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1 /*
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2 * Copyright 2001-2003 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any 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 <stdlib.h>
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34 #include <stdio.h>
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35 #include <string.h>
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36 #include <signal.h>
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37 #include <dlfcn.h>
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38 #include <thread.h>
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39 #include <synch.h>
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40 #include "jvm_solaris.h"
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41
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42 #define bool int
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43 #define true 1
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44 #define false 0
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45
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46 static struct sigaction *sact = (struct sigaction *)NULL; /* saved signal handlers */
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47 static sigset_t jvmsigs;
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48
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49 /* used to synchronize the installation of signal handlers */
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50 static mutex_t mutex = DEFAULTMUTEX;
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51 static cond_t cond = DEFAULTCV;
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52 static thread_t tid = 0;
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53
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54 typedef void (*sa_handler_t)(int);
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55 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
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56 typedef sa_handler_t (*signal_t)(int, sa_handler_t);
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57 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
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58
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59 static signal_t os_signal = 0; /* os's version of signal()/sigset() */
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60 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
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61
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62 static bool jvm_signal_installing = false;
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63 static bool jvm_signal_installed = false;
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64
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65
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66 /* assume called within signal_lock */
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67 static void allocate_sact() {
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68 size_t maxsignum;
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69 maxsignum = SIGRTMAX;
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70 if (sact == NULL) {
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71 sact = (struct sigaction *)malloc((maxsignum+1) * (size_t)sizeof(struct sigaction));
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72 memset(sact, 0, (maxsignum+1) * (size_t)sizeof(struct sigaction));
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73 }
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74
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75 if (sact == NULL) {
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76 printf("%s\n", "libjsig.so unable to allocate memory");
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77 exit(0);
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78 }
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79
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80 sigemptyset(&jvmsigs);
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81 }
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82
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83 static void signal_lock() {
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84 mutex_lock(&mutex);
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85 /* When the jvm is installing its set of signal handlers, threads
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86 * other than the jvm thread should wait */
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87 if (jvm_signal_installing) {
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88 if (tid != thr_self()) {
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89 cond_wait(&cond, &mutex);
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90 }
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91 }
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92 }
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93
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94 static void signal_unlock() {
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95 mutex_unlock(&mutex);
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96 }
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97
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98 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
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99 bool is_sigset) {
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100 if (os_signal == NULL) {
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101 if (!is_sigset) {
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102 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
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103 } else {
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104 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
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105 }
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106 if (os_signal == NULL) {
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107 printf("%s\n", dlerror());
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108 exit(0);
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109 }
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110 }
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111 return (*os_signal)(sig, disp);
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112 }
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113
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114 static void save_signal_handler(int sig, sa_handler_t disp, bool is_sigset) {
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115 sigset_t set;
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116 if (sact == NULL) {
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117 allocate_sact();
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118 }
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119 sact[sig].sa_handler = disp;
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120 sigemptyset(&set);
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121 sact[sig].sa_mask = set;
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122 if (!is_sigset) {
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123 sact[sig].sa_flags = SA_NODEFER;
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124 if (sig != SIGILL && sig != SIGTRAP && sig != SIGPWR) {
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125 sact[sig].sa_flags |= SA_RESETHAND;
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126 }
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127 } else {
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128 sact[sig].sa_flags = 0;
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129 }
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130 }
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131
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132 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
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133 sa_handler_t oldhandler;
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134 bool sigblocked;
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135
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136 signal_lock();
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137 if (sact == NULL) {
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138 allocate_sact();
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139 }
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140
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141 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
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142 /* jvm has installed its signal handler for this signal. */
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143 /* Save the handler. Don't really install it. */
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144 if (is_sigset) {
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145 /* We won't honor the SIG_HOLD request to change the signal mask */
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146 sigblocked = sigismember(&(sact[sig].sa_mask), sig);
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147 }
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148 oldhandler = sact[sig].sa_handler;
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149 save_signal_handler(sig, disp, is_sigset);
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150
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151 if (is_sigset && sigblocked) {
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152 oldhandler = SIG_HOLD;
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153 }
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154
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155 signal_unlock();
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156 return oldhandler;
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157 } else if (jvm_signal_installing) {
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158 /* jvm is installing its signal handlers. Install the new
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159 * handlers and save the old ones. jvm uses sigaction().
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160 * Leave the piece here just in case. */
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161 oldhandler = call_os_signal(sig, disp, is_sigset);
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162 save_signal_handler(sig, oldhandler, is_sigset);
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163
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164 /* Record the signals used by jvm */
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165 sigaddset(&jvmsigs, sig);
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166
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167 signal_unlock();
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168 return oldhandler;
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169 } else {
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170 /* jvm has no relation with this signal (yet). Install the
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171 * the handler. */
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172 oldhandler = call_os_signal(sig, disp, is_sigset);
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173
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174 signal_unlock();
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175 return oldhandler;
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176 }
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177 }
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178
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179 sa_handler_t signal(int sig, sa_handler_t disp) {
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180 return set_signal(sig, disp, false);
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181 }
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182
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183 sa_handler_t sigset(int sig, sa_handler_t disp) {
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184 return set_signal(sig, disp, true);
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185 }
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186
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187 static int call_os_sigaction(int sig, const struct sigaction *act,
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188 struct sigaction *oact) {
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189 if (os_sigaction == NULL) {
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190 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
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191 if (os_sigaction == NULL) {
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192 printf("%s\n", dlerror());
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193 exit(0);
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194 }
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195 }
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196 return (*os_sigaction)(sig, act, oact);
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197 }
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198
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199 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
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200 int res;
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201 struct sigaction oldAct;
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202
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203 signal_lock();
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204
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205 if (sact == NULL ) {
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206 allocate_sact();
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207 }
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208 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
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209 /* jvm has installed its signal handler for this signal. */
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210 /* Save the handler. Don't really install it. */
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211 if (oact != NULL) {
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212 *oact = sact[sig];
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213 }
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214 if (act != NULL) {
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215 sact[sig] = *act;
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216 }
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217
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218 signal_unlock();
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219 return 0;
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220 } else if (jvm_signal_installing) {
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221 /* jvm is installing its signal handlers. Install the new
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222 * handlers and save the old ones. */
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223 res = call_os_sigaction(sig, act, &oldAct);
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224 sact[sig] = oldAct;
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225 if (oact != NULL) {
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226 *oact = oldAct;
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227 }
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228
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229 /* Record the signals used by jvm */
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230 sigaddset(&jvmsigs, sig);
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231
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232 signal_unlock();
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233 return res;
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234 } else {
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235 /* jvm has no relation with this signal (yet). Install the
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236 * the handler. */
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237 res = call_os_sigaction(sig, act, oact);
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238
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239 signal_unlock();
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240 return res;
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241 }
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242 }
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243
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244 /* The four functions for the jvm to call into */
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245 void JVM_begin_signal_setting() {
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246 signal_lock();
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247 jvm_signal_installing = true;
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248 tid = thr_self();
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249 signal_unlock();
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250 }
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251
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252 void JVM_end_signal_setting() {
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253 signal_lock();
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254 jvm_signal_installed = true;
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255 jvm_signal_installing = false;
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256 cond_broadcast(&cond);
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257 signal_unlock();
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258 }
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259
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260 struct sigaction *JVM_get_signal_action(int sig) {
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261 if (sact == NULL) {
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262 allocate_sact();
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263 }
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264 /* Does race condition make sense here? */
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265 if (sigismember(&jvmsigs, sig)) {
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266 return &sact[sig];
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267 }
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268 return NULL;
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269 }
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270
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271 int JVM_get_libjsig_version() {
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272 return JSIG_VERSION_1_4_1;
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273 }
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