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 */
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 VFORK(3);
70
71 private int value;
72 LaunchMechanism(int x) {value = x;}
73 };
74
75 /* default is VFORK on Linux */
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 String osArch = System.getProperty("os.arch");
98
99 helperpath = toCString(javahome + "/lib/" + osArch + "/jspawnhelper");
100 String s = System.getProperty(
101 "jdk.lang.Process.launchMechanism", "vfork");
102
103 try {
104 return LaunchMechanism.valueOf(s.toUpperCase());
105 } catch (IllegalArgumentException e) {
106 throw new Error(s + " is not a supported " +
107 "process launch mechanism on this platform.");
108 }
109 }
110 });
111 }
112
113 /* this is for the reaping thread */
114 private native int waitForProcessExit(int pid);
115
116 /**
117 * Create a process. Depending on the mode flag, this is done by
118 * one of the following mechanisms.
119 * - fork(2) and exec(2)
120 * - clone(2) and exec(2)
121 * - vfork(2) and exec(2)
122 *
123 * @param fds an array of three file descriptors.
124 * Indexes 0, 1, and 2 correspond to standard input,
125 * standard output and standard error, respectively. On
126 * input, a value of -1 means to create a pipe to connect
127 * child and parent processes. On output, a value which
128 * is not -1 is the parent pipe fd corresponding to the
129 * pipe which has been created. An element of this array
130 * is -1 on input if and only if it is <em>not</em> -1 on
131 * output.
132 * @return the pid of the subprocess
133 */
134 private native int forkAndExec(int mode, byte[] helperpath,
135 byte[] prog,
136 byte[] argBlock, int argc,
137 byte[] envBlock, int envc,
138 byte[] dir,
139 int[] fds,
140 boolean redirectErrorStream)
141 throws IOException;
142
143 /**
144 * The thread factory used to create "process reaper" daemon threads.
145 */
146 private static class ProcessReaperThreadFactory implements ThreadFactory {
147 private final static ThreadGroup group = getRootThreadGroup();
148
149 private static ThreadGroup getRootThreadGroup() {
150 return doPrivileged(new PrivilegedAction<ThreadGroup> () {
151 public ThreadGroup run() {
152 ThreadGroup root = Thread.currentThread().getThreadGroup();
153 while (root.getParent() != null)
154 root = root.getParent();
155 return root;
156 }});
157 }
158
159 public Thread newThread(Runnable grimReaper) {
160 // Our thread stack requirement is quite modest.
161 Thread t = new Thread(group, grimReaper, "process reaper", 32768);
162 t.setDaemon(true);
163 // A small attempt (probably futile) to avoid priority inversion
164 t.setPriority(Thread.MAX_PRIORITY);
165 return t;
166 }
167 }
168
169 /**
170 * The thread pool of "process reaper" daemon threads.
171 */
172 private static final Executor processReaperExecutor =
173 doPrivileged(new PrivilegedAction<Executor>() {
174 public Executor run() {
175 return Executors.newCachedThreadPool
176 (new ProcessReaperThreadFactory());
177 }});
178
179 UNIXProcess(final byte[] prog,
180 final byte[] argBlock, final int argc,
181 final byte[] envBlock, final int envc,
182 final byte[] dir,
183 final int[] fds,
184 final boolean redirectErrorStream)
185 throws IOException {
186
187 pid = forkAndExec(launchMechanism.value,
188 helperpath,
189 prog,
190 argBlock, argc,
191 envBlock, envc,
192 dir,
193 fds,
194 redirectErrorStream);
195
196 try {
197 doPrivileged(new PrivilegedExceptionAction<Void>() {
198 public Void run() throws IOException {
199 initStreams(fds);
200 return null;
201 }});
202 } catch (PrivilegedActionException ex) {
203 throw (IOException) ex.getException();
204 }
205 }
206
207 static FileDescriptor newFileDescriptor(int fd) {
208 FileDescriptor fileDescriptor = new FileDescriptor();
209 fdAccess.set(fileDescriptor, fd);
210 return fileDescriptor;
211 }
212
213 void initStreams(int[] fds) throws IOException {
214 stdin = (fds[0] == -1) ?
215 ProcessBuilder.NullOutputStream.INSTANCE :
216 new ProcessPipeOutputStream(fds[0]);
217
218 stdout = (fds[1] == -1) ?
219 ProcessBuilder.NullInputStream.INSTANCE :
220 new ProcessPipeInputStream(fds[1]);
221
222 stderr = (fds[2] == -1) ?
223 ProcessBuilder.NullInputStream.INSTANCE :
224 new ProcessPipeInputStream(fds[2]);
225
226 processReaperExecutor.execute(new Runnable() {
227 public void run() {
228 int exitcode = waitForProcessExit(pid);
229 UNIXProcess.this.processExited(exitcode);
230 }});
231 }
232
233 void processExited(int exitcode) {
234 synchronized (this) {
235 this.exitcode = exitcode;
236 hasExited = true;
237 notifyAll();
238 }
239
240 if (stdout instanceof ProcessPipeInputStream)
241 ((ProcessPipeInputStream) stdout).processExited();
242
243 if (stderr instanceof ProcessPipeInputStream)
244 ((ProcessPipeInputStream) stderr).processExited();
245
246 if (stdin instanceof ProcessPipeOutputStream)
247 ((ProcessPipeOutputStream) stdin).processExited();
248 }
249
250 public OutputStream getOutputStream() {
251 return stdin;
252 }
253
254 public InputStream getInputStream() {
255 return stdout;
256 }
257
258 public InputStream getErrorStream() {
259 return stderr;
260 }
261
262 public synchronized int waitFor() throws InterruptedException {
263 while (!hasExited) {
264 wait();
265 }
266 return exitcode;
267 }
268
269 @Override
270 public synchronized boolean waitFor(long timeout, TimeUnit unit)
271 throws InterruptedException
272 {
273 if (hasExited) return true;
274 if (timeout <= 0) return false;
275
276 long timeoutAsNanos = unit.toNanos(timeout);
277 long startTime = System.nanoTime();
278 long rem = timeoutAsNanos;
279
280 while (!hasExited && (rem > 0)) {
281 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
282 rem = timeoutAsNanos - (System.nanoTime() - startTime);
283 }
284 return hasExited;
285 }
286
287 public synchronized int exitValue() {
288 if (!hasExited) {
289 throw new IllegalThreadStateException("process hasn't exited");
290 }
291 return exitcode;
292 }
293
294 private static native void destroyProcess(int pid, boolean force);
295 private void destroy(boolean force) {
296 // There is a risk that pid will be recycled, causing us to
297 // kill the wrong process! So we only terminate processes
298 // that appear to still be running. Even with this check,
299 // there is an unavoidable race condition here, but the window
300 // is very small, and OSes try hard to not recycle pids too
301 // soon, so this is quite safe.
302 synchronized (this) {
303 if (!hasExited)
304 destroyProcess(pid, force);
305 }
306 try { stdin.close(); } catch (IOException ignored) {}
307 try { stdout.close(); } catch (IOException ignored) {}
308 try { stderr.close(); } catch (IOException ignored) {}
309 }
310
311 public void destroy() {
312 destroy(false);
313 }
314
315 @Override
316 public Process destroyForcibly() {
317 destroy(true);
318 return this;
319 }
320
321 @Override
322 public synchronized boolean isAlive() {
323 return !hasExited;
324 }
325
326 private static native void init();
327
328 static {
329 init();
330 }
331
332 /**
333 * A buffered input stream for a subprocess pipe file descriptor
334 * that allows the underlying file descriptor to be reclaimed when
335 * the process exits, via the processExited hook.
336 *
337 * This is tricky because we do not want the user-level InputStream to be
338 * closed until the user invokes close(), and we need to continue to be
339 * able to read any buffered data lingering in the OS pipe buffer.
340 */
341 static class ProcessPipeInputStream extends BufferedInputStream {
342 private final Object closeLock = new Object();
343
344 ProcessPipeInputStream(int fd) {
345 super(new FileInputStream(newFileDescriptor(fd)));
346 }
347 private static byte[] drainInputStream(InputStream in)
348 throws IOException {
349 int n = 0;
350 int j;
351 byte[] a = null;
352 while ((j = in.available()) > 0) {
353 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
354 n += in.read(a, n, j);
355 }
356 return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
357 }
358
359 /** Called by the process reaper thread when the process exits. */
360 synchronized void processExited() {
361 synchronized (closeLock) {
362 try {
363 InputStream in = this.in;
364 // this stream is closed if and only if: in == null
365 if (in != null) {
366 byte[] stragglers = drainInputStream(in);
367 in.close();
368 this.in = (stragglers == null) ?
369 ProcessBuilder.NullInputStream.INSTANCE :
370 new ByteArrayInputStream(stragglers);
371 }
372 } catch (IOException ignored) {}
373 }
374 }
375
376 @Override
377 public void close() throws IOException {
378 // BufferedInputStream#close() is not synchronized unlike most other methods.
379 // Synchronizing helps avoid race with processExited().
380 synchronized (closeLock) {
381 super.close();
382 }
383 }
384 }
385
386 /**
387 * A buffered output stream for a subprocess pipe file descriptor
388 * that allows the underlying file descriptor to be reclaimed when
389 * the process exits, via the processExited hook.
390 */
391 static class ProcessPipeOutputStream extends BufferedOutputStream {
392 ProcessPipeOutputStream(int fd) {
393 super(new FileOutputStream(newFileDescriptor(fd)));
394 }
395
396 /** Called by the process reaper thread when the process exits. */
397 synchronized void processExited() {
398 OutputStream out = this.out;
399 if (out != null) {
400 try {
401 out.close();
402 } catch (IOException ignored) {
403 // We know of no reason to get an IOException, but if
404 // we do, there's nothing else to do but carry on.
405 }
406 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
407 }
408 }
409 }
410 }