dlfcn/dlvsym.c

   1 /* Look up a versioned symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1995-2020 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <dlfcn.h>
  20 #include <stddef.h>
  21
  22 #include <ldsodefs.h>
  23
  24 #if !defined SHARED && IS_IN (libdl)
  25
  26 void *
  27 weak_function
  28 dlvsym (void *handle, const char *name, const char *version_str)
  29 {
  30   return __dlvsym (handle, name, version_str, RETURN_ADDRESS (0));
  31 }
  32
  33 #else
  34
  35 struct dlvsym_args
  36 {
  37   /* The arguments to dlvsym_doit.  */
  38   void *handle;
  39   const char *name;
  40   const char *version;
  41   void *who;
  42
  43   /* The return values of dlvsym_doit.  */
  44   void *sym;
  45 };
  46
  47
  48 static void
  49 dlvsym_doit (void *a)
  50 {
  51   struct dlvsym_args *args = (struct dlvsym_args *)a;
  52
  53   args->sym = _dl_vsym (args->handle, args->name, args->version, args->who);
  54 }
  55
  56 void *
  57 __dlvsym (void *handle, const char *name, const char *version_str
  58           DL_CALLER_DECL)
  59 {
  60 # ifdef SHARED
  61   if (!rtld_active ())
  62     return _dlfcn_hook->dlvsym (handle, name, version_str, DL_CALLER);
  63 # endif
  64
  65   struct dlvsym_args args;
  66   args.handle = handle;
  67   args.name = name;
  68   args.who = DL_CALLER;
  69   args.version = version_str;
  70
  71   /* Protect against concurrent loads and unloads.  */
  72   __rtld_lock_lock_recursive (GL(dl_load_lock));
  73
  74   void *result = (_dlerror_run (dlvsym_doit, &args) ? NULL : args.sym);
  75
  76   __rtld_lock_unlock_recursive (GL(dl_load_lock));
  77
  78   return result;
  79 }
  80 # ifdef SHARED
  81 weak_alias (__dlvsym, dlvsym)
  82 # endif
  83 #endif