1 /* $NetBSD: makecontext.c,v 1.4 2009/07/30 20:57:17 dsl Exp $ */
2
3 /*-
4 * Copyright (c) 1999 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 * Modified from the i386 version for x86_64 by fvdl@wasabisystems.com.
32 *
33 */
34
35 #include <sys/cdefs.h>
36 #if defined(LIBC_SCCS) && !defined(lint)
37 __RCSID("$NetBSD: makecontext.c,v 1.4 2009/07/30 20:57:17 dsl Exp $");
38 #endif
39
40 #include <inttypes.h>
41 #include <stddef.h>
42 #include <ucontext.h>
43 #include "extern.h"
44
45 #include <stdarg.h>
46
47 void
makecontext(ucontext_t * ucp,void (* func)(void),int argc,...)48 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
49 {
50 __greg_t *gr = ucp->uc_mcontext.__gregs;
51 uintptr_t *sp;
52 va_list ap;
53 int stackargs, i;
54
55 stackargs = argc - 6;
56
57 /* LINTED __greg_t is safe */
58 gr[_REG_RIP] = (__greg_t)func;
59
60 /* LINTED uintptr_t is safe */
61 sp = (uintptr_t *)
62 ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
63
64 /* LINTED uintptr_t is safe */
65 sp = (uintptr_t *)(((uintptr_t)sp & ~15));
66 sp--;
67 if (stackargs > 0)
68 sp -= stackargs;
69 /* LINTED __greg_t is safe */
70 gr[_REG_RSP] = (__greg_t)sp;
71 gr[_REG_RBP] = (__greg_t)0; /* Wipe out frame pointer. */
72
73 /* Put return address on top of stack. */
74 /* LINTED uintptr_t is safe */
75 *sp++ = (uintptr_t)_resumecontext;
76
77 /*
78 * Construct argument list.
79 * The registers used to pass the first 6 arguments
80 * (rdi, rsi, rdx, rcx, r8, r9) are the first 6 in gregs,
81 * in that order, so those arguments can just be copied to
82 * the gregs array.
83 */
84 va_start(ap, argc);
85 for (i = 0; i < 6 && argc > 0; i++) {
86 argc--;
87 /* LINTED __greg_t is safe */
88 gr[i] = va_arg(ap, __greg_t);
89 }
90
91 while (stackargs-- > 0) {
92 /* LINTED uintptr_t is safe */
93 *sp++ = va_arg(ap, uintptr_t);
94 }
95
96 va_end(ap);
97 }
98