1 /* Copyright (C) 2005-2017 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library. If not, see
16 <http://www.gnu.org/licenses/>. */
20 #include <bits/errno.h>
21 #include <tcb-offsets.h>
23 /* Clone the calling process, but without copying the whole address space.
24 The calling process is suspended until the new process exits or is
25 replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
26 and the process ID of the new process to the old process. */
28 .Lthread_start: ASM_LINE_SEP
30 /* r26, r25, r24, r23 are free since vfork has no arguments */
32 /* We must not create a frame. When the child unwinds to call
33 exec it will clobber the same frame that the parent
36 /* Save the PIC register. */
38 copy %r19, %r25 /* parent */
41 /* Syscall saves and restores all register states */
47 comclr,>>= %r1,%ret0,%r0 /* Note: unsigned compare. */
50 /* Return, and DO NOT restore rp. The child may have called
51 functions that updated the frame's rp. This works because
52 the kernel ensures rp is preserved across the vfork
57 /* Now we need a stack to call a function. We are assured
58 that there is no child now, so it's safe to create
66 /* Restore the PIC register (in delay slot) on error */
68 copy %r25, %r19 /* parent */
72 /* Write syscall return into errno location */
78 libc_hidden_def (__vfork)
79 weak_alias (__vfork, vfork)