Line data Source code
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
120 0 : evsig_set_base_(struct event_base *base)
121 : {
122 0 : EVSIGBASE_LOCK();
123 0 : evsig_base = base;
124 0 : evsig_base_n_signals_added = base->sig.ev_n_signals_added;
125 0 : evsig_base_fd = base->sig.ev_signal_pair[1];
126 0 : EVSIGBASE_UNLOCK();
127 0 : }
128 :
129 : /* Callback for when the signal handler write a byte to our signaling socket */
130 : static void
131 0 : 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 0 : base = arg;
140 :
141 0 : memset(&ncaught, 0, sizeof(ncaught));
142 :
143 : while (1) {
144 : #ifdef _WIN32
145 : n = recv(fd, signals, sizeof(signals), 0);
146 : #else
147 0 : n = read(fd, signals, sizeof(signals));
148 : #endif
149 0 : if (n == -1) {
150 0 : int err = evutil_socket_geterror(fd);
151 0 : if (! EVUTIL_ERR_RW_RETRIABLE(err))
152 0 : event_sock_err(1, fd, "%s: recv", __func__);
153 0 : break;
154 0 : } else if (n == 0) {
155 : /* XXX warn? */
156 0 : break;
157 : }
158 0 : for (i = 0; i < n; ++i) {
159 0 : ev_uint8_t sig = signals[i];
160 0 : if (sig < NSIG)
161 0 : ncaught[sig]++;
162 : }
163 : }
164 :
165 0 : EVBASE_ACQUIRE_LOCK(base, th_base_lock);
166 0 : for (i = 0; i < NSIG; ++i) {
167 0 : if (ncaught[i])
168 0 : evmap_signal_active_(base, i, ncaught[i]);
169 : }
170 0 : EVBASE_RELEASE_LOCK(base, th_base_lock);
171 0 : }
172 :
173 : int
174 3 : 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 3 : 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 0 : event_sock_err(1, -1, "%s: socketpair", __func__);
188 : #endif
189 : return -1;
190 : }
191 :
192 3 : if (base->sig.sh_old) {
193 0 : mm_free(base->sig.sh_old);
194 : }
195 3 : base->sig.sh_old = NULL;
196 3 : base->sig.sh_old_max = 0;
197 :
198 3 : event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0],
199 : EV_READ | EV_PERSIST, evsig_cb, base);
200 :
201 3 : base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
202 3 : event_priority_set(&base->sig.ev_signal, 0);
203 :
204 3 : base->evsigsel = &evsigops;
205 :
206 3 : 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
212 0 : 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 0 : 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 0 : if (evsignal >= sig->sh_old_max) {
228 0 : int new_max = evsignal + 1;
229 0 : event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",
230 : __func__, evsignal, sig->sh_old_max));
231 0 : p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));
232 0 : if (p == NULL) {
233 0 : event_warn("realloc");
234 0 : return (-1);
235 : }
236 :
237 0 : memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),
238 0 : 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));
239 :
240 0 : sig->sh_old_max = new_max;
241 0 : sig->sh_old = p;
242 : }
243 :
244 : /* allocate space for previous handler out of dynamic array */
245 0 : sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]);
246 0 : if (sig->sh_old[evsignal] == NULL) {
247 0 : event_warn("malloc");
248 0 : return (-1);
249 : }
250 :
251 : /* save previous handler and setup new handler */
252 : #ifdef EVENT__HAVE_SIGACTION
253 0 : memset(&sa, 0, sizeof(sa));
254 0 : sa.sa_handler = handler;
255 0 : sa.sa_flags |= SA_RESTART;
256 0 : sigfillset(&sa.sa_mask);
257 :
258 0 : if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {
259 0 : event_warn("sigaction");
260 0 : mm_free(sig->sh_old[evsignal]);
261 0 : sig->sh_old[evsignal] = NULL;
262 0 : 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 0 : return (0);
275 : }
276 :
277 : static int
278 0 : evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
279 : {
280 0 : struct evsig_info *sig = &base->sig;
281 : (void)p;
282 :
283 0 : EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
284 :
285 : /* catch signals if they happen quickly */
286 0 : EVSIGBASE_LOCK();
287 0 : if (evsig_base != base && evsig_base_n_signals_added) {
288 0 : 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 0 : base, evsig_base, base->evsel->name);
295 : }
296 0 : evsig_base = base;
297 0 : evsig_base_n_signals_added = ++sig->ev_n_signals_added;
298 0 : evsig_base_fd = base->sig.ev_signal_pair[1];
299 0 : EVSIGBASE_UNLOCK();
300 :
301 0 : event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal));
302 0 : if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) {
303 0 : goto err;
304 : }
305 :
306 :
307 0 : if (!sig->ev_signal_added) {
308 0 : if (event_add_nolock_(&sig->ev_signal, NULL, 0))
309 0 : goto err;
310 0 : sig->ev_signal_added = 1;
311 : }
312 :
313 0 : return (0);
314 :
315 : err:
316 0 : EVSIGBASE_LOCK();
317 0 : --evsig_base_n_signals_added;
318 0 : --sig->ev_n_signals_added;
319 0 : EVSIGBASE_UNLOCK();
320 0 : return (-1);
321 : }
322 :
323 : int
324 0 : evsig_restore_handler_(struct event_base *base, int evsignal)
325 : {
326 0 : int ret = 0;
327 0 : 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 0 : if (evsignal >= sig->sh_old_max) {
335 : /* Can't actually restore. */
336 : /* XXXX.*/
337 0 : return 0;
338 : }
339 :
340 : /* restore previous handler */
341 0 : sh = sig->sh_old[evsignal];
342 0 : sig->sh_old[evsignal] = NULL;
343 : #ifdef EVENT__HAVE_SIGACTION
344 0 : if (sigaction(evsignal, sh, NULL) == -1) {
345 0 : event_warn("sigaction");
346 0 : ret = -1;
347 : }
348 : #else
349 : if (signal(evsignal, *sh) == SIG_ERR) {
350 : event_warn("signal");
351 : ret = -1;
352 : }
353 : #endif
354 :
355 0 : mm_free(sh);
356 :
357 0 : return ret;
358 : }
359 :
360 : static int
361 0 : evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
362 : {
363 0 : EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
364 :
365 0 : event_debug(("%s: "EV_SOCK_FMT": restoring signal handler",
366 : __func__, EV_SOCK_ARG(evsignal)));
367 :
368 0 : EVSIGBASE_LOCK();
369 0 : --evsig_base_n_signals_added;
370 0 : --base->sig.ev_n_signals_added;
371 0 : EVSIGBASE_UNLOCK();
372 :
373 0 : return (evsig_restore_handler_(base, (int)evsignal));
374 : }
375 :
376 : static void __cdecl
377 0 : evsig_handler(int sig)
378 : {
379 0 : int save_errno = errno;
380 : #ifdef _WIN32
381 : int socket_errno = EVUTIL_SOCKET_ERROR();
382 : #endif
383 : ev_uint8_t msg;
384 :
385 0 : if (evsig_base == NULL) {
386 0 : event_warnx(
387 : "%s: received signal %d, but have no base configured",
388 : __func__, sig);
389 0 : return;
390 : }
391 :
392 : #ifndef EVENT__HAVE_SIGACTION
393 : signal(sig, evsig_handler);
394 : #endif
395 :
396 : /* Wake up our notification mechanism */
397 0 : msg = sig;
398 : #ifdef _WIN32
399 : send(evsig_base_fd, (char*)&msg, 1, 0);
400 : #else
401 : {
402 0 : int r = write(evsig_base_fd, (char*)&msg, 1);
403 : (void)r; /* Suppress 'unused return value' and 'unused var' */
404 : }
405 : #endif
406 0 : errno = save_errno;
407 : #ifdef _WIN32
408 : EVUTIL_SET_SOCKET_ERROR(socket_errno);
409 : #endif
410 : }
411 :
412 : void
413 0 : evsig_dealloc_(struct event_base *base)
414 : {
415 0 : int i = 0;
416 0 : if (base->sig.ev_signal_added) {
417 0 : event_del(&base->sig.ev_signal);
418 0 : 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 0 : event_debug_unassign(&base->sig.ev_signal);
423 :
424 0 : for (i = 0; i < NSIG; ++i) {
425 0 : if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
426 0 : evsig_restore_handler_(base, i);
427 : }
428 0 : EVSIGBASE_LOCK();
429 0 : if (base == evsig_base) {
430 0 : evsig_base = NULL;
431 0 : evsig_base_n_signals_added = 0;
432 0 : evsig_base_fd = -1;
433 : }
434 0 : EVSIGBASE_UNLOCK();
435 :
436 0 : if (base->sig.ev_signal_pair[0] != -1) {
437 0 : evutil_closesocket(base->sig.ev_signal_pair[0]);
438 0 : base->sig.ev_signal_pair[0] = -1;
439 : }
440 0 : if (base->sig.ev_signal_pair[1] != -1) {
441 0 : evutil_closesocket(base->sig.ev_signal_pair[1]);
442 0 : base->sig.ev_signal_pair[1] = -1;
443 : }
444 0 : base->sig.sh_old_max = 0;
445 :
446 : /* per index frees are handled in evsig_del() */
447 0 : if (base->sig.sh_old) {
448 0 : mm_free(base->sig.sh_old);
449 0 : base->sig.sh_old = NULL;
450 : }
451 0 : }
452 :
453 : static void
454 0 : evsig_free_globals_locks(void)
455 : {
456 : #ifndef EVENT__DISABLE_THREAD_SUPPORT
457 0 : if (evsig_base_lock != NULL) {
458 0 : EVTHREAD_FREE_LOCK(evsig_base_lock, 0);
459 0 : evsig_base_lock = NULL;
460 : }
461 : #endif
462 0 : return;
463 : }
464 :
465 : void
466 0 : evsig_free_globals_(void)
467 : {
468 0 : evsig_free_globals_locks();
469 0 : }
470 :
471 : #ifndef EVENT__DISABLE_THREAD_SUPPORT
472 : int
473 0 : evsig_global_setup_locks_(const int enable_locks)
474 : {
475 0 : EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);
476 0 : return 0;
477 : }
478 :
479 : #endif
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