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 Bsd)
  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         POSIX_SPAWN(2);
  69 
  70         private int value;
  71         LaunchMechanism(int x) {value = x;}
  72     };
  73 
  74     /* On BSD, the default is to spawn */
  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 
  97                 helperpath = toCString(javahome + "/lib/jspawnhelper");
  98                 String s = System.getProperty(
  99                     "jdk.lang.Process.launchMechanism", "posix_spawn");
 100 
 101                 try {
 102                     return LaunchMechanism.valueOf(s.toUpperCase());
 103                 } catch (IllegalArgumentException e) {
 104                     throw new Error(s + " is not a supported " +
 105                         "process launch mechanism on this platform.");
 106                 }
 107             }
 108         });
 109     }
 110 
 111     /* this is for the reaping thread */
 112     private native int waitForProcessExit(int pid);
 113 
 114     /**
 115      * Create a process. Depending on the mode flag, this is done by
 116      * one of the following mechanisms.
 117      * - fork(2) and exec(2)
 118      * - posix_spawn(2)
 119      *
 120      * @param fds an array of three file descriptors.
 121      *        Indexes 0, 1, and 2 correspond to standard input,
 122      *        standard output and standard error, respectively.  On
 123      *        input, a value of -1 means to create a pipe to connect
 124      *        child and parent processes.  On output, a value which
 125      *        is not -1 is the parent pipe fd corresponding to the
 126      *        pipe which has been created.  An element of this array
 127      *        is -1 on input if and only if it is <em>not</em> -1 on
 128      *        output.
 129      * @return the pid of the subprocess
 130      */
 131     private native int forkAndExec(int mode, byte[] helperpath,
 132                                    byte[] prog,
 133                                    byte[] argBlock, int argc,
 134                                    byte[] envBlock, int envc,
 135                                    byte[] dir,
 136                                    int[] fds,
 137                                    boolean redirectErrorStream)
 138         throws IOException;
 139 
 140     /**
 141      * The thread factory used to create "process reaper" daemon threads.
 142      */
 143     private static class ProcessReaperThreadFactory implements ThreadFactory {
 144         private final static ThreadGroup group = getRootThreadGroup();
 145 
 146         private static ThreadGroup getRootThreadGroup() {
 147             return doPrivileged(new PrivilegedAction<ThreadGroup> () {
 148                 public ThreadGroup run() {
 149                     ThreadGroup root = Thread.currentThread().getThreadGroup();
 150                     while (root.getParent() != null)
 151                         root = root.getParent();
 152                     return root;
 153                 }});
 154         }
 155 
 156         public Thread newThread(Runnable grimReaper) {
 157             // Our thread stack requirement is quite modest.
 158             Thread t = new Thread(group, grimReaper, "process reaper", 32768);
 159             t.setDaemon(true);
 160             // A small attempt (probably futile) to avoid priority inversion
 161             t.setPriority(Thread.MAX_PRIORITY);
 162             return t;
 163         }
 164     }
 165 
 166     /**
 167      * The thread pool of "process reaper" daemon threads.
 168      */
 169     private static final Executor processReaperExecutor =
 170         doPrivileged(new PrivilegedAction<Executor>() {
 171             public Executor run() {
 172                 return Executors.newCachedThreadPool
 173                     (new ProcessReaperThreadFactory());
 174             }});
 175 
 176     UNIXProcess(final byte[] prog,
 177                 final byte[] argBlock, final int argc,
 178                 final byte[] envBlock, final int envc,
 179                 final byte[] dir,
 180                 final int[] fds,
 181                 final boolean redirectErrorStream)
 182             throws IOException {
 183 
 184         pid = forkAndExec(launchMechanism.value,
 185                           helperpath,
 186                           prog,
 187                           argBlock, argc,
 188                           envBlock, envc,
 189                           dir,
 190                           fds,
 191                           redirectErrorStream);
 192 
 193         try {
 194             doPrivileged(new PrivilegedExceptionAction<Void>() {
 195                 public Void run() throws IOException {
 196                     initStreams(fds);
 197                     return null;
 198                 }});
 199         } catch (PrivilegedActionException ex) {
 200             throw (IOException) ex.getException();
 201         }
 202     }
 203 
 204     static FileDescriptor newFileDescriptor(int fd) {
 205         FileDescriptor fileDescriptor = new FileDescriptor();
 206         fdAccess.set(fileDescriptor, fd);
 207         return fileDescriptor;
 208     }
 209 
 210     void initStreams(int[] fds) throws IOException {
 211         stdin = (fds[0] == -1) ?
 212             ProcessBuilder.NullOutputStream.INSTANCE :
 213             new ProcessPipeOutputStream(fds[0]);
 214 
 215         stdout = (fds[1] == -1) ?
 216             ProcessBuilder.NullInputStream.INSTANCE :
 217             new ProcessPipeInputStream(fds[1]);
 218 
 219         stderr = (fds[2] == -1) ?
 220             ProcessBuilder.NullInputStream.INSTANCE :
 221             new ProcessPipeInputStream(fds[2]);
 222 
 223         processReaperExecutor.execute(new Runnable() {
 224             public void run() {
 225                 int exitcode = waitForProcessExit(pid);
 226                 UNIXProcess.this.processExited(exitcode);
 227             }});
 228     }
 229 
 230     void processExited(int exitcode) {
 231         synchronized (this) {
 232             this.exitcode = exitcode;
 233             hasExited = true;
 234             notifyAll();
 235         }
 236 
 237         if (stdout instanceof ProcessPipeInputStream)
 238             ((ProcessPipeInputStream) stdout).processExited();
 239 
 240         if (stderr instanceof ProcessPipeInputStream)
 241             ((ProcessPipeInputStream) stderr).processExited();
 242 
 243         if (stdin instanceof ProcessPipeOutputStream)
 244             ((ProcessPipeOutputStream) stdin).processExited();
 245     }
 246 
 247     public OutputStream getOutputStream() {
 248         return stdin;
 249     }
 250 
 251     public InputStream getInputStream() {
 252         return stdout;
 253     }
 254 
 255     public InputStream getErrorStream() {
 256         return stderr;
 257     }
 258 
 259     public synchronized int waitFor() throws InterruptedException {
 260         while (!hasExited) {
 261             wait();
 262         }
 263         return exitcode;
 264     }
 265 
 266     public synchronized int exitValue() {
 267         if (!hasExited) {
 268             throw new IllegalThreadStateException("process hasn't exited");
 269         }
 270         return exitcode;
 271     }
 272 
 273     private static native void destroyProcess(int pid);
 274     public void destroy() {
 275         // There is a risk that pid will be recycled, causing us to
 276         // kill the wrong process!  So we only terminate processes
 277         // that appear to still be running.  Even with this check,
 278         // there is an unavoidable race condition here, but the window
 279         // is very small, and OSes try hard to not recycle pids too
 280         // soon, so this is quite safe.
 281         synchronized (this) {
 282             if (!hasExited)
 283                 destroyProcess(pid);
 284         }
 285         try { stdin.close();  } catch (IOException ignored) {}
 286         try { stdout.close(); } catch (IOException ignored) {}
 287         try { stderr.close(); } catch (IOException ignored) {}
 288     }
 289 
 290     private static native void init();
 291 
 292     static {
 293         init();
 294     }
 295 
 296     /**
 297      * A buffered input stream for a subprocess pipe file descriptor
 298      * that allows the underlying file descriptor to be reclaimed when
 299      * the process exits, via the processExited hook.
 300      *
 301      * This is tricky because we do not want the user-level InputStream to be
 302      * closed until the user invokes close(), and we need to continue to be
 303      * able to read any buffered data lingering in the OS pipe buffer.
 304      */
 305     static class ProcessPipeInputStream extends BufferedInputStream {
 306         ProcessPipeInputStream(int fd) {
 307             super(new FileInputStream(newFileDescriptor(fd)));
 308         }
 309 
 310         private static byte[] drainInputStream(InputStream in)
 311                 throws IOException {
 312             if (in == null) return null;
 313             int n = 0;
 314             int j;
 315             byte[] a = null;
 316             while ((j = in.available()) > 0) {
 317                 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
 318                 n += in.read(a, n, j);
 319             }
 320             return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
 321         }
 322 
 323         /** Called by the process reaper thread when the process exits. */
 324         synchronized void processExited() {
 325             // Most BufferedInputStream methods are synchronized, but close()
 326             // is not, and so we have to handle concurrent racing close().
 327             try {
 328                 InputStream in = this.in;
 329                 if (in != null) {
 330                     byte[] stragglers = drainInputStream(in);
 331                     in.close();
 332                     this.in = (stragglers == null) ?
 333                         ProcessBuilder.NullInputStream.INSTANCE :
 334                         new ByteArrayInputStream(stragglers);
 335                     if (buf == null) // asynchronous close()?
 336                         this.in = null;
 337                 }
 338             } catch (IOException ignored) {
 339                 // probably an asynchronous close().
 340             }
 341         }
 342     }
 343 
 344     /**
 345      * A buffered output stream for a subprocess pipe file descriptor
 346      * that allows the underlying file descriptor to be reclaimed when
 347      * the process exits, via the processExited hook.
 348      */
 349     static class ProcessPipeOutputStream extends BufferedOutputStream {
 350         ProcessPipeOutputStream(int fd) {
 351             super(new FileOutputStream(newFileDescriptor(fd)));
 352         }
 353 
 354         /** Called by the process reaper thread when the process exits. */
 355         synchronized void processExited() {
 356             OutputStream out = this.out;
 357             if (out != null) {
 358                 try {
 359                     out.close();
 360                 } catch (IOException ignored) {
 361                     // We know of no reason to get an IOException, but if
 362                     // we do, there's nothing else to do but carry on.
 363                 }
 364                 this.out = ProcessBuilder.NullOutputStream.INSTANCE;
 365             }
 366         }
 367     }
 368 }