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

   1 /* ELF symbol resolve functions for VDSO objects.
   2    Copyright (C) 2005-2018 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "config.h"
  20 #include <ldsodefs.h>
  21
  22
  23 void *
  24 _dl_vdso_vsym (const char *name, const struct r_found_version *vers)
  25 {
  26   struct link_map *map = GLRO (dl_sysinfo_map);
  27   void *value = NULL;
  28
  29
  30   if (map != NULL)
  31     {
  32       /* Use a WEAK REF so we don't error out if the symbol is not found.  */
  33       ElfW (Sym) wsym;
  34       memset (&wsym, 0, sizeof (ElfW (Sym)));
  35       wsym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));
  36
  37       /* Search the scope of the vdso map.  */
  38       const ElfW (Sym) *ref = &wsym;
  39       lookup_t result = GLRO (dl_lookup_symbol_x) (name, map, &ref,
  40                                                    map->l_local_scope,
  41                                                    vers, 0, 0, NULL);
  42
  43       if (ref != NULL)
  44         value = DL_SYMBOL_ADDRESS (result, ref);
  45     }
  46
  47   return value;
  48 }