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   // we use this method at some places for writing to 0 e.g. to cause a crash;
246   // ubsan does not know that this is the desired behavior
247 #if defined(__clang__) || defined(__GNUC__)
248 __attribute__((no_sanitize("undefined")))
249 #endif
250   void put(T x) {
251     GuardUnsafeAccess guard(_thread);
252     *addr() = normalize_for_write(x);
253   }
254 
255 
256   T get_volatile() {
257     GuardUnsafeAccess guard(_thread);
258     volatile T ret = RawAccess<MO_SEQ_CST>::load(addr());
259     return normalize_for_read(ret);
260   }
261 
262   void put_volatile(T x) {
263     GuardUnsafeAccess guard(_thread);
264     RawAccess<MO_SEQ_CST>::store(addr(), normalize_for_write(x));
265   }
266 };
267 
268 // These functions allow a null base pointer with an arbitrary address.
269 // But if the base pointer is non-null, the offset should make some sense.
270 // That is, it should be in the range [0, MAX_OBJECT_SIZE].
271 UNSAFE_ENTRY(jobject, Unsafe_GetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
272   oop p = JNIHandles::resolve(obj);
273   assert_field_offset_sane(p, offset);
274   oop v = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
275   return JNIHandles::make_local(THREAD, v);
276 } UNSAFE_END
277 
278 UNSAFE_ENTRY(void, Unsafe_PutReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
279   oop x = JNIHandles::resolve(x_h);
280   oop p = JNIHandles::resolve(obj);
281   assert_field_offset_sane(p, offset);
282   HeapAccess<ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
283 } UNSAFE_END
284 
285 UNSAFE_ENTRY(jobject, Unsafe_GetReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
286   oop p = JNIHandles::resolve(obj);
287   assert_field_offset_sane(p, offset);
288   oop v = HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
289   return JNIHandles::make_local(THREAD, v);
290 } UNSAFE_END
291 
292 UNSAFE_ENTRY(void, Unsafe_PutReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
293   oop x = JNIHandles::resolve(x_h);
294   oop p = JNIHandles::resolve(obj);
295   assert_field_offset_sane(p, offset);
296   HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
297 } UNSAFE_END
298 
299 UNSAFE_ENTRY(jobject, Unsafe_GetUncompressedObject(JNIEnv *env, jobject unsafe, jlong addr)) {
300   oop v = *(oop*) (address) addr;
301   return JNIHandles::make_local(THREAD, v);
302 } UNSAFE_END
303 
304 #define DEFINE_GETSETOOP(java_type, Type) \
305  \
306 UNSAFE_ENTRY_SCOPED(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
307   return MemoryAccess<java_type>(thread, obj, offset).get(); \
308 } UNSAFE_END \
309  \
310 UNSAFE_ENTRY_SCOPED(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
311   MemoryAccess<java_type>(thread, obj, offset).put(x); \
312 } UNSAFE_END \
313  \
314 // END DEFINE_GETSETOOP.
315 
316 DEFINE_GETSETOOP(jboolean, Boolean)
317 DEFINE_GETSETOOP(jbyte, Byte)
318 DEFINE_GETSETOOP(jshort, Short);
319 DEFINE_GETSETOOP(jchar, Char);
320 DEFINE_GETSETOOP(jint, Int);
321 DEFINE_GETSETOOP(jlong, Long);
322 DEFINE_GETSETOOP(jfloat, Float);
323 DEFINE_GETSETOOP(jdouble, Double);
324 
325 #undef DEFINE_GETSETOOP
326 
327 #define DEFINE_GETSETOOP_VOLATILE(java_type, Type) \
328  \
329 UNSAFE_ENTRY_SCOPED(java_type, Unsafe_Get##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
330   return MemoryAccess<java_type>(thread, obj, offset).get_volatile(); \
331 } UNSAFE_END \
332  \
333 UNSAFE_ENTRY_SCOPED(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
334   MemoryAccess<java_type>(thread, obj, offset).put_volatile(x); \
335 } UNSAFE_END \
336  \
337 // END DEFINE_GETSETOOP_VOLATILE.
338 
339 DEFINE_GETSETOOP_VOLATILE(jboolean, Boolean)
340 DEFINE_GETSETOOP_VOLATILE(jbyte, Byte)
341 DEFINE_GETSETOOP_VOLATILE(jshort, Short);
342 DEFINE_GETSETOOP_VOLATILE(jchar, Char);
343 DEFINE_GETSETOOP_VOLATILE(jint, Int);
344 DEFINE_GETSETOOP_VOLATILE(jlong, Long);
345 DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
346 DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
347 
348 #undef DEFINE_GETSETOOP_VOLATILE
349 
350 UNSAFE_LEAF(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe)) {
351   OrderAccess::fence();
352 } UNSAFE_END
353 
354 ////// Allocation requests
355 
356 UNSAFE_ENTRY(jobject, Unsafe_AllocateInstance(JNIEnv *env, jobject unsafe, jclass cls)) {
357   JvmtiVMObjectAllocEventCollector oam;
358   instanceOop i = InstanceKlass::allocate_instance(JNIHandles::resolve_non_null(cls), "unsafe", CHECK_NULL);
359   return JNIHandles::make_local(THREAD, i);
360 } UNSAFE_END
361 
362 UNSAFE_LEAF(jlong, Unsafe_AllocateMemory0(JNIEnv *env, jobject unsafe, jlong size)) {
363   size_t sz = (size_t)size;
364 
365   assert(is_aligned(sz, HeapWordSize), "sz not aligned");
366 
367   void* x = os::malloc(sz, mtOther);
368 
369   return addr_to_java(x);
370 } UNSAFE_END
371 
372 UNSAFE_LEAF(jlong, Unsafe_ReallocateMemory0(JNIEnv *env, jobject unsafe, jlong addr, jlong size)) {
373   void* p = addr_from_java(addr);
374   size_t sz = (size_t)size;
375 
376   assert(is_aligned(sz, HeapWordSize), "sz not aligned");
377 
378   void* x = os::realloc(p, sz, mtOther);
379 
380   return addr_to_java(x);
381 } UNSAFE_END
382 
383 UNSAFE_LEAF(void, Unsafe_FreeMemory0(JNIEnv *env, jobject unsafe, jlong addr)) {
384   void* p = addr_from_java(addr);
385 
386   os::free(p);
387 } UNSAFE_END
388 
389 UNSAFE_ENTRY_SCOPED(void, Unsafe_SetMemory0(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong size, jbyte value)) {
390   size_t sz = (size_t)size;
391 
392   oop base = JNIHandles::resolve(obj);
393   void* p = index_oop_from_field_offset_long(base, offset);
394 
395   {
396     GuardUnsafeAccess guard(thread);
397     if (StubRoutines::unsafe_setmemory() != nullptr) {
398       MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
399       StubRoutines::UnsafeSetMemory_stub()(p, sz, value);
400     } else {
401       Copy::fill_to_memory_atomic(p, sz, value);
402     }
403   }
404 } UNSAFE_END
405 
406 UNSAFE_ENTRY_SCOPED(void, Unsafe_CopyMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size)) {
407   size_t sz = (size_t)size;
408 
409   oop srcp = JNIHandles::resolve(srcObj);
410   oop dstp = JNIHandles::resolve(dstObj);
411 
412   void* src = index_oop_from_field_offset_long(srcp, srcOffset);
413   void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
414   {
415     GuardUnsafeAccess guard(thread);
416     if (StubRoutines::unsafe_arraycopy() != nullptr) {
417       MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
418       StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
419     } else {
420       Copy::conjoint_memory_atomic(src, dst, sz);
421     }
422   }
423 } UNSAFE_END
424 
425 UNSAFE_ENTRY_SCOPED(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
426   size_t sz = (size_t)size;
427   size_t esz = (size_t)elemSize;
428 
429   oop srcp = JNIHandles::resolve(srcObj);
430   oop dstp = JNIHandles::resolve(dstObj);
431 
432   address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
433   address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
434 
435   {
436     GuardUnsafeAccess guard(thread);
437     Copy::conjoint_swap(src, dst, sz, esz);
438   }
439 } UNSAFE_END
440 
441 UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
442   assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
443 #ifdef ASSERT
444   if (TraceMemoryWriteback) {
445     tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
446   }
447 #endif
448 
449   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
450   assert(StubRoutines::data_cache_writeback() != nullptr, "sanity");
451   (StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
452 } UNSAFE_END
453 
454 static void doWriteBackSync0(bool is_pre)
455 {
456   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
457   assert(StubRoutines::data_cache_writeback_sync() != nullptr, "sanity");
458   (StubRoutines::DataCacheWritebackSync_stub())(is_pre);
459 }
460 
461 UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
462   assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
463 #ifdef ASSERT
464   if (TraceMemoryWriteback) {
465       tty->print_cr("Unsafe: writeback pre-sync");
466   }
467 #endif
468 
469   doWriteBackSync0(true);
470 } UNSAFE_END
471 
472 UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
473   assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
474 #ifdef ASSERT
475   if (TraceMemoryWriteback) {
476     tty->print_cr("Unsafe: writeback pre-sync");
477   }
478 #endif
479 
480   doWriteBackSync0(false);
481 } UNSAFE_END
482 
483 ////// Random queries
484 
485 static jlong find_field_offset(jclass clazz, jstring name, TRAPS) {
486   assert(clazz != nullptr, "clazz must not be null");
487   assert(name != nullptr, "name must not be null");
488 
489   ResourceMark rm(THREAD);
490   char *utf_name = java_lang_String::as_utf8_string(JNIHandles::resolve_non_null(name));
491 
492   InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(clazz)));
493 
494   jint offset = -1;
495   for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
496     Symbol *name = fs.name();
497     if (name->equals(utf_name)) {
498       offset = fs.offset();
499       break;
500     }
501   }
502   if (offset < 0) {
503     THROW_0(vmSymbols::java_lang_InternalError());
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_ObjectFieldOffset1(JNIEnv *env, jobject unsafe, jclass c, jstring name)) {
533   return find_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_0(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 = 0;
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 0;
670   }
671 
672   env->GetByteArrayRegion(data, offset, length, body);
673   if (env->ExceptionOccurred()) {
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(char, utfName);
702   }
703 
704  free_body:
705   FREE_C_HEAP_ARRAY(jbyte, 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_SCOPED(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 Atomic::cmpxchg(addr, e, x);
737 } UNSAFE_END
738 
739 UNSAFE_ENTRY_SCOPED(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 Atomic::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_SCOPED(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 Atomic::cmpxchg(addr, e, x) == e;
758 } UNSAFE_END
759 
760 UNSAFE_ENTRY_SCOPED(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 Atomic::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 "objectFieldOffset1", CC "(" CLS LANG "String;)J", FN_PTR(Unsafe_ObjectFieldOffset1)},
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