codepreverifier.java

proguard 一个java的混淆器

/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification
 *             of Java bytecode.
 *
 * Copyright (c) 2002-2007 Eric Lafortune ([e-mail])
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.preverify;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.preverification.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.editor.*;
import proguard.classfile.instruction.InstructionConstants;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.*;
import proguard.evaluation.*;
import proguard.evaluation.value.*;
import proguard.optimize.evaluation.*;

import java.util.*;

/**
 * This class can preverify methods in program class pools, according to a given
 * specification.
 *
 * @author Eric Lafortune
 */
public class CodePreverifier
extends      SimplifiedVisitor
implements   MemberVisitor,
             AttributeVisitor
{
    //*
    private static final boolean DEBUG = false;
    /*/
    private static       boolean DEBUG = true;
    //*/


    private final boolean microEdition;

    private final PartialEvaluator   partialEvaluator   = new PartialEvaluator();
    private final LivenessAnalyzer   livenessAnalyzer   = new LivenessAnalyzer(partialEvaluator);
    private final ConstantPoolEditor constantPoolEditor = new ConstantPoolEditor();
    private final AttributesEditor   attributesEditor   = new AttributesEditor();


    /**
     * Creates a new CodePreverifier.
     */
    public CodePreverifier(boolean microEdition)
    {
        this.microEdition = microEdition;
    }


    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}


    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
    {
        // TODO: Remove this when the preverifier has stabilized.
        // Catch any unexpected exceptions from the actual visiting method.
        try
        {
            // Process the code.
            visitCodeAttribute0(clazz, method, codeAttribute);
        }
        catch (RuntimeException ex)
        {
            System.err.println("Unexpected error while preverifying:");
            System.err.println("  Class       = ["+clazz.getName()+"]");
            System.err.println("  Method      = ["+method.getName(clazz)+method.getDescriptor(clazz)+"]");
            System.err.println("  Exception   = ["+ex.getClass().getName()+"] ("+ex.getMessage()+")");

            throw ex;
        }
    }


    public void visitCodeAttribute0(Clazz clazz, Method method, CodeAttribute codeAttribute)
    {
//        DEBUG =
//            clazz.getName().equals("abc/Def") &&
//            method.getName(clazz).equals("abc");

        ProgramClass  programClass  = (ProgramClass)clazz;
        ProgramMethod programMethod = (ProgramMethod)method;

        // Evaluate the method.
        //partialEvaluator.visitCodeAttribute(clazz, method, codeAttribute);
        livenessAnalyzer.visitCodeAttribute(clazz, method, codeAttribute);

        // Collect the stack map frames.
        List stackMapFrameList = new ArrayList();

        for (int offset = 0; offset < codeAttribute.u4codeLength; offset++)
        {
            // Only store frames at the beginning of code blocks.
            if (partialEvaluator.isTraced(offset) &&
                partialEvaluator.isBranchOrExceptionTarget(offset))
            {
                // Convert the variable values to types.
                VerificationType[] variableTypes =
                    correspondingVerificationTypes(programClass,
                                                   programMethod,
                                                   codeAttribute,
                                                   offset,
                                                   partialEvaluator.getVariablesBefore(offset));

                // Convert the stack values to types.
                VerificationType[] stackTypes =
                    correspondingVerificationTypes(programClass,
                                                   programMethod,
                                                   codeAttribute,
                                                   offset,
                                                   partialEvaluator.getStackBefore(offset));
                // Create and store a new frame.
                stackMapFrameList.add(new FullFrame(offset,
                                                    variableTypes,
                                                    stackTypes));
            }
        }

        // Compress the stack map frames if the target is not Java Micro Edition.
        if (!microEdition && !stackMapFrameList.isEmpty())
        {
            // Convert the initial variable values to types.
            VerificationType[] initialVariables =
                correspondingVerificationTypes(programClass,
                                               programMethod,
                                               codeAttribute,
                                               PartialEvaluator.AT_METHOD_ENTRY,
                                               partialEvaluator.getVariablesBefore(0));

            // Special case: the <init> method.
            if (method.getName(programClass).equals(ClassConstants.INTERNAL_METHOD_NAME_INIT))
            {
                initialVariables[0] = VerificationTypeFactory.createUninitializedThisType();
            }

            compressStackMapFrames(initialVariables,
                                   stackMapFrameList);
        }

        // Get the proper name for the attribute to be added/replaced/deleted.
        String stackMapAttributeName = microEdition ?
             ClassConstants.ATTR_StackMap :
             ClassConstants.ATTR_StackMapTable;

        int frameCount = stackMapFrameList.size();

        if (DEBUG)
        {
            Attribute originalStackMapAttribute = codeAttribute.getAttribute(clazz,
                                                                             stackMapAttributeName);

            if (originalStackMapAttribute != null)
            {
                int originalFrameCount = microEdition ?
                    ((StackMapAttribute)originalStackMapAttribute).u2stackMapFramesCount :
                    ((StackMapTableAttribute)originalStackMapAttribute).u2stackMapFramesCount;

                StackMapFrame[] originalFrames = microEdition ?
                    ((StackMapAttribute)originalStackMapAttribute).stackMapFrames :
                    ((StackMapTableAttribute)originalStackMapAttribute).stackMapFrames;

                if (frameCount != originalFrameCount ||
                    !Arrays.equals(stackMapFrameList.toArray(), originalFrames))
                {
                    System.out.println("Original preverification ["+clazz.getName()+"]:");
                    new ClassPrinter().visitProgramMethod(programClass, programMethod);
                }
            }
            else if (frameCount != 0)
            {
                System.out.println("Original preverification empty ["+clazz.getName()+"."+method.getName(clazz)+"]");
            }
        }

        if (frameCount == 0)
        {
            // Remove any stack map (table) attribute from the code attribute.
            attributesEditor.deleteAttribute(programClass,
                                             programMethod,
                                             codeAttribute,
                                             stackMapAttributeName);
        }
        else
        {
            Attribute stackMapAttribute;

            // Create the appropriate attribute.
            if (microEdition)
            {
                // Copy the frames into an array.
                FullFrame[] stackMapFrames = new FullFrame[frameCount];
                stackMapFrameList.toArray(stackMapFrames);

                // Put the frames into a stack map attribute.
                stackMapAttribute = new StackMapAttribute(stackMapFrames);
            }
            else
            {
                // Copy the frames into an array.
                StackMapFrame[] stackMapFrames = new StackMapFrame[frameCount];
                stackMapFrameList.toArray(stackMapFrames);

                // Put the frames into a stack map table attribute.
                stackMapAttribute = new StackMapTableAttribute(stackMapFrames);
            }

            // Fill out the name of the stack map attribute.
            stackMapAttribute.u2attributeNameIndex =
                constantPoolEditor.addUtf8Constant(programClass, stackMapAttributeName);

            // Add the new stack map (table) attribute to the code attribute.
            attributesEditor.addAttribute(programClass,
                                          programMethod,
                                          codeAttribute,
                                          stackMapAttribute);

            if (DEBUG)
            {
                System.out.println("Preverifier ["+programClass.getName()+"."+programMethod.getName(programClass)+"]:");
                stackMapAttribute.accept(programClass, programMethod, codeAttribute, new ClassPrinter());
            }
        }
    }


    // Small utility methods.

    /**
     * Creates and returns the verification types corresponding to the given
     * variables. If necessary, class constants are added to the constant pool
     * of the given class.
     */
    private VerificationType[] correspondingVerificationTypes(ProgramClass    programClass,
                                                              ProgramMethod   programMethod,
                                                              CodeAttribute   codeAttribute,
                                                              int             offset,
                                                              TracedVariables variables)
    {
        int maximumVariablesSize = variables.size();
        int typeCount = 0;
        int typeIndex = 0;

        // Count the the number of verification types, ignoring any nulls at
        // the end.
        for (int index = 0; index < maximumVariablesSize; index++)
        {
            Value value = variables.getValue(index);

            typeIndex++;

            // Remember the maximum live type index.
            if (value != null &&
                (offset == PartialEvaluator.AT_METHOD_ENTRY ||
                 livenessAnalyzer.isAliveBefore(offset, index)))
            {
                typeCount = typeIndex;

                // Category 2 types that are alive are stored as single entries.
                if (value.isCategory2())
                {
                    index++;
                }
            }
        }

        // Create and fill out the verification types.
        VerificationType[] types = new VerificationType[typeCount];

        typeIndex = 0;

        // Note the slightly different terminating condition, because the
        // types may have been truncated.
        for (int index = 0; typeIndex < typeCount; index++)
        {
            Value value         = variables.getValue(index);
            Value producerValue = variables.getProducerValue(index);

            // Fill out the type.
            VerificationType type;