1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22/* 23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 .file "vforkx.s" 28 29#include "SYS.h" 30#include <assym.h> 31 32/* 33 * pid = vforkx(flags); 34 * syscall trap: forksys(2, flags) 35 * 36 * pid = vfork(); 37 * syscall trap: forksys(2, 0) 38 * 39 * From the syscall: 40 * %edx == 0 in parent process, %edx = 1 in child process. 41 * %eax == pid of child in parent, %eax == pid of parent in child. 42 * 43 * The child gets a zero return value. 44 * The parent gets the pid of the child. 45 */ 46 47/* 48 * The child of vfork() will execute in the parent's address space, 49 * thereby changing the stack before the parent runs again. 50 * Therefore we have to be careful how we return from vfork(). 51 * Pity the poor debugger developer who has to deal with this kludge. 52 * 53 * We block all blockable signals while performing the vfork() system call 54 * trap. This enables us to set curthread->ul_vfork safely, so that we 55 * don't end up in a signal handler with curthread->ul_vfork set wrong. 56 */ 57 58 ENTRY_NP(vforkx) 59 movq %rdi, %r8 /* flags */ 60 jmp 0f 61 ENTRY_NP(vfork) 62 xorq %r8, %r8 /* flags = 0 */ 630: 64 popq %r9 /* save return %rip in %r9 */ 65 movl $MASKSET1, %edx /* block all signals */ 66 movl $MASKSET0, %esi 67 movl $SIG_SETMASK, %edi 68 __SYSCALL(lwp_sigmask) 69 70 movq %r8, %rsi /* flags */ 71 movl $2, %edi 72 __SYSCALL(forksys) /* vforkx(flags) */ 73 jae 1f 74 75 /* reconstruct stack before jumping to __cerror */ 76 pushq %r9 77 movq %rax, %r8 /* save the vfork() error number */ 78 79 movl %fs:UL_SIGMASK+4, %edx /* reinstate signals */ 80 movl %fs:UL_SIGMASK, %esi 81 movl $SIG_SETMASK, %edi 82 __SYSCALL(lwp_sigmask) 83 84 movq %r8, %rax /* restore the vfork() error number */ 85 jmp __cerror 86 871: 88 /* 89 * To determine if we are (still) a child of vfork(), the child 90 * increments curthread->ul_vfork by one and the parent decrements 91 * it by one. If the result is zero, then we are not a child of 92 * vfork(), else we are. We do this to deal with the case of 93 * a vfork() child calling vfork(). 94 */ 95 cmpl $0, %edx 96 jne 2f 97 movl %fs:UL_VFORK, %edx 98 cmpl $0, %edx /* don't let it go negative */ 99 je 3f 100 subl $1, %edx /* curthread->ul_vfork--; */ 101 jmp 3f 1022: 103 xorl %eax, %eax /* zero the return value in the child */ 104 movl %fs:UL_VFORK, %edx 105 addl $1, %edx /* curthread->ul_vfork++; */ 1063: 107 movl %edx, %fs:UL_VFORK 108 /* 109 * Clear the schedctl interface in both parent and child. 110 * (The child might have modified the parent.) 111 */ 112 xorq %rdx, %rdx 113 movq %rdx, %fs:UL_SCHEDCTL 114 movq %rdx, %fs:UL_SCHEDCTL_CALLED 115 movq %rax, %r8 /* save the vfork() return value */ 116 117 movl %fs:UL_SIGMASK+4, %edx /* reinstate signals */ 118 movl %fs:UL_SIGMASK, %esi 119 movl $SIG_SETMASK, %edi 120 __SYSCALL(lwp_sigmask) 121 122 movq %r8, %rax /* restore the vfork() return value */ 123 jmp *%r9 /* jump back to the caller */ 124 SET_SIZE(vfork) 125 SET_SIZE(vforkx) 126