xref: /php-src/Zend/zend_signal.c (revision 8e62e2b8)
1 /*
2   +----------------------------------------------------------------------+
3   | Zend Signal Handling                                                 |
4   +----------------------------------------------------------------------+
5   | Copyright (c) The PHP Group                                          |
6   +----------------------------------------------------------------------+
7   | This source file is subject to version 3.01 of the PHP license,      |
8   | that is bundled with this package in the file LICENSE, and is        |
9   | available through the world-wide-web at the following url:           |
10   | https://www.php.net/license/3_01.txt                                 |
11   | If you did not receive a copy of the PHP license and are unable to   |
12   | obtain it through the world-wide-web, please send a note to          |
13   | license@php.net so we can mail you a copy immediately.               |
14   +----------------------------------------------------------------------+
15   | Authors: Lucas Nealan <lucas@php.net>                                |
16   |          Arnaud Le Blanc <lbarnaud@php.net>                          |
17   +----------------------------------------------------------------------+
18 
19    This software was contributed to PHP by Facebook Inc. in 2008.
20 
21    Future revisions and derivatives of this source code must acknowledge
22    Facebook Inc. as the original contributor of this module by leaving
23    this note intact in the source code.
24 
25    All other licensing and usage conditions are those of the PHP Group.
26 */
27 
28 #ifndef _GNU_SOURCE
29 # define _GNU_SOURCE
30 #endif
31 #include <string.h>
32 
33 #include "zend.h"
34 #include "zend_globals.h"
35 #include <signal.h>
36 
37 #ifdef HAVE_UNISTD_H
38 #include <unistd.h>
39 #endif
40 
41 #ifdef ZEND_SIGNALS
42 
43 #include "zend_signal.h"
44 
45 #ifdef ZTS
46 ZEND_API int zend_signal_globals_id;
47 ZEND_API size_t zend_signal_globals_offset;
48 #else
49 ZEND_API zend_signal_globals_t zend_signal_globals;
50 #endif /* not ZTS */
51 
52 #define SIGNAL_BEGIN_CRITICAL() \
53 	sigset_t oldmask; \
54 	zend_sigprocmask(SIG_BLOCK, &global_sigmask, &oldmask);
55 #define SIGNAL_END_CRITICAL() \
56 	zend_sigprocmask(SIG_SETMASK, &oldmask, NULL);
57 
58 #ifdef ZTS
59 # define zend_sigprocmask(signo, set, oldset) tsrm_sigmask((signo), (set), (oldset))
60 #else
61 # define zend_sigprocmask(signo, set, oldset) sigprocmask((signo), (set), (oldset))
62 #endif
63 
64 static void zend_signal_handler(int signo, siginfo_t *siginfo, void *context);
65 static zend_result zend_signal_register(int signo, void (*handler)(int, siginfo_t*, void*));
66 
67 #if defined(__CYGWIN__) || defined(__PASE__)
68 /* Matches zend_execute_API.c; these platforms don't support ITIMER_PROF. */
69 #define TIMEOUT_SIG SIGALRM
70 #else
71 #define TIMEOUT_SIG SIGPROF
72 #endif
73 
74 static const int zend_sigs[] = { TIMEOUT_SIG, SIGHUP, SIGINT, SIGQUIT, SIGTERM, SIGUSR1, SIGUSR2 };
75 
76 #define SA_FLAGS_MASK ~(SA_NODEFER | SA_RESETHAND)
77 
78 /* True globals, written only at process startup */
79 static zend_signal_entry_t global_orig_handlers[NSIG];
80 static sigset_t            global_sigmask;
81 
82 /* {{{ zend_signal_handler_defer
83  *  Blocks signals if in critical section */
zend_signal_handler_defer(int signo,siginfo_t * siginfo,void * context)84 static void zend_signal_handler_defer(int signo, siginfo_t *siginfo, void *context)
85 {
86 	int errno_save = errno;
87 	zend_signal_queue_t *queue, *qtmp;
88 
89 #ifdef ZTS
90 	/* A signal could hit after TSRM shutdown, in this case globals are already freed.
91 	 * Or it could be delivered to a thread that didn't execute PHP yet.
92 	 * In the latter case we act as if SIGG(active) is false. */
93 	if (tsrm_is_shutdown() || !tsrm_is_managed_thread()) {
94 		/* Forward to default handler handler */
95 		zend_signal_handler(signo, siginfo, context);
96 		return;
97 	}
98 #endif
99 
100 	if (EXPECTED(SIGG(active))) {
101 		if (UNEXPECTED(SIGG(depth) == 0)) { /* try to handle signal */
102 			if (UNEXPECTED(SIGG(blocked))) {
103 				SIGG(blocked) = 0;
104 			}
105 			if (EXPECTED(SIGG(running) == 0)) {
106 				SIGG(running) = 1;
107 				zend_signal_handler(signo, siginfo, context);
108 
109 				queue = SIGG(phead);
110 				SIGG(phead) = NULL;
111 
112 				while (queue) {
113 					zend_signal_handler(queue->zend_signal.signo, queue->zend_signal.siginfo, queue->zend_signal.context);
114 					qtmp = queue->next;
115 					queue->next = SIGG(pavail);
116 					queue->zend_signal.signo = 0;
117 					SIGG(pavail) = queue;
118 					queue = qtmp;
119 				}
120 				SIGG(running) = 0;
121 			}
122 		} else { /* delay signal handling */
123 			SIGG(blocked) = 1; /* signal is blocked */
124 
125 			if ((queue = SIGG(pavail))) { /* if none available it's simply forgotten */
126 				SIGG(pavail) = queue->next;
127 				queue->zend_signal.signo = signo;
128 				queue->zend_signal.siginfo = siginfo;
129 				queue->zend_signal.context = context;
130 				queue->next = NULL;
131 
132 				if (SIGG(phead) && SIGG(ptail)) {
133 					SIGG(ptail)->next = queue;
134 				} else {
135 					SIGG(phead) = queue;
136 				}
137 				SIGG(ptail) = queue;
138 			}
139 #if ZEND_DEBUG
140 			else { /* this may not be safe to do, but could work and be useful */
141 				zend_output_debug_string(0, "zend_signal: not enough queue storage, lost signal (%d)", signo);
142 			}
143 #endif
144 		}
145 	} else {
146 		/* need to just run handler if we're inactive and getting a signal */
147 		zend_signal_handler(signo, siginfo, context);
148 	}
149 
150 	errno = errno_save;
151 } /* }}} */
152 
153 /* {{{ zend_signal_handler_unblock
154  * Handle deferred signal from HANDLE_UNBLOCK_ALARMS */
zend_signal_handler_unblock(void)155 ZEND_API void zend_signal_handler_unblock(void)
156 {
157 	zend_signal_queue_t *queue;
158 	zend_signal_t zend_signal;
159 
160 	if (EXPECTED(SIGG(active))) {
161 		SIGNAL_BEGIN_CRITICAL(); /* procmask to protect handler_defer as if it were called by the kernel */
162 		queue = SIGG(phead);
163 		SIGG(phead) = queue->next;
164 		zend_signal = queue->zend_signal;
165 		queue->next = SIGG(pavail);
166 		queue->zend_signal.signo = 0;
167 		SIGG(pavail) = queue;
168 
169 		zend_signal_handler_defer(zend_signal.signo, zend_signal.siginfo, zend_signal.context);
170 		SIGNAL_END_CRITICAL();
171 	}
172 }
173 /* }}} */
174 
175 /* {{{ zend_signal_handler
176  *  Call the previously registered handler for a signal
177  */
zend_signal_handler(int signo,siginfo_t * siginfo,void * context)178 static void zend_signal_handler(int signo, siginfo_t *siginfo, void *context)
179 {
180 	int errno_save = errno;
181 	struct sigaction sa;
182 	sigset_t sigset;
183 	zend_signal_entry_t p_sig;
184 #ifdef ZTS
185 	if (tsrm_is_shutdown() || !tsrm_is_managed_thread()) {
186 		p_sig = global_orig_handlers[signo-1];
187 	} else
188 #endif
189 	p_sig = SIGG(handlers)[signo-1];
190 
191 	if (p_sig.handler == SIG_DFL) { /* raise default handler */
192 		if (sigaction(signo, NULL, &sa) == 0) {
193 			sa.sa_handler = SIG_DFL;
194 			sigemptyset(&sa.sa_mask);
195 
196 			sigemptyset(&sigset);
197 			sigaddset(&sigset, signo);
198 
199 			if (sigaction(signo, &sa, NULL) == 0) {
200 				/* throw away any blocked signals */
201 				zend_sigprocmask(SIG_UNBLOCK, &sigset, NULL);
202 #ifdef ZTS
203 # define RAISE_ERROR "raise() failed\n"
204 				if (raise(signo) != 0) {
205 					/* On some systems raise() fails with errno 3: No such process */
206 					kill(getpid(), signo);
207 				}
208 #else
209 				kill(getpid(), signo);
210 #endif
211 			}
212 		}
213 	} else if (p_sig.handler != SIG_IGN) {
214 		if (p_sig.flags & SA_SIGINFO) {
215 			if (p_sig.flags & SA_RESETHAND) {
216 				SIGG(handlers)[signo-1].flags   = 0;
217 				SIGG(handlers)[signo-1].handler = SIG_DFL;
218 			}
219 			(*(void (*)(int, siginfo_t*, void*))p_sig.handler)(signo, siginfo, context);
220 		} else {
221 			(*(void (*)(int))p_sig.handler)(signo);
222 		}
223 	}
224 
225 	errno = errno_save;
226 } /* }}} */
227 
228 /* {{{ zend_sigaction
229  *  Register a signal handler that will be deferred in critical sections */
zend_sigaction(int signo,const struct sigaction * act,struct sigaction * oldact)230 ZEND_API void zend_sigaction(int signo, const struct sigaction *act, struct sigaction *oldact)
231 {
232 	struct sigaction sa;
233 	sigset_t sigset;
234 
235 	if (oldact != NULL) {
236 		oldact->sa_flags   = SIGG(handlers)[signo-1].flags;
237 		oldact->sa_handler = (void *) SIGG(handlers)[signo-1].handler;
238 		oldact->sa_mask    = global_sigmask;
239 	}
240 	if (act != NULL) {
241 		SIGG(handlers)[signo-1].flags = act->sa_flags;
242 		if (act->sa_flags & SA_SIGINFO) {
243 			SIGG(handlers)[signo-1].handler = (void *) act->sa_sigaction;
244 		} else {
245 			SIGG(handlers)[signo-1].handler = (void *) act->sa_handler;
246 		}
247 
248 		memset(&sa, 0, sizeof(sa));
249 		if (SIGG(handlers)[signo-1].handler == (void *) SIG_IGN) {
250 			sa.sa_sigaction = (void *) SIG_IGN;
251 		} else {
252 			sa.sa_flags     = SA_ONSTACK | SA_SIGINFO | (act->sa_flags & SA_FLAGS_MASK);
253 			sa.sa_sigaction = zend_signal_handler_defer;
254 			sa.sa_mask      = global_sigmask;
255 		}
256 
257 		if (sigaction(signo, &sa, NULL) < 0) {
258 			zend_error_noreturn(E_ERROR, "Error installing signal handler for %d", signo);
259 		}
260 
261 		/* unsure this signal is not blocked */
262 		sigemptyset(&sigset);
263 		sigaddset(&sigset, signo);
264 		zend_sigprocmask(SIG_UNBLOCK, &sigset, NULL);
265 	}
266 }
267 /* }}} */
268 
269 /* {{{ zend_signal
270  *  Register a signal handler that will be deferred in critical sections */
zend_signal(int signo,void (* handler)(int))271 ZEND_API void zend_signal(int signo, void (*handler)(int))
272 {
273 	struct sigaction sa;
274 
275 	memset(&sa, 0, sizeof(sa));
276 	sa.sa_flags   = 0;
277 	sa.sa_handler = handler;
278 	sa.sa_mask    = global_sigmask;
279 
280 	zend_sigaction(signo, &sa, NULL);
281 }
282 /* }}} */
283 
284 /* {{{ zend_signal_register
285  *  Set a handler for a signal we want to defer.
286  *  Previously set handler must have been saved before.
287  */
zend_signal_register(int signo,void (* handler)(int,siginfo_t *,void *))288 static zend_result zend_signal_register(int signo, void (*handler)(int, siginfo_t*, void*))
289 {
290 	struct sigaction sa;
291 
292 	if (sigaction(signo, NULL, &sa) == 0) {
293 		if ((sa.sa_flags & SA_SIGINFO) && sa.sa_sigaction == handler) {
294 			return FAILURE;
295 		}
296 
297 		SIGG(handlers)[signo-1].flags = sa.sa_flags;
298 		if (sa.sa_flags & SA_SIGINFO) {
299 			SIGG(handlers)[signo-1].handler = (void *)sa.sa_sigaction;
300 		} else {
301 			SIGG(handlers)[signo-1].handler = (void *)sa.sa_handler;
302 		}
303 
304 		sa.sa_flags     = SA_SIGINFO; /* we'll use a siginfo handler */
305 		sa.sa_sigaction = handler;
306 		sa.sa_mask      = global_sigmask;
307 
308 		if (sigaction(signo, &sa, NULL) < 0) {
309 			zend_error_noreturn(E_ERROR, "Error installing signal handler for %d", signo);
310 		}
311 
312 		return SUCCESS;
313 	}
314 	return FAILURE;
315 } /* }}} */
316 
317 /* {{{ zend_signal_activate
318  *  Install our signal handlers, per request */
zend_signal_activate(void)319 void zend_signal_activate(void)
320 {
321 	size_t x;
322 
323 	memcpy(&SIGG(handlers), &global_orig_handlers, sizeof(global_orig_handlers));
324 
325 	if (SIGG(reset)) {
326 		for (x = 0; x < sizeof(zend_sigs) / sizeof(*zend_sigs); x++) {
327 			zend_signal_register(zend_sigs[x], zend_signal_handler_defer);
328 		}
329 	}
330 
331 	SIGG(active) = 1;
332 	SIGG(depth)  = 0;
333 } /* }}} */
334 
335 /* {{{ zend_signal_deactivate */
zend_signal_deactivate(void)336 void zend_signal_deactivate(void)
337 {
338 	if (SIGG(check)) {
339 		size_t x;
340 		struct sigaction sa;
341 
342 		if (SIGG(depth) != 0) {
343 			zend_error(E_CORE_WARNING, "zend_signal: shutdown with non-zero blocking depth (%d)", SIGG(depth));
344 		}
345 
346 		/* did anyone steal our installed handler */
347 		for (x = 0; x < sizeof(zend_sigs) / sizeof(*zend_sigs); x++) {
348 			sigaction(zend_sigs[x], NULL, &sa);
349 			if (sa.sa_sigaction != zend_signal_handler_defer &&
350 					sa.sa_sigaction != (void *) SIG_IGN) {
351 				zend_error(E_CORE_WARNING, "zend_signal: handler was replaced for signal (%d) after startup", zend_sigs[x]);
352 			}
353 		}
354 	}
355 
356 	/* After active=0 is set, signal handlers will be called directly and other
357 	 * state that is reset below will not be accessed. */
358 	*((volatile int *) &SIGG(active)) = 0;
359 
360 	SIGG(running) = 0;
361 	SIGG(blocked) = 0;
362 	SIGG(depth) = 0;
363 
364 	/* If there are any queued signals because of a missed unblock, drop them. */
365 	if (SIGG(phead) && SIGG(ptail)) {
366 		SIGG(ptail)->next = SIGG(pavail);
367 		SIGG(pavail) = SIGG(phead);
368 		SIGG(phead) = NULL;
369 		SIGG(ptail) = NULL;
370 	}
371 }
372 /* }}} */
373 
zend_signal_globals_ctor(zend_signal_globals_t * zend_signal_globals)374 static void zend_signal_globals_ctor(zend_signal_globals_t *zend_signal_globals) /* {{{ */
375 {
376 	size_t x;
377 
378 	memset(zend_signal_globals, 0, sizeof(*zend_signal_globals));
379 	zend_signal_globals->reset = 1;
380 
381 	for (x = 0; x < sizeof(zend_signal_globals->pstorage) / sizeof(*zend_signal_globals->pstorage); ++x) {
382 		zend_signal_queue_t *queue = &zend_signal_globals->pstorage[x];
383 		queue->zend_signal.signo = 0;
384 		queue->next = zend_signal_globals->pavail;
385 		zend_signal_globals->pavail = queue;
386 	}
387 }
388 /* }}} */
389 
zend_signal_init(void)390 void zend_signal_init(void) /* {{{ */
391 {
392 	int signo;
393 	struct sigaction sa;
394 
395 	/* Save previously registered signal handlers into orig_handlers */
396 	memset(&global_orig_handlers, 0, sizeof(global_orig_handlers));
397 	for (signo = 1; signo < NSIG; ++signo) {
398 		if (sigaction(signo, NULL, &sa) == 0) {
399 			global_orig_handlers[signo-1].flags = sa.sa_flags;
400 			if (sa.sa_flags & SA_SIGINFO) {
401 				global_orig_handlers[signo-1].handler = (void *) sa.sa_sigaction;
402 			} else {
403 				global_orig_handlers[signo-1].handler = (void *) sa.sa_handler;
404 			}
405 		}
406 	}
407 }
408 /* }}} */
409 
410 /* {{{ zend_signal_startup
411  * alloc zend signal globals */
zend_signal_startup(void)412 ZEND_API void zend_signal_startup(void)
413 {
414 
415 #ifdef ZTS
416 	ts_allocate_fast_id(&zend_signal_globals_id, &zend_signal_globals_offset, sizeof(zend_signal_globals_t), (ts_allocate_ctor) zend_signal_globals_ctor, NULL);
417 #else
418 	zend_signal_globals_ctor(&zend_signal_globals);
419 #endif
420 
421 	/* Used to block signals during execution of signal handlers */
422 	sigfillset(&global_sigmask);
423 	sigdelset(&global_sigmask, SIGILL);
424 	sigdelset(&global_sigmask, SIGABRT);
425 	sigdelset(&global_sigmask, SIGFPE);
426 	sigdelset(&global_sigmask, SIGKILL);
427 	sigdelset(&global_sigmask, SIGSEGV);
428 	sigdelset(&global_sigmask, SIGCONT);
429 	sigdelset(&global_sigmask, SIGSTOP);
430 	sigdelset(&global_sigmask, SIGTSTP);
431 	sigdelset(&global_sigmask, SIGTTIN);
432 	sigdelset(&global_sigmask, SIGTTOU);
433 #ifdef SIGBUS
434 	sigdelset(&global_sigmask, SIGBUS);
435 #endif
436 #ifdef SIGSYS
437 	sigdelset(&global_sigmask, SIGSYS);
438 #endif
439 #ifdef SIGTRAP
440 	sigdelset(&global_sigmask, SIGTRAP);
441 #endif
442 
443 	zend_signal_init();
444 }
445 /* }}} */
446 
447 
448 #endif /* ZEND_SIGNALS */
449