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      1 /*	$NetBSD: resumecontext.S,v 1.8 2013/07/17 03:04:54 matt 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 Klaus Klein.
      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 <machine/asm.h>
     33 #include "assym.h"
     34 
     35 #if defined(LIBC_SCCS) && !defined(lint)
     36 	RCSID("$NetBSD: resumecontext.S,v 1.8 2013/07/17 03:04:54 matt Exp $")
     37 #endif /* LIBC_SCCS && !lint */
     38 
     39 /*
     40  * This assembly-language implementation differs from the (obvious)
     41  * C-language implementation only in not clobbering the previous
     42  * function's return address (us), which is the point of the exercise.
     43  */
     44 
     45 ENTRY(_resumecontext)
     46 	subl	#(4 + UC_SIZE),%sp	/* retaddr preservation + ucontext_t */
     47 	lea	(%sp),%a0
     48 	movl	%a0,-(%sp)
     49 	jbsr	PIC_PLT(_C_LABEL(_getcontext))
     50 	movl	(4 + UC_LINK)(%sp),(%sp)	/* uc_link */
     51 	tstl	(%sp)			/* check for NULL */
     52 	jne	1f
     53 	jbsr	PIC_PLT(_C_LABEL(exit))	/* cleanly exit(0) */
     54 	jmp	2f
     55 1:	jbsr	PIC_PLT(_C_LABEL(setcontext))
     56 	/* NOTREACHED */
     57 	/* But just in case... */
     58 2:	movl	#-1,(%sp)
     59 	jbsr	PIC_PLT(_C_LABEL(_exit))
     60 	/* NOTREACHED */
     61 END(_resumecontext)
     62