1 /*
   2  * Copyright (c) 2016, 2019, 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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package jdk.jfr.internal;
  26 
  27 import java.io.IOException;
  28 
  29 /**
  30  * Checks if the running VM supports Flight Recorder.
  31  *
  32  * Purpose of this helper class is to detect early and cleanly if the VM has
  33  * support for Flight Recorder, i.e. not throw {@link UnsatisfiedLinkError} in
  34  * unexpected places.
  35  * <p>
  36  * This is needed so a disabled-jfr.jar can be built for non Oracle JDKs.
  37  */
  38 public final class JVMSupport {
  39 
  40     private static final String UNSUPPORTED_VM_MESSAGE = "Flight Recorder is not supported on this VM";
  41     private static final boolean notAvailable = !checkAvailability();
  42 
  43     private static boolean checkAvailability() {
  44         // set jfr.unsupported.vm to true to test API on an unsupported VM
  45         try {
  46             if (SecuritySupport.getBooleanProperty("jfr.unsupported.vm")) {
  47                 return false;
  48             }
  49         } catch (NoClassDefFoundError cnfe) {
  50             // May happen on JDK 8, where sun.misc.Unsafe can't be found
  51             return false;
  52         }
  53         try {
  54             // Will typically throw UnsatisfiedLinkError if
  55             // there is no native implementation
  56             JVM.getJVM().isAvailable();
  57             return true;
  58         } catch (Throwable t) {
  59             return false;
  60         }
  61     }
  62 
  63     public static void ensureWithInternalError() {
  64         if (notAvailable) {
  65             throw new InternalError(UNSUPPORTED_VM_MESSAGE);
  66         }
  67     }
  68 
  69     public static void ensureWithIOException() throws IOException {
  70         if (notAvailable) {
  71             throw new IOException(UNSUPPORTED_VM_MESSAGE);
  72         }
  73     }
  74 
  75     public static void ensureWithIllegalStateException() {
  76         if (notAvailable) {
  77             throw new IllegalStateException(UNSUPPORTED_VM_MESSAGE);
  78         }
  79     }
  80 
  81     public static boolean isNotAvailable() {
  82         return notAvailable;
  83     }
  84 }