--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/os/linux/vm/jsig.c	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,227 @@
+/*
+ * Copyright 2001-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+/* CopyrightVersion 1.2 */
+
+/* This is a special library that should be loaded before libc &
+ * libthread to interpose the signal handler installation functions:
+ * sigaction(), signal(), sigset().
+ * Used for signal-chaining. See RFE 4381843.
+ */
+
+#include <signal.h>
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define bool int
+#define true 1
+#define false 0
+
+#define MAXSIGNUM 32
+#define MASK(sig) ((unsigned int)1 << sig)
+
+static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
+static unsigned int jvmsigs = 0; /* signals used by jvm */
+
+/* used to synchronize the installation of signal handlers */
+static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
+static pthread_t tid = 0;
+
+typedef void (*sa_handler_t)(int);
+typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
+typedef sa_handler_t (*signal_t)(int, sa_handler_t);
+typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
+
+static signal_t os_signal = 0; /* os's version of signal()/sigset() */
+static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
+
+static bool jvm_signal_installing = false;
+static bool jvm_signal_installed = false;
+
+static void signal_lock() {
+  pthread_mutex_lock(&mutex);
+  /* When the jvm is installing its set of signal handlers, threads
+   * other than the jvm thread should wait */
+  if (jvm_signal_installing) {
+    if (tid != pthread_self()) {
+      pthread_cond_wait(&cond, &mutex);
+    }
+  }
+}
+
+static void signal_unlock() {
+  pthread_mutex_unlock(&mutex);
+}
+
+static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
+                                   bool is_sigset) {
+  if (os_signal == NULL) {
+    if (!is_sigset) {
+      os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
+    } else {
+      os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
+    }
+    if (os_signal == NULL) {
+      printf("%s\n", dlerror());
+      exit(0);
+    }
+  }
+  return (*os_signal)(sig, disp);
+}
+
+static void save_signal_handler(int sig, sa_handler_t disp) {
+  sigset_t set;
+  sact[sig].sa_handler = disp;
+  sigemptyset(&set);
+  sact[sig].sa_mask = set;
+  sact[sig].sa_flags = 0;
+}
+
+static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
+  sa_handler_t oldhandler;
+  bool sigused;
+
+  signal_lock();
+
+  sigused = (MASK(sig) & jvmsigs) != 0;
+  if (jvm_signal_installed && sigused) {
+    /* jvm has installed its signal handler for this signal. */
+    /* Save the handler. Don't really install it. */
+    oldhandler = sact[sig].sa_handler;
+    save_signal_handler(sig, disp);
+
+    signal_unlock();
+    return oldhandler;
+  } else if (jvm_signal_installing) {
+    /* jvm is installing its signal handlers. Install the new
+     * handlers and save the old ones. jvm uses sigaction().
+     * Leave the piece here just in case. */
+    oldhandler = call_os_signal(sig, disp, is_sigset);
+    save_signal_handler(sig, oldhandler);
+
+    /* Record the signals used by jvm */
+    jvmsigs |= MASK(sig);
+
+    signal_unlock();
+    return oldhandler;
+  } else {
+    /* jvm has no relation with this signal (yet). Install the
+     * the handler. */
+    oldhandler = call_os_signal(sig, disp, is_sigset);
+
+    signal_unlock();
+    return oldhandler;
+  }
+}
+
+sa_handler_t signal(int sig, sa_handler_t disp) {
+  return set_signal(sig, disp, false);
+}
+
+sa_handler_t sigset(int sig, sa_handler_t disp) {
+  return set_signal(sig, disp, true);
+ }
+
+static int call_os_sigaction(int sig, const struct sigaction  *act,
+                             struct sigaction *oact) {
+  if (os_sigaction == NULL) {
+    os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
+    if (os_sigaction == NULL) {
+      printf("%s\n", dlerror());
+      exit(0);
+    }
+  }
+  return (*os_sigaction)(sig, act, oact);
+}
+
+int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
+  int res;
+  bool sigused;
+  struct sigaction oldAct;
+
+  signal_lock();
+
+  sigused = (MASK(sig) & jvmsigs) != 0;
+  if (jvm_signal_installed && sigused) {
+    /* jvm has installed its signal handler for this signal. */
+    /* Save the handler. Don't really install it. */
+    if (oact != NULL) {
+      *oact = sact[sig];
+    }
+    if (act != NULL) {
+      sact[sig] = *act;
+    }
+
+    signal_unlock();
+    return 0;
+  } else if (jvm_signal_installing) {
+    /* jvm is installing its signal handlers. Install the new
+     * handlers and save the old ones. */
+    res = call_os_sigaction(sig, act, &oldAct);
+    sact[sig] = oldAct;
+    if (oact != NULL) {
+      *oact = oldAct;
+    }
+
+    /* Record the signals used by jvm */
+    jvmsigs |= MASK(sig);
+
+    signal_unlock();
+    return res;
+  } else {
+    /* jvm has no relation with this signal (yet). Install the
+     * the handler. */
+    res = call_os_sigaction(sig, act, oact);
+
+    signal_unlock();
+    return res;
+  }
+}
+
+/* The three functions for the jvm to call into */
+void JVM_begin_signal_setting() {
+  signal_lock();
+  jvm_signal_installing = true;
+  tid = pthread_self();
+  signal_unlock();
+}
+
+void JVM_end_signal_setting() {
+  signal_lock();
+  jvm_signal_installed = true;
+  jvm_signal_installing = false;
+  pthread_cond_broadcast(&cond);
+  signal_unlock();
+}
+
+struct sigaction *JVM_get_signal_action(int sig) {
+  /* Does race condition make sense here? */
+  if ((MASK(sig) & jvmsigs) != 0) {
+    return &sact[sig];
+  }
+  return NULL;
+}