1 /*
   2  * Copyright (c) 2001, 2010, 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 <stdlib.h>
  34 #include <stdio.h>
  35 #include <string.h>
  36 #include <signal.h>
  37 #include <dlfcn.h>
  38 #include <thread.h>
  39 #include <synch.h>
  40 #include "jvm_md.h"
  41 
  42 #define bool int
  43 #define true 1
  44 #define false 0
  45 
  46 static struct sigaction *sact = (struct sigaction *)NULL; /* saved signal handlers */
  47 static sigset_t jvmsigs;




















  48 
  49 /* used to synchronize the installation of signal handlers */

  50 static mutex_t mutex = DEFAULTMUTEX;
  51 static cond_t cond = DEFAULTCV;
  52 static thread_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 
  66 /* assume called within signal_lock */
  67 static void allocate_sact() {
  68   size_t maxsignum;
  69   maxsignum = SIGRTMAX;
  70   if (sact == NULL) {
  71     sact = (struct sigaction *)malloc((maxsignum+1) * (size_t)sizeof(struct sigaction));
  72     memset(sact, 0, (maxsignum+1) * (size_t)sizeof(struct sigaction));
  73   }
  74 
  75   if (sact == NULL) {
  76     printf("%s\n", "libjsig.so unable to allocate memory");
  77     exit(0);
  78   }
  79 
  80   sigemptyset(&jvmsigs);
  81 }
  82 
  83 static void signal_lock() {

  84   mutex_lock(&mutex);



  85   /* When the jvm is installing its set of signal handlers, threads
  86    * other than the jvm thread should wait */
  87   if (jvm_signal_installing) {

  88     if (tid != thr_self()) {
  89       cond_wait(&cond, &mutex);
  90     }





  91   }
  92 }
  93 
  94 static void signal_unlock() {

  95   mutex_unlock(&mutex);



  96 }
  97 
  98 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
  99                                    bool is_sigset) {


 100   if (os_signal == NULL) {
 101     if (!is_sigset) {
 102       os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");




 103     } else {
 104       os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");




 105     }
 106     if (os_signal == NULL) {
 107       printf("%s\n", dlerror());
 108       exit(0);
 109     }
 110   }
 111   return (*os_signal)(sig, disp);





 112 }
 113 
 114 static void save_signal_handler(int sig, sa_handler_t disp, bool is_sigset) {
 115   sigset_t set;
 116   if (sact == NULL) {
 117     allocate_sact();
 118   }
 119   sact[sig].sa_handler = disp;
 120   sigemptyset(&set);
 121   sact[sig].sa_mask = set;
 122   if (!is_sigset) {

 123     sact[sig].sa_flags = SA_NODEFER;
 124     if (sig != SIGILL && sig != SIGTRAP && sig != SIGPWR) {
 125       sact[sig].sa_flags |= SA_RESETHAND;
 126     }



 127   } else {
 128     sact[sig].sa_flags = 0;
 129   }
 130 }
 131 
 132 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
 133   sa_handler_t oldhandler;

 134   bool sigblocked;
 135 
 136   signal_lock();
 137   if (sact == NULL) {
 138     allocate_sact();
 139   }
 140 
 141   if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {

 142     /* jvm has installed its signal handler for this signal. */
 143     /* Save the handler. Don't really install it. */
 144     if (is_sigset) {
 145       /* We won't honor the SIG_HOLD request to change the signal mask */
 146       sigblocked = sigismember(&(sact[sig].sa_mask), sig);
 147     }
 148     oldhandler = sact[sig].sa_handler;
 149     save_signal_handler(sig, disp, is_sigset);
 150 

 151     if (is_sigset && sigblocked) {

 152       oldhandler = SIG_HOLD;
 153     }

 154 
 155     signal_unlock();
 156     return oldhandler;
 157   } else if (jvm_signal_installing) {
 158     /* jvm is installing its signal handlers. Install the new
 159      * handlers and save the old ones. jvm uses sigaction().
 160      * Leave the piece here just in case. */
 161     oldhandler = call_os_signal(sig, disp, is_sigset);
 162     save_signal_handler(sig, oldhandler, is_sigset);
 163 
 164     /* Record the signals used by jvm */
 165     sigaddset(&jvmsigs, sig);
 166 
 167     signal_unlock();
 168     return oldhandler;
 169   } else {
 170     /* jvm has no relation with this signal (yet). Install the
 171      * the handler. */
 172     oldhandler = call_os_signal(sig, disp, is_sigset);
 173 
 174     signal_unlock();
 175     return oldhandler;
 176   }
 177 }
 178 
 179 sa_handler_t signal(int sig, sa_handler_t disp) {
 180   return set_signal(sig, disp, false);
 181 }
 182 
 183 sa_handler_t sigset(int sig, sa_handler_t disp) {




 184   return set_signal(sig, disp, true);

 185 }
 186 
 187 static int call_os_sigaction(int sig, const struct sigaction  *act,
 188                              struct sigaction *oact) {
 189   if (os_sigaction == NULL) {



 190     os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");

 191     if (os_sigaction == NULL) {
 192       printf("%s\n", dlerror());
 193       exit(0);
 194     }
 195   }
 196   return (*os_sigaction)(sig, act, oact);
 197 }
 198 
 199 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
 200   int res;

 201   struct sigaction oldAct;
 202 




 203   signal_lock();
 204 
 205   if (sact == NULL ) {
 206     allocate_sact();
 207   }
 208   if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
 209     /* jvm has installed its signal handler for this signal. */
 210     /* Save the handler. Don't really install it. */
 211     if (oact != NULL) {
 212       *oact = sact[sig];
 213     }
 214     if (act != NULL) {
 215       sact[sig] = *act;
 216     }
 217 
 218     signal_unlock();
 219     return 0;
 220   } else if (jvm_signal_installing) {
 221     /* jvm is installing its signal handlers. Install the new
 222      * handlers and save the old ones. */
 223     res = call_os_sigaction(sig, act, &oldAct);
 224     sact[sig] = oldAct;
 225     if (oact != NULL) {
 226       *oact = oldAct;
 227     }
 228 
 229     /* Record the signals used by jvm */
 230     sigaddset(&jvmsigs, sig);
 231 
 232     signal_unlock();
 233     return res;
 234   } else {
 235     /* jvm has no relation with this signal (yet). Install the
 236      * the handler. */
 237     res = call_os_sigaction(sig, act, oact);
 238 
 239     signal_unlock();
 240     return res;
 241   }
 242 }
 243 
 244 /* The four functions for the jvm to call into */
 245 void JVM_begin_signal_setting() {
 246   signal_lock();

 247   jvm_signal_installing = true;

 248   tid = thr_self();



 249   signal_unlock();
 250 }
 251 
 252 void JVM_end_signal_setting() {
 253   signal_lock();
 254   jvm_signal_installed = true;
 255   jvm_signal_installing = false;

 256   cond_broadcast(&cond);



 257   signal_unlock();
 258 }
 259 
 260 struct sigaction *JVM_get_signal_action(int sig) {
 261   if (sact == NULL) {
 262     allocate_sact();
 263   }
 264   /* Does race condition make sense here? */
 265   if (sigismember(&jvmsigs, sig)) {
 266     return &sact[sig];
 267   }
 268   return NULL;
 269 }
 270 
 271 int JVM_get_libjsig_version() {
 272   return JSIG_VERSION_1_4_1;
 273 }
--- EOF ---