1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
30
31 #include <stdarg.h>
32 #include <stdlib.h>
33 #include <unistd.h>
34 #include <stdio.h>
35 #include <ucontext.h>
36
37 __weak_reference(__makecontext, makecontext);
38
39 void _ctx_done(ucontext_t *ucp);
40 void _ctx_start(void);
41
42 void
_ctx_done(ucontext_t * ucp)43 _ctx_done(ucontext_t *ucp)
44 {
45 if (ucp->uc_link == NULL)
46 exit(0);
47 else {
48 /* invalidate context */
49 ucp->uc_mcontext.mc_len = 0;
50
51 setcontext((const ucontext_t *)ucp->uc_link);
52
53 abort(); /* should never return from above call */
54 }
55 }
56
57 void
__makecontext(ucontext_t * ucp,void (* start)(void),int argc,...)58 __makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...)
59 {
60 mcontext_t *mc;
61 char *sp;
62 va_list ap;
63 int i, regargs, stackargs;
64
65 /* Sanity checks */
66 if ((ucp == NULL) || (argc < 0)
67 || (ucp->uc_stack.ss_sp == NULL)
68 || (ucp->uc_stack.ss_size < MINSIGSTKSZ)) {
69 /* invalidate context */
70 ucp->uc_mcontext.mc_len = 0;
71 return;
72 }
73
74 /*
75 * The stack must have space for the frame pointer, saved
76 * link register, overflow arguments, and be 16-byte
77 * aligned.
78 */
79 stackargs = (argc > 8) ? argc - 8 : 0;
80 sp = (char *) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size
81 - sizeof(uintptr_t)*(stackargs + 2);
82 sp = (char *)((uintptr_t)sp & ~0x1f);
83
84 mc = &ucp->uc_mcontext;
85
86 /*
87 * Up to 8 register args. Assumes all args are 64-bit and
88 * integer only. Not sure how to cater for floating point.
89 */
90 regargs = (argc > 8) ? 8 : argc;
91 va_start(ap, argc);
92 for (i = 0; i < regargs; i++)
93 mc->mc_gpr[3 + i] = va_arg(ap, uint64_t);
94
95 /*
96 * Overflow args go onto the stack
97 */
98 if (argc > 8) {
99 uint64_t *argp;
100
101 /* Skip past frame pointer and saved LR */
102 #if !defined(_CALL_ELF) || _CALL_ELF == 1
103 argp = (uint64_t *)sp + 6;
104 #else
105 argp = (uint64_t *)sp + 4;
106 #endif
107
108 for (i = 0; i < stackargs; i++)
109 *argp++ = va_arg(ap, uint64_t);
110 }
111 va_end(ap);
112
113 /*
114 * Use caller-saved regs 14/15 to hold params that _ctx_start
115 * will use to invoke the user-supplied func
116 */
117 #if !defined(_CALL_ELF) || _CALL_ELF == 1
118 /* Cast to ensure this is treated as a function descriptor. */
119 mc->mc_srr0 = *(uintptr_t *)_ctx_start;
120 #else
121 mc->mc_srr0 = (uintptr_t) _ctx_start;
122 #endif
123 mc->mc_gpr[1] = (uintptr_t) sp; /* new stack pointer */
124 mc->mc_gpr[14] = (uintptr_t) start; /* r14 <- start */
125 mc->mc_gpr[15] = (uintptr_t) ucp; /* r15 <- ucp */
126 }
127