jsig.c revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 2001, 2006, 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 39#define bool int 40#define true 1 41#define false 0 42 43#define MAXSIGNUM 32 44#define MASK(sig) ((unsigned int)1 << sig) 45 46static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */ 47static unsigned int jvmsigs = 0; /* signals used by jvm */ 48 49/* used to synchronize the installation of signal handlers */ 50static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 51static pthread_cond_t cond = PTHREAD_COND_INITIALIZER; 52static pthread_t tid = 0; 53 54typedef void (*sa_handler_t)(int); 55typedef void (*sa_sigaction_t)(int, siginfo_t *, void *); 56typedef sa_handler_t (*signal_t)(int, sa_handler_t); 57typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *); 58 59static signal_t os_signal = 0; /* os's version of signal()/sigset() */ 60static sigaction_t os_sigaction = 0; /* os's version of sigaction() */ 61 62static bool jvm_signal_installing = false; 63static bool jvm_signal_installed = false; 64 65static void signal_lock() { 66 pthread_mutex_lock(&mutex); 67 /* When the jvm is installing its set of signal handlers, threads 68 * other than the jvm thread should wait */ 69 if (jvm_signal_installing) { 70 if (tid != pthread_self()) { 71 pthread_cond_wait(&cond, &mutex); 72 } 73 } 74} 75 76static void signal_unlock() { 77 pthread_mutex_unlock(&mutex); 78} 79 80static sa_handler_t call_os_signal(int sig, sa_handler_t disp, 81 bool is_sigset) { 82 if (os_signal == NULL) { 83 if (!is_sigset) { 84 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal"); 85 } else { 86 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset"); 87 } 88 if (os_signal == NULL) { 89 printf("%s\n", dlerror()); 90 exit(0); 91 } 92 } 93 return (*os_signal)(sig, disp); 94} 95 96static void save_signal_handler(int sig, sa_handler_t disp) { 97 sigset_t set; 98 sact[sig].sa_handler = disp; 99 sigemptyset(&set); 100 sact[sig].sa_mask = set; 101 sact[sig].sa_flags = 0; 102} 103 104static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) { 105 sa_handler_t oldhandler; 106 bool sigused; 107 108 signal_lock(); 109 110 sigused = (MASK(sig) & jvmsigs) != 0; 111 if (jvm_signal_installed && sigused) { 112 /* jvm has installed its signal handler for this signal. */ 113 /* Save the handler. Don't really install it. */ 114 oldhandler = sact[sig].sa_handler; 115 save_signal_handler(sig, disp); 116 117 signal_unlock(); 118 return oldhandler; 119 } else if (jvm_signal_installing) { 120 /* jvm is installing its signal handlers. Install the new 121 * handlers and save the old ones. jvm uses sigaction(). 122 * Leave the piece here just in case. */ 123 oldhandler = call_os_signal(sig, disp, is_sigset); 124 save_signal_handler(sig, oldhandler); 125 126 /* Record the signals used by jvm */ 127 jvmsigs |= MASK(sig); 128 129 signal_unlock(); 130 return oldhandler; 131 } else { 132 /* jvm has no relation with this signal (yet). Install the 133 * the handler. */ 134 oldhandler = call_os_signal(sig, disp, is_sigset); 135 136 signal_unlock(); 137 return oldhandler; 138 } 139} 140 141sa_handler_t signal(int sig, sa_handler_t disp) { 142 return set_signal(sig, disp, false); 143} 144 145sa_handler_t sigset(int sig, sa_handler_t disp) { 146 return set_signal(sig, disp, true); 147 } 148 149static int call_os_sigaction(int sig, const struct sigaction *act, 150 struct sigaction *oact) { 151 if (os_sigaction == NULL) { 152 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction"); 153 if (os_sigaction == NULL) { 154 printf("%s\n", dlerror()); 155 exit(0); 156 } 157 } 158 return (*os_sigaction)(sig, act, oact); 159} 160 161int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) { 162 int res; 163 bool sigused; 164 struct sigaction oldAct; 165 166 signal_lock(); 167 168 sigused = (MASK(sig) & jvmsigs) != 0; 169 if (jvm_signal_installed && sigused) { 170 /* jvm has installed its signal handler for this signal. */ 171 /* Save the handler. Don't really install it. */ 172 if (oact != NULL) { 173 *oact = sact[sig]; 174 } 175 if (act != NULL) { 176 sact[sig] = *act; 177 } 178 179 signal_unlock(); 180 return 0; 181 } else if (jvm_signal_installing) { 182 /* jvm is installing its signal handlers. Install the new 183 * handlers and save the old ones. */ 184 res = call_os_sigaction(sig, act, &oldAct); 185 sact[sig] = oldAct; 186 if (oact != NULL) { 187 *oact = oldAct; 188 } 189 190 /* Record the signals used by jvm */ 191 jvmsigs |= MASK(sig); 192 193 signal_unlock(); 194 return res; 195 } else { 196 /* jvm has no relation with this signal (yet). Install the 197 * the handler. */ 198 res = call_os_sigaction(sig, act, oact); 199 200 signal_unlock(); 201 return res; 202 } 203} 204 205/* The three functions for the jvm to call into */ 206void JVM_begin_signal_setting() { 207 signal_lock(); 208 jvm_signal_installing = true; 209 tid = pthread_self(); 210 signal_unlock(); 211} 212 213void JVM_end_signal_setting() { 214 signal_lock(); 215 jvm_signal_installed = true; 216 jvm_signal_installing = false; 217 pthread_cond_broadcast(&cond); 218 signal_unlock(); 219} 220 221struct sigaction *JVM_get_signal_action(int sig) { 222 /* Does race condition make sense here? */ 223 if ((MASK(sig) & jvmsigs) != 0) { 224 return &sact[sig]; 225 } 226 return NULL; 227} 228