elf/dl-addr.c

   1 /* Locate the shared object symbol nearest a given address.
   2    Copyright (C) 1996-2000, 2001, 2002 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 {
  29   const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
  30   struct link_map *l, *match;
  31   const ElfW(Sym) *symtab, *matchsym;
  32   const char *strtab;
  33   ElfW(Word) strtabsize;
  34
  35   /* Find the highest-addressed object that ADDRESS is not below.  */
  36   match = NULL;
  37   for (l = GL(dl_loaded); l; l = l->l_next)
  38     if (addr >= l->l_map_start && addr < l->l_map_end)
  39       {
  40         /* We know ADDRESS lies within L if in any shared object.
  41            Make sure it isn't past the end of L's segments.  */
  42         size_t n = l->l_phnum;
  43         if (n > 0)
  44           {
  45             do
  46               --n;
  47             while (l->l_phdr[n].p_type != PT_LOAD);
  48             if (addr >= (l->l_addr +
  49                          l->l_phdr[n].p_vaddr + l->l_phdr[n].p_memsz))
  50               /* Off the end of the highest-addressed shared object.  */
  51               continue;
  52           }
  53
  54         match = l;
  55         break;
  56       }
  57
  58   if (match == NULL)
  59     return 0;
  60
  61   /* Now we know what object the address lies in.  */
  62   info->dli_fname = match->l_name;
  63   info->dli_fbase = (void *) match->l_addr;
  64
  65   /* If this is the main program the information is incomplete.  */
  66   if (__builtin_expect (info->dli_fbase == NULL, 0))
  67     {
  68       info->dli_fname = _dl_argv[0];
  69       info->dli_fbase = (void *) match->l_map_start;
  70     }
  71
  72   symtab = (const void *) D_PTR (match, l_info[DT_SYMTAB]);
  73   strtab = (const void *) D_PTR (match, l_info[DT_STRTAB]);
  74   strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
  75
  76   /* We assume that the string table follows the symbol table, because
  77      there is no way in ELF to know the size of the dynamic symbol table!!  */
  78   for (matchsym = NULL; (void *) symtab < (void *) strtab; ++symtab)
  79     if (addr >= match->l_addr + symtab->st_value
  80         && ((symtab->st_size == 0 && addr == match->l_addr + symtab->st_value)
  81             || addr < match->l_addr + symtab->st_value + symtab->st_size)
  82         && symtab->st_name < strtabsize
  83         && (matchsym == NULL || matchsym->st_value < symtab->st_value)
  84         && (ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
  85             || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK))
  86       matchsym = symtab;
  87
  88   if (matchsym)
  89     {
  90       /* We found a symbol close by.  Fill in its name and exact address.  */
  91       info->dli_sname = strtab + matchsym->st_name;
  92       info->dli_saddr = (void *) (match->l_addr + matchsym->st_value);
  93     }
  94   else
  95     {
  96       /* No symbol matches.  We return only the containing object.  */
  97       info->dli_sname = NULL;
  98       info->dli_saddr = NULL;
  99     }
 100
 101   return 1;
 102 }