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 #ifndef __cdecl
89 #define __cdecl
90 #endif
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[1];
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 #ifdef _WIN32
147 n = recv(fd, signals, sizeof(signals), 0);
148 #else
149 n = read(fd, signals, sizeof(signals));
150 #endif
151 if (n == -1) {
152 int err = evutil_socket_geterror(fd);
153 if (! EVUTIL_ERR_RW_RETRIABLE(err))
154 event_sock_err(1, fd, "%s: recv", __func__);
155 break;
156 } else if (n == 0) {
157 /* XXX warn? */
158 break;
159 }
160 for (i = 0; i < n; ++i) {
161 ev_uint8_t sig = signals[i];
162 if (sig < NSIG)
163 ncaught[sig]++;
164 }
165 }
166
167 EVBASE_ACQUIRE_LOCK(base, th_base_lock);
168 for (i = 0; i < NSIG; ++i) {
169 if (ncaught[i])
170 evmap_signal_active_(base, i, ncaught[i]);
171 }
172 EVBASE_RELEASE_LOCK(base, th_base_lock);
173 }
174
175 int
evsig_init_(struct event_base * base)176 evsig_init_(struct event_base *base)
177 {
178 /*
179 * Our signal handler is going to write to one end of the socket
180 * pair to wake up our event loop. The event loop then scans for
181 * signals that got delivered.
182 */
183 if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) {
184 #ifdef _WIN32
185 /* Make this nonfatal on win32, where sometimes people
186 have localhost firewalled. */
187 event_sock_warn(-1, "%s: socketpair", __func__);
188 #else
189 event_sock_err(1, -1, "%s: socketpair", __func__);
190 #endif
191 return -1;
192 }
193
194 if (base->sig.sh_old) {
195 mm_free(base->sig.sh_old);
196 }
197 base->sig.sh_old = NULL;
198 base->sig.sh_old_max = 0;
199
200 event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0],
201 EV_READ | EV_PERSIST, evsig_cb, base);
202
203 base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
204 event_priority_set(&base->sig.ev_signal, 0);
205
206 base->evsigsel = &evsigops;
207
208 return 0;
209 }
210
211 /* Helper: set the signal handler for evsignal to handler in base, so that
212 * we can restore the original handler when we clear the current one. */
213 int
evsig_set_handler_(struct event_base * base,int evsignal,void (__cdecl * handler)(int))214 evsig_set_handler_(struct event_base *base,
215 int evsignal, void (__cdecl *handler)(int))
216 {
217 #ifdef EVENT__HAVE_SIGACTION
218 struct sigaction sa;
219 #else
220 ev_sighandler_t sh;
221 #endif
222 struct evsig_info *sig = &base->sig;
223 void *p;
224
225 /*
226 * resize saved signal handler array up to the highest signal number.
227 * a dynamic array is used to keep footprint on the low side.
228 */
229 if (evsignal >= sig->sh_old_max) {
230 int new_max = evsignal + 1;
231 event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",
232 __func__, evsignal, sig->sh_old_max));
233 p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));
234 if (p == NULL) {
235 event_warn("realloc");
236 return (-1);
237 }
238
239 memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),
240 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));
241
242 sig->sh_old_max = new_max;
243 sig->sh_old = p;
244 }
245
246 /* allocate space for previous handler out of dynamic array */
247 sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]);
248 if (sig->sh_old[evsignal] == NULL) {
249 event_warn("malloc");
250 return (-1);
251 }
252
253 /* save previous handler and setup new handler */
254 #ifdef EVENT__HAVE_SIGACTION
255 memset(&sa, 0, sizeof(sa));
256 sa.sa_handler = handler;
257 sa.sa_flags |= SA_RESTART;
258 sigfillset(&sa.sa_mask);
259
260 if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {
261 event_warn("sigaction");
262 mm_free(sig->sh_old[evsignal]);
263 sig->sh_old[evsignal] = NULL;
264 return (-1);
265 }
266 #else
267 if ((sh = signal(evsignal, handler)) == SIG_ERR) {
268 event_warn("signal");
269 mm_free(sig->sh_old[evsignal]);
270 sig->sh_old[evsignal] = NULL;
271 return (-1);
272 }
273 *sig->sh_old[evsignal] = sh;
274 #endif
275
276 return (0);
277 }
278
279 static int
evsig_add(struct event_base * base,evutil_socket_t evsignal,short old,short events,void * p)280 evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
281 {
282 struct evsig_info *sig = &base->sig;
283 (void)p;
284
285 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
286
287 /* catch signals if they happen quickly */
288 EVSIGBASE_LOCK();
289 if (evsig_base != base && evsig_base_n_signals_added) {
290 event_warnx("Added a signal to event base %p with signals "
291 "already added to event_base %p. Only one can have "
292 "signals at a time with the %s backend. The base with "
293 "the most recently added signal or the most recent "
294 "event_base_loop() call gets preference; do "
295 "not rely on this behavior in future Libevent versions.",
296 base, evsig_base, base->evsel->name);
297 }
298 evsig_base = base;
299 evsig_base_n_signals_added = ++sig->ev_n_signals_added;
300 evsig_base_fd = base->sig.ev_signal_pair[1];
301 EVSIGBASE_UNLOCK();
302
303 event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal));
304 if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) {
305 goto err;
306 }
307
308
309 if (!sig->ev_signal_added) {
310 if (event_add_nolock_(&sig->ev_signal, NULL, 0))
311 goto err;
312 sig->ev_signal_added = 1;
313 }
314
315 return (0);
316
317 err:
318 EVSIGBASE_LOCK();
319 --evsig_base_n_signals_added;
320 --sig->ev_n_signals_added;
321 EVSIGBASE_UNLOCK();
322 return (-1);
323 }
324
325 int
evsig_restore_handler_(struct event_base * base,int evsignal)326 evsig_restore_handler_(struct event_base *base, int evsignal)
327 {
328 int ret = 0;
329 struct evsig_info *sig = &base->sig;
330 #ifdef EVENT__HAVE_SIGACTION
331 struct sigaction *sh;
332 #else
333 ev_sighandler_t *sh;
334 #endif
335
336 if (evsignal >= sig->sh_old_max) {
337 /* Can't actually restore. */
338 /* XXXX.*/
339 return 0;
340 }
341
342 /* restore previous handler */
343 sh = sig->sh_old[evsignal];
344 sig->sh_old[evsignal] = NULL;
345 #ifdef EVENT__HAVE_SIGACTION
346 if (sigaction(evsignal, sh, NULL) == -1) {
347 event_warn("sigaction");
348 ret = -1;
349 }
350 #else
351 if (signal(evsignal, *sh) == SIG_ERR) {
352 event_warn("signal");
353 ret = -1;
354 }
355 #endif
356
357 mm_free(sh);
358
359 return ret;
360 }
361
362 static int
evsig_del(struct event_base * base,evutil_socket_t evsignal,short old,short events,void * p)363 evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
364 {
365 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
366
367 event_debug(("%s: "EV_SOCK_FMT": restoring signal handler",
368 __func__, EV_SOCK_ARG(evsignal)));
369
370 EVSIGBASE_LOCK();
371 --evsig_base_n_signals_added;
372 --base->sig.ev_n_signals_added;
373 EVSIGBASE_UNLOCK();
374
375 return (evsig_restore_handler_(base, (int)evsignal));
376 }
377
378 static void __cdecl
evsig_handler(int sig)379 evsig_handler(int sig)
380 {
381 int save_errno = errno;
382 #ifdef _WIN32
383 int socket_errno = EVUTIL_SOCKET_ERROR();
384 #endif
385 ev_uint8_t msg;
386
387 if (evsig_base == NULL) {
388 event_warnx(
389 "%s: received signal %d, but have no base configured",
390 __func__, sig);
391 return;
392 }
393
394 #ifndef EVENT__HAVE_SIGACTION
395 signal(sig, evsig_handler);
396 #endif
397
398 /* Wake up our notification mechanism */
399 msg = sig;
400 #ifdef _WIN32
401 send(evsig_base_fd, (char*)&msg, 1, 0);
402 #else
403 {
404 int r = write(evsig_base_fd, (char*)&msg, 1);
405 (void)r; /* Suppress 'unused return value' and 'unused var' */
406 }
407 #endif
408 errno = save_errno;
409 #ifdef _WIN32
410 EVUTIL_SET_SOCKET_ERROR(socket_errno);
411 #endif
412 }
413
414 void
evsig_dealloc_(struct event_base * base)415 evsig_dealloc_(struct event_base *base)
416 {
417 int i = 0;
418 if (base->sig.ev_signal_added) {
419 event_del(&base->sig.ev_signal);
420 base->sig.ev_signal_added = 0;
421 }
422 /* debug event is created in evsig_init_/event_assign even when
423 * ev_signal_added == 0, so unassign is required */
424 event_debug_unassign(&base->sig.ev_signal);
425
426 for (i = 0; i < NSIG; ++i) {
427 if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
428 evsig_restore_handler_(base, i);
429 }
430 EVSIGBASE_LOCK();
431 if (base == evsig_base) {
432 evsig_base = NULL;
433 evsig_base_n_signals_added = 0;
434 evsig_base_fd = -1;
435 }
436 EVSIGBASE_UNLOCK();
437
438 if (base->sig.ev_signal_pair[0] != -1) {
439 evutil_closesocket(base->sig.ev_signal_pair[0]);
440 base->sig.ev_signal_pair[0] = -1;
441 }
442 if (base->sig.ev_signal_pair[1] != -1) {
443 evutil_closesocket(base->sig.ev_signal_pair[1]);
444 base->sig.ev_signal_pair[1] = -1;
445 }
446 base->sig.sh_old_max = 0;
447
448 /* per index frees are handled in evsig_del() */
449 if (base->sig.sh_old) {
450 mm_free(base->sig.sh_old);
451 base->sig.sh_old = NULL;
452 }
453 }
454
455 static void
evsig_free_globals_locks(void)456 evsig_free_globals_locks(void)
457 {
458 #ifndef EVENT__DISABLE_THREAD_SUPPORT
459 if (evsig_base_lock != NULL) {
460 EVTHREAD_FREE_LOCK(evsig_base_lock, 0);
461 evsig_base_lock = NULL;
462 }
463 #endif
464 return;
465 }
466
467 void
evsig_free_globals_(void)468 evsig_free_globals_(void)
469 {
470 evsig_free_globals_locks();
471 }
472
473 #ifndef EVENT__DISABLE_THREAD_SUPPORT
474 int
evsig_global_setup_locks_(const int enable_locks)475 evsig_global_setup_locks_(const int enable_locks)
476 {
477 EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);
478 return 0;
479 }
480
481 #endif
482