1/* Look up a 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
24struct dlsym_args
25{
26 /* The arguments to dlsym_doit. */
27 void *handle;
28 const char *name;
29 void *who;
30
31 /* The return value of dlsym_doit. */
32 void *sym;
33};
34
35static void
36dlsym_doit (void *a)
37{
38 struct dlsym_args *args = (struct dlsym_args *) a;
39
40 args->sym = _dl_sym (args->handle, args->name, args->who);
41}
42
43static void *
44dlsym_implementation (void *handle, const char *name, void *dl_caller)
45{
46 struct dlsym_args args;
47 args.who = dl_caller;
48 args.handle = handle;
49 args.name = name;
50
51 /* Protect against concurrent loads and unloads. */
52 __rtld_lock_lock_recursive (GL(dl_load_lock));
53
54 void *result = (_dlerror_run (dlsym_doit, &args) ? NULL : args.sym);
55
56 __rtld_lock_unlock_recursive (GL(dl_load_lock));
57
58 return result;
59}
60
61#ifdef SHARED
62void *
63___dlsym (void *handle, const char *name)
64{
65 if (GLRO (dl_dlfcn_hook) != NULL)
66 return GLRO (dl_dlfcn_hook)->dlsym (handle, name, RETURN_ADDRESS (0));
67 else
68 return dlsym_implementation (handle, name, RETURN_ADDRESS (0));
69}
70versioned_symbol (libc, ___dlsym, dlsym, GLIBC_2_34);
71
72# if OTHER_SHLIB_COMPAT (libdl, GLIBC_2_0, GLIBC_2_34)
73compat_symbol (libdl, ___dlsym, dlsym, GLIBC_2_0);
74# endif
75
76#else /* !SHARED */
77/* Also used with _dlfcn_hook. */
78void *
79__dlsym (void *handle, const char *name, void *dl_caller)
80{
81 return dlsym_implementation (handle, name, dl_caller);
82}
83
84void *
85___dlsym (void *handle, const char *name)
86{
87 return __dlsym (handle, name, RETURN_ADDRESS (0));
88}
89weak_alias (___dlsym, dlsym)
90#endif /* !SHARED */
91