1 /* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 import sun.misc.Unsafe; 18 import java.lang.reflect.Field; 19 20 public class Main { 21 22 long instanceField; 23 static long myLongField1; 24 static long myLongField2; 25 26 public static void main(String[] args) throws Exception { 27 Unsafe unsafe = getUnsafe(); 28 Main f = new Main(); 29 long offset = unsafe.objectFieldOffset(Main.class.getDeclaredField("instanceField")); 30 getUnsafe(); // spill offset 31 long a = myLongField1; 32 // We used the hinted register for the low part of b, which is EBX, as requested 33 // by the intrinsic below. Allocating EBX for the low part, would put ESP as the high 34 // part, and we did not check that ESP was blocked. 35 long b = myLongField2; 36 unsafe.compareAndSwapLong(f, offset, a, b); 37 } 38 39 40 private static Unsafe getUnsafe() throws Exception { 41 Field f = Unsafe.class.getDeclaredField("theUnsafe"); 42 f.setAccessible(true); 43 return (Unsafe) f.get(null); 44 } 45 } 46
