glibc/sysdeps/unix/sysv/linux/arm/vfork.S

/* Copyright (C) 1999-2012 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Philip Blundell <philb@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 <kernel-features.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)

#ifdef __NR_vfork
#ifdef SAVE_PID
	SAVE_PID
#endif
	/* The DO_CALL macro saves r7 on the stack, to enable generation
	   of ARM unwind info.  Since the stack is initially shared between
	   parent and child of vfork, that saved value could be corrupted.
	   To avoid this problem, we save r7 into ip as well, and restore
	   from there.  */
	mov	ip, r7
	cfi_register (r7, ip)
	.fnstart
	str r7, [sp, #-4]!
	cfi_adjust_cfa_offset (4)
	.save { r7 }
	ldr	r7, =SYS_ify (vfork)
	swi	0x0
	.fnend
	add	sp, sp, #4
	cfi_adjust_cfa_offset (-4)
	mov	r7, ip
	cfi_restore (r7);
#ifdef RESTORE_PID
	RESTORE_PID
#endif
	cmn	a1, #4096
	RETINSTR(cc, lr)

# ifdef __ASSUME_VFORK_SYSCALL
	b	PLTJMP(SYSCALL_ERROR)
# else
	/* Check if vfork syscall is known at all.  */
	cmn	a1, #ENOSYS
	bne	PLTJMP(SYSCALL_ERROR)
# endif
#endif

#ifndef __ASSUME_VFORK_SYSCALL
	/* If we don't have vfork, fork is close enough.  */
	DO_CALL (fork, 0)
	cmn	a1, #4096
	RETINSTR(cc, lr)
    	b	PLTJMP(SYSCALL_ERROR)
#elif !defined __NR_vfork
# error "__NR_vfork not available and __ASSUME_VFORK_SYSCALL defined"
#endif

PSEUDO_END (__vfork)
libc_hidden_def (__vfork)

weak_alias (__vfork, vfork)