sysdeps/unix/sysv/linux/dl-vdso.c

   1 /* ELF symbol resolve functions for VDSO objects.
   2    Copyright (C) 2005, 2007 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 "config.h"
  21 #include <ldsodefs.h>
  22
  23
  24 void *
  25 internal_function
  26 _dl_vdso_vsym (const char *name, const struct r_found_version *vers)
  27 {
  28   struct link_map *map = GLRO (dl_sysinfo_map);
  29   void *value = NULL;
  30
  31
  32   if (map != NULL)
  33     {
  34       /* Use a WEAK REF so we don't error out if the symbol is not found.  */
  35       ElfW (Sym) wsym;
  36       memset (&wsym, 0, sizeof (ElfW (Sym)));
  37       wsym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));
  38
  39       /* Search the scope of the vdso map.  */
  40       const ElfW (Sym) *ref = &wsym;
  41       lookup_t result = GLRO (dl_lookup_symbol_x) (name, map, &ref,
  42                                                    map->l_local_scope,
  43                                                    vers, 0, 0, NULL);
  44
  45       if (ref != NULL)
  46         value = DL_SYMBOL_ADDRESS (result, ref);
  47     }
  48
  49   return value;
  50 }