1 /* $NetBSD: makecontext.c,v 1.10 2025/04/24 23:54:13 riastradh 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 1.10 2025/04/24 23:54:13 riastradh Exp $");
35 #endif
36
37 #include <sys/param.h>
38
39 #include <inttypes.h>
40 #include <stdarg.h>
41 #include <stddef.h>
42 #include <ucontext.h>
43
44 #include "extern.h"
45
46 void __resumecontext(void) __dead;
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 __greg_t *sp;
53 int i;
54 va_list ap;
55
56 /* LINTED uintptr_t is safe */
57 sp = (__greg_t *)
58 ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
59 #if defined(__mips_o32) || defined(__mips_o64)
60 sp -= (argc >= 4 ? argc : 4); /* Make room for >=4 arguments. */
61 #elif defined(__mips_n32) || defined(__mips_n64)
62 sp -= (argc > 8 ? argc - 8 : 0); /* Make room for > 8 arguments. */
63 #endif
64 /* LINTED uintptr_t is safe */
65 sp = (__greg_t *)((uintptr_t)sp & ~STACK_ALIGNBYTES);
66
67 gr[_REG_SP] = (intptr_t)sp;
68 gr[_REG_RA] = (intptr_t)__resumecontext;
69 gr[_REG_T9] = (intptr_t)func; /* required for .abicalls */
70 gr[_REG_EPC] = (intptr_t)func;
71
72 /* Construct argument list. */
73 va_start(ap, argc);
74 #if defined(__mips_o32) || defined(__mips_o64)
75 /* Up to the first four arguments are passed in $a0-3. */
76 for (i = 0; i < argc && i < 4; i++)
77 /* LINTED __greg_t is safe */
78 gr[_REG_A0 + i] = va_arg(ap, __greg_t);
79 /* Pass remaining arguments on the stack above the $a0-3 gap. */
80 sp += i;
81 #endif
82 #if defined(__mips_n32) || defined(__mips_n64)
83 /* Up to the first 8 arguments are passed in $a0-7. */
84 for (i = 0; i < argc && i < 8; i++)
85 /* LINTED __greg_t is safe */
86 gr[_REG_A0 + i] = va_arg(ap, __greg_t);
87 /* Pass remaining arguments on the stack */
88 #endif
89 for (; i < argc; i++)
90 /* LINTED uintptr_t is safe */
91 *sp++ = va_arg(ap, __greg_t);
92 va_end(ap);
93 }
94