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