| /* |
| * Copyright (c) 2001, 2015, 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> |
| #include <stdint.h> |
| |
| #define MASK(sig) ((uint32_t)1 << (sig-1)) // 0 is not a signal. |
| #if (32 < NSIG-1) |
| #error "Not all signals can be encoded in jvmsigs. Adapt its type!" |
| #endif |
| static struct sigaction sact[NSIG]; /* saved signal handlers */ |
| static uint32_t jvmsigs = 0; /* signals used by jvm */ |
| static __thread bool reentry = false; /* prevent reentry deadlock (per-thread) */ |
| |
| /* 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) { |
| sa_handler_t res; |
| |
| 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); |
| } |
| } |
| reentry = true; |
| res = (*os_signal)(sig, disp); |
| reentry = false; |
| return res; |
| } |
| |
| 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; |
| |
| if (reentry) { |
| return call_os_sigaction(sig, act, oact); |
| } |
| |
| 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; |
| } |