makecontext.c revision 1.2 
1/*	$NetBSD: makecontext.c,v 1.2 2005/04/09 20:46:56 matt Exp $	*/
2
3/*-
4 * Copyright (c) 2003 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.
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 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *        This product includes software developed by the NetBSD
21 *        Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 *    contributors may be used to endorse or promote products derived
24 *    from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#include <sys/cdefs.h>
40#if defined(LIBC_SCCS) && !defined(lint)
41__RCSID("$NetBSD: makecontext.c,v 1.2 2005/04/09 20:46:56 matt Exp $");
42#endif
43
44#include <stddef.h>
45#include <inttypes.h>
46#include <ucontext.h>
47#include "extern.h"
48
49#include <stdarg.h>
50
51void
52makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
53{
54	__greg_t *gr = ucp->uc_mcontext.__gregs;
55	va_list ap;
56	int *sp;
57	int i;
58
59	/* Compute and align stack pointer. */
60	sp = (int *)
61	    (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~0x3);
62
63	/*
64	 * Allocate necessary stack space for arguments including arg count
65	 * and call frame
66	 */
67	sp -= argc + 1 + 5;
68
69	va_start(ap, argc);
70	sp[5] = argc;
71	for (i = 1; argc > 0; argc--, i++)
72		sp[5 + i] = va_arg(ap, int);
73	va_end(ap);
74
75	sp[0] = 0;			/* condition handler is null */
76	sp[1] = 0x20000000;		/* make this a CALLS frame */
77	sp[2] = 0;			/* saved argument pointer */
78	sp[3] = 0;			/* saved frame pointer */
79	sp[4] = (int)_resumecontext+2;	/* return via trampoline code */
80
81	gr[_REG_AP] = (__greg_t)(sp + 5);
82	gr[_REG_SP] = (__greg_t)sp;
83	gr[_REG_FP] = (__greg_t)sp;
84	gr[_REG_PC] = (__greg_t)func+2;
85
86}
87