1 /*
2 * Copyright (c) 1996, 2020, 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.ArrayList;
31 import java.util.Collections;
32 import java.util.List;
33 import java.util.Map;
34 import java.util.Properties;
35
36 import jdk.internal.access.SharedSecrets;
37
38 import sun.nio.ch.FileChannelImpl;
39
40 public class VM {
41
42 // the init level when the VM is fully initialized
43 private static final int JAVA_LANG_SYSTEM_INITED = 1;
44 private static final int MODULE_SYSTEM_INITED = 2;
45 private static final int SYSTEM_LOADER_INITIALIZING = 3;
46 private static final int SYSTEM_BOOTED = 4;
47 private static final int SYSTEM_SHUTDOWN = 5;
48
49
50 // 0, 1, 2, ...
51 private static volatile int initLevel;
52 private static final Object lock = new Object();
53
54 /**
55 * Sets the init level.
56 *
57 * @see java.lang.System#initPhase1
58 * @see java.lang.System#initPhase2
59 * @see java.lang.System#initPhase3
60 */
61 public static void initLevel(int value) {
62 synchronized (lock) {
63 if (value <= initLevel || value > SYSTEM_SHUTDOWN)
64 throw new InternalError("Bad level: " + value);
65 initLevel = value;
66 lock.notifyAll();
67 }
68 }
69
70 /**
71 * Returns the current init level.
72 */
73 public static int initLevel() {
74 return initLevel;
75 }
76
77 /**
78 * Waits for the init level to get the given value.
79 *
80 * @see java.lang.ref.Finalizer
81 */
82 public static void awaitInitLevel(int value) throws InterruptedException {
83 synchronized (lock) {
84 while (initLevel < value) {
85 lock.wait();
86 }
87 }
88 }
89
90 /**
91 * Returns {@code true} if the module system has been initialized.
92 * @see java.lang.System#initPhase2
93 */
94 public static boolean isModuleSystemInited() {
95 return VM.initLevel() >= MODULE_SYSTEM_INITED;
96 }
97
98 /**
99 * Returns {@code true} if the VM is fully initialized.
100 */
101 public static boolean isBooted() {
102 return initLevel >= SYSTEM_BOOTED;
103 }
104
105 /**
106 * Set shutdown state. Shutdown completes when all registered shutdown
107 * hooks have been run.
108 *
109 * @see java.lang.Shutdown
110 */
111 public static void shutdown() {
112 initLevel(SYSTEM_SHUTDOWN);
113 }
114
115 /**
116 * Returns {@code true} if the VM has been shutdown
117 */
118 public static boolean isShutdown() {
119 return initLevel == SYSTEM_SHUTDOWN;
120 }
121
122 // A user-settable upper limit on the maximum amount of allocatable direct
123 // buffer memory. This value may be changed during VM initialization if
124 // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
125 //
126 // The initial value of this field is arbitrary; during JRE initialization
127 // it will be reset to the value specified on the command line, if any,
128 // otherwise to Runtime.getRuntime().maxMemory().
129 //
130 private static long directMemory = 64 * 1024 * 1024;
131
132 // Returns the maximum amount of allocatable direct buffer memory.
133 // The directMemory variable is initialized during system initialization
134 // in the saveAndRemoveProperties method.
135 //
136 public static long maxDirectMemory() {
137 return directMemory;
138 }
139
140 // User-controllable flag that determines if direct buffers should be page
141 // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
142 // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
143 private static boolean pageAlignDirectMemory;
144
145 // Returns {@code true} if the direct buffers should be page aligned. This
146 // variable is initialized by saveAndRemoveProperties.
147 public static boolean isDirectMemoryPageAligned() {
148 return pageAlignDirectMemory;
149 }
150
151 /**
152 * Returns true if the given class loader is the bootstrap class loader
153 * or the platform class loader.
154 */
155 public static boolean isSystemDomainLoader(ClassLoader loader) {
156 return loader == null || loader == ClassLoader.getPlatformClassLoader();
157 }
158
159 /**
160 * Returns the system property of the specified key saved at
161 * system initialization time. This method should only be used
162 * for the system properties that are not changed during runtime.
163 *
164 * Note that the saved system properties do not include
165 * the ones set by java.lang.VersionProps.init().
166 */
167 public static String getSavedProperty(String key) {
168 if (savedProps == null)
169 throw new IllegalStateException("Not yet initialized");
170
171 return savedProps.get(key);
172 }
173
174 /**
175 * Gets an unmodifiable view of the system properties saved at system
176 * initialization time. This method should only be used
177 * for the system properties that are not changed during runtime.
178 *
179 * Note that the saved system properties do not include
180 * the ones set by java.lang.VersionProps.init().
181 */
182 public static Map<String, String> getSavedProperties() {
183 if (savedProps == null)
184 throw new IllegalStateException("Not yet initialized");
185
186 return Collections.unmodifiableMap(savedProps);
187 }
188
189 private static Map<String, String> savedProps;
190
191 // Save a private copy of the system properties and remove
192 // the system properties that are not intended for public access.
193 //
194 // This method can only be invoked during system initialization.
195 public static void saveProperties(Map<String, String> props) {
196 if (initLevel() != 0)
197 throw new IllegalStateException("Wrong init level");
198
199 // only main thread is running at this time, so savedProps and
200 // its content will be correctly published to threads started later
201 if (savedProps == null) {
202 savedProps = props;
203 }
204
205 // Set the maximum amount of direct memory. This value is controlled
206 // by the vm option -XX:MaxDirectMemorySize=<size>.
207 // The maximum amount of allocatable direct buffer memory (in bytes)
208 // from the system property sun.nio.MaxDirectMemorySize set by the VM.
209 // If not set or set to -1, the max memory will be used
210 // The system property will be removed.
211 String s = props.get("sun.nio.MaxDirectMemorySize");
212 if (s == null || s.isEmpty() || s.equals("-1")) {
213 // -XX:MaxDirectMemorySize not given, take default
214 directMemory = Runtime.getRuntime().maxMemory();
215 } else {
216 long l = Long.parseLong(s);
217 if (l > -1)
218 directMemory = l;
219 }
220
221 // Check if direct buffers should be page aligned
222 s = props.get("sun.nio.PageAlignDirectMemory");
223 if ("true".equals(s))
224 pageAlignDirectMemory = true;
225 }
226
227 // Initialize any miscellaneous operating system settings that need to be
228 // set for the class libraries.
229 //
230 public static void initializeOSEnvironment() {
231 if (initLevel() == 0) {
232 OSEnvironment.initialize();
233 }
234 }
235
236 /* Current count of objects pending for finalization */
237 private static volatile int finalRefCount;
238
239 /* Peak count of objects pending for finalization */
240 private static volatile int peakFinalRefCount;
241
242 /*
243 * Gets the number of objects pending for finalization.
244 *
245 * @return the number of objects pending for finalization.
246 */
247 public static int getFinalRefCount() {
248 return finalRefCount;
249 }
250
251 /*
252 * Gets the peak number of objects pending for finalization.
253 *
254 * @return the peak number of objects pending for finalization.
255 */
256 public static int getPeakFinalRefCount() {
257 return peakFinalRefCount;
258 }
259
260 /*
261 * Add {@code n} to the objects pending for finalization count.
262 *
263 * @param n an integer value to be added to the objects pending
264 * for finalization count
265 */
266 public static void addFinalRefCount(int n) {
267 // The caller must hold lock to synchronize the update.
268
269 finalRefCount += n;
270 if (finalRefCount > peakFinalRefCount) {
271 peakFinalRefCount = finalRefCount;
272 }
273 }
274
275 /**
276 * Returns Thread.State for the given threadStatus
277 */
278 public static Thread.State toThreadState(int threadStatus) {
279 if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) {
280 return RUNNABLE;
281 } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) {
282 return BLOCKED;
283 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) {
284 return WAITING;
285 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) {
286 return TIMED_WAITING;
287 } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) {
288 return TERMINATED;
289 } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) {
290 return NEW;
291 } else {
292 return RUNNABLE;
293 }
294 }
295
296 /* The threadStatus field is set by the VM at state transition
297 * in the hotspot implementation. Its value is set according to
298 * the JVM TI specification GetThreadState function.
299 */
300 private static final int JVMTI_THREAD_STATE_ALIVE = 0x0001;
301 private static final int JVMTI_THREAD_STATE_TERMINATED = 0x0002;
302 private static final int JVMTI_THREAD_STATE_RUNNABLE = 0x0004;
303 private static final int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400;
304 private static final int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010;
305 private static final int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020;
306
307 /*
308 * Returns the first user-defined class loader up the execution stack,
309 * or the platform class loader if only code from the platform or
310 * bootstrap class loader is on the stack.
311 */
312 public static ClassLoader latestUserDefinedLoader() {
313 ClassLoader loader = latestUserDefinedLoader0();
314 return loader != null ? loader : ClassLoader.getPlatformClassLoader();
315 }
316
317 /*
318 * Returns the first user-defined class loader up the execution stack,
319 * or null if only code from the platform or bootstrap class loader is
320 * on the stack. VM does not keep a reference of platform loader and so
321 * it returns null.
322 *
323 * This method should be replaced with StackWalker::walk and then we can
324 * remove the logic in the VM.
325 */
326 private static native ClassLoader latestUserDefinedLoader0();
327
328 /**
329 * Returns {@code true} if we are in a set UID program.
330 */
331 public static boolean isSetUID() {
332 long uid = getuid();
333 long euid = geteuid();
334 long gid = getgid();
335 long egid = getegid();
336 return uid != euid || gid != egid;
337 }
338
339 /**
340 * Returns the real user ID of the calling process,
341 * or -1 if the value is not available.
342 */
343 public static native long getuid();
344
345 /**
346 * Returns the effective user ID of the calling process,
347 * or -1 if the value is not available.
348 */
349 public static native long geteuid();
350
351 /**
352 * Returns the real group ID of the calling process,
353 * or -1 if the value is not available.
354 */
355 public static native long getgid();
356
357 /**
358 * Returns the effective group ID of the calling process,
359 * or -1 if the value is not available.
360 */
361 public static native long getegid();
362
363 /**
364 * Get a nanosecond time stamp adjustment in the form of a single long.
365 *
366 * This value can be used to create an instant using
367 * {@link java.time.Instant#ofEpochSecond(long, long)
368 * java.time.Instant.ofEpochSecond(offsetInSeconds,
369 * getNanoTimeAdjustment(offsetInSeconds))}.
370 * <p>
371 * The value returned has the best resolution available to the JVM on
372 * the current system.
373 * This is usually down to microseconds - or tenth of microseconds -
374 * depending on the OS/Hardware and the JVM implementation.
375 *
376 * @param offsetInSeconds The offset in seconds from which the nanosecond
377 * time stamp should be computed.
378 *
379 * @apiNote The offset should be recent enough - so that
380 * {@code offsetInSeconds} is within {@code +/- 2^32} seconds of the
381 * current UTC time. If the offset is too far off, {@code -1} will be
382 * returned. As such, {@code -1} must not be considered as a valid
383 * nano time adjustment, but as an exception value indicating
384 * that an offset closer to the current time should be used.
385 *
386 * @return A nanosecond time stamp adjustment in the form of a single long.
387 * If the offset is too far off the current time, this method returns -1.
388 * In that case, the caller should call this method again, passing a
389 * more accurate offset.
390 */
391 public static native long getNanoTimeAdjustment(long offsetInSeconds);
392
393 /**
394 * Returns the VM arguments for this runtime environment.
395 *
396 * @implNote
397 * The HotSpot JVM processes the input arguments from multiple sources
398 * in the following order:
399 * 1. JAVA_TOOL_OPTIONS environment variable
400 * 2. Options from JNI Invocation API
401 * 3. _JAVA_OPTIONS environment variable
402 *
403 * If VM options file is specified via -XX:VMOptionsFile, the vm options
404 * file is read and expanded in place of -XX:VMOptionFile option.
405 */
406 public static native String[] getRuntimeArguments();
407
408 static {
409 initialize();
410 }
411 private static native void initialize();
412
413 /**
414 * Initialize archived static fields in the given Class using archived
415 * values from CDS dump time. Also initialize the classes of objects in
416 * the archived graph referenced by those fields.
417 *
418 * Those static fields remain as uninitialized if there is no mapped CDS
419 * java heap data or there is any error during initialization of the
420 * object class in the archived graph.
421 */
422 public static native void initializeFromArchive(Class<?> c);
423
424 public static native long getRandomSeedForCDSDump();
425
426 /**
427 * Check if CDS dynamic dumping is enabled via the DynamicDumpSharedSpaces flag.
428 */
429 public static native boolean isCDSDumpingEnabled();
430
431 /**
432 * Check if CDS sharing is enabled by via the UseSharedSpaces flag.
433 */
434 public static native boolean isCDSSharingEnabled();
435
436 /**
437 * Provides access to information on buffer usage.
438 */
439 public interface BufferPool {
440 String getName();
441 long getCount();
442 long getTotalCapacity();
443 long getMemoryUsed();
444 }
445
446 private static class BufferPoolsHolder {
447 static final List<BufferPool> BUFFER_POOLS;
448
449 static {
450 ArrayList<BufferPool> bufferPools = new ArrayList<>(3);
451 bufferPools.add(SharedSecrets.getJavaNioAccess().getDirectBufferPool());
452 bufferPools.add(FileChannelImpl.getMappedBufferPool());
453 bufferPools.add(FileChannelImpl.getSyncMappedBufferPool());
454
455 BUFFER_POOLS = Collections.unmodifiableList(bufferPools);
456 }
457 }
458
459 /**
460 * @return the list of buffer pools.
461 */
462 public static List<BufferPool> getBufferPools() {
463 return BufferPoolsHolder.BUFFER_POOLS;
464 }
465 }