elf/dlsym.c

   1 /* dlsym -- Look up a symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1995, 1996 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 #include <setjmp.h>
  24
  25
  26 void *
  27 dlsym (void *handle, const char *name)
  28 {
  29   ElfW(Addr) caller = (ElfW(Addr)) __builtin_return_address (0);
  30   ElfW(Addr) loadbase;
  31   const ElfW(Sym) *ref = NULL;
  32   void doit (void)
  33     {
  34       if (handle == NULL)
  35         /* Search the global scope.  */
  36         loadbase = _dl_lookup_symbol
  37           (name, &ref, &(_dl_global_scope ?: _dl_default_scope)[2], NULL, 0);
  38       else if (handle == RTLD_NEXT)
  39         {
  40           struct link_map *l, *match;
  41
  42           /* Find the highest-addressed object that CALLER is not below.  */
  43           match = NULL;
  44           for (l = _dl_loaded; l; l = l->l_next)
  45             if (caller >= l->l_addr && (!match || match->l_addr < l->l_addr))
  46               match = l;
  47
  48           if (! match)
  49             _dl_signal_error (0, NULL, _("\
  50 RTLD_NEXT used in code not dynamically loaded"));
  51
  52           l = match;
  53           while (l->l_loader)
  54             l = l->l_loader;
  55
  56           loadbase = _dl_lookup_symbol_skip
  57             (name, &ref, &_dl_loaded, NULL, l, 0);
  58         }
  59       else
  60         {
  61           /* Search the scope of the given object.  */
  62           struct link_map *map = handle;
  63           struct link_map *mapscope[2] = { map, NULL };
  64           loadbase = _dl_lookup_symbol (name, &ref, mapscope, map->l_name, 0);
  65         }
  66     }
  67
  68   return _dlerror_run (doit) ? NULL : (void *) (loadbase + ref->st_value);
  69 }