vfork.s revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
.file "%M%"
#include <sys/asm_linkage.h>
ANSI_PRAGMA_WEAK(vfork,function)
#include "SYS.h"
#include <assym.h>
/ The child of vfork() will execute in the parent's address space,
/ thereby changing the stack before the parent runs again.
/ Therefore we have to be careful how we return from vfork().
/ Pity the poor debugger developer who has to deal with this kludge.
/
/ We block all blockable signals while performing the vfork() system call
/ trap. This enables us to set curthread->ul_vfork safely, so that we
/ don't end up in a signal handler with curthread->ul_vfork set wrong.
ENTRY(vfork)
movl 0(%esp),%ecx / save %eip in %ecx
_prologue_
leal _sref_(0f),%eax / arrange for RET to return here
_epilogue_
movl %eax,0(%esp)
ret
0:
pushl $MASKSET1 / block signals
pushl $MASKSET0
pushl $SIG_SETMASK
pushl %ecx
__SYSCALLINT(lwp_sigmask)
addl $16, %esp
__SYSCALLINT(vfork)
jae 2f
/ reconstruct stack before jumping to __cerror
call 1f
1: movl %ecx,0(%esp)
pushl %eax / save the vfork() error number
pushl %gs:UL_SIGMASK+4 / reinstate signals
pushl %gs:UL_SIGMASK
pushl $SIG_SETMASK
pushl %ecx
__SYSCALLINT(lwp_sigmask)
addl $16, %esp
popl %eax / restore the vfork() error number
jmp __cerror
2:
/ To determine if we are (still) a child of vfork(), the child
/ increments curthread->ul_vfork by one and the parent decrements
/ it by one. If the result is zero, then we are not a child of
/ vfork(), else we are. We do this to deal with the case of
/ a vfork() child calling vfork().
/
/ %edx is zero if we are the parent, non-zero if we are the child.
/
cmpl $0,%edx
jne 3f
movl %gs:UL_VFORK, %edx
cmpl $0, %edx / don't let it go negative
je 4f
subl $1, %edx / curthread->ul_vfork--;
jmp 4f
3:
movl $0,%eax / zero the return value in the child
movl %gs:UL_VFORK, %edx
addl $1, %edx / curthread->ul_vfork++;
4:
movl %edx, %gs:UL_VFORK
/
/ Clear the schedctl interface in both parent and child.
/ (The child might have modified the parent.)
/
xorl %edx, %edx
movl %edx, %gs:UL_SCHEDCTL
movl %edx, %gs:UL_SCHEDCTL_CALLED
pushl %eax / save the vfork() return value
pushl %gs:UL_SIGMASK+4 / reinstate signals
pushl %gs:UL_SIGMASK
pushl $SIG_SETMASK
pushl %ecx
__SYSCALLINT(lwp_sigmask)
addl $16, %esp
popl %eax / restore the vfork() return value
jmp *%ecx / jump back to the caller
SET_SIZE(vfork)