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_solaris.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 }