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__vfork14.S revision 1.1 
      1 /*	$NetBSD: __vfork14.S,v 1.1 2002/06/06 20:31:23 fredette 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  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/errno.h>
     40 #include "SYS.h"
     41 
     42 	.import errno, data
     43 
     44 ENTRY(__vfork14, 0)
     45 	/*
     46 	 * NB: __vfork14 is a tricky syscall.  We can't save
     47 	 * any values on the stack, because the stack will be
     48 	 * trashed by the child, leaving garbage for when the
     49 	 * parent returns.
     50 	 *
     51 	 * So we must save values in registers, specifically,
     52 	 * registers that the kernel is willing to preserve
     53 	 * across the syscall.  Normally, this would be callee-
     54 	 * saved registers, with the kernel being the callee,
     55 	 * but the problem is that we, too, are a callee, and
     56 	 * would have to save that very same register somewhere,
     57 	 * because *our* caller is counting on us to do so.
     58 	 *
     59 	 * What we need is a normally caller-saved register,
     60 	 * that the kernel is willing to save for us.  The
     61 	 * syscall entry code in locore.S has been modified
     62 	 * to do just this for the t4 register.
     63 	 */
     64 	.import	errno, data
     65 	copy	rp, t4
     66 	ldil	L%SYSCALLGATE, r1
     67 	ble	4(sr7, r1)
     68 	ldi	SYS___vfork14, t1
     69 	copy	t4, rp
     70 	comb,=,n r0, t1, __vfork14$noerr
     71 	ldil	L%errno, r1
     72 	stw	t1, R%errno(r1)
     73 	ldi	-1, ret0
     74 	bv	r0(rp)
     75 	ldi	-1, ret1
     76 __vfork14$noerr
     77 	addi	-1, ret1, ret1
     78 	bv	r0(rp)
     79 	and	ret0, ret1, ret0
     80 EXIT(__vfork14)
     81