signal.c

   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