1 /*
 2  * Copyright (c) 2016, 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 import java.lang.reflect.Field;
25 import java.lang.reflect.Method;
26 import java.util.List;
27 import java.util.Set;
28 import java.util.stream.Collectors;
29 import java.lang.StackWalker.StackFrame;
30 
31 public class LocalLongHelper {
32     static StackWalker sw;
33     static Method longValue;
34     static Method getLocals;
35     static Class<?> primitiveValueClass;
36     static Method primitiveSize;
37     static Method getMethodType;
38     static Field memberName;
39     static Field offset;
40 
41     public static void main(String[] args) throws Throwable {
42         setupReflectionStatics();
43         new LocalLongHelper().longArg(0xC0FFEE, 0x1234567890ABCDEFL);
44     }
45 
46     // locals[2] contains the unused slot of the long argument.
47     public long longArg(int i, long l) throws Throwable {
48         List<StackFrame> frames = sw.walk(s -> s.collect(Collectors.toList()));
49         Object[] locals = (Object[]) getLocals.invoke(frames.get(0));
50 
51         if (8 == (int) primitiveSize.invoke(locals[2])) { // Only test 64-bit
52             long locals_2 = (long) longValue.invoke(locals[2]);
53             if (locals_2 != 0){
54                 throw new RuntimeException("Expected locals_2 == 0");
55             }
56         }
57         return l; // Don't want l to become a dead var
58     }
59 
60     private static void setupReflectionStatics() throws Throwable {
61         Class<?> liveStackFrameClass = Class.forName("java.lang.LiveStackFrame");
62         primitiveValueClass = Class.forName("java.lang.LiveStackFrame$PrimitiveSlot");
63 
64         getLocals = liveStackFrameClass.getDeclaredMethod("getLocals");
65         getLocals.setAccessible(true);
66 
67         longValue = primitiveValueClass.getDeclaredMethod("longValue");
68         longValue.setAccessible(true);
69 
70         Class<?> stackFrameInfoClass = Class.forName("java.lang.StackFrameInfo");
71         memberName = stackFrameInfoClass.getDeclaredField("memberName");
72         memberName.setAccessible(true);
73         offset = stackFrameInfoClass.getDeclaredField("bci");
74         offset.setAccessible(true);
75         getMethodType = Class.forName("java.lang.invoke.MemberName").getDeclaredMethod("getMethodType");
76         getMethodType.setAccessible(true);
77 
78         Class<?> extendedOptionClass = Class.forName("java.lang.StackWalker$ExtendedOption");
79         Method ewsNI = StackWalker.class.getDeclaredMethod("newInstance", Set.class, extendedOptionClass, jdk.internal.vm.ContinuationScope.class);
80         ewsNI.setAccessible(true);
81         Field f = extendedOptionClass.getDeclaredField("LOCALS_AND_OPERANDS");
82         f.setAccessible(true);
83         Object localsAndOperandsOption = f.get(null);
84 
85         primitiveSize = primitiveValueClass.getDeclaredMethod("size");
86         primitiveSize.setAccessible(true);
87         sw = (StackWalker) ewsNI.invoke(null, java.util.Collections.emptySet(), localsAndOperandsOption, null);
88     }
89 }