Remove some unnecessary inclusions of <sys/cdefs.h> across the tree.
[dragonfly.git] / lib / libc / gen / ucontext.c
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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.
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25 */
26
e2b7bcae 27#include "namespace.h"
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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>
e2b7bcae 37#include "un-namespace.h"
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38
39/* Prototypes */
40__weak_reference(_swapcontext, swapcontext);
41__weak_reference(_setcontext, setcontext);
42
43int get_mcontext(mcontext_t *);
44int set_mcontext(const mcontext_t *);
45
46/*
47 * We need to block most signals during a context switch so we do not
48 * dispatch a signal vector during a context switch.
49 */
50static sigset_t sigset_block_all;
51
52static void __sigset_block_all_setup(void) __attribute__ ((constructor));
53
54static void
55__sigset_block_all_setup(void)
56{
57 sigfillset(&sigset_block_all);
58 sigdelset(&sigset_block_all, SIGSEGV);
59 sigdelset(&sigset_block_all, SIGBUS);
60 sigdelset(&sigset_block_all, SIGILL);
61}
62
63/*
64 * Save the calling context in (oucp) then switch to (ucp).
65 *
66 * Block all signals while switching contexts. get_mcontext() returns zero
67 * when retrieving a context.
68 *
69 * When some other thread calls set_mcontext() to resume our thread,
70 * the resume point causes get_mcontext() to return non-zero to us.
71 * Signals will be blocked and we must restore the signal mask before
72 * returning.
73 */
74int
75_swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
76{
77 int ret;
78
79 ret = _sigprocmask(SIG_BLOCK, &sigset_block_all, &oucp->uc_sigmask);
80 if (ret == 0) {
81 if (get_mcontext(&oucp->uc_mcontext) == 0) {
82 ret = set_mcontext(&ucp->uc_mcontext);
83 } else {
84 ret = _sigprocmask(SIG_SETMASK, &oucp->uc_sigmask, NULL);
85 }
86 }
87 return(ret);
88}
89
90/*
91 * Switch to the target context. The current signal mask is saved in ucp
92 * and all signals are blocked. The call to set_mcontext() causes the
93 * specified context to be switched to (usually resuming as a return from
94 * the get_mcontext() procedure). The current context is thrown away.
95 *
96 * The target context being resumed is responsible for restoring the
97 * signal mask appropriate for the target context.
98 */
99int
100_setcontext(ucontext_t *ucp)
101{
102 int ret;
103
104 ret = _sigprocmask(SIG_BLOCK, &sigset_block_all, &ucp->uc_sigmask);
105 if (ret == 0)
106 ret = set_mcontext(&ucp->uc_mcontext);
107 return(ret);
108}
109