1 /*
   2  * Copyright (c) 1996, 2016, 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 jdk.internal.misc;
  27 
  28 import static java.lang.Thread.State.*;


  29 import java.util.Properties;

  30 
  31 public class VM {
  32 
  33     // the init level when the VM is fully initialized
  34     private static final int JAVA_LANG_SYSTEM_INITED     = 1;
  35     private static final int MODULE_SYSTEM_INITED        = 2;
  36     private static final int SYSTEM_LOADER_INITIALIZING  = 3;
  37     private static final int SYSTEM_BOOTED               = 4;
  38 
  39     // 0, 1, 2, ...
  40     private static volatile int initLevel;
  41     private static final Object lock = new Object();
  42 
  43     /**
  44      * Sets the init level.
  45      *
  46      * @see java.lang.System#initPhase1
  47      * @see java.lang.System#initPhase2
  48      * @see java.lang.System#initPhase3
  49      */
  50     public static void initLevel(int value) {
  51         synchronized (lock) {
  52             if (value <= initLevel || value > SYSTEM_BOOTED)
  53                 throw new InternalError("Bad level: " + value);
  54             initLevel = value;
  55             lock.notifyAll();
  56         }
  57     }
  58 
  59     /**
  60      * Returns the current init level.
  61      */
  62     public static int initLevel() {
  63         return initLevel;
  64     }
  65 
  66     /**
  67      * Waits for the init level to get the given value.
  68      *
  69      * @see java.lang.ref.Finalizer
  70      */
  71     public static void awaitInitLevel(int value) throws InterruptedException {
  72         synchronized (lock) {
  73             while (initLevel < value) {
  74                 lock.wait();
  75             }
  76         }
  77     }
  78 
  79     /**
  80      * Returns {@code true} if the module system has been initialized.
  81      * @see java.lang.System#initPhase2
  82      */
  83     public static boolean isModuleSystemInited() {
  84         return VM.initLevel() >= MODULE_SYSTEM_INITED;
  85     }
  86 
  87     /**
  88      * Returns {@code true} if the VM is fully initialized.
  89      */
  90     public static boolean isBooted() {
  91         return initLevel >= SYSTEM_BOOTED;
  92     }
  93 
  94     // A user-settable upper limit on the maximum amount of allocatable direct
  95     // buffer memory.  This value may be changed during VM initialization if
  96     // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
  97     //
  98     // The initial value of this field is arbitrary; during JRE initialization
  99     // it will be reset to the value specified on the command line, if any,
 100     // otherwise to Runtime.getRuntime().maxMemory().
 101     //
 102     private static long directMemory = 64 * 1024 * 1024;
 103 
 104     // Returns the maximum amount of allocatable direct buffer memory.
 105     // The directMemory variable is initialized during system initialization
 106     // in the saveAndRemoveProperties method.
 107     //
 108     public static long maxDirectMemory() {
 109         return directMemory;
 110     }
 111 
 112     // User-controllable flag that determines if direct buffers should be page
 113     // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
 114     // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
 115     private static boolean pageAlignDirectMemory;
 116 
 117     // Returns {@code true} if the direct buffers should be page aligned. This
 118     // variable is initialized by saveAndRemoveProperties.
 119     public static boolean isDirectMemoryPageAligned() {
 120         return pageAlignDirectMemory;
 121     }
 122 
 123     /**
 124      * Returns true if the given class loader is in the system domain
 125      * in which all permissions are granted.
 126      */
 127     public static boolean isSystemDomainLoader(ClassLoader loader) {
 128         return loader == null;
 129     }
 130 
 131     /**
 132      * Returns the system property of the specified key saved at
 133      * system initialization time.  This method should only be used
 134      * for the system properties that are not changed during runtime.
 135      * It accesses a private copy of the system properties so
 136      * that user's locking of the system properties object will not
 137      * cause the library to deadlock.
 138      *
 139      * Note that the saved system properties do not include
 140      * the ones set by sun.misc.Version.init().
 141      *
 142      */
 143     public static String getSavedProperty(String key) {
 144         if (savedProps.isEmpty())
 145             throw new IllegalStateException("Should be non-empty if initialized");
 146 
 147         return savedProps.getProperty(key);















 148     }
 149 
 150     // TODO: the Property Management needs to be refactored and
 151     // the appropriate prop keys need to be accessible to the
 152     // calling classes to avoid duplication of keys.
 153     private static final Properties savedProps = new Properties();
 154 
 155     // Save a private copy of the system properties and remove
 156     // the system properties that are not intended for public access.
 157     //
 158     // This method can only be invoked during system initialization.
 159     public static void saveAndRemoveProperties(Properties props) {
 160         if (initLevel() != 0)
 161             throw new IllegalStateException("Wrong init level");
 162 
 163         savedProps.putAll(props);




 164 
 165         // Set the maximum amount of direct memory.  This value is controlled
 166         // by the vm option -XX:MaxDirectMemorySize=<size>.
 167         // The maximum amount of allocatable direct buffer memory (in bytes)
 168         // from the system property sun.nio.MaxDirectMemorySize set by the VM.
 169         // The system property will be removed.
 170         String s = (String)props.remove("sun.nio.MaxDirectMemorySize");
 171         if (s != null) {
 172             if (s.equals("-1")) {
 173                 // -XX:MaxDirectMemorySize not given, take default
 174                 directMemory = Runtime.getRuntime().maxMemory();
 175             } else {
 176                 long l = Long.parseLong(s);
 177                 if (l > -1)
 178                     directMemory = l;
 179             }
 180         }
 181 
 182         // Check if direct buffers should be page aligned
 183         s = (String)props.remove("sun.nio.PageAlignDirectMemory");
 184         if ("true".equals(s))
 185             pageAlignDirectMemory = true;
 186 
 187         // Remove other private system properties
 188         // used by java.lang.Integer.IntegerCache
 189         props.remove("java.lang.Integer.IntegerCache.high");
 190 
 191         // used by sun.launcher.LauncherHelper
 192         props.remove("sun.java.launcher.diag");
 193 
 194         // used by jdk.internal.loader.ClassLoaders
 195         props.remove("jdk.boot.class.path.append");
 196     }
 197 
 198     // Initialize any miscellaneous operating system settings that need to be
 199     // set for the class libraries.
 200     //
 201     public static void initializeOSEnvironment() {
 202         if (initLevel() == 0) {
 203             OSEnvironment.initialize();
 204         }
 205     }
 206 
 207     /* Current count of objects pending for finalization */
 208     private static volatile int finalRefCount;
 209 
 210     /* Peak count of objects pending for finalization */
 211     private static volatile int peakFinalRefCount;
 212 
 213     /*
 214      * Gets the number of objects pending for finalization.
 215      *
 216      * @return the number of objects pending for finalization.
 217      */
 218     public static int getFinalRefCount() {
 219         return finalRefCount;
 220     }
 221 
 222     /*
 223      * Gets the peak number of objects pending for finalization.
 224      *
 225      * @return the peak number of objects pending for finalization.
 226      */
 227     public static int getPeakFinalRefCount() {
 228         return peakFinalRefCount;
 229     }
 230 
 231     /*
 232      * Add {@code n} to the objects pending for finalization count.
 233      *
 234      * @param n an integer value to be added to the objects pending
 235      * for finalization count
 236      */
 237     public static void addFinalRefCount(int n) {
 238         // The caller must hold lock to synchronize the update.
 239 
 240         finalRefCount += n;
 241         if (finalRefCount > peakFinalRefCount) {
 242             peakFinalRefCount = finalRefCount;
 243         }
 244     }
 245 
 246     /**
 247      * Returns Thread.State for the given threadStatus
 248      */
 249     public static Thread.State toThreadState(int threadStatus) {
 250         if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) {
 251             return RUNNABLE;
 252         } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) {
 253             return BLOCKED;
 254         } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) {
 255             return WAITING;
 256         } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) {
 257             return TIMED_WAITING;
 258         } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) {
 259             return TERMINATED;
 260         } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) {
 261             return NEW;
 262         } else {
 263             return RUNNABLE;
 264         }
 265     }
 266 
 267     /* The threadStatus field is set by the VM at state transition
 268      * in the hotspot implementation. Its value is set according to
 269      * the JVM TI specification GetThreadState function.
 270      */
 271     private static final int JVMTI_THREAD_STATE_ALIVE = 0x0001;
 272     private static final int JVMTI_THREAD_STATE_TERMINATED = 0x0002;
 273     private static final int JVMTI_THREAD_STATE_RUNNABLE = 0x0004;
 274     private static final int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400;
 275     private static final int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010;
 276     private static final int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020;
 277 
 278     /*
 279      * Returns the first user-defined class loader up the execution stack,
 280      * or the platform class loader if only code from the platform or
 281      * bootstrap class loader is on the stack.
 282      */
 283     public static ClassLoader latestUserDefinedLoader() {
 284         ClassLoader loader = latestUserDefinedLoader0();
 285         return loader != null ? loader : ClassLoader.getPlatformClassLoader();
 286     }
 287 
 288     /*
 289      * Returns the first user-defined class loader up the execution stack,
 290      * or null if only code from the platform or bootstrap class loader is
 291      * on the stack.  VM does not keep a reference of platform loader and so
 292      * it returns null.
 293      *
 294      * This method should be replaced with StackWalker::walk and then we can
 295      * remove the logic in the VM.
 296      */
 297     private static native ClassLoader latestUserDefinedLoader0();
 298 
 299     /**
 300      * Returns {@code true} if we are in a set UID program.
 301      */
 302     public static boolean isSetUID() {
 303         long uid = getuid();
 304         long euid = geteuid();
 305         long gid = getgid();
 306         long egid = getegid();
 307         return uid != euid  || gid != egid;
 308     }
 309 
 310     /**
 311      * Returns the real user ID of the calling process,
 312      * or -1 if the value is not available.
 313      */
 314     public static native long getuid();
 315 
 316     /**
 317      * Returns the effective user ID of the calling process,
 318      * or -1 if the value is not available.
 319      */
 320     public static native long geteuid();
 321 
 322     /**
 323      * Returns the real group ID of the calling process,
 324      * or -1 if the value is not available.
 325      */
 326     public static native long getgid();
 327 
 328     /**
 329      * Returns the effective group ID of the calling process,
 330      * or -1 if the value is not available.
 331      */
 332     public static native long getegid();
 333 
 334     /**
 335      * Get a nanosecond time stamp adjustment in the form of a single long.
 336      *
 337      * This value can be used to create an instant using
 338      * {@link java.time.Instant#ofEpochSecond(long, long)
 339      *  java.time.Instant.ofEpochSecond(offsetInSeconds,
 340      *  getNanoTimeAdjustment(offsetInSeconds))}.
 341      * <p>
 342      * The value returned has the best resolution available to the JVM on
 343      * the current system.
 344      * This is usually down to microseconds - or tenth of microseconds -
 345      * depending on the OS/Hardware and the JVM implementation.
 346      *
 347      * @param offsetInSeconds The offset in seconds from which the nanosecond
 348      *        time stamp should be computed.
 349      *
 350      * @apiNote The offset should be recent enough - so that
 351      *         {@code offsetInSeconds} is within {@code +/- 2^32} seconds of the
 352      *         current UTC time. If the offset is too far off, {@code -1} will be
 353      *         returned. As such, {@code -1} must not be considered as a valid
 354      *         nano time adjustment, but as an exception value indicating
 355      *         that an offset closer to the current time should be used.
 356      *
 357      * @return A nanosecond time stamp adjustment in the form of a single long.
 358      *     If the offset is too far off the current time, this method returns -1.
 359      *     In that case, the caller should call this method again, passing a
 360      *     more accurate offset.
 361      */
 362     public static native long getNanoTimeAdjustment(long offsetInSeconds);
 363 
 364     /**
 365      * Returns the VM arguments for this runtime environment.
 366      *
 367      * @implNote
 368      * The HotSpot JVM processes the input arguments from multiple sources
 369      * in the following order:
 370      * 1. JAVA_TOOL_OPTIONS environment variable
 371      * 2. Options from JNI Invocation API
 372      * 3. _JAVA_OPTIONS environment variable
 373      *
 374      * If VM options file is specified via -XX:VMOptionsFile, the vm options
 375      * file is read and expanded in place of -XX:VMOptionFile option.
 376      */
 377     public static native String[] getRuntimeArguments();
 378 
 379     static {
 380         initialize();
 381     }
 382     private static native void initialize();
 383 }
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