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对于我的论文研究,我需要将一段代码注入到我没有源代码的测试套件中的可定义方法(在本例中为 DaCapo 基准测试套件,http: //dacapobench.org/ )。我论文的这一部分所基于的先前研究为此使用了字节码注入,这导致我也这样做。

我使用 Apache 的 BCEL 库 ( http://commons.apache.org/proper/commons-bcel/ ) 构建了一个小程序,使我能够在其他语句之前将斐波那契算法注入方法体中。

现在,我做了这个,但它不能正常工作。我注入的一些方法运行良好(因为斐波那契代码它们速度较慢),并且运行 DaCapo 框架运行良好,而其他注入的方法会破坏代码。

问题是,我不知道为什么,即使我知道哪些方法发生故障以及哪些方法成功了,我也无法在损坏的方法中找到重复出现的模式。

  • 字节码似乎很好,到目前为止我可以看到,但我离专家还很远。当我比较注入前后的字节码时,我看到斐波那契算法后面跟着其余的方法,唯一的区别是增加的堆栈位置(因为注入的代码也使用堆栈空间)。
  • 成功的方法包含公共方法和私有方法。带参数和不带参数。
  • 一些失败的方法包含异常,而另一些则没有。有些人尝试过,有些人没有。等等等等

我可以粘贴一些失败的方法,但这会使这篇文章比现在更长。所以我想知道,有什么我没有考虑或忽略的事情吗?

下面你会找到一个示例 java 文件,它的结果和我编写的 BCEL 程序。

一个简单的例子,我有一个名为 DemoClass.java 的 java 文件:

public class DemoClass {

    public static void main(String[] argv) {
        System.out.println("Demo body");
        test();
    }

    public static void test() {
        System.out.println("Demo test");
    }
}

在我的 shell 中调用以下 java 命令后:

javac DemoClass.java; java -cp bcel-5.2.jar:. InjectCodeBCEL DemoClass test 123456789 ; java DemoClass

(bcel-5.2.jar文件可以在前面提到的apache网站上找到)

该程序将如下所示:

public class DemoClass {

    public static void main(String[] argv) {
        System.out.println("Demo body");
        test();
    }

    public static void test() {
        int[] fibNumbers = new int[100]; 
        for (int i = 0; i < 123456789; i++) { 
            int j = i % 100; 
            if (i == 0) { 
                fibNumbers[i] = 0; 
            } 
            else if (i == 1) { 
                fibNumbers[i] = 1; 
            } 
            else { 
                int k = (i - 1) % 100; 
                int m = (i - 2) % 100; 
                int n = fibNumbers[k] + fibNumbers[m]; 
                fibNumbers[j] = n; 
            }  
        } 
        System.out.println("Demo test");
    }
}

这是 InjectCodeBCEL.java 的代码:

import java.io.IOException;
import org.apache.bcel.classfile.*;
import org.apache.bcel.generic.*;
import org.apache.bcel.*;

public class InjectCodeBCEL {

    static public void main(String args[]) {
        //Get class to modify from program argument
        JavaClass mod = null;
        String methodName = (args.length >= 2) ? args[1] : "";
        int loopsize = (args.length >= 3) ? Integer.parseInt(args[2]) : 1;
        try {
            mod = Repository.lookupClass(args[0]);
        }
        catch (Exception e) {
            System.err.println("Could not get class " + args[0]);
            return;
        }

        //Create a generic class to modify
        ClassGen modClass = new ClassGen(mod);
        //Create a generic constantpool to modify
        ConstantPoolGen cp = modClass.getConstantPool();
        boolean methodEdited = false;

        Method[] methods = mod.getMethods();
        for (int i = 0; i < methods.length; i++) {
            if (methods[i].getName().equals(methodName)) {

                System.out.println("Method: " + methods[i]);
                // System.out.println("before:\n" + methods[i].getCode());
                modClass.removeMethod(methods[i]);
                Method newMethod = insertCodeInMethod(mod, methods[i], cp, loopsize);
                // System.out.println("after:\n" + newMethod.getCode());
                modClass.addMethod(newMethod);

                methodEdited = true;
            }
        }
        if (methodEdited) {
            modClass.update();
            try {
                //Write modified class
                JavaClass newClass = modClass.getJavaClass();
                String classname = args[0].replace(".","/");
                newClass.dump(classname + ".class");
                System.out.println("Class " + classname + " modified");
            }
            catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static Method insertCodeInMethod(JavaClass mod, Method method, ConstantPoolGen cp, int loopsize) {
        MethodGen mg = new MethodGen(method, mod.getClassName(), cp);

        InstructionList il = mg.getInstructionList();
        InstructionHandle ihs = il.getStart();
        InstructionList ils = new InstructionList();
        InstructionFactory f = new InstructionFactory(cp);

        String CLASS_NAME = mod.getClassName();

        int ARRAY_SIZE = 100;
        int LOOP_SIZE = loopsize;

        int INCREASE_ID = mg.isStatic() ? 0 : 1; // if not static, this has position 0 on the stack
        Type[] types = mg.getArgumentTypes();
        // Increase the stack location(?) so they don't collide with the methods parameters.
        for (int i = 0; i < types.length; i++) {
            INCREASE_ID += types[i].getSize();
        }

        int VAR_ARRAY = 0 + INCREASE_ID;
        int VAR_I = 1 + INCREASE_ID;
        int VAR_II = 2 + INCREASE_ID;
        int VAR_I_MIN_1 = 3 + INCREASE_ID;
        int VAR_I_MIN_2 = 4 + INCREASE_ID;
        int VAR_SUM = 5 + INCREASE_ID;
        int VAR_JUMPTO = 6 + INCREASE_ID;

        // init array
        ils.append(new PUSH(cp, ARRAY_SIZE));
        ils.append(new NEWARRAY(Type.INT));
        ils.append(new ASTORE(VAR_ARRAY));

        // create iterator = 0 for while 
        ils.append(new PUSH(cp, 0));
        ils.append(new ISTORE(VAR_I));

        // Main while loop:
        InstructionHandle beforeWhile = ils.append(new ILOAD(VAR_I));
        ils.append(new PUSH(cp, LOOP_SIZE));
        // While condition:
        BranchHandle whileCondition = ils.append(new IF_ICMPLT(null)); // if (VAR_I < LOOP_SIZE): jump to "whileBody"
        BranchHandle whileConditionFalseGoto = ils.append(new GOTO(null)); // if not: jump to "afterWhile"

            // While body:
            InstructionHandle whileBody = ils.append(new ILOAD(VAR_I));
            ils.append(new PUSH(cp, ARRAY_SIZE));
            ils.append(new IREM());
            ils.append(new ISTORE(VAR_II)); // create int ii = i % ARRAY_SIZE;

            // if (i == 0)
            ils.append(new ILOAD(VAR_I));
            ils.append(new PUSH(cp, 0));
            BranchHandle ifIteratorIs0 = ils.append(new IF_ICMPEQ(null));
            BranchHandle ifIteratorIs0FalseGoto = ils.append(new GOTO(null));
                // If true body
                InstructionHandle ifIteratorIs0Body = ils.append(new ALOAD(VAR_ARRAY));
                ils.append(new ILOAD(VAR_I));
                ils.append(new PUSH(cp, 0));
                ils.append(new IASTORE());
                BranchHandle ifIteratorIs0Done = ils.append(new GOTO(null));

            // "else" if (i != 1)
            InstructionHandle beginIfIteratorIsNot1 = ils.append(new ILOAD(VAR_I));
            ils.append(new PUSH(cp, 1));
            BranchHandle ifIteratorIsNot1 = ils.append(new IF_ICMPNE(null));
                // false: else: so in this case: if (!(i != 1)): 
                ils.append(new ALOAD(VAR_ARRAY));
                ils.append(new ILOAD(VAR_I));
                ils.append(new PUSH(cp, 1));
                ils.append(new IASTORE());
                // done, go to i++;
                BranchHandle ifIteratorIsNot1FalseGoto = ils.append(new GOTO(null));

                // If true body (so if i != 1)..
                // create variable VAR_I_MIN_1 for array index (i-1)
                InstructionHandle ifIteratorIsNot1Body = ils.append(new ILOAD(VAR_I));
                ils.append(new PUSH(cp, 1));
                ils.append(new ISUB());
                ils.append(new PUSH(cp, ARRAY_SIZE));
                ils.append(new IREM());
                ils.append(new ISTORE(VAR_I_MIN_1)); // create int i_min_1 = (i - 1) % ARRAY_SIZE;
                // create variable VAR_I_MIN_2 for array index (i-2)
                ils.append(new ILOAD(VAR_I));
                ils.append(new PUSH(cp, 2));
                ils.append(new ISUB());
                ils.append(new PUSH(cp, ARRAY_SIZE));
                ils.append(new IREM());
                ils.append(new ISTORE(VAR_I_MIN_2)); // create int i_min_2 = (i - 2) % ARRAY_SIZE;
                // load the array values:
                ils.append(new ALOAD(VAR_ARRAY));
                ils.append(new ILOAD(VAR_I_MIN_1));
                ils.append(new IALOAD());
                ils.append(new ALOAD(VAR_ARRAY));
                ils.append(new ILOAD(VAR_I_MIN_2));
                ils.append(new IALOAD());
                // add the two values, and save them
                ils.append(new IADD());
                ils.append(new ISTORE(VAR_SUM));
                // add the new calculated number to the array
                ils.append(new ALOAD(VAR_ARRAY));
                ils.append(new ILOAD(VAR_II));
                ils.append(new ILOAD(VAR_SUM));
                ils.append(new IASTORE());
                // Done; go to i++;
                BranchHandle ifIteratorIsNot1Done = ils.append(new GOTO(null));

            // Increment i with 1
            InstructionHandle generalIfDoneGoto = ils.append(new IINC(VAR_I,1));

            // Goto that whil restart this loop:
            BranchHandle whileGotoBegin = ils.append(new GOTO(null)); // jumps to "beforeWhile"

        // We need something to jump to when done with the outer loop.
        InstructionHandle afterWhile = ils.append(new PUSH(cp, 0));
        ils.append(new ISTORE(VAR_JUMPTO));

        // While targets:
        whileCondition.setTarget(whileBody);
        whileConditionFalseGoto.setTarget(afterWhile);
        whileGotoBegin.setTarget(beforeWhile);
        // if (i == 0)
        ifIteratorIs0.setTarget(ifIteratorIs0Body);
        ifIteratorIs0FalseGoto.setTarget(beginIfIteratorIsNot1);
        ifIteratorIs0Done.setTarget(generalIfDoneGoto);
        // if (i == 1)
        ifIteratorIsNot1.setTarget(ifIteratorIsNot1Body);
        ifIteratorIsNot1FalseGoto.setTarget(generalIfDoneGoto);
        ifIteratorIsNot1Done.setTarget(generalIfDoneGoto);

        InstructionHandle ihss = il.insert(ihs,ils);
        il.redirectBranches(ihs, ihss);
        il.update();

        mg.setMaxStack();
        mg.setMaxLocals();
        mg.update();
        return mg.getMethod();
    }
}

更新

下面你可以看到 net.sourceforge.pmd.AbstractRuleChainVisitor 中的 visitAll 方法注入失败后的完整错误

===== DaCapo 9.12 pmd starting =====
java.lang.reflect.InvocationTargetException
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.dacapo.harness.Pmd.iterate(Pmd.java:58)
    at org.dacapo.harness.Benchmark.run(Benchmark.java:166)
    at org.dacapo.harness.TestHarness.runBenchmark(TestHarness.java:218)
    at org.dacapo.harness.TestHarness.main(TestHarness.java:171)
    at Harness.main(Harness.java:17)
Caused by: java.lang.ClassFormatError: LVTT entry for 'nodes' in class file net/sourceforge/pmd/AbstractRuleChainVisitor does not match any LVT entry
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at org.dacapo.harness.DacapoClassLoader.loadClass(DacapoClassLoader.java:124)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at org.dacapo.harness.DacapoClassLoader.loadClass(DacapoClassLoader.java:124)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at net.sourceforge.pmd.RuleSets.<init>(RuleSets.java:27)
    at net.sourceforge.pmd.RuleSetFactory.createRuleSets(RuleSetFactory.java:82)
    at net.sourceforge.pmd.RuleSetFactory.createRuleSets(RuleSetFactory.java:70)
    at net.sourceforge.pmd.PMD.doPMD(PMD.java:359)
    at net.sourceforge.pmd.PMD.main(PMD.java:415)
    ... 9 more

该方法的代码(由JD-GUI生成):

  public void visitAll(List<CompilationUnit> astCompilationUnits, RuleContext ctx)
  {
    initialize();
    clear();

    long start = System.nanoTime();
    indexNodes(astCompilationUnits, ctx);
    long end = System.nanoTime();
    Benchmark.mark(8, end - start, 1L);

    for (RuleSet ruleSet : this.ruleSetRules.keySet())
      if (ruleSet.applies(ctx.getSourceCodeFile()))
      {
        visits = 0;
        start = System.nanoTime();
        for (Rule rule : (List)this.ruleSetRules.get(ruleSet)) {
          List nodeNames = rule.getRuleChainVisits();
          for (int j = 0; j < nodeNames.size(); j++) {
            List nodes = (List)this.nodeNameToNodes.get(nodeNames.get(j));
            for (SimpleNode node : nodes)
            {
              while ((rule instanceof RuleReference)) {
                rule = ((RuleReference)rule).getRule();
              }
              visit(rule, node, ctx);
            }
            visits += nodes.size();
          }
          end = System.nanoTime();
          Benchmark.mark(1, rule.getName(), end - start, visits);
          start = end;
        }
      }
    int visits;
  }

这是一个与我的代码错过“insertCodeInMethod”中的堆栈位置增加部分时得到的错误相当的错误。这导致参数和非静态时 this 与斐波那契代码中定义的变量发生冲突。

4

1 回答 1

3

LVTT代表LocalVariableTypeTable和。LVT_ LocalVariableTable这些是在更改方法时必须调整或删除的调试信息。

顺便说一句,将大量代码成功注入方法并不是一个好方法,因为它会产生各种错误来源,意味着重新发明轮子(构建编译器)并导致转换后的类中的代码重复。大多数使用代码注入/类文件转换的应用程序只会注入对预编译方法的少量调用。

于 2013-10-07T08:06:01.687 回答