instrumentation代码示例

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非Attach方式

src\main\resources\META-INF\MANIFEST.MF

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Premain-Class: org.example.AgentMain
Agent-Class: org.example.AgentMain
Can-Redefine-Classes: true
Can-Retransform-Classes: true

pom

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<dependency>
    <groupId>org.ow2.asm</groupId>
    <artifactId>asm</artifactId>
    <version>9.1</version>
</dependency>

<dependency>
    <groupId>org.ow2.asm</groupId>
    <artifactId>asm-commons</artifactId>
    <version>8.0</version>
</dependency>


<plugin>
    <artifactId>maven-jar-plugin</artifactId>
    <version>3.0.2</version>
    <configuration>
    <archive>
        <manifestEntries>
        <Agent-Class>org.example.AgentMain</Agent-Class>
        <Premain-Class>org.example.AgentMain</Premain-Class>
        <Can-Redefine-Classes>true</Can-Redefine-Classes>
        <Can-Retransform-Classes>true</Can-Retransform-Classes>
        </manifestEntries>
    </archive>
    </configuration>
</plugin>

MyTest

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package org.example;

public class MyTest {
    public static void main(String[] args) {
        new MyTest().foo();
    }

    public void foo() {
        bar1();
        bar2();
    }

    public void bar1() {

    }

    public void bar2() {

    }
}

AgentMain

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package org.example;

import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;

public class AgentMain {
    public static void premain(String agentArgs, Instrumentation inst) throws
        ClassNotFoundException, UnmodifiableClassException {
        inst.addTransformer(new MyClassFileTransformer(), true);
    }
}

MyMethodVisitor

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package org.example;

import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.commons.AdviceAdapter;

/**
 * 用来处理访问一个方法触发的事件
 * 在代码开始和结束前插入代码
 */
public class MyMethodVisitor extends AdviceAdapter {
    protected MyMethodVisitor(MethodVisitor methodVisitor, int access, String name, String descriptor) {
        super(ASM7, methodVisitor, access, name, descriptor);
    }

    @Override
    protected void onMethodEnter() {
        // <<<enter xxx
        mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        mv.visitLdcInsn("<<<enter " + this.getName());
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",
                "(Ljava/lang/String;)V", false);
        super.onMethodEnter();
    }

    @Override
    protected void onMethodExit(int opcode) {
        super.onMethodExit(opcode);
        // >>>exit xxx
        mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        mv.visitLdcInsn(">>>exit " + this.getName());
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",
                "(Ljava/lang/String;)V", false);
    }
}

MyClassVisitor

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package org.example;

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.MethodVisitor;
import static org.objectweb.asm.Opcodes.ASM7;

public class MyClassVisitor extends ClassVisitor {
    public MyClassVisitor(ClassVisitor classVisitor) {
        super(ASM7, classVisitor);
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exception) {
        MethodVisitor mv = super.visitMethod(access, name, descriptor, signature, exception);
        if (name.equals("<init>")) return mv;
        return new MyMethodVisitor(mv, access, name, descriptor);
    }
}

MyClassFileTransformer

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package org.example;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;

public class MyClassFileTransformer implements ClassFileTransformer {

    @Override
    public byte[] transform(ClassLoader loader, String className, Class<?>
            classBeingRedefined,
                            ProtectionDomain protectionDomain, byte[] classfileBuffer)
            throws IllegalClassFormatException {
        if (!"MyTest".equals(className)) return classfileBuffer;
        ClassReader cr = new ClassReader(classfileBuffer);
        ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_FRAMES);
        ClassVisitor cv = new MyClassVisitor(cw);
        cr.accept(cv, ClassReader.SKIP_FRAMES | ClassReader.SKIP_DEBUG);
        return cw.toByteArray();
    }
}

启动

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java -javaagent:'D:\Projects\2022SEU\JVMBookTest\target\JVMBookTest-1.0-SNAPSHOT.jar' org.example.MyTest

Attach方式（成功复现！）

  • 《深入理解JVM字节码》7.3 Page180-183
  • 参考

测试代码中的main方法，每3秒输出foo的返回值100。后面会Attach上MyTestMain，修改foo的字节码，让foo返回50

主要类

  • MyTestMain
  • AgentMain
  • MyAttachMain

环境配置

  • 添加依赖

attach的使用涉及com.sun.tools.attach，因此需要在POM中引入本地tools包，否则会找不到tools。

tools包在JAVA_HOME，比如在我的设备中，其绝对位置为D:/Program Files/java/jdk1.8.0_261/lib/tools.jar 

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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.example</groupId>
  <artifactId>my-javaagent</artifactId>
  <version>1.0-SNAPSHOT</version>

  <!--项目名-->
  <name>my-javaagent</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <!--针对ASM的依赖-->
  <dependencies>
    <dependency>
      <groupId>org.ow2.asm</groupId>
      <artifactId>asm</artifactId>
      <version>9.1</version>
    </dependency>
    <dependency>
      <groupId>org.ow2.asm</groupId>
      <artifactId>asm-commons</artifactId>
      <version>8.0</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!--com.sun.tools的本地包-->
    <dependency>
      <groupId>com.sun</groupId>
      <artifactId>tools</artifactId>
      <version>1.8.0</version>
      <scope>system</scope>
      <systemPath>D:/Program Files/java/jdk1.8.0_261/lib/tools.jar</systemPath>
    </dependency>
  </dependencies>

  <build>
    <!--生成jar包的名称-->
    <finalName>my-attach-agent-project</finalName>

    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>

        <!--配置打包插件-->
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-jar-plugin</artifactId>
          <version>3.2.0</version>
          <configuration>
            <archive>
              <manifestEntries>
                <!--根据自己的代理类名进行配置-->
                <Agent-Class>org.example.AgentMain</Agent-Class>
                <!--<Premain-Class>org.example.AgentMain</Premain-Class>-->
                <Can-Redefine-Classes>true</Can-Redefine-Classes>
                <Can-Retransform-Classes>true</Can-Retransform-Classes>
              </manifestEntries>
            </archive>
          </configuration>
        </plugin>

        <!--这也是要添加的必要插件-->
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-shade-plugin</artifactId>
          <version>3.2.4</version>
          <executions>
            <execution>
              <phase>package</phase>
              <goals>
                <goal>shade</goal>
              </goals>
              <configuration>
                <relocations>
                  <relocation>
                    <pattern>org.ow2.asm</pattern>
                    <shadedPattern>me.ya.agent.hidden.org.objectweb.asm</shadedPattern>
                  </relocation>
                </relocations>
              </configuration>
            </execution>
          </executions>
        </plugin>

        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
        <plugin>
          <artifactId>maven-site-plugin</artifactId>
          <version>3.7.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-project-info-reports-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>
  • D:\Projects\2022SEU\my-javaagent\src\main\resources\META-INF\MANIFEST.MFMF文件配置，注意最后一行有空行 
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Manifest-Version: 1.0
Can-Redefine-Classes: true
Agent-Class: org.example.AgentMain
Can-Retransform-Classes: true
Permissions: all-permissions

AgentMain

代理类，包含了MethodVisitor、MyClassVisitor、MyClassFileTransformer以及agentmain（这里是动态配置，所以不用写入Premain类） 

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package org.example;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.commons.AdviceAdapter;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.security.ProtectionDomain;

import static org.objectweb.asm.Opcodes.ASM7;

public class AgentMain {


    public static class MyMethodVisitor extends AdviceAdapter {

        protected MyMethodVisitor( MethodVisitor methodVisitor,int access, String name, String desc) {
            super(ASM7,methodVisitor,access, name, desc);
        }

        @Override
        protected void onMethodEnter(){
            mv.visitIntInsn(BIPUSH,50);
            mv.visitInsn(IRETURN);
        }
    }

    public static class MyClassVisitor extends ClassVisitor {
        public MyClassVisitor(ClassVisitor classVisitor) {
            super(ASM7, classVisitor);
        }

        @Override
        public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions){

            MethodVisitor mv = super.visitMethod(access,name,descriptor,signature,exceptions);
            System.out.println(name);
            if ("foo".equalsIgnoreCase(name)) {
                return new MyMethodVisitor(mv,access,name,descriptor);
            }

            return mv;
        }
    }

    public static class MyClassFileTransformer implements ClassFileTransformer {
        @Override
        public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
            System.out.println("className:"+className);
//            if (!"com.lgydojava.jvmdemo.MyTestMain".equalsIgnoreCase(className)) {
//                return classfileBuffer;
//            }

            ClassReader cr = new ClassReader(classfileBuffer);
            ClassWriter cw = new ClassWriter(cr,ClassWriter.COMPUTE_FRAMES);
            ClassVisitor cv = new MyClassVisitor(cw);
            cr.accept(cv,ClassReader.SKIP_FRAMES | ClassReader.SKIP_DEBUG);
            return cw.toByteArray();
        }
    }

    public static void agentmain(String agentArgs, Instrumentation inst) throws UnmodifiableClassException {
        System.out.println("agentmain called");
        inst.addTransformer(new MyClassFileTransformer(),true);
        Class classes[] = inst.getAllLoadedClasses();

        for (int i = 0; i < classes.length; i++) {
            Class aClass = classes[i];
            String name = aClass.getName();
            System.out.println(name);
            if (name.equals("org.example.MyTestMain")) {
                System.out.println("Reloading: " + name);
                inst.retransformClasses(aClass);
                break;
            }
        }
    }
}

MyTestMain

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package org.example;

import java.util.concurrent.TimeUnit;

public class MyTestMain {

    public static void main(String[] args) throws InterruptedException {
        while (true) {
            System.out.println(foo());
            TimeUnit.SECONDS.sleep(3);
        }
    }

    private static int foo() {
        //将原来返回100的，改为返回50
        return 100;
    }
}

MyAttachMain

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package org.example;

import com.sun.tools.attach.AttachNotSupportedException;
import com.sun.tools.attach.VirtualMachine;

import java.io.IOException;

public class MyAttachMain {

    public static void main(String[] args) throws IOException, AttachNotSupportedException {
        VirtualMachine vm = VirtualMachine.attach(String.valueOf(8792));
        try {
            vm.loadAgent("D:\\Projects\\2022SEU\\my-javaagent\\target\\my-attach-agent-project.jar");
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            vm.detach();
        }
    }
}

启动方法

  • 运行MyTestMain
  • 在命令行中输入
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jps

显示MyTestMain的PID

  • 在MyAttachMain中填入PID
  • 在命令行输入以下命令，生成jar包 
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mvn clean package
  • 在MyAttachMain中loadAgent填入生成jar包的绝对位置
  • 运行MyAttachMain（不需要-javaagent，直接run即可）
  • 效果如图，从100变成50

通过Attach方式复现函数调用链Lab

配置同上（Attach方式）

AgentMain

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package org.example;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.commons.AdviceAdapter;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.security.ProtectionDomain;

import static org.objectweb.asm.Opcodes.ASM7;

public class AgentMain {
    public static class MyMethodVisitor extends AdviceAdapter {

        protected MyMethodVisitor( MethodVisitor methodVisitor,int access, String name, String desc) {
            super(ASM7,methodVisitor,access, name, desc);
        }

        @Override
        protected void onMethodEnter() {
            // <<<enter xxx
            mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
            mv.visitLdcInsn("<<<enter " + this.getName());
            mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",
                    "(Ljava/lang/String;)V", false);
//            mv.visitIntInsn(BIPUSH,50);
//            mv.visitInsn(IRETURN);
            super.onMethodEnter();
        }

        @Override
        protected void onMethodExit(int opcode) {
            super.onMethodExit(opcode);
            // >>>exit xxx
            mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
            mv.visitLdcInsn(">>>exit " + this.getName());
            mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",
                    "(Ljava/lang/String;)V", false);
        }
    }

    public static class MyClassVisitor extends ClassVisitor {
        public MyClassVisitor(ClassVisitor classVisitor) {
            super(ASM7, classVisitor);
        }

        @Override
        public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exception) {
            MethodVisitor mv = super.visitMethod(access, name, descriptor, signature, exception);
            if ("foo".equals(name)) return new MyMethodVisitor(mv, access, name, descriptor);
            return mv;
        }
    }

    public static class MyClassFileTransformer implements ClassFileTransformer {
        @Override
        public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
//            这个if不注释掉会导致进入去MethodEnter
//            if (!"org.example.MyTestMain".equals(className)) return classfileBuffer;
            ClassReader cr = new ClassReader(classfileBuffer);
            ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_FRAMES);
            ClassVisitor cv = new MyClassVisitor(cw);
            cr.accept(cv, ClassReader.SKIP_FRAMES | ClassReader.SKIP_DEBUG);
            return cw.toByteArray();
        }
    }

    public static void agentmain(String agentArgs, Instrumentation inst) throws UnmodifiableClassException {
        System.out.println("agentmain called");
        inst.addTransformer(new MyClassFileTransformer(),true);
        Class classes[] = inst.getAllLoadedClasses();

        for (int i = 0; i < classes.length; i++) {
            Class aClass = classes[i];
            String name = aClass.getName();
            System.out.println(name);
            if (name.equals("org.example.MyTestMain")) {
                System.out.println("Reloading: " + name);
                inst.retransformClasses(aClass);
                break;
            }
        }
    }
}

MyTestMain

这里在foo中加入了递增数字a和延迟时间，以观测变化 

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package org.example;

import java.util.concurrent.TimeUnit;

public class MyTestMain {
    private static int a = 1;

    public static void main(String[] args) throws InterruptedException {
        while (true)
            new MyTestMain().foo();
    }

    public void foo() throws InterruptedException {
        System.out.println(a++);
        TimeUnit.SECONDS.sleep(3);
        bar1();
        bar2();
    }

    public void bar1() {

    }

    public void bar2() {

    }
}

MyAttachMain

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package org.example;

import com.sun.tools.attach.AttachNotSupportedException;
import com.sun.tools.attach.VirtualMachine;

import java.io.IOException;

public class MyAttachMain {

    public static void main(String[] args) throws IOException, AttachNotSupportedException {
        VirtualMachine vm = VirtualMachine.attach(String.valueOf(14500));
        try {
            vm.loadAgent("D:\\Projects\\2022SEU\\my-javaagent\\target\\my-attach-agent-project.jar");
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            vm.detach();
        }
    }
}

启动

  • 启动MyTestMain，效果如下

  • jps看以下PID并填入MyAttachMain并保存
  • mvn clean package打包
  • 运行MyAttachMain
  • 观察MyTestMain输出结果，如下

【注意】

  • 上述只显示foo是因为在MyClassVisitor中，限定了foo的调教，只要无条件输出new MyMethodVisitor(mv, access, name, descriptor)，即可对所有函数调用进行打印 
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public static class MyClassVisitor extends ClassVisitor {
    public MyClassVisitor(ClassVisitor classVisitor) {
        super(ASM7, classVisitor);
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exception) {
        MethodVisitor mv = super.visitMethod(access, name, descriptor, signature, exception);
//            if ("foo".equals(name)) return new MyMethodVisitor(mv, access, name, descriptor);
//            return mv;
        return new MyMethodVisitor(mv, access, name, descriptor);
    }
}
  • 结果如下



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