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.text.NumberFormat;
31 import java.util.ArrayList;
32 import java.util.Collections;
33 import java.util.List;
34 import java.util.Map;
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 // 0, 1, 2, ...
50 private static volatile int initLevel;
51 private static final Object lock = new Object();
52
53 /**
54 * Sets the init level.
55 *
56 * @see java.lang.System#initPhase1
57 * @see java.lang.System#initPhase2
58 * @see java.lang.System#initPhase3
59 */
60 public static void initLevel(int value) {
61 synchronized (lock) {
62 if (value <= initLevel || value > SYSTEM_SHUTDOWN)
63 throw new InternalError("Bad level: " + value);
64 initLevel = value;
65 lock.notifyAll();
66 }
67 }
68
69 /**
70 * Returns the current init level.
71 */
72 public static int initLevel() {
73 return initLevel;
74 }
75
76 /**
77 * Waits for the init level to get the given value.
78 *
79 * @see java.lang.ref.Finalizer
80 */
81 public static void awaitInitLevel(int value) throws InterruptedException {
82 synchronized (lock) {
83 while (initLevel < value) {
84 lock.wait();
85 }
86 }
87 }
88
89 /**
90 * Returns {@code true} if the module system has been initialized.
91 * @see java.lang.System#initPhase2
92 */
93 public static boolean isModuleSystemInited() {
94 return VM.initLevel() >= MODULE_SYSTEM_INITED;
95 }
96
97 /**
98 * Returns {@code true} if the VM is fully initialized.
99 */
100 public static boolean isBooted() {
101 return initLevel >= SYSTEM_BOOTED;
102 }
103
104 /**
105 * Set shutdown state. Shutdown completes when all registered shutdown
106 * hooks have been run.
107 *
108 * @see java.lang.Shutdown
109 */
110 public static void shutdown() {
111 initLevel(SYSTEM_SHUTDOWN);
112 }
113
114 /**
115 * Returns {@code true} if the VM has been shutdown
116 */
117 public static boolean isShutdown() {
118 return initLevel == SYSTEM_SHUTDOWN;
119 }
120
121 // A user-settable upper limit on the maximum amount of allocatable direct
122 // buffer memory. This value may be changed during VM initialization if
123 // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
124 //
125 // The initial value of this field is arbitrary; during JRE initialization
126 // it will be reset to the value specified on the command line, if any,
127 // otherwise to Runtime.getRuntime().maxMemory().
128 //
129 private static long directMemory = 64 * 1024 * 1024;
130
131 // Returns the maximum amount of allocatable direct buffer memory.
132 // The directMemory variable is initialized during system initialization
133 // in the saveAndRemoveProperties method.
134 //
135 public static long maxDirectMemory() {
136 return directMemory;
137 }
138
139 // User-controllable flag that determines if direct buffers should be page
140 // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
141 // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
142 private static boolean pageAlignDirectMemory;
143
144 // Returns {@code true} if the direct buffers should be page aligned. This
145 // variable is initialized by saveAndRemoveProperties.
146 public static boolean isDirectMemoryPageAligned() {
147 return pageAlignDirectMemory;
148 }
149
150 private static int classFileMajorVersion;
151 private static int classFileMinorVersion;
152 private static final int PREVIEW_MINOR_VERSION = 65535;
153
154 /**
155 * Tests if the given version is a supported {@code class}
156 * file version.
157 *
158 * A {@code class} file depends on the preview features of Java SE {@code N}
159 * if the major version is {@code N} and the minor version is 65535.
160 * This method returns {@code true} if the given version is a supported
161 * {@code class} file version regardless of whether the preview features
162 * are enabled or not.
163 *
164 * @jvms 4.1 Table 4.1-A. class file format major versions
165 */
166 public static boolean isSupportedClassFileVersion(int major, int minor) {
167 if (major < 45 || major > classFileMajorVersion) return false;
168 // for major version is between 45 and 55 inclusive, the minor version may be any value
169 if (major < 56) return true;
170 // otherwise, the minor version must be 0 or 65535
171 return minor == 0 || minor == PREVIEW_MINOR_VERSION;
172 }
173
174 /**
175 * Tests if the given version is a supported {@code class}
176 * file version for module descriptor.
177 *
178 * major.minor version >= 53.0
179 */
180 public static boolean isSupportedModuleDescriptorVersion(int major, int minor) {
181 if (major < 53 || major > classFileMajorVersion) return false;
182 // for major version is between 45 and 55 inclusive, the minor version may be any value
183 if (major < 56) return true;
184 // otherwise, the minor version must be 0 or 65535
185 // preview features do not apply to module-info.class but JVMS allows it
186 return minor == 0 || minor == PREVIEW_MINOR_VERSION;
187 }
188
189 /**
190 * Returns true if the given class loader is the bootstrap class loader
191 * or the platform class loader.
192 */
193 public static boolean isSystemDomainLoader(ClassLoader loader) {
194 return loader == null || loader == ClassLoader.getPlatformClassLoader();
195 }
196
197 /**
198 * Returns the system property of the specified key saved at
199 * system initialization time. This method should only be used
200 * for the system properties that are not changed during runtime.
201 *
202 * Note that the saved system properties do not include
203 * the ones set by java.lang.VersionProps.init().
204 */
205 public static String getSavedProperty(String key) {
206 if (savedProps == null)
207 throw new IllegalStateException("Not yet initialized");
208
209 return savedProps.get(key);
210 }
211
212 /**
213 * Gets an unmodifiable view of the system properties saved at system
214 * initialization time. This method should only be used
215 * for the system properties that are not changed during runtime.
216 *
217 * Note that the saved system properties do not include
218 * the ones set by java.lang.VersionProps.init().
219 */
220 public static Map<String, String> getSavedProperties() {
221 if (savedProps == null)
222 throw new IllegalStateException("Not yet initialized");
223
224 return Collections.unmodifiableMap(savedProps);
225 }
226
227 private static Map<String, String> savedProps;
228
229 // Save a private copy of the system properties and remove
230 // the system properties that are not intended for public access.
231 //
232 // This method can only be invoked during system initialization.
233 public static void saveProperties(Map<String, String> props) {
234 if (initLevel() != 0)
235 throw new IllegalStateException("Wrong init level");
236
237 // only main thread is running at this time, so savedProps and
238 // its content will be correctly published to threads started later
239 if (savedProps == null) {
240 savedProps = props;
241 }
242
243 // Set the maximum amount of direct memory. This value is controlled
244 // by the vm option -XX:MaxDirectMemorySize=<size>.
245 // The maximum amount of allocatable direct buffer memory (in bytes)
246 // from the system property sun.nio.MaxDirectMemorySize set by the VM.
247 // If not set or set to -1, the max memory will be used
248 // The system property will be removed.
249 String s = props.get("sun.nio.MaxDirectMemorySize");
250 if (s == null || s.isEmpty() || s.equals("-1")) {
251 // -XX:MaxDirectMemorySize not given, take default
252 directMemory = Runtime.getRuntime().maxMemory();
253 } else {
254 long l = Long.parseLong(s);
255 if (l > -1)
256 directMemory = l;
257 }
258
259 // Check if direct buffers should be page aligned
260 s = props.get("sun.nio.PageAlignDirectMemory");
261 if ("true".equals(s))
262 pageAlignDirectMemory = true;
263
264 s = props.get("java.class.version");
265 int index = s.indexOf('.');
266 try {
267 classFileMajorVersion = Integer.valueOf(s.substring(0, index));
268 classFileMinorVersion = Integer.valueOf(s.substring(index+1, s.length()));
269 } catch (NumberFormatException e) {
270 throw new InternalError(e);
271 }
272 }
273
274 // Initialize any miscellaneous operating system settings that need to be
275 // set for the class libraries.
276 //
277 public static void initializeOSEnvironment() {
278 if (initLevel() == 0) {
279 OSEnvironment.initialize();
280 }
281 }
282
283 /* Current count of objects pending for finalization */
284 private static volatile int finalRefCount;
285
286 /* Peak count of objects pending for finalization */
287 private static volatile int peakFinalRefCount;
288
289 /*
290 * Gets the number of objects pending for finalization.
291 *
292 * @return the number of objects pending for finalization.
293 */
294 public static int getFinalRefCount() {
295 return finalRefCount;
296 }
297
298 /*
299 * Gets the peak number of objects pending for finalization.
300 *
301 * @return the peak number of objects pending for finalization.
302 */
303 public static int getPeakFinalRefCount() {
304 return peakFinalRefCount;
305 }
306
307 /*
308 * Add {@code n} to the objects pending for finalization count.
309 *
310 * @param n an integer value to be added to the objects pending
311 * for finalization count
312 */
313 public static void addFinalRefCount(int n) {
314 // The caller must hold lock to synchronize the update.
315
316 finalRefCount += n;
317 if (finalRefCount > peakFinalRefCount) {
318 peakFinalRefCount = finalRefCount;
319 }
320 }
321
322 /**
323 * Returns Thread.State for the given threadStatus
324 */
325 public static Thread.State toThreadState(int threadStatus) {
326 if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) {
327 return RUNNABLE;
328 } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) {
329 return BLOCKED;
330 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) {
331 return WAITING;
332 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) {
333 return TIMED_WAITING;
334 } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) {
335 return TERMINATED;
336 } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) {
337 return NEW;
338 } else {
339 return RUNNABLE;
340 }
341 }
342
343 /* The threadStatus field is set by the VM at state transition
344 * in the hotspot implementation. Its value is set according to
345 * the JVM TI specification GetThreadState function.
346 */
347 private static final int JVMTI_THREAD_STATE_ALIVE = 0x0001;
348 private static final int JVMTI_THREAD_STATE_TERMINATED = 0x0002;
349 private static final int JVMTI_THREAD_STATE_RUNNABLE = 0x0004;
350 private static final int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400;
351 private static final int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010;
352 private static final int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020;
353
354 /*
355 * Returns the first user-defined class loader up the execution stack,
356 * or the platform class loader if only code from the platform or
357 * bootstrap class loader is on the stack.
358 */
359 public static ClassLoader latestUserDefinedLoader() {
360 ClassLoader loader = latestUserDefinedLoader0();
361 return loader != null ? loader : ClassLoader.getPlatformClassLoader();
362 }
363
364 /*
365 * Returns the first user-defined class loader up the execution stack,
366 * or null if only code from the platform or bootstrap class loader is
367 * on the stack. VM does not keep a reference of platform loader and so
368 * it returns null.
369 *
370 * This method should be replaced with StackWalker::walk and then we can
371 * remove the logic in the VM.
372 */
373 private static native ClassLoader latestUserDefinedLoader0();
374
375 /**
376 * Returns {@code true} if we are in a set UID program.
377 */
378 public static boolean isSetUID() {
379 long uid = getuid();
380 long euid = geteuid();
381 long gid = getgid();
382 long egid = getegid();
383 return uid != euid || gid != egid;
384 }
385
386 /**
387 * Returns the real user ID of the calling process,
388 * or -1 if the value is not available.
389 */
390 public static native long getuid();
391
392 /**
393 * Returns the effective user ID of the calling process,
394 * or -1 if the value is not available.
395 */
396 public static native long geteuid();
397
398 /**
399 * Returns the real group ID of the calling process,
400 * or -1 if the value is not available.
401 */
402 public static native long getgid();
403
404 /**
405 * Returns the effective group ID of the calling process,
406 * or -1 if the value is not available.
407 */
408 public static native long getegid();
409
410 /**
411 * Get a nanosecond time stamp adjustment in the form of a single long.
412 *
413 * This value can be used to create an instant using
414 * {@link java.time.Instant#ofEpochSecond(long, long)
415 * java.time.Instant.ofEpochSecond(offsetInSeconds,
416 * getNanoTimeAdjustment(offsetInSeconds))}.
417 * <p>
418 * The value returned has the best resolution available to the JVM on
419 * the current system.
420 * This is usually down to microseconds - or tenth of microseconds -
421 * depending on the OS/Hardware and the JVM implementation.
422 *
423 * @param offsetInSeconds The offset in seconds from which the nanosecond
424 * time stamp should be computed.
425 *
426 * @apiNote The offset should be recent enough - so that
427 * {@code offsetInSeconds} is within {@code +/- 2^32} seconds of the
428 * current UTC time. If the offset is too far off, {@code -1} will be
429 * returned. As such, {@code -1} must not be considered as a valid
430 * nano time adjustment, but as an exception value indicating
431 * that an offset closer to the current time should be used.
432 *
433 * @return A nanosecond time stamp adjustment in the form of a single long.
434 * If the offset is too far off the current time, this method returns -1.
435 * In that case, the caller should call this method again, passing a
436 * more accurate offset.
437 */
438 public static native long getNanoTimeAdjustment(long offsetInSeconds);
439
440 /**
441 * Returns the VM arguments for this runtime environment.
442 *
443 * @implNote
444 * The HotSpot JVM processes the input arguments from multiple sources
445 * in the following order:
446 * 1. JAVA_TOOL_OPTIONS environment variable
447 * 2. Options from JNI Invocation API
448 * 3. _JAVA_OPTIONS environment variable
449 *
450 * If VM options file is specified via -XX:VMOptionsFile, the vm options
451 * file is read and expanded in place of -XX:VMOptionFile option.
452 */
453 public static native String[] getRuntimeArguments();
454
455 static {
456 initialize();
457 }
458 private static native void initialize();
459
460 /**
461 * Initialize archived static fields in the given Class using archived
462 * values from CDS dump time. Also initialize the classes of objects in
463 * the archived graph referenced by those fields.
464 *
465 * Those static fields remain as uninitialized if there is no mapped CDS
466 * java heap data or there is any error during initialization of the
467 * object class in the archived graph.
468 */
469 public static native void initializeFromArchive(Class<?> c);
470
471 public static native void defineArchivedModules(ClassLoader platformLoader, ClassLoader systemLoader);
472
473 public static native long getRandomSeedForCDSDump();
474
475 /**
476 * Check if CDS dynamic dumping is enabled via the DynamicDumpSharedSpaces flag.
477 */
478 public static native boolean isCDSDumpingEnabled();
479
480 /**
481 * Check if CDS sharing is enabled by via the UseSharedSpaces flag.
482 */
483 public static native boolean isCDSSharingEnabled();
484
485 /**
486 * Provides access to information on buffer usage.
487 */
488 public interface BufferPool {
489 String getName();
490 long getCount();
491 long getTotalCapacity();
492 long getMemoryUsed();
493 }
494
495 private static class BufferPoolsHolder {
496 static final List<BufferPool> BUFFER_POOLS;
497
498 static {
499 ArrayList<BufferPool> bufferPools = new ArrayList<>(3);
500 bufferPools.add(SharedSecrets.getJavaNioAccess().getDirectBufferPool());
501 bufferPools.add(FileChannelImpl.getMappedBufferPool());
502 bufferPools.add(FileChannelImpl.getSyncMappedBufferPool());
503
504 BUFFER_POOLS = Collections.unmodifiableList(bufferPools);
505 }
506 }
507
508 /**
509 * @return the list of buffer pools.
510 */
511 public static List<BufferPool> getBufferPools() {
512 return BufferPoolsHolder.BUFFER_POOLS;
513 }
514 }