1 /*
2 * Copyright (c) 1995, 2012, 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
26 package java.lang;
27
28 import java.io.BufferedInputStream;
29 import java.io.BufferedOutputStream;
30 import java.io.ByteArrayInputStream;
31 import java.io.FileDescriptor;
32 import java.io.FileInputStream;
33 import java.io.FileOutputStream;
34 import java.io.IOException;
35 import java.io.InputStream;
36 import java.io.OutputStream;
37 import java.util.Arrays;
38 import java.util.concurrent.Executors;
39 import java.util.concurrent.Executor;
40 import java.util.concurrent.ThreadFactory;
41 import java.util.concurrent.TimeUnit;
42 import java.security.AccessController;
43 import static java.security.AccessController.doPrivileged;
44 import java.security.PrivilegedAction;
45 import java.security.PrivilegedActionException;
46 import java.security.PrivilegedExceptionAction;
47
48 /**
49 * java.lang.Process subclass in the UNIX environment.
50 *
51 * @author Mario Wolczko and Ross Knippel.
52 * @author Konstantin Kladko (ported to Linux)
53 * @author Martin Buchholz
54 */
55 final class UNIXProcess extends Process {
56 private static final sun.misc.JavaIOFileDescriptorAccess fdAccess
57 = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();
58
59 private final int pid;
60 private int exitcode;
61 private boolean hasExited;
62
63 private /* final */ OutputStream stdin;
64 private /* final */ InputStream stdout;
65 private /* final */ InputStream stderr;
66
67 private static String javahome;
68 private static String helperpath;
69
70 enum LaunchMechanism {
71 CLONE(1), FORK(2),
72 VFORK(3), SPAWN(4);
73
74 private int value;
75 LaunchMechanism(int x) {value = x;}
76 };
77
78 /* default is VFORK on Linux */
79 private static LaunchMechanism launchMechanism = LaunchMechanism.VFORK;
80
81 static {
82 AccessController.doPrivileged(new PrivilegedAction<Void>() {
83 public Void run() {
84 String javahome = System.getProperty("java.home");
85 String osarch = System.getProperty("os.arch");
86
87 helperpath = javahome + "/lib/" + osarch + "/jspawnhelper";
88 String s = System.getProperty("java.lang.useFork");
89 if (s != null) {
90 launchMechanism = LaunchMechanism.FORK;
91 }
92 return null;
93 }
94 });
95 }
96
97 /* this is for the reaping thread */
98 private native int waitForProcessExit(int pid);
99
100 /**
101 * Create a process. Depending on the mode flag, this is done by
102 * one of the following mechanisms.
103 * - fork(2) and exec(2)
104 * - clone(2) and exec(2)
105 * - vfork(2) and exec(2)
106 *
107 * @param fds an array of three file descriptors.
108 * Indexes 0, 1, and 2 correspond to standard input,
109 * standard output and standard error, respectively. On
110 * input, a value of -1 means to create a pipe to connect
111 * child and parent processes. On output, a value which
112 * is not -1 is the parent pipe fd corresponding to the
113 * pipe which has been created. An element of this array
114 * is -1 on input if and only if it is <em>not</em> -1 on
115 * output.
116 * @return the pid of the subprocess
117 */
118 private native int forkAndExec(int mode, byte[] prog,
119 byte[] argBlock, int argc,
120 byte[] envBlock, int envc,
121 byte[] dir,
122 int[] fds,
123 boolean redirectErrorStream)
124 throws IOException;
125
126 /**
127 * The thread factory used to create "process reaper" daemon threads.
128 */
129 private static class ProcessReaperThreadFactory implements ThreadFactory {
130 private final static ThreadGroup group = getRootThreadGroup();
131
132 private static ThreadGroup getRootThreadGroup() {
133 return doPrivileged(new PrivilegedAction<ThreadGroup> () {
134 public ThreadGroup run() {
135 ThreadGroup root = Thread.currentThread().getThreadGroup();
136 while (root.getParent() != null)
137 root = root.getParent();
138 return root;
139 }});
140 }
141
142 public Thread newThread(Runnable grimReaper) {
143 // Our thread stack requirement is quite modest.
144 Thread t = new Thread(group, grimReaper, "process reaper", 32768);
145 t.setDaemon(true);
146 // A small attempt (probably futile) to avoid priority inversion
147 t.setPriority(Thread.MAX_PRIORITY);
148 return t;
149 }
150 }
151
152 /**
153 * The thread pool of "process reaper" daemon threads.
154 */
155 private static final Executor processReaperExecutor =
156 doPrivileged(new PrivilegedAction<Executor>() {
157 public Executor run() {
158 return Executors.newCachedThreadPool
159 (new ProcessReaperThreadFactory());
160 }});
161
162 UNIXProcess(final byte[] prog,
163 final byte[] argBlock, final int argc,
164 final byte[] envBlock, final int envc,
165 final byte[] dir,
166 final int[] fds,
167 final boolean redirectErrorStream)
168 throws IOException {
169
170 pid = forkAndExec(launchMechanism.value,
171 prog,
172 argBlock, argc,
173 envBlock, envc,
174 dir,
175 fds,
176 redirectErrorStream);
177
178 try {
179 doPrivileged(new PrivilegedExceptionAction<Void>() {
180 public Void run() throws IOException {
181 initStreams(fds);
182 return null;
183 }});
184 } catch (PrivilegedActionException ex) {
185 throw (IOException) ex.getException();
186 }
187 }
188
189 static FileDescriptor newFileDescriptor(int fd) {
190 FileDescriptor fileDescriptor = new FileDescriptor();
191 fdAccess.set(fileDescriptor, fd);
192 return fileDescriptor;
193 }
194
195 void initStreams(int[] fds) throws IOException {
196 stdin = (fds[0] == -1) ?
197 ProcessBuilder.NullOutputStream.INSTANCE :
198 new ProcessPipeOutputStream(fds[0]);
199
200 stdout = (fds[1] == -1) ?
201 ProcessBuilder.NullInputStream.INSTANCE :
202 new ProcessPipeInputStream(fds[1]);
203
204 stderr = (fds[2] == -1) ?
205 ProcessBuilder.NullInputStream.INSTANCE :
206 new ProcessPipeInputStream(fds[2]);
207
208 processReaperExecutor.execute(new Runnable() {
209 public void run() {
210 int exitcode = waitForProcessExit(pid);
211 UNIXProcess.this.processExited(exitcode);
212 }});
213 }
214
215 void processExited(int exitcode) {
216 synchronized (this) {
217 this.exitcode = exitcode;
218 hasExited = true;
219 notifyAll();
220 }
221
222 if (stdout instanceof ProcessPipeInputStream)
223 ((ProcessPipeInputStream) stdout).processExited();
224
225 if (stderr instanceof ProcessPipeInputStream)
226 ((ProcessPipeInputStream) stderr).processExited();
227
228 if (stdin instanceof ProcessPipeOutputStream)
229 ((ProcessPipeOutputStream) stdin).processExited();
230 }
231
232 public OutputStream getOutputStream() {
233 return stdin;
234 }
235
236 public InputStream getInputStream() {
237 return stdout;
238 }
239
240 public InputStream getErrorStream() {
241 return stderr;
242 }
243
244 public synchronized int waitFor() throws InterruptedException {
245 while (!hasExited) {
246 wait();
247 }
248 return exitcode;
249 }
250
251 @Override
252 public synchronized boolean waitFor(long timeout, TimeUnit unit)
253 throws InterruptedException
254 {
255 if (hasExited) return true;
256 if (timeout <= 0) return false;
257
258 long timeoutAsNanos = unit.toNanos(timeout);
259 long startTime = System.nanoTime();
260 long rem = timeoutAsNanos;
261
262 while (!hasExited && (rem > 0)) {
263 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
264 rem = timeoutAsNanos - (System.nanoTime() - startTime);
265 }
266 return hasExited;
267 }
268
269 public synchronized int exitValue() {
270 if (!hasExited) {
271 throw new IllegalThreadStateException("process hasn't exited");
272 }
273 return exitcode;
274 }
275
276 private static native void destroyProcess(int pid, boolean force);
277 private void destroy(boolean force) {
278 // There is a risk that pid will be recycled, causing us to
279 // kill the wrong process! So we only terminate processes
280 // that appear to still be running. Even with this check,
281 // there is an unavoidable race condition here, but the window
282 // is very small, and OSes try hard to not recycle pids too
283 // soon, so this is quite safe.
284 synchronized (this) {
285 if (!hasExited)
286 destroyProcess(pid, force);
287 }
288 try { stdin.close(); } catch (IOException ignored) {}
289 try { stdout.close(); } catch (IOException ignored) {}
290 try { stderr.close(); } catch (IOException ignored) {}
291 }
292
293 public void destroy() {
294 destroy(false);
295 }
296
297 @Override
298 public Process destroyForcibly() {
299 destroy(true);
300 return this;
301 }
302
303 @Override
304 public synchronized boolean isAlive() {
305 return !hasExited;
306 }
307
308 /* This routine initializes JNI field offsets for the class */
309 private static native void initIDs();
310
311 static {
312 initIDs();
313 }
314
315 /**
316 * A buffered input stream for a subprocess pipe file descriptor
317 * that allows the underlying file descriptor to be reclaimed when
318 * the process exits, via the processExited hook.
319 *
320 * This is tricky because we do not want the user-level InputStream to be
321 * closed until the user invokes close(), and we need to continue to be
322 * able to read any buffered data lingering in the OS pipe buffer.
323 */
324 static class ProcessPipeInputStream extends BufferedInputStream {
325 ProcessPipeInputStream(int fd) {
326 super(new FileInputStream(newFileDescriptor(fd)));
327 }
328
329 private static byte[] drainInputStream(InputStream in)
330 throws IOException {
331 if (in == null) return null;
332 int n = 0;
333 int j;
334 byte[] a = null;
335 while ((j = in.available()) > 0) {
336 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
337 n += in.read(a, n, j);
338 }
339 return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
340 }
341
342 /** Called by the process reaper thread when the process exits. */
343 synchronized void processExited() {
344 // Most BufferedInputStream methods are synchronized, but close()
345 // is not, and so we have to handle concurrent racing close().
346 try {
347 InputStream in = this.in;
348 if (in != null) {
349 byte[] stragglers = drainInputStream(in);
350 in.close();
351 this.in = (stragglers == null) ?
352 ProcessBuilder.NullInputStream.INSTANCE :
353 new ByteArrayInputStream(stragglers);
354 if (buf == null) // asynchronous close()?
355 this.in = null;
356 }
357 } catch (IOException ignored) {
358 // probably an asynchronous close().
359 }
360 }
361 }
362
363 /**
364 * A buffered output stream for a subprocess pipe file descriptor
365 * that allows the underlying file descriptor to be reclaimed when
366 * the process exits, via the processExited hook.
367 */
368 static class ProcessPipeOutputStream extends BufferedOutputStream {
369 ProcessPipeOutputStream(int fd) {
370 super(new FileOutputStream(newFileDescriptor(fd)));
371 }
372
373 /** Called by the process reaper thread when the process exits. */
374 synchronized void processExited() {
375 OutputStream out = this.out;
376 if (out != null) {
377 try {
378 out.close();
379 } catch (IOException ignored) {
380 // We know of no reason to get an IOException, but if
381 // we do, there's nothing else to do but carry on.
382 }
383 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
384 }
385 }
386 }
387 }