1/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <unistd.h>
20#include <list.h>
21#include <fork.h>
22#include <dl-sysdep.h>
23#include <tls.h>
24#include <string.h>
25#include <pthreadP.h>
26#include <libc-lock.h>
27#include <sysdep.h>
28#include <ldsodefs.h>
29
30
31unsigned long int *__fork_generation_pointer;
32
33
34#ifdef TLS_MULTIPLE_THREADS_IN_TCB
35void
36#else
37extern int __libc_multiple_threads attribute_hidden;
38
39int *
40#endif
41__libc_pthread_init (unsigned long int *ptr, void (*reclaim) (void),
42 const struct pthread_functions *functions)
43{
44 /* Remember the pointer to the generation counter in libpthread. */
45 __fork_generation_pointer = ptr;
46
47 /* Called by a child after fork. */
48 __register_atfork (NULL, NULL, reclaim, NULL);
49
50#ifdef SHARED
51 /* Copy the function pointers into an array in libc. This enables
52 access with just one memory reference but moreso, it prevents
53 hijacking the function pointers with just one pointer change. We
54 "encrypt" the function pointers since we cannot write-protect the
55 array easily enough. */
56 union ptrhack
57 {
58 struct pthread_functions pf;
59# define NPTRS (sizeof (struct pthread_functions) / sizeof (void *))
60 void *parr[NPTRS];
61 } __attribute__ ((may_alias)) const *src;
62 union ptrhack *dest;
63
64 src = (const void *) functions;
65 dest = (void *) &__libc_pthread_functions;
66
67 for (size_t cnt = 0; cnt < NPTRS; ++cnt)
68 {
69 void *p = src->parr[cnt];
70 PTR_MANGLE (p);
71 dest->parr[cnt] = p;
72 }
73 __libc_pthread_functions_init = 1;
74#endif
75
76#ifndef TLS_MULTIPLE_THREADS_IN_TCB
77 return &__libc_multiple_threads;
78#endif
79}
80