1/*	$NetBSD: signal.c,v 1.1.1.4 2021/04/07 02:43:13 christos Exp $	*/
2/*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
3
4/*
5 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
6 * Copyright 2007-2012 Niels Provos and Nick Mathewson
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 *    derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30#include "event2/event-config.h"
31#include <sys/cdefs.h>
32__RCSID("$NetBSD: signal.c,v 1.1.1.4 2021/04/07 02:43:13 christos Exp $");
33#include "evconfig-private.h"
34
35#ifdef _WIN32
36#define WIN32_LEAN_AND_MEAN
37#include <winsock2.h>
38#include <windows.h>
39#undef WIN32_LEAN_AND_MEAN
40#endif
41#include <sys/types.h>
42#ifdef EVENT__HAVE_SYS_TIME_H
43#include <sys/time.h>
44#endif
45#include <sys/queue.h>
46#ifdef EVENT__HAVE_SYS_SOCKET_H
47#include <sys/socket.h>
48#endif
49#include <signal.h>
50#include <stdio.h>
51#include <stdlib.h>
52#include <string.h>
53#ifdef EVENT__HAVE_UNISTD_H
54#include <unistd.h>
55#endif
56#include <errno.h>
57#ifdef EVENT__HAVE_FCNTL_H
58#include <fcntl.h>
59#endif
60
61#include "event2/event.h"
62#include "event2/event_struct.h"
63#include "event-internal.h"
64#include "event2/util.h"
65#include "evsignal-internal.h"
66#include "log-internal.h"
67#include "evmap-internal.h"
68#include "evthread-internal.h"
69
70/*
71  signal.c
72
73  This is the signal-handling implementation we use for backends that don't
74  have a better way to do signal handling.  It uses sigaction() or signal()
75  to set a signal handler, and a socket pair to tell the event base when
76
77  Note that I said "the event base" : only one event base can be set up to use
78  this at a time.  For historical reasons and backward compatibility, if you
79  add an event for a signal to event_base A, then add an event for a signal
80  (any signal!) to event_base B, event_base B will get informed about the
81  signal, but event_base A won't.
82
83  It would be neat to change this behavior in some future version of Libevent.
84  kqueue already does something far more sensible.  We can make all backends
85  on Linux do a reasonable thing using signalfd.
86*/
87
88#ifndef _WIN32
89/* Windows wants us to call our signal handlers as __cdecl.  Nobody else
90 * expects you to do anything crazy like this. */
91#ifndef __cdecl
92#define __cdecl
93#endif
94#endif
95
96static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *);
97static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *);
98
99static const struct eventop evsigops = {
100	"signal",
101	NULL,
102	evsig_add,
103	evsig_del,
104	NULL,
105	NULL,
106	0, 0, 0
107};
108
109#ifndef EVENT__DISABLE_THREAD_SUPPORT
110/* Lock for evsig_base and evsig_base_n_signals_added fields. */
111static void *evsig_base_lock = NULL;
112#endif
113/* The event base that's currently getting informed about signals. */
114static struct event_base *evsig_base = NULL;
115/* A copy of evsig_base->sigev_n_signals_added. */
116static int evsig_base_n_signals_added = 0;
117static evutil_socket_t evsig_base_fd = -1;
118
119static void __cdecl evsig_handler(int sig);
120
121#define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0)
122#define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0)
123
124void
125evsig_set_base_(struct event_base *base)
126{
127	EVSIGBASE_LOCK();
128	evsig_base = base;
129	evsig_base_n_signals_added = base->sig.ev_n_signals_added;
130	evsig_base_fd = base->sig.ev_signal_pair[1];
131	EVSIGBASE_UNLOCK();
132}
133
134/* Callback for when the signal handler write a byte to our signaling socket */
135static void
136evsig_cb(evutil_socket_t fd, short what, void *arg)
137{
138	static char signals[1024];
139	ev_ssize_t n;
140	int i;
141	int ncaught[NSIG];
142	struct event_base *base;
143
144	base = arg;
145
146	memset(&ncaught, 0, sizeof(ncaught));
147
148	while (1) {
149#ifdef _WIN32
150		n = recv(fd, signals, sizeof(signals), 0);
151#else
152		n = read(fd, signals, sizeof(signals));
153#endif
154		if (n == -1) {
155			int err = evutil_socket_geterror(fd);
156			if (! EVUTIL_ERR_RW_RETRIABLE(err))
157				event_sock_err(1, fd, "%s: recv", __func__);
158			break;
159		} else if (n == 0) {
160			/* XXX warn? */
161			break;
162		}
163		for (i = 0; i < n; ++i) {
164			ev_uint8_t sig = signals[i];
165			if (sig < NSIG)
166				ncaught[sig]++;
167		}
168	}
169
170	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
171	for (i = 0; i < NSIG; ++i) {
172		if (ncaught[i])
173			evmap_signal_active_(base, i, ncaught[i]);
174	}
175	EVBASE_RELEASE_LOCK(base, th_base_lock);
176}
177
178int
179evsig_init_(struct event_base *base)
180{
181	/*
182	 * Our signal handler is going to write to one end of the socket
183	 * pair to wake up our event loop.  The event loop then scans for
184	 * signals that got delivered.
185	 */
186	if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) {
187#ifdef _WIN32
188		/* Make this nonfatal on win32, where sometimes people
189		   have localhost firewalled. */
190		event_sock_warn(-1, "%s: socketpair", __func__);
191#else
192		event_sock_err(1, -1, "%s: socketpair", __func__);
193#endif
194		return -1;
195	}
196
197	if (base->sig.sh_old) {
198		mm_free(base->sig.sh_old);
199	}
200	base->sig.sh_old = NULL;
201	base->sig.sh_old_max = 0;
202
203	event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0],
204		EV_READ | EV_PERSIST, evsig_cb, base);
205
206	base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
207	event_priority_set(&base->sig.ev_signal, 0);
208
209	base->evsigsel = &evsigops;
210
211	return 0;
212}
213
214/* Helper: set the signal handler for evsignal to handler in base, so that
215 * we can restore the original handler when we clear the current one. */
216int
217evsig_set_handler_(struct event_base *base,
218    int evsignal, void (__cdecl *handler)(int))
219{
220#ifdef EVENT__HAVE_SIGACTION
221	struct sigaction sa;
222#else
223	ev_sighandler_t sh;
224#endif
225	struct evsig_info *sig = &base->sig;
226	void *p;
227
228	/*
229	 * resize saved signal handler array up to the highest signal number.
230	 * a dynamic array is used to keep footprint on the low side.
231	 */
232	if (evsignal >= sig->sh_old_max) {
233		int new_max = evsignal + 1;
234		event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",
235			    __func__, evsignal, sig->sh_old_max));
236		p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));
237		if (p == NULL) {
238			event_warn("realloc");
239			return (-1);
240		}
241
242		memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),
243		    0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));
244
245		sig->sh_old_max = new_max;
246		sig->sh_old = p;
247	}
248
249	/* allocate space for previous handler out of dynamic array */
250	sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]);
251	if (sig->sh_old[evsignal] == NULL) {
252		event_warn("malloc");
253		return (-1);
254	}
255
256	/* save previous handler and setup new handler */
257#ifdef EVENT__HAVE_SIGACTION
258	memset(&sa, 0, sizeof(sa));
259	sa.sa_handler = handler;
260	sa.sa_flags |= SA_RESTART;
261	sigfillset(&sa.sa_mask);
262
263	if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {
264		event_warn("sigaction");
265		mm_free(sig->sh_old[evsignal]);
266		sig->sh_old[evsignal] = NULL;
267		return (-1);
268	}
269#else
270	if ((sh = signal(evsignal, handler)) == SIG_ERR) {
271		event_warn("signal");
272		mm_free(sig->sh_old[evsignal]);
273		sig->sh_old[evsignal] = NULL;
274		return (-1);
275	}
276	*sig->sh_old[evsignal] = sh;
277#endif
278
279	return (0);
280}
281
282static int
283evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
284{
285	struct evsig_info *sig = &base->sig;
286	(void)p;
287
288	EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
289
290	/* catch signals if they happen quickly */
291	EVSIGBASE_LOCK();
292	if (evsig_base != base && evsig_base_n_signals_added) {
293		event_warnx("Added a signal to event base %p with signals "
294		    "already added to event_base %p.  Only one can have "
295		    "signals at a time with the %s backend.  The base with "
296		    "the most recently added signal or the most recent "
297		    "event_base_loop() call gets preference; do "
298		    "not rely on this behavior in future Libevent versions.",
299		    base, evsig_base, base->evsel->name);
300	}
301	evsig_base = base;
302	evsig_base_n_signals_added = ++sig->ev_n_signals_added;
303	evsig_base_fd = base->sig.ev_signal_pair[1];
304	EVSIGBASE_UNLOCK();
305
306	event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal));
307	if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) {
308		goto err;
309	}
310
311
312	if (!sig->ev_signal_added) {
313		if (event_add_nolock_(&sig->ev_signal, NULL, 0))
314			goto err;
315		sig->ev_signal_added = 1;
316	}
317
318	return (0);
319
320err:
321	EVSIGBASE_LOCK();
322	--evsig_base_n_signals_added;
323	--sig->ev_n_signals_added;
324	EVSIGBASE_UNLOCK();
325	return (-1);
326}
327
328int
329evsig_restore_handler_(struct event_base *base, int evsignal)
330{
331	int ret = 0;
332	struct evsig_info *sig = &base->sig;
333#ifdef EVENT__HAVE_SIGACTION
334	struct sigaction *sh;
335#else
336	ev_sighandler_t *sh;
337#endif
338
339	if (evsignal >= sig->sh_old_max) {
340		/* Can't actually restore. */
341		/* XXXX.*/
342		return 0;
343	}
344
345	/* restore previous handler */
346	sh = sig->sh_old[evsignal];
347	sig->sh_old[evsignal] = NULL;
348#ifdef EVENT__HAVE_SIGACTION
349	if (sigaction(evsignal, sh, NULL) == -1) {
350		event_warn("sigaction");
351		ret = -1;
352	}
353#else
354	if (signal(evsignal, *sh) == SIG_ERR) {
355		event_warn("signal");
356		ret = -1;
357	}
358#endif
359
360	mm_free(sh);
361
362	return ret;
363}
364
365static int
366evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)
367{
368	EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);
369
370	event_debug(("%s: "EV_SOCK_FMT": restoring signal handler",
371		__func__, EV_SOCK_ARG(evsignal)));
372
373	EVSIGBASE_LOCK();
374	--evsig_base_n_signals_added;
375	--base->sig.ev_n_signals_added;
376	EVSIGBASE_UNLOCK();
377
378	return (evsig_restore_handler_(base, (int)evsignal));
379}
380
381static void __cdecl
382evsig_handler(int sig)
383{
384	int save_errno = errno;
385#ifdef _WIN32
386	int socket_errno = EVUTIL_SOCKET_ERROR();
387#endif
388	ev_uint8_t msg;
389
390	if (evsig_base == NULL) {
391		event_warnx(
392			"%s: received signal %d, but have no base configured",
393			__func__, sig);
394		return;
395	}
396
397#ifndef EVENT__HAVE_SIGACTION
398	signal(sig, evsig_handler);
399#endif
400
401	/* Wake up our notification mechanism */
402	msg = sig;
403#ifdef _WIN32
404	send(evsig_base_fd, (char*)&msg, 1, 0);
405#else
406	{
407		int r = write(evsig_base_fd, (char*)&msg, 1);
408		(void)r; /* Suppress 'unused return value' and 'unused var' */
409	}
410#endif
411	errno = save_errno;
412#ifdef _WIN32
413	EVUTIL_SET_SOCKET_ERROR(socket_errno);
414#endif
415}
416
417void
418evsig_dealloc_(struct event_base *base)
419{
420	int i = 0;
421	if (base->sig.ev_signal_added) {
422		event_del(&base->sig.ev_signal);
423		base->sig.ev_signal_added = 0;
424	}
425	/* debug event is created in evsig_init_/event_assign even when
426	 * ev_signal_added == 0, so unassign is required */
427	event_debug_unassign(&base->sig.ev_signal);
428
429	for (i = 0; i < NSIG; ++i) {
430		if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)
431			evsig_restore_handler_(base, i);
432	}
433	EVSIGBASE_LOCK();
434	if (base == evsig_base) {
435		evsig_base = NULL;
436		evsig_base_n_signals_added = 0;
437		evsig_base_fd = -1;
438	}
439	EVSIGBASE_UNLOCK();
440
441	if (base->sig.ev_signal_pair[0] != -1) {
442		evutil_closesocket(base->sig.ev_signal_pair[0]);
443		base->sig.ev_signal_pair[0] = -1;
444	}
445	if (base->sig.ev_signal_pair[1] != -1) {
446		evutil_closesocket(base->sig.ev_signal_pair[1]);
447		base->sig.ev_signal_pair[1] = -1;
448	}
449	base->sig.sh_old_max = 0;
450
451	/* per index frees are handled in evsig_del() */
452	if (base->sig.sh_old) {
453		mm_free(base->sig.sh_old);
454		base->sig.sh_old = NULL;
455	}
456}
457
458static void
459evsig_free_globals_locks(void)
460{
461#ifndef EVENT__DISABLE_THREAD_SUPPORT
462	if (evsig_base_lock != NULL) {
463		EVTHREAD_FREE_LOCK(evsig_base_lock, 0);
464		evsig_base_lock = NULL;
465	}
466#endif
467	return;
468}
469
470void
471evsig_free_globals_(void)
472{
473	evsig_free_globals_locks();
474}
475
476#ifndef EVENT__DISABLE_THREAD_SUPPORT
477int
478evsig_global_setup_locks_(const int enable_locks)
479{
480	EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);
481	return 0;
482}
483
484#endif
485