xref: /openbsd/lib/libevent/signal.c (revision 91f110e0) 
1 /*	$OpenBSD: signal.c,v 1.16 2013/04/29 00:28:23 okan Exp $	*/
2 
3 /*
4  * Copyright 2000-2002 Niels Provos <provos@citi.umich.edu>
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  * 3. The name of the author may not be used to endorse or promote products
16  *    derived from this software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  */
29 #ifdef HAVE_CONFIG_H
30 #include "config.h"
31 #endif
32 
33 #ifdef WIN32
34 #define WIN32_LEAN_AND_MEAN
35 #include <winsock2.h>
36 #include <windows.h>
37 #undef WIN32_LEAN_AND_MEAN
38 #endif
39 #include <sys/types.h>
40 #ifdef HAVE_SYS_TIME_H
41 #include <sys/time.h>
42 #endif
43 #include <sys/queue.h>
44 #ifdef HAVE_SYS_SOCKET_H
45 #include <sys/socket.h>
46 #endif
47 #include <signal.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #ifdef HAVE_UNISTD_H
52 #include <unistd.h>
53 #endif
54 #include <errno.h>
55 #ifdef HAVE_FCNTL_H
56 #include <fcntl.h>
57 #endif
58 #include <assert.h>
59 
60 #include "event.h"
61 #include "event-internal.h"
62 #include "evsignal.h"
63 #include "evutil.h"
64 #include "log.h"
65 
66 struct event_base *evsignal_base = NULL;
67 
68 static void evsignal_handler(int sig);
69 
70 /* Callback for when the signal handler write a byte to our signaling socket */
71 static void
72 evsignal_cb(int fd, short what, void *arg)
73 {
74 	static char signals[1];
75 #ifdef WIN32
76 	SSIZE_T n;
77 #else
78 	ssize_t n;
79 #endif
80 
81 	n = recv(fd, signals, sizeof(signals), 0);
82 	if (n == -1)
83 		event_err(1, "%s: read", __func__);
84 }
85 
86 #ifdef HAVE_SETFD
87 #define FD_CLOSEONEXEC(x) do { \
88         if (fcntl(x, F_SETFD, FD_CLOEXEC) == -1) \
89                 event_warn("fcntl(%d, F_SETFD)", x); \
90 } while (0)
91 #else
92 #define FD_CLOSEONEXEC(x)
93 #endif
94 
95 int
96 evsignal_init(struct event_base *base)
97 {
98 	int i;
99 
100 	/*
101 	 * Our signal handler is going to write to one end of the socket
102 	 * pair to wake up our event loop.  The event loop then scans for
103 	 * signals that got delivered.
104 	 */
105 	if (evutil_socketpair(
106 		    AF_UNIX, SOCK_STREAM, 0, base->sig.ev_signal_pair) == -1) {
107 #ifdef WIN32
108 		/* Make this nonfatal on win32, where sometimes people
109 		   have localhost firewalled. */
110 		event_warn("%s: socketpair", __func__);
111 #else
112 		event_err(1, "%s: socketpair", __func__);
113 #endif
114 		return -1;
115 	}
116 
117 	FD_CLOSEONEXEC(base->sig.ev_signal_pair[0]);
118 	FD_CLOSEONEXEC(base->sig.ev_signal_pair[1]);
119 	base->sig.sh_old = NULL;
120 	base->sig.sh_old_max = 0;
121 	base->sig.evsignal_caught = 0;
122 	memset(&base->sig.evsigcaught, 0, sizeof(sig_atomic_t)*NSIG);
123 	/* initialize the queues for all events */
124 	for (i = 0; i < NSIG; ++i)
125 		TAILQ_INIT(&base->sig.evsigevents[i]);
126 
127         evutil_make_socket_nonblocking(base->sig.ev_signal_pair[0]);
128 
129 	event_set(&base->sig.ev_signal, base->sig.ev_signal_pair[1],
130 		EV_READ | EV_PERSIST, evsignal_cb, &base->sig.ev_signal);
131 	base->sig.ev_signal.ev_base = base;
132 	base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
133 
134 	return 0;
135 }
136 
137 /* Helper: set the signal handler for evsignal to handler in base, so that
138  * we can restore the original handler when we clear the current one. */
139 int
140 _evsignal_set_handler(struct event_base *base,
141 		      int evsignal, void (*handler)(int))
142 {
143 #ifdef HAVE_SIGACTION
144 	struct sigaction sa;
145 #else
146 	ev_sighandler_t sh;
147 #endif
148 	struct evsignal_info *sig = &base->sig;
149 	void *p;
150 
151 	/*
152 	 * resize saved signal handler array up to the highest signal number.
153 	 * a dynamic array is used to keep footprint on the low side.
154 	 */
155 	if (evsignal >= sig->sh_old_max) {
156 		int new_max = evsignal + 1;
157 		event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",
158 			    __func__, evsignal, sig->sh_old_max));
159 		p = realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));
160 		if (p == NULL) {
161 			event_warn("realloc");
162 			return (-1);
163 		}
164 
165 		memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),
166 		    0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));
167 
168 		sig->sh_old_max = new_max;
169 		sig->sh_old = p;
170 	}
171 
172 	/* allocate space for previous handler out of dynamic array */
173 	sig->sh_old[evsignal] = malloc(sizeof *sig->sh_old[evsignal]);
174 	if (sig->sh_old[evsignal] == NULL) {
175 		event_warn("malloc");
176 		return (-1);
177 	}
178 
179 	/* save previous handler and setup new handler */
180 #ifdef HAVE_SIGACTION
181 	memset(&sa, 0, sizeof(sa));
182 	sa.sa_handler = handler;
183 	sa.sa_flags |= SA_RESTART;
184 	sigfillset(&sa.sa_mask);
185 
186 	if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {
187 		event_warn("sigaction");
188 		free(sig->sh_old[evsignal]);
189 		sig->sh_old[evsignal] = NULL;
190 		return (-1);
191 	}
192 #else
193 	if ((sh = signal(evsignal, handler)) == SIG_ERR) {
194 		event_warn("signal");
195 		free(sig->sh_old[evsignal]);
196 		sig->sh_old[evsignal] = NULL;
197 		return (-1);
198 	}
199 	*sig->sh_old[evsignal] = sh;
200 #endif
201 
202 	return (0);
203 }
204 
205 int
206 evsignal_add(struct event *ev)
207 {
208 	int evsignal;
209 	struct event_base *base = ev->ev_base;
210 	struct evsignal_info *sig = &ev->ev_base->sig;
211 
212 	if (ev->ev_events & (EV_READ|EV_WRITE))
213 		event_errx(1, "%s: EV_SIGNAL incompatible use", __func__);
214 	evsignal = EVENT_SIGNAL(ev);
215 	assert(evsignal >= 0 && evsignal < NSIG);
216 	if (TAILQ_EMPTY(&sig->evsigevents[evsignal])) {
217 		event_debug(("%s: %p: changing signal handler", __func__, ev));
218 		if (_evsignal_set_handler(
219 			    base, evsignal, evsignal_handler) == -1)
220 			return (-1);
221 
222 		/* catch signals if they happen quickly */
223 		evsignal_base = base;
224 
225 		if (!sig->ev_signal_added) {
226 			if (event_add(&sig->ev_signal, NULL))
227 				return (-1);
228 			sig->ev_signal_added = 1;
229 		}
230 	}
231 
232 	/* multiple events may listen to the same signal */
233 	TAILQ_INSERT_TAIL(&sig->evsigevents[evsignal], ev, ev_signal_next);
234 
235 	return (0);
236 }
237 
238 int
239 _evsignal_restore_handler(struct event_base *base, int evsignal)
240 {
241 	int ret = 0;
242 	struct evsignal_info *sig = &base->sig;
243 #ifdef HAVE_SIGACTION
244 	struct sigaction *sh;
245 #else
246 	ev_sighandler_t *sh;
247 #endif
248 
249 	/* restore previous handler */
250 	sh = sig->sh_old[evsignal];
251 	sig->sh_old[evsignal] = NULL;
252 #ifdef HAVE_SIGACTION
253 	if (sigaction(evsignal, sh, NULL) == -1) {
254 		event_warn("sigaction");
255 		ret = -1;
256 	}
257 #else
258 	if (signal(evsignal, *sh) == SIG_ERR) {
259 		event_warn("signal");
260 		ret = -1;
261 	}
262 #endif
263 	free(sh);
264 
265 	return ret;
266 }
267 
268 int
269 evsignal_del(struct event *ev)
270 {
271 	struct event_base *base = ev->ev_base;
272 	struct evsignal_info *sig = &base->sig;
273 	int evsignal = EVENT_SIGNAL(ev);
274 
275 	assert(evsignal >= 0 && evsignal < NSIG);
276 
277 	/* multiple events may listen to the same signal */
278 	TAILQ_REMOVE(&sig->evsigevents[evsignal], ev, ev_signal_next);
279 
280 	if (!TAILQ_EMPTY(&sig->evsigevents[evsignal]))
281 		return (0);
282 
283 	event_debug(("%s: %p: restoring signal handler", __func__, ev));
284 
285 	return (_evsignal_restore_handler(ev->ev_base, EVENT_SIGNAL(ev)));
286 }
287 
288 static void
289 evsignal_handler(int sig)
290 {
291 	int save_errno = errno;
292 
293 	if (evsignal_base == NULL) {
294 		event_warn(
295 			"%s: received signal %d, but have no base configured",
296 			__func__, sig);
297 		return;
298 	}
299 
300 	evsignal_base->sig.evsigcaught[sig]++;
301 	evsignal_base->sig.evsignal_caught = 1;
302 
303 #ifndef HAVE_SIGACTION
304 	signal(sig, evsignal_handler);
305 #endif
306 
307 	/* Wake up our notification mechanism */
308 	send(evsignal_base->sig.ev_signal_pair[0], "a", 1, 0);
309 	errno = save_errno;
310 }
311 
312 void
313 evsignal_process(struct event_base *base)
314 {
315 	struct evsignal_info *sig = &base->sig;
316 	struct event *ev, *next_ev;
317 	sig_atomic_t ncalls;
318 	int i;
319 
320 	base->sig.evsignal_caught = 0;
321 	for (i = 1; i < NSIG; ++i) {
322 		ncalls = sig->evsigcaught[i];
323 		if (ncalls == 0)
324 			continue;
325 		sig->evsigcaught[i] -= ncalls;
326 
327 		for (ev = TAILQ_FIRST(&sig->evsigevents[i]);
328 		    ev != NULL; ev = next_ev) {
329 			next_ev = TAILQ_NEXT(ev, ev_signal_next);
330 			if (!(ev->ev_events & EV_PERSIST))
331 				event_del(ev);
332 			event_active(ev, EV_SIGNAL, ncalls);
333 		}
334 
335 	}
336 }
337 
338 void
339 evsignal_dealloc(struct event_base *base)
340 {
341 	int i = 0;
342 	if (base->sig.ev_signal_added) {
343 		event_del(&base->sig.ev_signal);
344 		base->sig.ev_signal_added = 0;
345 	}
346 	for (i = 0; i < NSIG; ++i) {
347 		if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
348 			_evsignal_restore_handler(base, i);
349 	}
350 
351 	if (base->sig.ev_signal_pair[0] != -1) {
352 		EVUTIL_CLOSESOCKET(base->sig.ev_signal_pair[0]);
353 		base->sig.ev_signal_pair[0] = -1;
354 	}
355 	if (base->sig.ev_signal_pair[1] != -1) {
356 		EVUTIL_CLOSESOCKET(base->sig.ev_signal_pair[1]);
357 		base->sig.ev_signal_pair[1] = -1;
358 	}
359 	base->sig.sh_old_max = 0;
360 
361 	/* per index frees are handled in evsignal_del() */
362 	if (base->sig.sh_old) {
363 		free(base->sig.sh_old);
364 		base->sig.sh_old = NULL;
365 	}
366 }
367