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 #if !defined SHARED && defined IS_IN_libdl
  26
  27 void *
  28 dlsym (void *handle, const char *name)
  29 {
  30   return __dlsym (handle, name, RETURN_ADDRESS (0));
  31 }
  32
  33 #else
  34
  35 struct dlsym_args
  36 {
  37   /* The arguments to dlsym_doit.  */
  38   void *handle;
  39   const char *name;
  40   void *who;
  41
  42   /* The return value of dlsym_doit.  */
  43   void *sym;
  44 };
  45
  46 static void
  47 dlsym_doit (void *a)
  48 {
  49   struct dlsym_args *args = (struct dlsym_args *) a;
  50
  51   args->sym = _dl_sym (args->handle, args->name, args->who);
  52 }
  53
  54
  55 void *
  56 __dlsym (void *handle, const char *name DL_CALLER_DECL)
  57 {
  58 # ifdef SHARED
  59   if (__builtin_expect (_dlfcn_hook != NULL, 0))
  60     return _dlfcn_hook->dlsym (handle, name, DL_CALLER);
  61 # endif
  62
  63   struct dlsym_args args;
  64   args.who = DL_CALLER;
  65   args.handle = handle;
  66   args.name = name;
  67
  68   /* Protect against concurrent loads and unloads.  */
  69   __rtld_lock_lock_recursive (GL(dl_load_lock));
  70
  71   void *result = (_dlerror_run (dlsym_doit, &args) ? NULL : args.sym);
  72
  73   __rtld_lock_unlock_recursive (GL(dl_load_lock));
  74
  75   return result;
  76 }
  77 # ifdef SHARED
  78 strong_alias (__dlsym, dlsym)
  79 # endif
  80 #endif