makecontext.c revision 1.6 
1/*	$NetBSD: makecontext.c,v 1.6 2011/09/20 08:42:29 joerg 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 <sys/cdefs.h>
33#if defined(LIBC_SCCS) && !defined(lint)
34__RCSID("$NetBSD: makecontext.c,v 1.6 2011/09/20 08:42:29 joerg Exp $");
35#endif
36
37#include <stddef.h>
38#include <inttypes.h>
39#include <ucontext.h>
40#include "extern.h"
41
42#include <stdarg.h>
43
44void __resumecontext(void) __dead;
45
46void
47makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
48{
49	__greg_t *gr = ucp->uc_mcontext.__gregs;
50	int i;
51	unsigned long *sp;
52	va_list ap;
53
54	/* Compute and align stack pointer. */
55	sp = (unsigned long *)
56	    (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~0x7);
57	/* Allocate necessary stack space for arguments exceeding a0-5. */
58	if (argc > 6)
59		sp -= (argc - 6);
60	gr[_REG_SP] = (__greg_t)sp;
61	/* Arrange for return via the trampoline code. */
62	gr[_REG_RA] = (__greg_t)__resumecontext;
63	gr[_REG_PC] = (__greg_t)func;
64	gr[_REG_PV] = (__greg_t)func;
65
66	va_start(ap, argc);
67	/* Pass up to six arguments in a0-5. */
68	for (i = 0; i < argc && i < 6; i++)
69		gr[_REG_A0 + i] = va_arg(ap, unsigned long);
70	/* Pass any additional arguments on the stack. */
71	for (argc -= i; argc > 0; argc--)
72		*sp++ = va_arg(ap, unsigned long);
73	va_end(ap);
74}
75