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