dlfcn/dlvsym.c

   1 /* Look up a versioned symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1995-2023 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 <ldsodefs.h>
  21 #include <shlib-compat.h>
  22 #include <stddef.h>
  23
  24 struct dlvsym_args
  25 {
  26   /* The arguments to dlvsym_doit.  */
  27   void *handle;
  28   const char *name;
  29   const char *version;
  30   void *who;
  31
  32   /* The return values of dlvsym_doit.  */
  33   void *sym;
  34 };
  35
  36 static void
  37 dlvsym_doit (void *a)
  38 {
  39   struct dlvsym_args *args = (struct dlvsym_args *) a;
  40
  41   args->sym = _dl_vsym (args->handle, args->name, args->version, args->who);
  42 }
  43
  44 static void *
  45 dlvsym_implementation (void *handle, const char *name, const char *version,
  46                        void *dl_caller)
  47 {
  48   struct dlvsym_args args;
  49   args.who = dl_caller;
  50   args.handle = handle;
  51   args.name = name;
  52   args.version = version;
  53
  54   /* Protect against concurrent loads and unloads.  */
  55   __rtld_lock_lock_recursive (GL(dl_load_lock));
  56
  57   void *result = (_dlerror_run (dlvsym_doit, &args) ? NULL : args.sym);
  58
  59   __rtld_lock_unlock_recursive (GL(dl_load_lock));
  60
  61   return result;
  62 }
  63
  64 #ifdef SHARED
  65 void *
  66 ___dlvsym (void *handle, const char *name, const char *version)
  67 {
  68   if (GLRO (dl_dlfcn_hook) != NULL)
  69     return GLRO (dl_dlfcn_hook)->dlvsym (handle, name, version,
  70                                          RETURN_ADDRESS (0));
  71   else
  72     return dlvsym_implementation (handle, name, version, RETURN_ADDRESS (0));
  73 }
  74 versioned_symbol (libc, ___dlvsym, dlvsym, GLIBC_2_34);
  75
  76 # if OTHER_SHLIB_COMPAT (libdl, GLIBC_2_1, GLIBC_2_34)
  77 compat_symbol (libdl, ___dlvsym, dlvsym, GLIBC_2_1);
  78 # endif
  79
  80 #else /* !SHARED */
  81 /* Also used with _dlfcn_hook.  */
  82 void *
  83 __dlvsym (void *handle, const char *name, const char *version, void *dl_caller)
  84 {
  85   return dlvsym_implementation (handle, name, version, dl_caller);
  86 }
  87
  88 void *
  89 ___dlvsym (void *handle, const char *name, const char *version)
  90 {
  91   return __dlvsym (handle, name, version, RETURN_ADDRESS (0));
  92 }
  93 weak_alias (___dlvsym, dlvsym)
  94 #endif /* !SHARED */