/* $NetBSD: signal.c,v 1.1.1.4 2021/04/07 02:43:13 christos Exp $ */ /* $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $ */ /* * Copyright 2000-2007 Niels Provos * Copyright 2007-2012 Niels Provos and Nick Mathewson * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "event2/event-config.h" #include __RCSID("$NetBSD: signal.c,v 1.1.1.4 2021/04/07 02:43:13 christos Exp $"); #include "evconfig-private.h" #ifdef _WIN32 #define WIN32_LEAN_AND_MEAN #include #include #undef WIN32_LEAN_AND_MEAN #endif #include #ifdef EVENT__HAVE_SYS_TIME_H #include #endif #include #ifdef EVENT__HAVE_SYS_SOCKET_H #include #endif #include #include #include #include #ifdef EVENT__HAVE_UNISTD_H #include #endif #include #ifdef EVENT__HAVE_FCNTL_H #include #endif #include "event2/event.h" #include "event2/event_struct.h" #include "event-internal.h" #include "event2/util.h" #include "evsignal-internal.h" #include "log-internal.h" #include "evmap-internal.h" #include "evthread-internal.h" /* signal.c This is the signal-handling implementation we use for backends that don't have a better way to do signal handling. It uses sigaction() or signal() to set a signal handler, and a socket pair to tell the event base when Note that I said "the event base" : only one event base can be set up to use this at a time. For historical reasons and backward compatibility, if you add an event for a signal to event_base A, then add an event for a signal (any signal!) to event_base B, event_base B will get informed about the signal, but event_base A won't. It would be neat to change this behavior in some future version of Libevent. kqueue already does something far more sensible. We can make all backends on Linux do a reasonable thing using signalfd. */ #ifndef _WIN32 /* Windows wants us to call our signal handlers as __cdecl. Nobody else * expects you to do anything crazy like this. */ #ifndef __cdecl #define __cdecl #endif #endif static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *); static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *); static const struct eventop evsigops = { "signal", NULL, evsig_add, evsig_del, NULL, NULL, 0, 0, 0 }; #ifndef EVENT__DISABLE_THREAD_SUPPORT /* Lock for evsig_base and evsig_base_n_signals_added fields. */ static void *evsig_base_lock = NULL; #endif /* The event base that's currently getting informed about signals. */ static struct event_base *evsig_base = NULL; /* A copy of evsig_base->sigev_n_signals_added. */ static int evsig_base_n_signals_added = 0; static evutil_socket_t evsig_base_fd = -1; static void __cdecl evsig_handler(int sig); #define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0) #define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0) void evsig_set_base_(struct event_base *base) { EVSIGBASE_LOCK(); evsig_base = base; evsig_base_n_signals_added = base->sig.ev_n_signals_added; evsig_base_fd = base->sig.ev_signal_pair[1]; EVSIGBASE_UNLOCK(); } /* Callback for when the signal handler write a byte to our signaling socket */ static void evsig_cb(evutil_socket_t fd, short what, void *arg) { static char signals[1024]; ev_ssize_t n; int i; int ncaught[NSIG]; struct event_base *base; base = arg; memset(&ncaught, 0, sizeof(ncaught)); while (1) { #ifdef _WIN32 n = recv(fd, signals, sizeof(signals), 0); #else n = read(fd, signals, sizeof(signals)); #endif if (n == -1) { int err = evutil_socket_geterror(fd); if (! EVUTIL_ERR_RW_RETRIABLE(err)) event_sock_err(1, fd, "%s: recv", __func__); break; } else if (n == 0) { /* XXX warn? */ break; } for (i = 0; i < n; ++i) { ev_uint8_t sig = signals[i]; if (sig < NSIG) ncaught[sig]++; } } EVBASE_ACQUIRE_LOCK(base, th_base_lock); for (i = 0; i < NSIG; ++i) { if (ncaught[i]) evmap_signal_active_(base, i, ncaught[i]); } EVBASE_RELEASE_LOCK(base, th_base_lock); } int evsig_init_(struct event_base *base) { /* * Our signal handler is going to write to one end of the socket * pair to wake up our event loop. The event loop then scans for * signals that got delivered. */ if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) { #ifdef _WIN32 /* Make this nonfatal on win32, where sometimes people have localhost firewalled. */ event_sock_warn(-1, "%s: socketpair", __func__); #else event_sock_err(1, -1, "%s: socketpair", __func__); #endif return -1; } if (base->sig.sh_old) { mm_free(base->sig.sh_old); } base->sig.sh_old = NULL; base->sig.sh_old_max = 0; event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0], EV_READ | EV_PERSIST, evsig_cb, base); base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL; event_priority_set(&base->sig.ev_signal, 0); base->evsigsel = &evsigops; return 0; } /* Helper: set the signal handler for evsignal to handler in base, so that * we can restore the original handler when we clear the current one. */ int evsig_set_handler_(struct event_base *base, int evsignal, void (__cdecl *handler)(int)) { #ifdef EVENT__HAVE_SIGACTION struct sigaction sa; #else ev_sighandler_t sh; #endif struct evsig_info *sig = &base->sig; void *p; /* * resize saved signal handler array up to the highest signal number. * a dynamic array is used to keep footprint on the low side. */ if (evsignal >= sig->sh_old_max) { int new_max = evsignal + 1; event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing", __func__, evsignal, sig->sh_old_max)); p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old)); if (p == NULL) { event_warn("realloc"); return (-1); } memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old), 0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old)); sig->sh_old_max = new_max; sig->sh_old = p; } /* allocate space for previous handler out of dynamic array */ sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]); if (sig->sh_old[evsignal] == NULL) { event_warn("malloc"); return (-1); } /* save previous handler and setup new handler */ #ifdef EVENT__HAVE_SIGACTION memset(&sa, 0, sizeof(sa)); sa.sa_handler = handler; sa.sa_flags |= SA_RESTART; sigfillset(&sa.sa_mask); if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) { event_warn("sigaction"); mm_free(sig->sh_old[evsignal]); sig->sh_old[evsignal] = NULL; return (-1); } #else if ((sh = signal(evsignal, handler)) == SIG_ERR) { event_warn("signal"); mm_free(sig->sh_old[evsignal]); sig->sh_old[evsignal] = NULL; return (-1); } *sig->sh_old[evsignal] = sh; #endif return (0); } static int evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) { struct evsig_info *sig = &base->sig; (void)p; EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); /* catch signals if they happen quickly */ EVSIGBASE_LOCK(); if (evsig_base != base && evsig_base_n_signals_added) { event_warnx("Added a signal to event base %p with signals " "already added to event_base %p. Only one can have " "signals at a time with the %s backend. The base with " "the most recently added signal or the most recent " "event_base_loop() call gets preference; do " "not rely on this behavior in future Libevent versions.", base, evsig_base, base->evsel->name); } evsig_base = base; evsig_base_n_signals_added = ++sig->ev_n_signals_added; evsig_base_fd = base->sig.ev_signal_pair[1]; EVSIGBASE_UNLOCK(); event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal)); if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) { goto err; } if (!sig->ev_signal_added) { if (event_add_nolock_(&sig->ev_signal, NULL, 0)) goto err; sig->ev_signal_added = 1; } return (0); err: EVSIGBASE_LOCK(); --evsig_base_n_signals_added; --sig->ev_n_signals_added; EVSIGBASE_UNLOCK(); return (-1); } int evsig_restore_handler_(struct event_base *base, int evsignal) { int ret = 0; struct evsig_info *sig = &base->sig; #ifdef EVENT__HAVE_SIGACTION struct sigaction *sh; #else ev_sighandler_t *sh; #endif if (evsignal >= sig->sh_old_max) { /* Can't actually restore. */ /* XXXX.*/ return 0; } /* restore previous handler */ sh = sig->sh_old[evsignal]; sig->sh_old[evsignal] = NULL; #ifdef EVENT__HAVE_SIGACTION if (sigaction(evsignal, sh, NULL) == -1) { event_warn("sigaction"); ret = -1; } #else if (signal(evsignal, *sh) == SIG_ERR) { event_warn("signal"); ret = -1; } #endif mm_free(sh); return ret; } static int evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p) { EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG); event_debug(("%s: "EV_SOCK_FMT": restoring signal handler", __func__, EV_SOCK_ARG(evsignal))); EVSIGBASE_LOCK(); --evsig_base_n_signals_added; --base->sig.ev_n_signals_added; EVSIGBASE_UNLOCK(); return (evsig_restore_handler_(base, (int)evsignal)); } static void __cdecl evsig_handler(int sig) { int save_errno = errno; #ifdef _WIN32 int socket_errno = EVUTIL_SOCKET_ERROR(); #endif ev_uint8_t msg; if (evsig_base == NULL) { event_warnx( "%s: received signal %d, but have no base configured", __func__, sig); return; } #ifndef EVENT__HAVE_SIGACTION signal(sig, evsig_handler); #endif /* Wake up our notification mechanism */ msg = sig; #ifdef _WIN32 send(evsig_base_fd, (char*)&msg, 1, 0); #else { int r = write(evsig_base_fd, (char*)&msg, 1); (void)r; /* Suppress 'unused return value' and 'unused var' */ } #endif errno = save_errno; #ifdef _WIN32 EVUTIL_SET_SOCKET_ERROR(socket_errno); #endif } void evsig_dealloc_(struct event_base *base) { int i = 0; if (base->sig.ev_signal_added) { event_del(&base->sig.ev_signal); base->sig.ev_signal_added = 0; } /* debug event is created in evsig_init_/event_assign even when * ev_signal_added == 0, so unassign is required */ event_debug_unassign(&base->sig.ev_signal); for (i = 0; i < NSIG; ++i) { if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL) evsig_restore_handler_(base, i); } EVSIGBASE_LOCK(); if (base == evsig_base) { evsig_base = NULL; evsig_base_n_signals_added = 0; evsig_base_fd = -1; } EVSIGBASE_UNLOCK(); if (base->sig.ev_signal_pair[0] != -1) { evutil_closesocket(base->sig.ev_signal_pair[0]); base->sig.ev_signal_pair[0] = -1; } if (base->sig.ev_signal_pair[1] != -1) { evutil_closesocket(base->sig.ev_signal_pair[1]); base->sig.ev_signal_pair[1] = -1; } base->sig.sh_old_max = 0; /* per index frees are handled in evsig_del() */ if (base->sig.sh_old) { mm_free(base->sig.sh_old); base->sig.sh_old = NULL; } } static void evsig_free_globals_locks(void) { #ifndef EVENT__DISABLE_THREAD_SUPPORT if (evsig_base_lock != NULL) { EVTHREAD_FREE_LOCK(evsig_base_lock, 0); evsig_base_lock = NULL; } #endif return; } void evsig_free_globals_(void) { evsig_free_globals_locks(); } #ifndef EVENT__DISABLE_THREAD_SUPPORT int evsig_global_setup_locks_(const int enable_locks) { EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0); return 0; } #endif