1/* $OpenBSD: Ovfork.S,v 1.10 2023/05/18 04:26:06 guenther Exp $ */ 2/* $NetBSD: Ovfork.S,v 1.2 2002/06/03 18:30:33 fvdl Exp $ */ 3 4/*- 5 * Copyright (c) 1990 The Regents of the University of California. 6 * All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * William Jolitz. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * from: @(#)Ovfork.s 5.1 (Berkeley) 4/23/90 36 */ 37 38#include <machine/asm.h> 39 40#include "SYS.h" 41 42/* 43 * This is written to support a potential vfork(2) that would share 44 * the parent's vmspace to the child. For that, the parent must 45 * not rely on anything on the stack at the time of the syscall, 46 * as the child will overwrite it. So, keep both the return address 47 * and retguard value in registers (r9 and r8) across the call. 48 * This used to do an indirect jump on success, but that doesn't 49 * work if indirect-branch-tracking is enabled as the _caller_ of 50 * this vfork() stub won't know to place an endbr64 instruction 51 * after the call. So, just push it back on the stack and return. 52 */ 53SYSENTRY_HIDDEN(vfork) 54 RETGUARD_SETUP(_thread_sys_vfork, r8); 55 popq %r9 /* my rta into r9 */ 56 SYSTRAP(vfork) 57 pushq %r9 58 jnc 1f 59 SET_ERRNO 601: RETGUARD_CHECK(_thread_sys_vfork, r8); 61 ret 62SYSCALL_END_HIDDEN(vfork) 63