/*      $NetBSD: __vfork14.S,v 1.10 2020/05/09 08:25:33 skrll Exp $     */

/*-
 * Copyright (c) 2001 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Matt Fredette.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/errno.h>
#include "SYS.h"

ENTRY(__vfork14, 0)
        /*
         * NB: __vfork14 is a tricky syscall.  We can't save
         * any values on the stack, because the stack will be
         * trashed by the child, leaving garbage for when the
         * parent returns.
         *
         * So we must save values in registers, specifically,
         * registers that the kernel is willing to preserve
         * across the syscall.  Normally, this would be callee-
         * saved registers, with the kernel being the callee,
         * but the problem is that we, too, are a callee, and
         * would have to save that very same register somewhere,
         * because *our* caller is counting on us to do so.
         *
         * What we need is a normally caller-saved register,
         * that the kernel is willing to save for us.  The
         * syscall entry code in locore.S has been modified
         * to do just this for the t4 register.
         */
        copy    %rp, %t4
        ldil    L%SYSCALLGATE, %r1
        ble     4(%sr2, %r1)
         ldi    SYS___vfork14, %t1
        comb,=,n %r0, %t1, 1f
        b       __cerror
1:
         copy   %t4, %rp                // delay slot of branch to __cerror
        addi    -1, %ret1, %ret1
        bv      %r0(%rp)
         and    %ret0, %ret1, %ret0
EXIT(__vfork14)