1 /* $NetBSD: signal.c,v 1.1.1.2 2013/04/11 16:43:25 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 1.1.1.2 2013/04/11 16:43:25 christos Exp $"); 33 34 #ifdef WIN32 35 #define WIN32_LEAN_AND_MEAN 36 #include <winsock2.h> 37 #include <windows.h> 38 #undef WIN32_LEAN_AND_MEAN 39 #endif 40 #include <sys/types.h> 41 #ifdef _EVENT_HAVE_SYS_TIME_H 42 #include <sys/time.h> 43 #endif 44 #include <sys/queue.h> 45 #ifdef _EVENT_HAVE_SYS_SOCKET_H 46 #include <sys/socket.h> 47 #endif 48 #include <signal.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include <string.h> 52 #ifdef _EVENT_HAVE_UNISTD_H 53 #include <unistd.h> 54 #endif 55 #include <errno.h> 56 #ifdef _EVENT_HAVE_FCNTL_H 57 #include <fcntl.h> 58 #endif 59 60 #include "event2/event.h" 61 #include "event2/event_struct.h" 62 #include "event-internal.h" 63 #include "event2/util.h" 64 #include "evsignal-internal.h" 65 #include "log-internal.h" 66 #include "evmap-internal.h" 67 #include "evthread-internal.h" 68 69 /* 70 signal.c 71 72 This is the signal-handling implementation we use for backends that don't 73 have a better way to do signal handling. It uses sigaction() or signal() 74 to set a signal handler, and a socket pair to tell the event base when 75 76 Note that I said "the event base" : only one event base can be set up to use 77 this at a time. For historical reasons and backward compatibility, if you 78 add an event for a signal to event_base A, then add an event for a signal 79 (any signal!) to event_base B, event_base B will get informed about the 80 signal, but event_base A won't. 81 82 It would be neat to change this behavior in some future version of Libevent. 83 kqueue already does something far more sensible. We can make all backends 84 on Linux do a reasonable thing using signalfd. 85 */ 86 87 #ifndef WIN32 88 /* Windows wants us to call our signal handlers as __cdecl. Nobody else 89 * expects you to do anything crazy like this. */ 90 #define __cdecl 91 #endif 92 93 static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *); 94 static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *); 95 96 static const struct eventop evsigops = { 97 "signal", 98 NULL, 99 evsig_add, 100 evsig_del, 101 NULL, 102 NULL, 103 0, 0, 0 104 }; 105 106 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 107 /* Lock for evsig_base and evsig_base_n_signals_added fields. */ 108 static void *evsig_base_lock = NULL; 109 #endif 110 /* The event base that's currently getting informed about signals. */ 111 static struct event_base *evsig_base = NULL; 112 /* A copy of evsig_base->sigev_n_signals_added. */ 113 static int evsig_base_n_signals_added = 0; 114 static evutil_socket_t evsig_base_fd = -1; 115 116 static void __cdecl evsig_handler(int sig); 117 118 #define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0) 119 #define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0) 120 121 void 122 evsig_set_base(struct event_base *base) 123 { 124 EVSIGBASE_LOCK(); 125 evsig_base = base; 126 evsig_base_n_signals_added = base->sig.ev_n_signals_added; 127 evsig_base_fd = base->sig.ev_signal_pair[0]; 128 EVSIGBASE_UNLOCK(); 129 } 130 131 /* Callback for when the signal handler write a byte to our signaling socket */ 132 static void 133 evsig_cb(evutil_socket_t fd, short what, void *arg) 134 { 135 static char signals[1024]; 136 ev_ssize_t n; 137 int i; 138 int ncaught[NSIG]; 139 struct event_base *base; 140 141 base = arg; 142 143 memset(&ncaught, 0, sizeof(ncaught)); 144 145 while (1) { 146 n = recv(fd, signals, sizeof(signals), 0); 147 if (n == -1) { 148 int err = evutil_socket_geterror(fd); 149 if (! EVUTIL_ERR_RW_RETRIABLE(err)) 150 event_sock_err(1, fd, "%s: recv", __func__); 151 break; 152 } else if (n == 0) { 153 /* XXX warn? */ 154 break; 155 } 156 for (i = 0; i < n; ++i) { 157 ev_uint8_t sig = signals[i]; 158 if (sig < NSIG) 159 ncaught[sig]++; 160 } 161 } 162 163 EVBASE_ACQUIRE_LOCK(base, th_base_lock); 164 for (i = 0; i < NSIG; ++i) { 165 if (ncaught[i]) 166 evmap_signal_active(base, i, ncaught[i]); 167 } 168 EVBASE_RELEASE_LOCK(base, th_base_lock); 169 } 170 171 int 172 evsig_init(struct event_base *base) 173 { 174 /* 175 * Our signal handler is going to write to one end of the socket 176 * pair to wake up our event loop. The event loop then scans for 177 * signals that got delivered. 178 */ 179 if (evutil_socketpair( 180 AF_UNIX, SOCK_STREAM, 0, base->sig.ev_signal_pair) == -1) { 181 #ifdef WIN32 182 /* Make this nonfatal on win32, where sometimes people 183 have localhost firewalled. */ 184 event_sock_warn(-1, "%s: socketpair", __func__); 185 #else 186 event_sock_err(1, -1, "%s: socketpair", __func__); 187 #endif 188 return -1; 189 } 190 191 evutil_make_socket_closeonexec(base->sig.ev_signal_pair[0]); 192 evutil_make_socket_closeonexec(base->sig.ev_signal_pair[1]); 193 base->sig.sh_old = NULL; 194 base->sig.sh_old_max = 0; 195 196 evutil_make_socket_nonblocking(base->sig.ev_signal_pair[0]); 197 evutil_make_socket_nonblocking(base->sig.ev_signal_pair[1]); 198 199 event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[1], 200 EV_READ | EV_PERSIST, evsig_cb, base); 201 202 base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL; 203 event_priority_set(&base->sig.ev_signal, 0); 204 205 base->evsigsel = &evsigops; 206 207 return 0; 208 } 209 210 /* Helper: set the signal handler for evsignal to handler in base, so that 211 * we can restore the original handler when we clear the current one. */ 212 int 213 _evsig_set_handler(struct event_base *base, 214 int evsignal, void (__cdecl *handler)(int)) 215 { 216 #ifdef _EVENT_HAVE_SIGACTION 217 struct sigaction sa; 218 #else 219 ev_sighandler_t sh; 220 #endif 221 struct evsig_info *sig = &base->sig; 222 void *p; 223 224 /* 225 * resize saved signal handler array up to the highest signal number. 226 * a dynamic array is used to keep footprint on the low side. 227 */ 228 if (evsignal >= sig->sh_old_max) { 229 int new_max = evsignal + 1; 230 event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing", 231 __func__, evsignal, sig->sh_old_max)); 232 p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old)); 233 if (p == NULL) { 234 event_warn("realloc"); 235 return (-1); 236 } 237 238 memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old), 239 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old)); 240 241 sig->sh_old_max = new_max; 242 sig->sh_old = p; 243 } 244 245 /* allocate space for previous handler out of dynamic array */ 246 sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]); 247 if (sig->sh_old[evsignal] == NULL) { 248 event_warn("malloc"); 249 return (-1); 250 } 251 252 /* save previous handler and setup new handler */ 253 #ifdef _EVENT_HAVE_SIGACTION 254 memset(&sa, 0, sizeof(sa)); 255 sa.sa_handler = handler; 256 sa.sa_flags |= SA_RESTART; 257 sigfillset(&sa.sa_mask); 258 259 if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) { 260 event_warn("sigaction"); 261 mm_free(sig->sh_old[evsignal]); 262 sig->sh_old[evsignal] = NULL; 263 return (-1); 264 } 265 #else 266 if ((sh = signal(evsignal, handler)) == SIG_ERR) { 267 event_warn("signal"); 268 mm_free(sig->sh_old[evsignal]); 269 sig->sh_old[evsignal] = NULL; 270 return (-1); 271 } 272 *sig->sh_old[evsignal] = sh; 273 #endif 274 275 return (0); 276 } 277 278 static int 279 evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 280 { 281 struct evsig_info *sig = &base->sig; 282 (void)p; 283 284 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 285 286 /* catch signals if they happen quickly */ 287 EVSIGBASE_LOCK(); 288 if (evsig_base != base && evsig_base_n_signals_added) { 289 event_warnx("Added a signal to event base %p with signals " 290 "already added to event_base %p. Only one can have " 291 "signals at a time with the %s backend. The base with " 292 "the most recently added signal or the most recent " 293 "event_base_loop() call gets preference; do " 294 "not rely on this behavior in future Libevent versions.", 295 base, evsig_base, base->evsel->name); 296 } 297 evsig_base = base; 298 evsig_base_n_signals_added = ++sig->ev_n_signals_added; 299 evsig_base_fd = base->sig.ev_signal_pair[0]; 300 EVSIGBASE_UNLOCK(); 301 302 event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal)); 303 if (_evsig_set_handler(base, (int)evsignal, evsig_handler) == -1) { 304 goto err; 305 } 306 307 308 if (!sig->ev_signal_added) { 309 if (event_add(&sig->ev_signal, NULL)) 310 goto err; 311 sig->ev_signal_added = 1; 312 } 313 314 return (0); 315 316 err: 317 EVSIGBASE_LOCK(); 318 --evsig_base_n_signals_added; 319 --sig->ev_n_signals_added; 320 EVSIGBASE_UNLOCK(); 321 return (-1); 322 } 323 324 int 325 _evsig_restore_handler(struct event_base *base, int evsignal) 326 { 327 int ret = 0; 328 struct evsig_info *sig = &base->sig; 329 #ifdef _EVENT_HAVE_SIGACTION 330 struct sigaction *sh; 331 #else 332 ev_sighandler_t *sh; 333 #endif 334 335 /* restore previous handler */ 336 sh = sig->sh_old[evsignal]; 337 sig->sh_old[evsignal] = NULL; 338 #ifdef _EVENT_HAVE_SIGACTION 339 if (sigaction(evsignal, sh, NULL) == -1) { 340 event_warn("sigaction"); 341 ret = -1; 342 } 343 #else 344 if (signal(evsignal, *sh) == SIG_ERR) { 345 event_warn("signal"); 346 ret = -1; 347 } 348 #endif 349 350 mm_free(sh); 351 352 return ret; 353 } 354 355 static int 356 evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 357 { 358 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 359 360 event_debug(("%s: "EV_SOCK_FMT": restoring signal handler", 361 __func__, EV_SOCK_ARG(evsignal))); 362 363 EVSIGBASE_LOCK(); 364 --evsig_base_n_signals_added; 365 --base->sig.ev_n_signals_added; 366 EVSIGBASE_UNLOCK(); 367 368 return (_evsig_restore_handler(base, (int)evsignal)); 369 } 370 371 static void __cdecl 372 evsig_handler(int sig) 373 { 374 int save_errno = errno; 375 #ifdef WIN32 376 int socket_errno = EVUTIL_SOCKET_ERROR(); 377 #endif 378 ev_uint8_t msg; 379 380 if (evsig_base == NULL) { 381 event_warnx( 382 "%s: received signal %d, but have no base configured", 383 __func__, sig); 384 return; 385 } 386 387 #ifndef _EVENT_HAVE_SIGACTION 388 signal(sig, evsig_handler); 389 #endif 390 391 /* Wake up our notification mechanism */ 392 msg = sig; 393 send(evsig_base_fd, (char*)&msg, 1, 0); 394 errno = save_errno; 395 #ifdef WIN32 396 EVUTIL_SET_SOCKET_ERROR(socket_errno); 397 #endif 398 } 399 400 void 401 evsig_dealloc(struct event_base *base) 402 { 403 int i = 0; 404 if (base->sig.ev_signal_added) { 405 event_del(&base->sig.ev_signal); 406 base->sig.ev_signal_added = 0; 407 } 408 /* debug event is created in evsig_init/event_assign even when 409 * ev_signal_added == 0, so unassign is required */ 410 event_debug_unassign(&base->sig.ev_signal); 411 412 for (i = 0; i < NSIG; ++i) { 413 if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL) 414 _evsig_restore_handler(base, i); 415 } 416 EVSIGBASE_LOCK(); 417 if (base == evsig_base) { 418 evsig_base = NULL; 419 evsig_base_n_signals_added = 0; 420 evsig_base_fd = -1; 421 } 422 EVSIGBASE_UNLOCK(); 423 424 if (base->sig.ev_signal_pair[0] != -1) { 425 evutil_closesocket(base->sig.ev_signal_pair[0]); 426 base->sig.ev_signal_pair[0] = -1; 427 } 428 if (base->sig.ev_signal_pair[1] != -1) { 429 evutil_closesocket(base->sig.ev_signal_pair[1]); 430 base->sig.ev_signal_pair[1] = -1; 431 } 432 base->sig.sh_old_max = 0; 433 434 /* per index frees are handled in evsig_del() */ 435 if (base->sig.sh_old) { 436 mm_free(base->sig.sh_old); 437 base->sig.sh_old = NULL; 438 } 439 } 440 441 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 442 int 443 evsig_global_setup_locks_(const int enable_locks) 444 { 445 EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0); 446 return 0; 447 } 448 #endif 449