elf/dladdr.c

   1 /* dladdr -- Locate the shared object symbol nearest a given address.
   2    Copyright (C) 1996, 1998 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <stddef.h>
  21 #include <link.h>
  22 #include <dlfcn.h>
  23
  24
  25 int
  26 dladdr (void *address, Dl_info *info)
  27 {
  28   const ElfW(Addr) addr = (ElfW(Addr)) address;
  29   struct link_map *l, *match;
  30   const ElfW(Sym) *symtab, *matchsym;
  31   const char *strtab;
  32
  33   /* Find the highest-addressed object that ADDRESS is not below.  */
  34   match = NULL;
  35   for (l = _dl_loaded; l; l = l->l_next)
  36     if (addr >= l->l_addr && (!match || match->l_addr < l->l_addr))
  37       match = l;
  38
  39   if (match)
  40     {
  41       /* We know ADDRESS lies within MATCH if in any shared object.
  42          Make sure it isn't past the end of MATCH's segments.  */
  43       size_t n = match->l_phnum;
  44       if (n > 0)
  45         {
  46           do
  47             --n;
  48           while (match->l_phdr[n].p_type != PT_LOAD);
  49           if (addr >= (match->l_addr +
  50                        match->l_phdr[n].p_vaddr + match->l_phdr[n].p_memsz))
  51             /* Off the end of the highest-addressed shared object.  */
  52             return 0;
  53         }
  54     }
  55   else
  56     return 0;
  57
  58   /* Now we know what object the address lies in.  */
  59   info->dli_fname = match->l_name;
  60   info->dli_fbase = (void *) match->l_addr;
  61
  62   symtab = ((void *) match->l_addr + match->l_info[DT_SYMTAB]->d_un.d_ptr);
  63   strtab = ((void *) match->l_addr + match->l_info[DT_STRTAB]->d_un.d_ptr);
  64
  65   /* We assume that the string table follows the symbol table, because
  66      there is no way in ELF to know the size of the dynamic symbol table!!  */
  67   for (matchsym = NULL; (void *) symtab < (void *) strtab; ++symtab)
  68     if (addr >= match->l_addr + symtab->st_value
  69         && (!matchsym
  70             || (matchsym->st_value < symtab->st_value
  71                 && (ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
  72                     || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK))))
  73       matchsym = symtab;
  74
  75   if (matchsym)
  76     {
  77       /* We found a symbol close by.  Fill in its name and exact address.  */
  78       info->dli_sname = strtab + matchsym->st_name;
  79       info->dli_saddr = (void *) (match->l_addr + matchsym->st_value);
  80     }
  81   else
  82     {
  83       /* No symbol matches.  We return only the containing object.  */
  84       info->dli_sname = NULL;
  85       info->dli_saddr = NULL;
  86     }
  87
  88   return 1;
  89 }