src/jdk.attach/linux/classes/sun/tools/attach/VirtualMachineImpl.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 package sun.tools.attach;

 import com.sun.tools.attach.AttachOperationFailedException;
 import com.sun.tools.attach.AgentLoadException;
 import com.sun.tools.attach.AttachNotSupportedException;
 import com.sun.tools.attach.spi.AttachProvider;

 import java.io.InputStream;
 import java.io.IOException;
 import java.io.File;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.Files;

 /*
  * Linux implementation of HotSpotVirtualMachine
  */
 public class VirtualMachineImpl extends HotSpotVirtualMachine {
     // "/tmp" is used as a global well-known location for the files
     // .java_pid<pid>. and .attach_pid<pid>. It is important that this
     // location is the same for all processes, otherwise the tools
     // will not be able to find all Hotspot processes.
     // Any changes to this needs to be synchronized with HotSpot.
     private static final String tmpdir = "/tmp";
     String socket_path;
     /**
      * Attaches to the target VM
      */
     VirtualMachineImpl(AttachProvider provider, String vmid)
         throws AttachNotSupportedException, IOException
     {
         super(provider, vmid);

         // This provider only understands pids
         int pid;
         try {
             pid = Integer.parseInt(vmid);
         } catch (NumberFormatException x) {
             throw new AttachNotSupportedException("Invalid process identifier");
         }

         // Try to resolve to the "inner most" pid namespace
         int ns_pid = getNamespacePid(pid);

         // Find the socket file. If not found then we attempt to start the
         // attach mechanism in the target VM by sending it a QUIT signal.
         // Then we attempt to find the socket file again.
         File socket_file = findSocketFile(pid, ns_pid);
         socket_path = socket_file.getPath();
         if (!socket_file.exists()) {
             File f = createAttachFile(pid, ns_pid);
             try {
                 sendQuitTo(pid);

                 // give the target VM time to start the attach mechanism
                 final int delay_step = 100;
                 final long timeout = attachTimeout();
                 long time_spend = 0;
                 long delay = 0;
                 do {
                     // Increase timeout on each attempt to reduce polling
                     delay += delay_step;
                     try {
                         Thread.sleep(delay);
                     } catch (InterruptedException x) { }

                     time_spend += delay;
                     if (time_spend > timeout/2 && !socket_file.exists()) {
                         // Send QUIT again to give target VM the last chance to react
                         sendQuitTo(pid);
                     }
                 } while (time_spend <= timeout && !socket_file.exists());
                 if (!socket_file.exists()) {
                     throw new AttachNotSupportedException(
                         String.format("Unable to open socket file %s: " +
                           "target process %d doesn't respond within %dms " +
                           "or HotSpot VM not loaded", socket_path, pid,
                                       time_spend));
                 }
             } finally {
                 f.delete();
             }
         }

         // Check that the file owner/permission to avoid attaching to
         // bogus process
         checkPermissions(socket_path);

         // Check that we can connect to the process
         // - this ensures we throw the permission denied error now rather than
         // later when we attempt to enqueue a command.
         int s = socket();
         try {
             connect(s, socket_path);
         } finally {
             close(s);
         }
     }

     /**
      * Detach from the target VM
      */
     public void detach() throws IOException {
         synchronized (this) {
             if (socket_path != null) {
                 socket_path = null;
             }
         }
     }

     // protocol version
     private final static String PROTOCOL_VERSION = "1";

     // known errors
     private final static int ATTACH_ERROR_BADVERSION = 101;

     /**
      * Execute the given command in the target VM.
      */
     InputStream execute(String cmd, Object ... args) throws AgentLoadException, IOException {
         assert args.length <= 4;                // includes null

         // did we detach?
         synchronized (this) {
             if (socket_path == null) {
                 throw new IOException("Detached from target VM");
             }
         }

         // create UNIX socket
         int s = socket();

         // connect to target VM
         try {
             connect(s, socket_path);
         } catch (IOException x) {
             close(s);
             throw x;
         }

         IOException ioe = null;

         // connected - write request
         // <ver> <cmd> <args...>
         try {
             writeString(s, PROTOCOL_VERSION);
             writeString(s, cmd);

             for (int i = 0; i < 4; i++) {
                 if (i < args.length && args[i] != null) {
                     writeString(s, (String)args[i]);
                 } else {
                     writeString(s, "");
                 }
             }
         } catch (IOException x) {
             ioe = x;
         }


         // Create an input stream to read reply
         SocketInputStream sis = new SocketInputStream(s);

         // Read the command completion status
         int completionStatus;
         try {
             completionStatus = readInt(sis);
         } catch (IOException x) {
             sis.close();
             if (ioe != null) {
                 throw ioe;
             } else {
                 throw x;
             }
         }

         if (completionStatus != 0) {
             // read from the stream and use that as the error message
             String message = readErrorMessage(sis);
             sis.close();

             // In the event of a protocol mismatch then the target VM
             // returns a known error so that we can throw a reasonable
             // error.
             if (completionStatus == ATTACH_ERROR_BADVERSION) {
                 throw new IOException("Protocol mismatch with target VM");
             }

             // Special-case the "load" command so that the right exception is
             // thrown.
             if (cmd.equals("load")) {
                 String msg = "Failed to load agent library";
                 if (!message.isEmpty())
                     msg += ": " + message;
                 throw new AgentLoadException(msg);
             } else {
                 if (message.isEmpty())
                     message = "Command failed in target VM";
                 throw new AttachOperationFailedException(message);
             }
         }

         // Return the input stream so that the command output can be read
         return sis;
     }

     /*
      * InputStream for the socket connection to get target VM
      */
     private class SocketInputStream extends InputStream {
         int s;

         public SocketInputStream(int s) {
             this.s = s;
         }

         public synchronized int read() throws IOException {
             byte b[] = new byte[1];
             int n = this.read(b, 0, 1);
             if (n == 1) {
                 return b[0] & 0xff;
             } else {
                 return -1;
             }
         }

         public synchronized int read(byte[] bs, int off, int len) throws IOException {
             if ((off < 0) || (off > bs.length) || (len < 0) ||
                 ((off + len) > bs.length) || ((off + len) < 0)) {
                 throw new IndexOutOfBoundsException();
             } else if (len == 0) {
                 return 0;
             }

             return VirtualMachineImpl.read(s, bs, off, len);
         }

         public void close() throws IOException {
             VirtualMachineImpl.close(s);
         }
     }

     // Return the socket file for the given process.
     private File findSocketFile(int pid, int ns_pid) {
         // A process may not exist in the same mount namespace as the caller.
         // Instead, attach relative to the target root filesystem as exposed by
         // procfs regardless of namespaces.
         String root = "/proc/" + pid + "/root/" + tmpdir;
         return new File(root, ".java_pid" + ns_pid);
     }

     // On Linux a simple handshake is used to start the attach mechanism
     // if not already started. The client creates a .attach_pid<pid> file in the
     // target VM's working directory (or temp directory), and the SIGQUIT handler
     // checks for the file.
     private File createAttachFile(int pid, int ns_pid) throws IOException {
         String fn = ".attach_pid" + ns_pid;
         String path = "/proc/" + pid + "/cwd/" + fn;
         File f = new File(path);
         try {
             f = f.getCanonicalFile();
             f.createNewFile();
         } catch (IOException x) {
             String root;
             if (pid != ns_pid) {
                 // A process may not exist in the same mount namespace as the caller.
                 // Instead, attach relative to the target root filesystem as exposed by
                 // procfs regardless of namespaces.
                 root = "/proc/" + pid + "/root/" + tmpdir;
             } else {
                 root = tmpdir;
             }
             f = new File(root, fn);
             f = f.getCanonicalFile();
             f.createNewFile();
         }
         return f;
     }

     /*
      * Write/sends the given to the target VM. String is transmitted in
      * UTF-8 encoding.
      */
     private void writeString(int fd, String s) throws IOException {
         if (s.length() > 0) {
             byte b[];
             try {
                 b = s.getBytes("UTF-8");
             } catch (java.io.UnsupportedEncodingException x) {
                 throw new InternalError(x);
             }
             VirtualMachineImpl.write(fd, b, 0, b.length);
         }
         byte b[] = new byte[1];
         b[0] = 0;
         write(fd, b, 0, 1);
     }


     // Return the inner most namespaced PID if there is one,
     // otherwise return the original PID.
     private int getNamespacePid(int pid) throws AttachNotSupportedException, IOException {
         // Assuming a real procfs sits beneath, reading this doesn't block
         // nor will it consume a lot of memory.
         String statusFile = "/proc/" + pid + "/status";
         File f = new File(statusFile);
         if (!f.exists()) {
             return pid; // Likely a bad pid, but this is properly handled later.
         }

         Path statusPath = Paths.get(statusFile);

         try {
             for (String line : Files.readAllLines(statusPath, StandardCharsets.UTF_8)) {
                 String[] parts = line.split(":");
                 if (parts.length == 2 && parts[0].trim().equals("NSpid")) {
                     parts = parts[1].trim().split("\\s+");
                     // The last entry represents the PID the JVM "thinks" it is.
                     // Even in non-namespaced pids these entries should be
                     // valid. You could refer to it as the inner most pid.
                     int ns_pid = Integer.parseInt(parts[parts.length - 1]);
                     return ns_pid;
                 }
             }
             // Old kernels may not have NSpid field (i.e. 3.10).
             // Fallback to original pid in the event we cannot deduce.
             return pid;
         } catch (NumberFormatException | IOException x) {
             throw new AttachNotSupportedException("Unable to parse namespace");
         }
     }


     //-- native methods

     static native void sendQuitTo(int pid) throws IOException;

     static native void checkPermissions(String path) throws IOException;

     static native int socket() throws IOException;

     static native void connect(int fd, String path) throws IOException;

     static native void close(int fd) throws IOException;

     static native int read(int fd, byte buf[], int off, int bufLen) throws IOException;

     static native void write(int fd, byte buf[], int off, int bufLen) throws IOException;

     static {
         System.loadLibrary("attach");
     }
 }
	/*
	* Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package sun.tools.attach;

	import com.sun.tools.attach.AttachOperationFailedException;
	import com.sun.tools.attach.AgentLoadException;
	import com.sun.tools.attach.AttachNotSupportedException;
	import com.sun.tools.attach.spi.AttachProvider;

	import java.io.InputStream;
	import java.io.IOException;
	import java.io.File;
	import java.nio.charset.StandardCharsets;
	import java.nio.file.Path;
	import java.nio.file.Paths;
	import java.nio.file.Files;

	/*
	* Linux implementation of HotSpotVirtualMachine
	*/
	public class VirtualMachineImpl extends HotSpotVirtualMachine {
	// "/tmp" is used as a global well-known location for the files
	// .java_pid<pid>. and .attach_pid<pid>. It is important that this
	// location is the same for all processes, otherwise the tools
	// will not be able to find all Hotspot processes.
	// Any changes to this needs to be synchronized with HotSpot.
	private static final String tmpdir = "/tmp";
	String socket_path;
	/**
	* Attaches to the target VM
	*/
	VirtualMachineImpl(AttachProvider provider, String vmid)
	throws AttachNotSupportedException, IOException
	{
	super(provider, vmid);

	// This provider only understands pids
	int pid;
	try {
	pid = Integer.parseInt(vmid);
	} catch (NumberFormatException x) {
	throw new AttachNotSupportedException("Invalid process identifier");
	}

	// Try to resolve to the "inner most" pid namespace
	int ns_pid = getNamespacePid(pid);

	// Find the socket file. If not found then we attempt to start the
	// attach mechanism in the target VM by sending it a QUIT signal.
	// Then we attempt to find the socket file again.
	File socket_file = findSocketFile(pid, ns_pid);
	socket_path = socket_file.getPath();
	if (!socket_file.exists()) {
	File f = createAttachFile(pid, ns_pid);
	try {
	sendQuitTo(pid);

	// give the target VM time to start the attach mechanism
	final int delay_step = 100;
	final long timeout = attachTimeout();
	long time_spend = 0;
	long delay = 0;
	do {
	// Increase timeout on each attempt to reduce polling
	delay += delay_step;
	try {
	Thread.sleep(delay);
	} catch (InterruptedException x) { }

	time_spend += delay;
	if (time_spend > timeout/2 && !socket_file.exists()) {
	// Send QUIT again to give target VM the last chance to react
	sendQuitTo(pid);
	}
	} while (time_spend <= timeout && !socket_file.exists());
	if (!socket_file.exists()) {
	throw new AttachNotSupportedException(
	String.format("Unable to open socket file %s: " +
	"target process %d doesn't respond within %dms " +
	"or HotSpot VM not loaded", socket_path, pid,
	time_spend));
	}
	} finally {
	f.delete();
	}
	}

	// Check that the file owner/permission to avoid attaching to
	// bogus process
	checkPermissions(socket_path);

	// Check that we can connect to the process
	// - this ensures we throw the permission denied error now rather than
	// later when we attempt to enqueue a command.
	int s = socket();
	try {
	connect(s, socket_path);
	} finally {
	close(s);
	}
	}

	/**
	* Detach from the target VM
	*/
	public void detach() throws IOException {
	synchronized (this) {
	if (socket_path != null) {
	socket_path = null;
	}
	}
	}

	// protocol version
	private final static String PROTOCOL_VERSION = "1";

	// known errors
	private final static int ATTACH_ERROR_BADVERSION = 101;

	/**
	* Execute the given command in the target VM.
	*/
	InputStream execute(String cmd, Object ... args) throws AgentLoadException, IOException {
	assert args.length <= 4; // includes null

	// did we detach?
	synchronized (this) {
	if (socket_path == null) {
	throw new IOException("Detached from target VM");
	}
	}

	// create UNIX socket
	int s = socket();

	// connect to target VM
	try {
	connect(s, socket_path);
	} catch (IOException x) {
	close(s);
	throw x;
	}

	IOException ioe = null;

	// connected - write request
	// <ver> <cmd> <args...>
	try {
	writeString(s, PROTOCOL_VERSION);
	writeString(s, cmd);

	for (int i = 0; i < 4; i++) {
	if (i < args.length && args[i] != null) {
	writeString(s, (String)args[i]);
	} else {
	writeString(s, "");
	}
	}
	} catch (IOException x) {
	ioe = x;
	}


	// Create an input stream to read reply
	SocketInputStream sis = new SocketInputStream(s);

	// Read the command completion status
	int completionStatus;
	try {
	completionStatus = readInt(sis);
	} catch (IOException x) {
	sis.close();
	if (ioe != null) {
	throw ioe;
	} else {
	throw x;
	}
	}

	if (completionStatus != 0) {
	// read from the stream and use that as the error message
	String message = readErrorMessage(sis);
	sis.close();

	// In the event of a protocol mismatch then the target VM
	// returns a known error so that we can throw a reasonable
	// error.
	if (completionStatus == ATTACH_ERROR_BADVERSION) {
	throw new IOException("Protocol mismatch with target VM");
	}

	// Special-case the "load" command so that the right exception is
	// thrown.
	if (cmd.equals("load")) {
	String msg = "Failed to load agent library";
	if (!message.isEmpty())
	msg += ": " + message;
	throw new AgentLoadException(msg);
	} else {
	if (message.isEmpty())
	message = "Command failed in target VM";
	throw new AttachOperationFailedException(message);
	}
	}

	// Return the input stream so that the command output can be read
	return sis;
	}

	/*
	* InputStream for the socket connection to get target VM
	*/
	private class SocketInputStream extends InputStream {
	int s;

	public SocketInputStream(int s) {
	this.s = s;
	}

	public synchronized int read() throws IOException {
	byte b[] = new byte[1];
	int n = this.read(b, 0, 1);
	if (n == 1) {
	return b[0] & 0xff;
	} else {
	return -1;
	}
	}

	public synchronized int read(byte[] bs, int off, int len) throws IOException {
	if ((off < 0) \|\| (off > bs.length) \|\| (len < 0) \|\|
	((off + len) > bs.length) \|\| ((off + len) < 0)) {
	throw new IndexOutOfBoundsException();
	} else if (len == 0) {
	return 0;
	}

	return VirtualMachineImpl.read(s, bs, off, len);
	}

	public void close() throws IOException {
	VirtualMachineImpl.close(s);
	}
	}

	// Return the socket file for the given process.
	private File findSocketFile(int pid, int ns_pid) {
	// A process may not exist in the same mount namespace as the caller.
	// Instead, attach relative to the target root filesystem as exposed by
	// procfs regardless of namespaces.
	String root = "/proc/" + pid + "/root/" + tmpdir;
	return new File(root, ".java_pid" + ns_pid);
	}

	// On Linux a simple handshake is used to start the attach mechanism
	// if not already started. The client creates a .attach_pid<pid> file in the
	// target VM's working directory (or temp directory), and the SIGQUIT handler
	// checks for the file.
	private File createAttachFile(int pid, int ns_pid) throws IOException {
	String fn = ".attach_pid" + ns_pid;
	String path = "/proc/" + pid + "/cwd/" + fn;
	File f = new File(path);
	try {
	f = f.getCanonicalFile();
	f.createNewFile();
	} catch (IOException x) {
	String root;
	if (pid != ns_pid) {
	// A process may not exist in the same mount namespace as the caller.
	// Instead, attach relative to the target root filesystem as exposed by
	// procfs regardless of namespaces.
	root = "/proc/" + pid + "/root/" + tmpdir;
	} else {
	root = tmpdir;
	}
	f = new File(root, fn);
	f = f.getCanonicalFile();
	f.createNewFile();
	}
	return f;
	}

	/*
	* Write/sends the given to the target VM. String is transmitted in
	* UTF-8 encoding.
	*/
	private void writeString(int fd, String s) throws IOException {
	if (s.length() > 0) {
	byte b[];
	try {
	b = s.getBytes("UTF-8");
	} catch (java.io.UnsupportedEncodingException x) {
	throw new InternalError(x);
	}
	VirtualMachineImpl.write(fd, b, 0, b.length);
	}
	byte b[] = new byte[1];
	b[0] = 0;
	write(fd, b, 0, 1);
	}


	// Return the inner most namespaced PID if there is one,
	// otherwise return the original PID.
	private int getNamespacePid(int pid) throws AttachNotSupportedException, IOException {
	// Assuming a real procfs sits beneath, reading this doesn't block
	// nor will it consume a lot of memory.
	String statusFile = "/proc/" + pid + "/status";
	File f = new File(statusFile);
	if (!f.exists()) {
	return pid; // Likely a bad pid, but this is properly handled later.
	}

	Path statusPath = Paths.get(statusFile);

	try {
	for (String line : Files.readAllLines(statusPath, StandardCharsets.UTF_8)) {
	String[] parts = line.split(":");
	if (parts.length == 2 && parts[0].trim().equals("NSpid")) {
	parts = parts[1].trim().split("\\s+");
	// The last entry represents the PID the JVM "thinks" it is.
	// Even in non-namespaced pids these entries should be
	// valid. You could refer to it as the inner most pid.
	int ns_pid = Integer.parseInt(parts[parts.length - 1]);
	return ns_pid;
	}
	}
	// Old kernels may not have NSpid field (i.e. 3.10).
	// Fallback to original pid in the event we cannot deduce.
	return pid;
	} catch (NumberFormatException \| IOException x) {
	throw new AttachNotSupportedException("Unable to parse namespace");
	}
	}


	//-- native methods

	static native void sendQuitTo(int pid) throws IOException;

	static native void checkPermissions(String path) throws IOException;

	static native int socket() throws IOException;

	static native void connect(int fd, String path) throws IOException;

	static native void close(int fd) throws IOException;

	static native int read(int fd, byte buf[], int off, int bufLen) throws IOException;

	static native void write(int fd, byte buf[], int off, int bufLen) throws IOException;

	static {
	System.loadLibrary("attach");
	}
	}