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/*
* Copyright 2005-2006 Sun Microsystems, Inc. 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. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package sun.tools.attach;
import com.sun.tools.attach.AgentLoadException;
import com.sun.tools.attach.AttachNotSupportedException;
import com.sun.tools.attach.spi.AttachProvider;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
/**
* Linux implementation of HotSpotVirtualMachine.
*/
public final class LinuxVirtualMachine extends HotSpotVirtualMachine
{
// Indicates if this machine uses the old LinuxThreads.
static boolean isLinuxThreads;
// The patch to the socket file created by the target VM.
String path;
/**
* Attaches to the target VM.
*/
public LinuxVirtualMachine(AttachProvider provider, String vmid)
throws AttachNotSupportedException, IOException
{
super(provider, vmid);
// This provider only understands pids.
int pid = Integer.parseInt(vmid);
// 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.
path = findSocketFile(pid);
if (path == null) {
File f = createAttachFile(pid);
try {
// On LinuxThreads each thread is a process and we don't have the
// pid of the VMThread which has SIGQUIT unblocked. To workaround
// this we get the pid of the "manager thread" that is created
// by the first call to pthread_create. This is parent of all
// threads (except the initial thread).
if (isLinuxThreads) {
int mpid = getLinuxThreadsManager(pid);
assert mpid >= 1;
sendQuitToChildrenOf(mpid);
}
else {
sendQuitTo(pid);
}
// give the target VM time to start the attach mechanism
int i = 0;
long delay = 200;
int retries = (int) (attachTimeout() / delay);
do {
try {
Thread.sleep(delay);
}
catch (InterruptedException ignore) { }
path = findSocketFile(pid);
i++;
}
while (i <= retries && path == null);
if (path == null) {
throw new AttachNotSupportedException(
"Unable to open socket file: target process not responding " +
"or HotSpot VM not loaded");
}
}
finally {
f.delete();
}
}
// Check that the file owner/permission to avoid attaching to
// bogus process
checkPermissions(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, path);
}
finally {
close(s);
}
}
/**
* Detach from the target VM.
*/
@Override
public void detach()
{
synchronized (this) {
if (path != null) {
path = null;
}
}
}
// protocol version
private static final String PROTOCOL_VERSION = "1";
// known errors
private static final int ATTACH_ERROR_BADVERSION = 101;
/**
* Execute the given command in the target VM.
*/
@Override
InputStream execute(String cmd, Object... args) throws AgentLoadException, IOException
{
assert args.length <= 3; // includes null
// did we detach?
String p;
synchronized (this) {
if (path == null) {
throw new IOException("Detached from target VM");
}
p = path;
}
// create UNIX socket
int s = socket();
// connect to target VM
try {
connect(s, p);
}
catch (IOException x) {
close(s);
throw x;
}
IOException ioe = null;
// connected - write request
//
try {
writeString(s, PROTOCOL_VERSION);
writeString(s, cmd);
for (int i = 0; i < 3; 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) {
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 ("load".equals(cmd)) {
throw new AgentLoadException("Failed to load agent library");
}
else {
throw new IOException("Command failed in target VM");
}
}
// Return the input stream so that the command output can be read.
return sis;
}
/**
* InputStream for the socket connection to get target VM.
*/
private final class SocketInputStream extends InputStream
{
int s;
SocketInputStream(int s)
{
this.s = s;
}
@Override
public synchronized int read() throws IOException
{
byte[] b = new byte[1];
int n = read(b, 0, 1);
if (n == 1) {
return b[0] & 0xff;
}
else {
return -1;
}
}
@Override
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 LinuxVirtualMachine.read(s, bs, off, len);
}
@Override
public void close() throws IOException
{
LinuxVirtualMachine.close(s);
}
}
// Return the socket file for the given process.
// Checks working directory of process for .java_pid. If not
// found it looks in /tmp.
private String findSocketFile(int pid)
{
// First check for a .java_pid file in the working directory
// of the target process
String fn = ".java_pid" + pid;
String path = "/proc/" + pid + "/cwd/" + fn;
File f = new File(path);
if (!f.exists()) {
// Not found, so try /tmp
path = "/tmp/" + fn;
f = new File(path);
if (!f.exists()) {
return null; // not found
}
}
return path;
}
// On Solaris/Linux a simple handshake is used to start the attach mechanism
// if not already started. The client creates a .attach_pid file in the
// target VM's working directory (or /tmp), and the SIGQUIT handler checks
// for the file.
private File createAttachFile(int pid) throws IOException
{
String fn = ".attach_pid" + pid;
String path = "/proc/" + pid + "/cwd/" + fn;
File f = new File(path);
try {
f.createNewFile();
}
catch (IOException ignore) {
path = "/tmp/" + fn;
f = new File(path);
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 (UnsupportedEncodingException ignore) {
throw new InternalError();
}
write(fd, b, 0, b.length);
}
byte[] b = new byte[1];
b[0] = 0;
write(fd, b, 0, 1);
}
//-- native methods
static native boolean isLinuxThreads();
static native int getLinuxThreadsManager(int pid) throws IOException;
static native void sendQuitToChildrenOf(int pid) throws IOException;
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");
isLinuxThreads = isLinuxThreads();
}
}
