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 }
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