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1 /*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey 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
evsignal_cb(int fd,short what,void * arg)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, 1) == -1) \
89                 event_warn("fcntl(%d, F_SETFD)", x); \
90 } while (0)
91 #else
92 #define FD_CLOSEONEXEC(x)
93 #endif
94 
95 int
evsignal_init(struct event_base * base)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
_evsignal_set_handler(struct event_base * base,int evsignal,void (* handler)(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 		return (-1);
190 	}
191 #else
192 	if ((sh = signal(evsignal, handler)) == SIG_ERR) {
193 		event_warn("signal");
194 		free(sig->sh_old[evsignal]);
195 		return (-1);
196 	}
197 	*sig->sh_old[evsignal] = sh;
198 #endif
199 
200 	return (0);
201 }
202 
203 int
evsignal_add(struct event * ev)204 evsignal_add(struct event *ev)
205 {
206 	int evsignal;
207 	struct event_base *base = ev->ev_base;
208 	struct evsignal_info *sig = &ev->ev_base->sig;
209 
210 	if (ev->ev_events & (EV_READ|EV_WRITE))
211 		event_errx(1, "%s: EV_SIGNAL incompatible use", __func__);
212 	evsignal = EVENT_SIGNAL(ev);
213 	assert(evsignal >= 0 && evsignal < NSIG);
214 	if (TAILQ_EMPTY(&sig->evsigevents[evsignal])) {
215 		event_debug(("%s: %p: changing signal handler", __func__, ev));
216 		if (_evsignal_set_handler(
217 			    base, evsignal, evsignal_handler) == -1)
218 			return (-1);
219 
220 		/* catch signals if they happen quickly */
221 		evsignal_base = base;
222 
223 		if (!sig->ev_signal_added) {
224 			if (event_add(&sig->ev_signal, NULL))
225 				return (-1);
226 			sig->ev_signal_added = 1;
227 		}
228 	}
229 
230 	/* multiple events may listen to the same signal */
231 	TAILQ_INSERT_TAIL(&sig->evsigevents[evsignal], ev, ev_signal_next);
232 
233 	return (0);
234 }
235 
236 int
_evsignal_restore_handler(struct event_base * base,int evsignal)237 _evsignal_restore_handler(struct event_base *base, int evsignal)
238 {
239 	int ret = 0;
240 	struct evsignal_info *sig = &base->sig;
241 #ifdef HAVE_SIGACTION
242 	struct sigaction *sh;
243 #else
244 	ev_sighandler_t *sh;
245 #endif
246 
247 	/* restore previous handler */
248 	sh = sig->sh_old[evsignal];
249 	sig->sh_old[evsignal] = NULL;
250 #ifdef HAVE_SIGACTION
251 	if (sigaction(evsignal, sh, NULL) == -1) {
252 		event_warn("sigaction");
253 		ret = -1;
254 	}
255 #else
256 	if (signal(evsignal, *sh) == SIG_ERR) {
257 		event_warn("signal");
258 		ret = -1;
259 	}
260 #endif
261 	free(sh);
262 
263 	return ret;
264 }
265 
266 int
evsignal_del(struct event * ev)267 evsignal_del(struct event *ev)
268 {
269 	struct event_base *base = ev->ev_base;
270 	struct evsignal_info *sig = &base->sig;
271 	int evsignal = EVENT_SIGNAL(ev);
272 
273 	assert(evsignal >= 0 && evsignal < NSIG);
274 
275 	/* multiple events may listen to the same signal */
276 	TAILQ_REMOVE(&sig->evsigevents[evsignal], ev, ev_signal_next);
277 
278 	if (!TAILQ_EMPTY(&sig->evsigevents[evsignal]))
279 		return (0);
280 
281 	event_debug(("%s: %p: restoring signal handler", __func__, ev));
282 
283 	return (_evsignal_restore_handler(ev->ev_base, EVENT_SIGNAL(ev)));
284 }
285 
286 static void
evsignal_handler(int sig)287 evsignal_handler(int sig)
288 {
289 	int save_errno = errno;
290 
291 	if (evsignal_base == NULL) {
292 		event_warn(
293 			"%s: received signal %d, but have no base configured",
294 			__func__, sig);
295 		return;
296 	}
297 
298 	evsignal_base->sig.evsigcaught[sig]++;
299 	evsignal_base->sig.evsignal_caught = 1;
300 
301 #ifndef HAVE_SIGACTION
302 	signal(sig, evsignal_handler);
303 #endif
304 
305 	/* Wake up our notification mechanism */
306 	send(evsignal_base->sig.ev_signal_pair[0], "a", 1, 0);
307 	errno = save_errno;
308 }
309 
310 void
evsignal_process(struct event_base * base)311 evsignal_process(struct event_base *base)
312 {
313 	struct evsignal_info *sig = &base->sig;
314 	struct event *ev, *next_ev;
315 	sig_atomic_t ncalls;
316 	int i;
317 
318 	base->sig.evsignal_caught = 0;
319 	for (i = 1; i < NSIG; ++i) {
320 		ncalls = sig->evsigcaught[i];
321 		if (ncalls == 0)
322 			continue;
323 		sig->evsigcaught[i] -= ncalls;
324 
325 		for (ev = TAILQ_FIRST(&sig->evsigevents[i]);
326 		    ev != NULL; ev = next_ev) {
327 			next_ev = TAILQ_NEXT(ev, ev_signal_next);
328 			if (!(ev->ev_events & EV_PERSIST))
329 				event_del(ev);
330 			event_active(ev, EV_SIGNAL, ncalls);
331 		}
332 
333 	}
334 }
335 
336 void
evsignal_dealloc(struct event_base * base)337 evsignal_dealloc(struct event_base *base)
338 {
339 	int i = 0;
340 	if (base->sig.ev_signal_added) {
341 		event_del(&base->sig.ev_signal);
342 		base->sig.ev_signal_added = 0;
343 	}
344 	for (i = 0; i < NSIG; ++i) {
345 		if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
346 			_evsignal_restore_handler(base, i);
347 	}
348 
349 	EVUTIL_CLOSESOCKET(base->sig.ev_signal_pair[0]);
350 	base->sig.ev_signal_pair[0] = -1;
351 	EVUTIL_CLOSESOCKET(base->sig.ev_signal_pair[1]);
352 	base->sig.ev_signal_pair[1] = -1;
353 	base->sig.sh_old_max = 0;
354 
355 	/* per index frees are handled in evsignal_del() */
356 	free(base->sig.sh_old);
357 }
358