1*b3731ba2Sryo /* $NetBSD: makecontext.c,v 1.2 2018/11/16 10:51:08 ryo Exp $ */
2beb9c6d1Smatt
3beb9c6d1Smatt /*-
4beb9c6d1Smatt * Copyright (c) 2014 The NetBSD Foundation, Inc.
5beb9c6d1Smatt * All rights reserved.
6beb9c6d1Smatt *
7beb9c6d1Smatt * This code is derived from software contributed to The NetBSD Foundation
8beb9c6d1Smatt * by Matt Thomas of 3am Software Foundry.
9beb9c6d1Smatt *
10beb9c6d1Smatt * Redistribution and use in source and binary forms, with or without
11beb9c6d1Smatt * modification, are permitted provided that the following conditions
12beb9c6d1Smatt * are met:
13beb9c6d1Smatt * 1. Redistributions of source code must retain the above copyright
14beb9c6d1Smatt * notice, this list of conditions and the following disclaimer.
15beb9c6d1Smatt * 2. Redistributions in binary form must reproduce the above copyright
16beb9c6d1Smatt * notice, this list of conditions and the following disclaimer in the
17beb9c6d1Smatt * documentation and/or other materials provided with the distribution.
18beb9c6d1Smatt *
19beb9c6d1Smatt * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20beb9c6d1Smatt * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21beb9c6d1Smatt * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22beb9c6d1Smatt * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23beb9c6d1Smatt * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24beb9c6d1Smatt * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25beb9c6d1Smatt * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26beb9c6d1Smatt * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27beb9c6d1Smatt * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28beb9c6d1Smatt * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29beb9c6d1Smatt * POSSIBILITY OF SUCH DAMAGE.
30beb9c6d1Smatt */
31beb9c6d1Smatt
32beb9c6d1Smatt #include <sys/cdefs.h>
33beb9c6d1Smatt #if defined(LIBC_SCCS) && !defined(lint)
34*b3731ba2Sryo __RCSID("$NetBSD: makecontext.c,v 1.2 2018/11/16 10:51:08 ryo Exp $");
35beb9c6d1Smatt #endif
36beb9c6d1Smatt
37beb9c6d1Smatt #include <stddef.h>
38beb9c6d1Smatt #include <inttypes.h>
39beb9c6d1Smatt #include <ucontext.h>
40beb9c6d1Smatt #include "extern.h"
41beb9c6d1Smatt
42beb9c6d1Smatt #include <stdarg.h>
43beb9c6d1Smatt
44beb9c6d1Smatt void
makecontext(ucontext_t * ucp,void (* func)(void),int argc,...)45beb9c6d1Smatt makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
46beb9c6d1Smatt {
47beb9c6d1Smatt __greg_t * const gr = ucp->uc_mcontext.__gregs;
48beb9c6d1Smatt __uint64_t *sp;
49beb9c6d1Smatt
50beb9c6d1Smatt /* Compute and align stack pointer. */
51beb9c6d1Smatt sp = (uint64_t *)
52beb9c6d1Smatt (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & -16LL);
53beb9c6d1Smatt /* Allocate necessary stack space for arguments exceeding x0-7. */
54beb9c6d1Smatt if (argc > 8)
55beb9c6d1Smatt sp -= argc - 8;
56beb9c6d1Smatt gr[_REG_SP] = (__greg_t)(uintptr_t)sp;
57beb9c6d1Smatt /* Wipe out frame pointer. */
58beb9c6d1Smatt gr[_REG_X29] = 0;
59beb9c6d1Smatt /* Arrange for return via the trampoline code. */
60beb9c6d1Smatt gr[_REG_X30] = (__greg_t)(uintptr_t)_resumecontext;
61beb9c6d1Smatt gr[_REG_PC] = (__greg_t)(uintptr_t)func;
62beb9c6d1Smatt
63beb9c6d1Smatt va_list ap;
64beb9c6d1Smatt va_start(ap, argc);
65beb9c6d1Smatt
66*b3731ba2Sryo /* Pass up to eight arguments in x0-x7. */
67beb9c6d1Smatt for (int i = 0; i < argc && i < 8; i++) {
68*b3731ba2Sryo gr[_REG_X0 + i] = va_arg(ap, __greg_t);
69beb9c6d1Smatt }
70beb9c6d1Smatt
71beb9c6d1Smatt /* Pass any additional arguments on the stack. */
72beb9c6d1Smatt for (int i = 8; i < argc; i++) {
73beb9c6d1Smatt *sp++ = va_arg(ap, uint64_t);
74beb9c6d1Smatt }
75beb9c6d1Smatt va_end(ap);
76beb9c6d1Smatt }
77