1 /*
2 * Copyright (c) 2000, 2021, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "jni.h"
27 #include "jvm.h"
28 #include "classfile/classFileStream.hpp"
29 #include "classfile/classLoader.hpp"
30 #include "classfile/classLoadInfo.hpp"
31 #include "classfile/javaClasses.inline.hpp"
32 #include "classfile/systemDictionary.hpp"
33 #include "classfile/vmSymbols.hpp"
34 #include "jfr/jfrEvents.hpp"
35 #include "memory/allocation.inline.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/access.inline.hpp"
38 #include "oops/fieldStreams.inline.hpp"
39 #include "oops/instanceKlass.inline.hpp"
40 #include "oops/klass.inline.hpp"
41 #include "oops/objArrayOop.inline.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "oops/typeArrayOop.inline.hpp"
44 #include "prims/unsafe.hpp"
45 #include "runtime/globals.hpp"
46 #include "runtime/handles.inline.hpp"
47 #include "runtime/interfaceSupport.inline.hpp"
48 #include "runtime/jniHandles.inline.hpp"
49 #include "runtime/orderAccess.hpp"
50 #include "runtime/reflection.hpp"
51 #include "runtime/sharedRuntime.hpp"
52 #include "runtime/stubRoutines.hpp"
53 #include "runtime/thread.hpp"
54 #include "runtime/threadSMR.hpp"
55 #include "runtime/vmOperations.hpp"
56 #include "runtime/vm_version.hpp"
57 #include "services/threadService.hpp"
58 #include "utilities/align.hpp"
59 #include "utilities/copy.hpp"
60 #include "utilities/dtrace.hpp"
61 #include "utilities/macros.hpp"
62
63 /**
64 * Implementation of the jdk.internal.misc.Unsafe class
65 */
66
67
68 #define MAX_OBJECT_SIZE \
69 ( arrayOopDesc::header_size(T_DOUBLE) * HeapWordSize \
70 + ((julong)max_jint * sizeof(double)) )
71
72
73 #define UNSAFE_ENTRY(result_type, header) \
74 JVM_ENTRY(static result_type, header)
75
76 #define UNSAFE_LEAF(result_type, header) \
77 JVM_LEAF(static result_type, header)
78
79 #define UNSAFE_END JVM_END
80
81
82 static inline void* addr_from_java(jlong addr) {
83 // This assert fails in a variety of ways on 32-bit systems.
84 // It is impossible to predict whether native code that converts
85 // pointers to longs will sign-extend or zero-extend the addresses.
86 //assert(addr == (uintptr_t)addr, "must not be odd high bits");
87 return (void*)(uintptr_t)addr;
88 }
89
90 static inline jlong addr_to_java(void* p) {
91 assert(p == (void*)(uintptr_t)p, "must not be odd high bits");
92 return (uintptr_t)p;
93 }
94
95
96 // Note: The VM's obj_field and related accessors use byte-scaled
97 // ("unscaled") offsets, just as the unsafe methods do.
98
99 // However, the method Unsafe.fieldOffset explicitly declines to
100 // guarantee this. The field offset values manipulated by the Java user
101 // through the Unsafe API are opaque cookies that just happen to be byte
102 // offsets. We represent this state of affairs by passing the cookies
103 // through conversion functions when going between the VM and the Unsafe API.
104 // The conversion functions just happen to be no-ops at present.
105
106 static inline jlong field_offset_to_byte_offset(jlong field_offset) {
107 return field_offset;
108 }
109
110 static inline jlong field_offset_from_byte_offset(jlong byte_offset) {
111 return byte_offset;
112 }
113
114 static inline void assert_field_offset_sane(oop p, jlong field_offset) {
115 #ifdef ASSERT
116 jlong byte_offset = field_offset_to_byte_offset(field_offset);
117
118 if (p != NULL) {
119 assert(byte_offset >= 0 && byte_offset <= (jlong)MAX_OBJECT_SIZE, "sane offset");
120 if (byte_offset == (jint)byte_offset) {
121 void* ptr_plus_disp = cast_from_oop<address>(p) + byte_offset;
122 assert(p->field_addr((jint)byte_offset) == ptr_plus_disp,
123 "raw [ptr+disp] must be consistent with oop::field_addr");
124 }
125 jlong p_size = HeapWordSize * (jlong)(p->size());
126 assert(byte_offset < p_size, "Unsafe access: offset " INT64_FORMAT " > object's size " INT64_FORMAT, (int64_t)byte_offset, (int64_t)p_size);
127 }
128 #endif
129 }
130
131 static inline void* index_oop_from_field_offset_long(oop p, jlong field_offset) {
132 assert_field_offset_sane(p, field_offset);
133 jlong byte_offset = field_offset_to_byte_offset(field_offset);
134
135 if (sizeof(char*) == sizeof(jint)) { // (this constant folds!)
136 return cast_from_oop<address>(p) + (jint) byte_offset;
137 } else {
138 return cast_from_oop<address>(p) + byte_offset;
139 }
140 }
141
142 // Externally callable versions:
143 // (Use these in compiler intrinsics which emulate unsafe primitives.)
144 jlong Unsafe_field_offset_to_byte_offset(jlong field_offset) {
145 return field_offset;
146 }
147 jlong Unsafe_field_offset_from_byte_offset(jlong byte_offset) {
148 return byte_offset;
149 }
150
151
152 ///// Data read/writes on the Java heap and in native (off-heap) memory
153
154 /**
155 * Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
156 */
157 class GuardUnsafeAccess {
158 JavaThread* _thread;
159
160 public:
161 GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
162 // native/off-heap access which may raise SIGBUS if accessing
163 // memory mapped file data in a region of the file which has
164 // been truncated and is now invalid.
165 _thread->set_doing_unsafe_access(true);
166 }
167
168 ~GuardUnsafeAccess() {
169 _thread->set_doing_unsafe_access(false);
170 }
171 };
172
173 /**
174 * Helper class for accessing memory.
175 *
176 * Normalizes values and wraps accesses in
177 * JavaThread::doing_unsafe_access() if needed.
178 */
179 template <typename T>
180 class MemoryAccess : StackObj {
181 JavaThread* _thread;
182 oop _obj;
183 ptrdiff_t _offset;
184
185 // Resolves and returns the address of the memory access.
186 // This raw memory access may fault, so we make sure it happens within the
187 // guarded scope by making the access volatile at least. Since the store
188 // of Thread::set_doing_unsafe_access() is also volatile, these accesses
189 // can not be reordered by the compiler. Therefore, if the access triggers
190 // a fault, we will know that Thread::doing_unsafe_access() returns true.
191 volatile T* addr() {
192 void* addr = index_oop_from_field_offset_long(_obj, _offset);
193 return static_cast<volatile T*>(addr);
194 }
195
196 template <typename U>
197 U normalize_for_write(U x) {
198 return x;
199 }
200
201 jboolean normalize_for_write(jboolean x) {
202 return x & 1;
203 }
204
205 template <typename U>
206 U normalize_for_read(U x) {
207 return x;
208 }
209
210 jboolean normalize_for_read(jboolean x) {
211 return x != 0;
212 }
213
214 public:
215 MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
216 : _thread(thread), _obj(JNIHandles::resolve(obj)), _offset((ptrdiff_t)offset) {
217 assert_field_offset_sane(_obj, offset);
218 }
219
220 T get() {
221 if (_obj == NULL) {
222 GuardUnsafeAccess guard(_thread);
223 T ret = RawAccess<>::load(addr());
224 return normalize_for_read(ret);
225 } else {
226 T ret = HeapAccess<>::load_at(_obj, _offset);
227 return normalize_for_read(ret);
228 }
229 }
230
231 void put(T x) {
232 if (_obj == NULL) {
233 GuardUnsafeAccess guard(_thread);
234 RawAccess<>::store(addr(), normalize_for_write(x));
235 } else {
236 HeapAccess<>::store_at(_obj, _offset, normalize_for_write(x));
237 }
238 }
239
240
241 T get_volatile() {
242 if (_obj == NULL) {
243 GuardUnsafeAccess guard(_thread);
244 volatile T ret = RawAccess<MO_SEQ_CST>::load(addr());
245 return normalize_for_read(ret);
246 } else {
247 T ret = HeapAccess<MO_SEQ_CST>::load_at(_obj, _offset);
248 return normalize_for_read(ret);
249 }
250 }
251
252 void put_volatile(T x) {
253 if (_obj == NULL) {
254 GuardUnsafeAccess guard(_thread);
255 RawAccess<MO_SEQ_CST>::store(addr(), normalize_for_write(x));
256 } else {
257 HeapAccess<MO_SEQ_CST>::store_at(_obj, _offset, normalize_for_write(x));
258 }
259 }
260 };
261
262 // These functions allow a null base pointer with an arbitrary address.
263 // But if the base pointer is non-null, the offset should make some sense.
264 // That is, it should be in the range [0, MAX_OBJECT_SIZE].
265 UNSAFE_ENTRY(jobject, Unsafe_GetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
266 oop p = JNIHandles::resolve(obj);
267 assert_field_offset_sane(p, offset);
268 oop v = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
269 return JNIHandles::make_local(THREAD, v);
270 } UNSAFE_END
271
272 UNSAFE_ENTRY(void, Unsafe_PutReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
273 oop x = JNIHandles::resolve(x_h);
274 oop p = JNIHandles::resolve(obj);
275 assert_field_offset_sane(p, offset);
276 HeapAccess<ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
277 } UNSAFE_END
278
279 UNSAFE_ENTRY(jobject, Unsafe_GetReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
280 oop p = JNIHandles::resolve(obj);
281 assert_field_offset_sane(p, offset);
282 oop v = HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
283 return JNIHandles::make_local(THREAD, v);
284 } UNSAFE_END
285
286 UNSAFE_ENTRY(void, Unsafe_PutReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
287 oop x = JNIHandles::resolve(x_h);
288 oop p = JNIHandles::resolve(obj);
289 assert_field_offset_sane(p, offset);
290 HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
291 } UNSAFE_END
292
293 UNSAFE_ENTRY(jobject, Unsafe_GetUncompressedObject(JNIEnv *env, jobject unsafe, jlong addr)) {
294 oop v = *(oop*) (address) addr;
295 return JNIHandles::make_local(THREAD, v);
296 } UNSAFE_END
297
298 #define DEFINE_GETSETOOP(java_type, Type) \
299 \
300 UNSAFE_ENTRY(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
301 return MemoryAccess<java_type>(thread, obj, offset).get(); \
302 } UNSAFE_END \
303 \
304 UNSAFE_ENTRY(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
305 MemoryAccess<java_type>(thread, obj, offset).put(x); \
306 } UNSAFE_END \
307 \
308 // END DEFINE_GETSETOOP.
309
310 DEFINE_GETSETOOP(jboolean, Boolean)
311 DEFINE_GETSETOOP(jbyte, Byte)
312 DEFINE_GETSETOOP(jshort, Short);
313 DEFINE_GETSETOOP(jchar, Char);
314 DEFINE_GETSETOOP(jint, Int);
315 DEFINE_GETSETOOP(jlong, Long);
316 DEFINE_GETSETOOP(jfloat, Float);
317 DEFINE_GETSETOOP(jdouble, Double);
318
319 #undef DEFINE_GETSETOOP
320
321 #define DEFINE_GETSETOOP_VOLATILE(java_type, Type) \
322 \
323 UNSAFE_ENTRY(java_type, Unsafe_Get##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
324 return MemoryAccess<java_type>(thread, obj, offset).get_volatile(); \
325 } UNSAFE_END \
326 \
327 UNSAFE_ENTRY(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
328 MemoryAccess<java_type>(thread, obj, offset).put_volatile(x); \
329 } UNSAFE_END \
330 \
331 // END DEFINE_GETSETOOP_VOLATILE.
332
333 DEFINE_GETSETOOP_VOLATILE(jboolean, Boolean)
334 DEFINE_GETSETOOP_VOLATILE(jbyte, Byte)
335 DEFINE_GETSETOOP_VOLATILE(jshort, Short);
336 DEFINE_GETSETOOP_VOLATILE(jchar, Char);
337 DEFINE_GETSETOOP_VOLATILE(jint, Int);
338 DEFINE_GETSETOOP_VOLATILE(jlong, Long);
339 DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
340 DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
341
342 #undef DEFINE_GETSETOOP_VOLATILE
343
344 UNSAFE_LEAF(void, Unsafe_LoadFence(JNIEnv *env, jobject unsafe)) {
345 OrderAccess::acquire();
346 } UNSAFE_END
347
348 UNSAFE_LEAF(void, Unsafe_StoreFence(JNIEnv *env, jobject unsafe)) {
349 OrderAccess::release();
350 } UNSAFE_END
351
352 UNSAFE_LEAF(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe)) {
353 OrderAccess::fence();
354 } UNSAFE_END
355
356 ////// Allocation requests
357
358 UNSAFE_ENTRY(jobject, Unsafe_AllocateInstance(JNIEnv *env, jobject unsafe, jclass cls)) {
359 instanceOop i = InstanceKlass::allocate_instance(JNIHandles::resolve_non_null(cls), CHECK_NULL);
360 return JNIHandles::make_local(THREAD, i);
361 } UNSAFE_END
362
363 UNSAFE_ENTRY(jlong, Unsafe_AllocateMemory0(JNIEnv *env, jobject unsafe, jlong size)) {
364 size_t sz = (size_t)size;
365
366 assert(is_aligned(sz, HeapWordSize), "sz not aligned");
367
368 void* x = os::malloc(sz, mtOther);
369
370 return addr_to_java(x);
371 } UNSAFE_END
372
373 UNSAFE_ENTRY(jlong, Unsafe_ReallocateMemory0(JNIEnv *env, jobject unsafe, jlong addr, jlong size)) {
374 void* p = addr_from_java(addr);
375 size_t sz = (size_t)size;
376
377 assert(is_aligned(sz, HeapWordSize), "sz not aligned");
378
379 void* x = os::realloc(p, sz, mtOther);
380
381 return addr_to_java(x);
382 } UNSAFE_END
383
384 UNSAFE_ENTRY(void, Unsafe_FreeMemory0(JNIEnv *env, jobject unsafe, jlong addr)) {
385 void* p = addr_from_java(addr);
386
387 os::free(p);
388 } UNSAFE_END
389
390 UNSAFE_ENTRY(void, Unsafe_SetMemory0(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong size, jbyte value)) {
391 size_t sz = (size_t)size;
392
393 oop base = JNIHandles::resolve(obj);
394 void* p = index_oop_from_field_offset_long(base, offset);
395
396 Copy::fill_to_memory_atomic(p, sz, value);
397 } UNSAFE_END
398
399 UNSAFE_ENTRY(void, Unsafe_CopyMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size)) {
400 size_t sz = (size_t)size;
401
402 oop srcp = JNIHandles::resolve(srcObj);
403 oop dstp = JNIHandles::resolve(dstObj);
404
405 void* src = index_oop_from_field_offset_long(srcp, srcOffset);
406 void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
407 {
408 GuardUnsafeAccess guard(thread);
409 if (StubRoutines::unsafe_arraycopy() != NULL) {
410 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
411 StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
412 } else {
413 Copy::conjoint_memory_atomic(src, dst, sz);
414 }
415 }
416 } UNSAFE_END
417
418 // This function is a leaf since if the source and destination are both in native memory
419 // the copy may potentially be very large, and we don't want to disable GC if we can avoid it.
420 // If either source or destination (or both) are on the heap, the function will enter VM using
421 // JVM_ENTRY_FROM_LEAF
422 UNSAFE_LEAF(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
423 size_t sz = (size_t)size;
424 size_t esz = (size_t)elemSize;
425
426 if (srcObj == NULL && dstObj == NULL) {
427 // Both src & dst are in native memory
428 address src = (address)srcOffset;
429 address dst = (address)dstOffset;
430
431 {
432 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
433 GuardUnsafeAccess guard(thread);
434 Copy::conjoint_swap(src, dst, sz, esz);
435 }
436 } else {
437 // At least one of src/dst are on heap, transition to VM to access raw pointers
438
439 JVM_ENTRY_FROM_LEAF(env, void, Unsafe_CopySwapMemory0) {
440 oop srcp = JNIHandles::resolve(srcObj);
441 oop dstp = JNIHandles::resolve(dstObj);
442
443 address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
444 address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
445
446 {
447 GuardUnsafeAccess guard(thread);
448 Copy::conjoint_swap(src, dst, sz, esz);
449 }
450 } JVM_END
451 }
452 } UNSAFE_END
453
454 UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
455 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
456 #ifdef ASSERT
457 if (TraceMemoryWriteback) {
458 tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
459 }
460 #endif
461
462 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
463 assert(StubRoutines::data_cache_writeback() != NULL, "sanity");
464 (StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
465 } UNSAFE_END
466
467 static void doWriteBackSync0(bool is_pre)
468 {
469 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
470 assert(StubRoutines::data_cache_writeback_sync() != NULL, "sanity");
471 (StubRoutines::DataCacheWritebackSync_stub())(is_pre);
472 }
473
474 UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
475 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
476 #ifdef ASSERT
477 if (TraceMemoryWriteback) {
478 tty->print_cr("Unsafe: writeback pre-sync");
479 }
480 #endif
481
482 doWriteBackSync0(true);
483 } UNSAFE_END
484
485 UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
486 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
487 #ifdef ASSERT
488 if (TraceMemoryWriteback) {
489 tty->print_cr("Unsafe: writeback pre-sync");
490 }
491 #endif
492
493 doWriteBackSync0(false);
494 } UNSAFE_END
495
496 ////// Random queries
497
498 static jlong find_field_offset(jclass clazz, jstring name, TRAPS) {
499 assert(clazz != NULL, "clazz must not be NULL");
500 assert(name != NULL, "name must not be NULL");
501
502 ResourceMark rm(THREAD);
503 char *utf_name = java_lang_String::as_utf8_string(JNIHandles::resolve_non_null(name));
504
505 InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(clazz)));
506
507 jint offset = -1;
508 for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
509 Symbol *name = fs.name();
510 if (name->equals(utf_name)) {
511 offset = fs.offset();
512 break;
513 }
514 }
515 if (offset < 0) {
516 THROW_0(vmSymbols::java_lang_InternalError());
517 }
518 return field_offset_from_byte_offset(offset);
519 }
520
521 static jlong find_field_offset(jobject field, int must_be_static, TRAPS) {
522 assert(field != NULL, "field must not be NULL");
523
524 oop reflected = JNIHandles::resolve_non_null(field);
525 oop mirror = java_lang_reflect_Field::clazz(reflected);
526 Klass* k = java_lang_Class::as_Klass(mirror);
527 int slot = java_lang_reflect_Field::slot(reflected);
528 int modifiers = java_lang_reflect_Field::modifiers(reflected);
529
530 if (must_be_static >= 0) {
531 int really_is_static = ((modifiers & JVM_ACC_STATIC) != 0);
532 if (must_be_static != really_is_static) {
533 THROW_0(vmSymbols::java_lang_IllegalArgumentException());
534 }
535 }
536
537 int offset = InstanceKlass::cast(k)->field_offset(slot);
538 return field_offset_from_byte_offset(offset);
539 }
540
541 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
542 return find_field_offset(field, 0, THREAD);
543 } UNSAFE_END
544
545 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset1(JNIEnv *env, jobject unsafe, jclass c, jstring name)) {
546 return find_field_offset(c, name, THREAD);
547 } UNSAFE_END
548
549 UNSAFE_ENTRY(jlong, Unsafe_StaticFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
550 return find_field_offset(field, 1, THREAD);
551 } UNSAFE_END
552
553 UNSAFE_ENTRY(jobject, Unsafe_StaticFieldBase0(JNIEnv *env, jobject unsafe, jobject field)) {
554 assert(field != NULL, "field must not be NULL");
555
556 // Note: In this VM implementation, a field address is always a short
557 // offset from the base of a a klass metaobject. Thus, the full dynamic
558 // range of the return type is never used. However, some implementations
559 // might put the static field inside an array shared by many classes,
560 // or even at a fixed address, in which case the address could be quite
561 // large. In that last case, this function would return NULL, since
562 // the address would operate alone, without any base pointer.
563
564 oop reflected = JNIHandles::resolve_non_null(field);
565 oop mirror = java_lang_reflect_Field::clazz(reflected);
566 int modifiers = java_lang_reflect_Field::modifiers(reflected);
567
568 if ((modifiers & JVM_ACC_STATIC) == 0) {
569 THROW_0(vmSymbols::java_lang_IllegalArgumentException());
570 }
571
572 return JNIHandles::make_local(THREAD, mirror);
573 } UNSAFE_END
574
575 UNSAFE_ENTRY(void, Unsafe_EnsureClassInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
576 assert(clazz != NULL, "clazz must not be NULL");
577
578 oop mirror = JNIHandles::resolve_non_null(clazz);
579
580 Klass* klass = java_lang_Class::as_Klass(mirror);
581 if (klass != NULL && klass->should_be_initialized()) {
582 InstanceKlass* k = InstanceKlass::cast(klass);
583 k->initialize(CHECK);
584 }
585 }
586 UNSAFE_END
587
588 UNSAFE_ENTRY(jboolean, Unsafe_ShouldBeInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
589 assert(clazz != NULL, "clazz must not be NULL");
590
591 oop mirror = JNIHandles::resolve_non_null(clazz);
592 Klass* klass = java_lang_Class::as_Klass(mirror);
593
594 if (klass != NULL && klass->should_be_initialized()) {
595 return true;
596 }
597
598 return false;
599 }
600 UNSAFE_END
601
602 static void getBaseAndScale(int& base, int& scale, jclass clazz, TRAPS) {
603 assert(clazz != NULL, "clazz must not be NULL");
604
605 oop mirror = JNIHandles::resolve_non_null(clazz);
606 Klass* k = java_lang_Class::as_Klass(mirror);
607
608 if (k == NULL || !k->is_array_klass()) {
609 THROW(vmSymbols::java_lang_InvalidClassException());
610 } else if (k->is_objArray_klass()) {
611 base = arrayOopDesc::base_offset_in_bytes(T_OBJECT);
612 scale = heapOopSize;
613 } else if (k->is_typeArray_klass()) {
614 TypeArrayKlass* tak = TypeArrayKlass::cast(k);
615 base = tak->array_header_in_bytes();
616 assert(base == arrayOopDesc::base_offset_in_bytes(tak->element_type()), "array_header_size semantics ok");
617 scale = (1 << tak->log2_element_size());
618 } else {
619 ShouldNotReachHere();
620 }
621 }
622
623 UNSAFE_ENTRY(jint, Unsafe_ArrayBaseOffset0(JNIEnv *env, jobject unsafe, jclass clazz)) {
624 int base = 0, scale = 0;
625 getBaseAndScale(base, scale, clazz, CHECK_0);
626
627 return field_offset_from_byte_offset(base);
628 } UNSAFE_END
629
630
631 UNSAFE_ENTRY(jint, Unsafe_ArrayIndexScale0(JNIEnv *env, jobject unsafe, jclass clazz)) {
632 int base = 0, scale = 0;
633 getBaseAndScale(base, scale, clazz, CHECK_0);
634
635 // This VM packs both fields and array elements down to the byte.
636 // But watch out: If this changes, so that array references for
637 // a given primitive type (say, T_BOOLEAN) use different memory units
638 // than fields, this method MUST return zero for such arrays.
639 // For example, the VM used to store sub-word sized fields in full
640 // words in the object layout, so that accessors like getByte(Object,int)
641 // did not really do what one might expect for arrays. Therefore,
642 // this function used to report a zero scale factor, so that the user
643 // would know not to attempt to access sub-word array elements.
644 // // Code for unpacked fields:
645 // if (scale < wordSize) return 0;
646
647 // The following allows for a pretty general fieldOffset cookie scheme,
648 // but requires it to be linear in byte offset.
649 return field_offset_from_byte_offset(scale) - field_offset_from_byte_offset(0);
650 } UNSAFE_END
651
652
653 static inline void throw_new(JNIEnv *env, const char *ename) {
654 jclass cls = env->FindClass(ename);
655 if (env->ExceptionCheck()) {
656 env->ExceptionClear();
657 tty->print_cr("Unsafe: cannot throw %s because FindClass has failed", ename);
658 return;
659 }
660
661 env->ThrowNew(cls, NULL);
662 }
663
664 static jclass Unsafe_DefineClass_impl(JNIEnv *env, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd) {
665 // Code lifted from JDK 1.3 ClassLoader.c
666
667 jbyte *body;
668 char *utfName = NULL;
669 jclass result = 0;
670 char buf[128];
671
672 assert(data != NULL, "Class bytes must not be NULL");
673 assert(length >= 0, "length must not be negative: %d", length);
674
675 if (UsePerfData) {
676 ClassLoader::unsafe_defineClassCallCounter()->inc();
677 }
678
679 body = NEW_C_HEAP_ARRAY_RETURN_NULL(jbyte, length, mtInternal);
680 if (body == NULL) {
681 throw_new(env, "java/lang/OutOfMemoryError");
682 return 0;
683 }
684
685 env->GetByteArrayRegion(data, offset, length, body);
686 if (env->ExceptionOccurred()) {
687 goto free_body;
688 }
689
690 if (name != NULL) {
691 uint len = env->GetStringUTFLength(name);
692 int unicode_len = env->GetStringLength(name);
693
694 if (len >= sizeof(buf)) {
695 utfName = NEW_C_HEAP_ARRAY_RETURN_NULL(char, len + 1, mtInternal);
696 if (utfName == NULL) {
697 throw_new(env, "java/lang/OutOfMemoryError");
698 goto free_body;
699 }
700 } else {
701 utfName = buf;
702 }
703
704 env->GetStringUTFRegion(name, 0, unicode_len, utfName);
705
706 for (uint i = 0; i < len; i++) {
707 if (utfName[i] == '.') utfName[i] = '/';
708 }
709 }
710
711 result = JVM_DefineClass(env, utfName, loader, body, length, pd);
712
713 if (utfName && utfName != buf) {
714 FREE_C_HEAP_ARRAY(char, utfName);
715 }
716
717 free_body:
718 FREE_C_HEAP_ARRAY(jbyte, body);
719 return result;
720 }
721
722
723 UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd)) {
724 ThreadToNativeFromVM ttnfv(thread);
725
726 return Unsafe_DefineClass_impl(env, name, data, offset, length, loader, pd);
727 } UNSAFE_END
728
729
730 UNSAFE_ENTRY(void, Unsafe_ThrowException(JNIEnv *env, jobject unsafe, jthrowable thr)) {
731 ThreadToNativeFromVM ttnfv(thread);
732 env->Throw(thr);
733 } UNSAFE_END
734
735 // JSR166 ------------------------------------------------------------------
736
737 UNSAFE_ENTRY(jobject, Unsafe_CompareAndExchangeReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
738 oop x = JNIHandles::resolve(x_h);
739 oop e = JNIHandles::resolve(e_h);
740 oop p = JNIHandles::resolve(obj);
741 assert_field_offset_sane(p, offset);
742 oop res = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
743 return JNIHandles::make_local(THREAD, res);
744 } UNSAFE_END
745
746 UNSAFE_ENTRY(jint, Unsafe_CompareAndExchangeInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
747 oop p = JNIHandles::resolve(obj);
748 if (p == NULL) {
749 volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
750 return RawAccess<>::atomic_cmpxchg(addr, e, x);
751 } else {
752 assert_field_offset_sane(p, offset);
753 return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
754 }
755 } UNSAFE_END
756
757 UNSAFE_ENTRY(jlong, Unsafe_CompareAndExchangeLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
758 oop p = JNIHandles::resolve(obj);
759 if (p == NULL) {
760 volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
761 return RawAccess<>::atomic_cmpxchg(addr, e, x);
762 } else {
763 assert_field_offset_sane(p, offset);
764 return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
765 }
766 } UNSAFE_END
767
768 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
769 oop x = JNIHandles::resolve(x_h);
770 oop e = JNIHandles::resolve(e_h);
771 oop p = JNIHandles::resolve(obj);
772 assert_field_offset_sane(p, offset);
773 oop ret = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
774 return ret == e;
775 } UNSAFE_END
776
777 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
778 oop p = JNIHandles::resolve(obj);
779 if (p == NULL) {
780 volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
781 return RawAccess<>::atomic_cmpxchg(addr, e, x) == e;
782 } else {
783 assert_field_offset_sane(p, offset);
784 return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x) == e;
785 }
786 } UNSAFE_END
787
788 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
789 oop p = JNIHandles::resolve(obj);
790 if (p == NULL) {
791 volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
792 return RawAccess<>::atomic_cmpxchg(addr, e, x) == e;
793 } else {
794 assert_field_offset_sane(p, offset);
795 return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x) == e;
796 }
797 } UNSAFE_END
798
799 static void post_thread_park_event(EventThreadPark* event, const oop obj, jlong timeout_nanos, jlong until_epoch_millis) {
800 assert(event != NULL, "invariant");
801 event->set_parkedClass((obj != NULL) ? obj->klass() : NULL);
802 event->set_timeout(timeout_nanos);
803 event->set_until(until_epoch_millis);
804 event->set_address((obj != NULL) ? (u8)cast_from_oop<uintptr_t>(obj) : 0);
805 event->commit();
806 }
807
808 UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time)) {
809 HOTSPOT_THREAD_PARK_BEGIN((uintptr_t) thread->parker(), (int) isAbsolute, time);
810 EventThreadPark event;
811
812 JavaThreadParkedState jtps(thread, time != 0);
813 thread->parker()->park(isAbsolute != 0, time);
814 if (event.should_commit()) {
815 const oop obj = thread->current_park_blocker();
816 if (time == 0) {
817 post_thread_park_event(&event, obj, min_jlong, min_jlong);
818 } else {
819 if (isAbsolute != 0) {
820 post_thread_park_event(&event, obj, min_jlong, time);
821 } else {
822 post_thread_park_event(&event, obj, time, min_jlong);
823 }
824 }
825 }
826 HOTSPOT_THREAD_PARK_END((uintptr_t) thread->parker());
827 } UNSAFE_END
828
829 UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread)) {
830 if (jthread != NULL) {
831 oop thread_oop = JNIHandles::resolve_non_null(jthread);
832 // Get the JavaThread* stored in the java.lang.Thread object _before_
833 // the embedded ThreadsListHandle is constructed so we know if the
834 // early life stage of the JavaThread* is protected. We use acquire
835 // here to ensure that if we see a non-nullptr value, then we also
836 // see the main ThreadsList updates from the JavaThread* being added.
837 FastThreadsListHandle ftlh(thread_oop, java_lang_Thread::thread_acquire(thread_oop));
838 JavaThread* thr = ftlh.protected_java_thread();
839 if (thr != nullptr) {
840 // The still live JavaThread* is protected by the FastThreadsListHandle
841 // so it is safe to access.
842 Parker* p = thr->parker();
843 HOTSPOT_THREAD_UNPARK((uintptr_t) p);
844 p->unpark();
845 }
846 } // FastThreadsListHandle is destroyed here.
847 } UNSAFE_END
848
849 UNSAFE_ENTRY(jint, Unsafe_GetLoadAverage0(JNIEnv *env, jobject unsafe, jdoubleArray loadavg, jint nelem)) {
850 const int max_nelem = 3;
851 double la[max_nelem];
852 jint ret;
853
854 typeArrayOop a = typeArrayOop(JNIHandles::resolve_non_null(loadavg));
855 assert(a->is_typeArray(), "must be type array");
856
857 ret = os::loadavg(la, nelem);
858 if (ret == -1) {
859 return -1;
860 }
861
862 // if successful, ret is the number of samples actually retrieved.
863 assert(ret >= 0 && ret <= max_nelem, "Unexpected loadavg return value");
864 switch(ret) {
865 case 3: a->double_at_put(2, (jdouble)la[2]); // fall through
866 case 2: a->double_at_put(1, (jdouble)la[1]); // fall through
867 case 1: a->double_at_put(0, (jdouble)la[0]); break;
868 }
869
870 return ret;
871 } UNSAFE_END
872
873
874 /// JVM_RegisterUnsafeMethods
875
876 #define ADR "J"
877
878 #define LANG "Ljava/lang/"
879
880 #define OBJ LANG "Object;"
881 #define CLS LANG "Class;"
882 #define FLD LANG "reflect/Field;"
883 #define THR LANG "Throwable;"
884
885 #define DC_Args LANG "String;[BII" LANG "ClassLoader;" "Ljava/security/ProtectionDomain;"
886 #define DAC_Args CLS "[B[" OBJ
887
888 #define CC (char*) /*cast a literal from (const char*)*/
889 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
890
891 #define DECLARE_GETPUTOOP(Type, Desc) \
892 {CC "get" #Type, CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type)}, \
893 {CC "put" #Type, CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type)}, \
894 {CC "get" #Type "Volatile", CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type##Volatile)}, \
895 {CC "put" #Type "Volatile", CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type##Volatile)}
896
897
898 static JNINativeMethod jdk_internal_misc_Unsafe_methods[] = {
899 {CC "getReference", CC "(" OBJ "J)" OBJ "", FN_PTR(Unsafe_GetReference)},
900 {CC "putReference", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReference)},
901 {CC "getReferenceVolatile", CC "(" OBJ "J)" OBJ, FN_PTR(Unsafe_GetReferenceVolatile)},
902 {CC "putReferenceVolatile", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReferenceVolatile)},
903
904 {CC "getUncompressedObject", CC "(" ADR ")" OBJ, FN_PTR(Unsafe_GetUncompressedObject)},
905
906 DECLARE_GETPUTOOP(Boolean, Z),
907 DECLARE_GETPUTOOP(Byte, B),
908 DECLARE_GETPUTOOP(Short, S),
909 DECLARE_GETPUTOOP(Char, C),
910 DECLARE_GETPUTOOP(Int, I),
911 DECLARE_GETPUTOOP(Long, J),
912 DECLARE_GETPUTOOP(Float, F),
913 DECLARE_GETPUTOOP(Double, D),
914
915 {CC "allocateMemory0", CC "(J)" ADR, FN_PTR(Unsafe_AllocateMemory0)},
916 {CC "reallocateMemory0", CC "(" ADR "J)" ADR, FN_PTR(Unsafe_ReallocateMemory0)},
917 {CC "freeMemory0", CC "(" ADR ")V", FN_PTR(Unsafe_FreeMemory0)},
918
919 {CC "objectFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_ObjectFieldOffset0)},
920 {CC "objectFieldOffset1", CC "(" CLS LANG "String;)J", FN_PTR(Unsafe_ObjectFieldOffset1)},
921 {CC "staticFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_StaticFieldOffset0)},
922 {CC "staticFieldBase0", CC "(" FLD ")" OBJ, FN_PTR(Unsafe_StaticFieldBase0)},
923 {CC "ensureClassInitialized0", CC "(" CLS ")V", FN_PTR(Unsafe_EnsureClassInitialized0)},
924 {CC "arrayBaseOffset0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayBaseOffset0)},
925 {CC "arrayIndexScale0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayIndexScale0)},
926
927 {CC "defineClass0", CC "(" DC_Args ")" CLS, FN_PTR(Unsafe_DefineClass0)},
928 {CC "allocateInstance", CC "(" CLS ")" OBJ, FN_PTR(Unsafe_AllocateInstance)},
929 {CC "throwException", CC "(" THR ")V", FN_PTR(Unsafe_ThrowException)},
930 {CC "compareAndSetReference",CC "(" OBJ "J" OBJ "" OBJ ")Z", FN_PTR(Unsafe_CompareAndSetReference)},
931 {CC "compareAndSetInt", CC "(" OBJ "J""I""I"")Z", FN_PTR(Unsafe_CompareAndSetInt)},
932 {CC "compareAndSetLong", CC "(" OBJ "J""J""J"")Z", FN_PTR(Unsafe_CompareAndSetLong)},
933 {CC "compareAndExchangeReference", CC "(" OBJ "J" OBJ "" OBJ ")" OBJ, FN_PTR(Unsafe_CompareAndExchangeReference)},
934 {CC "compareAndExchangeInt", CC "(" OBJ "J""I""I"")I", FN_PTR(Unsafe_CompareAndExchangeInt)},
935 {CC "compareAndExchangeLong", CC "(" OBJ "J""J""J"")J", FN_PTR(Unsafe_CompareAndExchangeLong)},
936
937 {CC "park", CC "(ZJ)V", FN_PTR(Unsafe_Park)},
938 {CC "unpark", CC "(" OBJ ")V", FN_PTR(Unsafe_Unpark)},
939
940 {CC "getLoadAverage0", CC "([DI)I", FN_PTR(Unsafe_GetLoadAverage0)},
941
942 {CC "copyMemory0", CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory0)},
943 {CC "copySwapMemory0", CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
944 {CC "writeback0", CC "(" "J" ")V", FN_PTR(Unsafe_WriteBack0)},
945 {CC "writebackPreSync0", CC "()V", FN_PTR(Unsafe_WriteBackPreSync0)},
946 {CC "writebackPostSync0", CC "()V", FN_PTR(Unsafe_WriteBackPostSync0)},
947 {CC "setMemory0", CC "(" OBJ "JJB)V", FN_PTR(Unsafe_SetMemory0)},
948
949 {CC "shouldBeInitialized0", CC "(" CLS ")Z", FN_PTR(Unsafe_ShouldBeInitialized0)},
950
951 {CC "loadFence", CC "()V", FN_PTR(Unsafe_LoadFence)},
952 {CC "storeFence", CC "()V", FN_PTR(Unsafe_StoreFence)},
953 {CC "fullFence", CC "()V", FN_PTR(Unsafe_FullFence)},
954 };
955
956 #undef CC
957 #undef FN_PTR
958
959 #undef ADR
960 #undef LANG
961 #undef OBJ
962 #undef CLS
963 #undef FLD
964 #undef THR
965 #undef DC_Args
966 #undef DAC_Args
967
968 #undef DECLARE_GETPUTOOP
969
970
971 // This function is exported, used by NativeLookup.
972 // The Unsafe_xxx functions above are called only from the interpreter.
973 // The optimizer looks at names and signatures to recognize
974 // individual functions.
975
976 JVM_ENTRY(void, JVM_RegisterJDKInternalMiscUnsafeMethods(JNIEnv *env, jclass unsafeclass)) {
977 ThreadToNativeFromVM ttnfv(thread);
978
979 int ok = env->RegisterNatives(unsafeclass, jdk_internal_misc_Unsafe_methods, sizeof(jdk_internal_misc_Unsafe_methods)/sizeof(JNINativeMethod));
980 guarantee(ok == 0, "register jdk.internal.misc.Unsafe natives");
981 } JVM_END