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glibc  2.9
dl-vdso.c
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00001 /* ELF symbol resolve functions for VDSO objects.
00002    Copyright (C) 2005, 2007 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include "config.h"
00021 #include <ldsodefs.h>
00022 
00023 
00024 void *
00025 internal_function
00026 _dl_vdso_vsym (const char *name, const struct r_found_version *vers)
00027 {
00028   struct link_map *map = GLRO (dl_sysinfo_map);
00029   void *value = NULL;
00030 
00031 
00032   if (map != NULL)
00033     {
00034       /* Use a WEAK REF so we don't error out if the symbol is not found.  */
00035       ElfW (Sym) wsym;
00036       memset (&wsym, 0, sizeof (ElfW (Sym)));
00037       wsym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));
00038 
00039       /* Search the scope of the vdso map.  */
00040       const ElfW (Sym) *ref = &wsym;
00041       lookup_t result = GLRO (dl_lookup_symbol_x) (name, map, &ref,
00042                                              map->l_local_scope,
00043                                              vers, 0, 0, NULL);
00044 
00045       if (ref != NULL)
00046        value = DL_SYMBOL_ADDRESS (result, ref);
00047     }
00048 
00049   return value;
00050 }