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
* 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 (c) 1988 AT&T */
/* All Rights Reserved */
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.ident "%Z%%M% %I% %E% SMI"
/*
* C library -- vfork
* pid_t vfork(void);
*/
/*
* From the syscall:
* %o1 == 0 in parent process, %o1 == 1 in child process.
* %o0 == pid of child in parent, %o0 == pid of parent in child.
*
* The child process gets a zero return value from vfork; the parent
* gets the pid of the child.
*
* 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.
*
* Note that since the SPARC architecture maintains stack maintence
* information (return pc, sp, fp) in the register windows, both parent
* and child can execute in a common address space without conflict.
*/
.file "%M%"
#include <sys/asm_linkage.h>
#include "SYS.h"
#include <../assym.h>
1:
/*
* 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().
*/
sub %g1, 1, %g1 ! curthread->ul_vfork--;
ba,a 3f
2:
clr %o0 ! child, return (0)
add %g1, 1, %g1 ! curthread->ul_vfork++;
3:
st %g1, [%g7 + UL_VFORK]
/*
* Clear the schedctl interface in both parent and child.
* (The child might have modified the parent.)
*/
stn %g0, [%g7 + UL_SCHEDCTL]
stn %g0, [%g7 + UL_SCHEDCTL_CALLED]
mov %o0, %o3 ! save the vfork() return value
mov SIG_SETMASK, %o0 ! reinstate signals
ld [%g7 + UL_SIGMASK], %o1
ld [%g7 + UL_SIGMASK + 4], %o2
SYSTRAP_2RVALS(lwp_sigmask)
retl
mov %o3, %o0 ! restore the vfork() return value
SET_SIZE(vfork)