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