makecontext.c revision 1.4 
1/*	$NetBSD: makecontext.c,v 1.4 2008/04/28 20:22:56 martin 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 1.4 2008/04/28 20:22:56 martin Exp $");
35#endif
36
37#include <inttypes.h>
38#include <stddef.h>
39#include <ucontext.h>
40#include "extern.h"
41
42#include <stdarg.h>
43
44void
45makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
46{
47	__greg_t *gr = ucp->uc_mcontext.__gregs;
48	uintptr_t *sp;
49	int i;
50	va_list ap;
51
52	void __resumecontext(void);
53
54	/* LINTED uintptr_t is safe */
55	sp  = (uintptr_t *)
56	    ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
57	/* LINTED uintptr_t is safe */
58	sp -= (argc >= 4 ? argc : 4);	/* Make room for >=4 arguments. */
59	sp  = (uintptr_t *)
60	      ((uintptr_t)sp & ~0x7);	/* Align on double-word boundary. */
61
62	gr[_REG_SP]  = (__greg_t)sp;
63	gr[_REG_RA]  = (__greg_t)__resumecontext;
64	gr[_REG_T9]  = (__greg_t)func;	/* required for .abicalls */
65	gr[_REG_EPC] = (__greg_t)func;
66
67	/* Construct argument list. */
68	va_start(ap, argc);
69	/* Up to the first four arguments are passed in $a0-3. */
70	for (i = 0; i < argc && i < 4; i++)
71		/* LINTED uintptr_t is safe */
72		gr[_REG_A0 + i] = va_arg(ap, uintptr_t);
73	/* Pass remaining arguments on the stack above the $a0-3 gap. */
74	for (sp += 4; i < argc; i++)
75		/* LINTED uintptr_t is safe */
76		*sp++ = va_arg(ap, uintptr_t);
77	va_end(ap);
78}
79