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 #ifndef __cdecl 89 #define __cdecl 90 #endif 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[1]; 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 #ifdef _WIN32 147 n = recv(fd, signals, sizeof(signals), 0); 148 #else 149 n = read(fd, signals, sizeof(signals)); 150 #endif 151 if (n == -1) { 152 int err = evutil_socket_geterror(fd); 153 if (! EVUTIL_ERR_RW_RETRIABLE(err)) 154 event_sock_err(1, fd, "%s: recv", __func__); 155 break; 156 } else if (n == 0) { 157 /* XXX warn? */ 158 break; 159 } 160 for (i = 0; i < n; ++i) { 161 ev_uint8_t sig = signals[i]; 162 if (sig < NSIG) 163 ncaught[sig]++; 164 } 165 } 166 167 EVBASE_ACQUIRE_LOCK(base, th_base_lock); 168 for (i = 0; i < NSIG; ++i) { 169 if (ncaught[i]) 170 evmap_signal_active_(base, i, ncaught[i]); 171 } 172 EVBASE_RELEASE_LOCK(base, th_base_lock); 173 } 174 175 int 176 evsig_init_(struct event_base *base) 177 { 178 /* 179 * Our signal handler is going to write to one end of the socket 180 * pair to wake up our event loop. The event loop then scans for 181 * signals that got delivered. 182 */ 183 if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) { 184 #ifdef _WIN32 185 /* Make this nonfatal on win32, where sometimes people 186 have localhost firewalled. */ 187 event_sock_warn(-1, "%s: socketpair", __func__); 188 #else 189 event_sock_err(1, -1, "%s: socketpair", __func__); 190 #endif 191 return -1; 192 } 193 194 if (base->sig.sh_old) { 195 mm_free(base->sig.sh_old); 196 } 197 base->sig.sh_old = NULL; 198 base->sig.sh_old_max = 0; 199 200 event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0], 201 EV_READ | EV_PERSIST, evsig_cb, base); 202 203 base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL; 204 event_priority_set(&base->sig.ev_signal, 0); 205 206 base->evsigsel = &evsigops; 207 208 return 0; 209 } 210 211 /* Helper: set the signal handler for evsignal to handler in base, so that 212 * we can restore the original handler when we clear the current one. */ 213 int 214 evsig_set_handler_(struct event_base *base, 215 int evsignal, void (__cdecl *handler)(int)) 216 { 217 #ifdef EVENT__HAVE_SIGACTION 218 struct sigaction sa; 219 #else 220 ev_sighandler_t sh; 221 #endif 222 struct evsig_info *sig = &base->sig; 223 void *p; 224 225 /* 226 * resize saved signal handler array up to the highest signal number. 227 * a dynamic array is used to keep footprint on the low side. 228 */ 229 if (evsignal >= sig->sh_old_max) { 230 int new_max = evsignal + 1; 231 event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing", 232 __func__, evsignal, sig->sh_old_max)); 233 p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old)); 234 if (p == NULL) { 235 event_warn("realloc"); 236 return (-1); 237 } 238 239 memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old), 240 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old)); 241 242 sig->sh_old_max = new_max; 243 sig->sh_old = p; 244 } 245 246 /* allocate space for previous handler out of dynamic array */ 247 sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]); 248 if (sig->sh_old[evsignal] == NULL) { 249 event_warn("malloc"); 250 return (-1); 251 } 252 253 /* save previous handler and setup new handler */ 254 #ifdef EVENT__HAVE_SIGACTION 255 memset(&sa, 0, sizeof(sa)); 256 sa.sa_handler = handler; 257 sa.sa_flags |= SA_RESTART; 258 sigfillset(&sa.sa_mask); 259 260 if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) { 261 event_warn("sigaction"); 262 mm_free(sig->sh_old[evsignal]); 263 sig->sh_old[evsignal] = NULL; 264 return (-1); 265 } 266 #else 267 if ((sh = signal(evsignal, handler)) == SIG_ERR) { 268 event_warn("signal"); 269 mm_free(sig->sh_old[evsignal]); 270 sig->sh_old[evsignal] = NULL; 271 return (-1); 272 } 273 *sig->sh_old[evsignal] = sh; 274 #endif 275 276 return (0); 277 } 278 279 static int 280 evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 281 { 282 struct evsig_info *sig = &base->sig; 283 (void)p; 284 285 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 286 287 /* catch signals if they happen quickly */ 288 EVSIGBASE_LOCK(); 289 if (evsig_base != base && evsig_base_n_signals_added) { 290 event_warnx("Added a signal to event base %p with signals " 291 "already added to event_base %p. Only one can have " 292 "signals at a time with the %s backend. The base with " 293 "the most recently added signal or the most recent " 294 "event_base_loop() call gets preference; do " 295 "not rely on this behavior in future Libevent versions.", 296 base, evsig_base, base->evsel->name); 297 } 298 evsig_base = base; 299 evsig_base_n_signals_added = ++sig->ev_n_signals_added; 300 evsig_base_fd = base->sig.ev_signal_pair[1]; 301 EVSIGBASE_UNLOCK(); 302 303 event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal)); 304 if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) { 305 goto err; 306 } 307 308 309 if (!sig->ev_signal_added) { 310 if (event_add_nolock_(&sig->ev_signal, NULL, 0)) 311 goto err; 312 sig->ev_signal_added = 1; 313 } 314 315 return (0); 316 317 err: 318 EVSIGBASE_LOCK(); 319 --evsig_base_n_signals_added; 320 --sig->ev_n_signals_added; 321 EVSIGBASE_UNLOCK(); 322 return (-1); 323 } 324 325 int 326 evsig_restore_handler_(struct event_base *base, int evsignal) 327 { 328 int ret = 0; 329 struct evsig_info *sig = &base->sig; 330 #ifdef EVENT__HAVE_SIGACTION 331 struct sigaction *sh; 332 #else 333 ev_sighandler_t *sh; 334 #endif 335 336 if (evsignal >= sig->sh_old_max) { 337 /* Can't actually restore. */ 338 /* XXXX.*/ 339 return 0; 340 } 341 342 /* restore previous handler */ 343 sh = sig->sh_old[evsignal]; 344 sig->sh_old[evsignal] = NULL; 345 #ifdef EVENT__HAVE_SIGACTION 346 if (sigaction(evsignal, sh, NULL) == -1) { 347 event_warn("sigaction"); 348 ret = -1; 349 } 350 #else 351 if (signal(evsignal, *sh) == SIG_ERR) { 352 event_warn("signal"); 353 ret = -1; 354 } 355 #endif 356 357 mm_free(sh); 358 359 return ret; 360 } 361 362 static int 363 evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 364 { 365 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 366 367 event_debug(("%s: "EV_SOCK_FMT": restoring signal handler", 368 __func__, EV_SOCK_ARG(evsignal))); 369 370 EVSIGBASE_LOCK(); 371 --evsig_base_n_signals_added; 372 --base->sig.ev_n_signals_added; 373 EVSIGBASE_UNLOCK(); 374 375 return (evsig_restore_handler_(base, (int)evsignal)); 376 } 377 378 static void __cdecl 379 evsig_handler(int sig) 380 { 381 int save_errno = errno; 382 #ifdef _WIN32 383 int socket_errno = EVUTIL_SOCKET_ERROR(); 384 #endif 385 ev_uint8_t msg; 386 387 if (evsig_base == NULL) { 388 event_warnx( 389 "%s: received signal %d, but have no base configured", 390 __func__, sig); 391 return; 392 } 393 394 #ifndef EVENT__HAVE_SIGACTION 395 signal(sig, evsig_handler); 396 #endif 397 398 /* Wake up our notification mechanism */ 399 msg = sig; 400 #ifdef _WIN32 401 send(evsig_base_fd, (char*)&msg, 1, 0); 402 #else 403 { 404 int r = write(evsig_base_fd, (char*)&msg, 1); 405 (void)r; /* Suppress 'unused return value' and 'unused var' */ 406 } 407 #endif 408 errno = save_errno; 409 #ifdef _WIN32 410 EVUTIL_SET_SOCKET_ERROR(socket_errno); 411 #endif 412 } 413 414 void 415 evsig_dealloc_(struct event_base *base) 416 { 417 int i = 0; 418 if (base->sig.ev_signal_added) { 419 event_del(&base->sig.ev_signal); 420 base->sig.ev_signal_added = 0; 421 } 422 /* debug event is created in evsig_init_/event_assign even when 423 * ev_signal_added == 0, so unassign is required */ 424 event_debug_unassign(&base->sig.ev_signal); 425 426 for (i = 0; i < NSIG; ++i) { 427 if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL) 428 evsig_restore_handler_(base, i); 429 } 430 EVSIGBASE_LOCK(); 431 if (base == evsig_base) { 432 evsig_base = NULL; 433 evsig_base_n_signals_added = 0; 434 evsig_base_fd = -1; 435 } 436 EVSIGBASE_UNLOCK(); 437 438 if (base->sig.ev_signal_pair[0] != -1) { 439 evutil_closesocket(base->sig.ev_signal_pair[0]); 440 base->sig.ev_signal_pair[0] = -1; 441 } 442 if (base->sig.ev_signal_pair[1] != -1) { 443 evutil_closesocket(base->sig.ev_signal_pair[1]); 444 base->sig.ev_signal_pair[1] = -1; 445 } 446 base->sig.sh_old_max = 0; 447 448 /* per index frees are handled in evsig_del() */ 449 if (base->sig.sh_old) { 450 mm_free(base->sig.sh_old); 451 base->sig.sh_old = NULL; 452 } 453 } 454 455 static void 456 evsig_free_globals_locks(void) 457 { 458 #ifndef EVENT__DISABLE_THREAD_SUPPORT 459 if (evsig_base_lock != NULL) { 460 EVTHREAD_FREE_LOCK(evsig_base_lock, 0); 461 evsig_base_lock = NULL; 462 } 463 #endif 464 return; 465 } 466 467 void 468 evsig_free_globals_(void) 469 { 470 evsig_free_globals_locks(); 471 } 472 473 #ifndef EVENT__DISABLE_THREAD_SUPPORT 474 int 475 evsig_global_setup_locks_(const int enable_locks) 476 { 477 EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0); 478 return 0; 479 } 480 481 #endif 482