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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
  *
  * Rewritten and vastly simplified by Rusty Russell for in-kernel
  * module loader:
  *   Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
  *
  * ChangeLog:
  *
  * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
  *      Changed the compression method from stem compression to "table lookup"
  *      compression (see scripts/kallsyms.c for a more complete description)
  */
 #include <linux/kallsyms.h>
 #include <linux/init.h>
 #include <linux/seq_file.h>
 #include <linux/fs.h>
 #include <linux/kdb.h>
 #include <linux/err.h>
 #include <linux/proc_fs.h>
 #include <linux/sched.h>    /* for cond_resched */
 #include <linux/ctype.h>
 #include <linux/slab.h>
 #include <linux/filter.h>
 #include <linux/ftrace.h>
 #include <linux/kprobes.h>
 #include <linux/build_bug.h>
 #include <linux/compiler.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/bsearch.h>
 #include <linux/btf_ids.h>
 
 #include "kallsyms_internal.h"
 
 /*
  * Expand a compressed symbol data into the resulting uncompressed string,
  * if uncompressed string is too long (>= maxlen), it will be truncated,
  * given the offset to where the symbol is in the compressed stream.
  */
 static unsigned int kallsyms_expand_symbol(unsigned int off,
                        char *result, size_t maxlen)
 {
     int len, skipped_first = 0;
     const char *tptr;
     const u8 *data;
 
     /* Get the compressed symbol length from the first symbol byte. */
     data = &kallsyms_names[off];
     len = *data;
     data++;
 
     /*
      * Update the offset to return the offset for the next symbol on
      * the compressed stream.
      */
     off += len + 1;
 
     /*
      * For every byte on the compressed symbol data, copy the table
      * entry for that byte.
      */
     while (len) {
         tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
         data++;
         len--;
 
         while (*tptr) {
             if (skipped_first) {
                 if (maxlen <= 1)
                     goto tail;
                 *result = *tptr;
                 result++;
                 maxlen--;
             } else
                 skipped_first = 1;
             tptr++;
         }
     }
 
 tail:
     if (maxlen)
         *result = '\0';
 
     /* Return to offset to the next symbol. */
     return off;
 }
 
 /*
  * Get symbol type information. This is encoded as a single char at the
  * beginning of the symbol name.
  */
 static char kallsyms_get_symbol_type(unsigned int off)
 {
     /*
      * Get just the first code, look it up in the token table,
      * and return the first char from this token.
      */
     return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
 }
 
 
 /*
  * Find the offset on the compressed stream given and index in the
  * kallsyms array.
  */
 static unsigned int get_symbol_offset(unsigned long pos)
 {
     const u8 *name;
     int i;
 
     /*
      * Use the closest marker we have. We have markers every 256 positions,
      * so that should be close enough.
      */
     name = &kallsyms_names[kallsyms_markers[pos >> 8]];
 
     /*
      * Sequentially scan all the symbols up to the point we're searching
      * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
      * so we just need to add the len to the current pointer for every
      * symbol we wish to skip.
      */
     for (i = 0; i < (pos & 0xFF); i++)
         name = name + (*name) + 1;
 
     return name - kallsyms_names;
 }
 
 static unsigned long kallsyms_sym_address(int idx)
 {
     if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
         return kallsyms_addresses[idx];
 
     /* values are unsigned offsets if --absolute-percpu is not in effect */
     if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
         return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
 
     /* ...otherwise, positive offsets are absolute values */
     if (kallsyms_offsets[idx] >= 0)
         return kallsyms_offsets[idx];
 
     /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
     return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
 }
 
 static bool cleanup_symbol_name(char *s)
 {
     char *res;
 
     if (!IS_ENABLED(CONFIG_LTO_CLANG))
         return false;
 
     /*
      * LLVM appends various suffixes for local functions and variables that
      * must be promoted to global scope as part of LTO.  This can break
      * hooking of static functions with kprobes. '.' is not a valid
      * character in an identifier in C. Suffixes observed:
      * - foo.llvm.[0-9a-f]+
      * - foo.[0-9a-f]+
      * - foo.[0-9a-f]+.cfi_jt
      */
     res = strchr(s, '.');
     if (res) {
         *res = '\0';
         return true;
     }
 
     if (!IS_ENABLED(CONFIG_CFI_CLANG) ||
         !IS_ENABLED(CONFIG_LTO_CLANG_THIN) ||
         CONFIG_CLANG_VERSION >= 130000)
         return false;
 
     /*
      * Prior to LLVM 13, the following suffixes were observed when thinLTO
      * and CFI are both enabled:
      * - foo$[0-9]+
      */
     res = strrchr(s, '$');
     if (res) {
         *res = '\0';
         return true;
     }
 
     return false;
 }
 
 /* Lookup the address for this symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name)
 {
     char namebuf[KSYM_NAME_LEN];
     unsigned long i;
     unsigned int off;
 
     /* Skip the search for empty string. */
     if (!*name)
         return 0;
 
     for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
         off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 
         if (strcmp(namebuf, name) == 0)
             return kallsyms_sym_address(i);
 
         if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
             return kallsyms_sym_address(i);
     }
     return module_kallsyms_lookup_name(name);
 }
 
 /*
  * Iterate over all symbols in vmlinux.  For symbols from modules use
  * module_kallsyms_on_each_symbol instead.
  */
 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
                       unsigned long),
                 void *data)
 {
     char namebuf[KSYM_NAME_LEN];
     unsigned long i;
     unsigned int off;
     int ret;
 
     for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
         off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
         ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
         if (ret != 0)
             return ret;
         cond_resched();
     }
     return 0;
 }
 
 static unsigned long get_symbol_pos(unsigned long addr,
                     unsigned long *symbolsize,
                     unsigned long *offset)
 {
     unsigned long symbol_start = 0, symbol_end = 0;
     unsigned long i, low, high, mid;
 
     /* This kernel should never had been booted. */
     if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
         BUG_ON(!kallsyms_addresses);
     else
         BUG_ON(!kallsyms_offsets);
 
     /* Do a binary search on the sorted kallsyms_addresses array. */
     low = 0;
     high = kallsyms_num_syms;
 
     while (high - low > 1) {
         mid = low + (high - low) / 2;
         if (kallsyms_sym_address(mid) <= addr)
             low = mid;
         else
             high = mid;
     }
 
     /*
      * Search for the first aliased symbol. Aliased
      * symbols are symbols with the same address.
      */
     while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
         --low;
 
     symbol_start = kallsyms_sym_address(low);
 
     /* Search for next non-aliased symbol. */
     for (i = low + 1; i < kallsyms_num_syms; i++) {
         if (kallsyms_sym_address(i) > symbol_start) {
             symbol_end = kallsyms_sym_address(i);
             break;
         }
     }
 
     /* If we found no next symbol, we use the end of the section. */
     if (!symbol_end) {
         if (is_kernel_inittext(addr))
             symbol_end = (unsigned long)_einittext;
         else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
             symbol_end = (unsigned long)_end;
         else
             symbol_end = (unsigned long)_etext;
     }
 
     if (symbolsize)
         *symbolsize = symbol_end - symbol_start;
     if (offset)
         *offset = addr - symbol_start;
 
     return low;
 }
 
 /*
  * Lookup an address but don't bother to find any names.
  */
 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
                 unsigned long *offset)
 {
     char namebuf[KSYM_NAME_LEN];
 
     if (is_ksym_addr(addr)) {
         get_symbol_pos(addr, symbolsize, offset);
         return 1;
     }
     return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
            !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
 }
 
 static const char *kallsyms_lookup_buildid(unsigned long addr,
             unsigned long *symbolsize,
             unsigned long *offset, char **modname,
             const unsigned char **modbuildid, char *namebuf)
 {
     const char *ret;
 
     namebuf[KSYM_NAME_LEN - 1] = 0;
     namebuf[0] = 0;
 
     if (is_ksym_addr(addr)) {
         unsigned long pos;
 
         pos = get_symbol_pos(addr, symbolsize, offset);
         /* Grab name */
         kallsyms_expand_symbol(get_symbol_offset(pos),
                        namebuf, KSYM_NAME_LEN);
         if (modname)
             *modname = NULL;
         if (modbuildid)
             *modbuildid = NULL;
 
         ret = namebuf;
         goto found;
     }
 
     /* See if it's in a module or a BPF JITed image. */
     ret = module_address_lookup(addr, symbolsize, offset,
                     modname, modbuildid, namebuf);
     if (!ret)
         ret = bpf_address_lookup(addr, symbolsize,
                      offset, modname, namebuf);
 
     if (!ret)
         ret = ftrace_mod_address_lookup(addr, symbolsize,
                         offset, modname, namebuf);
 
 found:
     cleanup_symbol_name(namebuf);
     return ret;
 }
 
 /*
  * Lookup an address
  * - modname is set to NULL if it's in the kernel.
  * - We guarantee that the returned name is valid until we reschedule even if.
  *   It resides in a module.
  * - We also guarantee that modname will be valid until rescheduled.
  */
 const char *kallsyms_lookup(unsigned long addr,
                 unsigned long *symbolsize,
                 unsigned long *offset,
                 char **modname, char *namebuf)
 {
     return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
                        NULL, namebuf);
 }
 
 int lookup_symbol_name(unsigned long addr, char *symname)
 {
     int res;
 
     symname[0] = '\0';
     symname[KSYM_NAME_LEN - 1] = '\0';
 
     if (is_ksym_addr(addr)) {
         unsigned long pos;
 
         pos = get_symbol_pos(addr, NULL, NULL);
         /* Grab name */
         kallsyms_expand_symbol(get_symbol_offset(pos),
                        symname, KSYM_NAME_LEN);
         goto found;
     }
     /* See if it's in a module. */
     res = lookup_module_symbol_name(addr, symname);
     if (res)
         return res;
 
 found:
     cleanup_symbol_name(symname);
     return 0;
 }
 
 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
             unsigned long *offset, char *modname, char *name)
 {
     int res;
 
     name[0] = '\0';
     name[KSYM_NAME_LEN - 1] = '\0';
 
     if (is_ksym_addr(addr)) {
         unsigned long pos;
 
         pos = get_symbol_pos(addr, size, offset);
         /* Grab name */
         kallsyms_expand_symbol(get_symbol_offset(pos),
                        name, KSYM_NAME_LEN);
         modname[0] = '\0';
         goto found;
     }
     /* See if it's in a module. */
     res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
     if (res)
         return res;
 
 found:
     cleanup_symbol_name(name);
     return 0;
 }
 
 /* Look up a kernel symbol and return it in a text buffer. */
 static int __sprint_symbol(char *buffer, unsigned long address,
                int symbol_offset, int add_offset, int add_buildid)
 {
     char *modname;
     const unsigned char *buildid;
     const char *name;
     unsigned long offset, size;
     int len;
 
     address += symbol_offset;
     name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
                        buffer);
     if (!name)
         return sprintf(buffer, "0x%lx", address - symbol_offset);
 
     if (name != buffer)
         strcpy(buffer, name);
     len = strlen(buffer);
     offset -= symbol_offset;
 
     if (add_offset)
         len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
 
     if (modname) {
         len += sprintf(buffer + len, " [%s", modname);
 #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
         if (add_buildid && buildid) {
             /* build ID should match length of sprintf */
 #if IS_ENABLED(CONFIG_MODULES)
             static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
 #endif
             len += sprintf(buffer + len, " %20phN", buildid);
         }
 #endif
         len += sprintf(buffer + len, "]");
     }
 
     return len;
 }
 
 /**
  * sprint_symbol - Look up a kernel symbol and return it in a text buffer
  * @buffer: buffer to be stored
  * @address: address to lookup
  *
  * This function looks up a kernel symbol with @address and stores its name,
  * offset, size and module name to @buffer if possible. If no symbol was found,
  * just saves its @address as is.
  *
  * This function returns the number of bytes stored in @buffer.
  */
 int sprint_symbol(char *buffer, unsigned long address)
 {
     return __sprint_symbol(buffer, address, 0, 1, 0);
 }
 EXPORT_SYMBOL_GPL(sprint_symbol);
 
 /**
  * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
  * @buffer: buffer to be stored
  * @address: address to lookup
  *
  * This function looks up a kernel symbol with @address and stores its name,
  * offset, size, module name and module build ID to @buffer if possible. If no
  * symbol was found, just saves its @address as is.
  *
  * This function returns the number of bytes stored in @buffer.
  */
 int sprint_symbol_build_id(char *buffer, unsigned long address)
 {
     return __sprint_symbol(buffer, address, 0, 1, 1);
 }
 EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
 
 /**
  * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
  * @buffer: buffer to be stored
  * @address: address to lookup
  *
  * This function looks up a kernel symbol with @address and stores its name
  * and module name to @buffer if possible. If no symbol was found, just saves
  * its @address as is.
  *
  * This function returns the number of bytes stored in @buffer.
  */
 int sprint_symbol_no_offset(char *buffer, unsigned long address)
 {
     return __sprint_symbol(buffer, address, 0, 0, 0);
 }
 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
 
 /**
  * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
  * @buffer: buffer to be stored
  * @address: address to lookup
  *
  * This function is for stack backtrace and does the same thing as
  * sprint_symbol() but with modified/decreased @address. If there is a
  * tail-call to the function marked "noreturn", gcc optimized out code after
  * the call so that the stack-saved return address could point outside of the
  * caller. This function ensures that kallsyms will find the original caller
  * by decreasing @address.
  *
  * This function returns the number of bytes stored in @buffer.
  */
 int sprint_backtrace(char *buffer, unsigned long address)
 {
     return __sprint_symbol(buffer, address, -1, 1, 0);
 }
 
 /**
  * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
  * @buffer: buffer to be stored
  * @address: address to lookup
  *
  * This function is for stack backtrace and does the same thing as
  * sprint_symbol() but with modified/decreased @address. If there is a
  * tail-call to the function marked "noreturn", gcc optimized out code after
  * the call so that the stack-saved return address could point outside of the
  * caller. This function ensures that kallsyms will find the original caller
  * by decreasing @address. This function also appends the module build ID to
  * the @buffer if @address is within a kernel module.
  *
  * This function returns the number of bytes stored in @buffer.
  */
 int sprint_backtrace_build_id(char *buffer, unsigned long address)
 {
     return __sprint_symbol(buffer, address, -1, 1, 1);
 }
 
 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 struct kallsym_iter {
     loff_t pos;
     loff_t pos_arch_end;
     loff_t pos_mod_end;
     loff_t pos_ftrace_mod_end;
     loff_t pos_bpf_end;
     unsigned long value;
     unsigned int nameoff; /* If iterating in core kernel symbols. */
     char type;
     char name[KSYM_NAME_LEN];
     char module_name[MODULE_NAME_LEN];
     int exported;
     int show_value;
 };
 
 int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
                 char *type, char *name)
 {
     return -EINVAL;
 }
 
 static int get_ksymbol_arch(struct kallsym_iter *iter)
 {
     int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
                    &iter->value, &iter->type,
                    iter->name);
 
     if (ret < 0) {
         iter->pos_arch_end = iter->pos;
         return 0;
     }
 
     return 1;
 }
 
 static int get_ksymbol_mod(struct kallsym_iter *iter)
 {
     int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
                      &iter->value, &iter->type,
                      iter->name, iter->module_name,
                      &iter->exported);
     if (ret < 0) {
         iter->pos_mod_end = iter->pos;
         return 0;
     }
 
     return 1;
 }
 
 /*
  * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
  * purposes. In that case "__builtin__ftrace" is used as a module name, even
  * though "__builtin__ftrace" is not a module.
  */
 static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
 {
     int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
                      &iter->value, &iter->type,
                      iter->name, iter->module_name,
                      &iter->exported);
     if (ret < 0) {
         iter->pos_ftrace_mod_end = iter->pos;
         return 0;
     }
 
     return 1;
 }
 
 static int get_ksymbol_bpf(struct kallsym_iter *iter)
 {
     int ret;
 
     strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
     iter->exported = 0;
     ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
                   &iter->value, &iter->type,
                   iter->name);
     if (ret < 0) {
         iter->pos_bpf_end = iter->pos;
         return 0;
     }
 
     return 1;
 }
 
 /*
  * This uses "__builtin__kprobes" as a module name for symbols for pages
  * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
  * module.
  */
 static int get_ksymbol_kprobe(struct kallsym_iter *iter)
 {
     strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
     iter->exported = 0;
     return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
                   &iter->value, &iter->type,
                   iter->name) < 0 ? 0 : 1;
 }
 
 /* Returns space to next name. */
 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 {
     unsigned off = iter->nameoff;
 
     iter->module_name[0] = '\0';
     iter->value = kallsyms_sym_address(iter->pos);
 
     iter->type = kallsyms_get_symbol_type(off);
 
     off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
 
     return off - iter->nameoff;
 }
 
 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 {
     iter->name[0] = '\0';
     iter->nameoff = get_symbol_offset(new_pos);
     iter->pos = new_pos;
     if (new_pos == 0) {
         iter->pos_arch_end = 0;
         iter->pos_mod_end = 0;
         iter->pos_ftrace_mod_end = 0;
         iter->pos_bpf_end = 0;
     }
 }
 
 /*
  * The end position (last + 1) of each additional kallsyms section is recorded
  * in iter->pos_..._end as each section is added, and so can be used to
  * determine which get_ksymbol_...() function to call next.
  */
 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
 {
     iter->pos = pos;
 
     if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
         get_ksymbol_arch(iter))
         return 1;
 
     if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
         get_ksymbol_mod(iter))
         return 1;
 
     if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
         get_ksymbol_ftrace_mod(iter))
         return 1;
 
     if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
         get_ksymbol_bpf(iter))
         return 1;
 
     return get_ksymbol_kprobe(iter);
 }
 
 /* Returns false if pos at or past end of file. */
 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 {
     /* Module symbols can be accessed randomly. */
     if (pos >= kallsyms_num_syms)
         return update_iter_mod(iter, pos);
 
     /* If we're not on the desired position, reset to new position. */
     if (pos != iter->pos)
         reset_iter(iter, pos);
 
     iter->nameoff += get_ksymbol_core(iter);
     iter->pos++;
 
     return 1;
 }
 
 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 {
     (*pos)++;
 
     if (!update_iter(m->private, *pos))
         return NULL;
     return p;
 }
 
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
     if (!update_iter(m->private, *pos))
         return NULL;
     return m->private;
 }
 
 static void s_stop(struct seq_file *m, void *p)
 {
 }
 
 static int s_show(struct seq_file *m, void *p)
 {
     void *value;
     struct kallsym_iter *iter = m->private;
 
     /* Some debugging symbols have no name.  Ignore them. */
     if (!iter->name[0])
         return 0;
 
     value = iter->show_value ? (void *)iter->value : NULL;
 
     if (iter->module_name[0]) {
         char type;
 
         /*
          * Label it "global" if it is exported,
          * "local" if not exported.
          */
         type = iter->exported ? toupper(iter->type) :
                     tolower(iter->type);
         seq_printf(m, "%px %c %s\t[%s]\n", value,
                type, iter->name, iter->module_name);
     } else
         seq_printf(m, "%px %c %s\n", value,
                iter->type, iter->name);
     return 0;
 }
 
 static const struct seq_operations kallsyms_op = {
     .start = s_start,
     .next = s_next,
     .stop = s_stop,
     .show = s_show
 };
 
 #ifdef CONFIG_BPF_SYSCALL
 
 struct bpf_iter__ksym {
     __bpf_md_ptr(struct bpf_iter_meta *, meta);
     __bpf_md_ptr(struct kallsym_iter *, ksym);
 };
 
 static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
 {
     struct bpf_iter__ksym ctx;
     struct bpf_iter_meta meta;
     struct bpf_prog *prog;
 
     meta.seq = m;
     prog = bpf_iter_get_info(&meta, in_stop);
     if (!prog)
         return 0;
 
     ctx.meta = &meta;
     ctx.ksym = m ? m->private : NULL;
     return bpf_iter_run_prog(prog, &ctx);
 }
 
 static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
 {
     return ksym_prog_seq_show(m, false);
 }
 
 static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
 {
     if (!p)
         (void) ksym_prog_seq_show(m, true);
     else
         s_stop(m, p);
 }
 
 static const struct seq_operations bpf_iter_ksym_ops = {
     .start = s_start,
     .next = s_next,
     .stop = bpf_iter_ksym_seq_stop,
     .show = bpf_iter_ksym_seq_show,
 };
 
 static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
 {
     struct kallsym_iter *iter = priv_data;
 
     reset_iter(iter, 0);
 
     /* cache here as in kallsyms_open() case; use current process
      * credentials to tell BPF iterators if values should be shown.
      */
     iter->show_value = kallsyms_show_value(current_cred());
 
     return 0;
 }
 
 DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
 
 static const struct bpf_iter_seq_info ksym_iter_seq_info = {
     .seq_ops        = &bpf_iter_ksym_ops,
     .init_seq_private   = bpf_iter_ksym_init,
     .fini_seq_private   = NULL,
     .seq_priv_size      = sizeof(struct kallsym_iter),
 };
 
 static struct bpf_iter_reg ksym_iter_reg_info = {
     .target                 = "ksym",
     .feature        = BPF_ITER_RESCHED,
     .ctx_arg_info_size  = 1,
     .ctx_arg_info       = {
         { offsetof(struct bpf_iter__ksym, ksym),
           PTR_TO_BTF_ID_OR_NULL },
     },
     .seq_info       = &ksym_iter_seq_info,
 };
 
 BTF_ID_LIST(btf_ksym_iter_id)
 BTF_ID(struct, kallsym_iter)
 
 static int __init bpf_ksym_iter_register(void)
 {
     ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
     return bpf_iter_reg_target(&ksym_iter_reg_info);
 }
 
 late_initcall(bpf_ksym_iter_register);
 
 #endif /* CONFIG_BPF_SYSCALL */
 
 static inline int kallsyms_for_perf(void)
 {
 #ifdef CONFIG_PERF_EVENTS
     extern int sysctl_perf_event_paranoid;
     if (sysctl_perf_event_paranoid <= 1)
         return 1;
 #endif
     return 0;
 }
 
 /*
  * We show kallsyms information even to normal users if we've enabled
  * kernel profiling and are explicitly not paranoid (so kptr_restrict
  * is clear, and sysctl_perf_event_paranoid isn't set).
  *
  * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
  * block even that).
  */
 bool kallsyms_show_value(const struct cred *cred)
 {
     switch (kptr_restrict) {
     case 0:
         if (kallsyms_for_perf())
             return true;
         fallthrough;
     case 1:
         if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
                      CAP_OPT_NOAUDIT) == 0)
             return true;
         fallthrough;
     default:
         return false;
     }
 }
 
 static int kallsyms_open(struct inode *inode, struct file *file)
 {
     /*
      * We keep iterator in m->private, since normal case is to
      * s_start from where we left off, so we avoid doing
      * using get_symbol_offset for every symbol.
      */
     struct kallsym_iter *iter;
     iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
     if (!iter)
         return -ENOMEM;
     reset_iter(iter, 0);
 
     /*
      * Instead of checking this on every s_show() call, cache
      * the result here at open time.
      */
     iter->show_value = kallsyms_show_value(file->f_cred);
     return 0;
 }
 
 #ifdef  CONFIG_KGDB_KDB
 const char *kdb_walk_kallsyms(loff_t *pos)
 {
     static struct kallsym_iter kdb_walk_kallsyms_iter;
     if (*pos == 0) {
         memset(&kdb_walk_kallsyms_iter, 0,
                sizeof(kdb_walk_kallsyms_iter));
         reset_iter(&kdb_walk_kallsyms_iter, 0);
     }
     while (1) {
         if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
             return NULL;
         ++*pos;
         /* Some debugging symbols have no name.  Ignore them. */
         if (kdb_walk_kallsyms_iter.name[0])
             return kdb_walk_kallsyms_iter.name;
     }
 }
 #endif  /* CONFIG_KGDB_KDB */
 
 static const struct proc_ops kallsyms_proc_ops = {
     .proc_open  = kallsyms_open,
     .proc_read  = seq_read,
     .proc_lseek = seq_lseek,
     .proc_release   = seq_release_private,
 };
 
 static int __init kallsyms_init(void)
 {
     proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
     return 0;
 }
 device_initcall(kallsyms_init);

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