1 /*
2 * Copyright (c) 2007 Matthew T. Emmerton <matt@gsicomp.on.ca>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Neither the name of the author nor the names of its contributors
11 * may be used to endorse or promote products derived from this software
12 * without specific prior written permission.
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 #include "namespace.h"
28 #include <sys/param.h>
29 #include <sys/signal.h>
30 #include <sys/ucontext.h>
31
32 #include <errno.h>
33 #include <stdarg.h>
34 #include <stdlib.h>
35 #include <unistd.h>
36 #include <signal.h>
37 #include "un-namespace.h"
38
39 int _swapcontext(ucontext_t *, const ucontext_t *);
40 int _setcontext(const ucontext_t *);
41
42 /*
43 * We need to block most signals during a context switch so we do not
44 * dispatch a signal vector during a context switch.
45 */
46 #if 0
47 static sigset_t sigset_block_all;
48
49 static void __sigset_block_all_setup(void) __attribute__ ((constructor));
50
51 static void
52 __sigset_block_all_setup(void)
53 {
54 sigfillset(&sigset_block_all);
55 sigdelset(&sigset_block_all, SIGSEGV);
56 sigdelset(&sigset_block_all, SIGBUS);
57 sigdelset(&sigset_block_all, SIGILL);
58 }
59 #endif
60
61 /*
62 * Save the calling context in (oucp) then switch to (ucp).
63 */
64 int
_swapcontext(ucontext_t * oucp,const ucontext_t * ucp)65 _swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
66 {
67 int ret;
68
69 if (getcontext(oucp) == 0) {
70 if (ucp->uc_mcontext.mc_len == 0)
71 ret = -1;
72 else
73 ret = sigreturn(__DECONST(ucontext_t *, ucp));
74 } else {
75 ret = 0;
76 }
77 return(ret);
78 }
79
80 /*
81 * Switch to the target context, use sigreturn() to properly restore
82 * everything, including rflags and to avoid scribbling over the
83 * target stack's red-zone.
84 *
85 * Note that setcontext() can be called with a ucontext from a signal,
86 * so the signal state must be restored and there is really no way to
87 * avoid making a system call :-(
88 */
89 int
_setcontext(const ucontext_t * ucp)90 _setcontext(const ucontext_t *ucp)
91 {
92 int ret;
93
94 /*
95 * Return failure if the context is invalid
96 */
97 if (ucp->uc_mcontext.mc_len == 0)
98 return -1;
99
100 /*
101 * XXX: shouldn't sigreturn() take const? or does it modify ucp?
102 */
103 ret = sigreturn(__DECONST(ucontext_t *, ucp));
104
105 return(ret);
106 }
107
108 __weak_reference(_swapcontext, swapcontext);
109 __weak_reference(_setcontext, setcontext);
110