1 /*
2 * Copyright (c) 1995, 2010, 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.security.AccessController;
42 import static java.security.AccessController.doPrivileged;
43 import java.security.PrivilegedAction;
44 import java.security.PrivilegedActionException;
45 import java.security.PrivilegedExceptionAction;
46
47 /**
48 * java.lang.Process subclass in the UNIX environment.
49 *
50 * @author Mario Wolczko and Ross Knippel.
51 * @author Konstantin Kladko (ported to Linux)
52 * @author Martin Buchholz
53 */
54 final class UNIXProcess extends Process {
55 private static final sun.misc.JavaIOFileDescriptorAccess fdAccess
56 = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();
57
58 private final int pid;
59 private int exitcode;
60 private boolean hasExited;
61
62 private /* final */ OutputStream stdin;
63 private /* final */ InputStream stdout;
64 private /* final */ InputStream stderr;
65
66 private static enum LaunchMechanism {
67 FORK(1),
68 VFORK(3);
69
70 private int value;
71 LaunchMechanism(int x) {value = x;}
72 };
73
74 /* default is VFORK on Linux */
75 private static final LaunchMechanism launchMechanism;
76 private static byte[] helperpath;
77
78 private static byte[] toCString(String s) {
79 if (s == null)
80 return null;
81 byte[] bytes = s.getBytes();
82 byte[] result = new byte[bytes.length + 1];
83 System.arraycopy(bytes, 0,
84 result, 0,
85 bytes.length);
86 result[result.length-1] = (byte)0;
87 return result;
88 }
89
90 static {
91 launchMechanism = AccessController.doPrivileged(
92 new PrivilegedAction<LaunchMechanism>()
93 {
94 public LaunchMechanism run() {
95 String javahome = System.getProperty("java.home");
96 String osArch = System.getProperty("os.arch");
97
98 helperpath = toCString(javahome + "/lib/" + osArch + "/jspawnhelper");
99 String s = System.getProperty(
100 "jdk.lang.Process.launchMechanism", "vfork");
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 * - clone(2) and exec(2)
120 * - vfork(2) and exec(2)
121 *
122 * @param fds an array of three file descriptors.
123 * Indexes 0, 1, and 2 correspond to standard input,
124 * standard output and standard error, respectively. On
125 * input, a value of -1 means to create a pipe to connect
126 * child and parent processes. On output, a value which
127 * is not -1 is the parent pipe fd corresponding to the
128 * pipe which has been created. An element of this array
129 * is -1 on input if and only if it is <em>not</em> -1 on
130 * output.
131 * @return the pid of the subprocess
132 */
133 private native int forkAndExec(int mode, byte[] helperpath,
134 byte[] prog,
135 byte[] argBlock, int argc,
136 byte[] envBlock, int envc,
137 byte[] dir,
138 int[] fds,
139 boolean redirectErrorStream)
140 throws IOException;
141
142 /**
143 * The thread factory used to create "process reaper" daemon threads.
144 */
145 private static class ProcessReaperThreadFactory implements ThreadFactory {
146 private final static ThreadGroup group = getRootThreadGroup();
147
148 private static ThreadGroup getRootThreadGroup() {
149 return doPrivileged(new PrivilegedAction<ThreadGroup> () {
150 public ThreadGroup run() {
151 ThreadGroup root = Thread.currentThread().getThreadGroup();
152 while (root.getParent() != null)
153 root = root.getParent();
154 return root;
155 }});
156 }
157
158 public Thread newThread(Runnable grimReaper) {
159 // Our thread stack requirement is quite modest.
160 Thread t = new Thread(group, grimReaper, "process reaper", 32768);
161 t.setDaemon(true);
162 // A small attempt (probably futile) to avoid priority inversion
163 t.setPriority(Thread.MAX_PRIORITY);
164 return t;
165 }
166 }
167
168 /**
169 * The thread pool of "process reaper" daemon threads.
170 */
171 private static final Executor processReaperExecutor =
172 doPrivileged(new PrivilegedAction<Executor>() {
173 public Executor run() {
174 return Executors.newCachedThreadPool
175 (new ProcessReaperThreadFactory());
176 }});
177
178 UNIXProcess(final byte[] prog,
179 final byte[] argBlock, final int argc,
180 final byte[] envBlock, final int envc,
181 final byte[] dir,
182 final int[] fds,
183 final boolean redirectErrorStream)
184 throws IOException {
185
186 pid = forkAndExec(launchMechanism.value,
187 helperpath,
188 prog,
189 argBlock, argc,
190 envBlock, envc,
191 dir,
192 fds,
193 redirectErrorStream);
194
195 try {
196 doPrivileged(new PrivilegedExceptionAction<Void>() {
197 public Void run() throws IOException {
198 initStreams(fds);
199 return null;
200 }});
201 } catch (PrivilegedActionException ex) {
202 throw (IOException) ex.getException();
203 }
204 }
205
206 static FileDescriptor newFileDescriptor(int fd) {
207 FileDescriptor fileDescriptor = new FileDescriptor();
208 fdAccess.set(fileDescriptor, fd);
209 return fileDescriptor;
210 }
211
212 void initStreams(int[] fds) throws IOException {
213 stdin = (fds[0] == -1) ?
214 ProcessBuilder.NullOutputStream.INSTANCE :
215 new ProcessPipeOutputStream(fds[0]);
216
217 stdout = (fds[1] == -1) ?
218 ProcessBuilder.NullInputStream.INSTANCE :
219 new ProcessPipeInputStream(fds[1]);
220
221 stderr = (fds[2] == -1) ?
222 ProcessBuilder.NullInputStream.INSTANCE :
223 new ProcessPipeInputStream(fds[2]);
224
225 processReaperExecutor.execute(new Runnable() {
226 public void run() {
227 int exitcode = waitForProcessExit(pid);
228 UNIXProcess.this.processExited(exitcode);
229 }});
230 }
231
232 void processExited(int exitcode) {
233 synchronized (this) {
234 this.exitcode = exitcode;
235 hasExited = true;
236 notifyAll();
237 }
238
239 if (stdout instanceof ProcessPipeInputStream)
240 ((ProcessPipeInputStream) stdout).processExited();
241
242 if (stderr instanceof ProcessPipeInputStream)
243 ((ProcessPipeInputStream) stderr).processExited();
244
245 if (stdin instanceof ProcessPipeOutputStream)
246 ((ProcessPipeOutputStream) stdin).processExited();
247 }
248
249 public OutputStream getOutputStream() {
250 return stdin;
251 }
252
253 public InputStream getInputStream() {
254 return stdout;
255 }
256
257 public InputStream getErrorStream() {
258 return stderr;
259 }
260
261 public synchronized int waitFor() throws InterruptedException {
262 while (!hasExited) {
263 wait();
264 }
265 return exitcode;
266 }
267
268 public synchronized int exitValue() {
269 if (!hasExited) {
270 throw new IllegalThreadStateException("process hasn't exited");
271 }
272 return exitcode;
273 }
274
275 private static native void destroyProcess(int pid);
276 public void destroy() {
277 // There is a risk that pid will be recycled, causing us to
278 // kill the wrong process! So we only terminate processes
279 // that appear to still be running. Even with this check,
280 // there is an unavoidable race condition here, but the window
281 // is very small, and OSes try hard to not recycle pids too
282 // soon, so this is quite safe.
283 synchronized (this) {
284 if (!hasExited)
285 destroyProcess(pid);
286 }
287 try { stdin.close(); } catch (IOException ignored) {}
288 try { stdout.close(); } catch (IOException ignored) {}
289 try { stderr.close(); } catch (IOException ignored) {}
290 }
291
292 private static native void init();
293
294 static {
295 init();
296 }
297
298 /**
299 * A buffered input stream for a subprocess pipe file descriptor
300 * that allows the underlying file descriptor to be reclaimed when
301 * the process exits, via the processExited hook.
302 *
303 * This is tricky because we do not want the user-level InputStream to be
304 * closed until the user invokes close(), and we need to continue to be
305 * able to read any buffered data lingering in the OS pipe buffer.
306 */
307 static class ProcessPipeInputStream extends BufferedInputStream {
308 ProcessPipeInputStream(int fd) {
309 super(new FileInputStream(newFileDescriptor(fd)));
310 }
311
312 private static byte[] drainInputStream(InputStream in)
313 throws IOException {
314 if (in == null) return null;
315 int n = 0;
316 int j;
317 byte[] a = null;
318 while ((j = in.available()) > 0) {
319 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
320 n += in.read(a, n, j);
321 }
322 return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
323 }
324
325 /** Called by the process reaper thread when the process exits. */
326 synchronized void processExited() {
327 // Most BufferedInputStream methods are synchronized, but close()
328 // is not, and so we have to handle concurrent racing close().
329 try {
330 InputStream in = this.in;
331 if (in != null) {
332 byte[] stragglers = drainInputStream(in);
333 in.close();
334 this.in = (stragglers == null) ?
335 ProcessBuilder.NullInputStream.INSTANCE :
336 new ByteArrayInputStream(stragglers);
337 if (buf == null) // asynchronous close()?
338 this.in = null;
339 }
340 } catch (IOException ignored) {
341 // probably an asynchronous close().
342 }
343 }
344 }
345
346 /**
347 * A buffered output stream for a subprocess pipe file descriptor
348 * that allows the underlying file descriptor to be reclaimed when
349 * the process exits, via the processExited hook.
350 */
351 static class ProcessPipeOutputStream extends BufferedOutputStream {
352 ProcessPipeOutputStream(int fd) {
353 super(new FileOutputStream(newFileDescriptor(fd)));
354 }
355
356 /** Called by the process reaper thread when the process exits. */
357 synchronized void processExited() {
358 OutputStream out = this.out;
359 if (out != null) {
360 try {
361 out.close();
362 } catch (IOException ignored) {
363 // We know of no reason to get an IOException, but if
364 // we do, there's nothing else to do but carry on.
365 }
366 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
367 }
368 }
369 }
370 }
--- EOF ---