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