1 /* $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $ */ 2 3 /* 4 * Copyright 2000-2007 Niels Provos <provos (at) 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 31 #ifdef WIN32 32 #define WIN32_LEAN_AND_MEAN 33 #include <winsock2.h> 34 #include <windows.h> 35 #undef WIN32_LEAN_AND_MEAN 36 #endif 37 #include <sys/types.h> 38 #ifdef _EVENT_HAVE_SYS_TIME_H 39 #include <sys/time.h> 40 #endif 41 #include <sys/queue.h> 42 #ifdef _EVENT_HAVE_SYS_SOCKET_H 43 #include <sys/socket.h> 44 #endif 45 #include <signal.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include <string.h> 49 #ifdef _EVENT_HAVE_UNISTD_H 50 #include <unistd.h> 51 #endif 52 #include <errno.h> 53 #ifdef _EVENT_HAVE_FCNTL_H 54 #include <fcntl.h> 55 #endif 56 57 #include "event2/event.h" 58 #include "event2/event_struct.h" 59 #include "event-internal.h" 60 #include "event2/util.h" 61 #include "evsignal-internal.h" 62 #include "log-internal.h" 63 #include "evmap-internal.h" 64 #include "evthread-internal.h" 65 66 /* 67 signal.c 68 69 This is the signal-handling implementation we use for backends that don't 70 have a better way to do signal handling. It uses sigaction() or signal() 71 to set a signal handler, and a socket pair to tell the event base when 72 73 Note that I said "the event base" : only one event base can be set up to use 74 this at a time. For historical reasons and backward compatibility, if you 75 add an event for a signal to event_base A, then add an event for a signal 76 (any signal!) to event_base B, event_base B will get informed about the 77 signal, but event_base A won't. 78 79 It would be neat to change this behavior in some future version of Libevent. 80 kqueue already does something far more sensible. We can make all backends 81 on Linux do a reasonable thing using signalfd. 82 */ 83 84 #ifndef WIN32 85 /* Windows wants us to call our signal handlers as __cdecl. Nobody else 86 * expects you to do anything crazy like this. */ 87 #define __cdecl 88 #endif 89 90 static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *); 91 static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *); 92 93 static const struct eventop evsigops = { 94 "signal", 95 NULL, 96 evsig_add, 97 evsig_del, 98 NULL, 99 NULL, 100 0, 0, 0 101 }; 102 103 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 104 /* Lock for evsig_base and evsig_base_n_signals_added fields. */ 105 static void *evsig_base_lock = NULL; 106 #endif 107 /* The event base that's currently getting informed about signals. */ 108 static struct event_base *evsig_base = NULL; 109 /* A copy of evsig_base->sigev_n_signals_added. */ 110 static int evsig_base_n_signals_added = 0; 111 static evutil_socket_t evsig_base_fd = -1; 112 113 static void __cdecl evsig_handler(int sig); 114 115 #define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0) 116 #define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0) 117 118 void 119 evsig_set_base(struct event_base *base) 120 { 121 EVSIGBASE_LOCK(); 122 evsig_base = base; 123 evsig_base_n_signals_added = base->sig.ev_n_signals_added; 124 evsig_base_fd = base->sig.ev_signal_pair[0]; 125 EVSIGBASE_UNLOCK(); 126 } 127 128 /* Callback for when the signal handler write a byte to our signaling socket */ 129 static void 130 evsig_cb(evutil_socket_t fd, short what, void *arg) 131 { 132 static char signals[1024]; 133 ev_ssize_t n; 134 int i; 135 int ncaught[NSIG]; 136 struct event_base *base; 137 138 base = arg; 139 140 memset(&ncaught, 0, sizeof(ncaught)); 141 142 while (1) { 143 n = recv(fd, signals, sizeof(signals), 0); 144 if (n == -1) { 145 int err = evutil_socket_geterror(fd); 146 if (! EVUTIL_ERR_RW_RETRIABLE(err)) 147 event_sock_err(1, fd, "%s: recv", __func__); 148 break; 149 } else if (n == 0) { 150 /* XXX warn? */ 151 break; 152 } 153 for (i = 0; i < n; ++i) { 154 ev_uint8_t sig = signals[i]; 155 if (sig < NSIG) 156 ncaught[sig]++; 157 } 158 } 159 160 EVBASE_ACQUIRE_LOCK(base, th_base_lock); 161 for (i = 0; i < NSIG; ++i) { 162 if (ncaught[i]) 163 evmap_signal_active(base, i, ncaught[i]); 164 } 165 EVBASE_RELEASE_LOCK(base, th_base_lock); 166 } 167 168 int 169 evsig_init(struct event_base *base) 170 { 171 /* 172 * Our signal handler is going to write to one end of the socket 173 * pair to wake up our event loop. The event loop then scans for 174 * signals that got delivered. 175 */ 176 if (evutil_socketpair( 177 AF_UNIX, SOCK_STREAM, 0, base->sig.ev_signal_pair) == -1) { 178 #ifdef WIN32 179 /* Make this nonfatal on win32, where sometimes people 180 have localhost firewalled. */ 181 event_sock_warn(-1, "%s: socketpair", __func__); 182 #else 183 event_sock_err(1, -1, "%s: socketpair", __func__); 184 #endif 185 return -1; 186 } 187 188 evutil_make_socket_closeonexec(base->sig.ev_signal_pair[0]); 189 evutil_make_socket_closeonexec(base->sig.ev_signal_pair[1]); 190 base->sig.sh_old = NULL; 191 base->sig.sh_old_max = 0; 192 193 evutil_make_socket_nonblocking(base->sig.ev_signal_pair[0]); 194 evutil_make_socket_nonblocking(base->sig.ev_signal_pair[1]); 195 196 event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[1], 197 EV_READ | EV_PERSIST, evsig_cb, base); 198 199 base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL; 200 event_priority_set(&base->sig.ev_signal, 0); 201 202 base->evsigsel = &evsigops; 203 204 return 0; 205 } 206 207 /* Helper: set the signal handler for evsignal to handler in base, so that 208 * we can restore the original handler when we clear the current one. */ 209 int 210 _evsig_set_handler(struct event_base *base, 211 int evsignal, void (__cdecl *handler)(int)) 212 { 213 #ifdef _EVENT_HAVE_SIGACTION 214 struct sigaction sa; 215 #else 216 ev_sighandler_t sh; 217 #endif 218 struct evsig_info *sig = &base->sig; 219 void *p; 220 221 /* 222 * resize saved signal handler array up to the highest signal number. 223 * a dynamic array is used to keep footprint on the low side. 224 */ 225 if (evsignal >= sig->sh_old_max) { 226 int new_max = evsignal + 1; 227 event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing", 228 __func__, evsignal, sig->sh_old_max)); 229 p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old)); 230 if (p == NULL) { 231 event_warn("realloc"); 232 return (-1); 233 } 234 235 memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old), 236 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old)); 237 238 sig->sh_old_max = new_max; 239 sig->sh_old = p; 240 } 241 242 /* allocate space for previous handler out of dynamic array */ 243 sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]); 244 if (sig->sh_old[evsignal] == NULL) { 245 event_warn("malloc"); 246 return (-1); 247 } 248 249 /* save previous handler and setup new handler */ 250 #ifdef _EVENT_HAVE_SIGACTION 251 memset(&sa, 0, sizeof(sa)); 252 sa.sa_handler = handler; 253 sa.sa_flags |= SA_RESTART; 254 sigfillset(&sa.sa_mask); 255 256 if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) { 257 event_warn("sigaction"); 258 mm_free(sig->sh_old[evsignal]); 259 sig->sh_old[evsignal] = NULL; 260 return (-1); 261 } 262 #else 263 if ((sh = signal(evsignal, handler)) == SIG_ERR) { 264 event_warn("signal"); 265 mm_free(sig->sh_old[evsignal]); 266 sig->sh_old[evsignal] = NULL; 267 return (-1); 268 } 269 *sig->sh_old[evsignal] = sh; 270 #endif 271 272 return (0); 273 } 274 275 static int 276 evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 277 { 278 struct evsig_info *sig = &base->sig; 279 (void)p; 280 281 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 282 283 /* catch signals if they happen quickly */ 284 EVSIGBASE_LOCK(); 285 if (evsig_base != base && evsig_base_n_signals_added) { 286 event_warnx("Added a signal to event base %p with signals " 287 "already added to event_base %p. Only one can have " 288 "signals at a time with the %s backend. The base with " 289 "the most recently added signal or the most recent " 290 "event_base_loop() call gets preference; do " 291 "not rely on this behavior in future Libevent versions.", 292 base, evsig_base, base->evsel->name); 293 } 294 evsig_base = base; 295 evsig_base_n_signals_added = ++sig->ev_n_signals_added; 296 evsig_base_fd = base->sig.ev_signal_pair[0]; 297 EVSIGBASE_UNLOCK(); 298 299 event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal)); 300 if (_evsig_set_handler(base, (int)evsignal, evsig_handler) == -1) { 301 goto err; 302 } 303 304 305 if (!sig->ev_signal_added) { 306 if (event_add(&sig->ev_signal, NULL)) 307 goto err; 308 sig->ev_signal_added = 1; 309 } 310 311 return (0); 312 313 err: 314 EVSIGBASE_LOCK(); 315 --evsig_base_n_signals_added; 316 --sig->ev_n_signals_added; 317 EVSIGBASE_UNLOCK(); 318 return (-1); 319 } 320 321 int 322 _evsig_restore_handler(struct event_base *base, int evsignal) 323 { 324 int ret = 0; 325 struct evsig_info *sig = &base->sig; 326 #ifdef _EVENT_HAVE_SIGACTION 327 struct sigaction *sh; 328 #else 329 ev_sighandler_t *sh; 330 #endif 331 332 /* restore previous handler */ 333 sh = sig->sh_old[evsignal]; 334 sig->sh_old[evsignal] = NULL; 335 #ifdef _EVENT_HAVE_SIGACTION 336 if (sigaction(evsignal, sh, NULL) == -1) { 337 event_warn("sigaction"); 338 ret = -1; 339 } 340 #else 341 if (signal(evsignal, *sh) == SIG_ERR) { 342 event_warn("signal"); 343 ret = -1; 344 } 345 #endif 346 347 mm_free(sh); 348 349 return ret; 350 } 351 352 static int 353 evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 354 { 355 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 356 357 event_debug(("%s: "EV_SOCK_FMT": restoring signal handler", 358 __func__, EV_SOCK_ARG(evsignal))); 359 360 EVSIGBASE_LOCK(); 361 --evsig_base_n_signals_added; 362 --base->sig.ev_n_signals_added; 363 EVSIGBASE_UNLOCK(); 364 365 return (_evsig_restore_handler(base, (int)evsignal)); 366 } 367 368 static void __cdecl 369 evsig_handler(int sig) 370 { 371 int save_errno = errno; 372 #ifdef WIN32 373 int socket_errno = EVUTIL_SOCKET_ERROR(); 374 #endif 375 ev_uint8_t msg; 376 377 if (evsig_base == NULL) { 378 event_warnx( 379 "%s: received signal %d, but have no base configured", 380 __func__, sig); 381 return; 382 } 383 384 #ifndef _EVENT_HAVE_SIGACTION 385 signal(sig, evsig_handler); 386 #endif 387 388 /* Wake up our notification mechanism */ 389 msg = sig; 390 send(evsig_base_fd, (char*)&msg, 1, 0); 391 errno = save_errno; 392 #ifdef WIN32 393 EVUTIL_SET_SOCKET_ERROR(socket_errno); 394 #endif 395 } 396 397 void 398 evsig_dealloc(struct event_base *base) 399 { 400 int i = 0; 401 if (base->sig.ev_signal_added) { 402 event_del(&base->sig.ev_signal); 403 base->sig.ev_signal_added = 0; 404 } 405 /* debug event is created in evsig_init/event_assign even when 406 * ev_signal_added == 0, so unassign is required */ 407 event_debug_unassign(&base->sig.ev_signal); 408 409 for (i = 0; i < NSIG; ++i) { 410 if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL) 411 _evsig_restore_handler(base, i); 412 } 413 EVSIGBASE_LOCK(); 414 if (base == evsig_base) { 415 evsig_base = NULL; 416 evsig_base_n_signals_added = 0; 417 evsig_base_fd = -1; 418 } 419 EVSIGBASE_UNLOCK(); 420 421 if (base->sig.ev_signal_pair[0] != -1) { 422 evutil_closesocket(base->sig.ev_signal_pair[0]); 423 base->sig.ev_signal_pair[0] = -1; 424 } 425 if (base->sig.ev_signal_pair[1] != -1) { 426 evutil_closesocket(base->sig.ev_signal_pair[1]); 427 base->sig.ev_signal_pair[1] = -1; 428 } 429 base->sig.sh_old_max = 0; 430 431 /* per index frees are handled in evsig_del() */ 432 if (base->sig.sh_old) { 433 mm_free(base->sig.sh_old); 434 base->sig.sh_old = NULL; 435 } 436 } 437 438 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 439 int 440 evsig_global_setup_locks_(const int enable_locks) 441 { 442 EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0); 443 return 0; 444 } 445 #endif 446
