1 /* 2 * Copyright (c) 2001, 2015, 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 <stdbool.h> 39 #include <stdint.h> 40 41 #define MASK(sig) ((uint32_t)1 << (sig-1)) // 0 is not a signal. 42 #if (32 < NSIG-1) 43 #error "Not all signals can be encoded in jvmsigs. Adapt its type!" 44 #endif 45 static struct sigaction sact[NSIG]; /* saved signal handlers */ 46 static uint32_t jvmsigs = 0; /* signals used by jvm */ 47 static __thread bool reentry = false; /* prevent reentry deadlock (per-thread) */ 48 49 /* used to synchronize the installation of signal handlers */ 50 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 51 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER; 52 static pthread_t tid = 0; 53 54 typedef void (*sa_handler_t)(int); 55 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *); 56 typedef sa_handler_t (*signal_t)(int, sa_handler_t); 57 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *); 58 59 static signal_t os_signal = 0; /* os's version of signal()/sigset() */ 60 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */ 61 62 static bool jvm_signal_installing = false; 63 static bool jvm_signal_installed = false; 64 65 static 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 76 static void signal_unlock() { 77 pthread_mutex_unlock(&mutex); 78 } 79 80 static sa_handler_t call_os_signal(int sig, sa_handler_t disp, 81 bool is_sigset) { 82 sa_handler_t res; 83 84 if (os_signal == NULL) { 85 if (!is_sigset) { 86 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal"); 87 } else { 88 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset"); 89 } 90 if (os_signal == NULL) { 91 printf("%s\n", dlerror()); 92 exit(0); 93 } 94 } 95 reentry = true; 96 res = (*os_signal)(sig, disp); 97 reentry = false; 98 return res; 99 } 100 101 static void save_signal_handler(int sig, sa_handler_t disp) { 102 sigset_t set; 103 sact[sig].sa_handler = disp; 104 sigemptyset(&set); 105 sact[sig].sa_mask = set; 106 sact[sig].sa_flags = 0; 107 } 108 109 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) { 110 sa_handler_t oldhandler; 111 bool sigused; 112 113 signal_lock(); 114 115 sigused = (MASK(sig) & jvmsigs) != 0; 116 if (jvm_signal_installed && sigused) { 117 /* jvm has installed its signal handler for this signal. */ 118 /* Save the handler. Don't really install it. */ 119 oldhandler = sact[sig].sa_handler; 120 save_signal_handler(sig, disp); 121 122 signal_unlock(); 123 return oldhandler; 124 } else if (jvm_signal_installing) { 125 /* jvm is installing its signal handlers. Install the new 126 * handlers and save the old ones. jvm uses sigaction(). 127 * Leave the piece here just in case. */ 128 oldhandler = call_os_signal(sig, disp, is_sigset); 129 save_signal_handler(sig, oldhandler); 130 131 /* Record the signals used by jvm */ 132 jvmsigs |= MASK(sig); 133 134 signal_unlock(); 135 return oldhandler; 136 } else { 137 /* jvm has no relation with this signal (yet). Install the 138 * the handler. */ 139 oldhandler = call_os_signal(sig, disp, is_sigset); 140 141 signal_unlock(); 142 return oldhandler; 143 } 144 } 145 146 sa_handler_t signal(int sig, sa_handler_t disp) { 147 return set_signal(sig, disp, false); 148 } 149 150 sa_handler_t sigset(int sig, sa_handler_t disp) { 151 printf("sigset() is not supported by BSD"); 152 exit(0); 153 } 154 155 static int call_os_sigaction(int sig, const struct sigaction *act, 156 struct sigaction *oact) { 157 if (os_sigaction == NULL) { 158 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction"); 159 if (os_sigaction == NULL) { 160 printf("%s\n", dlerror()); 161 exit(0); 162 } 163 } 164 return (*os_sigaction)(sig, act, oact); 165 } 166 167 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) { 168 int res; 169 bool sigused; 170 struct sigaction oldAct; 171 172 if (reentry) { 173 return call_os_sigaction(sig, act, oact); 174 } 175 176 signal_lock(); 177 178 sigused = (MASK(sig) & jvmsigs) != 0; 179 if (jvm_signal_installed && sigused) { 180 /* jvm has installed its signal handler for this signal. */ 181 /* Save the handler. Don't really install it. */ 182 if (oact != NULL) { 183 *oact = sact[sig]; 184 } 185 if (act != NULL) { 186 sact[sig] = *act; 187 } 188 189 signal_unlock(); 190 return 0; 191 } else if (jvm_signal_installing) { 192 /* jvm is installing its signal handlers. Install the new 193 * handlers and save the old ones. */ 194 res = call_os_sigaction(sig, act, &oldAct); 195 sact[sig] = oldAct; 196 if (oact != NULL) { 197 *oact = oldAct; 198 } 199 200 /* Record the signals used by jvm */ 201 jvmsigs |= MASK(sig); 202 203 signal_unlock(); 204 return res; 205 } else { 206 /* jvm has no relation with this signal (yet). Install the 207 * the handler. */ 208 res = call_os_sigaction(sig, act, oact); 209 210 signal_unlock(); 211 return res; 212 } 213 } 214 215 /* The three functions for the jvm to call into */ 216 void JVM_begin_signal_setting() { 217 signal_lock(); 218 jvm_signal_installing = true; 219 tid = pthread_self(); 220 signal_unlock(); 221 } 222 223 void JVM_end_signal_setting() { 224 signal_lock(); 225 jvm_signal_installed = true; 226 jvm_signal_installing = false; 227 pthread_cond_broadcast(&cond); 228 signal_unlock(); 229 } 230 231 struct sigaction *JVM_get_signal_action(int sig) { 232 /* Does race condition make sense here? */ 233 if ((MASK(sig) & jvmsigs) != 0) { 234 return &sact[sig]; 235 } 236 return NULL; 237 }