1 /*

     2  * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * Copyright 2012, 2013 SAP AG. 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 

    40 #define bool int

    41 #define true 1

    42 #define false 0

    43 

    44 // Highest so far on AIX 5.2 is SIGSAK (63)

    45 #define MAXSIGNUM 63

    46 #define MASK(sig) ((unsigned int)1 << sig)

    47 

    48 static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */

    49 static unsigned int jvmsigs = 0; /* signals used by jvm */

    50 

    51 /* used to synchronize the installation of signal handlers */

    52 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

    53 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

    54 static pthread_t tid = 0;

    55 

    56 typedef void (*sa_handler_t)(int);

    57 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);

    58 // signal_t is already defined on AIX

    59 typedef sa_handler_t (*signal_like_function_t)(int, sa_handler_t);

    60 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);

    61 

    62 static signal_like_function_t os_signal = 0; /* os's version of signal()/sigset() */

    63 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */

    64 

    65 static bool jvm_signal_installing = false;

    66 static bool jvm_signal_installed = false;

    67 

    68 static void signal_lock() {

    69   pthread_mutex_lock(&mutex);

    70   /* When the jvm is installing its set of signal handlers, threads

    71    * other than the jvm thread should wait */

    72   if (jvm_signal_installing) {

    73     if (tid != pthread_self()) {

    74       pthread_cond_wait(&cond, &mutex);

    75     }

    76   }

    77 }

    78 

    79 static void signal_unlock() {

    80   pthread_mutex_unlock(&mutex);

    81 }

    82 

    83 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,

    84                                    bool is_sigset) {

    85   if (os_signal == NULL) {

    86     if (!is_sigset) {

    87       // Aix: call functions directly instead of dlsym'ing them

    88       os_signal = signal;

    89     } else {

    90       // Aix: call functions directly instead of dlsym'ing them

    91       os_signal = sigset;

    92     }

    93     if (os_signal == NULL) {

    94       printf("%s\n", dlerror());

    95       exit(0);

    96     }

    97   }

    98   return (*os_signal)(sig, disp);

    99 }

   100 

   101 static void save_signal_handler(int sig, sa_handler_t disp) {

   102   sigset_t set;

   103   sact[sig].sa_handler = disp;

   104   sigemptyset(&set);

   105   sact[sig].sa_mask = set;

   106   sact[sig].sa_flags = 0;

   107 }

   108 

   109 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {

   110   sa_handler_t oldhandler;

   111   bool sigused;

   112 

   113   signal_lock();

   114 

   115   sigused = (MASK(sig) & jvmsigs) != 0;

   116   if (jvm_signal_installed && sigused) {

   117     /* jvm has installed its signal handler for this signal. */

   118     /* Save the handler. Don't really install it. */

   119     oldhandler = sact[sig].sa_handler;

   120     save_signal_handler(sig, disp);

   121 

   122     signal_unlock();

   123     return oldhandler;

   124   } else if (jvm_signal_installing) {

   125     /* jvm is installing its signal handlers. Install the new

   126      * handlers and save the old ones. jvm uses sigaction().

   127      * Leave the piece here just in case. */

   128     oldhandler = call_os_signal(sig, disp, is_sigset);

   129     save_signal_handler(sig, oldhandler);

   130 

   131     /* Record the signals used by jvm */

   132     jvmsigs |= MASK(sig);

   133 

   134     signal_unlock();

   135     return oldhandler;

   136   } else {

   137     /* jvm has no relation with this signal (yet). Install the

   138      * the handler. */

   139     oldhandler = call_os_signal(sig, disp, is_sigset);

   140 

   141     signal_unlock();

   142     return oldhandler;

   143   }

   144 }

   145 

   146 sa_handler_t signal(int sig, sa_handler_t disp) {

   147   return set_signal(sig, disp, false);

   148 }

   149 

   150 sa_handler_t sigset(int sig, sa_handler_t disp) {

   151   return set_signal(sig, disp, true);

   152  }

   153 

   154 static int call_os_sigaction(int sig, const struct sigaction  *act,

   155                              struct sigaction *oact) {

   156   if (os_sigaction == NULL) {

   157     // Aix: call functions directly instead of dlsym'ing them

   158     os_sigaction = sigaction;

   159     if (os_sigaction == NULL) {

   160       printf("%s\n", dlerror());

   161       exit(0);

   162     }

   163   }

   164   return (*os_sigaction)(sig, act, oact);

   165 }

   166 

   167 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {

   168   int res;

   169   bool sigused;

   170   struct sigaction oldAct;

   171 

   172   signal_lock();

   173 

   174   sigused = (MASK(sig) & jvmsigs) != 0;

   175   if (jvm_signal_installed && sigused) {

   176     /* jvm has installed its signal handler for this signal. */

   177     /* Save the handler. Don't really install it. */

   178     if (oact != NULL) {

   179       *oact = sact[sig];

   180     }

   181     if (act != NULL) {

   182       sact[sig] = *act;

   183     }

   184 

   185     signal_unlock();

   186     return 0;

   187   } else if (jvm_signal_installing) {

   188     /* jvm is installing its signal handlers. Install the new

   189      * handlers and save the old ones. */

   190     res = call_os_sigaction(sig, act, &oldAct);

   191     sact[sig] = oldAct;

   192     if (oact != NULL) {

   193       *oact = oldAct;

   194     }

   195 

   196     /* Record the signals used by jvm */

   197     jvmsigs |= MASK(sig);

   198 

   199     signal_unlock();

   200     return res;

   201   } else {

   202     /* jvm has no relation with this signal (yet). Install the

   203      * the handler. */

   204     res = call_os_sigaction(sig, act, oact);

   205 

   206     signal_unlock();

   207     return res;

   208   }

   209 }

   210 

   211 /* The three functions for the jvm to call into */

   212 void JVM_begin_signal_setting() {

   213   signal_lock();

   214   jvm_signal_installing = true;

   215   tid = pthread_self();

   216   signal_unlock();

   217 }

   218 

   219 void JVM_end_signal_setting() {

   220   signal_lock();

   221   jvm_signal_installed = true;

   222   jvm_signal_installing = false;

   223   pthread_cond_broadcast(&cond);

   224   signal_unlock();

   225 }

   226 

   227 struct sigaction *JVM_get_signal_action(int sig) {

   228   /* Does race condition make sense here? */

   229   if ((MASK(sig) & jvmsigs) != 0) {

   230     return &sact[sig];

   231   }

   232   return NULL;

   233 }