1 /*
2  * Copyright (c) 2012, 2018, 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
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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.
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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
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22  */
23 package vm.compiler.coverage.parentheses.share;
24 
25 import java.lang.reflect.Field;
26 import jdk.internal.org.objectweb.asm.ClassWriter;
27 import jdk.internal.org.objectweb.asm.MethodVisitor;
28 import jdk.internal.misc.Unsafe;
29 
30 import static jdk.internal.org.objectweb.asm.Opcodes.*;
31 
32 
33 import java.lang.reflect.Method;
34 import java.util.List;
35 
36 /**
37  * This class convert instructions sequence to java class file, load it to same JVM and then execute.
38  * This class uses Unsafe.defineAnonymousClass for class loading
39  */
40 public class HotspotInstructionsExecutor implements InstructionsExecutor {
41 
42     private static final Object[] NO_CP_PATCHES = new Object[0];
43 
44     private int stackSize;
45 
HotspotInstructionsExecutor(int stackSize)46     public HotspotInstructionsExecutor(int stackSize) {
47         this.stackSize = stackSize;
48     }
49 
50     @Override
execute(List<Instruction> instructions)51     public int execute(List<Instruction> instructions) throws ReflectiveOperationException {
52         Class execClass = generateClass(instructions);
53         Method execMethod = execClass.getMethod("exec");
54         return (Integer) execMethod.invoke(null);
55     }
56 
generateClass(List<Instruction> instructions)57     private Class generateClass(List<Instruction> instructions) throws ClassNotFoundException {
58         String classNameForASM = "ExecClass";
59 
60         ClassWriter cw = new ClassWriter(0);
61         cw.visit(V1_1, ACC_PUBLIC, classNameForASM, null, "java/lang/Object", null);
62 
63         // creates a MethodWriter for the 'main' method
64         MethodVisitor mw = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "exec", "()I", null, null);
65 
66         for (Instruction instruction : instructions) {
67             mw.visitInsn(instruction.opCode);
68         }
69 
70         mw.visitInsn(IRETURN);
71         mw.visitMaxs(stackSize, 2);
72         mw.visitEnd();
73 
74         return getUnsafe().defineAnonymousClass(ClassWriter.class, cw.toByteArray(), NO_CP_PATCHES);
75     }
76 
getUnsafe()77     private static Unsafe getUnsafe() {
78         return Unsafe.getUnsafe();
79     }
80 }
81