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
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, 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) loadbase;
  30   const ElfW(Sym) *ref = NULL;
  31   void doit (void)
  32     {
  33       struct link_map *map = handle, **scope, *mapscope[2] = { map, NULL };
  34       const char *owner;
  35
  36       if (map)
  37         {
  38           /* Search the scope of the given object.  */
  39           scope = mapscope;
  40           owner = map->l_name;
  41         }
  42       else
  43         {
  44           scope = &(_dl_global_scope ?: _dl_default_scope)[2];
  45           owner = NULL;
  46         }
  47       loadbase = _dl_lookup_symbol (name, &ref, scope, owner, 0);
  48     }
  49
  50   return _dlerror_run (doit) ? NULL : (void *) (loadbase + ref->st_value);
  51 }