1 /*
2 * Copyright (c) 2000, 2025, 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 "classfile/classFileStream.hpp"
26 #include "classfile/classLoader.hpp"
27 #include "classfile/classLoadInfo.hpp"
28 #include "classfile/javaClasses.inline.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "classfile/vmSymbols.hpp"
31 #include "jfr/jfrEvents.hpp"
32 #include "jni.h"
33 #include "jvm.h"
34 #include "memory/allocation.inline.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "oops/access.inline.hpp"
37 #include "oops/fieldStreams.inline.hpp"
38 #include "oops/instanceKlass.inline.hpp"
39 #include "oops/klass.inline.hpp"
40 #include "oops/objArrayOop.inline.hpp"
41 #include "oops/oop.inline.hpp"
42 #include "oops/typeArrayOop.inline.hpp"
43 #include "prims/jvmtiExport.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/javaThread.inline.hpp"
49 #include "runtime/jniHandles.inline.hpp"
50 #include "runtime/orderAccess.hpp"
51 #include "runtime/reflection.hpp"
52 #include "runtime/sharedRuntime.hpp"
53 #include "runtime/stubRoutines.hpp"
54 #include "runtime/threadSMR.hpp"
55 #include "runtime/vm_version.hpp"
56 #include "runtime/vmOperations.hpp"
57 #include "sanitizers/ub.hpp"
58 #include "services/threadService.hpp"
59 #include "utilities/align.hpp"
60 #include "utilities/copy.hpp"
61 #include "utilities/dtrace.hpp"
62 #include "utilities/macros.hpp"
63
64 /**
65 * Implementation of the jdk.internal.misc.Unsafe class
66 */
67
68
69 #define MAX_OBJECT_SIZE \
70 ( arrayOopDesc::base_offset_in_bytes(T_DOUBLE) \
71 + ((julong)max_jint * sizeof(double)) )
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 int field_offset_from_byte_offset(int 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 != nullptr) {
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<void>((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 uintptr_t base_address = cast_from_oop<uintptr_t>(p);
134 uintptr_t byte_offset = (uintptr_t)field_offset_to_byte_offset(field_offset);
135 return (void*)(base_address + byte_offset);
136 }
137
138 // Externally callable versions:
139 // (Use these in compiler intrinsics which emulate unsafe primitives.)
140 jlong Unsafe_field_offset_to_byte_offset(jlong field_offset) {
141 return field_offset;
142 }
143 jlong Unsafe_field_offset_from_byte_offset(jlong byte_offset) {
144 return byte_offset;
145 }
146
147
148 ///// Data read/writes on the Java heap and in native (off-heap) memory
149
150 /**
151 * Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
152 */
153 class GuardUnsafeAccess {
154 JavaThread* _thread;
155
156 public:
157 GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
158 // native/off-heap access which may raise SIGBUS if accessing
159 // memory mapped file data in a region of the file which has
160 // been truncated and is now invalid.
161 _thread->set_doing_unsafe_access(true);
162 }
163
164 ~GuardUnsafeAccess() {
165 _thread->set_doing_unsafe_access(false);
166 }
167 };
168
169 /**
170 * Helper class for accessing memory.
171 *
172 * Normalizes values and wraps accesses in
173 * JavaThread::doing_unsafe_access() if needed.
174 */
175 template <typename T>
176 class MemoryAccess : StackObj {
177 JavaThread* _thread;
178 oop _obj;
179 ptrdiff_t _offset;
180
181 // Resolves and returns the address of the memory access.
182 // This raw memory access may fault, so we make sure it happens within the
183 // guarded scope by making the access volatile at least. Since the store
184 // of Thread::set_doing_unsafe_access() is also volatile, these accesses
185 // can not be reordered by the compiler. Therefore, if the access triggers
186 // a fault, we will know that Thread::doing_unsafe_access() returns true.
187 volatile T* addr() {
188 void* addr = index_oop_from_field_offset_long(_obj, _offset);
189 return static_cast<volatile T*>(addr);
190 }
191
192 template <typename U>
193 U normalize_for_write(U x) {
194 return x;
195 }
196
197 jboolean normalize_for_write(jboolean x) {
198 return x & 1;
199 }
200
201 template <typename U>
202 U normalize_for_read(U x) {
203 return x;
204 }
205
206 jboolean normalize_for_read(jboolean x) {
207 return x != 0;
208 }
209
210 public:
211 MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
212 : _thread(thread), _obj(JNIHandles::resolve(obj)), _offset((ptrdiff_t)offset) {
213 assert_field_offset_sane(_obj, offset);
214 }
215
216 T get() {
217 GuardUnsafeAccess guard(_thread);
218 return normalize_for_read(*addr());
219 }
220
221 // we use this method at some places for writing to 0 e.g. to cause a crash;
222 // ubsan does not know that this is the desired behavior
223 ATTRIBUTE_NO_UBSAN
224 void put(T x) {
225 GuardUnsafeAccess guard(_thread);
226 *addr() = normalize_for_write(x);
227 }
228
229
230 T get_volatile() {
231 GuardUnsafeAccess guard(_thread);
232 volatile T ret = RawAccess<MO_SEQ_CST>::load(addr());
233 return normalize_for_read(ret);
234 }
235
236 void put_volatile(T x) {
237 GuardUnsafeAccess guard(_thread);
238 RawAccess<MO_SEQ_CST>::store(addr(), normalize_for_write(x));
239 }
240 };
241
242 // These functions allow a null base pointer with an arbitrary address.
243 // But if the base pointer is non-null, the offset should make some sense.
244 // That is, it should be in the range [0, MAX_OBJECT_SIZE].
245 UNSAFE_ENTRY(jobject, Unsafe_GetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
246 oop p = JNIHandles::resolve(obj);
247 assert_field_offset_sane(p, offset);
248 oop v = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
249 return JNIHandles::make_local(THREAD, v);
250 } UNSAFE_END
251
252 UNSAFE_ENTRY(void, Unsafe_PutReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
253 oop x = JNIHandles::resolve(x_h);
254 oop p = JNIHandles::resolve(obj);
255 assert_field_offset_sane(p, offset);
256 HeapAccess<ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
257 } UNSAFE_END
258
259 UNSAFE_ENTRY(jobject, Unsafe_GetReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
260 oop p = JNIHandles::resolve(obj);
261 assert_field_offset_sane(p, offset);
262 oop v = HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
263 return JNIHandles::make_local(THREAD, v);
264 } UNSAFE_END
265
266 UNSAFE_ENTRY(void, Unsafe_PutReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
267 oop x = JNIHandles::resolve(x_h);
268 oop p = JNIHandles::resolve(obj);
269 assert_field_offset_sane(p, offset);
270 HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
271 } UNSAFE_END
272
273 UNSAFE_ENTRY(jobject, Unsafe_GetUncompressedObject(JNIEnv *env, jobject unsafe, jlong addr)) {
274 oop v = *(oop*) (address) addr;
275 return JNIHandles::make_local(THREAD, v);
276 } UNSAFE_END
277
278 #define DEFINE_GETSETOOP(java_type, Type) \
279 \
280 UNSAFE_ENTRY(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
281 return MemoryAccess<java_type>(thread, obj, offset).get(); \
282 } UNSAFE_END \
283 \
284 UNSAFE_ENTRY(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
285 MemoryAccess<java_type>(thread, obj, offset).put(x); \
286 } UNSAFE_END \
287 \
288 // END DEFINE_GETSETOOP.
289
290 DEFINE_GETSETOOP(jboolean, Boolean)
291 DEFINE_GETSETOOP(jbyte, Byte)
292 DEFINE_GETSETOOP(jshort, Short);
293 DEFINE_GETSETOOP(jchar, Char);
294 DEFINE_GETSETOOP(jint, Int);
295 DEFINE_GETSETOOP(jlong, Long);
296 DEFINE_GETSETOOP(jfloat, Float);
297 DEFINE_GETSETOOP(jdouble, Double);
298
299 #undef DEFINE_GETSETOOP
300
301 #define DEFINE_GETSETOOP_VOLATILE(java_type, Type) \
302 \
303 UNSAFE_ENTRY(java_type, Unsafe_Get##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
304 return MemoryAccess<java_type>(thread, obj, offset).get_volatile(); \
305 } UNSAFE_END \
306 \
307 UNSAFE_ENTRY(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
308 MemoryAccess<java_type>(thread, obj, offset).put_volatile(x); \
309 } UNSAFE_END \
310 \
311 // END DEFINE_GETSETOOP_VOLATILE.
312
313 DEFINE_GETSETOOP_VOLATILE(jboolean, Boolean)
314 DEFINE_GETSETOOP_VOLATILE(jbyte, Byte)
315 DEFINE_GETSETOOP_VOLATILE(jshort, Short);
316 DEFINE_GETSETOOP_VOLATILE(jchar, Char);
317 DEFINE_GETSETOOP_VOLATILE(jint, Int);
318 DEFINE_GETSETOOP_VOLATILE(jlong, Long);
319 DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
320 DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
321
322 #undef DEFINE_GETSETOOP_VOLATILE
323
324 UNSAFE_LEAF(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe)) {
325 OrderAccess::fence();
326 } UNSAFE_END
327
328 ////// Allocation requests
329
330 UNSAFE_ENTRY(jobject, Unsafe_AllocateInstance(JNIEnv *env, jobject unsafe, jclass cls)) {
331 JvmtiVMObjectAllocEventCollector oam;
332 instanceOop i = InstanceKlass::allocate_instance(JNIHandles::resolve_non_null(cls), CHECK_NULL);
333 return JNIHandles::make_local(THREAD, i);
334 } UNSAFE_END
335
336 UNSAFE_LEAF(jlong, Unsafe_AllocateMemory0(JNIEnv *env, jobject unsafe, jlong size)) {
337 size_t sz = (size_t)size;
338
339 assert(is_aligned(sz, HeapWordSize), "sz not aligned");
340
341 void* x = os::malloc(sz, mtOther);
342
343 return addr_to_java(x);
344 } UNSAFE_END
345
346 UNSAFE_LEAF(jlong, Unsafe_ReallocateMemory0(JNIEnv *env, jobject unsafe, jlong addr, jlong size)) {
347 void* p = addr_from_java(addr);
348 size_t sz = (size_t)size;
349
350 assert(is_aligned(sz, HeapWordSize), "sz not aligned");
351
352 void* x = os::realloc(p, sz, mtOther);
353
354 return addr_to_java(x);
355 } UNSAFE_END
356
357 UNSAFE_LEAF(void, Unsafe_FreeMemory0(JNIEnv *env, jobject unsafe, jlong addr)) {
358 void* p = addr_from_java(addr);
359
360 os::free(p);
361 } UNSAFE_END
362
363 UNSAFE_ENTRY(void, Unsafe_SetMemory0(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong size, jbyte value)) {
364 size_t sz = (size_t)size;
365
366 oop base = JNIHandles::resolve(obj);
367 void* p = index_oop_from_field_offset_long(base, offset);
368
369 {
370 GuardUnsafeAccess guard(thread);
371 if (StubRoutines::unsafe_setmemory() != nullptr) {
372 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
373 StubRoutines::UnsafeSetMemory_stub()(p, sz, value);
374 } else {
375 Copy::fill_to_memory_atomic(p, sz, value);
376 }
377 }
378 } UNSAFE_END
379
380 UNSAFE_ENTRY(void, Unsafe_CopyMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size)) {
381 size_t sz = (size_t)size;
382
383 oop srcp = JNIHandles::resolve(srcObj);
384 oop dstp = JNIHandles::resolve(dstObj);
385
386 void* src = index_oop_from_field_offset_long(srcp, srcOffset);
387 void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
388 {
389 GuardUnsafeAccess guard(thread);
390 if (StubRoutines::unsafe_arraycopy() != nullptr) {
391 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
392 StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
393 } else {
394 Copy::conjoint_memory_atomic(src, dst, sz);
395 }
396 }
397 } UNSAFE_END
398
399 // This function is a leaf since if the source and destination are both in native memory
400 // the copy may potentially be very large, and we don't want to disable GC if we can avoid it.
401 // If either source or destination (or both) are on the heap, the function will enter VM using
402 // JVM_ENTRY_FROM_LEAF
403 UNSAFE_LEAF(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
404 size_t sz = (size_t)size;
405 size_t esz = (size_t)elemSize;
406
407
408 if (srcObj == nullptr && dstObj == nullptr) {
409 // Both src & dst are in native memory
410 address src = (address)srcOffset;
411 address dst = (address)dstOffset;
412
413 {
414 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
415 GuardUnsafeAccess guard(thread);
416 Copy::conjoint_swap(src, dst, sz, esz);
417 }
418 } else {
419 // At least one of src/dst are on heap, transition to VM to access raw pointers
420
421 JVM_ENTRY_FROM_LEAF(env, void, Unsafe_CopySwapMemory0) {
422 oop srcp = JNIHandles::resolve(srcObj);
423 oop dstp = JNIHandles::resolve(dstObj);
424
425 address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
426 address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
427 {
428 GuardUnsafeAccess guard(thread);
429 Copy::conjoint_swap(src, dst, sz, esz);
430 }
431 } JVM_END
432 }
433 } UNSAFE_END
434
435 UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
436 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
437 #ifdef ASSERT
438 if (TraceMemoryWriteback) {
439 tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
440 }
441 #endif
442
443 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
444 assert(StubRoutines::data_cache_writeback() != nullptr, "sanity");
445 (StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
446 } UNSAFE_END
447
448 static void doWriteBackSync0(bool is_pre)
449 {
450 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
451 assert(StubRoutines::data_cache_writeback_sync() != nullptr, "sanity");
452 (StubRoutines::DataCacheWritebackSync_stub())(is_pre);
453 }
454
455 UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
456 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
457 #ifdef ASSERT
458 if (TraceMemoryWriteback) {
459 tty->print_cr("Unsafe: writeback pre-sync");
460 }
461 #endif
462
463 doWriteBackSync0(true);
464 } UNSAFE_END
465
466 UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
467 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
468 #ifdef ASSERT
469 if (TraceMemoryWriteback) {
470 tty->print_cr("Unsafe: writeback pre-sync");
471 }
472 #endif
473
474 doWriteBackSync0(false);
475 } UNSAFE_END
476
477 ////// Random queries
478
479 // Finds the object field offset of a field with the matching name, or an error code
480 // Error code -1 is not found, -2 is static field
481 static jlong find_known_instance_field_offset(jclass clazz, jstring name, TRAPS) {
482 assert(clazz != nullptr, "clazz must not be null");
483 assert(name != nullptr, "name must not be null");
484
485 ResourceMark rm(THREAD);
486 char *utf_name = java_lang_String::as_utf8_string(JNIHandles::resolve_non_null(name));
487
488 InstanceKlass* k = java_lang_Class::as_InstanceKlass(JNIHandles::resolve_non_null(clazz));
489
490 jint offset = -1; // Not found
491 for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
492 Symbol *name = fs.name();
493 if (name->equals(utf_name)) {
494 if (!fs.access_flags().is_static()) {
495 offset = fs.offset();
496 } else {
497 offset = -2; // A static field
498 }
499 break;
500 }
501 }
502 if (offset < 0) {
503 return offset; // Error code
504 }
505 return field_offset_from_byte_offset(offset);
506 }
507
508 static jlong find_field_offset(jobject field, int must_be_static, TRAPS) {
509 assert(field != nullptr, "field must not be null");
510
511 oop reflected = JNIHandles::resolve_non_null(field);
512 oop mirror = java_lang_reflect_Field::clazz(reflected);
513 Klass* k = java_lang_Class::as_Klass(mirror);
514 int slot = java_lang_reflect_Field::slot(reflected);
515 int modifiers = java_lang_reflect_Field::modifiers(reflected);
516
517 if (must_be_static >= 0) {
518 int really_is_static = ((modifiers & JVM_ACC_STATIC) != 0);
519 if (must_be_static != really_is_static) {
520 THROW_0(vmSymbols::java_lang_IllegalArgumentException());
521 }
522 }
523
524 int offset = InstanceKlass::cast(k)->field_offset(slot);
525 return field_offset_from_byte_offset(offset);
526 }
527
528 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
529 return find_field_offset(field, 0, THREAD);
530 } UNSAFE_END
531
532 UNSAFE_ENTRY(jlong, Unsafe_KnownObjectFieldOffset0(JNIEnv *env, jobject unsafe, jclass c, jstring name)) {
533 return find_known_instance_field_offset(c, name, THREAD);
534 } UNSAFE_END
535
536 UNSAFE_ENTRY(jlong, Unsafe_StaticFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
537 return find_field_offset(field, 1, THREAD);
538 } UNSAFE_END
539
540 UNSAFE_ENTRY(jobject, Unsafe_StaticFieldBase0(JNIEnv *env, jobject unsafe, jobject field)) {
541 assert(field != nullptr, "field must not be null");
542
543 // Note: In this VM implementation, a field address is always a short
544 // offset from the base of a klass metaobject. Thus, the full dynamic
545 // range of the return type is never used. However, some implementations
546 // might put the static field inside an array shared by many classes,
547 // or even at a fixed address, in which case the address could be quite
548 // large. In that last case, this function would return null, since
549 // the address would operate alone, without any base pointer.
550
551 oop reflected = JNIHandles::resolve_non_null(field);
552 oop mirror = java_lang_reflect_Field::clazz(reflected);
553 int modifiers = java_lang_reflect_Field::modifiers(reflected);
554
555 if ((modifiers & JVM_ACC_STATIC) == 0) {
556 THROW_NULL(vmSymbols::java_lang_IllegalArgumentException());
557 }
558
559 return JNIHandles::make_local(THREAD, mirror);
560 } UNSAFE_END
561
562 UNSAFE_ENTRY(void, Unsafe_EnsureClassInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
563 assert(clazz != nullptr, "clazz must not be null");
564
565 oop mirror = JNIHandles::resolve_non_null(clazz);
566
567 Klass* klass = java_lang_Class::as_Klass(mirror);
568 if (klass != nullptr && klass->should_be_initialized()) {
569 InstanceKlass* k = InstanceKlass::cast(klass);
570 k->initialize(CHECK);
571 }
572 }
573 UNSAFE_END
574
575 UNSAFE_ENTRY(jboolean, Unsafe_ShouldBeInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
576 assert(clazz != nullptr, "clazz must not be null");
577
578 oop mirror = JNIHandles::resolve_non_null(clazz);
579 Klass* klass = java_lang_Class::as_Klass(mirror);
580
581 if (klass != nullptr && klass->should_be_initialized()) {
582 return true;
583 }
584
585 return false;
586 }
587 UNSAFE_END
588
589 static void getBaseAndScale(int& base, int& scale, jclass clazz, TRAPS) {
590 assert(clazz != nullptr, "clazz must not be null");
591
592 oop mirror = JNIHandles::resolve_non_null(clazz);
593 Klass* k = java_lang_Class::as_Klass(mirror);
594
595 if (k == nullptr || !k->is_array_klass()) {
596 THROW(vmSymbols::java_lang_InvalidClassException());
597 } else if (k->is_objArray_klass()) {
598 base = arrayOopDesc::base_offset_in_bytes(T_OBJECT);
599 scale = heapOopSize;
600 } else if (k->is_typeArray_klass()) {
601 TypeArrayKlass* tak = TypeArrayKlass::cast(k);
602 base = tak->array_header_in_bytes();
603 assert(base == arrayOopDesc::base_offset_in_bytes(tak->element_type()), "array_header_size semantics ok");
604 scale = (1 << tak->log2_element_size());
605 } else {
606 ShouldNotReachHere();
607 }
608 }
609
610 UNSAFE_ENTRY(jint, Unsafe_ArrayBaseOffset0(JNIEnv *env, jobject unsafe, jclass clazz)) {
611 int base = 0, scale = 0;
612 getBaseAndScale(base, scale, clazz, CHECK_0);
613
614 return field_offset_from_byte_offset(base);
615 } UNSAFE_END
616
617
618 UNSAFE_ENTRY(jint, Unsafe_ArrayIndexScale0(JNIEnv *env, jobject unsafe, jclass clazz)) {
619 int base = 0, scale = 0;
620 getBaseAndScale(base, scale, clazz, CHECK_0);
621
622 // This VM packs both fields and array elements down to the byte.
623 // But watch out: If this changes, so that array references for
624 // a given primitive type (say, T_BOOLEAN) use different memory units
625 // than fields, this method MUST return zero for such arrays.
626 // For example, the VM used to store sub-word sized fields in full
627 // words in the object layout, so that accessors like getByte(Object,int)
628 // did not really do what one might expect for arrays. Therefore,
629 // this function used to report a zero scale factor, so that the user
630 // would know not to attempt to access sub-word array elements.
631 // // Code for unpacked fields:
632 // if (scale < wordSize) return 0;
633
634 // The following allows for a pretty general fieldOffset cookie scheme,
635 // but requires it to be linear in byte offset.
636 return field_offset_from_byte_offset(scale) - field_offset_from_byte_offset(0);
637 } UNSAFE_END
638
639
640 static inline void throw_new(JNIEnv *env, const char *ename) {
641 jclass cls = env->FindClass(ename);
642 if (env->ExceptionCheck()) {
643 env->ExceptionClear();
644 tty->print_cr("Unsafe: cannot throw %s because FindClass has failed", ename);
645 return;
646 }
647
648 env->ThrowNew(cls, nullptr);
649 }
650
651 static jclass Unsafe_DefineClass_impl(JNIEnv *env, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd) {
652 // Code lifted from JDK 1.3 ClassLoader.c
653
654 jbyte *body;
655 char *utfName = nullptr;
656 jclass result = nullptr;
657 char buf[128];
658
659 assert(data != nullptr, "Class bytes must not be null");
660 assert(length >= 0, "length must not be negative: %d", length);
661
662 if (UsePerfData) {
663 ClassLoader::unsafe_defineClassCallCounter()->inc();
664 }
665
666 body = NEW_C_HEAP_ARRAY_RETURN_NULL(jbyte, length, mtInternal);
667 if (body == nullptr) {
668 throw_new(env, "java/lang/OutOfMemoryError");
669 return nullptr;
670 }
671
672 env->GetByteArrayRegion(data, offset, length, body);
673 if (env->ExceptionCheck()) {
674 goto free_body;
675 }
676
677 if (name != nullptr) {
678 uint len = env->GetStringUTFLength(name);
679 int unicode_len = env->GetStringLength(name);
680
681 if (len >= sizeof(buf)) {
682 utfName = NEW_C_HEAP_ARRAY_RETURN_NULL(char, len + 1, mtInternal);
683 if (utfName == nullptr) {
684 throw_new(env, "java/lang/OutOfMemoryError");
685 goto free_body;
686 }
687 } else {
688 utfName = buf;
689 }
690
691 env->GetStringUTFRegion(name, 0, unicode_len, utfName);
692
693 for (uint i = 0; i < len; i++) {
694 if (utfName[i] == '.') utfName[i] = '/';
695 }
696 }
697
698 result = JVM_DefineClass(env, utfName, loader, body, length, pd);
699
700 if (utfName && utfName != buf) {
701 FREE_C_HEAP_ARRAY(utfName);
702 }
703
704 free_body:
705 FREE_C_HEAP_ARRAY(body);
706 return result;
707 }
708
709
710 UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd)) {
711 ThreadToNativeFromVM ttnfv(thread);
712
713 return Unsafe_DefineClass_impl(env, name, data, offset, length, loader, pd);
714 } UNSAFE_END
715
716
717 UNSAFE_ENTRY(void, Unsafe_ThrowException(JNIEnv *env, jobject unsafe, jthrowable thr)) {
718 ThreadToNativeFromVM ttnfv(thread);
719 env->Throw(thr);
720 } UNSAFE_END
721
722 // JSR166 ------------------------------------------------------------------
723
724 UNSAFE_ENTRY(jobject, Unsafe_CompareAndExchangeReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
725 oop x = JNIHandles::resolve(x_h);
726 oop e = JNIHandles::resolve(e_h);
727 oop p = JNIHandles::resolve(obj);
728 assert_field_offset_sane(p, offset);
729 oop res = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
730 return JNIHandles::make_local(THREAD, res);
731 } UNSAFE_END
732
733 UNSAFE_ENTRY(jint, Unsafe_CompareAndExchangeInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
734 oop p = JNIHandles::resolve(obj);
735 volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
736 return AtomicAccess::cmpxchg(addr, e, x);
737 } UNSAFE_END
738
739 UNSAFE_ENTRY(jlong, Unsafe_CompareAndExchangeLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
740 oop p = JNIHandles::resolve(obj);
741 volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
742 return AtomicAccess::cmpxchg(addr, e, x);
743 } UNSAFE_END
744
745 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
746 oop x = JNIHandles::resolve(x_h);
747 oop e = JNIHandles::resolve(e_h);
748 oop p = JNIHandles::resolve(obj);
749 assert_field_offset_sane(p, offset);
750 oop ret = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
751 return ret == e;
752 } UNSAFE_END
753
754 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
755 oop p = JNIHandles::resolve(obj);
756 volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
757 return AtomicAccess::cmpxchg(addr, e, x) == e;
758 } UNSAFE_END
759
760 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
761 oop p = JNIHandles::resolve(obj);
762 volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
763 return AtomicAccess::cmpxchg(addr, e, x) == e;
764 } UNSAFE_END
765
766 static void post_thread_park_event(EventThreadPark* event, const oop obj, jlong timeout_nanos, jlong until_epoch_millis) {
767 assert(event != nullptr, "invariant");
768 event->set_parkedClass((obj != nullptr) ? obj->klass() : nullptr);
769 event->set_timeout(timeout_nanos);
770 event->set_until(until_epoch_millis);
771 event->set_address((obj != nullptr) ? (u8)cast_from_oop<uintptr_t>(obj) : 0);
772 event->commit();
773 }
774
775 UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time)) {
776 HOTSPOT_THREAD_PARK_BEGIN((uintptr_t) thread->parker(), (int) isAbsolute, time);
777 EventThreadPark event;
778
779 JavaThreadParkedState jtps(thread, time != 0);
780 thread->parker()->park(isAbsolute != 0, time);
781 if (event.should_commit()) {
782 const oop obj = thread->current_park_blocker();
783 if (time == 0) {
784 post_thread_park_event(&event, obj, min_jlong, min_jlong);
785 } else {
786 if (isAbsolute != 0) {
787 post_thread_park_event(&event, obj, min_jlong, time);
788 } else {
789 post_thread_park_event(&event, obj, time, min_jlong);
790 }
791 }
792 }
793 HOTSPOT_THREAD_PARK_END((uintptr_t) thread->parker());
794 } UNSAFE_END
795
796 UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread)) {
797 if (jthread != nullptr) {
798 oop thread_oop = JNIHandles::resolve_non_null(jthread);
799 // Get the JavaThread* stored in the java.lang.Thread object _before_
800 // the embedded ThreadsListHandle is constructed so we know if the
801 // early life stage of the JavaThread* is protected. We use acquire
802 // here to ensure that if we see a non-nullptr value, then we also
803 // see the main ThreadsList updates from the JavaThread* being added.
804 FastThreadsListHandle ftlh(thread_oop, java_lang_Thread::thread_acquire(thread_oop));
805 JavaThread* thr = ftlh.protected_java_thread();
806 if (thr != nullptr) {
807 // The still live JavaThread* is protected by the FastThreadsListHandle
808 // so it is safe to access.
809 Parker* p = thr->parker();
810 HOTSPOT_THREAD_UNPARK((uintptr_t) p);
811 p->unpark();
812 }
813 } // FastThreadsListHandle is destroyed here.
814 } UNSAFE_END
815
816 UNSAFE_ENTRY(jint, Unsafe_GetLoadAverage0(JNIEnv *env, jobject unsafe, jdoubleArray loadavg, jint nelem)) {
817 const int max_nelem = 3;
818 double la[max_nelem];
819 jint ret;
820
821 typeArrayOop a = typeArrayOop(JNIHandles::resolve_non_null(loadavg));
822 assert(a->is_typeArray(), "must be type array");
823
824 ret = os::loadavg(la, nelem);
825 if (ret == -1) {
826 return -1;
827 }
828
829 // if successful, ret is the number of samples actually retrieved.
830 assert(ret >= 0 && ret <= max_nelem, "Unexpected loadavg return value");
831 switch(ret) {
832 case 3: a->double_at_put(2, (jdouble)la[2]); // fall through
833 case 2: a->double_at_put(1, (jdouble)la[1]); // fall through
834 case 1: a->double_at_put(0, (jdouble)la[0]); break;
835 }
836
837 return ret;
838 } UNSAFE_END
839
840
841 /// JVM_RegisterUnsafeMethods
842
843 #define ADR "J"
844
845 #define LANG "Ljava/lang/"
846
847 #define OBJ LANG "Object;"
848 #define CLS LANG "Class;"
849 #define FLD LANG "reflect/Field;"
850 #define THR LANG "Throwable;"
851
852 #define DC_Args LANG "String;[BII" LANG "ClassLoader;" "Ljava/security/ProtectionDomain;"
853 #define DAC_Args CLS "[B[" OBJ
854
855 #define CC (char*) /*cast a literal from (const char*)*/
856 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
857
858 #define DECLARE_GETPUTOOP(Type, Desc) \
859 {CC "get" #Type, CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type)}, \
860 {CC "put" #Type, CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type)}, \
861 {CC "get" #Type "Volatile", CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type##Volatile)}, \
862 {CC "put" #Type "Volatile", CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type##Volatile)}
863
864
865 static JNINativeMethod jdk_internal_misc_Unsafe_methods[] = {
866 {CC "getReference", CC "(" OBJ "J)" OBJ "", FN_PTR(Unsafe_GetReference)},
867 {CC "putReference", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReference)},
868 {CC "getReferenceVolatile", CC "(" OBJ "J)" OBJ, FN_PTR(Unsafe_GetReferenceVolatile)},
869 {CC "putReferenceVolatile", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReferenceVolatile)},
870
871 {CC "getUncompressedObject", CC "(" ADR ")" OBJ, FN_PTR(Unsafe_GetUncompressedObject)},
872
873 DECLARE_GETPUTOOP(Boolean, Z),
874 DECLARE_GETPUTOOP(Byte, B),
875 DECLARE_GETPUTOOP(Short, S),
876 DECLARE_GETPUTOOP(Char, C),
877 DECLARE_GETPUTOOP(Int, I),
878 DECLARE_GETPUTOOP(Long, J),
879 DECLARE_GETPUTOOP(Float, F),
880 DECLARE_GETPUTOOP(Double, D),
881
882 {CC "allocateMemory0", CC "(J)" ADR, FN_PTR(Unsafe_AllocateMemory0)},
883 {CC "reallocateMemory0", CC "(" ADR "J)" ADR, FN_PTR(Unsafe_ReallocateMemory0)},
884 {CC "freeMemory0", CC "(" ADR ")V", FN_PTR(Unsafe_FreeMemory0)},
885
886 {CC "objectFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_ObjectFieldOffset0)},
887 {CC "knownObjectFieldOffset0", CC "(" CLS LANG "String;)J", FN_PTR(Unsafe_KnownObjectFieldOffset0)},
888 {CC "staticFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_StaticFieldOffset0)},
889 {CC "staticFieldBase0", CC "(" FLD ")" OBJ, FN_PTR(Unsafe_StaticFieldBase0)},
890 {CC "ensureClassInitialized0", CC "(" CLS ")V", FN_PTR(Unsafe_EnsureClassInitialized0)},
891 {CC "arrayBaseOffset0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayBaseOffset0)},
892 {CC "arrayIndexScale0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayIndexScale0)},
893
894 {CC "defineClass0", CC "(" DC_Args ")" CLS, FN_PTR(Unsafe_DefineClass0)},
895 {CC "allocateInstance", CC "(" CLS ")" OBJ, FN_PTR(Unsafe_AllocateInstance)},
896 {CC "throwException", CC "(" THR ")V", FN_PTR(Unsafe_ThrowException)},
897 {CC "compareAndSetReference",CC "(" OBJ "J" OBJ "" OBJ ")Z", FN_PTR(Unsafe_CompareAndSetReference)},
898 {CC "compareAndSetInt", CC "(" OBJ "J""I""I"")Z", FN_PTR(Unsafe_CompareAndSetInt)},
899 {CC "compareAndSetLong", CC "(" OBJ "J""J""J"")Z", FN_PTR(Unsafe_CompareAndSetLong)},
900 {CC "compareAndExchangeReference", CC "(" OBJ "J" OBJ "" OBJ ")" OBJ, FN_PTR(Unsafe_CompareAndExchangeReference)},
901 {CC "compareAndExchangeInt", CC "(" OBJ "J""I""I"")I", FN_PTR(Unsafe_CompareAndExchangeInt)},
902 {CC "compareAndExchangeLong", CC "(" OBJ "J""J""J"")J", FN_PTR(Unsafe_CompareAndExchangeLong)},
903
904 {CC "park", CC "(ZJ)V", FN_PTR(Unsafe_Park)},
905 {CC "unpark", CC "(" OBJ ")V", FN_PTR(Unsafe_Unpark)},
906
907 {CC "getLoadAverage0", CC "([DI)I", FN_PTR(Unsafe_GetLoadAverage0)},
908
909 {CC "copyMemory0", CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory0)},
910 {CC "copySwapMemory0", CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
911 {CC "writeback0", CC "(" "J" ")V", FN_PTR(Unsafe_WriteBack0)},
912 {CC "writebackPreSync0", CC "()V", FN_PTR(Unsafe_WriteBackPreSync0)},
913 {CC "writebackPostSync0", CC "()V", FN_PTR(Unsafe_WriteBackPostSync0)},
914 {CC "setMemory0", CC "(" OBJ "JJB)V", FN_PTR(Unsafe_SetMemory0)},
915
916 {CC "shouldBeInitialized0", CC "(" CLS ")Z", FN_PTR(Unsafe_ShouldBeInitialized0)},
917
918 {CC "fullFence", CC "()V", FN_PTR(Unsafe_FullFence)},
919 };
920
921 #undef CC
922 #undef FN_PTR
923
924 #undef ADR
925 #undef LANG
926 #undef OBJ
927 #undef CLS
928 #undef FLD
929 #undef THR
930 #undef DC_Args
931 #undef DAC_Args
932
933 #undef DECLARE_GETPUTOOP
934
935
936 // This function is exported, used by NativeLookup.
937 // The Unsafe_xxx functions above are called only from the interpreter.
938 // The optimizer looks at names and signatures to recognize
939 // individual functions.
940
941 JVM_ENTRY(void, JVM_RegisterJDKInternalMiscUnsafeMethods(JNIEnv *env, jclass unsafeclass)) {
942 ThreadToNativeFromVM ttnfv(thread);
943
944 int ok = env->RegisterNatives(unsafeclass, jdk_internal_misc_Unsafe_methods, sizeof(jdk_internal_misc_Unsafe_methods)/sizeof(JNINativeMethod));
945 guarantee(ok == 0, "register jdk.internal.misc.Unsafe natives");
946 } JVM_END