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/* Copyright (C) 2001-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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 RDI. We need a register that
is preserved by the syscall and that we're allowed to destroy. */
popq %rdi
cfi_adjust_cfa_offset(-8)
cfi_register(%rip, %rdi)
/* Save the TCB-cached PID away in %esi, 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 %fs:PID, %esi
movl $0x80000000, %ecx
movl %esi, %edx
negl %edx
cmove %ecx, %edx
movl %edx, %fs:PID
/* Stuff the syscall number in RAX and enter into the kernel. */
movl $SYS_ify (vfork), %eax
syscall
/* Push back the return PC. */
pushq %rdi
cfi_adjust_cfa_offset(8)
/* 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. */
testq %rax, %rax
je 1f
movl %esi, %fs:PID
1:
cmpl $-4095, %eax
jae SYSCALL_ERROR_LABEL /* Branch forward if it failed. */
/* Normal return. */
ret
PSEUDO_END (__vfork)
libc_hidden_def (__vfork)
weak_alias (__vfork, vfork)
strong_alias (__vfork, __libc_vfork)
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