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/*
* Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
/* CopyrightVersion 1.2 */
/* This is a special library that should be loaded before libc &
* libthread to interpose the signal handler installation functions:
* sigaction(), signal(), sigset().
* Used for signal-chaining. See RFE 4381843.
*/
#include <signal.h>
#include <dlfcn.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#define MAXSIGNUM 32
#define MASK(sig) ((unsigned int)1 << sig)
static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
static unsigned int jvmsigs = 0; /* signals used by jvm */
/* used to synchronize the installation of signal handlers */
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
static pthread_t tid = 0;
typedef void (*sa_handler_t)(int);
typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
typedef sa_handler_t (*signal_t)(int, sa_handler_t);
typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
static signal_t os_signal = 0; /* os's version of signal()/sigset() */
static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
static bool jvm_signal_installing = false;
static bool jvm_signal_installed = false;
static void signal_lock() {
pthread_mutex_lock(&mutex);
/* When the jvm is installing its set of signal handlers, threads
* other than the jvm thread should wait */
if (jvm_signal_installing) {
if (tid != pthread_self()) {
pthread_cond_wait(&cond, &mutex);
}
}
}
static void signal_unlock() {
pthread_mutex_unlock(&mutex);
}
static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
bool is_sigset) {
if (os_signal == NULL) {
if (!is_sigset) {
os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
} else {
os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
}
if (os_signal == NULL) {
printf("%s\n", dlerror());
exit(0);
}
}
return (*os_signal)(sig, disp);
}
static void save_signal_handler(int sig, sa_handler_t disp) {
sigset_t set;
sact[sig].sa_handler = disp;
sigemptyset(&set);
sact[sig].sa_mask = set;
sact[sig].sa_flags = 0;
}
static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
sa_handler_t oldhandler;
bool sigused;
signal_lock();
sigused = (MASK(sig) & jvmsigs) != 0;
if (jvm_signal_installed && sigused) {
/* jvm has installed its signal handler for this signal. */
/* Save the handler. Don't really install it. */
oldhandler = sact[sig].sa_handler;
save_signal_handler(sig, disp);
signal_unlock();
return oldhandler;
} else if (jvm_signal_installing) {
/* jvm is installing its signal handlers. Install the new
* handlers and save the old ones. jvm uses sigaction().
* Leave the piece here just in case. */
oldhandler = call_os_signal(sig, disp, is_sigset);
save_signal_handler(sig, oldhandler);
/* Record the signals used by jvm */
jvmsigs |= MASK(sig);
signal_unlock();
return oldhandler;
} else {
/* jvm has no relation with this signal (yet). Install the
* the handler. */
oldhandler = call_os_signal(sig, disp, is_sigset);
signal_unlock();
return oldhandler;
}
}
sa_handler_t signal(int sig, sa_handler_t disp) {
return set_signal(sig, disp, false);
}
sa_handler_t sigset(int sig, sa_handler_t disp) {
printf("sigset() is not supported by BSD");
exit(0);
}
static int call_os_sigaction(int sig, const struct sigaction *act,
struct sigaction *oact) {
if (os_sigaction == NULL) {
os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
if (os_sigaction == NULL) {
printf("%s\n", dlerror());
exit(0);
}
}
return (*os_sigaction)(sig, act, oact);
}
int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
int res;
bool sigused;
struct sigaction oldAct;
signal_lock();
sigused = (MASK(sig) & jvmsigs) != 0;
if (jvm_signal_installed && sigused) {
/* jvm has installed its signal handler for this signal. */
/* Save the handler. Don't really install it. */
if (oact != NULL) {
*oact = sact[sig];
}
if (act != NULL) {
sact[sig] = *act;
}
signal_unlock();
return 0;
} else if (jvm_signal_installing) {
/* jvm is installing its signal handlers. Install the new
* handlers and save the old ones. */
res = call_os_sigaction(sig, act, &oldAct);
sact[sig] = oldAct;
if (oact != NULL) {
*oact = oldAct;
}
/* Record the signals used by jvm */
jvmsigs |= MASK(sig);
signal_unlock();
return res;
} else {
/* jvm has no relation with this signal (yet). Install the
* the handler. */
res = call_os_sigaction(sig, act, oact);
signal_unlock();
return res;
}
}
/* The three functions for the jvm to call into */
void JVM_begin_signal_setting() {
signal_lock();
jvm_signal_installing = true;
tid = pthread_self();
signal_unlock();
}
void JVM_end_signal_setting() {
signal_lock();
jvm_signal_installed = true;
jvm_signal_installing = false;
pthread_cond_broadcast(&cond);
signal_unlock();
}
struct sigaction *JVM_get_signal_action(int sig) {
/* Does race condition make sense here? */
if ((MASK(sig) & jvmsigs) != 0) {
return &sact[sig];
}
return NULL;
}
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