1 /*
2 * Copyright (c) 2003 Marcel Moolenaar
3 * All rights reserved.
4 * Copyright (c) 2012 Markus Pfeiffer <markus.pfeiffer@morphism.de>
5 * All rights reserved.
6 *
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in
11 * the documentation and/or other materials provided with the
12 * distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 */
27
28 #include <sys/cdefs.h>
29 #include <sys/param.h>
30 #include <sys/signal.h>
31 #include <sys/ucontext.h>
32
33 #include <machine/frame.h>
34 #include <machine/tss.h>
35 #include <machine/segments.h>
36
37 #include <signal.h>
38 #include <errno.h>
39 #include <string.h>
40 #include <stdarg.h>
41 #include <stdlib.h>
42 #include <unistd.h>
43
44 void _makecontext(ucontext_t *, void (*)(void), int, ...);
45
46 typedef void (*func_t)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t);
47
48 /* Prototypes */
49 static void makectx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args);
50
51 /*
52 * makecontext() associates a stack with a user thread context and sets
53 * up to call the start function when switched to. The start function
54 * returns to _ctx_start which then calls _ctx_done to terminate the
55 * context.
56 */
57 void
_makecontext(ucontext_t * ucp,void (* start)(void),int argc,...)58 _makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...)
59 {
60 va_list ap;
61 uint64_t *stack_top;
62 uint64_t *argp;
63 int i;
64
65 if (ucp == NULL)
66 return;
67
68 /*
69 * Invalidate a context which did not have a stack associated with
70 * it or for which the stack was too small. The stack check is
71 * kinda silly, though, since we have no control over the stack
72 * usage of the code being set up to run.
73 */
74 if ((ucp->uc_stack.ss_sp == NULL) ||
75 (ucp->uc_stack.ss_size < MINSIGSTKSZ)) {
76 ucp->uc_mcontext.mc_len = 0;
77 }
78 if (argc < 0 || argc > NCARGS)
79 ucp->uc_mcontext.mc_len = 0;
80
81 if (ucp->uc_mcontext.mc_len == sizeof(mcontext_t)) {
82 /*
83 */
84 stack_top = (uint64_t *)((char *)ucp->uc_stack.ss_sp +
85 ucp->uc_stack.ss_size);
86 stack_top = (uint64_t *)((uint64_t)(stack_top) & ~15UL);
87
88 argp = stack_top - 6;
89 stack_top -= 7;
90
91 /* Add all the arguments: */
92 va_start(ap, argc);
93 for (i = 0; i < argc; i++) {
94 argp[i] = va_arg(ap, uint64_t);
95 }
96 va_end(ap);
97 /* The first six arguments are passed via registers. */
98 for (i = argc; i < 6; i++) {
99 argp[i] = 0;
100 }
101
102 /*
103 * Set the machine context to point to the top of the
104 * stack and the program counter to the context start
105 * wrapper. Note that setcontext() pushes the return
106 * address onto the top of the stack, so allow for this
107 * by adjusting the stack downward 1 slot. Also set
108 * %rbp to point to the base of the stack where ucp
109 * is stored.
110 */
111 ucp->uc_mcontext.mc_rdi = (register_t)ucp;
112 ucp->uc_mcontext.mc_rsi = (register_t)start;
113 ucp->uc_mcontext.mc_rdx = (register_t)argp;
114 ucp->uc_mcontext.mc_rbp = 0;
115 ucp->uc_mcontext.mc_rbx = (register_t)stack_top;
116 ucp->uc_mcontext.mc_rsp = (register_t)stack_top;
117 ucp->uc_mcontext.mc_rip = (register_t)makectx_wrapper;
118 ucp->uc_mcontext.mc_ownedfp = _MC_FPOWNED_NONE;
119 ucp->uc_mcontext.mc_fpformat = _MC_FPFMT_NODEV;
120 ucp->uc_mcontext.mc_cs = GSEL(GUCODE_SEL, SEL_UPL);
121 ucp->uc_mcontext.mc_ss = GSEL(GUDATA_SEL, SEL_UPL);
122 ucp->uc_mcontext.mc_onstack = 0;
123 ucp->uc_mcontext.mc_err = 0;
124 }
125 }
126
127 __weak_reference(_makecontext, makecontext);
128
129 /* */
130 static void
makectx_wrapper(ucontext_t * ucp,func_t func,uint64_t * args)131 makectx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args)
132 {
133 (*func)(args[0], args[1], args[2], args[3], args[4], args[5]);
134 if (ucp->uc_link == NULL)
135 exit(0);
136
137 setcontext((const ucontext_t *)ucp->uc_link);
138
139 /* should never reach this */
140 abort();
141 }
142