657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * CDDL HEADER START
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * The contents of this file are subject to the terms of the
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * Common Development and Distribution License (the "License").
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * You may not use this file except in compliance with the License.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * See the License for the specific language governing permissions
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * and limitations under the License.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * When distributing Covered Code, include this CDDL HEADER in each
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * CDDL HEADER END
bdf0047c9427cca40961a023475891c898579c37Roger A. Faulkner * Copyright 2010 Sun Microsystems, Inc. All rights reserved.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * Use is subject to license terms.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * pid = vforkx(flags);
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * syscall trap: forksys(2, flags)
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * pid = vfork();
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * syscall trap: forksys(2, 0)
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * From the syscall:
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * %edx == 0 in parent process, %edx = 1 in child process.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * %eax == pid of child in parent, %eax == pid of parent in child.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * The child gets a zero return value.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * The parent gets the pid of the child.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * The child of vfork() will execute in the parent's address space,
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * thereby changing the stack before the parent runs again.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * Therefore we have to be careful how we return from vfork().
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * Pity the poor debugger developer who has to deal with this kludge.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * We block all blockable signals while performing the vfork() system call
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * trap. This enables us to set curthread->ul_vfork safely, so that we
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * don't end up in a signal handler with curthread->ul_vfork set wrong.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf /* reconstruct stack before jumping to __cerror */
bdf0047c9427cca40961a023475891c898579c37Roger A. Faulkner pushl %gs:UL_SIGMASK+12 /* reinstate signals */
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * To determine if we are (still) a child of vfork(), the child
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * increments curthread->ul_vfork by one and the parent decrements
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * it by one. If the result is zero, then we are not a child of
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * vfork(), else we are. We do this to deal with the case of
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * a vfork() child calling vfork().
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf xorl %eax, %eax /* zero the return value in the child */
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * Clear the schedctl interface in both parent and child.
657b1f3d64bcf8eaa2385dba72a6047f089433b2raf * (The child might have modified the parent.)
bdf0047c9427cca40961a023475891c898579c37Roger A. Faulkner pushl %gs:UL_SIGMASK+12 /* reinstate signals */