lib/bpf/libbpf_probes.c

0001 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
0002 /* Copyright (c) 2019 Netronome Systems, Inc. */
0003
0004 #include <errno.h>
0005 #include <fcntl.h>
0006 #include <string.h>
0007 #include <stdlib.h>
0008 #include <unistd.h>
0009 #include <net/if.h>
0010 #include <sys/utsname.h>
0011
0012 #include <linux/btf.h>
0013 #include <linux/filter.h>
0014 #include <linux/kernel.h>
0015
0016 #include "bpf.h"
0017 #include "libbpf.h"
0018 #include "libbpf_internal.h"
0019
0020 static int probe_prog_load(enum bpf_prog_type prog_type,
0021                const struct bpf_insn *insns, size_t insns_cnt,
0022                char *log_buf, size_t log_buf_sz)
0023 {
0024     LIBBPF_OPTS(bpf_prog_load_opts, opts,
0025         .log_buf = log_buf,
0026         .log_size = log_buf_sz,
0027         .log_level = log_buf ? 1 : 0,
0028     );
0029     int fd, err, exp_err = 0;
0030     const char *exp_msg = NULL;
0031     char buf[4096];
0032
0033     switch (prog_type) {
0034     case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
0035         opts.expected_attach_type = BPF_CGROUP_INET4_CONNECT;
0036         break;
0037     case BPF_PROG_TYPE_CGROUP_SOCKOPT:
0038         opts.expected_attach_type = BPF_CGROUP_GETSOCKOPT;
0039         break;
0040     case BPF_PROG_TYPE_SK_LOOKUP:
0041         opts.expected_attach_type = BPF_SK_LOOKUP;
0042         break;
0043     case BPF_PROG_TYPE_KPROBE:
0044         opts.kern_version = get_kernel_version();
0045         break;
0046     case BPF_PROG_TYPE_LIRC_MODE2:
0047         opts.expected_attach_type = BPF_LIRC_MODE2;
0048         break;
0049     case BPF_PROG_TYPE_TRACING:
0050     case BPF_PROG_TYPE_LSM:
0051         opts.log_buf = buf;
0052         opts.log_size = sizeof(buf);
0053         opts.log_level = 1;
0054         if (prog_type == BPF_PROG_TYPE_TRACING)
0055             opts.expected_attach_type = BPF_TRACE_FENTRY;
0056         else
0057             opts.expected_attach_type = BPF_MODIFY_RETURN;
0058         opts.attach_btf_id = 1;
0059
0060         exp_err = -EINVAL;
0061         exp_msg = "attach_btf_id 1 is not a function";
0062         break;
0063     case BPF_PROG_TYPE_EXT:
0064         opts.log_buf = buf;
0065         opts.log_size = sizeof(buf);
0066         opts.log_level = 1;
0067         opts.attach_btf_id = 1;
0068
0069         exp_err = -EINVAL;
0070         exp_msg = "Cannot replace kernel functions";
0071         break;
0072     case BPF_PROG_TYPE_SYSCALL:
0073         opts.prog_flags = BPF_F_SLEEPABLE;
0074         break;
0075     case BPF_PROG_TYPE_STRUCT_OPS:
0076         exp_err = -524; /* -ENOTSUPP */
0077         break;
0078     case BPF_PROG_TYPE_UNSPEC:
0079     case BPF_PROG_TYPE_SOCKET_FILTER:
0080     case BPF_PROG_TYPE_SCHED_CLS:
0081     case BPF_PROG_TYPE_SCHED_ACT:
0082     case BPF_PROG_TYPE_TRACEPOINT:
0083     case BPF_PROG_TYPE_XDP:
0084     case BPF_PROG_TYPE_PERF_EVENT:
0085     case BPF_PROG_TYPE_CGROUP_SKB:
0086     case BPF_PROG_TYPE_CGROUP_SOCK:
0087     case BPF_PROG_TYPE_LWT_IN:
0088     case BPF_PROG_TYPE_LWT_OUT:
0089     case BPF_PROG_TYPE_LWT_XMIT:
0090     case BPF_PROG_TYPE_SOCK_OPS:
0091     case BPF_PROG_TYPE_SK_SKB:
0092     case BPF_PROG_TYPE_CGROUP_DEVICE:
0093     case BPF_PROG_TYPE_SK_MSG:
0094     case BPF_PROG_TYPE_RAW_TRACEPOINT:
0095     case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
0096     case BPF_PROG_TYPE_LWT_SEG6LOCAL:
0097     case BPF_PROG_TYPE_SK_REUSEPORT:
0098     case BPF_PROG_TYPE_FLOW_DISSECTOR:
0099     case BPF_PROG_TYPE_CGROUP_SYSCTL:
0100         break;
0101     default:
0102         return -EOPNOTSUPP;
0103     }
0104
0105     fd = bpf_prog_load(prog_type, NULL, "GPL", insns, insns_cnt, &opts);
0106     err = -errno;
0107     if (fd >= 0)
0108         close(fd);
0109     if (exp_err) {
0110         if (fd >= 0 || err != exp_err)
0111             return 0;
0112         if (exp_msg && !strstr(buf, exp_msg))
0113             return 0;
0114         return 1;
0115     }
0116     return fd >= 0 ? 1 : 0;
0117 }
0118
0119 int libbpf_probe_bpf_prog_type(enum bpf_prog_type prog_type, const void *opts)
0120 {
0121     struct bpf_insn insns[] = {
0122         BPF_MOV64_IMM(BPF_REG_0, 0),
0123         BPF_EXIT_INSN()
0124     };
0125     const size_t insn_cnt = ARRAY_SIZE(insns);
0126     int ret;
0127
0128     if (opts)
0129         return libbpf_err(-EINVAL);
0130
0131     ret = probe_prog_load(prog_type, insns, insn_cnt, NULL, 0);
0132     return libbpf_err(ret);
0133 }
0134
0135 int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
0136              const char *str_sec, size_t str_len)
0137 {
0138     struct btf_header hdr = {
0139         .magic = BTF_MAGIC,
0140         .version = BTF_VERSION,
0141         .hdr_len = sizeof(struct btf_header),
0142         .type_len = types_len,
0143         .str_off = types_len,
0144         .str_len = str_len,
0145     };
0146     int btf_fd, btf_len;
0147     __u8 *raw_btf;
0148
0149     btf_len = hdr.hdr_len + hdr.type_len + hdr.str_len;
0150     raw_btf = malloc(btf_len);
0151     if (!raw_btf)
0152         return -ENOMEM;
0153
0154     memcpy(raw_btf, &hdr, sizeof(hdr));
0155     memcpy(raw_btf + hdr.hdr_len, raw_types, hdr.type_len);
0156     memcpy(raw_btf + hdr.hdr_len + hdr.type_len, str_sec, hdr.str_len);
0157
0158     btf_fd = bpf_btf_load(raw_btf, btf_len, NULL);
0159
0160     free(raw_btf);
0161     return btf_fd;
0162 }
0163
0164 static int load_local_storage_btf(void)
0165 {
0166     const char strs[] = "\0bpf_spin_lock\0val\0cnt\0l";
0167     /* struct bpf_spin_lock {
0168      *   int val;
0169      * };
0170      * struct val {
0171      *   int cnt;
0172      *   struct bpf_spin_lock l;
0173      * };
0174      */
0175     __u32 types[] = {
0176         /* int */
0177         BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
0178         /* struct bpf_spin_lock */                      /* [2] */
0179         BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 4),
0180         BTF_MEMBER_ENC(15, 1, 0), /* int val; */
0181         /* struct val */                                /* [3] */
0182         BTF_TYPE_ENC(15, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 8),
0183         BTF_MEMBER_ENC(19, 1, 0), /* int cnt; */
0184         BTF_MEMBER_ENC(23, 2, 32),/* struct bpf_spin_lock l; */
0185     };
0186
0187     return libbpf__load_raw_btf((char *)types, sizeof(types),
0188                      strs, sizeof(strs));
0189 }
0190
0191 static int probe_map_create(enum bpf_map_type map_type)
0192 {
0193     LIBBPF_OPTS(bpf_map_create_opts, opts);
0194     int key_size, value_size, max_entries;
0195     __u32 btf_key_type_id = 0, btf_value_type_id = 0;
0196     int fd = -1, btf_fd = -1, fd_inner = -1, exp_err = 0, err;
0197
0198     key_size    = sizeof(__u32);
0199     value_size  = sizeof(__u32);
0200     max_entries = 1;
0201
0202     switch (map_type) {
0203     case BPF_MAP_TYPE_STACK_TRACE:
0204         value_size  = sizeof(__u64);
0205         break;
0206     case BPF_MAP_TYPE_LPM_TRIE:
0207         key_size    = sizeof(__u64);
0208         value_size  = sizeof(__u64);
0209         opts.map_flags  = BPF_F_NO_PREALLOC;
0210         break;
0211     case BPF_MAP_TYPE_CGROUP_STORAGE:
0212     case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE:
0213         key_size    = sizeof(struct bpf_cgroup_storage_key);
0214         value_size  = sizeof(__u64);
0215         max_entries = 0;
0216         break;
0217     case BPF_MAP_TYPE_QUEUE:
0218     case BPF_MAP_TYPE_STACK:
0219         key_size    = 0;
0220         break;
0221     case BPF_MAP_TYPE_SK_STORAGE:
0222     case BPF_MAP_TYPE_INODE_STORAGE:
0223     case BPF_MAP_TYPE_TASK_STORAGE:
0224         btf_key_type_id = 1;
0225         btf_value_type_id = 3;
0226         value_size = 8;
0227         max_entries = 0;
0228         opts.map_flags = BPF_F_NO_PREALLOC;
0229         btf_fd = load_local_storage_btf();
0230         if (btf_fd < 0)
0231             return btf_fd;
0232         break;
0233     case BPF_MAP_TYPE_RINGBUF:
0234         key_size = 0;
0235         value_size = 0;
0236         max_entries = 4096;
0237         break;
0238     case BPF_MAP_TYPE_STRUCT_OPS:
0239         /* we'll get -ENOTSUPP for invalid BTF type ID for struct_ops */
0240         opts.btf_vmlinux_value_type_id = 1;
0241         exp_err = -524; /* -ENOTSUPP */
0242         break;
0243     case BPF_MAP_TYPE_BLOOM_FILTER:
0244         key_size = 0;
0245         max_entries = 1;
0246         break;
0247     case BPF_MAP_TYPE_HASH:
0248     case BPF_MAP_TYPE_ARRAY:
0249     case BPF_MAP_TYPE_PROG_ARRAY:
0250     case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
0251     case BPF_MAP_TYPE_PERCPU_HASH:
0252     case BPF_MAP_TYPE_PERCPU_ARRAY:
0253     case BPF_MAP_TYPE_CGROUP_ARRAY:
0254     case BPF_MAP_TYPE_LRU_HASH:
0255     case BPF_MAP_TYPE_LRU_PERCPU_HASH:
0256     case BPF_MAP_TYPE_ARRAY_OF_MAPS:
0257     case BPF_MAP_TYPE_HASH_OF_MAPS:
0258     case BPF_MAP_TYPE_DEVMAP:
0259     case BPF_MAP_TYPE_DEVMAP_HASH:
0260     case BPF_MAP_TYPE_SOCKMAP:
0261     case BPF_MAP_TYPE_CPUMAP:
0262     case BPF_MAP_TYPE_XSKMAP:
0263     case BPF_MAP_TYPE_SOCKHASH:
0264     case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
0265         break;
0266     case BPF_MAP_TYPE_UNSPEC:
0267     default:
0268         return -EOPNOTSUPP;
0269     }
0270
0271     if (map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
0272         map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
0273         fd_inner = bpf_map_create(BPF_MAP_TYPE_HASH, NULL,
0274                       sizeof(__u32), sizeof(__u32), 1, NULL);
0275         if (fd_inner < 0)
0276             goto cleanup;
0277
0278         opts.inner_map_fd = fd_inner;
0279     }
0280
0281     if (btf_fd >= 0) {
0282         opts.btf_fd = btf_fd;
0283         opts.btf_key_type_id = btf_key_type_id;
0284         opts.btf_value_type_id = btf_value_type_id;
0285     }
0286
0287     fd = bpf_map_create(map_type, NULL, key_size, value_size, max_entries, &opts);
0288     err = -errno;
0289
0290 cleanup:
0291     if (fd >= 0)
0292         close(fd);
0293     if (fd_inner >= 0)
0294         close(fd_inner);
0295     if (btf_fd >= 0)
0296         close(btf_fd);
0297
0298     if (exp_err)
0299         return fd < 0 && err == exp_err ? 1 : 0;
0300     else
0301         return fd >= 0 ? 1 : 0;
0302 }
0303
0304 int libbpf_probe_bpf_map_type(enum bpf_map_type map_type, const void *opts)
0305 {
0306     int ret;
0307
0308     if (opts)
0309         return libbpf_err(-EINVAL);
0310
0311     ret = probe_map_create(map_type);
0312     return libbpf_err(ret);
0313 }
0314
0315 int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,
0316                 const void *opts)
0317 {
0318     struct bpf_insn insns[] = {
0319         BPF_EMIT_CALL((__u32)helper_id),
0320         BPF_EXIT_INSN(),
0321     };
0322     const size_t insn_cnt = ARRAY_SIZE(insns);
0323     char buf[4096];
0324     int ret;
0325
0326     if (opts)
0327         return libbpf_err(-EINVAL);
0328
0329     /* we can't successfully load all prog types to check for BPF helper
0330      * support, so bail out with -EOPNOTSUPP error
0331      */
0332     switch (prog_type) {
0333     case BPF_PROG_TYPE_TRACING:
0334     case BPF_PROG_TYPE_EXT:
0335     case BPF_PROG_TYPE_LSM:
0336     case BPF_PROG_TYPE_STRUCT_OPS:
0337         return -EOPNOTSUPP;
0338     default:
0339         break;
0340     }
0341
0342     buf[0] = '\0';
0343     ret = probe_prog_load(prog_type, insns, insn_cnt, buf, sizeof(buf));
0344     if (ret < 0)
0345         return libbpf_err(ret);
0346
0347     /* If BPF verifier doesn't recognize BPF helper ID (enum bpf_func_id)
0348      * at all, it will emit something like "invalid func unknown#181".
0349      * If BPF verifier recognizes BPF helper but it's not supported for
0350      * given BPF program type, it will emit "unknown func bpf_sys_bpf#166".
0351      * In both cases, provided combination of BPF program type and BPF
0352      * helper is not supported by the kernel.
0353      * In all other cases, probe_prog_load() above will either succeed (e.g.,
0354      * because BPF helper happens to accept no input arguments or it
0355      * accepts one input argument and initial PTR_TO_CTX is fine for
0356      * that), or we'll get some more specific BPF verifier error about
0357      * some unsatisfied conditions.
0358      */
0359     if (ret == 0 && (strstr(buf, "invalid func ") || strstr(buf, "unknown func ")))
0360         return 0;
0361     return 1; /* assume supported */
0362 }