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/* $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $ */

/*
* Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
* 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 "evconfig-private.h"

#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#endif
#include <sys/types.h>
#ifdef EVENT__HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#include <sys/queue.h>
#ifdef EVENT__HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef EVENT__HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <errno.h>
#ifdef EVENT__HAVE_FCNTL_H
#include <fcntl.h>
#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. */
#define __cdecl
#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
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