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
91static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *);
92static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *);
93
94static 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. */
106static void *evsig_base_lock = NULL;
107#endif
108/* The event base that's currently getting informed about signals. */
109static struct event_base *evsig_base = NULL;
110/* A copy of evsig_base->sigev_n_signals_added. */
111static int evsig_base_n_signals_added = 0;
112static evutil_socket_t evsig_base_fd = -1;
113
114static 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
119void
120evsig_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 */
130static void
131evsig_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
173int
174evsig_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. */
211int
212evsig_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
277static int
278evsig_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
315err:
316	EVSIGBASE_LOCK();
317	--evsig_base_n_signals_added;
318	--sig->ev_n_signals_added;
319	EVSIGBASE_UNLOCK();
320	return (-1);
321}
322
323int
324evsig_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
360static int
361evsig_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
376static void __cdecl
377evsig_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
412void
413evsig_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
453static void
454evsig_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
465void
466evsig_free_globals_(void)
467{
468	evsig_free_globals_locks();
469}
470
471#ifndef EVENT__DISABLE_THREAD_SUPPORT
472int
473evsig_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