elf/dl-addr.c

   1 /* Locate the shared object symbol nearest a given address.
   2    Copyright (C) 1996-2003, 2004   Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <dlfcn.h>
  21 #include <stddef.h>
  22 #include <ldsodefs.h>
  23
  24
  25 int
  26 internal_function
  27 _dl_addr (const void *address, Dl_info *info,
  28           struct link_map **mapp, const ElfW(Sym) **symbolp)
  29 {
  30   const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
  31   struct link_map *l, *match;
  32   const ElfW(Sym) *symtab, *matchsym, *symtabend;
  33   const char *strtab;
  34   ElfW(Word) strtabsize;
  35
  36   /* Protect against concurrent loads and unloads.  */
  37   __rtld_lock_lock_recursive (GL(dl_load_lock));
  38
  39   /* Find the highest-addressed object that ADDRESS is not below.  */
  40   match = NULL;
  41   for (l = GL(dl_loaded); l; l = l->l_next)
  42     if (addr >= l->l_map_start && addr < l->l_map_end)
  43       {
  44         /* We know ADDRESS lies within L if in any shared object.
  45            Make sure it isn't past the end of L's segments.  */
  46         size_t n = l->l_phnum;
  47         if (n > 0)
  48           {
  49             do
  50               --n;
  51             while (l->l_phdr[n].p_type != PT_LOAD);
  52             if (addr >= (l->l_addr +
  53                          l->l_phdr[n].p_vaddr + l->l_phdr[n].p_memsz))
  54               /* Off the end of the highest-addressed shared object.  */
  55               continue;
  56           }
  57
  58         match = l;
  59         break;
  60       }
  61
  62   int result = 0;
  63   if (match != NULL)
  64     {
  65       /* Now we know what object the address lies in.  */
  66       info->dli_fname = match->l_name;
  67       info->dli_fbase = (void *) match->l_map_start;
  68
  69       /* If this is the main program the information is incomplete.  */
  70       if (__builtin_expect (l->l_name[0], 'a') == '\0'
  71           && l->l_type == lt_executable)
  72         info->dli_fname = _dl_argv[0];
  73
  74       symtab = (const void *) D_PTR (match, l_info[DT_SYMTAB]);
  75       strtab = (const void *) D_PTR (match, l_info[DT_STRTAB]);
  76
  77       strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
  78
  79       if (match->l_info[DT_HASH] != NULL)
  80         symtabend = (symtab
  81                      + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
  82       else
  83         /* There is no direct way to determine the number of symbols in the
  84            dynamic symbol table and no hash table is present.  The ELF
  85            binary is ill-formed but what shall we do?  Use the beginning of
  86            the string table which generally follows the symbol table.  */
  87         symtabend = (const ElfW(Sym) *) strtab;
  88
  89       /* We assume that the string table follows the symbol table,
  90          because there is no way in ELF to know the size of the
  91          dynamic symbol table!!  */
  92       for (matchsym = NULL; (void *) symtab < (void *) symtabend; ++symtab)
  93         if (addr >= match->l_addr + symtab->st_value
  94             && ((symtab->st_size == 0
  95                  && addr == match->l_addr + symtab->st_value)
  96                 || addr < match->l_addr + symtab->st_value + symtab->st_size)
  97             && symtab->st_name < strtabsize
  98             && (matchsym == NULL || matchsym->st_value < symtab->st_value)
  99             && (ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
 100                 || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK))
 101           matchsym = (ElfW(Sym) *) symtab;
 102
 103       if (mapp)
 104         *mapp = match;
 105       if (symbolp)
 106         *symbolp = matchsym;
 107
 108       if (matchsym)
 109         {
 110           /* We found a symbol close by.  Fill in its name and exact
 111              address.  */
 112           info->dli_sname = strtab + matchsym->st_name;
 113           info->dli_saddr = (void *) (match->l_addr + matchsym->st_value);
 114         }
 115       else
 116         {
 117           /* No symbol matches.  We return only the containing object.  */
 118           info->dli_sname = NULL;
 119           info->dli_saddr = NULL;
 120         }
 121
 122       result = 1;
 123     }
 124
 125   __rtld_lock_unlock_recursive (GL(dl_load_lock));
 126
 127   return result;
 128 }
 129 libc_hidden_def (_dl_addr)