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