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/* Copyright (C) 2001-2021 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
<https://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)
/* 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)
cmpl $-4095, %eax
jae SYSCALL_ERROR_LABEL /* Branch forward if it failed. */
#if SHSTK_ENABLED
/* Check if shadow stack is in use. */
xorl %esi, %esi
rdsspq %rsi
testq %rsi, %rsi
/* Normal return if shadow stack isn't in use. */
je L(no_shstk)
testl %eax, %eax
/* In parent, normal return. */
jnz L(no_shstk)
/* NB: In child, jump back to caller via indirect branch without
popping shadow stack which is shared with parent. Keep shadow
stack mismatched so that child returns in the vfork-calling
function will trigger SIGSEGV. */
popq %rdi
cfi_adjust_cfa_offset(-8)
jmp *%rdi
L(no_shstk):
#endif
/* Normal return. */
ret
PSEUDO_END (__vfork)
libc_hidden_def (__vfork)
weak_alias (__vfork, vfork)
strong_alias (__vfork, __libc_vfork)
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