1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * Copyright (c) 2012, 2015 SAP SE. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 /* CopyrightVersion 1.2 */ 27 28 /* This is a special library that should be loaded before libc & 29 * libthread to interpose the signal handler installation functions: 30 * sigaction(), signal(), sigset(). 31 * Used for signal-chaining. See RFE 4381843. 32 */ 33 34 #include <signal.h> 35 #include <dlfcn.h> 36 #include <pthread.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <stdint.h> 40 41 #define bool int 42 #define true 1 43 #define false 0 44 45 static struct sigaction sact[NSIG]; /* saved signal handlers */ 46 static sigset_t jvmsigs; /* Signals used by jvm. */ 47 48 /* Used to synchronize the installation of signal handlers. */ 49 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 50 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER; 51 static pthread_t tid = 0; 52 53 typedef void (*sa_handler_t)(int); 54 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *); 55 // signal_t is already defined on AIX. 56 typedef sa_handler_t (*signal_like_function_t)(int, sa_handler_t); 57 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *); 58 59 static signal_like_function_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 if (os_signal == NULL) { 83 if (!is_sigset) { 84 // Aix: call functions directly instead of dlsym'ing them. 85 os_signal = signal; 86 } else { 87 // Aix: call functions directly instead of dlsym'ing them. 88 os_signal = sigset; 89 } 90 if (os_signal == NULL) { 91 printf("%s\n", dlerror()); 92 exit(0); 93 } 94 } 95 return (*os_signal)(sig, disp); 96 } 97 98 static void save_signal_handler(int sig, sa_handler_t disp) { 99 sigset_t set; 100 sact[sig].sa_handler = disp; 101 sigemptyset(&set); 102 sact[sig].sa_mask = set; 103 sact[sig].sa_flags = 0; 104 } 105 106 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) { 107 sa_handler_t oldhandler; 108 bool sigused; 109 110 signal_lock(); 111 112 sigused = sigismember(&jvmsigs, sig); 113 if (jvm_signal_installed && sigused) { 114 /* jvm has installed its signal handler for this signal. */ 115 /* Save the handler. Don't really install it. */ 116 oldhandler = sact[sig].sa_handler; 117 save_signal_handler(sig, disp); 118 119 signal_unlock(); 120 return oldhandler; 121 } else if (jvm_signal_installing) { 122 /* jvm is installing its signal handlers. Install the new 123 * handlers and save the old ones. jvm uses sigaction(). 124 * Leave the piece here just in case. */ 125 oldhandler = call_os_signal(sig, disp, is_sigset); 126 save_signal_handler(sig, oldhandler); 127 128 /* Record the signals used by jvm */ 129 sigaddset(&jvmsigs, sig); 130 131 signal_unlock(); 132 return oldhandler; 133 } else { 134 /* jvm has no relation with this signal (yet). Install the 135 * the handler. */ 136 oldhandler = call_os_signal(sig, disp, is_sigset); 137 138 signal_unlock(); 139 return oldhandler; 140 } 141 } 142 143 sa_handler_t signal(int sig, sa_handler_t disp) { 144 return set_signal(sig, disp, false); 145 } 146 147 sa_handler_t sigset(int sig, sa_handler_t disp) { 148 return set_signal(sig, disp, true); 149 } 150 151 static int call_os_sigaction(int sig, const struct sigaction *act, 152 struct sigaction *oact) { 153 if (os_sigaction == NULL) { 154 // Aix: call functions directly instead of dlsym'ing them. 155 os_sigaction = sigaction; 156 if (os_sigaction == NULL) { 157 printf("%s\n", dlerror()); 158 exit(0); 159 } 160 } 161 return (*os_sigaction)(sig, act, oact); 162 } 163 164 int 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 = sigismember(&jvmsigs, sig); 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 (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 sigaddset(&jvmsigs, 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. */ 209 void JVM_begin_signal_setting() { 210 signal_lock(); 211 sigemptyset(&jvmsigs); 212 jvm_signal_installing = true; 213 tid = pthread_self(); 214 signal_unlock(); 215 } 216 217 void JVM_end_signal_setting() { 218 signal_lock(); 219 jvm_signal_installed = true; 220 jvm_signal_installing = false; 221 pthread_cond_broadcast(&cond); 222 signal_unlock(); 223 } 224 225 struct sigaction *JVM_get_signal_action(int sig) { 226 /* Does race condition make sense here? */ 227 if (sigismember(&jvmsigs, sig)) { 228 return &sact[sig]; 229 } 230 return NULL; 231 }