1 /* $NetBSD: makecontext.c,v 1.1 2014/09/19 17:36:25 matt 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 1.1 2014/09/19 17:36:25 matt 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 long *sp;
53 int i;
54 va_list ap;
55
56 /* LINTED uintptr_t is safe */
57 sp = (long *)
58 ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
59 /* LINTED uintptr_t is safe */
60 sp -= 1 + (argc > 8 ? argc - 8: 0); /* Make room for call frame. */
61 sp = (long *) ((uintptr_t)sp & -16L); /* Align on 16byte boundary. */
62
63 /*
64 * Start executing at <func> -- when <func> completes, return to
65 * <_resumecontext>.
66 */
67 gr[_REG_SP] = (uintptr_t)sp;
68 gr[_REG_RA] = (uintptr_t)_resumecontext;
69 gr[_REG_PC] = (uintptr_t)func;
70
71 /* Wipe out stack frame backchain pointer. */
72 *sp = 0;
73
74 /* Construct argument list. */
75 va_start(ap, argc);
76 /* Up to the first six arguments are passed in x18-x25 */
77 for (i = 0; i < argc && i < 8; i++)
78 gr[_REG_A0 + i] = va_arg(ap, int);
79 /* Pass remaining arguments on the stack above the backchain/lr gap. */
80 for (sp += 0; i < argc; i++)
81 *sp++ = va_arg(ap, long);
82 va_end(ap);
83 }
84