1 /* $NetBSD: signal.c,v 1.1.1.2 2013/04/11 16:43:25 christos Exp $ */
2 /* $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $ */
3
4 /*
5 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
6 * Copyright 2007-2012 Niels Provos and Nick Mathewson
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 * derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30 #include "event2/event-config.h"
31 #include <sys/cdefs.h>
32 __RCSID("$NetBSD: signal.c,v 1.1.1.2 2013/04/11 16:43:25 christos Exp $");
33
34 #ifdef WIN32
35 #define WIN32_LEAN_AND_MEAN
36 #include <winsock2.h>
37 #include <windows.h>
38 #undef WIN32_LEAN_AND_MEAN
39 #endif
40 #include <sys/types.h>
41 #ifdef _EVENT_HAVE_SYS_TIME_H
42 #include <sys/time.h>
43 #endif
44 #include <sys/queue.h>
45 #ifdef _EVENT_HAVE_SYS_SOCKET_H
46 #include <sys/socket.h>
47 #endif
48 #include <signal.h>
49 #include <stdio.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #ifdef _EVENT_HAVE_UNISTD_H
53 #include <unistd.h>
54 #endif
55 #include <errno.h>
56 #ifdef _EVENT_HAVE_FCNTL_H
57 #include <fcntl.h>
58 #endif
59
60 #include "event2/event.h"
61 #include "event2/event_struct.h"
62 #include "event-internal.h"
63 #include "event2/util.h"
64 #include "evsignal-internal.h"
65 #include "log-internal.h"
66 #include "evmap-internal.h"
67 #include "evthread-internal.h"
68
69 /*
70 signal.c
71
72 This is the signal-handling implementation we use for backends that don't
73 have a better way to do signal handling. It uses sigaction() or signal()
74 to set a signal handler, and a socket pair to tell the event base when
75
76 Note that I said "the event base" : only one event base can be set up to use
77 this at a time. For historical reasons and backward compatibility, if you
78 add an event for a signal to event_base A, then add an event for a signal
79 (any signal!) to event_base B, event_base B will get informed about the
80 signal, but event_base A won't.
81
82 It would be neat to change this behavior in some future version of Libevent.
83 kqueue already does something far more sensible. We can make all backends
84 on Linux do a reasonable thing using signalfd.
85 */
86
87 #ifndef WIN32
88 /* Windows wants us to call our signal handlers as __cdecl. Nobody else
89 * expects you to do anything crazy like this. */
90 #define __cdecl
91 #endif
92
93 static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *);
94 static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *);
95
96 static const struct eventop evsigops = {
97 "signal",
98 NULL,
99 evsig_add,
100 evsig_del,
101 NULL,
102 NULL,
103 0, 0, 0
104 };
105
106 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
107 /* Lock for evsig_base and evsig_base_n_signals_added fields. */
108 static void *evsig_base_lock = NULL;
109 #endif
110 /* The event base that's currently getting informed about signals. */
111 static struct event_base *evsig_base = NULL;
112 /* A copy of evsig_base->sigev_n_signals_added. */
113 static int evsig_base_n_signals_added = 0;
114 static evutil_socket_t evsig_base_fd = -1;
115
116 static void __cdecl evsig_handler(int sig);
117
118 #define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0)
119 #define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0)
120
121 void
evsig_set_base(struct event_base * base)122 evsig_set_base(struct event_base *base)
123 {
124 EVSIGBASE_LOCK();
125 evsig_base = base;
126 evsig_base_n_signals_added = base->sig.ev_n_signals_added;
127 evsig_base_fd = base->sig.ev_signal_pair[0];
128 EVSIGBASE_UNLOCK();
129 }
130
131 /* Callback for when the signal handler write a byte to our signaling socket */
132 static void
evsig_cb(evutil_socket_t fd,short what,void * arg)133 evsig_cb(evutil_socket_t fd, short what, void *arg)
134 {
135 static char signals[1024];
136 ev_ssize_t n;
137 int i;
138 int ncaught[NSIG];
139 struct event_base *base;
140
141 base = arg;
142
143 memset(&ncaught, 0, sizeof(ncaught));
144
145 while (1) {
146 n = recv(fd, signals, sizeof(signals), 0);
147 if (n == -1) {
148 int err = evutil_socket_geterror(fd);
149 if (! EVUTIL_ERR_RW_RETRIABLE(err))
150 event_sock_err(1, fd, "%s: recv", __func__);
151 break;
152 } else if (n == 0) {
153 /* XXX warn? */
154 break;
155 }
156 for (i = 0; i < n; ++i) {
157 ev_uint8_t sig = signals[i];
158 if (sig < NSIG)
159 ncaught[sig]++;
160 }
161 }
162
163 EVBASE_ACQUIRE_LOCK(base, th_base_lock);
164 for (i = 0; i < NSIG; ++i) {
165 if (ncaught[i])
166 evmap_signal_active(base, i, ncaught[i]);
167 }
168 EVBASE_RELEASE_LOCK(base, th_base_lock);
169 }
170
171 int
evsig_init(struct event_base * base)172 evsig_init(struct event_base *base)
173 {
174 /*
175 * Our signal handler is going to write to one end of the socket
176 * pair to wake up our event loop. The event loop then scans for
177 * signals that got delivered.
178 */
179 if (evutil_socketpair(
180 AF_UNIX, SOCK_STREAM, 0, base->sig.ev_signal_pair) == -1) {
181 #ifdef WIN32
182 /* Make this nonfatal on win32, where sometimes people
183 have localhost firewalled. */
184 event_sock_warn(-1, "%s: socketpair", __func__);
185 #else
186 event_sock_err(1, -1, "%s: socketpair", __func__);
187 #endif
188 return -1;
189 }
190
191 evutil_make_socket_closeonexec(base->sig.ev_signal_pair[0]);
192 evutil_make_socket_closeonexec(base->sig.ev_signal_pair[1]);
193 base->sig.sh_old = NULL;
194 base->sig.sh_old_max = 0;
195
196 evutil_make_socket_nonblocking(base->sig.ev_signal_pair[0]);
197 evutil_make_socket_nonblocking(base->sig.ev_signal_pair[1]);
198
199 event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[1],
200 EV_READ | EV_PERSIST, evsig_cb, base);
201
202 base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
203 event_priority_set(&base->sig.ev_signal, 0);
204
205 base->evsigsel = &evsigops;
206
207 return 0;
208 }
209
210 /* Helper: set the signal handler for evsignal to handler in base, so that
211 * we can restore the original handler when we clear the current one. */
212 int
_evsig_set_handler(struct event_base * base,int evsignal,void (__cdecl * handler)(int))213 _evsig_set_handler(struct event_base *base,
214 int evsignal, void (__cdecl *handler)(int))
215 {
216 #ifdef _EVENT_HAVE_SIGACTION
217 struct sigaction sa;
218 #else
219 ev_sighandler_t sh;
220 #endif
221 struct evsig_info *sig = &base->sig;
222 void *p;
223
224 /*
225 * resize saved signal handler array up to the highest signal number.
226 * a dynamic array is used to keep footprint on the low side.
227 */
228 if (evsignal >= sig->sh_old_max) {
229 int new_max = evsignal + 1;
230 event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",
231 __func__, evsignal, sig->sh_old_max));
232 p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));
233 if (p == NULL) {
234 event_warn("realloc");
235 return (-1);
236 }
237
238 memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),
239 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));
240
241 sig->sh_old_max = new_max;
242 sig->sh_old = p;
243 }
244
245 /* allocate space for previous handler out of dynamic array */
246 sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]);
247 if (sig->sh_old[evsignal] == NULL) {
248 event_warn("malloc");
249 return (-1);
250 }
251
252 /* save previous handler and setup new handler */
253 #ifdef _EVENT_HAVE_SIGACTION
254 memset(&sa, 0, sizeof(sa));
255 sa.sa_handler = handler;
256 sa.sa_flags |= SA_RESTART;
257 sigfillset(&sa.sa_mask);
258
259 if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {
260 event_warn("sigaction");
261 mm_free(sig->sh_old[evsignal]);
262 sig->sh_old[evsignal] = NULL;
263 return (-1);
264 }
265 #else
266 if ((sh = signal(evsignal, handler)) == SIG_ERR) {
267 event_warn("signal");
268 mm_free(sig->sh_old[evsignal]);
269 sig->sh_old[evsignal] = NULL;
270 return (-1);
271 }
272 *sig->sh_old[evsignal] = sh;
273 #endif
274
275 return (0);
276 }
277
278 static int
evsig_add(struct event_base * base,evutil_socket_t evsignal,short old,short events,void * p)279 evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
280 {
281 struct evsig_info *sig = &base->sig;
282 (void)p;
283
284 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
285
286 /* catch signals if they happen quickly */
287 EVSIGBASE_LOCK();
288 if (evsig_base != base && evsig_base_n_signals_added) {
289 event_warnx("Added a signal to event base %p with signals "
290 "already added to event_base %p. Only one can have "
291 "signals at a time with the %s backend. The base with "
292 "the most recently added signal or the most recent "
293 "event_base_loop() call gets preference; do "
294 "not rely on this behavior in future Libevent versions.",
295 base, evsig_base, base->evsel->name);
296 }
297 evsig_base = base;
298 evsig_base_n_signals_added = ++sig->ev_n_signals_added;
299 evsig_base_fd = base->sig.ev_signal_pair[0];
300 EVSIGBASE_UNLOCK();
301
302 event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal));
303 if (_evsig_set_handler(base, (int)evsignal, evsig_handler) == -1) {
304 goto err;
305 }
306
307
308 if (!sig->ev_signal_added) {
309 if (event_add(&sig->ev_signal, NULL))
310 goto err;
311 sig->ev_signal_added = 1;
312 }
313
314 return (0);
315
316 err:
317 EVSIGBASE_LOCK();
318 --evsig_base_n_signals_added;
319 --sig->ev_n_signals_added;
320 EVSIGBASE_UNLOCK();
321 return (-1);
322 }
323
324 int
_evsig_restore_handler(struct event_base * base,int evsignal)325 _evsig_restore_handler(struct event_base *base, int evsignal)
326 {
327 int ret = 0;
328 struct evsig_info *sig = &base->sig;
329 #ifdef _EVENT_HAVE_SIGACTION
330 struct sigaction *sh;
331 #else
332 ev_sighandler_t *sh;
333 #endif
334
335 /* restore previous handler */
336 sh = sig->sh_old[evsignal];
337 sig->sh_old[evsignal] = NULL;
338 #ifdef _EVENT_HAVE_SIGACTION
339 if (sigaction(evsignal, sh, NULL) == -1) {
340 event_warn("sigaction");
341 ret = -1;
342 }
343 #else
344 if (signal(evsignal, *sh) == SIG_ERR) {
345 event_warn("signal");
346 ret = -1;
347 }
348 #endif
349
350 mm_free(sh);
351
352 return ret;
353 }
354
355 static int
evsig_del(struct event_base * base,evutil_socket_t evsignal,short old,short events,void * p)356 evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
357 {
358 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
359
360 event_debug(("%s: "EV_SOCK_FMT": restoring signal handler",
361 __func__, EV_SOCK_ARG(evsignal)));
362
363 EVSIGBASE_LOCK();
364 --evsig_base_n_signals_added;
365 --base->sig.ev_n_signals_added;
366 EVSIGBASE_UNLOCK();
367
368 return (_evsig_restore_handler(base, (int)evsignal));
369 }
370
371 static void __cdecl
evsig_handler(int sig)372 evsig_handler(int sig)
373 {
374 int save_errno = errno;
375 #ifdef WIN32
376 int socket_errno = EVUTIL_SOCKET_ERROR();
377 #endif
378 ev_uint8_t msg;
379
380 if (evsig_base == NULL) {
381 event_warnx(
382 "%s: received signal %d, but have no base configured",
383 __func__, sig);
384 return;
385 }
386
387 #ifndef _EVENT_HAVE_SIGACTION
388 signal(sig, evsig_handler);
389 #endif
390
391 /* Wake up our notification mechanism */
392 msg = sig;
393 send(evsig_base_fd, (char*)&msg, 1, 0);
394 errno = save_errno;
395 #ifdef WIN32
396 EVUTIL_SET_SOCKET_ERROR(socket_errno);
397 #endif
398 }
399
400 void
evsig_dealloc(struct event_base * base)401 evsig_dealloc(struct event_base *base)
402 {
403 int i = 0;
404 if (base->sig.ev_signal_added) {
405 event_del(&base->sig.ev_signal);
406 base->sig.ev_signal_added = 0;
407 }
408 /* debug event is created in evsig_init/event_assign even when
409 * ev_signal_added == 0, so unassign is required */
410 event_debug_unassign(&base->sig.ev_signal);
411
412 for (i = 0; i < NSIG; ++i) {
413 if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
414 _evsig_restore_handler(base, i);
415 }
416 EVSIGBASE_LOCK();
417 if (base == evsig_base) {
418 evsig_base = NULL;
419 evsig_base_n_signals_added = 0;
420 evsig_base_fd = -1;
421 }
422 EVSIGBASE_UNLOCK();
423
424 if (base->sig.ev_signal_pair[0] != -1) {
425 evutil_closesocket(base->sig.ev_signal_pair[0]);
426 base->sig.ev_signal_pair[0] = -1;
427 }
428 if (base->sig.ev_signal_pair[1] != -1) {
429 evutil_closesocket(base->sig.ev_signal_pair[1]);
430 base->sig.ev_signal_pair[1] = -1;
431 }
432 base->sig.sh_old_max = 0;
433
434 /* per index frees are handled in evsig_del() */
435 if (base->sig.sh_old) {
436 mm_free(base->sig.sh_old);
437 base->sig.sh_old = NULL;
438 }
439 }
440
441 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
442 int
evsig_global_setup_locks_(const int enable_locks)443 evsig_global_setup_locks_(const int enable_locks)
444 {
445 EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);
446 return 0;
447 }
448 #endif
449