
     if (!OPTS_VALID(opts, bpf_kprobe_opts))
         return libbpf_err_ptr(-EINVAL);
 
     retprobe = OPTS_GET(opts, retprobe, false);
     offset = OPTS_GET(opts, offset, 0);
     pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
 
     legacy = determine_kprobe_perf_type() < 0;
     if (!legacy) {
         pfd = perf_event_open_probe(false /* uprobe */, retprobe,
                         func_name, offset,
                         -1 /* pid */, 0 /* ref_ctr_off */);
     } else {
         char probe_name[256];
 
         gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
                          func_name, offset);
 
         legacy_probe = strdup(probe_name);
         if (!legacy_probe)
             return libbpf_err_ptr(-ENOMEM);
 
         pfd = perf_event_kprobe_open_legacy(legacy_probe, retprobe, func_name,
                             offset, -1 /* pid */);
     }
     if (pfd < 0) {
         err = -errno;
         pr_warn("prog '%s': failed to create %s '%s+0x%zx' perf event: %s\n",
             prog->name, retprobe ? "kretprobe" : "kprobe",
             func_name, offset,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_out;
     }
     link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
     err = libbpf_get_error(link);
     if (err) {
         close(pfd);
         pr_warn("prog '%s': failed to attach to %s '%s+0x%zx': %s\n",
             prog->name, retprobe ? "kretprobe" : "kprobe",
             func_name, offset,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_clean_legacy;
     }
     if (legacy) {
         struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
 
         perf_link->legacy_probe_name = legacy_probe;
         perf_link->legacy_is_kprobe = true;
         perf_link->legacy_is_retprobe = retprobe;
     }
 
     return link;
 
 err_clean_legacy:
     if (legacy)
         remove_kprobe_event_legacy(legacy_probe, retprobe);
 err_out:
     free(legacy_probe);
     return libbpf_err_ptr(err);
 }
 
 struct bpf_link *bpf_program__attach_kprobe(const struct bpf_program *prog,
                         bool retprobe,
                         const char *func_name)
 {
     DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts,
         .retprobe = retprobe,
     );
 
     return bpf_program__attach_kprobe_opts(prog, func_name, &opts);
 }
 
 struct bpf_link *bpf_program__attach_ksyscall(const struct bpf_program *prog,
                           const char *syscall_name,
                           const struct bpf_ksyscall_opts *opts)
 {
     LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts);
     char func_name[128];
 
     if (!OPTS_VALID(opts, bpf_ksyscall_opts))
         return libbpf_err_ptr(-EINVAL);
 
     if (kernel_supports(prog->obj, FEAT_SYSCALL_WRAPPER)) {
         /* arch_specific_syscall_pfx() should never return NULL here
          * because it is guarded by kernel_supports(). However, since
          * compiler does not know that we have an explicit conditional
          * as well.
          */
         snprintf(func_name, sizeof(func_name), "__%s_sys_%s",
              arch_specific_syscall_pfx() ? : "", syscall_name);
     } else {
         snprintf(func_name, sizeof(func_name), "__se_sys_%s", syscall_name);
     }
 
     kprobe_opts.retprobe = OPTS_GET(opts, retprobe, false);
     kprobe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
 
     return bpf_program__attach_kprobe_opts(prog, func_name, &kprobe_opts);
 }
 
 /* Adapted from perf/util/string.c */
 static bool glob_match(const char *str, const char *pat)
 {
     while (*str && *pat && *pat != '*') {
         if (*pat == '?') {      /* Matches any single character */
             str++;
             pat++;
             continue;
         }
         if (*str != *pat)
             return false;
         str++;
         pat++;
     }
     /* Check wild card */
     if (*pat == '*') {
         while (*pat == '*')
             pat++;
         if (!*pat) /* Tail wild card matches all */
             return true;
         while (*str)
             if (glob_match(str++, pat))
                 return true;
     }
     return !*str && !*pat;
 }
 
 struct kprobe_multi_resolve {
     const char *pattern;
     unsigned long *addrs;
     size_t cap;
     size_t cnt;
 };
 
 static int
 resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
             const char *sym_name, void *ctx)
 {
     struct kprobe_multi_resolve *res = ctx;
     int err;
 
     if (!glob_match(sym_name, res->pattern))
         return 0;
 
     err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
                 res->cnt + 1);
     if (err)
         return err;
 
     res->addrs[res->cnt++] = (unsigned long) sym_addr;
     return 0;
 }
 
 struct bpf_link *
 bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
                       const char *pattern,
                       const struct bpf_kprobe_multi_opts *opts)
 {
     LIBBPF_OPTS(bpf_link_create_opts, lopts);
     struct kprobe_multi_resolve res = {
         .pattern = pattern,
     };
     struct bpf_link *link = NULL;
     char errmsg[STRERR_BUFSIZE];
     const unsigned long *addrs;
     int err, link_fd, prog_fd;
     const __u64 *cookies;
     const char **syms;
     bool retprobe;
     size_t cnt;
 
     if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
         return libbpf_err_ptr(-EINVAL);
 
     syms    = OPTS_GET(opts, syms, false);
     addrs   = OPTS_GET(opts, addrs, false);
     cnt     = OPTS_GET(opts, cnt, false);
     cookies = OPTS_GET(opts, cookies, false);
 
     if (!pattern && !addrs && !syms)
         return libbpf_err_ptr(-EINVAL);
     if (pattern && (addrs || syms || cookies || cnt))
         return libbpf_err_ptr(-EINVAL);
     if (!pattern && !cnt)
         return libbpf_err_ptr(-EINVAL);
     if (addrs && syms)
         return libbpf_err_ptr(-EINVAL);
 
     if (pattern) {
         err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
         if (err)
             goto error;
         if (!res.cnt) {
             err = -ENOENT;
             goto error;
         }
         addrs = res.addrs;
         cnt = res.cnt;
     }
 
     retprobe = OPTS_GET(opts, retprobe, false);
 
     lopts.kprobe_multi.syms = syms;
     lopts.kprobe_multi.addrs = addrs;
     lopts.kprobe_multi.cookies = cookies;
     lopts.kprobe_multi.cnt = cnt;
     lopts.kprobe_multi.flags = retprobe ? BPF_F_KPROBE_MULTI_RETURN : 0;
 
     link = calloc(1, sizeof(*link));
     if (!link) {
         err = -ENOMEM;
         goto error;
     }
     link->detach = &bpf_link__detach_fd;
 
     prog_fd = bpf_program__fd(prog);
     link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_KPROBE_MULTI, &lopts);
     if (link_fd < 0) {
         err = -errno;
         pr_warn("prog '%s': failed to attach: %s\n",
             prog->name, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto error;
     }
     link->fd = link_fd;
     free(res.addrs);
     return link;
 
 error:
     free(link);
     free(res.addrs);
     return libbpf_err_ptr(err);
 }
 
 static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts);
     unsigned long offset = 0;
     const char *func_name;
     char *func;
     int n;
 
     *link = NULL;
 
     /* no auto-attach for SEC("kprobe") and SEC("kretprobe") */
     if (strcmp(prog->sec_name, "kprobe") == 0 || strcmp(prog->sec_name, "kretprobe") == 0)
         return 0;
 
     opts.retprobe = str_has_pfx(prog->sec_name, "kretprobe/");
     if (opts.retprobe)
         func_name = prog->sec_name + sizeof("kretprobe/") - 1;
     else
         func_name = prog->sec_name + sizeof("kprobe/") - 1;
 
     n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);
     if (n < 1) {
         pr_warn("kprobe name is invalid: %s\n", func_name);
         return -EINVAL;
     }
     if (opts.retprobe && offset != 0) {
         free(func);
         pr_warn("kretprobes do not support offset specification\n");
         return -EINVAL;
     }
 
     opts.offset = offset;
     *link = bpf_program__attach_kprobe_opts(prog, func, &opts);
     free(func);
     return libbpf_get_error(*link);
 }
 
 static int attach_ksyscall(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     LIBBPF_OPTS(bpf_ksyscall_opts, opts);
     const char *syscall_name;
 
     *link = NULL;
 
     /* no auto-attach for SEC("ksyscall") and SEC("kretsyscall") */
     if (strcmp(prog->sec_name, "ksyscall") == 0 || strcmp(prog->sec_name, "kretsyscall") == 0)
         return 0;
 
     opts.retprobe = str_has_pfx(prog->sec_name, "kretsyscall/");
     if (opts.retprobe)
         syscall_name = prog->sec_name + sizeof("kretsyscall/") - 1;
     else
         syscall_name = prog->sec_name + sizeof("ksyscall/") - 1;
 
     *link = bpf_program__attach_ksyscall(prog, syscall_name, &opts);
     return *link ? 0 : -errno;
 }
 
 static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
     const char *spec;
     char *pattern;
     int n;
 
     *link = NULL;
 
     /* no auto-attach for SEC("kprobe.multi") and SEC("kretprobe.multi") */
     if (strcmp(prog->sec_name, "kprobe.multi") == 0 ||
         strcmp(prog->sec_name, "kretprobe.multi") == 0)
         return 0;
 
     opts.retprobe = str_has_pfx(prog->sec_name, "kretprobe.multi/");
     if (opts.retprobe)
         spec = prog->sec_name + sizeof("kretprobe.multi/") - 1;
     else
         spec = prog->sec_name + sizeof("kprobe.multi/") - 1;
 
     n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern);
     if (n < 1) {
         pr_warn("kprobe multi pattern is invalid: %s\n", pattern);
         return -EINVAL;
     }
 
     *link = bpf_program__attach_kprobe_multi_opts(prog, pattern, &opts);
     free(pattern);
     return libbpf_get_error(*link);
 }
 
 static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
                      const char *binary_path, uint64_t offset)
 {
     int i;
 
     snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
 
     /* sanitize binary_path in the probe name */
     for (i = 0; buf[i]; i++) {
         if (!isalnum(buf[i]))
             buf[i] = '_';
     }
 }
 
 static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
                       const char *binary_path, size_t offset)
 {
     return append_to_file(tracefs_uprobe_events(), "%c:%s/%s %s:0x%zx",
                   retprobe ? 'r' : 'p',
                   retprobe ? "uretprobes" : "uprobes",
                   probe_name, binary_path, offset);
 }
 
 static inline int remove_uprobe_event_legacy(const char *probe_name, bool retprobe)
 {
     return append_to_file(tracefs_uprobe_events(), "-:%s/%s",
                   retprobe ? "uretprobes" : "uprobes", probe_name);
 }
 
 static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retprobe)
 {
     char file[512];
 
     snprintf(file, sizeof(file), "%s/events/%s/%s/id",
          tracefs_path(), retprobe ? "uretprobes" : "uprobes", probe_name);
 
     return parse_uint_from_file(file, "%d\n");
 }
 
 static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe,
                      const char *binary_path, size_t offset, int pid)
 {
     struct perf_event_attr attr;
     int type, pfd, err;
 
     err = add_uprobe_event_legacy(probe_name, retprobe, binary_path, offset);
     if (err < 0) {
         pr_warn("failed to add legacy uprobe event for %s:0x%zx: %d\n",
             binary_path, (size_t)offset, err);
         return err;
     }
     type = determine_uprobe_perf_type_legacy(probe_name, retprobe);
     if (type < 0) {
         err = type;
         pr_warn("failed to determine legacy uprobe event id for %s:0x%zx: %d\n",
             binary_path, offset, err);
         goto err_clean_legacy;
     }
 
     memset(&attr, 0, sizeof(attr));
     attr.size = sizeof(attr);
     attr.config = type;
     attr.type = PERF_TYPE_TRACEPOINT;
 
     pfd = syscall(__NR_perf_event_open, &attr,
               pid < 0 ? -1 : pid, /* pid */
               pid == -1 ? 0 : -1, /* cpu */
               -1 /* group_fd */,  PERF_FLAG_FD_CLOEXEC);
     if (pfd < 0) {
         err = -errno;
         pr_warn("legacy uprobe perf_event_open() failed: %d\n", err);
         goto err_clean_legacy;
     }
     return pfd;
 
 err_clean_legacy:
     /* Clear the newly added legacy uprobe_event */
     remove_uprobe_event_legacy(probe_name, retprobe);
     return err;
 }
 
 /* Return next ELF section of sh_type after scn, or first of that type if scn is NULL. */
 static Elf_Scn *elf_find_next_scn_by_type(Elf *elf, int sh_type, Elf_Scn *scn)
 {
     while ((scn = elf_nextscn(elf, scn)) != NULL) {
         GElf_Shdr sh;
 
         if (!gelf_getshdr(scn, &sh))
             continue;
         if (sh.sh_type == sh_type)
             return scn;
     }
     return NULL;
 }
 
 /* Find offset of function name in object specified by path.  "name" matches
  * symbol name or name@@LIB for library functions.
  */
 static long elf_find_func_offset(const char *binary_path, const char *name)
 {
     int fd, i, sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
     bool is_shared_lib, is_name_qualified;
     char errmsg[STRERR_BUFSIZE];
     long ret = -ENOENT;
     size_t name_len;
     GElf_Ehdr ehdr;
     Elf *elf;
 
     fd = open(binary_path, O_RDONLY | O_CLOEXEC);
     if (fd < 0) {
         ret = -errno;
         pr_warn("failed to open %s: %s\n", binary_path,
             libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));
         return ret;
     }
     elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
     if (!elf) {
         pr_warn("elf: could not read elf from %s: %s\n", binary_path, elf_errmsg(-1));
         close(fd);
         return -LIBBPF_ERRNO__FORMAT;
     }
     if (!gelf_getehdr(elf, &ehdr)) {
         pr_warn("elf: failed to get ehdr from %s: %s\n", binary_path, elf_errmsg(-1));
         ret = -LIBBPF_ERRNO__FORMAT;
         goto out;
     }
     /* for shared lib case, we do not need to calculate relative offset */
     is_shared_lib = ehdr.e_type == ET_DYN;
 
     name_len = strlen(name);
     /* Does name specify "@@LIB"? */
     is_name_qualified = strstr(name, "@@") != NULL;
 
     /* Search SHT_DYNSYM, SHT_SYMTAB for symbol.  This search order is used because if
      * a binary is stripped, it may only have SHT_DYNSYM, and a fully-statically
      * linked binary may not have SHT_DYMSYM, so absence of a section should not be
      * reported as a warning/error.
      */
     for (i = 0; i < ARRAY_SIZE(sh_types); i++) {
         size_t nr_syms, strtabidx, idx;
         Elf_Data *symbols = NULL;
         Elf_Scn *scn = NULL;
         int last_bind = -1;
         const char *sname;
         GElf_Shdr sh;
 
         scn = elf_find_next_scn_by_type(elf, sh_types[i], NULL);
         if (!scn) {
             pr_debug("elf: failed to find symbol table ELF sections in '%s'\n",
                  binary_path);
             continue;
         }
         if (!gelf_getshdr(scn, &sh))
             continue;
         strtabidx = sh.sh_link;
         symbols = elf_getdata(scn, 0);
         if (!symbols) {
             pr_warn("elf: failed to get symbols for symtab section in '%s': %s\n",
                 binary_path, elf_errmsg(-1));
             ret = -LIBBPF_ERRNO__FORMAT;
             goto out;
         }
         nr_syms = symbols->d_size / sh.sh_entsize;
 
         for (idx = 0; idx < nr_syms; idx++) {
             int curr_bind;
             GElf_Sym sym;
             Elf_Scn *sym_scn;
             GElf_Shdr sym_sh;
 
             if (!gelf_getsym(symbols, idx, &sym))
                 continue;
 
             if (GELF_ST_TYPE(sym.st_info) != STT_FUNC)
                 continue;
 
             sname = elf_strptr(elf, strtabidx, sym.st_name);
             if (!sname)
                 continue;
 
             curr_bind = GELF_ST_BIND(sym.st_info);
 
             /* User can specify func, func@@LIB or func@@LIB_VERSION. */
             if (strncmp(sname, name, name_len) != 0)
                 continue;
             /* ...but we don't want a search for "foo" to match 'foo2" also, so any
              * additional characters in sname should be of the form "@@LIB".
              */
             if (!is_name_qualified && sname[name_len] != '\0' && sname[name_len] != '@')
                 continue;
 
             if (ret >= 0) {
                 /* handle multiple matches */
                 if (last_bind != STB_WEAK && curr_bind != STB_WEAK) {
                     /* Only accept one non-weak bind. */
                     pr_warn("elf: ambiguous match for '%s', '%s' in '%s'\n",
                         sname, name, binary_path);
                     ret = -LIBBPF_ERRNO__FORMAT;
                     goto out;
                 } else if (curr_bind == STB_WEAK) {
                     /* already have a non-weak bind, and
                      * this is a weak bind, so ignore.
                      */
                     continue;
                 }
             }
 
             /* Transform symbol's virtual address (absolute for
              * binaries and relative for shared libs) into file
              * offset, which is what kernel is expecting for
              * uprobe/uretprobe attachment.
              * See Documentation/trace/uprobetracer.rst for more
              * details.
              * This is done by looking up symbol's containing
              * section's header and using it's virtual address
              * (sh_addr) and corresponding file offset (sh_offset)
              * to transform sym.st_value (virtual address) into
              * desired final file offset.
              */
             sym_scn = elf_getscn(elf, sym.st_shndx);
             if (!sym_scn)
                 continue;
             if (!gelf_getshdr(sym_scn, &sym_sh))
                 continue;
 
             ret = sym.st_value - sym_sh.sh_addr + sym_sh.sh_offset;
             last_bind = curr_bind;
         }
         if (ret > 0)
             break;
     }
 
     if (ret > 0) {
         pr_debug("elf: symbol address match for '%s' in '%s': 0x%lx\n", name, binary_path,
              ret);
     } else {
         if (ret == 0) {
             pr_warn("elf: '%s' is 0 in symtab for '%s': %s\n", name, binary_path,
                 is_shared_lib ? "should not be 0 in a shared library" :
                         "try using shared library path instead");
             ret = -ENOENT;
         } else {
             pr_warn("elf: failed to find symbol '%s' in '%s'\n", name, binary_path);
         }
     }
 out:
     elf_end(elf);
     close(fd);
     return ret;
 }
 
 static const char *arch_specific_lib_paths(void)
 {
     /*
      * Based on https://packages.debian.org/sid/libc6.
      *
      * Assume that the traced program is built for the same architecture
      * as libbpf, which should cover the vast majority of cases.
      */
 #if defined(__x86_64__)
     return "/lib/x86_64-linux-gnu";
 #elif defined(__i386__)
     return "/lib/i386-linux-gnu";
 #elif defined(__s390x__)
     return "/lib/s390x-linux-gnu";
 #elif defined(__s390__)
     return "/lib/s390-linux-gnu";
 #elif defined(__arm__) && defined(__SOFTFP__)
     return "/lib/arm-linux-gnueabi";
 #elif defined(__arm__) && !defined(__SOFTFP__)
     return "/lib/arm-linux-gnueabihf";
 #elif defined(__aarch64__)
     return "/lib/aarch64-linux-gnu";
 #elif defined(__mips__) && defined(__MIPSEL__) && _MIPS_SZLONG == 64
     return "/lib/mips64el-linux-gnuabi64";
 #elif defined(__mips__) && defined(__MIPSEL__) && _MIPS_SZLONG == 32
     return "/lib/mipsel-linux-gnu";
 #elif defined(__powerpc64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
     return "/lib/powerpc64le-linux-gnu";
 #elif defined(__sparc__) && defined(__arch64__)
     return "/lib/sparc64-linux-gnu";
 #elif defined(__riscv) && __riscv_xlen == 64
     return "/lib/riscv64-linux-gnu";
 #else
     return NULL;
 #endif
 }
 
 /* Get full path to program/shared library. */
 static int resolve_full_path(const char *file, char *result, size_t result_sz)
 {
     const char *search_paths[3] = {};
     int i;
 
     if (str_has_sfx(file, ".so") || strstr(file, ".so.")) {
         search_paths[0] = getenv("LD_LIBRARY_PATH");
         search_paths[1] = "/usr/lib64:/usr/lib";
         search_paths[2] = arch_specific_lib_paths();
     } else {
         search_paths[0] = getenv("PATH");
         search_paths[1] = "/usr/bin:/usr/sbin";
     }
 
     for (i = 0; i < ARRAY_SIZE(search_paths); i++) {
         const char *s;
 
         if (!search_paths[i])
             continue;
         for (s = search_paths[i]; s != NULL; s = strchr(s, ':')) {
             char *next_path;
             int seg_len;
 
             if (s[0] == ':')
                 s++;
             next_path = strchr(s, ':');
             seg_len = next_path ? next_path - s : strlen(s);
             if (!seg_len)
                 continue;
             snprintf(result, result_sz, "%.*s/%s", seg_len, s, file);
             /* ensure it is an executable file/link */
             if (access(result, R_OK | X_OK) < 0)
                 continue;
             pr_debug("resolved '%s' to '%s'\n", file, result);
             return 0;
         }
     }
     return -ENOENT;
 }
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
                 const char *binary_path, size_t func_offset,
                 const struct bpf_uprobe_opts *opts)
 {
     DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
     char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
     char full_binary_path[PATH_MAX];
     struct bpf_link *link;
     size_t ref_ctr_off;
     int pfd, err;
     bool retprobe, legacy;
     const char *func_name;
 
     if (!OPTS_VALID(opts, bpf_uprobe_opts))
         return libbpf_err_ptr(-EINVAL);
 
     retprobe = OPTS_GET(opts, retprobe, false);
     ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
     pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
 
     if (!binary_path)
         return libbpf_err_ptr(-EINVAL);
 
     if (!strchr(binary_path, '/')) {
         err = resolve_full_path(binary_path, full_binary_path,
                     sizeof(full_binary_path));
         if (err) {
             pr_warn("prog '%s': failed to resolve full path for '%s': %d\n",
                 prog->name, binary_path, err);
             return libbpf_err_ptr(err);
         }
         binary_path = full_binary_path;
     }
     func_name = OPTS_GET(opts, func_name, NULL);
     if (func_name) {
         long sym_off;
 
         sym_off = elf_find_func_offset(binary_path, func_name);
         if (sym_off < 0)
             return libbpf_err_ptr(sym_off);
         func_offset += sym_off;
     }
 
     legacy = determine_uprobe_perf_type() < 0;
     if (!legacy) {
         pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
                         func_offset, pid, ref_ctr_off);
     } else {
         char probe_name[PATH_MAX + 64];
 
         if (ref_ctr_off)
             return libbpf_err_ptr(-EINVAL);
 
         gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
                          binary_path, func_offset);
 
         legacy_probe = strdup(probe_name);
         if (!legacy_probe)
             return libbpf_err_ptr(-ENOMEM);
 
         pfd = perf_event_uprobe_open_legacy(legacy_probe, retprobe,
                             binary_path, func_offset, pid);
     }
     if (pfd < 0) {
         err = -errno;
         pr_warn("prog '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
             prog->name, retprobe ? "uretprobe" : "uprobe",
             binary_path, func_offset,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_out;
     }
 
     link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
     err = libbpf_get_error(link);
     if (err) {
         close(pfd);
         pr_warn("prog '%s': failed to attach to %s '%s:0x%zx': %s\n",
             prog->name, retprobe ? "uretprobe" : "uprobe",
             binary_path, func_offset,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         goto err_clean_legacy;
     }
     if (legacy) {
         struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
 
         perf_link->legacy_probe_name = legacy_probe;
         perf_link->legacy_is_kprobe = false;
         perf_link->legacy_is_retprobe = retprobe;
     }
     return link;
 
 err_clean_legacy:
     if (legacy)
         remove_uprobe_event_legacy(legacy_probe, retprobe);
 err_out:
     free(legacy_probe);
     return libbpf_err_ptr(err);
 }
 
 /* Format of u[ret]probe section definition supporting auto-attach:
  * u[ret]probe/binary:function[+offset]
  *
  * binary can be an absolute/relative path or a filename; the latter is resolved to a
  * full binary path via bpf_program__attach_uprobe_opts.
  *
  * Specifying uprobe+ ensures we carry out strict matching; either "uprobe" must be
  * specified (and auto-attach is not possible) or the above format is specified for
  * auto-attach.
  */
 static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);
     char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;
     int n, ret = -EINVAL;
     long offset = 0;
 
     *link = NULL;
 
     n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.]+%li",
            &probe_type, &binary_path, &func_name, &offset);
     switch (n) {
     case 1:
         /* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */
         ret = 0;
         break;
     case 2:
         pr_warn("prog '%s': section '%s' missing ':function[+offset]' specification\n",
             prog->name, prog->sec_name);
         break;
     case 3:
     case 4:
         opts.retprobe = strcmp(probe_type, "uretprobe") == 0 ||
                 strcmp(probe_type, "uretprobe.s") == 0;
         if (opts.retprobe && offset != 0) {
             pr_warn("prog '%s': uretprobes do not support offset specification\n",
                 prog->name);
             break;
         }
         opts.func_name = func_name;
         *link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);
         ret = libbpf_get_error(*link);
         break;
     default:
         pr_warn("prog '%s': invalid format of section definition '%s'\n", prog->name,
             prog->sec_name);
         break;
     }
     free(probe_type);
     free(binary_path);
     free(func_name);
 
     return ret;
 }
 
 struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
                         bool retprobe, pid_t pid,
                         const char *binary_path,
                         size_t func_offset)
 {
     DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts, .retprobe = retprobe);
 
     return bpf_program__attach_uprobe_opts(prog, pid, binary_path, func_offset, &opts);
 }
 
 struct bpf_link *bpf_program__attach_usdt(const struct bpf_program *prog,
                       pid_t pid, const char *binary_path,
                       const char *usdt_provider, const char *usdt_name,
                       const struct bpf_usdt_opts *opts)
 {
     char resolved_path[512];
     struct bpf_object *obj = prog->obj;
     struct bpf_link *link;
     __u64 usdt_cookie;
     int err;
 
     if (!OPTS_VALID(opts, bpf_uprobe_opts))
         return libbpf_err_ptr(-EINVAL);
 
     if (bpf_program__fd(prog) < 0) {
         pr_warn("prog '%s': can't attach BPF program w/o FD (did you load it?)\n",
             prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     if (!binary_path)
         return libbpf_err_ptr(-EINVAL);
 
     if (!strchr(binary_path, '/')) {
         err = resolve_full_path(binary_path, resolved_path, sizeof(resolved_path));
         if (err) {
             pr_warn("prog '%s': failed to resolve full path for '%s': %d\n",
                 prog->name, binary_path, err);
             return libbpf_err_ptr(err);
         }
         binary_path = resolved_path;
     }
 
     /* USDT manager is instantiated lazily on first USDT attach. It will
      * be destroyed together with BPF object in bpf_object__close().
      */
     if (IS_ERR(obj->usdt_man))
         return libbpf_ptr(obj->usdt_man);
     if (!obj->usdt_man) {
         obj->usdt_man = usdt_manager_new(obj);
         if (IS_ERR(obj->usdt_man))
             return libbpf_ptr(obj->usdt_man);
     }
 
     usdt_cookie = OPTS_GET(opts, usdt_cookie, 0);
     link = usdt_manager_attach_usdt(obj->usdt_man, prog, pid, binary_path,
                         usdt_provider, usdt_name, usdt_cookie);
     err = libbpf_get_error(link);
     if (err)
         return libbpf_err_ptr(err);
     return link;
 }
 
 static int attach_usdt(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     char *path = NULL, *provider = NULL, *name = NULL;
     const char *sec_name;
     int n, err;
 
     sec_name = bpf_program__section_name(prog);
     if (strcmp(sec_name, "usdt") == 0) {
         /* no auto-attach for just SEC("usdt") */
         *link = NULL;
         return 0;
     }
 
     n = sscanf(sec_name, "usdt/%m[^:]:%m[^:]:%m[^:]", &path, &provider, &name);
     if (n != 3) {
         pr_warn("invalid section '%s', expected SEC(\"usdt/<path>:<provider>:<name>\")\n",
             sec_name);
         err = -EINVAL;
     } else {
         *link = bpf_program__attach_usdt(prog, -1 /* any process */, path,
                          provider, name, NULL);
         err = libbpf_get_error(*link);
     }
     free(path);
     free(provider);
     free(name);
     return err;
 }
 
 static int determine_tracepoint_id(const char *tp_category,
                    const char *tp_name)
 {
     char file[PATH_MAX];
     int ret;
 
     ret = snprintf(file, sizeof(file), "%s/events/%s/%s/id",
                tracefs_path(), tp_category, tp_name);
     if (ret < 0)
         return -errno;
     if (ret >= sizeof(file)) {
         pr_debug("tracepoint %s/%s path is too long\n",
              tp_category, tp_name);
         return -E2BIG;
     }
     return parse_uint_from_file(file, "%d\n");
 }
 
 static int perf_event_open_tracepoint(const char *tp_category,
                       const char *tp_name)
 {
     struct perf_event_attr attr = {};
     char errmsg[STRERR_BUFSIZE];
     int tp_id, pfd, err;
 
     tp_id = determine_tracepoint_id(tp_category, tp_name);
     if (tp_id < 0) {
         pr_warn("failed to determine tracepoint '%s/%s' perf event ID: %s\n",
             tp_category, tp_name,
             libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
         return tp_id;
     }
 
     attr.type = PERF_TYPE_TRACEPOINT;
     attr.size = sizeof(attr);
     attr.config = tp_id;
 
     pfd = syscall(__NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
               -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
     if (pfd < 0) {
         err = -errno;
         pr_warn("tracepoint '%s/%s' perf_event_open() failed: %s\n",
             tp_category, tp_name,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         return err;
     }
     return pfd;
 }
 
 struct bpf_link *bpf_program__attach_tracepoint_opts(const struct bpf_program *prog,
                              const char *tp_category,
                              const char *tp_name,
                              const struct bpf_tracepoint_opts *opts)
 {
     DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
     char errmsg[STRERR_BUFSIZE];
     struct bpf_link *link;
     int pfd, err;
 
     if (!OPTS_VALID(opts, bpf_tracepoint_opts))
         return libbpf_err_ptr(-EINVAL);
 
     pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
 
     pfd = perf_event_open_tracepoint(tp_category, tp_name);
     if (pfd < 0) {
         pr_warn("prog '%s': failed to create tracepoint '%s/%s' perf event: %s\n",
             prog->name, tp_category, tp_name,
             libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
         return libbpf_err_ptr(pfd);
     }
     link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
     err = libbpf_get_error(link);
     if (err) {
         close(pfd);
         pr_warn("prog '%s': failed to attach to tracepoint '%s/%s': %s\n",
             prog->name, tp_category, tp_name,
             libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
         return libbpf_err_ptr(err);
     }
     return link;
 }
 
 struct bpf_link *bpf_program__attach_tracepoint(const struct bpf_program *prog,
                         const char *tp_category,
                         const char *tp_name)
 {
     return bpf_program__attach_tracepoint_opts(prog, tp_category, tp_name, NULL);
 }
 
 static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     char *sec_name, *tp_cat, *tp_name;
 
     *link = NULL;
 
     /* no auto-attach for SEC("tp") or SEC("tracepoint") */
     if (strcmp(prog->sec_name, "tp") == 0 || strcmp(prog->sec_name, "tracepoint") == 0)
         return 0;
 
     sec_name = strdup(prog->sec_name);
     if (!sec_name)
         return -ENOMEM;
 
     /* extract "tp/<category>/<name>" or "tracepoint/<category>/<name>" */
     if (str_has_pfx(prog->sec_name, "tp/"))
         tp_cat = sec_name + sizeof("tp/") - 1;
     else
         tp_cat = sec_name + sizeof("tracepoint/") - 1;
     tp_name = strchr(tp_cat, '/');
     if (!tp_name) {
         free(sec_name);
         return -EINVAL;
     }
     *tp_name = '\0';
     tp_name++;
 
     *link = bpf_program__attach_tracepoint(prog, tp_cat, tp_name);
     free(sec_name);
     return libbpf_get_error(*link);
 }
 
 struct bpf_link *bpf_program__attach_raw_tracepoint(const struct bpf_program *prog,
                             const char *tp_name)
 {
     char errmsg[STRERR_BUFSIZE];
     struct bpf_link *link;
     int prog_fd, pfd;
 
     prog_fd = bpf_program__fd(prog);
     if (prog_fd < 0) {
         pr_warn("prog '%s': can't attach before loaded\n", prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     link = calloc(1, sizeof(*link));
     if (!link)
         return libbpf_err_ptr(-ENOMEM);
     link->detach = &bpf_link__detach_fd;
 
     pfd = bpf_raw_tracepoint_open(tp_name, prog_fd);
     if (pfd < 0) {
         pfd = -errno;
         free(link);
         pr_warn("prog '%s': failed to attach to raw tracepoint '%s': %s\n",
             prog->name, tp_name, libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
         return libbpf_err_ptr(pfd);
     }
     link->fd = pfd;
     return link;
 }
 
 static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     static const char *const prefixes[] = {
         "raw_tp",
         "raw_tracepoint",
         "raw_tp.w",
         "raw_tracepoint.w",
     };
     size_t i;
     const char *tp_name = NULL;
 
     *link = NULL;
 
     for (i = 0; i < ARRAY_SIZE(prefixes); i++) {
         size_t pfx_len;
 
         if (!str_has_pfx(prog->sec_name, prefixes[i]))
             continue;
 
         pfx_len = strlen(prefixes[i]);
         /* no auto-attach case of, e.g., SEC("raw_tp") */
         if (prog->sec_name[pfx_len] == '\0')
             return 0;
 
         if (prog->sec_name[pfx_len] != '/')
             continue;
 
         tp_name = prog->sec_name + pfx_len + 1;
         break;
     }
 
     if (!tp_name) {
         pr_warn("prog '%s': invalid section name '%s'\n",
             prog->name, prog->sec_name);
         return -EINVAL;
     }
 
     *link = bpf_program__attach_raw_tracepoint(prog, tp_name);
     return libbpf_get_error(link);
 }
 
 /* Common logic for all BPF program types that attach to a btf_id */
 static struct bpf_link *bpf_program__attach_btf_id(const struct bpf_program *prog,
                            const struct bpf_trace_opts *opts)
 {
     LIBBPF_OPTS(bpf_link_create_opts, link_opts);
     char errmsg[STRERR_BUFSIZE];
     struct bpf_link *link;
     int prog_fd, pfd;
 
     if (!OPTS_VALID(opts, bpf_trace_opts))
         return libbpf_err_ptr(-EINVAL);
 
     prog_fd = bpf_program__fd(prog);
     if (prog_fd < 0) {
         pr_warn("prog '%s': can't attach before loaded\n", prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     link = calloc(1, sizeof(*link));
     if (!link)
         return libbpf_err_ptr(-ENOMEM);
     link->detach = &bpf_link__detach_fd;
 
     /* libbpf is smart enough to redirect to BPF_RAW_TRACEPOINT_OPEN on old kernels */
     link_opts.tracing.cookie = OPTS_GET(opts, cookie, 0);
     pfd = bpf_link_create(prog_fd, 0, bpf_program__expected_attach_type(prog), &link_opts);
     if (pfd < 0) {
         pfd = -errno;
         free(link);
         pr_warn("prog '%s': failed to attach: %s\n",
             prog->name, libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
         return libbpf_err_ptr(pfd);
     }
     link->fd = pfd;
     return link;
 }
 
 struct bpf_link *bpf_program__attach_trace(const struct bpf_program *prog)
 {
     return bpf_program__attach_btf_id(prog, NULL);
 }
 
 struct bpf_link *bpf_program__attach_trace_opts(const struct bpf_program *prog,
                         const struct bpf_trace_opts *opts)
 {
     return bpf_program__attach_btf_id(prog, opts);
 }
 
 struct bpf_link *bpf_program__attach_lsm(const struct bpf_program *prog)
 {
     return bpf_program__attach_btf_id(prog, NULL);
 }
 
 static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     *link = bpf_program__attach_trace(prog);
     return libbpf_get_error(*link);
 }
 
 static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     *link = bpf_program__attach_lsm(prog);
     return libbpf_get_error(*link);
 }
 
 static struct bpf_link *
 bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id,
                const char *target_name)
 {
     DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts,
                 .target_btf_id = btf_id);
     enum bpf_attach_type attach_type;
     char errmsg[STRERR_BUFSIZE];
     struct bpf_link *link;
     int prog_fd, link_fd;
 
     prog_fd = bpf_program__fd(prog);
     if (prog_fd < 0) {
         pr_warn("prog '%s': can't attach before loaded\n", prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     link = calloc(1, sizeof(*link));
     if (!link)
         return libbpf_err_ptr(-ENOMEM);
     link->detach = &bpf_link__detach_fd;
 
     attach_type = bpf_program__expected_attach_type(prog);
     link_fd = bpf_link_create(prog_fd, target_fd, attach_type, &opts);
     if (link_fd < 0) {
         link_fd = -errno;
         free(link);
         pr_warn("prog '%s': failed to attach to %s: %s\n",
             prog->name, target_name,
             libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg)));
         return libbpf_err_ptr(link_fd);
     }
     link->fd = link_fd;
     return link;
 }
 
 struct bpf_link *
 bpf_program__attach_cgroup(const struct bpf_program *prog, int cgroup_fd)
 {
     return bpf_program__attach_fd(prog, cgroup_fd, 0, "cgroup");
 }
 
 struct bpf_link *
 bpf_program__attach_netns(const struct bpf_program *prog, int netns_fd)
 {
     return bpf_program__attach_fd(prog, netns_fd, 0, "netns");
 }
 
 struct bpf_link *bpf_program__attach_xdp(const struct bpf_program *prog, int ifindex)
 {
     /* target_fd/target_ifindex use the same field in LINK_CREATE */
     return bpf_program__attach_fd(prog, ifindex, 0, "xdp");
 }
 
 struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
                           int target_fd,
                           const char *attach_func_name)
 {
     int btf_id;
 
     if (!!target_fd != !!attach_func_name) {
         pr_warn("prog '%s': supply none or both of target_fd and attach_func_name\n",
             prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     if (prog->type != BPF_PROG_TYPE_EXT) {
         pr_warn("prog '%s': only BPF_PROG_TYPE_EXT can attach as freplace",
             prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     if (target_fd) {
         btf_id = libbpf_find_prog_btf_id(attach_func_name, target_fd);
         if (btf_id < 0)
             return libbpf_err_ptr(btf_id);
 
         return bpf_program__attach_fd(prog, target_fd, btf_id, "freplace");
     } else {
         /* no target, so use raw_tracepoint_open for compatibility
          * with old kernels
          */
         return bpf_program__attach_trace(prog);
     }
 }
 
 struct bpf_link *
 bpf_program__attach_iter(const struct bpf_program *prog,
              const struct bpf_iter_attach_opts *opts)
 {
     DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_create_opts);
     char errmsg[STRERR_BUFSIZE];
     struct bpf_link *link;
     int prog_fd, link_fd;
     __u32 target_fd = 0;
 
     if (!OPTS_VALID(opts, bpf_iter_attach_opts))
         return libbpf_err_ptr(-EINVAL);
 
     link_create_opts.iter_info = OPTS_GET(opts, link_info, (void *)0);
     link_create_opts.iter_info_len = OPTS_GET(opts, link_info_len, 0);
 
     prog_fd = bpf_program__fd(prog);
     if (prog_fd < 0) {
         pr_warn("prog '%s': can't attach before loaded\n", prog->name);
         return libbpf_err_ptr(-EINVAL);
     }
 
     link = calloc(1, sizeof(*link));
     if (!link)
         return libbpf_err_ptr(-ENOMEM);
     link->detach = &bpf_link__detach_fd;
 
     link_fd = bpf_link_create(prog_fd, target_fd, BPF_TRACE_ITER,
                   &link_create_opts);
     if (link_fd < 0) {
         link_fd = -errno;
         free(link);
         pr_warn("prog '%s': failed to attach to iterator: %s\n",
             prog->name, libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg)));
         return libbpf_err_ptr(link_fd);
     }
     link->fd = link_fd;
     return link;
 }
 
 static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
     *link = bpf_program__attach_iter(prog, NULL);
     return libbpf_get_error(*link);
 }
 
 struct bpf_link *bpf_program__attach(const struct bpf_program *prog)
 {
     struct bpf_link *link = NULL;
     int err;
 
     if (!prog->sec_def || !prog->sec_def->prog_attach_fn)
         return libbpf_err_ptr(-EOPNOTSUPP);
 
     err = prog->sec_def->prog_attach_fn(prog, prog->sec_def->cookie, &link);
     if (err)
         return libbpf_err_ptr(err);
 
     /* When calling bpf_program__attach() explicitly, auto-attach support
      * is expected to work, so NULL returned link is considered an error.
      * This is different for skeleton's attach, see comment in
      * bpf_object__attach_skeleton().
      */
     if (!link)
         return libbpf_err_ptr(-EOPNOTSUPP);
 
     return link;
 }
 
 static int bpf_link__detach_struct_ops(struct bpf_link *link)
 {
     __u32 zero = 0;
 
     if (bpf_map_delete_elem(link->fd, &zero))
         return -errno;
 
     return 0;
 }
 
 struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
 {
     struct bpf_struct_ops *st_ops;
     struct bpf_link *link;
     __u32 i, zero = 0;
     int err;
 
     if (!bpf_map__is_struct_ops(map) || map->fd == -1)
         return libbpf_err_ptr(-EINVAL);
 
     link = calloc(1, sizeof(*link));
     if (!link)
         return libbpf_err_ptr(-EINVAL);
 
     st_ops = map->st_ops;
     for (i = 0; i < btf_vlen(st_ops->type); i++) {
         struct bpf_program *prog = st_ops->progs[i];
         void *kern_data;
         int prog_fd;
 
         if (!prog)
             continue;
 
         prog_fd = bpf_program__fd(prog);
         kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i];
         *(unsigned long *)kern_data = prog_fd;
     }
 
     err = bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0);
     if (err) {
         err = -errno;
         free(link);
         return libbpf_err_ptr(err);
     }
 
     link->detach = bpf_link__detach_struct_ops;
     link->fd = map->fd;
 
     return link;
 }
 
 typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr,
                               void *private_data);
 
 static enum bpf_perf_event_ret
 perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
                void **copy_mem, size_t *copy_size,
                bpf_perf_event_print_t fn, void *private_data)
 {
     struct perf_event_mmap_page *header = mmap_mem;
     __u64 data_head = ring_buffer_read_head(header);
     __u64 data_tail = header->data_tail;
     void *base = ((__u8 *)header) + page_size;
     int ret = LIBBPF_PERF_EVENT_CONT;
     struct perf_event_header *ehdr;
     size_t ehdr_size;
 
     while (data_head != data_tail) {
         ehdr = base + (data_tail & (mmap_size - 1));
         ehdr_size = ehdr->size;
 
         if (((void *)ehdr) + ehdr_size > base + mmap_size) {
             void *copy_start = ehdr;
             size_t len_first = base + mmap_size - copy_start;
             size_t len_secnd = ehdr_size - len_first;
 
             if (*copy_size < ehdr_size) {
                 free(*copy_mem);
                 *copy_mem = malloc(ehdr_size);
                 if (!*copy_mem) {
                     *copy_size = 0;
                     ret = LIBBPF_PERF_EVENT_ERROR;
                     break;
                 }
                 *copy_size = ehdr_size;
             }
 
             memcpy(*copy_mem, copy_start, len_first);
             memcpy(*copy_mem + len_first, base, len_secnd);
             ehdr = *copy_mem;
         }
 
         ret = fn(ehdr, private_data);
         data_tail += ehdr_size;
         if (ret != LIBBPF_PERF_EVENT_CONT)
             break;
     }
 
     ring_buffer_write_tail(header, data_tail);
     return libbpf_err(ret);
 }
 
 struct perf_buffer;
 
 struct perf_buffer_params {
     struct perf_event_attr *attr;
     /* if event_cb is specified, it takes precendence */
     perf_buffer_event_fn event_cb;
     /* sample_cb and lost_cb are higher-level common-case callbacks */
     perf_buffer_sample_fn sample_cb;
     perf_buffer_lost_fn lost_cb;
     void *ctx;
     int cpu_cnt;
     int *cpus;
     int *map_keys;
 };
 
 struct perf_cpu_buf {
     struct perf_buffer *pb;
     void *base; /* mmap()'ed memory */
     void *buf; /* for reconstructing segmented data */
     size_t buf_size;
     int fd;
     int cpu;
     int map_key;
 };
 
 struct perf_buffer {
     perf_buffer_event_fn event_cb;
     perf_buffer_sample_fn sample_cb;
     perf_buffer_lost_fn lost_cb;
     void *ctx; /* passed into callbacks */
 
     size_t page_size;
     size_t mmap_size;
     struct perf_cpu_buf **cpu_bufs;
     struct epoll_event *events;
     int cpu_cnt; /* number of allocated CPU buffers */
     int epoll_fd; /* perf event FD */
     int map_fd; /* BPF_MAP_TYPE_PERF_EVENT_ARRAY BPF map FD */
 };
 
 static void perf_buffer__free_cpu_buf(struct perf_buffer *pb,
                       struct perf_cpu_buf *cpu_buf)
 {
     if (!cpu_buf)
         return;
     if (cpu_buf->base &&
         munmap(cpu_buf->base, pb->mmap_size + pb->page_size))
         pr_warn("failed to munmap cpu_buf #%d\n", cpu_buf->cpu);
     if (cpu_buf->fd >= 0) {
         ioctl(cpu_buf->fd, PERF_EVENT_IOC_DISABLE, 0);
         close(cpu_buf->fd);
     }
     free(cpu_buf->buf);
     free(cpu_buf);
 }
 
 void perf_buffer__free(struct perf_buffer *pb)
 {
     int i;
 
     if (IS_ERR_OR_NULL(pb))
         return;
     if (pb->cpu_bufs) {
         for (i = 0; i < pb->cpu_cnt; i++) {
             struct perf_cpu_buf *cpu_buf = pb->cpu_bufs[i];
 
             if (!cpu_buf)
                 continue;
 
             bpf_map_delete_elem(pb->map_fd, &cpu_buf->map_key);
             perf_buffer__free_cpu_buf(pb, cpu_buf);
         }
         free(pb->cpu_bufs);
     }
     if (pb->epoll_fd >= 0)
         close(pb->epoll_fd);
     free(pb->events);
     free(pb);
 }
 
 static struct perf_cpu_buf *
 perf_buffer__open_cpu_buf(struct perf_buffer *pb, struct perf_event_attr *attr,
               int cpu, int map_key)
 {
     struct perf_cpu_buf *cpu_buf;
     char msg[STRERR_BUFSIZE];
     int err;
 
     cpu_buf = calloc(1, sizeof(*cpu_buf));
     if (!cpu_buf)
         return ERR_PTR(-ENOMEM);
 
     cpu_buf->pb = pb;
     cpu_buf->cpu = cpu;
     cpu_buf->map_key = map_key;
 
     cpu_buf->fd = syscall(__NR_perf_event_open, attr, -1 /* pid */, cpu,
                   -1, PERF_FLAG_FD_CLOEXEC);
     if (cpu_buf->fd < 0) {
         err = -errno;
         pr_warn("failed to open perf buffer event on cpu #%d: %s\n",
             cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
         goto error;
     }
 
     cpu_buf->base = mmap(NULL, pb->mmap_size + pb->page_size,
                  PROT_READ | PROT_WRITE, MAP_SHARED,
                  cpu_buf->fd, 0);
     if (cpu_buf->base == MAP_FAILED) {
         cpu_buf->base = NULL;
         err = -errno;
         pr_warn("failed to mmap perf buffer on cpu #%d: %s\n",
             cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
         goto error;
     }
 
     if (ioctl(cpu_buf->fd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
         err = -errno;
         pr_warn("failed to enable perf buffer event on cpu #%d: %s\n",
             cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
         goto error;
     }
 
     return cpu_buf;
 
 error:
     perf_buffer__free_cpu_buf(pb, cpu_buf);
     return (struct perf_cpu_buf *)ERR_PTR(err);
 }
 
 static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
                           struct perf_buffer_params *p);
 
 struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
                      perf_buffer_sample_fn sample_cb,
                      perf_buffer_lost_fn lost_cb,
                      void *ctx,
                      const struct perf_buffer_opts *opts)
 {
     struct perf_buffer_params p = {};
     struct perf_event_attr attr = {};
 
     if (!OPTS_VALID(opts, perf_buffer_opts))
         return libbpf_err_ptr(-EINVAL);
 
     attr.config = PERF_COUNT_SW_BPF_OUTPUT;
     attr.type = PERF_TYPE_SOFTWARE;
     attr.sample_type = PERF_SAMPLE_RAW;
     attr.sample_period = 1;
     attr.wakeup_events = 1;
 
     p.attr = &attr;
     p.sample_cb = sample_cb;
     p.lost_cb = lost_cb;
     p.ctx = ctx;
 
     return libbpf_ptr(__perf_buffer__new(map_fd, page_cnt, &p));
 }
 
 struct perf_buffer *perf_buffer__new_raw(int map_fd, size_t page_cnt,
                      struct perf_event_attr *attr,
                      perf_buffer_event_fn event_cb, void *ctx,
                      const struct perf_buffer_raw_opts *opts)
 {
     struct perf_buffer_params p = {};
 
     if (!attr)
         return libbpf_err_ptr(-EINVAL);
 
     if (!OPTS_VALID(opts, perf_buffer_raw_opts))
         return libbpf_err_ptr(-EINVAL);
 
     p.attr = attr;
     p.event_cb = event_cb;
     p.ctx = ctx;
     p.cpu_cnt = OPTS_GET(opts, cpu_cnt, 0);
     p.cpus = OPTS_GET(opts, cpus, NULL);
     p.map_keys = OPTS_GET(opts, map_keys, NULL);
 
     return libbpf_ptr(__perf_buffer__new(map_fd, page_cnt, &p));
 }
 
 static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
                           struct perf_buffer_params *p)
 {
     const char *online_cpus_file = "/sys/devices/system/cpu/online";
     struct bpf_map_info map;
     char msg[STRERR_BUFSIZE];
     struct perf_buffer *pb;
     bool *online = NULL;
     __u32 map_info_len;
     int err, i, j, n;
 
     if (page_cnt == 0 || (page_cnt & (page_cnt - 1))) {
         pr_warn("page count should be power of two, but is %zu\n",
             page_cnt);
         return ERR_PTR(-EINVAL);
     }
 
     /* best-effort sanity checks */
     memset(&map, 0, sizeof(map));
     map_info_len = sizeof(map);
     err = bpf_obj_get_info_by_fd(map_fd, &map, &map_info_len);
     if (err) {
         err = -errno;
         /* if BPF_OBJ_GET_INFO_BY_FD is supported, will return
          * -EBADFD, -EFAULT, or -E2BIG on real error
          */
         if (err != -EINVAL) {
             pr_warn("failed to get map info for map FD %d: %s\n",
                 map_fd, libbpf_strerror_r(err, msg, sizeof(msg)));
             return ERR_PTR(err);
         }
         pr_debug("failed to get map info for FD %d; API not supported? Ignoring...\n",
              map_fd);
     } else {
         if (map.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) {
             pr_warn("map '%s' should be BPF_MAP_TYPE_PERF_EVENT_ARRAY\n",
                 map.name);
             return ERR_PTR(-EINVAL);
         }
     }
 
     pb = calloc(1, sizeof(*pb));
     if (!pb)
         return ERR_PTR(-ENOMEM);
 
     pb->event_cb = p->event_cb;
     pb->sample_cb = p->sample_cb;
     pb->lost_cb = p->lost_cb;
     pb->ctx = p->ctx;
 
     pb->page_size = getpagesize();
     pb->mmap_size = pb->page_size * page_cnt;
     pb->map_fd = map_fd;
 
     pb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
     if (pb->epoll_fd < 0) {
         err = -errno;
         pr_warn("failed to create epoll instance: %s\n",
             libbpf_strerror_r(err, msg, sizeof(msg)));
         goto error;
     }
 
     if (p->cpu_cnt > 0) {
         pb->cpu_cnt = p->cpu_cnt;
     } else {
         pb->cpu_cnt = libbpf_num_possible_cpus();
         if (pb->cpu_cnt < 0) {
             err = pb->cpu_cnt;
             goto error;
         }
         if (map.max_entries && map.max_entries < pb->cpu_cnt)
             pb->cpu_cnt = map.max_entries;
     }
 
     pb->events = calloc(pb->cpu_cnt, sizeof(*pb->events));
     if (!pb->events) {
         err = -ENOMEM;
         pr_warn("failed to allocate events: out of memory\n");
         goto error;
     }
     pb->cpu_bufs = calloc(pb->cpu_cnt, sizeof(*pb->cpu_bufs));
     if (!pb->cpu_bufs) {
         err = -ENOMEM;
         pr_warn("failed to allocate buffers: out of memory\n");
         goto error;
     }
 
     err = parse_cpu_mask_file(online_cpus_file, &online, &n);
     if (err) {
         pr_warn("failed to get online CPU mask: %d\n", err);
         goto error;
     }
 
     for (i = 0, j = 0; i < pb->cpu_cnt; i++) {
         struct perf_cpu_buf *cpu_buf;
         int cpu, map_key;
 
         cpu = p->cpu_cnt > 0 ? p->cpus[i] : i;
         map_key = p->cpu_cnt > 0 ? p->map_keys[i] : i;
 
         /* in case user didn't explicitly requested particular CPUs to
          * be attached to, skip offline/not present CPUs
          */
         if (p->cpu_cnt <= 0 && (cpu >= n || !online[cpu]))
             continue;
 
         cpu_buf = perf_buffer__open_cpu_buf(pb, p->attr, cpu, map_key);
         if (IS_ERR(cpu_buf)) {
             err = PTR_ERR(cpu_buf);
             goto error;
         }
 
         pb->cpu_bufs[j] = cpu_buf;
 
         err = bpf_map_update_elem(pb->map_fd, &map_key,
                       &cpu_buf->fd, 0);
         if (err) {
             err = -errno;
             pr_warn("failed to set cpu #%d, key %d -> perf FD %d: %s\n",
                 cpu, map_key, cpu_buf->fd,
                 libbpf_strerror_r(err, msg, sizeof(msg)));
             goto error;
         }
 
         pb->events[j].events = EPOLLIN;
         pb->events[j].data.ptr = cpu_buf;
         if (epoll_ctl(pb->epoll_fd, EPOLL_CTL_ADD, cpu_buf->fd,
                   &pb->events[j]) < 0) {
             err = -errno;
             pr_warn("failed to epoll_ctl cpu #%d perf FD %d: %s\n",
                 cpu, cpu_buf->fd,
                 libbpf_strerror_r(err, msg, sizeof(msg)));
             goto error;
         }
         j++;
     }
     pb->cpu_cnt = j;
     free(online);
 
     return pb;
 
 error:
     free(online);
     if (pb)
         perf_buffer__free(pb);
     return ERR_PTR(err);
 }
 
 struct perf_sample_raw {
     struct perf_event_header header;
     uint32_t size;
     char data[];
 };
 
 struct perf_sample_lost {
     struct perf_event_header header;
     uint64_t id;
     uint64_t lost;
     uint64_t sample_id;
 };
 
 static enum bpf_perf_event_ret
 perf_buffer__process_record(struct perf_event_header *e, void *ctx)
 {
     struct perf_cpu_buf *cpu_buf = ctx;
     struct perf_buffer *pb = cpu_buf->pb;
     void *data = e;
 
     /* user wants full control over parsing perf event */
     if (pb->event_cb)
         return pb->event_cb(pb->ctx, cpu_buf->cpu, e);
 
     switch (e->type) {
     case PERF_RECORD_SAMPLE: {
         struct perf_sample_raw *s = data;
 
         if (pb->sample_cb)
             pb->sample_cb(pb->ctx, cpu_buf->cpu, s->data, s->size);
         break;
     }
     case PERF_RECORD_LOST: {
         struct perf_sample_lost *s = data;
 
         if (pb->lost_cb)
             pb->lost_cb(pb->ctx, cpu_buf->cpu, s->lost);
         break;
     }
     default:
         pr_warn("unknown perf sample type %d\n", e->type);
         return LIBBPF_PERF_EVENT_ERROR;
     }
     return LIBBPF_PERF_EVENT_CONT;
 }
 
 static int perf_buffer__process_records(struct perf_buffer *pb,
                     struct perf_cpu_buf *cpu_buf)
 {
     enum bpf_perf_event_ret ret;
 
     ret = perf_event_read_simple(cpu_buf->base, pb->mmap_size,
                      pb->page_size, &cpu_buf->buf,
                      &cpu_buf->buf_size,
                      perf_buffer__process_record, cpu_buf);
     if (ret != LIBBPF_PERF_EVENT_CONT)
         return ret;
     return 0;
 }
 
 int perf_buffer__epoll_fd(const struct perf_buffer *pb)
 {
     return pb->epoll_fd;
 }
 
 int perf_buffer__poll(struct perf_buffer *pb, int timeout_ms)
 {
     int i, cnt, err;
 
     cnt = epoll_wait(pb->epoll_fd, pb->events, pb->cpu_cnt, timeout_ms);
     if (cnt < 0)
         return -errno;
 
     for (i = 0; i < cnt; i++) {
         struct perf_cpu_buf *cpu_buf = pb->events[i].data.ptr;
 
         err = perf_buffer__process_records(pb, cpu_buf);
         if (err) {
             pr_warn("error while processing records: %d\n", err);
             return libbpf_err(err);
         }
     }
     return cnt;
 }
 
 /* Return number of PERF_EVENT_ARRAY map slots set up by this perf_buffer
  * manager.
  */
 size_t perf_buffer__buffer_cnt(const struct perf_buffer *pb)
 {
     return pb->cpu_cnt;
 }
 
 /*
  * Return perf_event FD of a ring buffer in *buf_idx* slot of
  * PERF_EVENT_ARRAY BPF map. This FD can be polled for new data using
  * select()/poll()/epoll() Linux syscalls.
  */
 int perf_buffer__buffer_fd(const struct perf_buffer *pb, size_t buf_idx)
 {
     struct perf_cpu_buf *cpu_buf;
 
     if (buf_idx >= pb->cpu_cnt)
         return libbpf_err(-EINVAL);
 
     cpu_buf = pb->cpu_bufs[buf_idx];
     if (!cpu_buf)
         return libbpf_err(-ENOENT);
 
     return cpu_buf->fd;
 }
 
 int perf_buffer__buffer(struct perf_buffer *pb, int buf_idx, void **buf, size_t *buf_size)
 {
     struct perf_cpu_buf *cpu_buf;
 
     if (buf_idx >= pb->cpu_cnt)
         return libbpf_err(-EINVAL);
 
     cpu_buf = pb->cpu_bufs[buf_idx];
     if (!cpu_buf)
         return libbpf_err(-ENOENT);
 
     *buf = cpu_buf->base;
     *buf_size = pb->mmap_size;
     return 0;
 }
 
 /*
  * Consume data from perf ring buffer corresponding to slot *buf_idx* in
  * PERF_EVENT_ARRAY BPF map without waiting/polling. If there is no data to
  * consume, do nothing and return success.
  * Returns:
  *   - 0 on success;
  *   - <0 on failure.
  */
 int perf_buffer__consume_buffer(struct perf_buffer *pb, size_t buf_idx)
 {
     struct perf_cpu_buf *cpu_buf;
 
     if (buf_idx >= pb->cpu_cnt)
         return libbpf_err(-EINVAL);
 
     cpu_buf = pb->cpu_bufs[buf_idx];
     if (!cpu_buf)
         return libbpf_err(-ENOENT);
 
     return perf_buffer__process_records(pb, cpu_buf);
 }
 
 int perf_buffer__consume(struct perf_buffer *pb)
 {
     int i, err;
 
     for (i = 0; i < pb->cpu_cnt; i++) {
         struct perf_cpu_buf *cpu_buf = pb->cpu_bufs[i];
 
         if (!cpu_buf)
             continue;
 
         err = perf_buffer__process_records(pb, cpu_buf);
         if (err) {
             pr_warn("perf_buffer: failed to process records in buffer #%d: %d\n", i, err);
             return libbpf_err(err);
         }
     }
     return 0;
 }
 
 int bpf_program__set_attach_target(struct bpf_program *prog,
                    int attach_prog_fd,
                    const char *attach_func_name)
 {
     int btf_obj_fd = 0, btf_id = 0, err;
 
     if (!prog || attach_prog_fd < 0)
         return libbpf_err(-EINVAL);
 
     if (prog->obj->loaded)
         return libbpf_err(-EINVAL);
 
     if (attach_prog_fd && !attach_func_name) {
         /* remember attach_prog_fd and let bpf_program__load() find
          * BTF ID during the program load
          */
         prog->attach_prog_fd = attach_prog_fd;
         return 0;
     }
 
     if (attach_prog_fd) {
         btf_id = libbpf_find_prog_btf_id(attach_func_name,
                          attach_prog_fd);
         if (btf_id < 0)
             return libbpf_err(btf_id);
     } else {
         if (!attach_func_name)
             return libbpf_err(-EINVAL);
 
         /* load btf_vmlinux, if not yet */
         err = bpf_object__load_vmlinux_btf(prog->obj, true);
         if (err)
             return libbpf_err(err);
         err = find_kernel_btf_id(prog->obj, attach_func_name,
                      prog->expected_attach_type,
                      &btf_obj_fd, &btf_id);
         if (err)
             return libbpf_err(err);
     }
 
     prog->attach_btf_id = btf_id;
     prog->attach_btf_obj_fd = btf_obj_fd;
     prog->attach_prog_fd = attach_prog_fd;
     return 0;
 }
 
 int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
 {
     int err = 0, n, len, start, end = -1;
     bool *tmp;
 
     *mask = NULL;
     *mask_sz = 0;
 
     /* Each sub string separated by ',' has format \d+-\d+ or \d+ */
     while (*s) {
         if (*s == ',' || *s == '\n') {
             s++;
             continue;
         }
         n = sscanf(s, "%d%n-%d%n", &start, &len, &end, &len);
         if (n <= 0 || n > 2) {
             pr_warn("Failed to get CPU range %s: %d\n", s, n);
             err = -EINVAL;
             goto cleanup;
         } else if (n == 1) {
             end = start;
         }
         if (start < 0 || start > end) {
             pr_warn("Invalid CPU range [%d,%d] in %s\n",
                 start, end, s);
             err = -EINVAL;
             goto cleanup;
         }
         tmp = realloc(*mask, end + 1);
         if (!tmp) {
             err = -ENOMEM;
             goto cleanup;
         }
         *mask = tmp;
         memset(tmp + *mask_sz, 0, start - *mask_sz);
         memset(tmp + start, 1, end - start + 1);
         *mask_sz = end + 1;
         s += len;
     }
     if (!*mask_sz) {
         pr_warn("Empty CPU range\n");
         return -EINVAL;
     }
     return 0;
 cleanup:
     free(*mask);
     *mask = NULL;
     return err;
 }
 
 int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz)
 {
     int fd, err = 0, len;
     char buf[128];
 
     fd = open(fcpu, O_RDONLY | O_CLOEXEC);
     if (fd < 0) {
         err = -errno;
         pr_warn("Failed to open cpu mask file %s: %d\n", fcpu, err);
         return err;
     }
     len = read(fd, buf, sizeof(buf));
     close(fd);
     if (len <= 0) {
         err = len ? -errno : -EINVAL;
         pr_warn("Failed to read cpu mask from %s: %d\n", fcpu, err);
         return err;
     }
     if (len >= sizeof(buf)) {
         pr_warn("CPU mask is too big in file %s\n", fcpu);
         return -E2BIG;
     }
     buf[len] = '\0';
 
     return parse_cpu_mask_str(buf, mask, mask_sz);
 }
 
 int libbpf_num_possible_cpus(void)
 {
     static const char *fcpu = "/sys/devices/system/cpu/possible";
     static int cpus;
     int err, n, i, tmp_cpus;
     bool *mask;
 
     tmp_cpus = READ_ONCE(cpus);
     if (tmp_cpus > 0)
         return tmp_cpus;
 
     err = parse_cpu_mask_file(fcpu, &mask, &n);
     if (err)
         return libbpf_err(err);
 
     tmp_cpus = 0;
     for (i = 0; i < n; i++) {
         if (mask[i])
             tmp_cpus++;
     }
     free(mask);
 
     WRITE_ONCE(cpus, tmp_cpus);
     return tmp_cpus;
 }
 
 static int populate_skeleton_maps(const struct bpf_object *obj,
                   struct bpf_map_skeleton *maps,
                   size_t map_cnt)
 {
     int i;
 
     for (i = 0; i < map_cnt; i++) {
         struct bpf_map **map = maps[i].map;
         const char *name = maps[i].name;
         void **mmaped = maps[i].mmaped;
 
         *map = bpf_object__find_map_by_name(obj, name);
         if (!*map) {
             pr_warn("failed to find skeleton map '%s'\n", name);
             return -ESRCH;
         }
 
         /* externs shouldn't be pre-setup from user code */
         if (mmaped && (*map)->libbpf_type != LIBBPF_MAP_KCONFIG)
             *mmaped = (*map)->mmaped;
     }
     return 0;
 }
 
 static int populate_skeleton_progs(const struct bpf_object *obj,
                    struct bpf_prog_skeleton *progs,
                    size_t prog_cnt)
 {
     int i;
 
     for (i = 0; i < prog_cnt; i++) {
         struct bpf_program **prog = progs[i].prog;
         const char *name = progs[i].name;
 
         *prog = bpf_object__find_program_by_name(obj, name);
         if (!*prog) {
             pr_warn("failed to find skeleton program '%s'\n", name);
             return -ESRCH;
         }
     }
     return 0;
 }
 
 int bpf_object__open_skeleton(struct bpf_object_skeleton *s,
                   const struct bpf_object_open_opts *opts)
 {
     DECLARE_LIBBPF_OPTS(bpf_object_open_opts, skel_opts,
         .object_name = s->name,
     );
     struct bpf_object *obj;
     int err;
 
     /* Attempt to preserve opts->object_name, unless overriden by user
      * explicitly. Overwriting object name for skeletons is discouraged,
      * as it breaks global data maps, because they contain object name
      * prefix as their own map name prefix. When skeleton is generated,
      * bpftool is making an assumption that this name will stay the same.
      */
     if (opts) {
         memcpy(&skel_opts, opts, sizeof(*opts));
         if (!opts->object_name)
             skel_opts.object_name = s->name;
     }
 
     obj = bpf_object__open_mem(s->data, s->data_sz, &skel_opts);
     err = libbpf_get_error(obj);
     if (err) {
         pr_warn("failed to initialize skeleton BPF object '%s': %d\n",
             s->name, err);
         return libbpf_err(err);
     }
 
     *s->obj = obj;
     err = populate_skeleton_maps(obj, s->maps, s->map_cnt);
     if (err) {
         pr_warn("failed to populate skeleton maps for '%s': %d\n", s->name, err);
         return libbpf_err(err);
     }
 
     err = populate_skeleton_progs(obj, s->progs, s->prog_cnt);
     if (err) {
         pr_warn("failed to populate skeleton progs for '%s': %d\n", s->name, err);
         return libbpf_err(err);
     }
 
     return 0;
 }
 
 int bpf_object__open_subskeleton(struct bpf_object_subskeleton *s)
 {
     int err, len, var_idx, i;
     const char *var_name;
     const struct bpf_map *map;
     struct btf *btf;
     __u32 map_type_id;
     const struct btf_type *map_type, *var_type;
     const struct bpf_var_skeleton *var_skel;
     struct btf_var_secinfo *var;
 
     if (!s->obj)
         return libbpf_err(-EINVAL);
 
     btf = bpf_object__btf(s->obj);
     if (!btf) {
         pr_warn("subskeletons require BTF at runtime (object %s)\n",
                 bpf_object__name(s->obj));
         return libbpf_err(-errno);
     }
 
     err = populate_skeleton_maps(s->obj, s->maps, s->map_cnt);
     if (err) {
         pr_warn("failed to populate subskeleton maps: %d\n", err);
         return libbpf_err(err);
     }
 
     err = populate_skeleton_progs(s->obj, s->progs, s->prog_cnt);
     if (err) {
         pr_warn("failed to populate subskeleton maps: %d\n", err);
         return libbpf_err(err);
     }
 
     for (var_idx = 0; var_idx < s->var_cnt; var_idx++) {
         var_skel = &s->vars[var_idx];
         map = *var_skel->map;
         map_type_id = bpf_map__btf_value_type_id(map);
         map_type = btf__type_by_id(btf, map_type_id);
 
         if (!btf_is_datasec(map_type)) {
             pr_warn("type for map '%1$s' is not a datasec: %2$s",
                 bpf_map__name(map),
                 __btf_kind_str(btf_kind(map_type)));
             return libbpf_err(-EINVAL);
         }
 
         len = btf_vlen(map_type);
         var = btf_var_secinfos(map_type);
         for (i = 0; i < len; i++, var++) {
             var_type = btf__type_by_id(btf, var->type);
             var_name = btf__name_by_offset(btf, var_type->name_off);
             if (strcmp(var_name, var_skel->name) == 0) {
                 *var_skel->addr = map->mmaped + var->offset;
                 break;
             }
         }
     }
     return 0;
 }
 
 void bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s)
 {
     if (!s)
         return;
     free(s->maps);
     free(s->progs);
     free(s->vars);
     free(s);
 }
 
 int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
 {
     int i, err;
 
     err = bpf_object__load(*s->obj);
     if (err) {
         pr_warn("failed to load BPF skeleton '%s': %d\n", s->name, err);
         return libbpf_err(err);
     }
 
     for (i = 0; i < s->map_cnt; i++) {
         struct bpf_map *map = *s->maps[i].map;
         size_t mmap_sz = bpf_map_mmap_sz(map);
         int prot, map_fd = bpf_map__fd(map);
         void **mmaped = s->maps[i].mmaped;
 
         if (!mmaped)
             continue;
 
         if (!(map->def.map_flags & BPF_F_MMAPABLE)) {
             *mmaped = NULL;
             continue;
         }
 
         if (map->def.map_flags & BPF_F_RDONLY_PROG)
             prot = PROT_READ;
         else
             prot = PROT_READ | PROT_WRITE;
 
         /* Remap anonymous mmap()-ed "map initialization image" as
          * a BPF map-backed mmap()-ed memory, but preserving the same
          * memory address. This will cause kernel to change process'
          * page table to point to a different piece of kernel memory,
          * but from userspace point of view memory address (and its
          * contents, being identical at this point) will stay the
          * same. This mapping will be released by bpf_object__close()
          * as per normal clean up procedure, so we don't need to worry
          * about it from skeleton's clean up perspective.
          */
         *mmaped = mmap(map->mmaped, mmap_sz, prot,
                 MAP_SHARED | MAP_FIXED, map_fd, 0);
         if (*mmaped == MAP_FAILED) {
             err = -errno;
             *mmaped = NULL;
             pr_warn("failed to re-mmap() map '%s': %d\n",
                  bpf_map__name(map), err);
             return libbpf_err(err);
         }
     }
 
     return 0;
 }
 
 int bpf_object__attach_skeleton(struct bpf_object_skeleton *s)
 {
     int i, err;
 
     for (i = 0; i < s->prog_cnt; i++) {
         struct bpf_program *prog = *s->progs[i].prog;
         struct bpf_link **link = s->progs[i].link;
 
         if (!prog->autoload)
             continue;
 
         /* auto-attaching not supported for this program */
         if (!prog->sec_def || !prog->sec_def->prog_attach_fn)
             continue;
 
         /* if user already set the link manually, don't attempt auto-attach */
         if (*link)
             continue;
 
         err = prog->sec_def->prog_attach_fn(prog, prog->sec_def->cookie, link);
         if (err) {
             pr_warn("prog '%s': failed to auto-attach: %d\n",
                 bpf_program__name(prog), err);
             return libbpf_err(err);
         }
 
         /* It's possible that for some SEC() definitions auto-attach
          * is supported in some cases (e.g., if definition completely
          * specifies target information), but is not in other cases.
          * SEC("uprobe") is one such case. If user specified target
          * binary and function name, such BPF program can be
          * auto-attached. But if not, it shouldn't trigger skeleton's
          * attach to fail. It should just be skipped.
          * attach_fn signals such case with returning 0 (no error) and
          * setting link to NULL.
          */
     }
 
     return 0;
 }
 
 void bpf_object__detach_skeleton(struct bpf_object_skeleton *s)
 {
     int i;
 
     for (i = 0; i < s->prog_cnt; i++) {
         struct bpf_link **link = s->progs[i].link;
 
         bpf_link__destroy(*link);
         *link = NULL;
     }
 }
 
 void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s)
 {
     if (!s)
         return;
 
     if (s->progs)
         bpf_object__detach_skeleton(s);
     if (s->obj)
         bpf_object__close(*s->obj);
     free(s->maps);
     free(s->progs);
     free(s);
 }