elf/dl-addr.c

   1 /* Locate the shared object symbol nearest a given address.
   2    Copyright (C) 1996-2000,2001,2002,2003 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   /* Find the highest-addressed object that ADDRESS is not below.  */
  37   match = NULL;
  38   for (l = GL(dl_loaded); l; l = l->l_next)
  39     if (addr >= l->l_map_start && addr < l->l_map_end)
  40       {
  41         /* We know ADDRESS lies within L if in any shared object.
  42            Make sure it isn't past the end of L's segments.  */
  43         size_t n = l->l_phnum;
  44         if (n > 0)
  45           {
  46             do
  47               --n;
  48             while (l->l_phdr[n].p_type != PT_LOAD);
  49             if (addr >= (l->l_addr +
  50                          l->l_phdr[n].p_vaddr + l->l_phdr[n].p_memsz))
  51               /* Off the end of the highest-addressed shared object.  */
  52               continue;
  53           }
  54
  55         match = l;
  56         break;
  57       }
  58
  59   if (match == NULL)
  60     return 0;
  61
  62   /* Now we know what object the address lies in.  */
  63   info->dli_fname = match->l_name;
  64   info->dli_fbase = (void *) match->l_map_start;
  65
  66   /* If this is the main program the information is incomplete.  */
  67   if (__builtin_expect (l->l_name[0], 'a') == '\0'
  68       && l->l_type == lt_executable)
  69     info->dli_fname = _dl_argv[0];
  70
  71   symtab = (const void *) D_PTR (match, l_info[DT_SYMTAB]);
  72   strtab = (const void *) D_PTR (match, l_info[DT_STRTAB]);
  73
  74   strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
  75
  76   if (match->l_info[DT_HASH] != NULL)
  77     symtabend = symtab + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1];
  78   else
  79     /* There is no direct way to determine the number of symbols in the
  80        dynamic symbol table and no hash table is present.  The ELF
  81        binary is ill-formed but what shall we do?  Use the beginning of
  82        the string table which generally follows the symbol table.  */
  83     symtabend = (const ElfW(Sym) *) strtab;
  84
  85   /* We assume that the string table follows the symbol table, because
  86      there is no way in ELF to know the size of the dynamic symbol table!!  */
  87   for (matchsym = NULL; (void *) symtab < (void *) symtabend; ++symtab)
  88     if (addr >= match->l_addr + symtab->st_value
  89         && ((symtab->st_size == 0 && addr == match->l_addr + symtab->st_value)
  90             || addr < match->l_addr + symtab->st_value + symtab->st_size)
  91         && symtab->st_name < strtabsize
  92         && (matchsym == NULL || matchsym->st_value < symtab->st_value)
  93         && (ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
  94             || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK))
  95       matchsym = (ElfW(Sym) *) symtab;
  96
  97   if (mapp)
  98     *mapp = match;
  99   if (symbolp)
 100     *symbolp = matchsym;
 101
 102   if (matchsym)
 103     {
 104       /* We found a symbol close by.  Fill in its name and exact address.  */
 105       info->dli_sname = strtab + matchsym->st_name;
 106       info->dli_saddr = (void *) (match->l_addr + matchsym->st_value);
 107     }
 108   else
 109     {
 110       /* No symbol matches.  We return only the containing object.  */
 111       info->dli_sname = NULL;
 112       info->dli_saddr = NULL;
 113     }
 114
 115   return 1;
 116 }
 117 libc_hidden_def (_dl_addr)