src/jdk.jfr/share/classes/jdk/jfr/internal/JVMUpcalls.java

/*
 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
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 */
package jdk.jfr.internal;

import java.lang.reflect.Modifier;

import jdk.jfr.Event;
import jdk.jfr.internal.handlers.EventHandler;
import jdk.jfr.internal.instrument.JDKEvents;

/**
 * All upcalls from the JVM should go through this class.
 *
 */
// Called by native
final class JVMUpcalls {
    /**
     * Called by the JVM when a retransform happens on a tagged class
     *
     * @param traceId
     *            Id of the class
     * @param dummy
     *            (not used but needed since invoke infrastructure in native
     *            uses same signature bytesForEagerInstrumentation)
     * @param clazz
     *            class being retransformed
     * @param oldBytes
     *            byte code
     * @return byte code to use
     * @throws Throwable
     */
    static byte[] onRetransform(long traceId, boolean dummy, Class<?> clazz, byte[] oldBytes) throws Throwable {
        try {
            if (Event.class.isAssignableFrom(clazz) && !Modifier.isAbstract(clazz.getModifiers())) {
                EventHandler handler = Utils.getHandler(clazz.asSubclass(Event.class));
                if (handler == null) {
                    Logger.log(LogTag.JFR_SYSTEM, LogLevel.INFO, "No event handler found for " + clazz.getName() + ". Ignoring instrumentation request.");
                    // Probably triggered by some other agent
                    return oldBytes;
                }
                Logger.log(LogTag.JFR_SYSTEM, LogLevel.INFO, "Adding instrumentation to event class " + clazz.getName() + " using retransform");
                EventInstrumentation ei = new EventInstrumentation(clazz.getSuperclass(), oldBytes, traceId);
                byte[] bytes = ei.buildInstrumented();
                ASMToolkit.logASM(clazz.getName(), bytes);
                return bytes;
            }
            return JDKEvents.retransformCallback(clazz, oldBytes);
        } catch (Throwable t) {
            Logger.log(LogTag.JFR_SYSTEM, LogLevel.WARN, "Unexpected error when adding instrumentation to event class " + clazz.getName());
        }
        return oldBytes;

    }

    /**
     * Called by the JVM when requested to do an "eager" instrumentation. Would
     * normally happen when JVMTI retransform capabilities are not available.
     *
     * @param traceId
     *            Id of the class
     * @param forceInstrumentation
     *            add instrumentation regardless if event is enabled or not.
     * @param superClazz
     *            the super class of the class being processed
     * @param oldBytes
     *            byte code
     * @return byte code to use
     * @throws Throwable
     */
    static byte[] bytesForEagerInstrumentation(long traceId, boolean forceInstrumentation, Class<?> superClass, byte[] oldBytes) throws Throwable {
        if (JVMSupport.isNotAvailable()) {
            return oldBytes;
        }
        String eventName = "<Unknown>";
        try {
            EventInstrumentation ei = new EventInstrumentation(superClass, oldBytes, traceId);
            eventName = ei.getEventName();
            if (!forceInstrumentation) {
                // Assume we are recording
                MetadataRepository mr = MetadataRepository.getInstance();
                // No need to generate bytecode if:
                // 1) Event class is disabled, and there is not an external configuration that overrides.
                // 2) Event class has @Registered(false)
                if (!mr.isEnabled(ei.getEventName()) && !ei.isEnabled() || !ei.isRegistered()) {
                    Logger.log(LogTag.JFR_SYSTEM, LogLevel.INFO, "Skipping instrumentation for event type " + eventName + " since event was disabled on class load");
                    return oldBytes;
                }
            }
            // Corner case when we are forced to generate bytecode. We can't reference the event
            // handler in #isEnabled() before event class has been registered, so we add a
            // guard against a null reference.
            ei.setGuardHandler(true);
            Logger.log(LogTag.JFR_SYSTEM, LogLevel.INFO, "Adding " + (forceInstrumentation ? "forced " : "") + "instrumentation for event type " + eventName + " during initial class load");
            EventHandlerCreator eh = new EventHandlerCreator(traceId, ei.getSettingInfos(), ei.getFieldInfos());
            // Handler class must be loaded before instrumented event class can
            // be used
            eh.makeEventHandlerClass();
            byte[] bytes = ei.buildInstrumented();
            ASMToolkit.logASM(ei.getClassName() + "(" + traceId + ")", bytes);
            return bytes;
        } catch (Throwable t) {
            Logger.log(LogTag.JFR_SYSTEM, LogLevel.WARN, "Unexpected error when adding instrumentation for event type " + eventName);
            return oldBytes;
        }
    }

    /**
     * Called by the JVM to create the recorder thread.
     *
     * @param systemThreadGroup
     *            the system thread group
     *
     * @param contextClassLoader
     *            the context class loader.
     *
     * @return a new thread
     */
    static Thread createRecorderThread(ThreadGroup systemThreadGroup, ClassLoader contextClassLoader) {
        return SecuritySupport.createRecorderThread(systemThreadGroup, contextClassLoader);
    }
}