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3960
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1 /*
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2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 *
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23 */
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24
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25 /* CopyrightVersion 1.2 */
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26
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27 /* This is a special library that should be loaded before libc &
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28 * libthread to interpose the signal handler installation functions:
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29 * sigaction(), signal(), sigset().
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30 * Used for signal-chaining. See RFE 4381843.
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31 */
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32
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33 #include <signal.h>
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34 #include <dlfcn.h>
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35 #include <pthread.h>
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36 #include <stdio.h>
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37 #include <stdlib.h>
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38 #include <stdbool.h>
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39
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40 #define MAXSIGNUM 32
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41 #define MASK(sig) ((unsigned int)1 << sig)
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42
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43 static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
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44 static unsigned int jvmsigs = 0; /* signals used by jvm */
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45
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46 /* used to synchronize the installation of signal handlers */
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47 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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48 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
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49 static pthread_t tid = 0;
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50
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51 typedef void (*sa_handler_t)(int);
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52 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
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53 typedef sa_handler_t (*signal_t)(int, sa_handler_t);
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54 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
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55
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56 static signal_t os_signal = 0; /* os's version of signal()/sigset() */
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57 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
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58
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59 static bool jvm_signal_installing = false;
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60 static bool jvm_signal_installed = false;
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61
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62 static void signal_lock() {
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63 pthread_mutex_lock(&mutex);
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64 /* When the jvm is installing its set of signal handlers, threads
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65 * other than the jvm thread should wait */
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66 if (jvm_signal_installing) {
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67 if (tid != pthread_self()) {
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68 pthread_cond_wait(&cond, &mutex);
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69 }
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70 }
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71 }
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72
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73 static void signal_unlock() {
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74 pthread_mutex_unlock(&mutex);
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75 }
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76
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77 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
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78 bool is_sigset) {
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79 if (os_signal == NULL) {
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80 if (!is_sigset) {
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81 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
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82 } else {
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83 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
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84 }
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85 if (os_signal == NULL) {
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86 printf("%s\n", dlerror());
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87 exit(0);
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88 }
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89 }
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90 return (*os_signal)(sig, disp);
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91 }
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92
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93 static void save_signal_handler(int sig, sa_handler_t disp) {
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94 sigset_t set;
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95 sact[sig].sa_handler = disp;
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96 sigemptyset(&set);
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97 sact[sig].sa_mask = set;
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98 sact[sig].sa_flags = 0;
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99 }
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100
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101 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
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102 sa_handler_t oldhandler;
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103 bool sigused;
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104
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105 signal_lock();
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106
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107 sigused = (MASK(sig) & jvmsigs) != 0;
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108 if (jvm_signal_installed && sigused) {
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109 /* jvm has installed its signal handler for this signal. */
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110 /* Save the handler. Don't really install it. */
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111 oldhandler = sact[sig].sa_handler;
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112 save_signal_handler(sig, disp);
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113
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114 signal_unlock();
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115 return oldhandler;
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116 } else if (jvm_signal_installing) {
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117 /* jvm is installing its signal handlers. Install the new
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118 * handlers and save the old ones. jvm uses sigaction().
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119 * Leave the piece here just in case. */
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120 oldhandler = call_os_signal(sig, disp, is_sigset);
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121 save_signal_handler(sig, oldhandler);
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122
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123 /* Record the signals used by jvm */
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124 jvmsigs |= MASK(sig);
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125
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126 signal_unlock();
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127 return oldhandler;
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128 } else {
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129 /* jvm has no relation with this signal (yet). Install the
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130 * the handler. */
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131 oldhandler = call_os_signal(sig, disp, is_sigset);
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132
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133 signal_unlock();
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134 return oldhandler;
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135 }
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136 }
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137
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138 sa_handler_t signal(int sig, sa_handler_t disp) {
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139 return set_signal(sig, disp, false);
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140 }
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141
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142 sa_handler_t sigset(int sig, sa_handler_t disp) {
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143 printf("sigset() is not supported by BSD");
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144 exit(0);
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145 }
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146
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147 static int call_os_sigaction(int sig, const struct sigaction *act,
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148 struct sigaction *oact) {
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149 if (os_sigaction == NULL) {
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150 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
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151 if (os_sigaction == NULL) {
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152 printf("%s\n", dlerror());
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153 exit(0);
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154 }
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155 }
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156 return (*os_sigaction)(sig, act, oact);
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157 }
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158
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159 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
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160 int res;
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161 bool sigused;
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162 struct sigaction oldAct;
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163
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164 signal_lock();
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165
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166 sigused = (MASK(sig) & jvmsigs) != 0;
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167 if (jvm_signal_installed && sigused) {
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168 /* jvm has installed its signal handler for this signal. */
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169 /* Save the handler. Don't really install it. */
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170 if (oact != NULL) {
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171 *oact = sact[sig];
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172 }
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173 if (act != NULL) {
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174 sact[sig] = *act;
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175 }
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176
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177 signal_unlock();
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178 return 0;
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179 } else if (jvm_signal_installing) {
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180 /* jvm is installing its signal handlers. Install the new
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181 * handlers and save the old ones. */
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182 res = call_os_sigaction(sig, act, &oldAct);
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183 sact[sig] = oldAct;
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184 if (oact != NULL) {
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185 *oact = oldAct;
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186 }
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187
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188 /* Record the signals used by jvm */
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189 jvmsigs |= MASK(sig);
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190
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191 signal_unlock();
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192 return res;
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193 } else {
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194 /* jvm has no relation with this signal (yet). Install the
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195 * the handler. */
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196 res = call_os_sigaction(sig, act, oact);
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197
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198 signal_unlock();
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199 return res;
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200 }
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201 }
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202
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203 /* The three functions for the jvm to call into */
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204 void JVM_begin_signal_setting() {
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205 signal_lock();
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206 jvm_signal_installing = true;
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207 tid = pthread_self();
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208 signal_unlock();
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209 }
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210
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211 void JVM_end_signal_setting() {
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212 signal_lock();
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213 jvm_signal_installed = true;
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214 jvm_signal_installing = false;
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215 pthread_cond_broadcast(&cond);
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216 signal_unlock();
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217 }
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218
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219 struct sigaction *JVM_get_signal_action(int sig) {
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220 /* Does race condition make sense here? */
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221 if ((MASK(sig) & jvmsigs) != 0) {
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222 return &sact[sig];
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223 }
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224 return NULL;
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225 }
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