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dl-addr.c

/* Locate the shared object symbol nearest a given address.
   Copyright (C) 1996-2004, 2005, 2006 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <dlfcn.h>
#include <stddef.h>
#include <ldsodefs.h>


int
internal_function
_dl_addr (const void *address, Dl_info *info,
        struct link_map **mapp, const ElfW(Sym) **symbolp)
{
  const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);

  /* Protect against concurrent loads and unloads.  */
  __rtld_lock_lock_recursive (GL(dl_load_lock));

  /* Find the highest-addressed object that ADDRESS is not below.  */
  struct link_map *match = NULL;
  for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
    for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l; l = l->l_next)
      if (addr >= l->l_map_start && addr < l->l_map_end)
      {
        /* We know ADDRESS lies within L if in any shared object.
           Make sure it isn't past the end of L's segments.  */
        size_t n = l->l_phnum;
        if (n > 0)
          {
            do
            --n;
            while (l->l_phdr[n].p_type != PT_LOAD);
            if (addr >= (l->l_addr +
                     l->l_phdr[n].p_vaddr + l->l_phdr[n].p_memsz))
            /* Off the end of the highest-addressed shared object.  */
            continue;
          }

        match = l;
        break;
      }

  int result = 0;
  if (match != NULL)
    {
      /* Now we know what object the address lies in.  */
      info->dli_fname = match->l_name;
      info->dli_fbase = (void *) match->l_map_start;

      /* If this is the main program the information is incomplete.  */
      if (__builtin_expect (match->l_name[0], 'a') == '\0'
        && match->l_type == lt_executable)
      info->dli_fname = _dl_argv[0];

      const ElfW(Sym) *symtab
      = (const ElfW(Sym) *) D_PTR (match, l_info[DT_SYMTAB]);
      const char *strtab = (const char *) D_PTR (match, l_info[DT_STRTAB]);

      ElfW(Word) strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;

      const ElfW(Sym) *matchsym = NULL;
      if (match->l_info[DT_ADDRTAGIDX (DT_GNU_HASH) + DT_NUM + DT_THISPROCNUM
                  + DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM] != NULL)
      {
        /* We look at all symbol table entries referenced by the
           hash table.  */
        for (Elf_Symndx bucket = 0; bucket < match->l_nbuckets; ++bucket)
          {
            Elf32_Word symndx = match->l_gnu_buckets[bucket];
            if (symndx != 0)
            {
              const Elf32_Word *hasharr = &match->l_gnu_chain_zero[symndx];

              do
                {
                  /* The hash table never references local symbols
                   so we can omit that test here.  */
                  if ((symtab[symndx].st_shndx != SHN_UNDEF
                     || symtab[symndx].st_value != 0)
#ifdef USE_TLS
                    && ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
#endif
                    && DL_ADDR_SYM_MATCH (match, &symtab[symndx],
                                    matchsym, addr)
                    && symtab[symndx].st_name < strtabsize)
                  matchsym = (ElfW(Sym) *) &symtab[symndx];

                  ++symndx;
                }
              while ((*hasharr++ & 1u) == 0);
            }
          }
      }
      else
      {
        const ElfW(Sym) *symtabend;
        if (match->l_info[DT_HASH] != NULL)
          symtabend = (symtab
                   + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
        else
          /* There is no direct way to determine the number of symbols in the
             dynamic symbol table and no hash table is present.  The ELF
             binary is ill-formed but what shall we do?  Use the beginning of
             the string table which generally follows the symbol table.  */
          symtabend = (const ElfW(Sym) *) strtab;

        for (; (void *) symtab < (void *) symtabend; ++symtab)
          if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
             || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
#ifdef USE_TLS
            && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
#endif
            && (symtab->st_shndx != SHN_UNDEF
                || symtab->st_value != 0)
            && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
            && symtab->st_name < strtabsize)
            matchsym = (ElfW(Sym) *) symtab;
      }

      if (mapp)
      *mapp = match;
      if (symbolp)
      *symbolp = matchsym;

      if (matchsym)
      {
        /* We found a symbol close by.  Fill in its name and exact
           address.  */
        lookup_t matchl = LOOKUP_VALUE (match);

        info->dli_sname = strtab + matchsym->st_name;
        info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
      }
      else
      {
        /* No symbol matches.  We return only the containing object.  */
        info->dli_sname = NULL;
        info->dli_saddr = NULL;
      }

      result = 1;
    }

  __rtld_lock_unlock_recursive (GL(dl_load_lock));

  return result;
}
libc_hidden_def (_dl_addr)

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