1 /*
2  * Copyright (c) 2012, 2021, 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 package vm.compiler.coverage.parentheses.share;
24 
25 import java.lang.invoke.MethodHandles;
26 import java.lang.invoke.MethodHandles.Lookup;
27 import java.lang.reflect.Field;
28 import jdk.internal.org.objectweb.asm.ClassWriter;
29 import jdk.internal.org.objectweb.asm.MethodVisitor;
30 
31 import static jdk.internal.org.objectweb.asm.Opcodes.*;
32 
33 
34 import java.lang.reflect.Method;
35 import java.util.List;
36 
37 /**
38  * This class convert instructions sequence to java class file, load it to same JVM and then execute.
39  * This class uses hidden classes for class loading
40  */
41 public class HotspotInstructionsExecutor implements InstructionsExecutor {
42 
43     private static final Object[] NO_CP_PATCHES = new Object[0];
44 
45     private int stackSize;
46 
HotspotInstructionsExecutor(int stackSize)47     public HotspotInstructionsExecutor(int stackSize) {
48         this.stackSize = stackSize;
49     }
50 
51     @Override
execute(List<Instruction> instructions)52     public int execute(List<Instruction> instructions) throws ReflectiveOperationException {
53         Class execClass = generateClass(instructions);
54         Method execMethod = execClass.getMethod("exec");
55         return (Integer) execMethod.invoke(null);
56     }
57 
generateClass(List<Instruction> instructions)58     private Class generateClass(List<Instruction> instructions) throws ReflectiveOperationException {
59         // Needs to be in the same package as the lookup class.
60         String classNameForASM = "vm/compiler/coverage/parentheses/share/ExecClass";
61 
62         ClassWriter cw = new ClassWriter(0);
63         cw.visit(V1_1, ACC_PUBLIC, classNameForASM, null, "java/lang/Object", null);
64 
65         // creates a MethodWriter for the 'main' method
66         MethodVisitor mw = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "exec", "()I", null, null);
67 
68         for (Instruction instruction : instructions) {
69             mw.visitInsn(instruction.opCode);
70         }
71 
72         mw.visitInsn(IRETURN);
73         mw.visitMaxs(stackSize, 2);
74         mw.visitEnd();
75 
76         Lookup lookup = MethodHandles.lookup();
77         Class<?> hc = lookup.defineHiddenClass(cw.toByteArray(), false).lookupClass();
78         return hc;
79     }
80 }
81