1/* arch_fork definition for Linux fork implementation.
2 Copyright (C) 2014-2021 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#ifndef __ARCH_FORK_H
20#define __ARCH_FORK_H
21
22#include <unistd.h>
23
24/* Call the clone syscall with fork semantic. The CTID address is used
25 to store the child thread ID at its locationm, to erase it in child memory
26 when the child exits, and do a wakeup on the futex at that address.
27
28 The architecture with non-default kernel abi semantic should correctlly
29 override it with one of the supported calling convention (check generic
30 kernel-features.h for the clone abi variants). */
31static inline pid_t
32arch_fork (void *ctid)
33{
34 const int flags = CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD;
35 long int ret;
36#ifdef __ASSUME_CLONE_BACKWARDS
37# ifdef INLINE_CLONE_SYSCALL
38 ret = INLINE_CLONE_SYSCALL (flags, 0, NULL, 0, ctid);
39# else
40 ret = INLINE_SYSCALL_CALL (clone, flags, 0, NULL, 0, ctid);
41# endif
42#elif defined(__ASSUME_CLONE_BACKWARDS2)
43 ret = INLINE_SYSCALL_CALL (clone, 0, flags, NULL, ctid, 0);
44#elif defined(__ASSUME_CLONE_BACKWARDS3)
45 ret = INLINE_SYSCALL_CALL (clone, flags, 0, 0, NULL, ctid, 0);
46#elif defined(__ASSUME_CLONE2)
47 ret = INLINE_SYSCALL_CALL (clone2, flags, 0, 0, NULL, ctid, 0);
48#elif defined(__ASSUME_CLONE_DEFAULT)
49 ret = INLINE_SYSCALL_CALL (clone, flags, 0, NULL, ctid, 0);
50#else
51# error "Undefined clone variant"
52#endif
53 return ret;
54}
55
56#endif /* __ARCH_FORK_H */
57