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 }