使用 BCEL 在现有方法中注入代码

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中(在这种情况下，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使用了字节码注入，这也导致我这样做。

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，我已经做了这个，但它不能正常工作。我注入的一些方法工作得很好(因为斐波那契代码，它们变慢了(，运行 DaCapo 框架效果很好，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崩溃了，哪些方法成功了，但我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，因为到目前为止我可以看到，但我远非专家。当我比较注入前后的字节码时，我看到斐波那契算法后跟其余方法，唯一的区别是增加了堆栈位置(因为注入的代码也使用堆栈空间(。
成功的方法既包括公共方法，也包括私有方法。带和不带参数。
一些失败的方法包含异常，有些则不包含。有些方法中有尝试捕获，有些则没有

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，是不是有些事情我没有想到或忽略了？

下面你会发现一个示例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(

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的代码.java：

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

您可以在下面看到在net.sourceforge.pmd.AbstractRuleChainVisiter中注入访问All方法失败后的完整错误

===== 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

此方法的代码(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遇到的错误相当的错误。这导致参数和当非静态时，this与斐波那契代码中定义的变量发生冲突。

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

顺便说一下，这不是成功将大量代码注入方法的好方法，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预编译方法的少量调用。

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