1 /* $NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:57 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 1.3 2008/04/28 20:22:57 martin Exp $");
35 #endif
36
37 #include <inttypes.h>
38 #include <stddef.h>
39 #include <ucontext.h>
40 #include "extern.h"
41
42 #if __STDC__
43 #include <stdarg.h>
44 #else
45 #include <varargs.h>
46 #endif
47
48 void
makecontext(ucontext_t * ucp,void (* func)(void),int argc,...)49 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
50 {
51 __greg_t *gr = ucp->uc_mcontext.__gregs;
52 __greg_t sp, *spp;
53 int i;
54 va_list ap;
55
56 sp = (__greg_t) ((uintptr_t)ucp->uc_stack.ss_sp
57 + ucp->uc_stack.ss_size);
58 sp -= 2 + (argc > 8 ? argc - 8: 0); /* Make room for call frame. */
59 sp = (__greg_t) ((uintptr_t)sp & ~0xf);
60
61 /*
62 * Start executing at <func> -- when <func> completes, return to
63 * <_resumecontext>.
64 */
65 gr[_REG_R1] = sp;
66 gr[_REG_LR] = (__greg_t)_resumecontext;
67 gr[_REG_PC] = (__greg_t)func; // XXX -- this is the descriptor address!
68
69 /* Wipe out stack frame backchain pointer. */
70 spp = (__greg_t *)sp;
71 *spp = 0;
72
73 /* Construct argument list. */
74 va_start(ap, argc);
75 /* Up to the first eight arguments are passed in r3-10. */
76 for (i = 0; i < argc && i < 8; i++)
77 gr[_REG_R3 + i] = va_arg(ap, long);
78 /* Pass remaining arguments on the stack above the backchain/lr gap. */
79 for (spp += 2; i < argc; i++)
80 *spp++ = va_arg(ap, long);
81 va_end(ap);
82 }
83