1/*	$NetBSD: resumecontext.S,v 1.7 2013/07/16 22:12:20 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 1.7 2013/07/16 22:12:20 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
45ENTRY(_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
551:	jbsr	PIC_PLT(_C_LABEL(setcontext))
56	/* NOTREACHED */
57	/* But just in case... */
582:	movl	#-1,(%sp)
59	jbsr	PIC_PLT(_C_LABEL(_exit))
60	/* NOTREACHED */
61END(_resumecontext)
62