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 "logging/log.hpp"
  37 #include "logging/logStream.hpp"
  38 #include "oops/access.inline.hpp"
  39 #include "oops/fieldStreams.inline.hpp"
  40 #include "oops/flatArrayKlass.hpp"
  41 #include "oops/flatArrayOop.inline.hpp"
  42 #include "oops/inlineKlass.inline.hpp"
  43 #include "oops/instanceKlass.inline.hpp"
  44 #include "oops/klass.inline.hpp"
  45 #include "oops/objArrayOop.inline.hpp"
  46 #include "oops/oop.inline.hpp"
  47 #include "oops/typeArrayOop.inline.hpp"
  48 #include "prims/jvmtiExport.hpp"
  49 #include "prims/unsafe.hpp"
  50 #include "runtime/fieldDescriptor.inline.hpp"
  51 #include "runtime/globals.hpp"
  52 #include "runtime/handles.inline.hpp"
  53 #include "runtime/interfaceSupport.inline.hpp"
  54 #include "runtime/javaThread.inline.hpp"
  55 #include "runtime/jniHandles.inline.hpp"
  56 #include "runtime/orderAccess.hpp"
  57 #include "runtime/reflection.hpp"
  58 #include "runtime/sharedRuntime.hpp"
  59 #include "runtime/stubRoutines.hpp"
  60 #include "runtime/threadSMR.hpp"
  61 #include "runtime/vmOperations.hpp"
  62 #include "runtime/vm_version.hpp"
  63 #include "sanitizers/ub.hpp"
  64 #include "services/threadService.hpp"
  65 #include "utilities/align.hpp"
  66 #include "utilities/copy.hpp"
  67 #include "utilities/dtrace.hpp"
  68 #include "utilities/macros.hpp"
  69 
  70 /**
  71  * Implementation of the jdk.internal.misc.Unsafe class
  72  */
  73 
  74 
  75 #define MAX_OBJECT_SIZE \
  76   ( arrayOopDesc::base_offset_in_bytes(T_DOUBLE) \
  77     + ((julong)max_jint * sizeof(double)) )
  78 
  79 #define UNSAFE_ENTRY(result_type, header) \
  80   JVM_ENTRY(static result_type, header)
  81 
  82 #define UNSAFE_LEAF(result_type, header) \
  83   JVM_LEAF(static result_type, header)
  84 
  85 // All memory access methods (e.g. getInt, copyMemory) must use this macro.
  86 // We call these methods "scoped" methods, as access to these methods is
  87 // typically governed by a "scope" (a MemorySessionImpl object), and no
  88 // access is allowed when the scope is no longer alive.
  89 //
  90 // Closing a scope object (cf. scopedMemoryAccess.cpp) can install
  91 // an async exception during a safepoint. When that happens,
  92 // scoped methods are not allowed to touch the underlying memory (as that
  93 // memory might have been released). Therefore, when entering a scoped method
  94 // we check if an async exception has been installed, and return immediately
  95 // if that is the case.
  96 //
  97 // As a rule, we disallow safepoints in the middle of a scoped method.
  98 // If an async exception handshake were installed in such a safepoint,
  99 // memory access might still occur before the handshake is honored by
 100 // the accessing thread.
 101 //
 102 // Corollary: as threads in native state are considered to be at a safepoint,
 103 // scoped methods must NOT be executed while in the native thread state.
 104 // Because of this, there can be no UNSAFE_LEAF_SCOPED.
 105 #define UNSAFE_ENTRY_SCOPED(result_type, header) \
 106   JVM_ENTRY(static result_type, header) \
 107   if (thread->has_async_exception_condition()) {return (result_type)0;}
 108 
 109 #define UNSAFE_END JVM_END
 110 
 111 
 112 static inline void* addr_from_java(jlong addr) {
 113   // This assert fails in a variety of ways on 32-bit systems.
 114   // It is impossible to predict whether native code that converts
 115   // pointers to longs will sign-extend or zero-extend the addresses.
 116   //assert(addr == (uintptr_t)addr, "must not be odd high bits");
 117   return (void*)(uintptr_t)addr;
 118 }
 119 
 120 static inline jlong addr_to_java(void* p) {
 121   assert(p == (void*)(uintptr_t)p, "must not be odd high bits");
 122   return (uintptr_t)p;
 123 }
 124 
 125 
 126 // Note: The VM's obj_field and related accessors use byte-scaled
 127 // ("unscaled") offsets, just as the unsafe methods do.
 128 
 129 // However, the method Unsafe.fieldOffset explicitly declines to
 130 // guarantee this.  The field offset values manipulated by the Java user
 131 // through the Unsafe API are opaque cookies that just happen to be byte
 132 // offsets.  We represent this state of affairs by passing the cookies
 133 // through conversion functions when going between the VM and the Unsafe API.
 134 // The conversion functions just happen to be no-ops at present.
 135 
 136 static inline jlong field_offset_to_byte_offset(jlong field_offset) {
 137   return field_offset;
 138 }
 139 
 140 static inline int field_offset_from_byte_offset(int byte_offset) {
 141   return byte_offset;
 142 }
 143 
 144 static inline void assert_field_offset_sane(oop p, jlong field_offset) {
 145 #ifdef ASSERT
 146   jlong byte_offset = field_offset_to_byte_offset(field_offset);
 147 
 148   if (p != nullptr) {
 149     assert(byte_offset >= 0 && byte_offset <= (jlong)MAX_OBJECT_SIZE, "sane offset");
 150     if (byte_offset == (jint)byte_offset) {
 151       void* ptr_plus_disp = cast_from_oop<address>(p) + byte_offset;
 152       assert(p->field_addr<void>((jint)byte_offset) == ptr_plus_disp,
 153              "raw [ptr+disp] must be consistent with oop::field_addr");
 154     }
 155     jlong p_size = HeapWordSize * (jlong)(p->size());
 156     assert(byte_offset < p_size, "Unsafe access: offset " INT64_FORMAT " > object's size " INT64_FORMAT, (int64_t)byte_offset, (int64_t)p_size);
 157   }
 158 #endif
 159 }
 160 
 161 static inline void* index_oop_from_field_offset_long(oop p, jlong field_offset) {
 162   assert_field_offset_sane(p, field_offset);
 163   uintptr_t base_address = cast_from_oop<uintptr_t>(p);
 164   uintptr_t byte_offset  = (uintptr_t)field_offset_to_byte_offset(field_offset);
 165   return (void*)(base_address + byte_offset);
 166 }
 167 
 168 // Externally callable versions:
 169 // (Use these in compiler intrinsics which emulate unsafe primitives.)
 170 jlong Unsafe_field_offset_to_byte_offset(jlong field_offset) {
 171   return field_offset;
 172 }
 173 jlong Unsafe_field_offset_from_byte_offset(jlong byte_offset) {
 174   return byte_offset;
 175 }
 176 
 177 ///// Data read/writes on the Java heap and in native (off-heap) memory
 178 
 179 /**
 180  * Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
 181  */
 182 class GuardUnsafeAccess {
 183   JavaThread* _thread;
 184 
 185 public:
 186   GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
 187     // native/off-heap access which may raise SIGBUS if accessing
 188     // memory mapped file data in a region of the file which has
 189     // been truncated and is now invalid.
 190     _thread->set_doing_unsafe_access(true);
 191   }
 192 
 193   ~GuardUnsafeAccess() {
 194     _thread->set_doing_unsafe_access(false);
 195   }
 196 };
 197 
 198 /**
 199  * Helper class for accessing memory.
 200  *
 201  * Normalizes values and wraps accesses in
 202  * JavaThread::doing_unsafe_access() if needed.
 203  */
 204 template <typename T>
 205 class MemoryAccess : StackObj {
 206   JavaThread* _thread;
 207   oop _obj;
 208   ptrdiff_t _offset;
 209 
 210   // Resolves and returns the address of the memory access.
 211   // This raw memory access may fault, so we make sure it happens within the
 212   // guarded scope by making the access volatile at least. Since the store
 213   // of Thread::set_doing_unsafe_access() is also volatile, these accesses
 214   // can not be reordered by the compiler. Therefore, if the access triggers
 215   // a fault, we will know that Thread::doing_unsafe_access() returns true.
 216   volatile T* addr() {
 217     void* addr = index_oop_from_field_offset_long(_obj, _offset);
 218     return static_cast<volatile T*>(addr);
 219   }
 220 
 221   template <typename U>
 222   U normalize_for_write(U x) {
 223     return x;
 224   }
 225 
 226   jboolean normalize_for_write(jboolean x) {
 227     return x & 1;
 228   }
 229 
 230   template <typename U>
 231   U normalize_for_read(U x) {
 232     return x;
 233   }
 234 
 235   jboolean normalize_for_read(jboolean x) {
 236     return x != 0;
 237   }
 238 
 239 public:
 240   MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
 241     : _thread(thread), _obj(JNIHandles::resolve(obj)), _offset((ptrdiff_t)offset) {
 242     assert_field_offset_sane(_obj, offset);
 243   }
 244 
 245   T get() {
 246     GuardUnsafeAccess guard(_thread);
 247     return normalize_for_read(*addr());
 248   }
 249 
 250   // we use this method at some places for writing to 0 e.g. to cause a crash;
 251   // ubsan does not know that this is the desired behavior
 252   ATTRIBUTE_NO_UBSAN
 253   void put(T x) {
 254     GuardUnsafeAccess guard(_thread);
 255     assert(_obj == nullptr || !_obj->is_inline_type() || _obj->mark().is_larval_state(), "must be an object instance or a larval inline type");
 256     *addr() = normalize_for_write(x);
 257   }
 258 
 259   T get_volatile() {
 260     GuardUnsafeAccess guard(_thread);
 261     volatile T ret = RawAccess<MO_SEQ_CST>::load(addr());
 262     return normalize_for_read(ret);
 263   }
 264 
 265   void put_volatile(T x) {
 266     GuardUnsafeAccess guard(_thread);
 267     RawAccess<MO_SEQ_CST>::store(addr(), normalize_for_write(x));
 268   }
 269 };
 270 
 271 #ifdef ASSERT
 272 /*
 273  * Get the field descriptor of the field of the given object at the given offset.
 274  */
 275 static bool get_field_descriptor(oop p, jlong offset, fieldDescriptor* fd) {
 276   bool found = false;
 277   Klass* k = p->klass();
 278   if (k->is_instance_klass()) {
 279     InstanceKlass* ik = InstanceKlass::cast(k);
 280     found = ik->find_field_from_offset((int)offset, false, fd);
 281     if (!found && ik->is_mirror_instance_klass()) {
 282       Klass* k2 = java_lang_Class::as_Klass(p);
 283       if (k2->is_instance_klass()) {
 284         ik = InstanceKlass::cast(k2);
 285         found = ik->find_field_from_offset((int)offset, true, fd);
 286       }
 287     }
 288   }
 289   return found;
 290 }
 291 #endif // ASSERT
 292 
 293 static void assert_and_log_unsafe_value_access(oop p, jlong offset, InlineKlass* vk) {
 294   Klass* k = p->klass();
 295 #ifdef ASSERT
 296   if (k->is_instance_klass()) {
 297     assert_field_offset_sane(p, offset);
 298     fieldDescriptor fd;
 299     bool found = get_field_descriptor(p, offset, &fd);
 300     if (found) {
 301       assert(found, "value field not found");
 302       assert(fd.is_flat(), "field not flat");
 303     } else {
 304       if (log_is_enabled(Trace, valuetypes)) {
 305         log_trace(valuetypes)("not a field in %s at offset " UINT64_FORMAT_X,
 306                               p->klass()->external_name(), (uint64_t)offset);
 307       }
 308     }
 309   } else if (k->is_flatArray_klass()) {
 310     FlatArrayKlass* vak = FlatArrayKlass::cast(k);
 311     int index = (offset - vak->array_header_in_bytes()) / vak->element_byte_size();
 312     address dest = (address)((flatArrayOop)p)->value_at_addr(index, vak->layout_helper());
 313     assert(dest == (cast_from_oop<address>(p) + offset), "invalid offset");
 314   } else {
 315     ShouldNotReachHere();
 316   }
 317 #endif // ASSERT
 318   if (log_is_enabled(Trace, valuetypes)) {
 319     if (k->is_flatArray_klass()) {
 320       FlatArrayKlass* vak = FlatArrayKlass::cast(k);
 321       int index = (offset - vak->array_header_in_bytes()) / vak->element_byte_size();
 322       address dest = (address)((flatArrayOop)p)->value_at_addr(index, vak->layout_helper());
 323       log_trace(valuetypes)("%s array type %s index %d element size %d offset " UINT64_FORMAT_X " at " INTPTR_FORMAT,
 324                             p->klass()->external_name(), vak->external_name(),
 325                             index, vak->element_byte_size(), (uint64_t)offset, p2i(dest));
 326     } else {
 327       log_trace(valuetypes)("%s field type %s at offset " UINT64_FORMAT_X,
 328                             p->klass()->external_name(), vk->external_name(), (uint64_t)offset);
 329     }
 330   }
 331 }
 332 
 333 // These functions allow a null base pointer with an arbitrary address.
 334 // But if the base pointer is non-null, the offset should make some sense.
 335 // That is, it should be in the range [0, MAX_OBJECT_SIZE].
 336 UNSAFE_ENTRY(jobject, Unsafe_GetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
 337   oop p = JNIHandles::resolve(obj);
 338   assert_field_offset_sane(p, offset);
 339   oop v = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
 340   return JNIHandles::make_local(THREAD, v);
 341 } UNSAFE_END
 342 
 343 UNSAFE_ENTRY(void, Unsafe_PutReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
 344   oop x = JNIHandles::resolve(x_h);
 345   oop p = JNIHandles::resolve(obj);
 346   assert_field_offset_sane(p, offset);
 347   assert(!p->is_inline_type() || p->mark().is_larval_state(), "must be an object instance or a larval inline type");
 348   HeapAccess<ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
 349 } UNSAFE_END
 350 
 351 UNSAFE_ENTRY(jlong, Unsafe_ValueHeaderSize(JNIEnv *env, jobject unsafe, jclass c)) {
 352   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(c));
 353   InlineKlass* vk = InlineKlass::cast(k);
 354   return vk->payload_offset();
 355 } UNSAFE_END
 356 
 357 UNSAFE_ENTRY(jboolean, Unsafe_IsFlatField(JNIEnv *env, jobject unsafe, jobject o)) {
 358   oop f = JNIHandles::resolve_non_null(o);
 359   Klass* k = java_lang_Class::as_Klass(java_lang_reflect_Field::clazz(f));
 360   int slot = java_lang_reflect_Field::slot(f);
 361   return InstanceKlass::cast(k)->field_is_flat(slot);
 362 } UNSAFE_END
 363 
 364 UNSAFE_ENTRY(jboolean, Unsafe_HasNullMarker(JNIEnv *env, jobject unsafe, jobject o)) {
 365   oop f = JNIHandles::resolve_non_null(o);
 366   Klass* k = java_lang_Class::as_Klass(java_lang_reflect_Field::clazz(f));
 367   int slot = java_lang_reflect_Field::slot(f);
 368   return InstanceKlass::cast(k)->field_has_null_marker(slot);
 369 } UNSAFE_END
 370 
 371 UNSAFE_ENTRY(jint, Unsafe_NullMarkerOffset(JNIEnv *env, jobject unsafe, jobject o)) {
 372   oop f = JNIHandles::resolve_non_null(o);
 373   Klass* k = java_lang_Class::as_Klass(java_lang_reflect_Field::clazz(f));
 374   int slot = java_lang_reflect_Field::slot(f);
 375   return InstanceKlass::cast(k)->null_marker_offset(slot);
 376 } UNSAFE_END
 377 
 378 UNSAFE_ENTRY(jint, Unsafe_ArrayLayout(JNIEnv *env, jobject unsafe, jclass c)) {
 379   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(c));
 380   if (!k->is_flatArray_klass()) {
 381     return LayoutKind::REFERENCE;
 382   } else {
 383     return (jint)FlatArrayKlass::cast(k)->layout_kind();
 384   }
 385 } UNSAFE_END
 386 
 387 UNSAFE_ENTRY(jint, Unsafe_FieldLayout(JNIEnv *env, jobject unsafe, jobject field)) {
 388   assert(field != nullptr, "field must not be null");
 389 
 390   oop reflected   = JNIHandles::resolve_non_null(field);
 391   oop mirror      = java_lang_reflect_Field::clazz(reflected);
 392   Klass* k        = java_lang_Class::as_Klass(mirror);
 393   int slot        = java_lang_reflect_Field::slot(reflected);
 394   int modifiers   = java_lang_reflect_Field::modifiers(reflected);
 395 
 396   if ((modifiers & JVM_ACC_STATIC) != 0) {
 397     return (jint)LayoutKind::REFERENCE; // static fields are never flat
 398   } else {
 399     InstanceKlass* ik = InstanceKlass::cast(k);
 400     if (ik->field_is_flat(slot)) {
 401       return (jint)ik->inline_layout_info(slot).kind();
 402     } else {
 403       return (jint)LayoutKind::REFERENCE;
 404     }
 405   }
 406 } UNSAFE_END
 407 
 408 UNSAFE_ENTRY(jboolean, Unsafe_IsFlatArray(JNIEnv *env, jobject unsafe, jclass c)) {
 409   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(c));
 410   return k->is_flatArray_klass();
 411 } UNSAFE_END
 412 
 413 UNSAFE_ENTRY(jobject, Unsafe_GetValue(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jclass vc)) {
 414   oop base = JNIHandles::resolve(obj);
 415   if (base == nullptr) {
 416     THROW_NULL(vmSymbols::java_lang_NullPointerException());
 417   }
 418   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(vc));
 419   InlineKlass* vk = InlineKlass::cast(k);
 420   assert_and_log_unsafe_value_access(base, offset, vk);
 421   LayoutKind lk = LayoutKind::UNKNOWN;
 422   if (base->is_array()) {
 423     FlatArrayKlass* fak = FlatArrayKlass::cast(base->klass());
 424     lk = fak->layout_kind();
 425   } else {
 426     fieldDescriptor fd;
 427     InstanceKlass::cast(base->klass())->find_field_from_offset(offset, false, &fd);
 428     lk = fd.field_holder()->inline_layout_info(fd.index()).kind();
 429   }
 430   Handle base_h(THREAD, base);
 431   oop v = vk->read_payload_from_addr(base_h(), offset, lk, CHECK_NULL);
 432   return JNIHandles::make_local(THREAD, v);
 433 } UNSAFE_END
 434 
 435 UNSAFE_ENTRY(jobject, Unsafe_GetFlatValue(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint layoutKind, jclass vc)) {
 436   assert(layoutKind != LayoutKind::REFERENCE, "This method handles only flat layouts");
 437   oop base = JNIHandles::resolve(obj);
 438   if (base == nullptr) {
 439     THROW_NULL(vmSymbols::java_lang_NullPointerException());
 440   }
 441   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(vc));
 442   InlineKlass* vk = InlineKlass::cast(k);
 443   assert_and_log_unsafe_value_access(base, offset, vk);
 444   LayoutKind lk = (LayoutKind)layoutKind;
 445   Handle base_h(THREAD, base);
 446   oop v = vk->read_payload_from_addr(base_h(), offset, lk, CHECK_NULL);
 447   return JNIHandles::make_local(THREAD, v);
 448 } UNSAFE_END
 449 
 450 UNSAFE_ENTRY(void, Unsafe_PutValue(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jclass vc, jobject value)) {
 451   oop base = JNIHandles::resolve(obj);
 452   if (base == nullptr) {
 453     THROW(vmSymbols::java_lang_NullPointerException());
 454   }
 455   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(vc));
 456   InlineKlass* vk = InlineKlass::cast(k);
 457   assert(!base->is_inline_type() || base->mark().is_larval_state(), "must be an object instance or a larval inline type");
 458   assert_and_log_unsafe_value_access(base, offset, vk);
 459   LayoutKind lk = LayoutKind::UNKNOWN;
 460   if (base->is_array()) {
 461     FlatArrayKlass* fak = FlatArrayKlass::cast(base->klass());
 462     lk = fak->layout_kind();
 463   } else {
 464     fieldDescriptor fd;
 465     InstanceKlass::cast(base->klass())->find_field_from_offset(offset, false, &fd);
 466     lk = fd.field_holder()->inline_layout_info(fd.index()).kind();
 467   }
 468   oop v = JNIHandles::resolve(value);
 469   vk->write_value_to_addr(v, ((char*)(oopDesc*)base) + offset, lk, true, CHECK);
 470 } UNSAFE_END
 471 
 472 UNSAFE_ENTRY(void, Unsafe_PutFlatValue(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint layoutKind, jclass vc, jobject value)) {
 473   assert(layoutKind != LayoutKind::REFERENCE, "This method handles only flat layouts");
 474   oop base = JNIHandles::resolve(obj);
 475   if (base == nullptr) {
 476     THROW(vmSymbols::java_lang_NullPointerException());
 477   }
 478   Klass* k = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(vc));
 479   InlineKlass* vk = InlineKlass::cast(k);
 480   assert(!base->is_inline_type() || base->mark().is_larval_state(), "must be an object instance or a larval inline type");
 481   assert_and_log_unsafe_value_access(base, offset, vk);
 482   LayoutKind lk = (LayoutKind)layoutKind;
 483   oop v = JNIHandles::resolve(value);
 484   vk->write_value_to_addr(v, ((char*)(oopDesc*)base) + offset, lk, true, CHECK);
 485 } UNSAFE_END
 486 
 487 UNSAFE_ENTRY(jobject, Unsafe_MakePrivateBuffer(JNIEnv *env, jobject unsafe, jobject value)) {
 488   oop v = JNIHandles::resolve_non_null(value);
 489   assert(v->is_inline_type(), "must be an inline type instance");
 490   Handle vh(THREAD, v);
 491   InlineKlass* vk = InlineKlass::cast(v->klass());
 492   instanceOop new_value = vk->allocate_instance_buffer(CHECK_NULL);
 493   vk->copy_payload_to_addr(vk->payload_addr(vh()), vk->payload_addr(new_value), LayoutKind::BUFFERED, false);
 494   markWord mark = new_value->mark();
 495   new_value->set_mark(mark.enter_larval_state());
 496   return JNIHandles::make_local(THREAD, new_value);
 497 } UNSAFE_END
 498 
 499 UNSAFE_ENTRY(jobject, Unsafe_FinishPrivateBuffer(JNIEnv *env, jobject unsafe, jobject value)) {
 500   oop v = JNIHandles::resolve(value);
 501   assert(v->mark().is_larval_state(), "must be a larval value");
 502   markWord mark = v->mark();
 503   v->set_mark(mark.exit_larval_state());
 504   return JNIHandles::make_local(THREAD, v);
 505 } UNSAFE_END
 506 
 507 UNSAFE_ENTRY(jobject, Unsafe_GetReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
 508   oop p = JNIHandles::resolve(obj);
 509   assert_field_offset_sane(p, offset);
 510   oop v = HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
 511   return JNIHandles::make_local(THREAD, v);
 512 } UNSAFE_END
 513 
 514 UNSAFE_ENTRY(void, Unsafe_PutReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
 515   oop x = JNIHandles::resolve(x_h);
 516   oop p = JNIHandles::resolve(obj);
 517   assert_field_offset_sane(p, offset);
 518   HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
 519 } UNSAFE_END
 520 
 521 UNSAFE_ENTRY(jobject, Unsafe_GetUncompressedObject(JNIEnv *env, jobject unsafe, jlong addr)) {
 522   oop v = *(oop*) (address) addr;
 523   return JNIHandles::make_local(THREAD, v);
 524 } UNSAFE_END
 525 
 526 #define DEFINE_GETSETOOP(java_type, Type) \
 527  \
 528 UNSAFE_ENTRY_SCOPED(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
 529   return MemoryAccess<java_type>(thread, obj, offset).get(); \
 530 } UNSAFE_END \
 531  \
 532 UNSAFE_ENTRY_SCOPED(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
 533   MemoryAccess<java_type>(thread, obj, offset).put(x); \
 534 } UNSAFE_END \
 535  \
 536 // END DEFINE_GETSETOOP.
 537 
 538 DEFINE_GETSETOOP(jboolean, Boolean)
 539 DEFINE_GETSETOOP(jbyte, Byte)
 540 DEFINE_GETSETOOP(jshort, Short);
 541 DEFINE_GETSETOOP(jchar, Char);
 542 DEFINE_GETSETOOP(jint, Int);
 543 DEFINE_GETSETOOP(jlong, Long);
 544 DEFINE_GETSETOOP(jfloat, Float);
 545 DEFINE_GETSETOOP(jdouble, Double);
 546 
 547 #undef DEFINE_GETSETOOP
 548 
 549 #define DEFINE_GETSETOOP_VOLATILE(java_type, Type) \
 550  \
 551 UNSAFE_ENTRY_SCOPED(java_type, Unsafe_Get##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
 552   return MemoryAccess<java_type>(thread, obj, offset).get_volatile(); \
 553 } UNSAFE_END \
 554  \
 555 UNSAFE_ENTRY_SCOPED(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
 556   MemoryAccess<java_type>(thread, obj, offset).put_volatile(x); \
 557 } UNSAFE_END \
 558  \
 559 // END DEFINE_GETSETOOP_VOLATILE.
 560 
 561 DEFINE_GETSETOOP_VOLATILE(jboolean, Boolean)
 562 DEFINE_GETSETOOP_VOLATILE(jbyte, Byte)
 563 DEFINE_GETSETOOP_VOLATILE(jshort, Short);
 564 DEFINE_GETSETOOP_VOLATILE(jchar, Char);
 565 DEFINE_GETSETOOP_VOLATILE(jint, Int);
 566 DEFINE_GETSETOOP_VOLATILE(jlong, Long);
 567 DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
 568 DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
 569 
 570 #undef DEFINE_GETSETOOP_VOLATILE
 571 
 572 UNSAFE_LEAF(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe)) {
 573   OrderAccess::fence();
 574 } UNSAFE_END
 575 
 576 ////// Allocation requests
 577 
 578 UNSAFE_ENTRY(jobject, Unsafe_AllocateInstance(JNIEnv *env, jobject unsafe, jclass cls)) {
 579   JvmtiVMObjectAllocEventCollector oam;
 580   instanceOop i = InstanceKlass::allocate_instance(JNIHandles::resolve_non_null(cls), CHECK_NULL);
 581   return JNIHandles::make_local(THREAD, i);
 582 } UNSAFE_END
 583 
 584 UNSAFE_LEAF(jlong, Unsafe_AllocateMemory0(JNIEnv *env, jobject unsafe, jlong size)) {
 585   size_t sz = (size_t)size;
 586 
 587   assert(is_aligned(sz, HeapWordSize), "sz not aligned");
 588 
 589   void* x = os::malloc(sz, mtOther);
 590 
 591   return addr_to_java(x);
 592 } UNSAFE_END
 593 
 594 UNSAFE_LEAF(jlong, Unsafe_ReallocateMemory0(JNIEnv *env, jobject unsafe, jlong addr, jlong size)) {
 595   void* p = addr_from_java(addr);
 596   size_t sz = (size_t)size;
 597 
 598   assert(is_aligned(sz, HeapWordSize), "sz not aligned");
 599 
 600   void* x = os::realloc(p, sz, mtOther);
 601 
 602   return addr_to_java(x);
 603 } UNSAFE_END
 604 
 605 UNSAFE_LEAF(void, Unsafe_FreeMemory0(JNIEnv *env, jobject unsafe, jlong addr)) {
 606   void* p = addr_from_java(addr);
 607 
 608   os::free(p);
 609 } UNSAFE_END
 610 
 611 UNSAFE_ENTRY_SCOPED(void, Unsafe_SetMemory0(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong size, jbyte value)) {
 612   size_t sz = (size_t)size;
 613 
 614   oop base = JNIHandles::resolve(obj);
 615   void* p = index_oop_from_field_offset_long(base, offset);
 616 
 617   {
 618     GuardUnsafeAccess guard(thread);
 619     if (StubRoutines::unsafe_setmemory() != nullptr) {
 620       MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
 621       StubRoutines::UnsafeSetMemory_stub()(p, sz, value);
 622     } else {
 623       Copy::fill_to_memory_atomic(p, sz, value);
 624     }
 625   }
 626 } UNSAFE_END
 627 
 628 UNSAFE_ENTRY_SCOPED(void, Unsafe_CopyMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size)) {
 629   size_t sz = (size_t)size;
 630 
 631   oop srcp = JNIHandles::resolve(srcObj);
 632   oop dstp = JNIHandles::resolve(dstObj);
 633 
 634   void* src = index_oop_from_field_offset_long(srcp, srcOffset);
 635   void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
 636   {
 637     GuardUnsafeAccess guard(thread);
 638     if (StubRoutines::unsafe_arraycopy() != nullptr) {
 639       MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, thread));
 640       StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
 641     } else {
 642       Copy::conjoint_memory_atomic(src, dst, sz);
 643     }
 644   }
 645 } UNSAFE_END
 646 
 647 UNSAFE_ENTRY_SCOPED(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
 648   size_t sz = (size_t)size;
 649   size_t esz = (size_t)elemSize;
 650 
 651   oop srcp = JNIHandles::resolve(srcObj);
 652   oop dstp = JNIHandles::resolve(dstObj);
 653 
 654   address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
 655   address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
 656 
 657   {
 658     GuardUnsafeAccess guard(thread);
 659     Copy::conjoint_swap(src, dst, sz, esz);
 660   }
 661 } UNSAFE_END
 662 
 663 UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
 664   assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
 665 #ifdef ASSERT
 666   if (TraceMemoryWriteback) {
 667     tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
 668   }
 669 #endif
 670 
 671   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
 672   assert(StubRoutines::data_cache_writeback() != nullptr, "sanity");
 673   (StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
 674 } UNSAFE_END
 675 
 676 static void doWriteBackSync0(bool is_pre)
 677 {
 678   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXExec, Thread::current()));
 679   assert(StubRoutines::data_cache_writeback_sync() != nullptr, "sanity");
 680   (StubRoutines::DataCacheWritebackSync_stub())(is_pre);
 681 }
 682 
 683 UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
 684   assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
 685 #ifdef ASSERT
 686   if (TraceMemoryWriteback) {
 687       tty->print_cr("Unsafe: writeback pre-sync");
 688   }
 689 #endif
 690 
 691   doWriteBackSync0(true);
 692 } UNSAFE_END
 693 
 694 UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
 695   assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
 696 #ifdef ASSERT
 697   if (TraceMemoryWriteback) {
 698     tty->print_cr("Unsafe: writeback pre-sync");
 699   }
 700 #endif
 701 
 702   doWriteBackSync0(false);
 703 } UNSAFE_END
 704 
 705 ////// Random queries
 706 
 707 static jlong find_field_offset(jclass clazz, jstring name, TRAPS) {
 708   assert(clazz != nullptr, "clazz must not be null");
 709   assert(name != nullptr, "name must not be null");
 710 
 711   ResourceMark rm(THREAD);
 712   char *utf_name = java_lang_String::as_utf8_string(JNIHandles::resolve_non_null(name));
 713 
 714   InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(clazz)));
 715 
 716   jint offset = -1;
 717   for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
 718     Symbol *name = fs.name();
 719     if (name->equals(utf_name)) {
 720       offset = fs.offset();
 721       break;
 722     }
 723   }
 724   if (offset < 0) {
 725     THROW_0(vmSymbols::java_lang_InternalError());
 726   }
 727   return field_offset_from_byte_offset(offset);
 728 }
 729 
 730 static jlong find_field_offset(jobject field, int must_be_static, TRAPS) {
 731   assert(field != nullptr, "field must not be null");
 732 
 733   oop reflected   = JNIHandles::resolve_non_null(field);
 734   oop mirror      = java_lang_reflect_Field::clazz(reflected);
 735   Klass* k        = java_lang_Class::as_Klass(mirror);
 736   int slot        = java_lang_reflect_Field::slot(reflected);
 737   int modifiers   = java_lang_reflect_Field::modifiers(reflected);
 738 
 739   if (must_be_static >= 0) {
 740     int really_is_static = ((modifiers & JVM_ACC_STATIC) != 0);
 741     if (must_be_static != really_is_static) {
 742       THROW_0(vmSymbols::java_lang_IllegalArgumentException());
 743     }
 744   }
 745 
 746   int offset = InstanceKlass::cast(k)->field_offset(slot);
 747   return field_offset_from_byte_offset(offset);
 748 }
 749 
 750 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
 751   return find_field_offset(field, 0, THREAD);
 752 } UNSAFE_END
 753 
 754 UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset1(JNIEnv *env, jobject unsafe, jclass c, jstring name)) {
 755   return find_field_offset(c, name, THREAD);
 756 } UNSAFE_END
 757 
 758 UNSAFE_ENTRY(jlong, Unsafe_StaticFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
 759   return find_field_offset(field, 1, THREAD);
 760 } UNSAFE_END
 761 
 762 UNSAFE_ENTRY(jobject, Unsafe_StaticFieldBase0(JNIEnv *env, jobject unsafe, jobject field)) {
 763   assert(field != nullptr, "field must not be null");
 764 
 765   // Note:  In this VM implementation, a field address is always a short
 766   // offset from the base of a klass metaobject.  Thus, the full dynamic
 767   // range of the return type is never used.  However, some implementations
 768   // might put the static field inside an array shared by many classes,
 769   // or even at a fixed address, in which case the address could be quite
 770   // large.  In that last case, this function would return null, since
 771   // the address would operate alone, without any base pointer.
 772 
 773   oop reflected   = JNIHandles::resolve_non_null(field);
 774   oop mirror      = java_lang_reflect_Field::clazz(reflected);
 775   int modifiers   = java_lang_reflect_Field::modifiers(reflected);
 776 
 777   if ((modifiers & JVM_ACC_STATIC) == 0) {
 778     THROW_NULL(vmSymbols::java_lang_IllegalArgumentException());
 779   }
 780 
 781   return JNIHandles::make_local(THREAD, mirror);
 782 } UNSAFE_END
 783 
 784 UNSAFE_ENTRY(void, Unsafe_EnsureClassInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
 785   assert(clazz != nullptr, "clazz must not be null");
 786 
 787   oop mirror = JNIHandles::resolve_non_null(clazz);
 788 
 789   Klass* klass = java_lang_Class::as_Klass(mirror);
 790   if (klass != nullptr && klass->should_be_initialized()) {
 791     InstanceKlass* k = InstanceKlass::cast(klass);
 792     k->initialize(CHECK);
 793   }
 794 }
 795 UNSAFE_END
 796 
 797 UNSAFE_ENTRY(jboolean, Unsafe_ShouldBeInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
 798   assert(clazz != nullptr, "clazz must not be null");
 799 
 800   oop mirror = JNIHandles::resolve_non_null(clazz);
 801   Klass* klass = java_lang_Class::as_Klass(mirror);
 802 
 803   if (klass != nullptr && klass->should_be_initialized()) {
 804     return true;
 805   }
 806 
 807   return false;
 808 }
 809 UNSAFE_END
 810 
 811 static void getBaseAndScale(int& base, int& scale, jclass clazz, TRAPS) {
 812   assert(clazz != nullptr, "clazz must not be null");
 813 
 814   oop mirror = JNIHandles::resolve_non_null(clazz);
 815   Klass* k = java_lang_Class::as_Klass(mirror);
 816 
 817   if (k == nullptr || !k->is_array_klass()) {
 818     THROW(vmSymbols::java_lang_InvalidClassException());
 819   } else if (k->is_objArray_klass()) {
 820     base  = arrayOopDesc::base_offset_in_bytes(T_OBJECT);
 821     scale = heapOopSize;
 822   } else if (k->is_typeArray_klass()) {
 823     TypeArrayKlass* tak = TypeArrayKlass::cast(k);
 824     base  = tak->array_header_in_bytes();
 825     assert(base == arrayOopDesc::base_offset_in_bytes(tak->element_type()), "array_header_size semantics ok");
 826     scale = (1 << tak->log2_element_size());
 827   } else if (k->is_flatArray_klass()) {
 828     FlatArrayKlass* vak = FlatArrayKlass::cast(k);
 829     InlineKlass* vklass = vak->element_klass();
 830     base = vak->array_header_in_bytes();
 831     scale = vak->element_byte_size();
 832   } else {
 833     ShouldNotReachHere();
 834   }
 835 }
 836 
 837 UNSAFE_ENTRY(jint, Unsafe_ArrayBaseOffset0(JNIEnv *env, jobject unsafe, jclass clazz)) {
 838   int base = 0, scale = 0;
 839   getBaseAndScale(base, scale, clazz, CHECK_0);
 840 
 841   return field_offset_from_byte_offset(base);
 842 } UNSAFE_END
 843 
 844 
 845 UNSAFE_ENTRY(jint, Unsafe_ArrayIndexScale0(JNIEnv *env, jobject unsafe, jclass clazz)) {
 846   int base = 0, scale = 0;
 847   getBaseAndScale(base, scale, clazz, CHECK_0);
 848 
 849   // This VM packs both fields and array elements down to the byte.
 850   // But watch out:  If this changes, so that array references for
 851   // a given primitive type (say, T_BOOLEAN) use different memory units
 852   // than fields, this method MUST return zero for such arrays.
 853   // For example, the VM used to store sub-word sized fields in full
 854   // words in the object layout, so that accessors like getByte(Object,int)
 855   // did not really do what one might expect for arrays.  Therefore,
 856   // this function used to report a zero scale factor, so that the user
 857   // would know not to attempt to access sub-word array elements.
 858   // // Code for unpacked fields:
 859   // if (scale < wordSize)  return 0;
 860 
 861   // The following allows for a pretty general fieldOffset cookie scheme,
 862   // but requires it to be linear in byte offset.
 863   return field_offset_from_byte_offset(scale) - field_offset_from_byte_offset(0);
 864 } UNSAFE_END
 865 
 866 
 867 UNSAFE_ENTRY(jlong, Unsafe_GetObjectSize0(JNIEnv* env, jobject o, jobject obj))
 868   oop p = JNIHandles::resolve(obj);
 869   return p->size() * HeapWordSize;
 870 UNSAFE_END
 871 
 872 
 873 static inline void throw_new(JNIEnv *env, const char *ename) {
 874   jclass cls = env->FindClass(ename);
 875   if (env->ExceptionCheck()) {
 876     env->ExceptionClear();
 877     tty->print_cr("Unsafe: cannot throw %s because FindClass has failed", ename);
 878     return;
 879   }
 880 
 881   env->ThrowNew(cls, nullptr);
 882 }
 883 
 884 static jclass Unsafe_DefineClass_impl(JNIEnv *env, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd) {
 885   // Code lifted from JDK 1.3 ClassLoader.c
 886 
 887   jbyte *body;
 888   char *utfName = nullptr;
 889   jclass result = nullptr;
 890   char buf[128];
 891 
 892   assert(data != nullptr, "Class bytes must not be null");
 893   assert(length >= 0, "length must not be negative: %d", length);
 894 
 895   if (UsePerfData) {
 896     ClassLoader::unsafe_defineClassCallCounter()->inc();
 897   }
 898 
 899   body = NEW_C_HEAP_ARRAY_RETURN_NULL(jbyte, length, mtInternal);
 900   if (body == nullptr) {
 901     throw_new(env, "java/lang/OutOfMemoryError");
 902     return nullptr;
 903   }
 904 
 905   env->GetByteArrayRegion(data, offset, length, body);
 906   if (env->ExceptionCheck()) {
 907     goto free_body;
 908   }
 909 
 910   if (name != nullptr) {
 911     uint len = env->GetStringUTFLength(name);
 912     int unicode_len = env->GetStringLength(name);
 913 
 914     if (len >= sizeof(buf)) {
 915       utfName = NEW_C_HEAP_ARRAY_RETURN_NULL(char, len + 1, mtInternal);
 916       if (utfName == nullptr) {
 917         throw_new(env, "java/lang/OutOfMemoryError");
 918         goto free_body;
 919       }
 920     } else {
 921       utfName = buf;
 922     }
 923 
 924     env->GetStringUTFRegion(name, 0, unicode_len, utfName);
 925 
 926     for (uint i = 0; i < len; i++) {
 927       if (utfName[i] == '.')   utfName[i] = '/';
 928     }
 929   }
 930 
 931   result = JVM_DefineClass(env, utfName, loader, body, length, pd);
 932 
 933   if (utfName && utfName != buf) {
 934     FREE_C_HEAP_ARRAY(char, utfName);
 935   }
 936 
 937  free_body:
 938   FREE_C_HEAP_ARRAY(jbyte, body);
 939   return result;
 940 }
 941 
 942 
 943 UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd)) {
 944   ThreadToNativeFromVM ttnfv(thread);
 945 
 946   return Unsafe_DefineClass_impl(env, name, data, offset, length, loader, pd);
 947 } UNSAFE_END
 948 
 949 
 950 UNSAFE_ENTRY(void, Unsafe_ThrowException(JNIEnv *env, jobject unsafe, jthrowable thr)) {
 951   ThreadToNativeFromVM ttnfv(thread);
 952   env->Throw(thr);
 953 } UNSAFE_END
 954 
 955 // JSR166 ------------------------------------------------------------------
 956 
 957 UNSAFE_ENTRY(jobject, Unsafe_CompareAndExchangeReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
 958   oop x = JNIHandles::resolve(x_h);
 959   oop e = JNIHandles::resolve(e_h);
 960   oop p = JNIHandles::resolve(obj);
 961   assert_field_offset_sane(p, offset);
 962   oop res = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
 963   return JNIHandles::make_local(THREAD, res);
 964 } UNSAFE_END
 965 
 966 UNSAFE_ENTRY_SCOPED(jint, Unsafe_CompareAndExchangeInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
 967   oop p = JNIHandles::resolve(obj);
 968   volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
 969   return Atomic::cmpxchg(addr, e, x);
 970 } UNSAFE_END
 971 
 972 UNSAFE_ENTRY_SCOPED(jlong, Unsafe_CompareAndExchangeLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
 973   oop p = JNIHandles::resolve(obj);
 974   volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
 975   return Atomic::cmpxchg(addr, e, x);
 976 } UNSAFE_END
 977 
 978 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
 979   oop x = JNIHandles::resolve(x_h);
 980   oop e = JNIHandles::resolve(e_h);
 981   oop p = JNIHandles::resolve(obj);
 982   assert_field_offset_sane(p, offset);
 983   oop ret = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
 984   return ret == e;
 985 } UNSAFE_END
 986 
 987 UNSAFE_ENTRY_SCOPED(jboolean, Unsafe_CompareAndSetInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
 988   oop p = JNIHandles::resolve(obj);
 989   volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
 990   return Atomic::cmpxchg(addr, e, x) == e;
 991 } UNSAFE_END
 992 
 993 UNSAFE_ENTRY_SCOPED(jboolean, Unsafe_CompareAndSetLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
 994   oop p = JNIHandles::resolve(obj);
 995   volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
 996   return Atomic::cmpxchg(addr, e, x) == e;
 997 } UNSAFE_END
 998 
 999 static void post_thread_park_event(EventThreadPark* event, const oop obj, jlong timeout_nanos, jlong until_epoch_millis) {
1000   assert(event != nullptr, "invariant");
1001   event->set_parkedClass((obj != nullptr) ? obj->klass() : nullptr);
1002   event->set_timeout(timeout_nanos);
1003   event->set_until(until_epoch_millis);
1004   event->set_address((obj != nullptr) ? (u8)cast_from_oop<uintptr_t>(obj) : 0);
1005   event->commit();
1006 }
1007 
1008 UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time)) {
1009   HOTSPOT_THREAD_PARK_BEGIN((uintptr_t) thread->parker(), (int) isAbsolute, time);
1010   EventThreadPark event;
1011 
1012   JavaThreadParkedState jtps(thread, time != 0);
1013   thread->parker()->park(isAbsolute != 0, time);
1014   if (event.should_commit()) {
1015     const oop obj = thread->current_park_blocker();
1016     if (time == 0) {
1017       post_thread_park_event(&event, obj, min_jlong, min_jlong);
1018     } else {
1019       if (isAbsolute != 0) {
1020         post_thread_park_event(&event, obj, min_jlong, time);
1021       } else {
1022         post_thread_park_event(&event, obj, time, min_jlong);
1023       }
1024     }
1025   }
1026   HOTSPOT_THREAD_PARK_END((uintptr_t) thread->parker());
1027 } UNSAFE_END
1028 
1029 UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread)) {
1030   if (jthread != nullptr) {
1031     oop thread_oop = JNIHandles::resolve_non_null(jthread);
1032     // Get the JavaThread* stored in the java.lang.Thread object _before_
1033     // the embedded ThreadsListHandle is constructed so we know if the
1034     // early life stage of the JavaThread* is protected. We use acquire
1035     // here to ensure that if we see a non-nullptr value, then we also
1036     // see the main ThreadsList updates from the JavaThread* being added.
1037     FastThreadsListHandle ftlh(thread_oop, java_lang_Thread::thread_acquire(thread_oop));
1038     JavaThread* thr = ftlh.protected_java_thread();
1039     if (thr != nullptr) {
1040       // The still live JavaThread* is protected by the FastThreadsListHandle
1041       // so it is safe to access.
1042       Parker* p = thr->parker();
1043       HOTSPOT_THREAD_UNPARK((uintptr_t) p);
1044       p->unpark();
1045     }
1046   } // FastThreadsListHandle is destroyed here.
1047 } UNSAFE_END
1048 
1049 UNSAFE_ENTRY(jint, Unsafe_GetLoadAverage0(JNIEnv *env, jobject unsafe, jdoubleArray loadavg, jint nelem)) {
1050   const int max_nelem = 3;
1051   double la[max_nelem];
1052   jint ret;
1053 
1054   typeArrayOop a = typeArrayOop(JNIHandles::resolve_non_null(loadavg));
1055   assert(a->is_typeArray(), "must be type array");
1056 
1057   ret = os::loadavg(la, nelem);
1058   if (ret == -1) {
1059     return -1;
1060   }
1061 
1062   // if successful, ret is the number of samples actually retrieved.
1063   assert(ret >= 0 && ret <= max_nelem, "Unexpected loadavg return value");
1064   switch(ret) {
1065     case 3: a->double_at_put(2, (jdouble)la[2]); // fall through
1066     case 2: a->double_at_put(1, (jdouble)la[1]); // fall through
1067     case 1: a->double_at_put(0, (jdouble)la[0]); break;
1068   }
1069 
1070   return ret;
1071 } UNSAFE_END
1072 
1073 
1074 /// JVM_RegisterUnsafeMethods
1075 
1076 #define ADR "J"
1077 
1078 #define LANG "Ljava/lang/"
1079 
1080 #define OBJ LANG "Object;"
1081 #define CLS LANG "Class;"
1082 #define FLD LANG "reflect/Field;"
1083 #define THR LANG "Throwable;"
1084 
1085 #define DC_Args  LANG "String;[BII" LANG "ClassLoader;" "Ljava/security/ProtectionDomain;"
1086 #define DAC_Args CLS "[B[" OBJ
1087 
1088 #define CC (char*)  /*cast a literal from (const char*)*/
1089 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
1090 
1091 #define DECLARE_GETPUTOOP(Type, Desc) \
1092     {CC "get"  #Type,      CC "(" OBJ "J)" #Desc,                 FN_PTR(Unsafe_Get##Type)}, \
1093     {CC "put"  #Type,      CC "(" OBJ "J" #Desc ")V",             FN_PTR(Unsafe_Put##Type)}, \
1094     {CC "get"  #Type "Volatile",      CC "(" OBJ "J)" #Desc,      FN_PTR(Unsafe_Get##Type##Volatile)}, \
1095     {CC "put"  #Type "Volatile",      CC "(" OBJ "J" #Desc ")V",  FN_PTR(Unsafe_Put##Type##Volatile)}
1096 
1097 
1098 static JNINativeMethod jdk_internal_misc_Unsafe_methods[] = {
1099     {CC "getReference",         CC "(" OBJ "J)" OBJ "",   FN_PTR(Unsafe_GetReference)},
1100     {CC "putReference",         CC "(" OBJ "J" OBJ ")V",  FN_PTR(Unsafe_PutReference)},
1101     {CC "getReferenceVolatile", CC "(" OBJ "J)" OBJ,      FN_PTR(Unsafe_GetReferenceVolatile)},
1102     {CC "putReferenceVolatile", CC "(" OBJ "J" OBJ ")V",  FN_PTR(Unsafe_PutReferenceVolatile)},
1103 
1104     {CC "isFlatArray",          CC "(" CLS ")Z",          FN_PTR(Unsafe_IsFlatArray)},
1105     {CC "isFlatField0",         CC "(" OBJ ")Z",          FN_PTR(Unsafe_IsFlatField)},
1106     {CC "hasNullMarker0",       CC "(" OBJ ")Z",          FN_PTR(Unsafe_HasNullMarker)},
1107     {CC "nullMarkerOffset0",    CC "(" OBJ ")I",          FN_PTR(Unsafe_NullMarkerOffset)},
1108     {CC "arrayLayout0",         CC "(" OBJ ")I",          FN_PTR(Unsafe_ArrayLayout)},
1109     {CC "fieldLayout0",         CC "(" OBJ ")I",          FN_PTR(Unsafe_FieldLayout)},
1110     {CC "getValue",             CC "(" OBJ "J" CLS ")" OBJ, FN_PTR(Unsafe_GetValue)},
1111     {CC "getFlatValue",         CC "(" OBJ "JI" CLS ")" OBJ, FN_PTR(Unsafe_GetFlatValue)},
1112     {CC "putValue",             CC "(" OBJ "J" CLS OBJ ")V", FN_PTR(Unsafe_PutValue)},
1113     {CC "putFlatValue",         CC "(" OBJ "JI" CLS OBJ ")V", FN_PTR(Unsafe_PutFlatValue)},
1114     {CC "makePrivateBuffer",     CC "(" OBJ ")" OBJ,      FN_PTR(Unsafe_MakePrivateBuffer)},
1115     {CC "finishPrivateBuffer",   CC "(" OBJ ")" OBJ,      FN_PTR(Unsafe_FinishPrivateBuffer)},
1116     {CC "valueHeaderSize",       CC "(" CLS ")J",         FN_PTR(Unsafe_ValueHeaderSize)},
1117 
1118     {CC "getUncompressedObject", CC "(" ADR ")" OBJ,  FN_PTR(Unsafe_GetUncompressedObject)},
1119 
1120     DECLARE_GETPUTOOP(Boolean, Z),
1121     DECLARE_GETPUTOOP(Byte, B),
1122     DECLARE_GETPUTOOP(Short, S),
1123     DECLARE_GETPUTOOP(Char, C),
1124     DECLARE_GETPUTOOP(Int, I),
1125     DECLARE_GETPUTOOP(Long, J),
1126     DECLARE_GETPUTOOP(Float, F),
1127     DECLARE_GETPUTOOP(Double, D),
1128 
1129     {CC "allocateMemory0",    CC "(J)" ADR,              FN_PTR(Unsafe_AllocateMemory0)},
1130     {CC "reallocateMemory0",  CC "(" ADR "J)" ADR,       FN_PTR(Unsafe_ReallocateMemory0)},
1131     {CC "freeMemory0",        CC "(" ADR ")V",           FN_PTR(Unsafe_FreeMemory0)},
1132 
1133     {CC "objectFieldOffset0", CC "(" FLD ")J",           FN_PTR(Unsafe_ObjectFieldOffset0)},
1134     {CC "objectFieldOffset1", CC "(" CLS LANG "String;)J", FN_PTR(Unsafe_ObjectFieldOffset1)},
1135     {CC "staticFieldOffset0", CC "(" FLD ")J",           FN_PTR(Unsafe_StaticFieldOffset0)},
1136     {CC "staticFieldBase0",   CC "(" FLD ")" OBJ,        FN_PTR(Unsafe_StaticFieldBase0)},
1137     {CC "ensureClassInitialized0", CC "(" CLS ")V",      FN_PTR(Unsafe_EnsureClassInitialized0)},
1138     {CC "arrayBaseOffset0",   CC "(" CLS ")I",           FN_PTR(Unsafe_ArrayBaseOffset0)},
1139     {CC "arrayIndexScale0",   CC "(" CLS ")I",           FN_PTR(Unsafe_ArrayIndexScale0)},
1140     {CC "getObjectSize0",     CC "(Ljava/lang/Object;)J", FN_PTR(Unsafe_GetObjectSize0)},
1141 
1142     {CC "defineClass0",       CC "(" DC_Args ")" CLS,    FN_PTR(Unsafe_DefineClass0)},
1143     {CC "allocateInstance",   CC "(" CLS ")" OBJ,        FN_PTR(Unsafe_AllocateInstance)},
1144     {CC "throwException",     CC "(" THR ")V",           FN_PTR(Unsafe_ThrowException)},
1145     {CC "compareAndSetReference",CC "(" OBJ "J" OBJ "" OBJ ")Z", FN_PTR(Unsafe_CompareAndSetReference)},
1146     {CC "compareAndSetInt",   CC "(" OBJ "J""I""I"")Z",  FN_PTR(Unsafe_CompareAndSetInt)},
1147     {CC "compareAndSetLong",  CC "(" OBJ "J""J""J"")Z",  FN_PTR(Unsafe_CompareAndSetLong)},
1148     {CC "compareAndExchangeReference", CC "(" OBJ "J" OBJ "" OBJ ")" OBJ, FN_PTR(Unsafe_CompareAndExchangeReference)},
1149     {CC "compareAndExchangeInt",  CC "(" OBJ "J""I""I"")I", FN_PTR(Unsafe_CompareAndExchangeInt)},
1150     {CC "compareAndExchangeLong", CC "(" OBJ "J""J""J"")J", FN_PTR(Unsafe_CompareAndExchangeLong)},
1151 
1152     {CC "park",               CC "(ZJ)V",                FN_PTR(Unsafe_Park)},
1153     {CC "unpark",             CC "(" OBJ ")V",           FN_PTR(Unsafe_Unpark)},
1154 
1155     {CC "getLoadAverage0",    CC "([DI)I",               FN_PTR(Unsafe_GetLoadAverage0)},
1156 
1157     {CC "copyMemory0",        CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory0)},
1158     {CC "copySwapMemory0",    CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
1159     {CC "writeback0",         CC "(" "J" ")V",           FN_PTR(Unsafe_WriteBack0)},
1160     {CC "writebackPreSync0",  CC "()V",                  FN_PTR(Unsafe_WriteBackPreSync0)},
1161     {CC "writebackPostSync0", CC "()V",                  FN_PTR(Unsafe_WriteBackPostSync0)},
1162     {CC "setMemory0",         CC "(" OBJ "JJB)V",        FN_PTR(Unsafe_SetMemory0)},
1163 
1164     {CC "shouldBeInitialized0", CC "(" CLS ")Z",         FN_PTR(Unsafe_ShouldBeInitialized0)},
1165 
1166     {CC "fullFence",          CC "()V",                  FN_PTR(Unsafe_FullFence)},
1167 };
1168 
1169 #undef CC
1170 #undef FN_PTR
1171 
1172 #undef ADR
1173 #undef LANG
1174 #undef OBJ
1175 #undef CLS
1176 #undef FLD
1177 #undef THR
1178 #undef DC_Args
1179 #undef DAC_Args
1180 
1181 #undef DECLARE_GETPUTOOP
1182 
1183 
1184 // This function is exported, used by NativeLookup.
1185 // The Unsafe_xxx functions above are called only from the interpreter.
1186 // The optimizer looks at names and signatures to recognize
1187 // individual functions.
1188 
1189 JVM_ENTRY(void, JVM_RegisterJDKInternalMiscUnsafeMethods(JNIEnv *env, jclass unsafeclass)) {
1190   ThreadToNativeFromVM ttnfv(thread);
1191 
1192   int ok = env->RegisterNatives(unsafeclass, jdk_internal_misc_Unsafe_methods, sizeof(jdk_internal_misc_Unsafe_methods)/sizeof(JNINativeMethod));
1193   guarantee(ok == 0, "register jdk.internal.misc.Unsafe natives");
1194 } JVM_END