1 /* $NetBSD: makecontext.c,v 1.4 2012/03/22 17:32:22 christos 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 *
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 2012/03/22 17:32:22 christos 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
44 void
makecontext(ucontext_t * ucp,void (* func)(void),int argc,...)45 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
46 {
47 __greg_t *gr = ucp->uc_mcontext.__gregs;
48 va_list ap;
49 int *sp;
50 int i;
51
52 /* Compute and align stack pointer. */
53 sp = (int *)
54 (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~0x3);
55
56 /*
57 * Allocate necessary stack space for arguments including arg count
58 * and call frame
59 */
60 sp -= argc + 1 + 5;
61
62 va_start(ap, argc);
63 sp[5] = argc;
64 for (i = 1; argc > 0; argc--, i++)
65 sp[5 + i] = va_arg(ap, int);
66 va_end(ap);
67
68 sp[0] = 0; /* condition handler is null */
69 sp[1] = 0x20000000; /* make this a CALLS frame */
70 sp[2] = 0; /* saved argument pointer */
71 sp[3] = 0; /* saved frame pointer */
72 sp[4] = (int)(uintptr_t)_resumecontext+2;/* return via trampoline code */
73
74 gr[_REG_AP] = (__greg_t)(uintptr_t)(sp + 5);
75 gr[_REG_SP] = (__greg_t)(uintptr_t)sp;
76 gr[_REG_FP] = (__greg_t)(uintptr_t)sp;
77 gr[_REG_PC] = (__greg_t)(uintptr_t)func+2;
78
79 }
80