/* Copyright (C) 1999-2018 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>

#if SHSTK_ENABLED

/* The shadow stack prevents us from pushing the saved return PC onto

   the stack and returning normally.  Instead we pop the shadow stack

   and return directly.  This is the safest way to return and ensures

   any stack manipulations done by the vfork'd child doesn't cause the

   parent to terminate when CET is enabled.  */

# undef SYSCALL_ERROR_HANDLER

# ifdef PIC

#  define SYSCALL_ERROR_HANDLER				\

0:							\

  calll .L1;						\

.L1:							\

  popl %edx;						\

.L2:							\

  addl $_GLOBAL_OFFSET_TABLE_ + (.L2 - .L1), %edx;	\

  movl __libc_errno@gotntpoff(%edx), %edx;		\

  negl %eax;						\

  movl %eax, %gs:(%edx);				\

  orl $-1, %eax;					\

  jmp 1b;

# else

#  define SYSCALL_ERROR_HANDLER				\

0:							\

  movl __libc_errno@indntpoff, %edx;			\

  negl %eax;						\

  movl %eax, %gs:(%edx);				\

  orl $-1, %eax;					\

  jmp 1b;

# endif

# undef SYSCALL_ERROR_LABEL

# define SYSCALL_ERROR_LABEL 0f

#endif

/* 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)

	/* Stuff the syscall number in EAX and enter into the kernel.  */

	movl	$SYS_ify (vfork), %eax

	int	$0x80

#if !SHSTK_ENABLED

	/* 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)

#endif

	cmpl	$-4095, %eax

	/* Branch forward if it failed.  */

	jae	SYSCALL_ERROR_LABEL

#if SHSTK_ENABLED

1:

	/* Check if shadow stack is in use.  */

	xorl	%edx, %edx

	rdsspd	%edx

	testl	%edx, %edx

	/* Normal return if shadow stack isn't in use.  */

	je	L(no_shstk)

	/* Pop return address from shadow stack and jump back to caller

	   directly.  */

	movl	$1, %edx

	incsspd	%edx

	jmp	*%ecx

L(no_shstk):

	/* 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)

#endif

	ret

PSEUDO_END (__vfork)

libc_hidden_def (__vfork)

weak_alias (__vfork, vfork)

strong_alias (__vfork, __libc_vfork)