1 /*
2 * Copyright (c) 2000, 2024, 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 "classfile/classFileStream.hpp"
27 #include "classfile/classLoader.hpp"
28 #include "classfile/classLoadInfo.hpp"
29 #include "classfile/javaClasses.inline.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "classfile/vmSymbols.hpp"
32 #include "jfr/jfrEvents.hpp"
33 #include "jni.h"
34 #include "jvm.h"
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/jvmtiExport.hpp"
45 #include "prims/unsafe.hpp"
46 #include "runtime/globals.hpp"
47 #include "runtime/handles.inline.hpp"
48 #include "runtime/interfaceSupport.inline.hpp"
49 #include "runtime/javaThread.inline.hpp"
50 #include "runtime/jniHandles.inline.hpp"
51 #include "runtime/orderAccess.hpp"
52 #include "runtime/reflection.hpp"
53 #include "runtime/sharedRuntime.hpp"
54 #include "runtime/stubRoutines.hpp"
55 #include "runtime/threadSMR.hpp"
56 #include "runtime/vmOperations.hpp"
57 #include "runtime/vm_version.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 // All memory access methods (e.g. getInt, copyMemory) must use this macro.
80 // We call these methods "scoped" methods, as access to these methods is
81 // typically governed by a "scope" (a MemorySessionImpl object), and no
82 // access is allowed when the scope is no longer alive.
83 //
84 // Closing a scope object (cf. scopedMemoryAccess.cpp) can install
85 // an async exception during a safepoint. When that happens,
86 // scoped methods are not allowed to touch the underlying memory (as that
87 // memory might have been released). Therefore, when entering a scoped method
88 // we check if an async exception has been installed, and return immediately
89 // if that is the case.
90 //
91 // As a rule, we disallow safepoints in the middle of a scoped method.
92 // If an async exception handshake were installed in such a safepoint,
93 // memory access might still occur before the handshake is honored by
94 // the accessing thread.
95 //
96 // Corollary: as threads in native state are considered to be at a safepoint,
97 // scoped methods must NOT be executed while in the native thread state.
98 // Because of this, there can be no UNSAFE_LEAF_SCOPED.
99 #define UNSAFE_ENTRY_SCOPED(result_type, header) \
100 JVM_ENTRY(static result_type, header) \
101 if (thread->has_async_exception_condition()) {return (result_type)0;}
102
103 #define UNSAFE_END JVM_END
104
105
106 static inline void* addr_from_java(jlong addr) {
107 // This assert fails in a variety of ways on 32-bit systems.
108 // It is impossible to predict whether native code that converts
109 // pointers to longs will sign-extend or zero-extend the addresses.
110 //assert(addr == (uintptr_t)addr, "must not be odd high bits");
111 return (void*)(uintptr_t)addr;
112 }
113
114 static inline jlong addr_to_java(void* p) {
115 assert(p == (void*)(uintptr_t)p, "must not be odd high bits");
116 return (uintptr_t)p;
117 }
118
119
120 // Note: The VM's obj_field and related accessors use byte-scaled
121 // ("unscaled") offsets, just as the unsafe methods do.
122
123 // However, the method Unsafe.fieldOffset explicitly declines to
124 // guarantee this. The field offset values manipulated by the Java user
125 // through the Unsafe API are opaque cookies that just happen to be byte
126 // offsets. We represent this state of affairs by passing the cookies
127 // through conversion functions when going between the VM and the Unsafe API.
128 // The conversion functions just happen to be no-ops at present.
129
130 static inline jlong field_offset_to_byte_offset(jlong field_offset) {
131 return field_offset;
132 }
133
134 static inline int field_offset_from_byte_offset(int byte_offset) {
135 return byte_offset;
136 }
137
138 static inline void assert_field_offset_sane(oop p, jlong field_offset) {
139 #ifdef ASSERT
140 jlong byte_offset = field_offset_to_byte_offset(field_offset);
141
142 if (p != nullptr) {
143 assert(byte_offset >= 0 && byte_offset <= (jlong)MAX_OBJECT_SIZE, "sane offset");
144 if (byte_offset == (jint)byte_offset) {
145 void* ptr_plus_disp = cast_from_oop<address>(p) + byte_offset;
146 assert(p->field_addr<void>((jint)byte_offset) == ptr_plus_disp,
147 "raw [ptr+disp] must be consistent with oop::field_addr");
148 }
149 jlong p_size = HeapWordSize * (jlong)(p->size());
150 assert(byte_offset < p_size, "Unsafe access: offset " INT64_FORMAT " > object's size " INT64_FORMAT, (int64_t)byte_offset, (int64_t)p_size);
151 }
152 #endif
153 }
154
155 static inline void* index_oop_from_field_offset_long(oop p, jlong field_offset) {
156 assert_field_offset_sane(p, field_offset);
157 uintptr_t base_address = cast_from_oop<uintptr_t>(p);
158 uintptr_t byte_offset = (uintptr_t)field_offset_to_byte_offset(field_offset);
159 return (void*)(base_address + byte_offset);
160 }
161
162 // Externally callable versions:
163 // (Use these in compiler intrinsics which emulate unsafe primitives.)
164 jlong Unsafe_field_offset_to_byte_offset(jlong field_offset) {
165 return field_offset;
166 }
167 jlong Unsafe_field_offset_from_byte_offset(jlong byte_offset) {
168 return byte_offset;
169 }
170
171
172 ///// Data read/writes on the Java heap and in native (off-heap) memory
173
174 /**
175 * Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
176 */
177 class GuardUnsafeAccess {
178 JavaThread* _thread;
179
180 public:
181 GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
182 // native/off-heap access which may raise SIGBUS if accessing
183 // memory mapped file data in a region of the file which has
184 // been truncated and is now invalid.
185 _thread->set_doing_unsafe_access(true);
186 }
187
188 ~GuardUnsafeAccess() {
189 _thread->set_doing_unsafe_access(false);
190 }
191 };
192
193 /**
194 * Helper class for accessing memory.
195 *
196 * Normalizes values and wraps accesses in
197 * JavaThread::doing_unsafe_access() if needed.
198 */
199 template <typename T>
200 class MemoryAccess : StackObj {
201 JavaThread* _thread;
202 oop _obj;
203 ptrdiff_t _offset;
204
205 // Resolves and returns the address of the memory access.
206 // This raw memory access may fault, so we make sure it happens within the
207 // guarded scope by making the access volatile at least. Since the store
208 // of Thread::set_doing_unsafe_access() is also volatile, these accesses
209 // can not be reordered by the compiler. Therefore, if the access triggers
210 // a fault, we will know that Thread::doing_unsafe_access() returns true.
211 volatile T* addr() {
212 void* addr = index_oop_from_field_offset_long(_obj, _offset);
213 return static_cast<volatile T*>(addr);
214 }
215
216 template <typename U>
217 U normalize_for_write(U x) {
218 return x;
219 }
220
221 jboolean normalize_for_write(jboolean x) {
222 return x & 1;
223 }
224
225 template <typename U>
226 U normalize_for_read(U x) {
227 return x;
228 }
229
230 jboolean normalize_for_read(jboolean x) {
231 return x != 0;
232 }
233
234 public:
235 MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
236 : _thread(thread), _obj(JNIHandles::resolve(obj)), _offset((ptrdiff_t)offset) {
237 assert_field_offset_sane(_obj, offset);
238 }
239
240 T get() {
241 GuardUnsafeAccess guard(_thread);
242 return normalize_for_read(*addr());
243 }
244
245 void put(T x) {
246 GuardUnsafeAccess guard(_thread);
247 *addr() = normalize_for_write(x);
248 }
249
250
251 T get_volatile() {
252 GuardUnsafeAccess guard(_thread);
253 volatile T ret = RawAccess<MO_SEQ_CST>::load(addr());
254 return normalize_for_read(ret);
255 }
256
257 void put_volatile(T x) {
258 GuardUnsafeAccess guard(_thread);
259 RawAccess<MO_SEQ_CST>::store(addr(), normalize_for_write(x));
260 }
261 };
262
263 // These functions allow a null base pointer with an arbitrary address.
264 // But if the base pointer is non-null, the offset should make some sense.
265 // That is, it should be in the range [0, MAX_OBJECT_SIZE].
266 UNSAFE_ENTRY(jobject, Unsafe_GetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
267 oop p = JNIHandles::resolve(obj);
268 assert_field_offset_sane(p, offset);
269 oop v = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
270 return JNIHandles::make_local(THREAD, v);
271 } UNSAFE_END
272
273 UNSAFE_ENTRY(void, Unsafe_PutReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
274 oop x = JNIHandles::resolve(x_h);
275 oop p = JNIHandles::resolve(obj);
276 assert_field_offset_sane(p, offset);
277 HeapAccess<ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
278 } UNSAFE_END
279
280 UNSAFE_ENTRY(jobject, Unsafe_GetReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
281 oop p = JNIHandles::resolve(obj);
282 assert_field_offset_sane(p, offset);
283 oop v = HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
284 return JNIHandles::make_local(THREAD, v);
285 } UNSAFE_END
286
287 UNSAFE_ENTRY(void, Unsafe_PutReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
288 oop x = JNIHandles::resolve(x_h);
289 oop p = JNIHandles::resolve(obj);
290 assert_field_offset_sane(p, offset);
291 HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
292 } UNSAFE_END
293
294 UNSAFE_ENTRY(jobject, Unsafe_GetUncompressedObject(JNIEnv *env, jobject unsafe, jlong addr)) {
295 oop v = *(oop*) (address) addr;
296 return JNIHandles::make_local(THREAD, v);
297 } UNSAFE_END
298
299 #define DEFINE_GETSETOOP(java_type, Type) \
300 \
301 UNSAFE_ENTRY_SCOPED(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
302 return MemoryAccess<java_type>(thread, obj, offset).get(); \
303 } UNSAFE_END \
304 \
305 UNSAFE_ENTRY_SCOPED(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
306 MemoryAccess<java_type>(thread, obj, offset).put(x); \
307 } UNSAFE_END \
308 \
309 // END DEFINE_GETSETOOP.
310
311 DEFINE_GETSETOOP(jboolean, Boolean)
312 DEFINE_GETSETOOP(jbyte, Byte)
313 DEFINE_GETSETOOP(jshort, Short);
314 DEFINE_GETSETOOP(jchar, Char);
315 DEFINE_GETSETOOP(jint, Int);
316 DEFINE_GETSETOOP(jlong, Long);
317 DEFINE_GETSETOOP(jfloat, Float);
318 DEFINE_GETSETOOP(jdouble, Double);
319
320 #undef DEFINE_GETSETOOP
321
322 #define DEFINE_GETSETOOP_VOLATILE(java_type, Type) \
323 \
324 UNSAFE_ENTRY_SCOPED(java_type, Unsafe_Get##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
325 return MemoryAccess<java_type>(thread, obj, offset).get_volatile(); \
326 } UNSAFE_END \
327 \
328 UNSAFE_ENTRY_SCOPED(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
329 MemoryAccess<java_type>(thread, obj, offset).put_volatile(x); \
330 } UNSAFE_END \
331 \
332 // END DEFINE_GETSETOOP_VOLATILE.
333
334 DEFINE_GETSETOOP_VOLATILE(jboolean, Boolean)
335 DEFINE_GETSETOOP_VOLATILE(jbyte, Byte)
336 DEFINE_GETSETOOP_VOLATILE(jshort, Short);
337 DEFINE_GETSETOOP_VOLATILE(jchar, Char);
338 DEFINE_GETSETOOP_VOLATILE(jint, Int);
339 DEFINE_GETSETOOP_VOLATILE(jlong, Long);
340 DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
341 DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
342
343 #undef DEFINE_GETSETOOP_VOLATILE
344
345 UNSAFE_LEAF(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe)) {
346 OrderAccess::fence();
347 } UNSAFE_END
348
349 ////// Allocation requests
350
351 UNSAFE_ENTRY(jobject, Unsafe_AllocateInstance(JNIEnv *env, jobject unsafe, jclass cls)) {
352 JvmtiVMObjectAllocEventCollector oam;
353 instanceOop i = InstanceKlass::allocate_instance(JNIHandles::resolve_non_null(cls), "unsafe", CHECK_NULL);
354 return JNIHandles::make_local(THREAD, i);
355 } UNSAFE_END
356
357 UNSAFE_LEAF(jlong, Unsafe_AllocateMemory0(JNIEnv *env, jobject unsafe, jlong size)) {
358 size_t sz = (size_t)size;
359
360 assert(is_aligned(sz, HeapWordSize), "sz not aligned");
361
362 void* x = os::malloc(sz, mtOther);
363
364 return addr_to_java(x);
365 } UNSAFE_END
366
367 UNSAFE_LEAF(jlong, Unsafe_ReallocateMemory0(JNIEnv *env, jobject unsafe, jlong addr, jlong size)) {
368 void* p = addr_from_java(addr);
369 size_t sz = (size_t)size;
370
371 assert(is_aligned(sz, HeapWordSize), "sz not aligned");
372
373 void* x = os::realloc(p, sz, mtOther);
374
375 return addr_to_java(x);
376 } UNSAFE_END
377
378 UNSAFE_LEAF(void, Unsafe_FreeMemory0(JNIEnv *env, jobject unsafe, jlong addr)) {
379 void* p = addr_from_java(addr);
380
381 os::free(p);
382 } UNSAFE_END
383
384 UNSAFE_ENTRY_SCOPED(void, Unsafe_SetMemory0(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong size, jbyte value)) {
385 size_t sz = (size_t)size;
386
387 oop base = JNIHandles::resolve(obj);
388 void* p = index_oop_from_field_offset_long(base, offset);
389
390 {
391 GuardUnsafeAccess guard(thread);
392 if (StubRoutines::unsafe_setmemory() != nullptr) {
393 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
394 StubRoutines::UnsafeSetMemory_stub()(p, sz, value);
395 } else {
396 Copy::fill_to_memory_atomic(p, sz, value);
397 }
398 }
399 } UNSAFE_END
400
401 UNSAFE_ENTRY_SCOPED(void, Unsafe_CopyMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size)) {
402 size_t sz = (size_t)size;
403
404 oop srcp = JNIHandles::resolve(srcObj);
405 oop dstp = JNIHandles::resolve(dstObj);
406
407 void* src = index_oop_from_field_offset_long(srcp, srcOffset);
408 void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
409 {
410 GuardUnsafeAccess guard(thread);
411 if (StubRoutines::unsafe_arraycopy() != nullptr) {
412 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
413 StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
414 } else {
415 Copy::conjoint_memory_atomic(src, dst, sz);
416 }
417 }
418 } UNSAFE_END
419
420 UNSAFE_ENTRY_SCOPED(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
421 size_t sz = (size_t)size;
422 size_t esz = (size_t)elemSize;
423
424 oop srcp = JNIHandles::resolve(srcObj);
425 oop dstp = JNIHandles::resolve(dstObj);
426
427 address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
428 address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
429
430 {
431 GuardUnsafeAccess guard(thread);
432 Copy::conjoint_swap(src, dst, sz, esz);
433 }
434 } UNSAFE_END
435
436 UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
437 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
438 #ifdef ASSERT
439 if (TraceMemoryWriteback) {
440 tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
441 }
442 #endif
443
444 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
445 assert(StubRoutines::data_cache_writeback() != nullptr, "sanity");
446 (StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
447 } UNSAFE_END
448
449 static void doWriteBackSync0(bool is_pre)
450 {
451 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
452 assert(StubRoutines::data_cache_writeback_sync() != nullptr, "sanity");
453 (StubRoutines::DataCacheWritebackSync_stub())(is_pre);
454 }
455
456 UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
457 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
458 #ifdef ASSERT
459 if (TraceMemoryWriteback) {
460 tty->print_cr("Unsafe: writeback pre-sync");
461 }
462 #endif
463
464 doWriteBackSync0(true);
465 } UNSAFE_END
466
467 UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
468 assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
469 #ifdef ASSERT
470 if (TraceMemoryWriteback) {
471 tty->print_cr("Unsafe: writeback pre-sync");
472 }
473 #endif
474
475 doWriteBackSync0(false);
476 } UNSAFE_END
477
478 ////// Random queries
479
480 static jlong find_field_offset(jclass clazz, jstring name, TRAPS) {
481 assert(clazz != nullptr, "clazz must not be null");
482 assert(name != nullptr, "name must not be null");
483
484 ResourceMark rm(THREAD);
485 char *utf_name = java_lang_String::as_utf8_string(JNIHandles::resolve_non_null(name));
486
487 InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(clazz)));
488
489 jint offset = -1;
490 for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
491 Symbol *name = fs.name();
492 if (name->equals(utf_name)) {
493 offset = fs.offset();
494 break;
495 }
496 }
497 if (offset < 0) {
498 THROW_0(vmSymbols::java_lang_InternalError());
499 }
500 return field_offset_from_byte_offset(offset);
501 }
502
503 static jlong find_field_offset(jobject field, int must_be_static, TRAPS) {
504 assert(field != nullptr, "field must not be null");
505
506 oop reflected = JNIHandles::resolve_non_null(field);
507 oop mirror = java_lang_reflect_Field::clazz(reflected);
508 Klass* k = java_lang_Class::as_Klass(mirror);
509 int slot = java_lang_reflect_Field::slot(reflected);
510 int modifiers = java_lang_reflect_Field::modifiers(reflected);
511
512 if (must_be_static >= 0) {
513 int really_is_static = ((modifiers & JVM_ACC_STATIC) != 0);
514 if (must_be_static != really_is_static) {
515 THROW_0(vmSymbols::java_lang_IllegalArgumentException());
516 }
517 }
518
519 int offset = InstanceKlass::cast(k)->field_offset(slot);
520 return field_offset_from_byte_offset(offset);
521 }
522
523 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
524 return find_field_offset(field, 0, THREAD);
525 } UNSAFE_END
526
527 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset1(JNIEnv *env, jobject unsafe, jclass c, jstring name)) {
528 return find_field_offset(c, name, THREAD);
529 } UNSAFE_END
530
531 UNSAFE_ENTRY(jlong, Unsafe_StaticFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
532 return find_field_offset(field, 1, THREAD);
533 } UNSAFE_END
534
535 UNSAFE_ENTRY(jobject, Unsafe_StaticFieldBase0(JNIEnv *env, jobject unsafe, jobject field)) {
536 assert(field != nullptr, "field must not be null");
537
538 // Note: In this VM implementation, a field address is always a short
539 // offset from the base of a klass metaobject. Thus, the full dynamic
540 // range of the return type is never used. However, some implementations
541 // might put the static field inside an array shared by many classes,
542 // or even at a fixed address, in which case the address could be quite
543 // large. In that last case, this function would return null, since
544 // the address would operate alone, without any base pointer.
545
546 oop reflected = JNIHandles::resolve_non_null(field);
547 oop mirror = java_lang_reflect_Field::clazz(reflected);
548 int modifiers = java_lang_reflect_Field::modifiers(reflected);
549
550 if ((modifiers & JVM_ACC_STATIC) == 0) {
551 THROW_0(vmSymbols::java_lang_IllegalArgumentException());
552 }
553
554 return JNIHandles::make_local(THREAD, mirror);
555 } UNSAFE_END
556
557 UNSAFE_ENTRY(void, Unsafe_EnsureClassInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
558 assert(clazz != nullptr, "clazz must not be null");
559
560 oop mirror = JNIHandles::resolve_non_null(clazz);
561
562 Klass* klass = java_lang_Class::as_Klass(mirror);
563 if (klass != nullptr && klass->should_be_initialized()) {
564 InstanceKlass* k = InstanceKlass::cast(klass);
565 k->initialize(CHECK);
566 }
567 }
568 UNSAFE_END
569
570 UNSAFE_ENTRY(jboolean, Unsafe_ShouldBeInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
571 assert(clazz != nullptr, "clazz must not be null");
572
573 oop mirror = JNIHandles::resolve_non_null(clazz);
574 Klass* klass = java_lang_Class::as_Klass(mirror);
575
576 if (klass != nullptr && klass->should_be_initialized()) {
577 return true;
578 }
579
580 return false;
581 }
582 UNSAFE_END
583
584 static void getBaseAndScale(int& base, int& scale, jclass clazz, TRAPS) {
585 assert(clazz != nullptr, "clazz must not be null");
586
587 oop mirror = JNIHandles::resolve_non_null(clazz);
588 Klass* k = java_lang_Class::as_Klass(mirror);
589
590 if (k == nullptr || !k->is_array_klass()) {
591 THROW(vmSymbols::java_lang_InvalidClassException());
592 } else if (k->is_objArray_klass()) {
593 base = arrayOopDesc::base_offset_in_bytes(T_OBJECT);
594 scale = heapOopSize;
595 } else if (k->is_typeArray_klass()) {
596 TypeArrayKlass* tak = TypeArrayKlass::cast(k);
597 base = tak->array_header_in_bytes();
598 assert(base == arrayOopDesc::base_offset_in_bytes(tak->element_type()), "array_header_size semantics ok");
599 scale = (1 << tak->log2_element_size());
600 } else {
601 ShouldNotReachHere();
602 }
603 }
604
605 UNSAFE_ENTRY(jint, Unsafe_ArrayBaseOffset0(JNIEnv *env, jobject unsafe, jclass clazz)) {
606 int base = 0, scale = 0;
607 getBaseAndScale(base, scale, clazz, CHECK_0);
608
609 return field_offset_from_byte_offset(base);
610 } UNSAFE_END
611
612
613 UNSAFE_ENTRY(jint, Unsafe_ArrayIndexScale0(JNIEnv *env, jobject unsafe, jclass clazz)) {
614 int base = 0, scale = 0;
615 getBaseAndScale(base, scale, clazz, CHECK_0);
616
617 // This VM packs both fields and array elements down to the byte.
618 // But watch out: If this changes, so that array references for
619 // a given primitive type (say, T_BOOLEAN) use different memory units
620 // than fields, this method MUST return zero for such arrays.
621 // For example, the VM used to store sub-word sized fields in full
622 // words in the object layout, so that accessors like getByte(Object,int)
623 // did not really do what one might expect for arrays. Therefore,
624 // this function used to report a zero scale factor, so that the user
625 // would know not to attempt to access sub-word array elements.
626 // // Code for unpacked fields:
627 // if (scale < wordSize) return 0;
628
629 // The following allows for a pretty general fieldOffset cookie scheme,
630 // but requires it to be linear in byte offset.
631 return field_offset_from_byte_offset(scale) - field_offset_from_byte_offset(0);
632 } UNSAFE_END
633
634
635 static inline void throw_new(JNIEnv *env, const char *ename) {
636 jclass cls = env->FindClass(ename);
637 if (env->ExceptionCheck()) {
638 env->ExceptionClear();
639 tty->print_cr("Unsafe: cannot throw %s because FindClass has failed", ename);
640 return;
641 }
642
643 env->ThrowNew(cls, nullptr);
644 }
645
646 static jclass Unsafe_DefineClass_impl(JNIEnv *env, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd) {
647 // Code lifted from JDK 1.3 ClassLoader.c
648
649 jbyte *body;
650 char *utfName = nullptr;
651 jclass result = 0;
652 char buf[128];
653
654 assert(data != nullptr, "Class bytes must not be null");
655 assert(length >= 0, "length must not be negative: %d", length);
656
657 if (UsePerfData) {
658 ClassLoader::unsafe_defineClassCallCounter()->inc();
659 }
660
661 body = NEW_C_HEAP_ARRAY_RETURN_NULL(jbyte, length, mtInternal);
662 if (body == nullptr) {
663 throw_new(env, "java/lang/OutOfMemoryError");
664 return 0;
665 }
666
667 env->GetByteArrayRegion(data, offset, length, body);
668 if (env->ExceptionOccurred()) {
669 goto free_body;
670 }
671
672 if (name != nullptr) {
673 uint len = env->GetStringUTFLength(name);
674 int unicode_len = env->GetStringLength(name);
675
676 if (len >= sizeof(buf)) {
677 utfName = NEW_C_HEAP_ARRAY_RETURN_NULL(char, len + 1, mtInternal);
678 if (utfName == nullptr) {
679 throw_new(env, "java/lang/OutOfMemoryError");
680 goto free_body;
681 }
682 } else {
683 utfName = buf;
684 }
685
686 env->GetStringUTFRegion(name, 0, unicode_len, utfName);
687
688 for (uint i = 0; i < len; i++) {
689 if (utfName[i] == '.') utfName[i] = '/';
690 }
691 }
692
693 result = JVM_DefineClass(env, utfName, loader, body, length, pd);
694
695 if (utfName && utfName != buf) {
696 FREE_C_HEAP_ARRAY(char, utfName);
697 }
698
699 free_body:
700 FREE_C_HEAP_ARRAY(jbyte, body);
701 return result;
702 }
703
704
705 UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd)) {
706 ThreadToNativeFromVM ttnfv(thread);
707
708 return Unsafe_DefineClass_impl(env, name, data, offset, length, loader, pd);
709 } UNSAFE_END
710
711
712 UNSAFE_ENTRY(void, Unsafe_ThrowException(JNIEnv *env, jobject unsafe, jthrowable thr)) {
713 ThreadToNativeFromVM ttnfv(thread);
714 env->Throw(thr);
715 } UNSAFE_END
716
717 // JSR166 ------------------------------------------------------------------
718
719 UNSAFE_ENTRY(jobject, Unsafe_CompareAndExchangeReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
720 oop x = JNIHandles::resolve(x_h);
721 oop e = JNIHandles::resolve(e_h);
722 oop p = JNIHandles::resolve(obj);
723 assert_field_offset_sane(p, offset);
724 oop res = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
725 return JNIHandles::make_local(THREAD, res);
726 } UNSAFE_END
727
728 UNSAFE_ENTRY_SCOPED(jint, Unsafe_CompareAndExchangeInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
729 oop p = JNIHandles::resolve(obj);
730 volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
731 return Atomic::cmpxchg(addr, e, x);
732 } UNSAFE_END
733
734 UNSAFE_ENTRY_SCOPED(jlong, Unsafe_CompareAndExchangeLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
735 oop p = JNIHandles::resolve(obj);
736 volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
737 return Atomic::cmpxchg(addr, e, x);
738 } UNSAFE_END
739
740 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
741 oop x = JNIHandles::resolve(x_h);
742 oop e = JNIHandles::resolve(e_h);
743 oop p = JNIHandles::resolve(obj);
744 assert_field_offset_sane(p, offset);
745 oop ret = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
746 return ret == e;
747 } UNSAFE_END
748
749 UNSAFE_ENTRY_SCOPED(jboolean, Unsafe_CompareAndSetInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
750 oop p = JNIHandles::resolve(obj);
751 volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
752 return Atomic::cmpxchg(addr, e, x) == e;
753 } UNSAFE_END
754
755 UNSAFE_ENTRY_SCOPED(jboolean, Unsafe_CompareAndSetLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
756 oop p = JNIHandles::resolve(obj);
757 volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
758 return Atomic::cmpxchg(addr, e, x) == e;
759 } UNSAFE_END
760
761 static void post_thread_park_event(EventThreadPark* event, const oop obj, jlong timeout_nanos, jlong until_epoch_millis) {
762 assert(event != nullptr, "invariant");
763 event->set_parkedClass((obj != nullptr) ? obj->klass() : nullptr);
764 event->set_timeout(timeout_nanos);
765 event->set_until(until_epoch_millis);
766 event->set_address((obj != nullptr) ? (u8)cast_from_oop<uintptr_t>(obj) : 0);
767 event->commit();
768 }
769
770 UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time)) {
771 HOTSPOT_THREAD_PARK_BEGIN((uintptr_t) thread->parker(), (int) isAbsolute, time);
772 EventThreadPark event;
773
774 JavaThreadParkedState jtps(thread, time != 0);
775 thread->parker()->park(isAbsolute != 0, time);
776 if (event.should_commit()) {
777 const oop obj = thread->current_park_blocker();
778 if (time == 0) {
779 post_thread_park_event(&event, obj, min_jlong, min_jlong);
780 } else {
781 if (isAbsolute != 0) {
782 post_thread_park_event(&event, obj, min_jlong, time);
783 } else {
784 post_thread_park_event(&event, obj, time, min_jlong);
785 }
786 }
787 }
788 HOTSPOT_THREAD_PARK_END((uintptr_t) thread->parker());
789 } UNSAFE_END
790
791 UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread)) {
792 if (jthread != nullptr) {
793 oop thread_oop = JNIHandles::resolve_non_null(jthread);
794 // Get the JavaThread* stored in the java.lang.Thread object _before_
795 // the embedded ThreadsListHandle is constructed so we know if the
796 // early life stage of the JavaThread* is protected. We use acquire
797 // here to ensure that if we see a non-nullptr value, then we also
798 // see the main ThreadsList updates from the JavaThread* being added.
799 FastThreadsListHandle ftlh(thread_oop, java_lang_Thread::thread_acquire(thread_oop));
800 JavaThread* thr = ftlh.protected_java_thread();
801 if (thr != nullptr) {
802 // The still live JavaThread* is protected by the FastThreadsListHandle
803 // so it is safe to access.
804 Parker* p = thr->parker();
805 HOTSPOT_THREAD_UNPARK((uintptr_t) p);
806 p->unpark();
807 }
808 } // FastThreadsListHandle is destroyed here.
809 } UNSAFE_END
810
811 UNSAFE_ENTRY(jint, Unsafe_GetLoadAverage0(JNIEnv *env, jobject unsafe, jdoubleArray loadavg, jint nelem)) {
812 const int max_nelem = 3;
813 double la[max_nelem];
814 jint ret;
815
816 typeArrayOop a = typeArrayOop(JNIHandles::resolve_non_null(loadavg));
817 assert(a->is_typeArray(), "must be type array");
818
819 ret = os::loadavg(la, nelem);
820 if (ret == -1) {
821 return -1;
822 }
823
824 // if successful, ret is the number of samples actually retrieved.
825 assert(ret >= 0 && ret <= max_nelem, "Unexpected loadavg return value");
826 switch(ret) {
827 case 3: a->double_at_put(2, (jdouble)la[2]); // fall through
828 case 2: a->double_at_put(1, (jdouble)la[1]); // fall through
829 case 1: a->double_at_put(0, (jdouble)la[0]); break;
830 }
831
832 return ret;
833 } UNSAFE_END
834
835
836 /// JVM_RegisterUnsafeMethods
837
838 #define ADR "J"
839
840 #define LANG "Ljava/lang/"
841
842 #define OBJ LANG "Object;"
843 #define CLS LANG "Class;"
844 #define FLD LANG "reflect/Field;"
845 #define THR LANG "Throwable;"
846
847 #define DC_Args LANG "String;[BII" LANG "ClassLoader;" "Ljava/security/ProtectionDomain;"
848 #define DAC_Args CLS "[B[" OBJ
849
850 #define CC (char*) /*cast a literal from (const char*)*/
851 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
852
853 #define DECLARE_GETPUTOOP(Type, Desc) \
854 {CC "get" #Type, CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type)}, \
855 {CC "put" #Type, CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type)}, \
856 {CC "get" #Type "Volatile", CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type##Volatile)}, \
857 {CC "put" #Type "Volatile", CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type##Volatile)}
858
859
860 static JNINativeMethod jdk_internal_misc_Unsafe_methods[] = {
861 {CC "getReference", CC "(" OBJ "J)" OBJ "", FN_PTR(Unsafe_GetReference)},
862 {CC "putReference", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReference)},
863 {CC "getReferenceVolatile", CC "(" OBJ "J)" OBJ, FN_PTR(Unsafe_GetReferenceVolatile)},
864 {CC "putReferenceVolatile", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReferenceVolatile)},
865
866 {CC "getUncompressedObject", CC "(" ADR ")" OBJ, FN_PTR(Unsafe_GetUncompressedObject)},
867
868 DECLARE_GETPUTOOP(Boolean, Z),
869 DECLARE_GETPUTOOP(Byte, B),
870 DECLARE_GETPUTOOP(Short, S),
871 DECLARE_GETPUTOOP(Char, C),
872 DECLARE_GETPUTOOP(Int, I),
873 DECLARE_GETPUTOOP(Long, J),
874 DECLARE_GETPUTOOP(Float, F),
875 DECLARE_GETPUTOOP(Double, D),
876
877 {CC "allocateMemory0", CC "(J)" ADR, FN_PTR(Unsafe_AllocateMemory0)},
878 {CC "reallocateMemory0", CC "(" ADR "J)" ADR, FN_PTR(Unsafe_ReallocateMemory0)},
879 {CC "freeMemory0", CC "(" ADR ")V", FN_PTR(Unsafe_FreeMemory0)},
880
881 {CC "objectFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_ObjectFieldOffset0)},
882 {CC "objectFieldOffset1", CC "(" CLS LANG "String;)J", FN_PTR(Unsafe_ObjectFieldOffset1)},
883 {CC "staticFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_StaticFieldOffset0)},
884 {CC "staticFieldBase0", CC "(" FLD ")" OBJ, FN_PTR(Unsafe_StaticFieldBase0)},
885 {CC "ensureClassInitialized0", CC "(" CLS ")V", FN_PTR(Unsafe_EnsureClassInitialized0)},
886 {CC "arrayBaseOffset0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayBaseOffset0)},
887 {CC "arrayIndexScale0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayIndexScale0)},
888
889 {CC "defineClass0", CC "(" DC_Args ")" CLS, FN_PTR(Unsafe_DefineClass0)},
890 {CC "allocateInstance", CC "(" CLS ")" OBJ, FN_PTR(Unsafe_AllocateInstance)},
891 {CC "throwException", CC "(" THR ")V", FN_PTR(Unsafe_ThrowException)},
892 {CC "compareAndSetReference",CC "(" OBJ "J" OBJ "" OBJ ")Z", FN_PTR(Unsafe_CompareAndSetReference)},
893 {CC "compareAndSetInt", CC "(" OBJ "J""I""I"")Z", FN_PTR(Unsafe_CompareAndSetInt)},
894 {CC "compareAndSetLong", CC "(" OBJ "J""J""J"")Z", FN_PTR(Unsafe_CompareAndSetLong)},
895 {CC "compareAndExchangeReference", CC "(" OBJ "J" OBJ "" OBJ ")" OBJ, FN_PTR(Unsafe_CompareAndExchangeReference)},
896 {CC "compareAndExchangeInt", CC "(" OBJ "J""I""I"")I", FN_PTR(Unsafe_CompareAndExchangeInt)},
897 {CC "compareAndExchangeLong", CC "(" OBJ "J""J""J"")J", FN_PTR(Unsafe_CompareAndExchangeLong)},
898
899 {CC "park", CC "(ZJ)V", FN_PTR(Unsafe_Park)},
900 {CC "unpark", CC "(" OBJ ")V", FN_PTR(Unsafe_Unpark)},
901
902 {CC "getLoadAverage0", CC "([DI)I", FN_PTR(Unsafe_GetLoadAverage0)},
903
904 {CC "copyMemory0", CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory0)},
905 {CC "copySwapMemory0", CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
906 {CC "writeback0", CC "(" "J" ")V", FN_PTR(Unsafe_WriteBack0)},
907 {CC "writebackPreSync0", CC "()V", FN_PTR(Unsafe_WriteBackPreSync0)},
908 {CC "writebackPostSync0", CC "()V", FN_PTR(Unsafe_WriteBackPostSync0)},
909 {CC "setMemory0", CC "(" OBJ "JJB)V", FN_PTR(Unsafe_SetMemory0)},
910
911 {CC "shouldBeInitialized0", CC "(" CLS ")Z", FN_PTR(Unsafe_ShouldBeInitialized0)},
912
913 {CC "fullFence", CC "()V", FN_PTR(Unsafe_FullFence)},
914 };
915
916 #undef CC
917 #undef FN_PTR
918
919 #undef ADR
920 #undef LANG
921 #undef OBJ
922 #undef CLS
923 #undef FLD
924 #undef THR
925 #undef DC_Args
926 #undef DAC_Args
927
928 #undef DECLARE_GETPUTOOP
929
930
931 // This function is exported, used by NativeLookup.
932 // The Unsafe_xxx functions above are called only from the interpreter.
933 // The optimizer looks at names and signatures to recognize
934 // individual functions.
935
936 JVM_ENTRY(void, JVM_RegisterJDKInternalMiscUnsafeMethods(JNIEnv *env, jclass unsafeclass)) {
937 ThreadToNativeFromVM ttnfv(thread);
938
939 int ok = env->RegisterNatives(unsafeclass, jdk_internal_misc_Unsafe_methods, sizeof(jdk_internal_misc_Unsafe_methods)/sizeof(JNINativeMethod));
940 guarantee(ok == 0, "register jdk.internal.misc.Unsafe natives");
941 } JVM_END