1 /* $NetBSD: makecontext.c,v 1.2 2018/11/16 10:51:08 ryo Exp $ */
2
3 /*-
4 * Copyright (c) 2014 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 of 3am Software Foundry.
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 1.2 2018/11/16 10:51:08 ryo 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 * const gr = ucp->uc_mcontext.__gregs;
48 __uint64_t *sp;
49
50 /* Compute and align stack pointer. */
51 sp = (uint64_t *)
52 (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & -16LL);
53 /* Allocate necessary stack space for arguments exceeding x0-7. */
54 if (argc > 8)
55 sp -= argc - 8;
56 gr[_REG_SP] = (__greg_t)(uintptr_t)sp;
57 /* Wipe out frame pointer. */
58 gr[_REG_X29] = 0;
59 /* Arrange for return via the trampoline code. */
60 gr[_REG_X30] = (__greg_t)(uintptr_t)_resumecontext;
61 gr[_REG_PC] = (__greg_t)(uintptr_t)func;
62
63 va_list ap;
64 va_start(ap, argc);
65
66 /* Pass up to eight arguments in x0-x7. */
67 for (int i = 0; i < argc && i < 8; i++) {
68 gr[_REG_X0 + i] = va_arg(ap, __greg_t);
69 }
70
71 /* Pass any additional arguments on the stack. */
72 for (int i = 8; i < argc; i++) {
73 *sp++ = va_arg(ap, uint64_t);
74 }
75 va_end(ap);
76 }
77