1/* $NetBSD: __vfork14.S,v 1.10 2020/05/09 08:25:33 skrll Exp $ */ 2 3/*- 4 * Copyright (c) 2001 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Matt Fredette. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32#include <sys/errno.h> 33#include "SYS.h" 34 35ENTRY(__vfork14, 0) 36 /* 37 * NB: __vfork14 is a tricky syscall. We can't save 38 * any values on the stack, because the stack will be 39 * trashed by the child, leaving garbage for when the 40 * parent returns. 41 * 42 * So we must save values in registers, specifically, 43 * registers that the kernel is willing to preserve 44 * across the syscall. Normally, this would be callee- 45 * saved registers, with the kernel being the callee, 46 * but the problem is that we, too, are a callee, and 47 * would have to save that very same register somewhere, 48 * because *our* caller is counting on us to do so. 49 * 50 * What we need is a normally caller-saved register, 51 * that the kernel is willing to save for us. The 52 * syscall entry code in locore.S has been modified 53 * to do just this for the t4 register. 54 */ 55 copy %rp, %t4 56 ldil L%SYSCALLGATE, %r1 57 ble 4(%sr2, %r1) 58 ldi SYS___vfork14, %t1 59 comb,=,n %r0, %t1, 1f 60 b __cerror 611: 62 copy %t4, %rp // delay slot of branch to __cerror 63 addi -1, %ret1, %ret1 64 bv %r0(%rp) 65 and %ret0, %ret1, %ret0 66EXIT(__vfork14) 67