1/* 2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25/* CopyrightVersion 1.2 */ 26 27/* This is a special library that should be loaded before libc & 28 * libthread to interpose the signal handler installation functions: 29 * sigaction(), signal(), sigset(). 30 * Used for signal-chaining. See RFE 4381843. 31 */ 32 33#include <signal.h> 34#include <dlfcn.h> 35#include <pthread.h> 36#include <stdio.h> 37#include <stdlib.h> 38#include <stdint.h> 39 40#define bool int 41#define true 1 42#define false 0 43 44#define MASK(sig) ((uint64_t)1 << (sig-1)) // 0 is not a signal. 45// Check whether all signals fit into jvmsigs. -1 as MASK shifts by -1. 46#if (64 < NSIG-1) 47#error "Not all signals can be encoded in jvmsigs. Adapt its type!" 48#endif 49static struct sigaction sact[NSIG]; /* saved signal handlers */ 50static uint64_t jvmsigs = 0; /* signals used by jvm */ 51 52/* used to synchronize the installation of signal handlers */ 53static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 54static pthread_cond_t cond = PTHREAD_COND_INITIALIZER; 55static pthread_t tid = 0; 56 57typedef void (*sa_handler_t)(int); 58typedef void (*sa_sigaction_t)(int, siginfo_t *, void *); 59typedef sa_handler_t (*signal_t)(int, sa_handler_t); 60typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *); 61 62static signal_t os_signal = 0; /* os's version of signal()/sigset() */ 63static sigaction_t os_sigaction = 0; /* os's version of sigaction() */ 64 65static bool jvm_signal_installing = false; 66static bool jvm_signal_installed = false; 67 68static void signal_lock() { 69 pthread_mutex_lock(&mutex); 70 /* When the jvm is installing its set of signal handlers, threads 71 * other than the jvm thread should wait */ 72 if (jvm_signal_installing) { 73 if (tid != pthread_self()) { 74 pthread_cond_wait(&cond, &mutex); 75 } 76 } 77} 78 79static void signal_unlock() { 80 pthread_mutex_unlock(&mutex); 81} 82 83static sa_handler_t call_os_signal(int sig, sa_handler_t disp, 84 bool is_sigset) { 85 if (os_signal == NULL) { 86 if (!is_sigset) { 87 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal"); 88 } else { 89 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset"); 90 } 91 if (os_signal == NULL) { 92 printf("%s\n", dlerror()); 93 exit(0); 94 } 95 } 96 return (*os_signal)(sig, disp); 97} 98 99static void save_signal_handler(int sig, sa_handler_t disp) { 100 sigset_t set; 101 sact[sig].sa_handler = disp; 102 sigemptyset(&set); 103 sact[sig].sa_mask = set; 104 sact[sig].sa_flags = 0; 105} 106 107static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) { 108 sa_handler_t oldhandler; 109 bool sigused; 110 111 signal_lock(); 112 113 sigused = (sig < NSIG) && ((MASK(sig) & jvmsigs) != 0); 114 if (jvm_signal_installed && sigused) { 115 /* jvm has installed its signal handler for this signal. */ 116 /* Save the handler. Don't really install it. */ 117 oldhandler = sact[sig].sa_handler; 118 save_signal_handler(sig, disp); 119 120 signal_unlock(); 121 return oldhandler; 122 } else if (sig < NSIG && jvm_signal_installing) { 123 /* jvm is installing its signal handlers. Install the new 124 * handlers and save the old ones. jvm uses sigaction(). 125 * Leave the piece here just in case. */ 126 oldhandler = call_os_signal(sig, disp, is_sigset); 127 save_signal_handler(sig, oldhandler); 128 129 /* Record the signals used by jvm */ 130 jvmsigs |= MASK(sig); 131 132 signal_unlock(); 133 return oldhandler; 134 } else { 135 /* jvm has no relation with this signal (yet). Install the 136 * the handler. */ 137 oldhandler = call_os_signal(sig, disp, is_sigset); 138 139 signal_unlock(); 140 return oldhandler; 141 } 142} 143 144sa_handler_t signal(int sig, sa_handler_t disp) { 145 return set_signal(sig, disp, false); 146} 147 148sa_handler_t sigset(int sig, sa_handler_t disp) { 149 return set_signal(sig, disp, true); 150 } 151 152static int call_os_sigaction(int sig, const struct sigaction *act, 153 struct sigaction *oact) { 154 if (os_sigaction == NULL) { 155 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction"); 156 if (os_sigaction == NULL) { 157 printf("%s\n", dlerror()); 158 exit(0); 159 } 160 } 161 return (*os_sigaction)(sig, act, oact); 162} 163 164int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) { 165 int res; 166 bool sigused; 167 struct sigaction oldAct; 168 169 signal_lock(); 170 171 sigused = (sig < NSIG) && ((MASK(sig) & jvmsigs) != 0); 172 if (jvm_signal_installed && sigused) { 173 /* jvm has installed its signal handler for this signal. */ 174 /* Save the handler. Don't really install it. */ 175 if (oact != NULL) { 176 *oact = sact[sig]; 177 } 178 if (act != NULL) { 179 sact[sig] = *act; 180 } 181 182 signal_unlock(); 183 return 0; 184 } else if (sig < NSIG && jvm_signal_installing) { 185 /* jvm is installing its signal handlers. Install the new 186 * handlers and save the old ones. */ 187 res = call_os_sigaction(sig, act, &oldAct); 188 sact[sig] = oldAct; 189 if (oact != NULL) { 190 *oact = oldAct; 191 } 192 193 /* Record the signals used by jvm */ 194 jvmsigs |= MASK(sig); 195 196 signal_unlock(); 197 return res; 198 } else { 199 /* jvm has no relation with this signal (yet). Install the 200 * the handler. */ 201 res = call_os_sigaction(sig, act, oact); 202 203 signal_unlock(); 204 return res; 205 } 206} 207 208/* The three functions for the jvm to call into */ 209void JVM_begin_signal_setting() { 210 signal_lock(); 211 jvm_signal_installing = true; 212 tid = pthread_self(); 213 signal_unlock(); 214} 215 216void JVM_end_signal_setting() { 217 signal_lock(); 218 jvm_signal_installed = true; 219 jvm_signal_installing = false; 220 pthread_cond_broadcast(&cond); 221 signal_unlock(); 222} 223 224struct sigaction *JVM_get_signal_action(int sig) { 225 /* Does race condition make sense here? */ 226 if ((MASK(sig) & jvmsigs) != 0) { 227 return &sact[sig]; 228 } 229 return NULL; 230} 231