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1 /*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
2 
3 /*
4  * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
5  * Copyright 2007-2012 Niels Provos and Nick Mathewson
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 #include "event2/event-config.h"
30 #include "evconfig-private.h"
31 
32 #ifdef _WIN32
33 #define WIN32_LEAN_AND_MEAN
34 #include <winsock2.h>
35 #include <windows.h>
36 #undef WIN32_LEAN_AND_MEAN
37 #endif
38 #include <sys/types.h>
39 #ifdef EVENT__HAVE_SYS_TIME_H
40 #include <sys/time.h>
41 #endif
42 #include <sys/queue.h>
43 #ifdef EVENT__HAVE_SYS_SOCKET_H
44 #include <sys/socket.h>
45 #endif
46 #include <signal.h>
47 #include <stdio.h>
48 #include <stdlib.h>
49 #include <string.h>
50 #ifdef EVENT__HAVE_UNISTD_H
51 #include <unistd.h>
52 #endif
53 #include <errno.h>
54 #ifdef EVENT__HAVE_FCNTL_H
55 #include <fcntl.h>
56 #endif
57 
58 #include "event2/event.h"
59 #include "event2/event_struct.h"
60 #include "event-internal.h"
61 #include "event2/util.h"
62 #include "evsignal-internal.h"
63 #include "log-internal.h"
64 #include "evmap-internal.h"
65 #include "evthread-internal.h"
66 
67 /*
68   signal.c
69 
70   This is the signal-handling implementation we use for backends that don't
71   have a better way to do signal handling.  It uses sigaction() or signal()
72   to set a signal handler, and a socket pair to tell the event base when
73 
74   Note that I said "the event base" : only one event base can be set up to use
75   this at a time.  For historical reasons and backward compatibility, if you
76   add an event for a signal to event_base A, then add an event for a signal
77   (any signal!) to event_base B, event_base B will get informed about the
78   signal, but event_base A won't.
79 
80   It would be neat to change this behavior in some future version of Libevent.
81   kqueue already does something far more sensible.  We can make all backends
82   on Linux do a reasonable thing using signalfd.
83 */
84 
85 #ifndef _WIN32
86 /* Windows wants us to call our signal handlers as __cdecl.  Nobody else
87  * expects you to do anything crazy like this. */
88 #define __cdecl
89 #endif
90 
91 static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *);
92 static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *);
93 
94 static const struct eventop evsigops = {
95 	"signal",
96 	NULL,
97 	evsig_add,
98 	evsig_del,
99 	NULL,
100 	NULL,
101 	0, 0, 0
102 };
103 
104 #ifndef EVENT__DISABLE_THREAD_SUPPORT
105 /* Lock for evsig_base and evsig_base_n_signals_added fields. */
106 static void *evsig_base_lock = NULL;
107 #endif
108 /* The event base that's currently getting informed about signals. */
109 static struct event_base *evsig_base = NULL;
110 /* A copy of evsig_base->sigev_n_signals_added. */
111 static int evsig_base_n_signals_added = 0;
112 static evutil_socket_t evsig_base_fd = -1;
113 
114 static void __cdecl evsig_handler(int sig);
115 
116 #define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0)
117 #define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0)
118 
119 void
evsig_set_base_(struct event_base * base)120 evsig_set_base_(struct event_base *base)
121 {
122 	EVSIGBASE_LOCK();
123 	evsig_base = base;
124 	evsig_base_n_signals_added = base->sig.ev_n_signals_added;
125 	evsig_base_fd = base->sig.ev_signal_pair[1];
126 	EVSIGBASE_UNLOCK();
127 }
128 
129 /* Callback for when the signal handler write a byte to our signaling socket */
130 static void
evsig_cb(evutil_socket_t fd,short what,void * arg)131 evsig_cb(evutil_socket_t fd, short what, void *arg)
132 {
133 	static char signals[1024];
134 	ev_ssize_t n;
135 	int i;
136 	int ncaught[NSIG];
137 	struct event_base *base;
138 
139 	base = arg;
140 
141 	memset(&ncaught, 0, sizeof(ncaught));
142 
143 	while (1) {
144 #ifdef _WIN32
145 		n = recv(fd, signals, sizeof(signals), 0);
146 #else
147 		n = read(fd, signals, sizeof(signals));
148 #endif
149 		if (n == -1) {
150 			int err = evutil_socket_geterror(fd);
151 			if (! EVUTIL_ERR_RW_RETRIABLE(err))
152 				event_sock_err(1, fd, "%s: recv", __func__);
153 			break;
154 		} else if (n == 0) {
155 			/* XXX warn? */
156 			break;
157 		}
158 		for (i = 0; i < n; ++i) {
159 			ev_uint8_t sig = signals[i];
160 			if (sig < NSIG)
161 				ncaught[sig]++;
162 		}
163 	}
164 
165 	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
166 	for (i = 0; i < NSIG; ++i) {
167 		if (ncaught[i])
168 			evmap_signal_active_(base, i, ncaught[i]);
169 	}
170 	EVBASE_RELEASE_LOCK(base, th_base_lock);
171 }
172 
173 int
evsig_init_(struct event_base * base)174 evsig_init_(struct event_base *base)
175 {
176 	/*
177 	 * Our signal handler is going to write to one end of the socket
178 	 * pair to wake up our event loop.  The event loop then scans for
179 	 * signals that got delivered.
180 	 */
181 	if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) {
182 #ifdef _WIN32
183 		/* Make this nonfatal on win32, where sometimes people
184 		   have localhost firewalled. */
185 		event_sock_warn(-1, "%s: socketpair", __func__);
186 #else
187 		event_sock_err(1, -1, "%s: socketpair", __func__);
188 #endif
189 		return -1;
190 	}
191 
192 	if (base->sig.sh_old) {
193 		mm_free(base->sig.sh_old);
194 	}
195 	base->sig.sh_old = NULL;
196 	base->sig.sh_old_max = 0;
197 
198 	event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0],
199 		EV_READ | EV_PERSIST, evsig_cb, base);
200 
201 	base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
202 	event_priority_set(&base->sig.ev_signal, 0);
203 
204 	base->evsigsel = &evsigops;
205 
206 	return 0;
207 }
208 
209 /* Helper: set the signal handler for evsignal to handler in base, so that
210  * we can restore the original handler when we clear the current one. */
211 int
evsig_set_handler_(struct event_base * base,int evsignal,void (__cdecl * handler)(int))212 evsig_set_handler_(struct event_base *base,
213     int evsignal, void (__cdecl *handler)(int))
214 {
215 #ifdef EVENT__HAVE_SIGACTION
216 	struct sigaction sa;
217 #else
218 	ev_sighandler_t sh;
219 #endif
220 	struct evsig_info *sig = &base->sig;
221 	void *p;
222 
223 	/*
224 	 * resize saved signal handler array up to the highest signal number.
225 	 * a dynamic array is used to keep footprint on the low side.
226 	 */
227 	if (evsignal >= sig->sh_old_max) {
228 		int new_max = evsignal + 1;
229 		event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",
230 			    __func__, evsignal, sig->sh_old_max));
231 		p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));
232 		if (p == NULL) {
233 			event_warn("realloc");
234 			return (-1);
235 		}
236 
237 		memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),
238 		    0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));
239 
240 		sig->sh_old_max = new_max;
241 		sig->sh_old = p;
242 	}
243 
244 	/* allocate space for previous handler out of dynamic array */
245 	sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]);
246 	if (sig->sh_old[evsignal] == NULL) {
247 		event_warn("malloc");
248 		return (-1);
249 	}
250 
251 	/* save previous handler and setup new handler */
252 #ifdef EVENT__HAVE_SIGACTION
253 	memset(&sa, 0, sizeof(sa));
254 	sa.sa_handler = handler;
255 	sa.sa_flags |= SA_RESTART;
256 	sigfillset(&sa.sa_mask);
257 
258 	if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {
259 		event_warn("sigaction");
260 		mm_free(sig->sh_old[evsignal]);
261 		sig->sh_old[evsignal] = NULL;
262 		return (-1);
263 	}
264 #else
265 	if ((sh = signal(evsignal, handler)) == SIG_ERR) {
266 		event_warn("signal");
267 		mm_free(sig->sh_old[evsignal]);
268 		sig->sh_old[evsignal] = NULL;
269 		return (-1);
270 	}
271 	*sig->sh_old[evsignal] = sh;
272 #endif
273 
274 	return (0);
275 }
276 
277 static int
evsig_add(struct event_base * base,evutil_socket_t evsignal,short old,short events,void * p)278 evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
279 {
280 	struct evsig_info *sig = &base->sig;
281 	(void)p;
282 
283 	EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
284 
285 	/* catch signals if they happen quickly */
286 	EVSIGBASE_LOCK();
287 	if (evsig_base != base && evsig_base_n_signals_added) {
288 		event_warnx("Added a signal to event base %p with signals "
289 		    "already added to event_base %p.  Only one can have "
290 		    "signals at a time with the %s backend.  The base with "
291 		    "the most recently added signal or the most recent "
292 		    "event_base_loop() call gets preference; do "
293 		    "not rely on this behavior in future Libevent versions.",
294 		    base, evsig_base, base->evsel->name);
295 	}
296 	evsig_base = base;
297 	evsig_base_n_signals_added = ++sig->ev_n_signals_added;
298 	evsig_base_fd = base->sig.ev_signal_pair[1];
299 	EVSIGBASE_UNLOCK();
300 
301 	event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal));
302 	if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) {
303 		goto err;
304 	}
305 
306 
307 	if (!sig->ev_signal_added) {
308 		if (event_add_nolock_(&sig->ev_signal, NULL, 0))
309 			goto err;
310 		sig->ev_signal_added = 1;
311 	}
312 
313 	return (0);
314 
315 err:
316 	EVSIGBASE_LOCK();
317 	--evsig_base_n_signals_added;
318 	--sig->ev_n_signals_added;
319 	EVSIGBASE_UNLOCK();
320 	return (-1);
321 }
322 
323 int
evsig_restore_handler_(struct event_base * base,int evsignal)324 evsig_restore_handler_(struct event_base *base, int evsignal)
325 {
326 	int ret = 0;
327 	struct evsig_info *sig = &base->sig;
328 #ifdef EVENT__HAVE_SIGACTION
329 	struct sigaction *sh;
330 #else
331 	ev_sighandler_t *sh;
332 #endif
333 
334 	if (evsignal >= sig->sh_old_max) {
335 		/* Can't actually restore. */
336 		/* XXXX.*/
337 		return 0;
338 	}
339 
340 	/* restore previous handler */
341 	sh = sig->sh_old[evsignal];
342 	sig->sh_old[evsignal] = NULL;
343 #ifdef EVENT__HAVE_SIGACTION
344 	if (sigaction(evsignal, sh, NULL) == -1) {
345 		event_warn("sigaction");
346 		ret = -1;
347 	}
348 #else
349 	if (signal(evsignal, *sh) == SIG_ERR) {
350 		event_warn("signal");
351 		ret = -1;
352 	}
353 #endif
354 
355 	mm_free(sh);
356 
357 	return ret;
358 }
359 
360 static int
evsig_del(struct event_base * base,evutil_socket_t evsignal,short old,short events,void * p)361 evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
362 {
363 	EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
364 
365 	event_debug(("%s: "EV_SOCK_FMT": restoring signal handler",
366 		__func__, EV_SOCK_ARG(evsignal)));
367 
368 	EVSIGBASE_LOCK();
369 	--evsig_base_n_signals_added;
370 	--base->sig.ev_n_signals_added;
371 	EVSIGBASE_UNLOCK();
372 
373 	return (evsig_restore_handler_(base, (int)evsignal));
374 }
375 
376 static void __cdecl
evsig_handler(int sig)377 evsig_handler(int sig)
378 {
379 	int save_errno = errno;
380 #ifdef _WIN32
381 	int socket_errno = EVUTIL_SOCKET_ERROR();
382 #endif
383 	ev_uint8_t msg;
384 
385 	if (evsig_base == NULL) {
386 		event_warnx(
387 			"%s: received signal %d, but have no base configured",
388 			__func__, sig);
389 		return;
390 	}
391 
392 #ifndef EVENT__HAVE_SIGACTION
393 	signal(sig, evsig_handler);
394 #endif
395 
396 	/* Wake up our notification mechanism */
397 	msg = sig;
398 #ifdef _WIN32
399 	send(evsig_base_fd, (char*)&msg, 1, 0);
400 #else
401 	{
402 		int r = write(evsig_base_fd, (char*)&msg, 1);
403 		(void)r; /* Suppress 'unused return value' and 'unused var' */
404 	}
405 #endif
406 	errno = save_errno;
407 #ifdef _WIN32
408 	EVUTIL_SET_SOCKET_ERROR(socket_errno);
409 #endif
410 }
411 
412 void
evsig_dealloc_(struct event_base * base)413 evsig_dealloc_(struct event_base *base)
414 {
415 	int i = 0;
416 	if (base->sig.ev_signal_added) {
417 		event_del(&base->sig.ev_signal);
418 		base->sig.ev_signal_added = 0;
419 	}
420 	/* debug event is created in evsig_init_/event_assign even when
421 	 * ev_signal_added == 0, so unassign is required */
422 	event_debug_unassign(&base->sig.ev_signal);
423 
424 	for (i = 0; i < NSIG; ++i) {
425 		if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
426 			evsig_restore_handler_(base, i);
427 	}
428 	EVSIGBASE_LOCK();
429 	if (base == evsig_base) {
430 		evsig_base = NULL;
431 		evsig_base_n_signals_added = 0;
432 		evsig_base_fd = -1;
433 	}
434 	EVSIGBASE_UNLOCK();
435 
436 	if (base->sig.ev_signal_pair[0] != -1) {
437 		evutil_closesocket(base->sig.ev_signal_pair[0]);
438 		base->sig.ev_signal_pair[0] = -1;
439 	}
440 	if (base->sig.ev_signal_pair[1] != -1) {
441 		evutil_closesocket(base->sig.ev_signal_pair[1]);
442 		base->sig.ev_signal_pair[1] = -1;
443 	}
444 	base->sig.sh_old_max = 0;
445 
446 	/* per index frees are handled in evsig_del() */
447 	if (base->sig.sh_old) {
448 		mm_free(base->sig.sh_old);
449 		base->sig.sh_old = NULL;
450 	}
451 }
452 
453 static void
evsig_free_globals_locks(void)454 evsig_free_globals_locks(void)
455 {
456 #ifndef EVENT__DISABLE_THREAD_SUPPORT
457 	if (evsig_base_lock != NULL) {
458 		EVTHREAD_FREE_LOCK(evsig_base_lock, 0);
459 		evsig_base_lock = NULL;
460 	}
461 #endif
462 	return;
463 }
464 
465 void
evsig_free_globals_(void)466 evsig_free_globals_(void)
467 {
468 	evsig_free_globals_locks();
469 }
470 
471 #ifndef EVENT__DISABLE_THREAD_SUPPORT
472 int
evsig_global_setup_locks_(const int enable_locks)473 evsig_global_setup_locks_(const int enable_locks)
474 {
475 	EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);
476 	return 0;
477 }
478 
479 #endif
480