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