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/* Copyright (C) 1999-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Andreas Schwab <schwab@gnu.org>.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
#define _ERRNO_H 1
#include <bits/errno.h>
#include <tcb-offsets.h>
/* Clone the calling process, but without copying the whole address space.
The calling process is suspended until the new process exits or is
replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
and the process ID of the new process to the old process. */
ENTRY (__vfork)
/* Pop the return PC value into ECX. */
popl %ecx
cfi_adjust_cfa_offset (-4)
cfi_register (%eip, %ecx)
/* Save the TCB-cached PID away in %edx, and then negate the TCB
field. But if it's zero, set it to 0x80000000 instead. See
raise.c for the logic that relies on this value. */
movl %gs:PID, %edx
movl %edx, %eax
negl %eax
jne 1f
movl $0x80000000, %eax
1: movl %eax, %gs:PID
/* Stuff the syscall number in EAX and enter into the kernel. */
movl $SYS_ify (vfork), %eax
int $0x80
/* Jump to the return PC. Don't jump directly since this
disturbs the branch target cache. Instead push the return
address back on the stack. */
pushl %ecx
cfi_adjust_cfa_offset (4)
/* Restore the original value of the TCB cache of the PID, if we're
the parent. But in the child (syscall return value equals zero),
leave things as they are. */
testl %eax, %eax
je 1f
movl %edx, %gs:PID
1:
cmpl $-4095, %eax
/* Branch forward if it failed. */
jae SYSCALL_ERROR_LABEL
ret
PSEUDO_END (__vfork)
libc_hidden_def (__vfork)
weak_alias (__vfork, vfork)
strong_alias (__vfork, __libc_vfork)
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