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 fork(1),
72 vfork(3);
73
74 private int value;
75 LaunchMechanism(int x) {value = x;}
76 };
77
78 /* default is VFORK on Linux */
79 private static LaunchMechanism launchMechanism;
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(
89 "jdk.lang.Process.launchMechanism", "vfork");
90
91 try {
92 launchMechanism = LaunchMechanism.valueOf(s);
93 } catch (IllegalArgumentException e) {
94 throw new Error(s + " is not a supported " +
95 "process launch mechanism on this platform.");
96 }
97 return null;
98 }
99 });
100 }
101
102 /* this is for the reaping thread */
103 private native int waitForProcessExit(int pid);
104
105 /**
106 * Create a process. Depending on the mode flag, this is done by
107 * one of the following mechanisms.
108 * - fork(2) and exec(2)
109 * - clone(2) and exec(2)
110 * - vfork(2) and exec(2)
111 *
112 * @param fds an array of three file descriptors.
113 * Indexes 0, 1, and 2 correspond to standard input,
114 * standard output and standard error, respectively. On
115 * input, a value of -1 means to create a pipe to connect
116 * child and parent processes. On output, a value which
117 * is not -1 is the parent pipe fd corresponding to the
118 * pipe which has been created. An element of this array
119 * is -1 on input if and only if it is <em>not</em> -1 on
120 * output.
121 * @return the pid of the subprocess
122 */
123 private native int forkAndExec(int mode, byte[] prog,
124 byte[] argBlock, int argc,
125 byte[] envBlock, int envc,
126 byte[] dir,
127 int[] fds,
128 boolean redirectErrorStream)
129 throws IOException;
130
131 /**
132 * The thread factory used to create "process reaper" daemon threads.
133 */
134 private static class ProcessReaperThreadFactory implements ThreadFactory {
135 private final static ThreadGroup group = getRootThreadGroup();
136
137 private static ThreadGroup getRootThreadGroup() {
138 return doPrivileged(new PrivilegedAction<ThreadGroup> () {
139 public ThreadGroup run() {
140 ThreadGroup root = Thread.currentThread().getThreadGroup();
141 while (root.getParent() != null)
142 root = root.getParent();
143 return root;
144 }});
145 }
146
147 public Thread newThread(Runnable grimReaper) {
148 // Our thread stack requirement is quite modest.
149 Thread t = new Thread(group, grimReaper, "process reaper", 32768);
150 t.setDaemon(true);
151 // A small attempt (probably futile) to avoid priority inversion
152 t.setPriority(Thread.MAX_PRIORITY);
153 return t;
154 }
155 }
156
157 /**
158 * The thread pool of "process reaper" daemon threads.
159 */
160 private static final Executor processReaperExecutor =
161 doPrivileged(new PrivilegedAction<Executor>() {
162 public Executor run() {
163 return Executors.newCachedThreadPool
164 (new ProcessReaperThreadFactory());
165 }});
166
167 UNIXProcess(final byte[] prog,
168 final byte[] argBlock, final int argc,
169 final byte[] envBlock, final int envc,
170 final byte[] dir,
171 final int[] fds,
172 final boolean redirectErrorStream)
173 throws IOException {
174
175 pid = forkAndExec(launchMechanism.value,
176 prog,
177 argBlock, argc,
178 envBlock, envc,
179 dir,
180 fds,
181 redirectErrorStream);
182
183 try {
184 doPrivileged(new PrivilegedExceptionAction<Void>() {
185 public Void run() throws IOException {
186 initStreams(fds);
187 return null;
188 }});
189 } catch (PrivilegedActionException ex) {
190 throw (IOException) ex.getException();
191 }
192 }
193
194 static FileDescriptor newFileDescriptor(int fd) {
195 FileDescriptor fileDescriptor = new FileDescriptor();
196 fdAccess.set(fileDescriptor, fd);
197 return fileDescriptor;
198 }
199
200 void initStreams(int[] fds) throws IOException {
201 stdin = (fds[0] == -1) ?
202 ProcessBuilder.NullOutputStream.INSTANCE :
203 new ProcessPipeOutputStream(fds[0]);
204
205 stdout = (fds[1] == -1) ?
206 ProcessBuilder.NullInputStream.INSTANCE :
207 new ProcessPipeInputStream(fds[1]);
208
209 stderr = (fds[2] == -1) ?
210 ProcessBuilder.NullInputStream.INSTANCE :
211 new ProcessPipeInputStream(fds[2]);
212
213 processReaperExecutor.execute(new Runnable() {
214 public void run() {
215 int exitcode = waitForProcessExit(pid);
216 UNIXProcess.this.processExited(exitcode);
217 }});
218 }
219
220 void processExited(int exitcode) {
221 synchronized (this) {
222 this.exitcode = exitcode;
223 hasExited = true;
224 notifyAll();
225 }
226
227 if (stdout instanceof ProcessPipeInputStream)
228 ((ProcessPipeInputStream) stdout).processExited();
229
230 if (stderr instanceof ProcessPipeInputStream)
231 ((ProcessPipeInputStream) stderr).processExited();
232
233 if (stdin instanceof ProcessPipeOutputStream)
234 ((ProcessPipeOutputStream) stdin).processExited();
235 }
236
237 public OutputStream getOutputStream() {
238 return stdin;
239 }
240
241 public InputStream getInputStream() {
242 return stdout;
243 }
244
245 public InputStream getErrorStream() {
246 return stderr;
247 }
248
249 public synchronized int waitFor() throws InterruptedException {
250 while (!hasExited) {
251 wait();
252 }
253 return exitcode;
254 }
255
256 @Override
257 public synchronized boolean waitFor(long timeout, TimeUnit unit)
258 throws InterruptedException
259 {
260 if (hasExited) return true;
261 if (timeout <= 0) return false;
262
263 long timeoutAsNanos = unit.toNanos(timeout);
264 long startTime = System.nanoTime();
265 long rem = timeoutAsNanos;
266
267 while (!hasExited && (rem > 0)) {
268 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
269 rem = timeoutAsNanos - (System.nanoTime() - startTime);
270 }
271 return hasExited;
272 }
273
274 public synchronized int exitValue() {
275 if (!hasExited) {
276 throw new IllegalThreadStateException("process hasn't exited");
277 }
278 return exitcode;
279 }
280
281 private static native void destroyProcess(int pid, boolean force);
282 private void destroy(boolean force) {
283 // There is a risk that pid will be recycled, causing us to
284 // kill the wrong process! So we only terminate processes
285 // that appear to still be running. Even with this check,
286 // there is an unavoidable race condition here, but the window
287 // is very small, and OSes try hard to not recycle pids too
288 // soon, so this is quite safe.
289 synchronized (this) {
290 if (!hasExited)
291 destroyProcess(pid, force);
292 }
293 try { stdin.close(); } catch (IOException ignored) {}
294 try { stdout.close(); } catch (IOException ignored) {}
295 try { stderr.close(); } catch (IOException ignored) {}
296 }
297
298 public void destroy() {
299 destroy(false);
300 }
301
302 @Override
303 public Process destroyForcibly() {
304 destroy(true);
305 return this;
306 }
307
308 @Override
309 public synchronized boolean isAlive() {
310 return !hasExited;
311 }
312
313 private static native void init();
314
315 static {
316 init();
317 }
318
319 /**
320 * A buffered input stream for a subprocess pipe file descriptor
321 * that allows the underlying file descriptor to be reclaimed when
322 * the process exits, via the processExited hook.
323 *
324 * This is tricky because we do not want the user-level InputStream to be
325 * closed until the user invokes close(), and we need to continue to be
326 * able to read any buffered data lingering in the OS pipe buffer.
327 */
328 static class ProcessPipeInputStream extends BufferedInputStream {
329 ProcessPipeInputStream(int fd) {
330 super(new FileInputStream(newFileDescriptor(fd)));
331 }
332
333 private static byte[] drainInputStream(InputStream in)
334 throws IOException {
335 if (in == null) return null;
336 int n = 0;
337 int j;
338 byte[] a = null;
339 while ((j = in.available()) > 0) {
340 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
341 n += in.read(a, n, j);
342 }
343 return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
344 }
345
346 /** Called by the process reaper thread when the process exits. */
347 synchronized void processExited() {
348 // Most BufferedInputStream methods are synchronized, but close()
349 // is not, and so we have to handle concurrent racing close().
350 try {
351 InputStream in = this.in;
352 if (in != null) {
353 byte[] stragglers = drainInputStream(in);
354 in.close();
355 this.in = (stragglers == null) ?
356 ProcessBuilder.NullInputStream.INSTANCE :
357 new ByteArrayInputStream(stragglers);
358 if (buf == null) // asynchronous close()?
359 this.in = null;
360 }
361 } catch (IOException ignored) {
362 // probably an asynchronous close().
363 }
364 }
365 }
366
367 /**
368 * A buffered output stream for a subprocess pipe file descriptor
369 * that allows the underlying file descriptor to be reclaimed when
370 * the process exits, via the processExited hook.
371 */
372 static class ProcessPipeOutputStream extends BufferedOutputStream {
373 ProcessPipeOutputStream(int fd) {
374 super(new FileOutputStream(newFileDescriptor(fd)));
375 }
376
377 /** Called by the process reaper thread when the process exits. */
378 synchronized void processExited() {
379 OutputStream out = this.out;
380 if (out != null) {
381 try {
382 out.close();
383 } catch (IOException ignored) {
384 // We know of no reason to get an IOException, but if
385 // we do, there's nothing else to do but carry on.
386 }
387 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
388 }
389 }
390 }
391 }