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 evsig_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 */ 130 static void 131 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 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 } 172 173 int 174 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 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. */ 211 int 212 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 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 } 276 277 static int 278 evsig_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); 314 315 err: 316 EVSIGBASE_LOCK(); 317 --evsig_base_n_signals_added; 318 --sig->ev_n_signals_added; 319 EVSIGBASE_UNLOCK(); 320 return (-1); 321 } 322 323 int 324 evsig_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 } 359 360 static int 361 evsig_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 } 375 376 static void __cdecl 377 evsig_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 } 411 412 void 413 evsig_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 } 452 453 static void 454 evsig_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 } 464 465 void 466 evsig_free_globals_(void) 467 { 468 evsig_free_globals_locks(); 469 } 470 471 #ifndef EVENT__DISABLE_THREAD_SUPPORT 472 int 473 evsig_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