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