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