elf/dlvsym.c

   1 /* Look up a versioned symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1995, 1996, 1997, 1998, 1999 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <dlfcn.h>
  21 #include <setjmp.h>
  22 #include <stddef.h>
  23 #include <elf/ldsodefs.h>
  24
  25 #include <dl-hash.h>
  26
  27 struct dlvsym_args
  28 {
  29   /* The arguments to dlvsym_doit.  */
  30   void *handle;
  31   const char *name;
  32   struct r_found_version version;
  33   ElfW(Addr) caller;
  34   /* The return values of dlvsym_doit.  */
  35   ElfW(Addr) loadbase;
  36   const ElfW(Sym) *ref;
  37 };
  38
  39
  40 static void
  41 dlvsym_doit (void *a)
  42 {
  43   struct dlvsym_args *args = (struct dlvsym_args *)a;
  44   args->ref = NULL;
  45
  46   if (args->handle == RTLD_DEFAULT)
  47     /* Search the global scope.  */
  48     args->loadbase = _dl_lookup_versioned_symbol (args->name, &args->ref,
  49                                                   _dl_global_scope,
  50                                                   NULL, &args->version, 0);
  51   else if (args->handle == RTLD_NEXT)
  52     {
  53       struct link_map *l, *match;
  54
  55       /* Find the highest-addressed object that CALLER is not below.  */
  56       match = NULL;
  57       for (l = _dl_loaded; l; l = l->l_next)
  58         if (args->caller >= l->l_addr && (!match || match->l_addr < l->l_addr))
  59           match = l;
  60
  61       if (! match)
  62         _dl_signal_error (0, NULL, _("\
  63 RTLD_NEXT used in code not dynamically loaded"));
  64
  65       l = match;
  66       while (l->l_loader)
  67         l = l->l_loader;
  68
  69       args->loadbase = _dl_lookup_versioned_symbol_skip (args->name,
  70                                                          &args->ref,
  71                                                          l->l_local_scope,
  72                                                          NULL, &args->version,
  73                                                          match);
  74
  75       if (args->loadbase == 0)
  76         {
  77           /* This means that no such symbol is defined.  In this case we
  78              have to provide a phony Elfxx_Sym entry since the value is
  79              referenced in `dlsym'.  */
  80           static const ElfW(Sym) null_result;
  81
  82           args->ref = &null_result;
  83         }
  84     }
  85   else
  86     {
  87       /* Search the scope of the given object.  */
  88       struct link_map *map = args->handle;
  89       args->loadbase = _dl_lookup_versioned_symbol (args->name, &args->ref,
  90                                                     map->l_local_scope,
  91                                                     map->l_name,
  92                                                     &args->version, 0);
  93     }
  94 }
  95
  96 void *
  97 __dlvsym (void *handle, const char *name, const char *version_str)
  98 {
  99   struct dlvsym_args args;
 100
 101   args.handle = handle;
 102   args.name = name;
 103   args.caller = (ElfW(Addr)) __builtin_return_address (0);
 104
 105   /* Compute hash value to the version string.  */
 106   args.version.name = version_str;
 107   args.version.hidden = 1;
 108   args.version.hash = _dl_elf_hash (version_str);
 109   /* We don't have a specific file where the symbol can be found.  */
 110   args.version.filename = NULL;
 111
 112   return (_dlerror_run (dlvsym_doit, &args)
 113           ? NULL : (void *) (args.loadbase + args.ref->st_value));
 114 }
 115 weak_alias (__dlvsym, dlvsym)