1 /*
   2  * Copyright (c) 1996, 2018, 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 
  30 import java.util.Collections;
  31 import java.util.Map;
  32 import java.util.Properties;
  33 
  34 public class VM {
  35 
  36     // the init level when the VM is fully initialized
  37     private static final int JAVA_LANG_SYSTEM_INITED     = 1;
  38     private static final int MODULE_SYSTEM_INITED        = 2;
  39     private static final int SYSTEM_LOADER_INITIALIZING  = 3;
  40     private static final int SYSTEM_BOOTED               = 4;
  41     private static final int SYSTEM_SHUTDOWN             = 5;
  42 
  43 
  44     // 0, 1, 2, ...
  45     private static volatile int initLevel;
  46     private static final Object lock = new Object();
  47 
  48     /**
  49      * Sets the init level.
  50      *
  51      * @see java.lang.System#initPhase1
  52      * @see java.lang.System#initPhase2
  53      * @see java.lang.System#initPhase3
  54      */
  55     public static void initLevel(int value) {
  56         synchronized (lock) {
  57             if (value <= initLevel || value > SYSTEM_SHUTDOWN)
  58                 throw new InternalError("Bad level: " + value);
  59             initLevel = value;
  60             lock.notifyAll();
  61         }
  62     }
  63 
  64     /**
  65      * Returns the current init level.
  66      */
  67     public static int initLevel() {
  68         return initLevel;
  69     }
  70 
  71     /**
  72      * Waits for the init level to get the given value.
  73      *
  74      * @see java.lang.ref.Finalizer
  75      */
  76     public static void awaitInitLevel(int value) throws InterruptedException {
  77         synchronized (lock) {
  78             while (initLevel < value) {
  79                 lock.wait();
  80             }
  81         }
  82     }
  83 
  84     /**
  85      * Returns {@code true} if the module system has been initialized.
  86      * @see java.lang.System#initPhase2
  87      */
  88     public static boolean isModuleSystemInited() {
  89         return VM.initLevel() >= MODULE_SYSTEM_INITED;
  90     }
  91 
  92     /**
  93      * Returns {@code true} if the VM is fully initialized.
  94      */
  95     public static boolean isBooted() {
  96         return initLevel >= SYSTEM_BOOTED;
  97     }
  98 
  99     /**
 100      * Set shutdown state.  Shutdown completes when all registered shutdown
 101      * hooks have been run.
 102      *
 103      * @see java.lang.Shutdown
 104      */
 105     public static void shutdown() {
 106         initLevel(SYSTEM_SHUTDOWN);
 107     }
 108 
 109     /**
 110      * Returns {@code true} if the VM has been shutdown
 111      */
 112     public static boolean isShutdown() {
 113         return initLevel == SYSTEM_SHUTDOWN;
 114     }
 115 
 116     // A user-settable upper limit on the maximum amount of allocatable direct
 117     // buffer memory.  This value may be changed during VM initialization if
 118     // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
 119     //
 120     // The initial value of this field is arbitrary; during JRE initialization
 121     // it will be reset to the value specified on the command line, if any,
 122     // otherwise to Runtime.getRuntime().maxMemory().
 123     //
 124     private static long directMemory = 64 * 1024 * 1024;
 125 
 126     // Returns the maximum amount of allocatable direct buffer memory.
 127     // The directMemory variable is initialized during system initialization
 128     // in the saveAndRemoveProperties method.
 129     //
 130     public static long maxDirectMemory() {
 131         return directMemory;
 132     }
 133 
 134     // User-controllable flag that determines if direct buffers should be page
 135     // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
 136     // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
 137     private static boolean pageAlignDirectMemory;
 138 
 139     // Returns {@code true} if the direct buffers should be page aligned. This
 140     // variable is initialized by saveAndRemoveProperties.
 141     public static boolean isDirectMemoryPageAligned() {
 142         return pageAlignDirectMemory;
 143     }
 144 
 145     /**
 146      * Returns true if the given class loader is the bootstrap class loader
 147      * or the platform class loader.
 148      */
 149     public static boolean isSystemDomainLoader(ClassLoader loader) {
 150         return loader == null || loader == ClassLoader.getPlatformClassLoader();
 151     }
 152 
 153     /**
 154      * Returns the system property of the specified key saved at
 155      * system initialization time.  This method should only be used
 156      * for the system properties that are not changed during runtime.
 157      *
 158      * Note that the saved system properties do not include
 159      * the ones set by java.lang.VersionProps.init().
 160      */
 161     public static String getSavedProperty(String key) {
 162         if (savedProps == null)
 163             throw new IllegalStateException("Not yet initialized");
 164 
 165         return savedProps.get(key);
 166     }
 167 
 168     /**
 169      * Gets an unmodifiable view of the system properties saved at system
 170      * initialization time. This method should only be used
 171      * for the system properties that are not changed during runtime.
 172      *
 173      * Note that the saved system properties do not include
 174      * the ones set by java.lang.VersionProps.init().
 175      */
 176     public static Map<String, String> getSavedProperties() {
 177         if (savedProps == null)
 178             throw new IllegalStateException("Not yet initialized");
 179 
 180         return Collections.unmodifiableMap(savedProps);
 181     }
 182 
 183     private static Map<String, String> savedProps;
 184 
 185     // Save a private copy of the system properties and remove
 186     // the system properties that are not intended for public access.
 187     //
 188     // This method can only be invoked during system initialization.
 189     public static void saveProperties(Map<String, String> props) {
 190         if (initLevel() != 0)
 191             throw new IllegalStateException("Wrong init level");
 192 
 193         // only main thread is running at this time, so savedProps and
 194         // its content will be correctly published to threads started later
 195         if (savedProps == null) {
 196             savedProps = props;
 197         }
 198 
 199         // Set the maximum amount of direct memory.  This value is controlled
 200         // by the vm option -XX:MaxDirectMemorySize=<size>.
 201         // The maximum amount of allocatable direct buffer memory (in bytes)
 202         // from the system property sun.nio.MaxDirectMemorySize set by the VM.
 203         // If not set or set to -1, the max memory will be used
 204         // The system property will be removed.
 205         String s = props.get("sun.nio.MaxDirectMemorySize");
 206         if (s == null || s.isEmpty() || s.equals("-1")) {
 207             // -XX:MaxDirectMemorySize not given, take default
 208             directMemory = Runtime.getRuntime().maxMemory();
 209         } else {
 210             long l = Long.parseLong(s);
 211             if (l > -1)
 212                 directMemory = l;
 213         }
 214 
 215         // Check if direct buffers should be page aligned
 216         s = props.get("sun.nio.PageAlignDirectMemory");
 217         if ("true".equals(s))
 218             pageAlignDirectMemory = true;
 219     }
 220 
 221     // Initialize any miscellaneous operating system settings that need to be
 222     // set for the class libraries.
 223     //
 224     public static void initializeOSEnvironment() {
 225         if (initLevel() == 0) {
 226             OSEnvironment.initialize();
 227         }
 228     }
 229 
 230     /* Current count of objects pending for finalization */
 231     private static volatile int finalRefCount;
 232 
 233     /* Peak count of objects pending for finalization */
 234     private static volatile int peakFinalRefCount;
 235 
 236     /*
 237      * Gets the number of objects pending for finalization.
 238      *
 239      * @return the number of objects pending for finalization.
 240      */
 241     public static int getFinalRefCount() {
 242         return finalRefCount;
 243     }
 244 
 245     /*
 246      * Gets the peak number of objects pending for finalization.
 247      *
 248      * @return the peak number of objects pending for finalization.
 249      */
 250     public static int getPeakFinalRefCount() {
 251         return peakFinalRefCount;
 252     }
 253 
 254     /*
 255      * Add {@code n} to the objects pending for finalization count.
 256      *
 257      * @param n an integer value to be added to the objects pending
 258      * for finalization count
 259      */
 260     public static void addFinalRefCount(int n) {
 261         // The caller must hold lock to synchronize the update.
 262 
 263         finalRefCount += n;
 264         if (finalRefCount > peakFinalRefCount) {
 265             peakFinalRefCount = finalRefCount;
 266         }
 267     }
 268 
 269     /**
 270      * Returns Thread.State for the given threadStatus
 271      */
 272     public static Thread.State toThreadState(int threadStatus) {
 273         if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) {
 274             return RUNNABLE;
 275         } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) {
 276             return BLOCKED;
 277         } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) {
 278             return WAITING;
 279         } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) {
 280             return TIMED_WAITING;
 281         } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) {
 282             return TERMINATED;
 283         } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) {
 284             return NEW;
 285         } else {
 286             return RUNNABLE;
 287         }
 288     }
 289 
 290     /* The threadStatus field is set by the VM at state transition
 291      * in the hotspot implementation. Its value is set according to
 292      * the JVM TI specification GetThreadState function.
 293      */
 294     private static final int JVMTI_THREAD_STATE_ALIVE = 0x0001;
 295     private static final int JVMTI_THREAD_STATE_TERMINATED = 0x0002;
 296     private static final int JVMTI_THREAD_STATE_RUNNABLE = 0x0004;
 297     private static final int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400;
 298     private static final int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010;
 299     private static final int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020;
 300 
 301     /*
 302      * Returns the first user-defined class loader up the execution stack,
 303      * or the platform class loader if only code from the platform or
 304      * bootstrap class loader is on the stack.
 305      */
 306     public static ClassLoader latestUserDefinedLoader() {
 307         ClassLoader loader = latestUserDefinedLoader0();
 308         return loader != null ? loader : ClassLoader.getPlatformClassLoader();
 309     }
 310 
 311     /*
 312      * Returns the first user-defined class loader up the execution stack,
 313      * or null if only code from the platform or bootstrap class loader is
 314      * on the stack.  VM does not keep a reference of platform loader and so
 315      * it returns null.
 316      *
 317      * This method should be replaced with StackWalker::walk and then we can
 318      * remove the logic in the VM.
 319      */
 320     private static native ClassLoader latestUserDefinedLoader0();
 321 
 322     /**
 323      * Returns {@code true} if we are in a set UID program.
 324      */
 325     public static boolean isSetUID() {
 326         long uid = getuid();
 327         long euid = geteuid();
 328         long gid = getgid();
 329         long egid = getegid();
 330         return uid != euid  || gid != egid;
 331     }
 332 
 333     /**
 334      * Returns the real user ID of the calling process,
 335      * or -1 if the value is not available.
 336      */
 337     public static native long getuid();
 338 
 339     /**
 340      * Returns the effective user ID of the calling process,
 341      * or -1 if the value is not available.
 342      */
 343     public static native long geteuid();
 344 
 345     /**
 346      * Returns the real group ID of the calling process,
 347      * or -1 if the value is not available.
 348      */
 349     public static native long getgid();
 350 
 351     /**
 352      * Returns the effective group ID of the calling process,
 353      * or -1 if the value is not available.
 354      */
 355     public static native long getegid();
 356 
 357     /**
 358      * Get a nanosecond time stamp adjustment in the form of a single long.
 359      *
 360      * This value can be used to create an instant using
 361      * {@link java.time.Instant#ofEpochSecond(long, long)
 362      *  java.time.Instant.ofEpochSecond(offsetInSeconds,
 363      *  getNanoTimeAdjustment(offsetInSeconds))}.
 364      * <p>
 365      * The value returned has the best resolution available to the JVM on
 366      * the current system.
 367      * This is usually down to microseconds - or tenth of microseconds -
 368      * depending on the OS/Hardware and the JVM implementation.
 369      *
 370      * @param offsetInSeconds The offset in seconds from which the nanosecond
 371      *        time stamp should be computed.
 372      *
 373      * @apiNote The offset should be recent enough - so that
 374      *         {@code offsetInSeconds} is within {@code +/- 2^32} seconds of the
 375      *         current UTC time. If the offset is too far off, {@code -1} will be
 376      *         returned. As such, {@code -1} must not be considered as a valid
 377      *         nano time adjustment, but as an exception value indicating
 378      *         that an offset closer to the current time should be used.
 379      *
 380      * @return A nanosecond time stamp adjustment in the form of a single long.
 381      *     If the offset is too far off the current time, this method returns -1.
 382      *     In that case, the caller should call this method again, passing a
 383      *     more accurate offset.
 384      */
 385     public static native long getNanoTimeAdjustment(long offsetInSeconds);
 386 
 387     /**
 388      * Returns the VM arguments for this runtime environment.
 389      *
 390      * @implNote
 391      * The HotSpot JVM processes the input arguments from multiple sources
 392      * in the following order:
 393      * 1. JAVA_TOOL_OPTIONS environment variable
 394      * 2. Options from JNI Invocation API
 395      * 3. _JAVA_OPTIONS environment variable
 396      *
 397      * If VM options file is specified via -XX:VMOptionsFile, the vm options
 398      * file is read and expanded in place of -XX:VMOptionFile option.
 399      */
 400     public static native String[] getRuntimeArguments();
 401 
 402     static {
 403         initialize();
 404     }
 405     private static native void initialize();
 406 
 407     /**
 408      * Initialize archived static fields in the given Class using archived
 409      * values from CDS dump time. Also initialize the classes of objects in
 410      * the archived graph referenced by those fields.
 411      *
 412      * Those static fields remain as uninitialized if there is no mapped CDS
 413      * java heap data or there is any error during initialization of the
 414      * object class in the archived graph.
 415      */
 416     public static native void initializeFromArchive(Class<?> c);


 417 }
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