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compat_Ovfork.S revision 1.1.40.1 
      1 /*
      2  * Copyright (c) 1983, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. Neither the name of the University nor the names of its contributors
     14  *    may be used to endorse or promote products derived from this software
     15  *    without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     27  * SUCH DAMAGE.
     28  */
     29 
     30 #include "SYS.h"
     31 
     32 #if defined(SYSLIBC_SCCS) && !defined(lint)
     33 	/* .asciz "@(#)Ovfork.s	8.1 (Berkeley) 6/4/93" */
     34 RCSID("$NetBSD: compat_Ovfork.S,v 1.1.40.1 2011/02/08 16:18:58 bouyer Exp $")
     35 #endif /* SYSLIBC_SCCS and not lint */
     36 
     37 /*
     38  * @(#)vfork.s	4.1 (Berkeley) 12/21/80
     39  * C library -- vfork
     40  */
     41 
     42 WARN_REFERENCES(vfork, \
     43     "warning: reference to compatibility vfork(); include <unistd.h> for correct reference")
     44 
     45 /*
     46  * pid = vfork();
     47  *
     48  * %r1 == 0 in parent process, %r1 == 1 in child process.
     49  * %r0 == pid of child in parent, %r0 == pid of parent in child.
     50  *
     51  * trickery here, due to keith sklower, uses ret to clear the stack,
     52  * and then returns with a jump indirect, since only one person can return
     53  * with a ret off this stack... we do the ret before we vfork!
     54  */
     55 
     56 ENTRY(vfork, 0)
     57 	movl	16(%fp),%r2	# save return address before we smash it
     58 	movab	here,16(%fp)
     59 	ret
     60 here:
     61 	chmk	$ SYS_vfork
     62 	bcs	err		# if failed, set errno and return -1
     63 	/* this next trick is Chris Torek's fault */
     64 	mnegl	%r1,%r1		# %r1 = 0xffffffff if child, 0 if parent
     65 	bicl2	%r1,%r0		# %r0 &= ~%r1, i.e., 0 if child, else unchanged
     66 	jmp	(%r2)
     67 
     68 err:
     69 #ifdef _REENTRANT
     70 	pushr	$0x5
     71 	calls	$0,_C_LABEL(__errno)
     72 	movl	(%sp)+,(%r0)
     73 	mnegl	$1,%r0
     74 	rsb
     75 #else
     76 	movl	%r0,_C_LABEL(errno)
     77 	mnegl	$1,%r0
     78 	jmp	(%r2)
     79 #endif
     80 END(vfork)
     81