--- a/src/hotspot/share/prims/unsafe.cpp	Thu Oct 17 20:27:44 2019 +0100
+++ b/src/hotspot/share/prims/unsafe.cpp	Thu Oct 17 20:53:35 2019 +0100
@@ -44,6 +44,7 @@
 #include "runtime/jniHandles.inline.hpp"
 #include "runtime/orderAccess.hpp"
 #include "runtime/reflection.hpp"
+#include "runtime/sharedRuntime.hpp"
 #include "runtime/thread.hpp"
 #include "runtime/threadSMR.hpp"
 #include "runtime/vm_version.hpp"
@@ -149,6 +150,25 @@
 ///// Data read/writes on the Java heap and in native (off-heap) memory
 
 /**
+ * Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
+ */
+class GuardUnsafeAccess {
+  JavaThread* _thread;
+
+public:
+  GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
+    // native/off-heap access which may raise SIGBUS if accessing
+    // memory mapped file data in a region of the file which has
+    // been truncated and is now invalid.
+    _thread->set_doing_unsafe_access(true);
+  }
+
+  ~GuardUnsafeAccess() {
+    _thread->set_doing_unsafe_access(false);
+  }
+};
+
+/**
  * Helper class for accessing memory.
  *
  * Normalizes values and wraps accesses in
@@ -189,25 +209,6 @@
     return x != 0;
   }
 
-  /**
-   * Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
-   */
-  class GuardUnsafeAccess {
-    JavaThread* _thread;
-
-  public:
-    GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
-      // native/off-heap access which may raise SIGBUS if accessing
-      // memory mapped file data in a region of the file which has
-      // been truncated and is now invalid
-      _thread->set_doing_unsafe_access(true);
-    }
-
-    ~GuardUnsafeAccess() {
-      _thread->set_doing_unsafe_access(false);
-    }
-  };
-
 public:
   MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
     : _thread(thread), _obj(JNIHandles::resolve(obj)), _offset((ptrdiff_t)offset) {
@@ -399,8 +400,14 @@
 
   void* src = index_oop_from_field_offset_long(srcp, srcOffset);
   void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
-
-  Copy::conjoint_memory_atomic(src, dst, sz);
+  {
+    GuardUnsafeAccess guard(thread);
+    if (StubRoutines::unsafe_arraycopy() != NULL) {
+      StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
+    } else {
+      Copy::conjoint_memory_atomic(src, dst, sz);
+    }
+  }
 } UNSAFE_END
 
 // This function is a leaf since if the source and destination are both in native memory
@@ -416,7 +423,11 @@
     address src = (address)srcOffset;
     address dst = (address)dstOffset;
 
-    Copy::conjoint_swap(src, dst, sz, esz);
+    {
+      JavaThread* thread = JavaThread::thread_from_jni_environment(env);
+      GuardUnsafeAccess guard(thread);
+      Copy::conjoint_swap(src, dst, sz, esz);
+    }
   } else {
     // At least one of src/dst are on heap, transition to VM to access raw pointers
 
@@ -427,11 +438,54 @@
       address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
       address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
 
-      Copy::conjoint_swap(src, dst, sz, esz);
+      {
+        GuardUnsafeAccess guard(thread);
+        Copy::conjoint_swap(src, dst, sz, esz);
+      }
     } JVM_END
   }
 } UNSAFE_END
 
+UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
+  assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
+#ifdef ASSERT
+  if (TraceMemoryWriteback) {
+    tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
+  }
+#endif
+
+  assert(StubRoutines::data_cache_writeback() != NULL, "sanity");
+  (StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
+} UNSAFE_END
+
+static void doWriteBackSync0(bool is_pre)
+{
+  assert(StubRoutines::data_cache_writeback_sync() != NULL, "sanity");
+  (StubRoutines::DataCacheWritebackSync_stub())(is_pre);
+}
+
+UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
+  assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
+#ifdef ASSERT
+  if (TraceMemoryWriteback) {
+      tty->print_cr("Unsafe: writeback pre-sync");
+  }
+#endif
+
+  doWriteBackSync0(true);
+} UNSAFE_END
+
+UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
+  assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
+#ifdef ASSERT
+  if (TraceMemoryWriteback) {
+    tty->print_cr("Unsafe: writeback pre-sync");
+  }
+#endif
+
+  doWriteBackSync0(false);
+} UNSAFE_END
+
 ////// Random queries
 
 static jlong find_field_offset(jclass clazz, jstring name, TRAPS) {
@@ -615,7 +669,7 @@
     ClassLoader::unsafe_defineClassCallCounter()->inc();
   }
 
-  body = NEW_C_HEAP_ARRAY(jbyte, length, mtInternal);
+  body = NEW_C_HEAP_ARRAY_RETURN_NULL(jbyte, length, mtInternal);
   if (body == NULL) {
     throw_new(env, "java/lang/OutOfMemoryError");
     return 0;
@@ -631,7 +685,7 @@
     int unicode_len = env->GetStringLength(name);
 
     if (len >= sizeof(buf)) {
-      utfName = NEW_C_HEAP_ARRAY(char, len + 1, mtInternal);
+      utfName = NEW_C_HEAP_ARRAY_RETURN_NULL(char, len + 1, mtInternal);
       if (utfName == NULL) {
         throw_new(env, "java/lang/OutOfMemoryError");
         goto free_body;
@@ -736,7 +790,7 @@
 
   int class_bytes_length = (int) length;
 
-  u1* class_bytes = NEW_C_HEAP_ARRAY(u1, length, mtInternal);
+  u1* class_bytes = NEW_C_HEAP_ARRAY_RETURN_NULL(u1, length, mtInternal);
   if (class_bytes == NULL) {
     THROW_0(vmSymbols::java_lang_OutOfMemoryError());
   }
@@ -821,9 +875,7 @@
   }
 
   // try/finally clause:
-  if (temp_alloc != NULL) {
-    FREE_C_HEAP_ARRAY(u1, temp_alloc);
-  }
+  FREE_C_HEAP_ARRAY(u1, temp_alloc);
 
   // The anonymous class loader data has been artificially been kept alive to
   // this point.   The mirror and any instances of this class have to keep
@@ -883,7 +935,7 @@
   oop p = JNIHandles::resolve(obj);
   assert_field_offset_sane(p, offset);
   oop ret = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(x, p, (ptrdiff_t)offset, e);
-  return oopDesc::equals(ret, e);
+  return ret == e;
 } UNSAFE_END
 
 UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
@@ -1060,6 +1112,9 @@
 
     {CC "copyMemory0",        CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory0)},
     {CC "copySwapMemory0",    CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
+    {CC "writeback0",         CC "(" "J" ")V",           FN_PTR(Unsafe_WriteBack0)},
+    {CC "writebackPreSync0",  CC "()V",                  FN_PTR(Unsafe_WriteBackPreSync0)},
+    {CC "writebackPostSync0", CC "()V",                  FN_PTR(Unsafe_WriteBackPostSync0)},
     {CC "setMemory0",         CC "(" OBJ "JJB)V",        FN_PTR(Unsafe_SetMemory0)},
 
     {CC "defineAnonymousClass0", CC "(" DAC_Args ")" CLS, FN_PTR(Unsafe_DefineAnonymousClass0)},