1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2004 Suleiman Souhlal
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31
32 #include <sys/param.h>
33
34 #include <stdarg.h>
35 #include <stdlib.h>
36 #include <unistd.h>
37 #include <stdio.h>
38 #include <ucontext.h>
39
40 __weak_reference(__makecontext, makecontext);
41
42 void _ctx_done(ucontext_t *ucp);
43 void _ctx_start(void);
44
45 void
_ctx_done(ucontext_t * ucp)46 _ctx_done(ucontext_t *ucp)
47 {
48 if (ucp->uc_link == NULL)
49 exit(0);
50 else {
51 /* invalidate context */
52 ucp->uc_mcontext.mc_len = 0;
53
54 setcontext((const ucontext_t *)ucp->uc_link);
55
56 abort(); /* should never return from above call */
57 }
58 }
59
60 void
__makecontext(ucontext_t * ucp,void (* start)(void),int argc,...)61 __makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...)
62 {
63 mcontext_t *mc;
64 char *sp;
65 va_list ap;
66 int i, regargs, stackargs;
67
68 /* Sanity checks */
69 if ((ucp == NULL) || (argc < 0)
70 || (ucp->uc_stack.ss_sp == NULL)
71 || (ucp->uc_stack.ss_size < MINSIGSTKSZ)) {
72 /* invalidate context */
73 ucp->uc_mcontext.mc_len = 0;
74 return;
75 }
76
77 /*
78 * The stack must have space for the frame pointer, saved
79 * link register, overflow arguments, and be 16-byte
80 * aligned.
81 */
82 stackargs = (argc > 8) ? argc - 8 : 0;
83 sp = (char *) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size
84 - sizeof(uintptr_t)*(stackargs + 2);
85 sp = (char *)((uintptr_t)sp & ~0x1f);
86
87 mc = &ucp->uc_mcontext;
88
89 /*
90 * Up to 8 register args. Assumes all args are 64-bit and
91 * integer only. Not sure how to cater for floating point.
92 */
93 regargs = (argc > 8) ? 8 : argc;
94 va_start(ap, argc);
95 for (i = 0; i < regargs; i++)
96 mc->mc_gpr[3 + i] = va_arg(ap, uint64_t);
97
98 /*
99 * Overflow args go onto the stack
100 */
101 if (argc > 8) {
102 uint64_t *argp;
103
104 /* Skip past frame pointer and saved LR */
105 argp = (uint64_t *)sp + 6;
106
107 for (i = 0; i < stackargs; i++)
108 *argp++ = va_arg(ap, uint64_t);
109 }
110 va_end(ap);
111
112 /*
113 * Use caller-saved regs 14/15 to hold params that _ctx_start
114 * will use to invoke the user-supplied func
115 */
116 mc->mc_srr0 = *(uintptr_t *)_ctx_start;
117 mc->mc_gpr[1] = (uintptr_t) sp; /* new stack pointer */
118 mc->mc_gpr[14] = (uintptr_t) start; /* r14 <- start */
119 mc->mc_gpr[15] = (uintptr_t) ucp; /* r15 <- ucp */
120 }
121