1 /*
2 * Copyright (c) 1995, 2013, 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 * @author Volker Simonis (ported to AIX)
55 */
56 final class UNIXProcess extends Process {
57 private static final sun.misc.JavaIOFileDescriptorAccess fdAccess
58 = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();
59
60 private final int pid;
61 private int exitcode;
62 private boolean hasExited;
63
64 private /* final */ OutputStream stdin;
65 private /* final */ InputStream stdout;
66 private /* final */ InputStream stderr;
67
68 private static enum LaunchMechanism {
69 FORK(1),
70 POSIX_SPAWN(2);
71
72 private int value;
73 LaunchMechanism(int x) {value = x;}
74 };
75
76 /* On AIX, the default is to spawn */
77 private static final LaunchMechanism launchMechanism;
78 private static byte[] helperpath;
79
80 private static byte[] toCString(String s) {
81 if (s == null)
82 return null;
83 byte[] bytes = s.getBytes();
84 byte[] result = new byte[bytes.length + 1];
85 System.arraycopy(bytes, 0,
86 result, 0,
87 bytes.length);
88 result[result.length-1] = (byte)0;
89 return result;
90 }
91
92 static {
93 launchMechanism = AccessController.doPrivileged(
94 new PrivilegedAction<LaunchMechanism>()
95 {
96 public LaunchMechanism run() {
97 String javahome = System.getProperty("java.home");
98 String osArch = System.getProperty("os.arch");
99
100 helperpath = toCString(javahome + "/lib/" + osArch + "/jspawnhelper");
101 String s = System.getProperty(
102 "jdk.lang.Process.launchMechanism", "posix_spawn");
103
104 try {
105 return LaunchMechanism.valueOf(s.toUpperCase());
106 } catch (IllegalArgumentException e) {
107 throw new Error(s + " is not a supported " +
108 "process launch mechanism on this platform.");
109 }
110 }
111 });
112 }
113
114 /* this is for the reaping thread */
115 private native int waitForProcessExit(int pid);
116
117 /**
118 * Create a process. Depending on the mode flag, this is done by
119 * one of the following mechanisms.
120 * - fork(2) and exec(2)
121 * - clone(2) and exec(2)
122 * - vfork(2) and exec(2)
123 *
124 * @param fds an array of three file descriptors.
125 * Indexes 0, 1, and 2 correspond to standard input,
126 * standard output and standard error, respectively. On
127 * input, a value of -1 means to create a pipe to connect
128 * child and parent processes. On output, a value which
129 * is not -1 is the parent pipe fd corresponding to the
130 * pipe which has been created. An element of this array
131 * is -1 on input if and only if it is <em>not</em> -1 on
132 * output.
133 * @return the pid of the subprocess
134 */
135 private native int forkAndExec(int mode, byte[] helperpath,
136 byte[] prog,
137 byte[] argBlock, int argc,
138 byte[] envBlock, int envc,
139 byte[] dir,
140 int[] fds,
141 boolean redirectErrorStream)
142 throws IOException;
143
144 /**
145 * The thread factory used to create "process reaper" daemon threads.
146 */
147 private static class ProcessReaperThreadFactory implements ThreadFactory {
148 private final static ThreadGroup group = getRootThreadGroup();
149
150 private static ThreadGroup getRootThreadGroup() {
151 return doPrivileged(new PrivilegedAction<ThreadGroup> () {
152 public ThreadGroup run() {
153 ThreadGroup root = Thread.currentThread().getThreadGroup();
154 while (root.getParent() != null)
155 root = root.getParent();
156 return root;
157 }});
158 }
159
160 public Thread newThread(Runnable grimReaper) {
161 // Our thread stack requirement is quite modest.
162 Thread t = new Thread(group, grimReaper, "process reaper", 32768);
163 t.setDaemon(true);
164 // A small attempt (probably futile) to avoid priority inversion
165 t.setPriority(Thread.MAX_PRIORITY);
166 return t;
167 }
168 }
169
170 /**
171 * The thread pool of "process reaper" daemon threads.
172 */
173 private static final Executor processReaperExecutor =
174 doPrivileged(new PrivilegedAction<Executor>() {
175 public Executor run() {
176 return Executors.newCachedThreadPool
177 (new ProcessReaperThreadFactory());
178 }});
179
180 UNIXProcess(final byte[] prog,
181 final byte[] argBlock, final int argc,
182 final byte[] envBlock, final int envc,
183 final byte[] dir,
184 final int[] fds,
185 final boolean redirectErrorStream)
186 throws IOException {
187
188 pid = forkAndExec(launchMechanism.value,
189 helperpath,
190 prog,
191 argBlock, argc,
192 envBlock, envc,
193 dir,
194 fds,
195 redirectErrorStream);
196
197 try {
198 doPrivileged(new PrivilegedExceptionAction<Void>() {
199 public Void run() throws IOException {
200 initStreams(fds);
201 return null;
202 }});
203 } catch (PrivilegedActionException ex) {
204 throw (IOException) ex.getException();
205 }
206 }
207
208 static FileDescriptor newFileDescriptor(int fd) {
209 FileDescriptor fileDescriptor = new FileDescriptor();
210 fdAccess.set(fileDescriptor, fd);
211 return fileDescriptor;
212 }
213
214 void initStreams(int[] fds) throws IOException {
215 stdin = (fds[0] == -1) ?
216 ProcessBuilder.NullOutputStream.INSTANCE :
217 new ProcessPipeOutputStream(fds[0]);
218
219 stdout = (fds[1] == -1) ?
220 ProcessBuilder.NullInputStream.INSTANCE :
221 new ProcessPipeInputStream(fds[1]);
222
223 stderr = (fds[2] == -1) ?
224 ProcessBuilder.NullInputStream.INSTANCE :
225 new ProcessPipeInputStream(fds[2]);
226
227 processReaperExecutor.execute(new Runnable() {
228 public void run() {
229 int exitcode = waitForProcessExit(pid);
230 UNIXProcess.this.processExited(exitcode);
231 }});
232 }
233
234 void processExited(int exitcode) {
235 synchronized (this) {
236 this.exitcode = exitcode;
237 hasExited = true;
238 notifyAll();
239 }
240
241 if (stdout instanceof ProcessPipeInputStream)
242 ((ProcessPipeInputStream) stdout).processExited();
243
244 if (stderr instanceof ProcessPipeInputStream)
245 ((ProcessPipeInputStream) stderr).processExited();
246
247 if (stdin instanceof ProcessPipeOutputStream)
248 ((ProcessPipeOutputStream) stdin).processExited();
249 }
250
251 public OutputStream getOutputStream() {
252 return stdin;
253 }
254
255 public InputStream getInputStream() {
256 return stdout;
257 }
258
259 public InputStream getErrorStream() {
260 return stderr;
261 }
262
263 public synchronized int waitFor() throws InterruptedException {
264 while (!hasExited) {
265 wait();
266 }
267 return exitcode;
268 }
269
270 @Override
271 public synchronized boolean waitFor(long timeout, TimeUnit unit)
272 throws InterruptedException
273 {
274 if (hasExited) return true;
275 if (timeout <= 0) return false;
276
277 long timeoutAsNanos = unit.toNanos(timeout);
278 long startTime = System.nanoTime();
279 long rem = timeoutAsNanos;
280
281 while (!hasExited && (rem > 0)) {
282 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
283 rem = timeoutAsNanos - (System.nanoTime() - startTime);
284 }
285 return hasExited;
286 }
287
288 public synchronized int exitValue() {
289 if (!hasExited) {
290 throw new IllegalThreadStateException("process hasn't exited");
291 }
292 return exitcode;
293 }
294
295 private static native void destroyProcess(int pid, boolean force);
296 private void destroy(boolean force) {
297 // There is a risk that pid will be recycled, causing us to
298 // kill the wrong process! So we only terminate processes
299 // that appear to still be running. Even with this check,
300 // there is an unavoidable race condition here, but the window
301 // is very small, and OSes try hard to not recycle pids too
302 // soon, so this is quite safe.
303 synchronized (this) {
304 if (!hasExited)
305 destroyProcess(pid, force);
306 }
307 try { stdin.close(); } catch (IOException ignored) {}
308 try { stdout.close(); } catch (IOException ignored) {}
309 try { stderr.close(); } catch (IOException ignored) {}
310 }
311
312 public void destroy() {
313 destroy(false);
314 }
315
316 @Override
317 public Process destroyForcibly() {
318 destroy(true);
319 return this;
320 }
321
322 @Override
323 public synchronized boolean isAlive() {
324 return !hasExited;
325 }
326
327 private static native void init();
328
329 static {
330 init();
331 }
332
333 /**
334 * A buffered input stream for a subprocess pipe file descriptor
335 * that allows the underlying file descriptor to be reclaimed when
336 * the process exits, via the processExited hook.
337 *
338 * This is tricky because we do not want the user-level InputStream to be
339 * closed until the user invokes close(), and we need to continue to be
340 * able to read any buffered data lingering in the OS pipe buffer.
341 */
342 static class ProcessPipeInputStream extends BufferedInputStream {
343 private final Object closeLock = new Object();
344
345 ProcessPipeInputStream(int fd) {
346 super(new FileInputStream(newFileDescriptor(fd)));
347 }
348
349 private InputStream drainInputStream(InputStream in)
350 throws IOException {
351 int n = 0;
352 int j;
353 byte[] a = null;
354 synchronized (closeLock) {
355 if (buf == null) // asynchronous close()?
356 return null; // discard
357 j = in.available();
358 }
359 while (j > 0) {
360 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
361 synchronized (closeLock) {
362 if (buf == null) // asynchronous close()?
363 return null; // discard
364 n += in.read(a, n, j);
365 j = in.available();
366 }
367 }
368 return (a == null) ?
369 ProcessBuilder.NullInputStream.INSTANCE :
370 new ByteArrayInputStream(n == a.length ? a : Arrays.copyOf(a, n));
371 }
372
373 /** Called by the process reaper thread when the process exits. */
374 synchronized void processExited() {
375 try {
376 InputStream in = this.in;
377 if (in != null) {
378 InputStream stragglers = drainInputStream(in);
379 in.close();
380 this.in = stragglers;
381 }
382 } catch (IOException ignored) { }
383 }
384
385 @Override
386 public void close() throws IOException {
387 // BufferedInputStream#close() is not synchronized unlike most other methods.
388 // Synchronizing helps avoid racing with drainInputStream().
389 synchronized (closeLock) {
390 super.close();
391 }
392 }
393 }
394
395 /**
396 * A buffered output stream for a subprocess pipe file descriptor
397 * that allows the underlying file descriptor to be reclaimed when
398 * the process exits, via the processExited hook.
399 */
400 static class ProcessPipeOutputStream extends BufferedOutputStream {
401 ProcessPipeOutputStream(int fd) {
402 super(new FileOutputStream(newFileDescriptor(fd)));
403 }
404
405 /** Called by the process reaper thread when the process exits. */
406 synchronized void processExited() {
407 OutputStream out = this.out;
408 if (out != null) {
409 try {
410 out.close();
411 } catch (IOException ignored) {
412 // We know of no reason to get an IOException, but if
413 // we do, there's nothing else to do but carry on.
414 }
415 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
416 }
417 }
418 }
419 }