1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27/*	Copyright (c) 1988 AT&T	*/
28/*	  All Rights Reserved  	*/
29
30#pragma ident	"%Z%%M%	%I%	%E% SMI"
31
32#pragma weak _makecontext = makecontext
33
34#include "lint.h"
35#include <stdarg.h>
36#include <ucontext.h>
37#include <sys/stack.h>
38
39/*
40 * The ucontext_t that the user passes in must have been primed with a
41 * call to getcontext(2), have the uc_stack member set to reflect the
42 * stack which this context will use, and have the uc_link member set
43 * to the context which should be resumed when this context returns.
44 * When makecontext() returns, the ucontext_t will be set to run the
45 * given function with the given parameters on the stack specified by
46 * uc_stack, and which will return to the ucontext_t specified by uc_link.
47 */
48
49static void resumecontext(void);
50
51void
52makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
53{
54	long *sp;
55	long *tsp;
56	va_list ap;
57	size_t size;
58
59	ucp->uc_mcontext.gregs[EIP] = (greg_t)func;
60
61	size = sizeof (long) * (argc + 1);
62
63	sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
64	    ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1));
65
66	tsp = sp + 1;
67
68	va_start(ap, argc);
69
70	while (argc-- > 0) {
71		*tsp++ = va_arg(ap, long);
72	}
73
74	va_end(ap);
75
76	*sp = (long)resumecontext;		/* return address */
77
78	ucp->uc_mcontext.gregs[UESP] = (greg_t)sp;
79}
80
81
82static void
83resumecontext(void)
84{
85	ucontext_t uc;
86
87	(void) getcontext(&uc);
88	(void) setcontext(uc.uc_link);
89}
90