1/* $NetBSD: swapcontext.S,v 1.4 2018/11/23 12:39:18 skrll Exp $ */
2
3/*-
4 * Copyright (c) 2014 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Matt Thomas of 3am Software Foundry.
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: swapcontext.S,v 1.4 2018/11/23 12:39:18 skrll Exp $")
37#endif /* LIBC_SCCS && !lint */
38
39/* LINTSTUB: int swapcontext(ucontext_t * restrict, ucontext_t * restrict); */
40
41ENTRY(swapcontext)
42	sub	sp, sp, #32		/* allocate stack frame */
43	stp	x29, x30, [sp, #16]	/* save FP & LR */
44	add	x29, sp, #16		/* new FP */
45	stp	x0, x1, [sp, #0]	/* save oucp (x0) & ucp (x1) */
46
47	bl	_C_LABEL(_getcontext)	/* getcontext(oucp) */
48	mov	x3, x0			/* save return value */
49
50	ldp	x2, x0, [sp, #0]	/* load oucp (x2) & ucp (x0) */
51	ldp	x29, x30, [sp, #16]	/* restore FP & LR */
52	add	sp, sp, #32		/* free stack frame */
53
54	/*
55	 * Assume _getcontext succeeded.
56	 */
57	mov	x4, sp			/* Get SP */
58	str	x4, [x2, #_UC_REGS_SP]	/* Adjust saved SP. */
59	str	x30, [x2, #_UC_REGS_PC]	/* Adjust saved PC. */
60
61	cbnz	x3, 1f
62	b	_C_LABEL(setcontext)	/* setcontext if getcontext succeeded */
631:
64	mov	x0, x3			/* restore getcontext return value */
65	ret				/* return on error from getcontext */
66END(swapcontext)
67