1/* $NetBSD: signal.c,v 1.1.1.4 2021/04/07 02:43:13 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 1.1.1.4 2021/04/07 02:43:13 christos Exp $"); 33#include "evconfig-private.h" 34 35#ifdef _WIN32 36#define WIN32_LEAN_AND_MEAN 37#include <winsock2.h> 38#include <windows.h> 39#undef WIN32_LEAN_AND_MEAN 40#endif 41#include <sys/types.h> 42#ifdef EVENT__HAVE_SYS_TIME_H 43#include <sys/time.h> 44#endif 45#include <sys/queue.h> 46#ifdef EVENT__HAVE_SYS_SOCKET_H 47#include <sys/socket.h> 48#endif 49#include <signal.h> 50#include <stdio.h> 51#include <stdlib.h> 52#include <string.h> 53#ifdef EVENT__HAVE_UNISTD_H 54#include <unistd.h> 55#endif 56#include <errno.h> 57#ifdef EVENT__HAVE_FCNTL_H 58#include <fcntl.h> 59#endif 60 61#include "event2/event.h" 62#include "event2/event_struct.h" 63#include "event-internal.h" 64#include "event2/util.h" 65#include "evsignal-internal.h" 66#include "log-internal.h" 67#include "evmap-internal.h" 68#include "evthread-internal.h" 69 70/* 71 signal.c 72 73 This is the signal-handling implementation we use for backends that don't 74 have a better way to do signal handling. It uses sigaction() or signal() 75 to set a signal handler, and a socket pair to tell the event base when 76 77 Note that I said "the event base" : only one event base can be set up to use 78 this at a time. For historical reasons and backward compatibility, if you 79 add an event for a signal to event_base A, then add an event for a signal 80 (any signal!) to event_base B, event_base B will get informed about the 81 signal, but event_base A won't. 82 83 It would be neat to change this behavior in some future version of Libevent. 84 kqueue already does something far more sensible. We can make all backends 85 on Linux do a reasonable thing using signalfd. 86*/ 87 88#ifndef _WIN32 89/* Windows wants us to call our signal handlers as __cdecl. Nobody else 90 * expects you to do anything crazy like this. */ 91#ifndef __cdecl 92#define __cdecl 93#endif 94#endif 95 96static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *); 97static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *); 98 99static const struct eventop evsigops = { 100 "signal", 101 NULL, 102 evsig_add, 103 evsig_del, 104 NULL, 105 NULL, 106 0, 0, 0 107}; 108 109#ifndef EVENT__DISABLE_THREAD_SUPPORT 110/* Lock for evsig_base and evsig_base_n_signals_added fields. */ 111static void *evsig_base_lock = NULL; 112#endif 113/* The event base that's currently getting informed about signals. */ 114static struct event_base *evsig_base = NULL; 115/* A copy of evsig_base->sigev_n_signals_added. */ 116static int evsig_base_n_signals_added = 0; 117static evutil_socket_t evsig_base_fd = -1; 118 119static void __cdecl evsig_handler(int sig); 120 121#define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0) 122#define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0) 123 124void 125evsig_set_base_(struct event_base *base) 126{ 127 EVSIGBASE_LOCK(); 128 evsig_base = base; 129 evsig_base_n_signals_added = base->sig.ev_n_signals_added; 130 evsig_base_fd = base->sig.ev_signal_pair[1]; 131 EVSIGBASE_UNLOCK(); 132} 133 134/* Callback for when the signal handler write a byte to our signaling socket */ 135static void 136evsig_cb(evutil_socket_t fd, short what, void *arg) 137{ 138 static char signals[1024]; 139 ev_ssize_t n; 140 int i; 141 int ncaught[NSIG]; 142 struct event_base *base; 143 144 base = arg; 145 146 memset(&ncaught, 0, sizeof(ncaught)); 147 148 while (1) { 149#ifdef _WIN32 150 n = recv(fd, signals, sizeof(signals), 0); 151#else 152 n = read(fd, signals, sizeof(signals)); 153#endif 154 if (n == -1) { 155 int err = evutil_socket_geterror(fd); 156 if (! EVUTIL_ERR_RW_RETRIABLE(err)) 157 event_sock_err(1, fd, "%s: recv", __func__); 158 break; 159 } else if (n == 0) { 160 /* XXX warn? */ 161 break; 162 } 163 for (i = 0; i < n; ++i) { 164 ev_uint8_t sig = signals[i]; 165 if (sig < NSIG) 166 ncaught[sig]++; 167 } 168 } 169 170 EVBASE_ACQUIRE_LOCK(base, th_base_lock); 171 for (i = 0; i < NSIG; ++i) { 172 if (ncaught[i]) 173 evmap_signal_active_(base, i, ncaught[i]); 174 } 175 EVBASE_RELEASE_LOCK(base, th_base_lock); 176} 177 178int 179evsig_init_(struct event_base *base) 180{ 181 /* 182 * Our signal handler is going to write to one end of the socket 183 * pair to wake up our event loop. The event loop then scans for 184 * signals that got delivered. 185 */ 186 if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) { 187#ifdef _WIN32 188 /* Make this nonfatal on win32, where sometimes people 189 have localhost firewalled. */ 190 event_sock_warn(-1, "%s: socketpair", __func__); 191#else 192 event_sock_err(1, -1, "%s: socketpair", __func__); 193#endif 194 return -1; 195 } 196 197 if (base->sig.sh_old) { 198 mm_free(base->sig.sh_old); 199 } 200 base->sig.sh_old = NULL; 201 base->sig.sh_old_max = 0; 202 203 event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0], 204 EV_READ | EV_PERSIST, evsig_cb, base); 205 206 base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL; 207 event_priority_set(&base->sig.ev_signal, 0); 208 209 base->evsigsel = &evsigops; 210 211 return 0; 212} 213 214/* Helper: set the signal handler for evsignal to handler in base, so that 215 * we can restore the original handler when we clear the current one. */ 216int 217evsig_set_handler_(struct event_base *base, 218 int evsignal, void (__cdecl *handler)(int)) 219{ 220#ifdef EVENT__HAVE_SIGACTION 221 struct sigaction sa; 222#else 223 ev_sighandler_t sh; 224#endif 225 struct evsig_info *sig = &base->sig; 226 void *p; 227 228 /* 229 * resize saved signal handler array up to the highest signal number. 230 * a dynamic array is used to keep footprint on the low side. 231 */ 232 if (evsignal >= sig->sh_old_max) { 233 int new_max = evsignal + 1; 234 event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing", 235 __func__, evsignal, sig->sh_old_max)); 236 p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old)); 237 if (p == NULL) { 238 event_warn("realloc"); 239 return (-1); 240 } 241 242 memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old), 243 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old)); 244 245 sig->sh_old_max = new_max; 246 sig->sh_old = p; 247 } 248 249 /* allocate space for previous handler out of dynamic array */ 250 sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]); 251 if (sig->sh_old[evsignal] == NULL) { 252 event_warn("malloc"); 253 return (-1); 254 } 255 256 /* save previous handler and setup new handler */ 257#ifdef EVENT__HAVE_SIGACTION 258 memset(&sa, 0, sizeof(sa)); 259 sa.sa_handler = handler; 260 sa.sa_flags |= SA_RESTART; 261 sigfillset(&sa.sa_mask); 262 263 if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) { 264 event_warn("sigaction"); 265 mm_free(sig->sh_old[evsignal]); 266 sig->sh_old[evsignal] = NULL; 267 return (-1); 268 } 269#else 270 if ((sh = signal(evsignal, handler)) == SIG_ERR) { 271 event_warn("signal"); 272 mm_free(sig->sh_old[evsignal]); 273 sig->sh_old[evsignal] = NULL; 274 return (-1); 275 } 276 *sig->sh_old[evsignal] = sh; 277#endif 278 279 return (0); 280} 281 282static int 283evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 284{ 285 struct evsig_info *sig = &base->sig; 286 (void)p; 287 288 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 289 290 /* catch signals if they happen quickly */ 291 EVSIGBASE_LOCK(); 292 if (evsig_base != base && evsig_base_n_signals_added) { 293 event_warnx("Added a signal to event base %p with signals " 294 "already added to event_base %p. Only one can have " 295 "signals at a time with the %s backend. The base with " 296 "the most recently added signal or the most recent " 297 "event_base_loop() call gets preference; do " 298 "not rely on this behavior in future Libevent versions.", 299 base, evsig_base, base->evsel->name); 300 } 301 evsig_base = base; 302 evsig_base_n_signals_added = ++sig->ev_n_signals_added; 303 evsig_base_fd = base->sig.ev_signal_pair[1]; 304 EVSIGBASE_UNLOCK(); 305 306 event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal)); 307 if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) { 308 goto err; 309 } 310 311 312 if (!sig->ev_signal_added) { 313 if (event_add_nolock_(&sig->ev_signal, NULL, 0)) 314 goto err; 315 sig->ev_signal_added = 1; 316 } 317 318 return (0); 319 320err: 321 EVSIGBASE_LOCK(); 322 --evsig_base_n_signals_added; 323 --sig->ev_n_signals_added; 324 EVSIGBASE_UNLOCK(); 325 return (-1); 326} 327 328int 329evsig_restore_handler_(struct event_base *base, int evsignal) 330{ 331 int ret = 0; 332 struct evsig_info *sig = &base->sig; 333#ifdef EVENT__HAVE_SIGACTION 334 struct sigaction *sh; 335#else 336 ev_sighandler_t *sh; 337#endif 338 339 if (evsignal >= sig->sh_old_max) { 340 /* Can't actually restore. */ 341 /* XXXX.*/ 342 return 0; 343 } 344 345 /* restore previous handler */ 346 sh = sig->sh_old[evsignal]; 347 sig->sh_old[evsignal] = NULL; 348#ifdef EVENT__HAVE_SIGACTION 349 if (sigaction(evsignal, sh, NULL) == -1) { 350 event_warn("sigaction"); 351 ret = -1; 352 } 353#else 354 if (signal(evsignal, *sh) == SIG_ERR) { 355 event_warn("signal"); 356 ret = -1; 357 } 358#endif 359 360 mm_free(sh); 361 362 return ret; 363} 364 365static int 366evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) 367{ 368 EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); 369 370 event_debug(("%s: "EV_SOCK_FMT": restoring signal handler", 371 __func__, EV_SOCK_ARG(evsignal))); 372 373 EVSIGBASE_LOCK(); 374 --evsig_base_n_signals_added; 375 --base->sig.ev_n_signals_added; 376 EVSIGBASE_UNLOCK(); 377 378 return (evsig_restore_handler_(base, (int)evsignal)); 379} 380 381static void __cdecl 382evsig_handler(int sig) 383{ 384 int save_errno = errno; 385#ifdef _WIN32 386 int socket_errno = EVUTIL_SOCKET_ERROR(); 387#endif 388 ev_uint8_t msg; 389 390 if (evsig_base == NULL) { 391 event_warnx( 392 "%s: received signal %d, but have no base configured", 393 __func__, sig); 394 return; 395 } 396 397#ifndef EVENT__HAVE_SIGACTION 398 signal(sig, evsig_handler); 399#endif 400 401 /* Wake up our notification mechanism */ 402 msg = sig; 403#ifdef _WIN32 404 send(evsig_base_fd, (char*)&msg, 1, 0); 405#else 406 { 407 int r = write(evsig_base_fd, (char*)&msg, 1); 408 (void)r; /* Suppress 'unused return value' and 'unused var' */ 409 } 410#endif 411 errno = save_errno; 412#ifdef _WIN32 413 EVUTIL_SET_SOCKET_ERROR(socket_errno); 414#endif 415} 416 417void 418evsig_dealloc_(struct event_base *base) 419{ 420 int i = 0; 421 if (base->sig.ev_signal_added) { 422 event_del(&base->sig.ev_signal); 423 base->sig.ev_signal_added = 0; 424 } 425 /* debug event is created in evsig_init_/event_assign even when 426 * ev_signal_added == 0, so unassign is required */ 427 event_debug_unassign(&base->sig.ev_signal); 428 429 for (i = 0; i < NSIG; ++i) { 430 if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL) 431 evsig_restore_handler_(base, i); 432 } 433 EVSIGBASE_LOCK(); 434 if (base == evsig_base) { 435 evsig_base = NULL; 436 evsig_base_n_signals_added = 0; 437 evsig_base_fd = -1; 438 } 439 EVSIGBASE_UNLOCK(); 440 441 if (base->sig.ev_signal_pair[0] != -1) { 442 evutil_closesocket(base->sig.ev_signal_pair[0]); 443 base->sig.ev_signal_pair[0] = -1; 444 } 445 if (base->sig.ev_signal_pair[1] != -1) { 446 evutil_closesocket(base->sig.ev_signal_pair[1]); 447 base->sig.ev_signal_pair[1] = -1; 448 } 449 base->sig.sh_old_max = 0; 450 451 /* per index frees are handled in evsig_del() */ 452 if (base->sig.sh_old) { 453 mm_free(base->sig.sh_old); 454 base->sig.sh_old = NULL; 455 } 456} 457 458static void 459evsig_free_globals_locks(void) 460{ 461#ifndef EVENT__DISABLE_THREAD_SUPPORT 462 if (evsig_base_lock != NULL) { 463 EVTHREAD_FREE_LOCK(evsig_base_lock, 0); 464 evsig_base_lock = NULL; 465 } 466#endif 467 return; 468} 469 470void 471evsig_free_globals_(void) 472{ 473 evsig_free_globals_locks(); 474} 475 476#ifndef EVENT__DISABLE_THREAD_SUPPORT 477int 478evsig_global_setup_locks_(const int enable_locks) 479{ 480 EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0); 481 return 0; 482} 483 484#endif 485