1*27620987Smatt /* $NetBSD: makecontext.c,v 1.1 2014/09/03 19:34:25 matt Exp $ */
2*27620987Smatt
3*27620987Smatt /*-
4*27620987Smatt * Copyright (c) 2001 The NetBSD Foundation, Inc.
5*27620987Smatt * All rights reserved.
6*27620987Smatt *
7*27620987Smatt * This code is derived from software contributed to The NetBSD Foundation
8*27620987Smatt * by Klaus Klein.
9*27620987Smatt *
10*27620987Smatt * Redistribution and use in source and binary forms, with or without
11*27620987Smatt * modification, are permitted provided that the following conditions
12*27620987Smatt * are met:
13*27620987Smatt * 1. Redistributions of source code must retain the above copyright
14*27620987Smatt * notice, this list of conditions and the following disclaimer.
15*27620987Smatt * 2. Redistributions in binary form must reproduce the above copyright
16*27620987Smatt * notice, this list of conditions and the following disclaimer in the
17*27620987Smatt * documentation and/or other materials provided with the distribution.
18*27620987Smatt *
19*27620987Smatt * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20*27620987Smatt * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21*27620987Smatt * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22*27620987Smatt * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23*27620987Smatt * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24*27620987Smatt * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25*27620987Smatt * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26*27620987Smatt * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27*27620987Smatt * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28*27620987Smatt * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29*27620987Smatt * POSSIBILITY OF SUCH DAMAGE.
30*27620987Smatt */
31*27620987Smatt
32*27620987Smatt #include <sys/cdefs.h>
33*27620987Smatt #if defined(LIBC_SCCS) && !defined(lint)
34*27620987Smatt __RCSID("$NetBSD: makecontext.c,v 1.1 2014/09/03 19:34:25 matt Exp $");
35*27620987Smatt #endif
36*27620987Smatt
37*27620987Smatt #include <inttypes.h>
38*27620987Smatt #include <stddef.h>
39*27620987Smatt #include <ucontext.h>
40*27620987Smatt #include "extern.h"
41*27620987Smatt
42*27620987Smatt #if __STDC__
43*27620987Smatt #include <stdarg.h>
44*27620987Smatt #else
45*27620987Smatt #include <varargs.h>
46*27620987Smatt #endif
47*27620987Smatt
48*27620987Smatt void
makecontext(ucontext_t * ucp,void (* func)(void),int argc,...)49*27620987Smatt makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
50*27620987Smatt {
51*27620987Smatt __greg_t *gr = ucp->uc_mcontext.__gregs;
52*27620987Smatt int *sp;
53*27620987Smatt int i;
54*27620987Smatt va_list ap;
55*27620987Smatt
56*27620987Smatt /* LINTED uintptr_t is safe */
57*27620987Smatt sp = (int *)
58*27620987Smatt ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
59*27620987Smatt /* LINTED uintptr_t is safe */
60*27620987Smatt sp -= 1 + (argc > 6 ? argc - 6: 0); /* Make room for call frame. */
61*27620987Smatt sp = (int *) ((uintptr_t)sp & ~0x3); /* Align on word boundary. */
62*27620987Smatt
63*27620987Smatt /*
64*27620987Smatt * Start executing at <func> -- when <func> completes, return to
65*27620987Smatt * <_resumecontext>.
66*27620987Smatt */
67*27620987Smatt gr[_REG_SP] = (uintptr_t)sp;
68*27620987Smatt gr[_REG_LR] = (uintptr_t)_resumecontext;
69*27620987Smatt gr[_REG_PC] = (uintptr_t)func;
70*27620987Smatt
71*27620987Smatt /* Wipe out stack frame backchain pointer. */
72*27620987Smatt *sp = 0;
73*27620987Smatt
74*27620987Smatt /* Construct argument list. */
75*27620987Smatt va_start(ap, argc);
76*27620987Smatt /* Up to the first six arguments are passed in r3-r8. */
77*27620987Smatt for (i = 0; i < argc && i < 6; i++)
78*27620987Smatt gr[_REG_R3 + i] = va_arg(ap, int);
79*27620987Smatt /* Pass remaining arguments on the stack above the backchain/lr gap. */
80*27620987Smatt for (sp += 2; i < argc; i++)
81*27620987Smatt *sp++ = va_arg(ap, int);
82*27620987Smatt va_end(ap);
83*27620987Smatt }
84