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 }