1 /*
2 * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package sun.tools.attach;
26
27 import com.sun.tools.attach.AttachOperationFailedException;
28 import com.sun.tools.attach.AgentLoadException;
29 import com.sun.tools.attach.AttachNotSupportedException;
30 import com.sun.tools.attach.spi.AttachProvider;
31
32 import java.io.InputStream;
33 import java.io.IOException;
34 import java.io.File;
35
36 /*
37 * Linux implementation of HotSpotVirtualMachine
38 */
39 public class VirtualMachineImpl extends HotSpotVirtualMachine {
40 // "/tmp" is used as a global well-known location for the files
41 // .java_pid<pid>. and .attach_pid<pid>. It is important that this
42 // location is the same for all processes, otherwise the tools
43 // will not be able to find all Hotspot processes.
44 // Any changes to this needs to be synchronized with HotSpot.
45 private static final String tmpdir = "/tmp";
46
47 // The patch to the socket file created by the target VM
48 String path;
49
50 /**
51 * Attaches to the target VM
52 */
53 VirtualMachineImpl(AttachProvider provider, String vmid)
54 throws AttachNotSupportedException, IOException
55 {
56 super(provider, vmid);
57
58 // This provider only understands pids
59 int pid;
60 try {
61 pid = Integer.parseInt(vmid);
62 } catch (NumberFormatException x) {
63 throw new AttachNotSupportedException("Invalid process identifier");
64 }
65
66 // Find the socket file. If not found then we attempt to start the
67 // attach mechanism in the target VM by sending it a QUIT signal.
68 // Then we attempt to find the socket file again.
69 path = findSocketFile(pid);
70 if (path == null) {
71 File f = createAttachFile(pid);
72 try {
73 sendQuitTo(pid);
74
75 // give the target VM time to start the attach mechanism
76 final int delay_step = 100;
77 final long timeout = attachTimeout();
78 long time_spend = 0;
79 long delay = 0;
80 do {
81 // Increase timeout on each attempt to reduce polling
82 delay += delay_step;
83 try {
84 Thread.sleep(delay);
85 } catch (InterruptedException x) { }
86 path = findSocketFile(pid);
87
88 time_spend += delay;
89 if (time_spend > timeout/2 && path == null) {
90 // Send QUIT again to give target VM the last chance to react
91 sendQuitTo(pid);
92 }
93 } while (time_spend <= timeout && path == null);
94 if (path == null) {
95 throw new AttachNotSupportedException(
96 String.format("Unable to open socket file: target process %d not responding within %dms or HotSpot VM not loaded", pid, time_spend));
97 }
98 } finally {
99 f.delete();
100 }
101 }
102
103 // Check that the file owner/permission to avoid attaching to
104 // bogus process
105 checkPermissions(path);
106
107 // Check that we can connect to the process
108 // - this ensures we throw the permission denied error now rather than
109 // later when we attempt to enqueue a command.
110 int s = socket();
111 try {
112 connect(s, path);
113 } finally {
114 close(s);
115 }
116 }
117
118 /**
119 * Detach from the target VM
120 */
121 public void detach() throws IOException {
122 synchronized (this) {
123 if (this.path != null) {
124 this.path = null;
125 }
126 }
127 }
128
129 // protocol version
130 private final static String PROTOCOL_VERSION = "1";
131
132 // known errors
133 private final static int ATTACH_ERROR_BADVERSION = 101;
134
135 /**
136 * Execute the given command in the target VM.
137 */
138 InputStream execute(String cmd, Object ... args) throws AgentLoadException, IOException {
139 assert args.length <= 3; // includes null
140
141 // did we detach?
142 String p;
143 synchronized (this) {
144 if (this.path == null) {
145 throw new IOException("Detached from target VM");
146 }
147 p = this.path;
148 }
149
150 // create UNIX socket
151 int s = socket();
152
153 // connect to target VM
154 try {
155 connect(s, p);
156 } catch (IOException x) {
157 close(s);
158 throw x;
159 }
160
161 IOException ioe = null;
162
163 // connected - write request
164 // <ver> <cmd> <args...>
165 try {
166 writeString(s, PROTOCOL_VERSION);
167 writeString(s, cmd);
168
169 for (int i=0; i<3; i++) {
170 if (i < args.length && args[i] != null) {
171 writeString(s, (String)args[i]);
172 } else {
173 writeString(s, "");
174 }
175 }
176 } catch (IOException x) {
177 ioe = x;
178 }
179
180
181 // Create an input stream to read reply
182 SocketInputStream sis = new SocketInputStream(s);
183
184 // Read the command completion status
185 int completionStatus;
186 try {
187 completionStatus = readInt(sis);
188 } catch (IOException x) {
189 sis.close();
190 if (ioe != null) {
191 throw ioe;
192 } else {
193 throw x;
194 }
195 }
196
197 if (completionStatus != 0) {
198 // read from the stream and use that as the error message
199 String message = readErrorMessage(sis);
200 sis.close();
201
202 // In the event of a protocol mismatch then the target VM
203 // returns a known error so that we can throw a reasonable
204 // error.
205 if (completionStatus == ATTACH_ERROR_BADVERSION) {
206 throw new IOException("Protocol mismatch with target VM");
207 }
208
209 // Special-case the "load" command so that the right exception is
210 // thrown.
211 if (cmd.equals("load")) {
212 throw new AgentLoadException("Failed to load agent library");
213 } else {
214 if (message == null) {
215 throw new AttachOperationFailedException("Command failed in target VM");
216 } else {
217 throw new AttachOperationFailedException(message);
218 }
219 }
220 }
221
222 // Return the input stream so that the command output can be read
223 return sis;
224 }
225
226 /*
227 * InputStream for the socket connection to get target VM
228 */
229 private class SocketInputStream extends InputStream {
230 int s;
231
232 public SocketInputStream(int s) {
233 this.s = s;
234 }
235
236 public synchronized int read() throws IOException {
237 byte b[] = new byte[1];
238 int n = this.read(b, 0, 1);
239 if (n == 1) {
240 return b[0] & 0xff;
241 } else {
242 return -1;
243 }
244 }
245
246 public synchronized int read(byte[] bs, int off, int len) throws IOException {
247 if ((off < 0) || (off > bs.length) || (len < 0) ||
248 ((off + len) > bs.length) || ((off + len) < 0)) {
249 throw new IndexOutOfBoundsException();
250 } else if (len == 0)
251 return 0;
252
253 return VirtualMachineImpl.read(s, bs, off, len);
254 }
255
256 public void close() throws IOException {
257 VirtualMachineImpl.close(s);
258 }
259 }
260
261 // Return the socket file for the given process.
262 private String findSocketFile(int pid) {
263 File f = new File(tmpdir, ".java_pid" + pid);
264 if (!f.exists()) {
265 return null;
266 }
267 return f.getPath();
268 }
269
270 // On Solaris/Linux a simple handshake is used to start the attach mechanism
271 // if not already started. The client creates a .attach_pid<pid> file in the
272 // target VM's working directory (or temp directory), and the SIGQUIT handler
273 // checks for the file.
274 private File createAttachFile(int pid) throws IOException {
275 String fn = ".attach_pid" + pid;
276 String path = "/proc/" + pid + "/cwd/" + fn;
277 File f = new File(path);
278 try {
279 f.createNewFile();
280 } catch (IOException x) {
281 f = new File(tmpdir, fn);
282 f.createNewFile();
283 }
284 return f;
285 }
286
287 /*
288 * Write/sends the given to the target VM. String is transmitted in
289 * UTF-8 encoding.
290 */
291 private void writeString(int fd, String s) throws IOException {
292 if (s.length() > 0) {
293 byte b[];
294 try {
295 b = s.getBytes("UTF-8");
296 } catch (java.io.UnsupportedEncodingException x) {
297 throw new InternalError(x);
298 }
299 VirtualMachineImpl.write(fd, b, 0, b.length);
300 }
301 byte b[] = new byte[1];
302 b[0] = 0;
303 write(fd, b, 0, 1);
304 }
305
306
307 //-- native methods
308
309 static native boolean isLinuxThreads();
310
311 static native int getLinuxThreadsManager(int pid) throws IOException;
312
313 static native void sendQuitToChildrenOf(int pid) throws IOException;
314
315 static native void sendQuitTo(int pid) throws IOException;
316
317 static native void checkPermissions(String path) throws IOException;
318
319 static native int socket() throws IOException;
320
321 static native void connect(int fd, String path) throws IOException;
322
323 static native void close(int fd) throws IOException;
324
325 static native int read(int fd, byte buf[], int off, int bufLen) throws IOException;
326
327 static native void write(int fd, byte buf[], int off, int bufLen) throws IOException;
328
329 static {
330 System.loadLibrary("attach");
331 }
332 }