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 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 String javahome;
68 private static String arch;
69 private static String helperpath;
70
71 enum LaunchMechanism {
72 CLONE(1), FORK(2),
73 VFORK(3), POSIX_SPAWN(4);
74
75 private int value;
76 LaunchMechanism(int x) {value = x;}
77 };
78
79 /* On BSD, the default is to spawn */
80 private static LaunchMechanism launchMechanism = LaunchMechanism.POSIX_SPAWN;
81
82 static {
83 AccessController.doPrivileged(new PrivilegedAction<Void>() {
84 public Void run() {
85 String javahome = System.getProperty("java.home");
86 String osarch = System.getProperty("os.arch");
87
88 helperpath = javahome + "/lib/jspawnhelper";
89 String s = System.getProperty("jdk.lang.Process.launchMechanism");
90 if (s != null && !s.equals("POSIX_SPAWN")) {
91 if (s.equals("FORK")) {
92 launchMechanism = LaunchMechanism.FORK;
93 } else {
94 throw new Error(s + " is not a supported " +
95 "process launch mechanism on this platform.");
96 }
97 }
98 return null;
99 }
100 });
101 }
102
103 /* this is for the reaping thread */
104 private native int waitForProcessExit(int pid);
105
106 /**
107 * Create a process. Depending on the mode flag, this is done by
108 * one of the following mechanisms.
109 * - fork(2) and exec(2)
110 * - vfork(2) and exec(2)
111 * - posix_spawn(2)
112 *
113 * @param fds an array of three file descriptors.
114 * Indexes 0, 1, and 2 correspond to standard input,
115 * standard output and standard error, respectively. On
116 * input, a value of -1 means to create a pipe to connect
117 * child and parent processes. On output, a value which
118 * is not -1 is the parent pipe fd corresponding to the
119 * pipe which has been created. An element of this array
120 * is -1 on input if and only if it is <em>not</em> -1 on
121 * output.
122 * @return the pid of the subprocess
123 */
124 private native int forkAndExec(int mode, byte[] prog,
125 byte[] argBlock, int argc,
126 byte[] envBlock, int envc,
127 byte[] dir,
128 int[] fds,
129 boolean redirectErrorStream)
130 throws IOException;
131
132 /**
133 * The thread factory used to create "process reaper" daemon threads.
134 */
135 private static class ProcessReaperThreadFactory implements ThreadFactory {
136 private final static ThreadGroup group = getRootThreadGroup();
137
138 private static ThreadGroup getRootThreadGroup() {
139 return doPrivileged(new PrivilegedAction<ThreadGroup> () {
140 public ThreadGroup run() {
141 ThreadGroup root = Thread.currentThread().getThreadGroup();
142 while (root.getParent() != null)
143 root = root.getParent();
144 return root;
145 }});
146 }
147
148 public Thread newThread(Runnable grimReaper) {
149 // Our thread stack requirement is quite modest.
150 Thread t = new Thread(group, grimReaper, "process reaper", 32768);
151 t.setDaemon(true);
152 // A small attempt (probably futile) to avoid priority inversion
153 t.setPriority(Thread.MAX_PRIORITY);
154 return t;
155 }
156 }
157
158 /**
159 * The thread pool of "process reaper" daemon threads.
160 */
161 private static final Executor processReaperExecutor =
162 doPrivileged(new PrivilegedAction<Executor>() {
163 public Executor run() {
164 return Executors.newCachedThreadPool
165 (new ProcessReaperThreadFactory());
166 }});
167
168 UNIXProcess(final byte[] prog,
169 final byte[] argBlock, final int argc,
170 final byte[] envBlock, final int envc,
171 final byte[] dir,
172 final int[] fds,
173 final boolean redirectErrorStream)
174 throws IOException {
175
176 pid = forkAndExec(launchMechanism.value,
177 prog,
178 argBlock, argc,
179 envBlock, envc,
180 dir,
181 fds,
182 redirectErrorStream);
183
184 try {
185 doPrivileged(new PrivilegedExceptionAction<Void>() {
186 public Void run() throws IOException {
187 initStreams(fds);
188 return null;
189 }});
190 } catch (PrivilegedActionException ex) {
191 throw (IOException) ex.getException();
192 }
193 }
194
195 static FileDescriptor newFileDescriptor(int fd) {
196 FileDescriptor fileDescriptor = new FileDescriptor();
197 fdAccess.set(fileDescriptor, fd);
198 return fileDescriptor;
199 }
200
201 void initStreams(int[] fds) throws IOException {
202 stdin = (fds[0] == -1) ?
203 ProcessBuilder.NullOutputStream.INSTANCE :
204 new ProcessPipeOutputStream(fds[0]);
205
206 stdout = (fds[1] == -1) ?
207 ProcessBuilder.NullInputStream.INSTANCE :
208 new ProcessPipeInputStream(fds[1]);
209
210 stderr = (fds[2] == -1) ?
211 ProcessBuilder.NullInputStream.INSTANCE :
212 new ProcessPipeInputStream(fds[2]);
213
214 processReaperExecutor.execute(new Runnable() {
215 public void run() {
216 int exitcode = waitForProcessExit(pid);
217 UNIXProcess.this.processExited(exitcode);
218 }});
219 }
220
221 void processExited(int exitcode) {
222 synchronized (this) {
223 this.exitcode = exitcode;
224 hasExited = true;
225 notifyAll();
226 }
227
228 if (stdout instanceof ProcessPipeInputStream)
229 ((ProcessPipeInputStream) stdout).processExited();
230
231 if (stderr instanceof ProcessPipeInputStream)
232 ((ProcessPipeInputStream) stderr).processExited();
233
234 if (stdin instanceof ProcessPipeOutputStream)
235 ((ProcessPipeOutputStream) stdin).processExited();
236 }
237
238 public OutputStream getOutputStream() {
239 return stdin;
240 }
241
242 public InputStream getInputStream() {
243 return stdout;
244 }
245
246 public InputStream getErrorStream() {
247 return stderr;
248 }
249
250 public synchronized int waitFor() throws InterruptedException {
251 while (!hasExited) {
252 wait();
253 }
254 return exitcode;
255 }
256
257 @Override
258 public synchronized boolean waitFor(long timeout, TimeUnit unit)
259 throws InterruptedException
260 {
261 if (hasExited) return true;
262 if (timeout <= 0) return false;
263
264 long timeoutAsNanos = unit.toNanos(timeout);
265 long startTime = System.nanoTime();
266 long rem = timeoutAsNanos;
267
268 while (!hasExited && (rem > 0)) {
269 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
270 rem = timeoutAsNanos - (System.nanoTime() - startTime);
271 }
272 return hasExited;
273 }
274
275 public synchronized int exitValue() {
276 if (!hasExited) {
277 throw new IllegalThreadStateException("process hasn't exited");
278 }
279 return exitcode;
280 }
281
282 private static native void destroyProcess(int pid, boolean force);
283 private void destroy(boolean force) {
284 // There is a risk that pid will be recycled, causing us to
285 // kill the wrong process! So we only terminate processes
286 // that appear to still be running. Even with this check,
287 // there is an unavoidable race condition here, but the window
288 // is very small, and OSes try hard to not recycle pids too
289 // soon, so this is quite safe.
290 synchronized (this) {
291 if (!hasExited)
292 destroyProcess(pid, force);
293 }
294 try { stdin.close(); } catch (IOException ignored) {}
295 try { stdout.close(); } catch (IOException ignored) {}
296 try { stderr.close(); } catch (IOException ignored) {}
297 }
298
299 public void destroy() {
300 destroy(false);
301 }
302
303 @Override
304 public Process destroyForcibly() {
305 destroy(true);
306 return this;
307 }
308
309 @Override
310 public synchronized boolean isAlive() {
311 return !hasExited;
312 }
313
314 private static native void init();
315
316 static {
317 init();
318 }
319
320 /**
321 * A buffered input stream for a subprocess pipe file descriptor
322 * that allows the underlying file descriptor to be reclaimed when
323 * the process exits, via the processExited hook.
324 *
325 * This is tricky because we do not want the user-level InputStream to be
326 * closed until the user invokes close(), and we need to continue to be
327 * able to read any buffered data lingering in the OS pipe buffer.
328 */
329 static class ProcessPipeInputStream extends BufferedInputStream {
330 ProcessPipeInputStream(int fd) {
331 super(new FileInputStream(newFileDescriptor(fd)));
332 }
333
334 private static byte[] drainInputStream(InputStream in)
335 throws IOException {
336 if (in == null) return null;
337 int n = 0;
338 int j;
339 byte[] a = null;
340 while ((j = in.available()) > 0) {
341 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
342 n += in.read(a, n, j);
343 }
344 return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
345 }
346
347 /** Called by the process reaper thread when the process exits. */
348 synchronized void processExited() {
349 // Most BufferedInputStream methods are synchronized, but close()
350 // is not, and so we have to handle concurrent racing close().
351 try {
352 InputStream in = this.in;
353 if (in != null) {
354 byte[] stragglers = drainInputStream(in);
355 in.close();
356 this.in = (stragglers == null) ?
357 ProcessBuilder.NullInputStream.INSTANCE :
358 new ByteArrayInputStream(stragglers);
359 if (buf == null) // asynchronous close()?
360 this.in = null;
361 }
362 } catch (IOException ignored) {
363 // probably an asynchronous close().
364 }
365 }
366 }
367
368 /**
369 * A buffered output stream for a subprocess pipe file descriptor
370 * that allows the underlying file descriptor to be reclaimed when
371 * the process exits, via the processExited hook.
372 */
373 static class ProcessPipeOutputStream extends BufferedOutputStream {
374 ProcessPipeOutputStream(int fd) {
375 super(new FileOutputStream(newFileDescriptor(fd)));
376 }
377
378 /** Called by the process reaper thread when the process exits. */
379 synchronized void processExited() {
380 OutputStream out = this.out;
381 if (out != null) {
382 try {
383 out.close();
384 } catch (IOException ignored) {
385 // We know of no reason to get an IOException, but if
386 // we do, there's nothing else to do but carry on.
387 }
388 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
389 }
390 }
391 }
392 }