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