JIT debug agent using ASM

jit-debug-agent/DebugAgent.mf

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+Manifest-Version: 1.0
+Premain-Class: DebugAgent
+Agent-Class: DebugAgent
+Class-path: asm-9.2.jar junit-4.12.jar
+Can-Redefine-Classes: true
+Can-Retransform-Classes: true

jit-debug-agent/README.md

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+# OpenJ9 JIT Debug Agent
+
+This tool automatically obtains a limited JIT trace log for a miscompiled method. It works by using preexistence
+and a hooked internal API to repeatedly run a test by sequentially reverting JIT methods to be executed in the interpreter.
+By repeatedly executing a test in a controlled environment we are able to devertmine which JIT method needs to be interpreted
+for the test to start passing. This is how the tool determines which JIT method _may_ be responsible for the test case failure.
+
+Once the JIT method is identified the tool performs a `lastOptIndex` search by recompiling the JIT method at different
+optimization levels. Once again, when the test starts passing we have determined the minimal `lastOptIndex` which causes the
+failure. At that point the tool gather a _"good"_ and _"bad"_ JIT trace log with the optimization included and excluded for
+JIT developers to investigate.
+
+# When to use this tool
+
+This tool should be used for highly intermittent JIT defects from automated testing environments where we are either not able
+to determine the JIT method responsible for the failure, or we are unable to trace the suspect JIT method due to a Heisenbug.
+
+# How to use this tool
+
+1. Using maven and running the command `$ mvn install` in this directory will package the agent into a jar file, you will find it in the `target` directory. 
+2. add the java agent option to your `java` execution which would look like this: `-javaagent: jit-debug-agent-1.0.jar`
+3. Run the test by forcing preexistence.
+
+    Currently the tool is not robust enough to enable this automatically, so we have to force every JIT method compilation to use
+    preexistence. This is to ensure that we have a _revert to interpreter_ stub inserted in the preprologue of every method.
+    Inserting this stub happens at binary encoding and should not affect the semantics of the method itself.
+
+    ```
+    java -Xdump:none -Xnoaot -Xcheck:jni -Xjit:forceUsePreexistence -javaagent: jit-debug-agent-1.0.jar <test>

jit-debug-agent/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>org.openj9</groupId>
+    <artifactId>jit-debug-agent</artifactId>
+    <version>1.0</version>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm</artifactId>
+            <version>9.2</version>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>compile</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <configuration>
+                    <archive>
+                        <manifestEntries>
+                            <Premain-Class>
+                                DebugAgent
+                            </Premain-Class>
+                            <Can-Retransform-Classes>
+                                true
+                            </Can-Retransform-Classes>
+                            <Can-Redefine-Classes>
+                                true
+                            </Can-Redefine-Classes>
+                        </manifestEntries>
+                    </archive>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <appendAssemblyId>false</appendAssemblyId>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>make-assembly</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

jit-debug-agent/src/main/java/DebugAgent.java

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+/*******************************************************************************
+ * Copyright (c) 2021, 2021 IBM Corp. and others
+ *
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which accompanies this
+ * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
+ * or the Apache License, Version 2.0 which accompanies this distribution and
+ * is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * This Source Code may also be made available under the following
+ * Secondary Licenses when the conditions for such availability set
+ * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
+ * General Public License, version 2 with the GNU Classpath
+ * Exception [1] and GNU General Public License, version 2 with the
+ * OpenJDK Assembly Exception [2].
+ *
+ * [1] https://www.gnu.org/software/classpath/license.html
+ * [2] http://openjdk.java.net/legal/assembly-exception.html
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
+ *******************************************************************************/
+import java.lang.instrument.*;
+import java.security.ProtectionDomain;
+import java.io.IOException;
+
+public class DebugAgent {
+
+    private static String REFLECT_METHOD_NAME = "java/lang/reflect/Method";
+    private static String EXPECT_EXCEPTION_NAME = "org/junit/internal/runners/statements/ExpectException";
+    private static Class REFLECT_METHOD_CLASS = java.lang.reflect.Method.class;
+    private static Class EXPECT_EXCEPTION_CLASS = org.junit.internal.runners.statements.ExpectException.class;
+    private static String INVOKE = "invoke";
+    private static String EVALUATE = "evaluate";
+
+    public static void premain(String args, Instrumentation inst) throws Exception {
+        inst.addTransformer(new ClassFileTransformer(){
+            @Override
+            public byte[] transform(
+                    ClassLoader l,
+                    String name,
+                    Class c,
+                    ProtectionDomain d,
+                    byte[] b
+            ) throws IllegalClassFormatException {
+                if(name.equals(REFLECT_METHOD_NAME)) {
+                    try {
+                        DebugClassWriter writer = new DebugClassWriter(c.getName());
+                        return writer.applyDebugger(INVOKE);
+                    } catch (IOException e) {
+                        System.out.println(e);
+                    }
+                }
+
+                if(name.equals(EXPECT_EXCEPTION_NAME)) {
+                    try{
+                        DebugClassWriter writer = new DebugClassWriter(c.getName());
+                        return writer.applyDebugger(EVALUATE);
+                    } catch (IOException e) {
+                        System.out.println(e);
+                    }
+                }
+                return b;
+            }
+        }, true);
+
+        Class[] classesToTransform = {EXPECT_EXCEPTION_CLASS, REFLECT_METHOD_CLASS};
+        inst.retransformClasses(classesToTransform);
+    }
+}

jit-debug-agent/src/main/java/DebugClassWriter.java

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+/*******************************************************************************
+ * Copyright (c) 2021, 2021 IBM Corp. and others
+ *
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which accompanies this
+ * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
+ * or the Apache License, Version 2.0 which accompanies this distribution and
+ * is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * This Source Code may also be made available under the following
+ * Secondary Licenses when the conditions for such availability set
+ * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
+ * General Public License, version 2 with the GNU Classpath
+ * Exception [1] and GNU General Public License, version 2 with the
+ * OpenJDK Assembly Exception [2].
+ *
+ * [1] https://www.gnu.org/software/classpath/license.html
+ * [2] http://openjdk.java.net/legal/assembly-exception.html
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
+ *******************************************************************************/
+import org.objectweb.asm.*;
+import java.io.IOException;
+
+public class DebugClassWriter {
+    private ClassReader reader;
+    private ClassWriter writer;
+    private static String INVOKE = "invoke";
+
+
+    public DebugClassWriter(String className) throws IOException {
+        reader = new ClassReader(className);
+        writer = new ClassWriter(reader, ClassWriter.COMPUTE_FRAMES);
+    }
+
+    public byte[] applyDebugger(String methodName){
+        if (methodName == INVOKE) {
+            MethodDebugAdapter methodDebugAdapter = new MethodDebugAdapter(methodName, writer);
+            reader.accept(methodDebugAdapter, 0);
+        } else {
+            ExpectDebugAdapter expectDebugAdapter = new ExpectDebugAdapter(methodName, writer);
+            reader.accept(expectDebugAdapter, 0);
+        }
+
+        return writer.toByteArray();
+    }
+}

jit-debug-agent/src/main/java/EvaluateDebugAdapter.java

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+/*******************************************************************************
+ * Copyright (c) 2021, 2021 IBM Corp. and others
+ *
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which accompanies this
+ * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
+ * or the Apache License, Version 2.0 which accompanies this distribution and
+ * is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * This Source Code may also be made available under the following
+ * Secondary Licenses when the conditions for such availability set
+ * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
+ * General Public License, version 2 with the GNU Classpath
+ * Exception [1] and GNU General Public License, version 2 with the
+ * OpenJDK Assembly Exception [2].
+ *
+ * [1] https://www.gnu.org/software/classpath/license.html
+ * [2] http://openjdk.java.net/legal/assembly-exception.html
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
+ *******************************************************************************/
+import org.objectweb.asm.*;
+
+public class EvaluateDebugAdapter extends MethodVisitor {
+
+    public EvaluateDebugAdapter(MethodVisitor mv) {
+        super(Opcodes.ASM9, mv);
+        this.mv = mv;
+    }
+
+    @Override
+    public void visitCode() {
+        mv.visitCode();
+        mv.visitVarInsn(Opcodes.ALOAD, 0);
+        mv.visitFieldInsn(Opcodes.GETFIELD, "org/junit/internal/runners/statements/ExpectException", "expected", "Ljava/lang/Class;");
+        mv.visitMethodInsn(Opcodes.INVOKESTATIC, "com/ibm/jit/JITHelpers", "setExpectedException", "(Ljava/lang/Class;)V", false);
+    }
+
+    @Override
+    public void visitLineNumber(int line, Label start){
+        mv.visitLineNumber(line, start);
+        if (line == 31) {
+            mv.visitInsn(Opcodes.ACONST_NULL);
+            mv.visitMethodInsn(Opcodes.INVOKESTATIC, "com/ibm/jit/JITHelpers", "setExpectedException", "(Ljava/lang/Class;)V", false);
+        }
+    }
+
+}

jit-debug-agent/src/main/java/ExpectDebugAdapter.java

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+/*******************************************************************************
+ * Copyright (c) 2021, 2021 IBM Corp. and others
+ *
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which accompanies this
+ * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
+ * or the Apache License, Version 2.0 which accompanies this distribution and
+ * is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * This Source Code may also be made available under the following
+ * Secondary Licenses when the conditions for such availability set
+ * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
+ * General Public License, version 2 with the GNU Classpath
+ * Exception [1] and GNU General Public License, version 2 with the
+ * OpenJDK Assembly Exception [2].
+ *
+ * [1] https://www.gnu.org/software/classpath/license.html
+ * [2] http://openjdk.java.net/legal/assembly-exception.html
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
+ *******************************************************************************/
+import org.objectweb.asm.*;
+
+public class ExpectDebugAdapter extends ClassVisitor {
+    private String methodName;
+    private int access = org.objectweb.asm.Opcodes.ACC_PUBLIC;
+
+    public ExpectDebugAdapter(String methodName, ClassVisitor cv) {
+        super(org.objectweb.asm.Opcodes.ASM9, cv);
+        this.cv = cv;
+        this.methodName = methodName;
+    }
+
+    @Override
+    public MethodVisitor visitMethod(
+            int access,
+            String name,
+            String desc,
+            String signature,
+            String[] exceptions) {
+        MethodVisitor mv;
+        mv =  cv.visitMethod(
+                access,
+                name,
+                desc,
+                signature,
+                exceptions);
+        if (name.equals(methodName) && mv != null) {
+            return new EvaluateDebugAdapter(mv);
+        }
+        return mv;
+    }
+}

jit-debug-agent/src/main/java/InvokeDebugAdapter.java

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+/*******************************************************************************
+ * Copyright (c) 2021, 2021 IBM Corp. and others
+ *
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which accompanies this
+ * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
+ * or the Apache License, Version 2.0 which accompanies this distribution and
+ * is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * This Source Code may also be made available under the following
+ * Secondary Licenses when the conditions for such availability set
+ * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
+ * General Public License, version 2 with the GNU Classpath
+ * Exception [1] and GNU General Public License, version 2 with the
+ * OpenJDK Assembly Exception [2].
+ *
+ * [1] https://www.gnu.org/software/classpath/license.html
+ * [2] http://openjdk.java.net/legal/assembly-exception.html
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
+ *******************************************************************************/
+import org.objectweb.asm.*;
+
+public class InvokeDebugAdapter extends MethodVisitor {
+    public InvokeDebugAdapter(MethodVisitor mv) {
+        super(Opcodes.ASM9, mv);
+    }
+
+    @Override
+    public void visitMethodInsn(int opcode, java.lang.String owner, java.lang.String name, java.lang.String descriptor, boolean isInterface) {
+        if(opcode==Opcodes.INVOKEINTERFACE){
+            mv.visitMethodInsn(
+                    Opcodes.INVOKESTATIC,
+                    "com/ibm/jit/JITHelpers",
+                    "invoke",
+                    "(Ljdk/internal/reflect/MethodAccessor;Ljava/lang/Object;[Ljava/lang/Object;)Ljava/lang/Object;",
+                    false);
+        } else {
+            mv.visitMethodInsn(opcode, owner, name, descriptor, isInterface);
+        }
+    }
+}