dlfcn/dlsym.c

   1 /* Look up a symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1995-2000, 2004 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
  23 #include <ldsodefs.h>
  24
  25 struct dlsym_args
  26 {
  27   /* The arguments to dlsym_doit.  */
  28   void *handle;
  29   const char *name;
  30   void *who;
  31
  32   /* The return value of dlsym_doit.  */
  33   void *sym;
  34 };
  35
  36 static void
  37 dlsym_doit (void *a)
  38 {
  39   struct dlsym_args *args = (struct dlsym_args *) a;
  40
  41   args->sym = _dl_sym (args->handle, args->name, args->who);
  42 }
  43
  44
  45 void *
  46 dlsym (void *handle, const char *name)
  47 {
  48   struct dlsym_args args;
  49   args.who = RETURN_ADDRESS (0);
  50   args.handle = handle;
  51   args.name = name;
  52
  53   /* Protect against concurrent loads and unloads.  */
  54   __rtld_lock_lock_recursive (GL(dl_load_lock));
  55
  56   void *result = (_dlerror_run (dlsym_doit, &args) ? NULL : args.sym);
  57
  58   __rtld_lock_unlock_recursive (GL(dl_load_lock));
  59
  60   return result;
  61 }