我试图获取Java程序方法参数的值。 我正在使用ASM来测试字节码并获取这些值。 但是,我遇到了一些麻烦。ASM中的Java方法参数值
这是用于检测代码的visitCode()方法。 它在做什么:
- 创建一个空数组来存储收集的参数。
- 对于每个参数,将其值加载到数组中。
- 将此数组发送到我的代理的OnMethodEntry方法(其中将使用值)。
。
@Override
public void visitCode() {
int paramLength = paramTypes.length;
// Create array with length equal to number of parameters
mv.visitIntInsn(Opcodes.BIPUSH, paramLength);
mv.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/Object");
mv.visitVarInsn(Opcodes.ASTORE, paramLength);
// Fill the created array with method parameters
int i = 0;
for (Type tp : paramTypes) {
mv.visitVarInsn(Opcodes.ALOAD, paramLength);
mv.visitIntInsn(Opcodes.BIPUSH, i);
if (tp.equals(Type.BOOLEAN_TYPE) || tp.equals(Type.BYTE_TYPE) || tp.equals(Type.CHAR_TYPE) || tp.equals(Type.SHORT_TYPE) || tp.equals(Type.INT_TYPE))
mv.visitVarInsn(Opcodes.ILOAD, i);
else if (tp.equals(Type.LONG_TYPE)) {
mv.visitVarInsn(Opcodes.LLOAD, i);
i++;
}
else if (tp.equals(Type.FLOAT_TYPE))
mv.visitVarInsn(Opcodes.FLOAD, i);
else if (tp.equals(Type.DOUBLE_TYPE)) {
mv.visitVarInsn(Opcodes.DLOAD, i);
i++;
}
else
mv.visitVarInsn(Opcodes.ALOAD, i);
mv.visitInsn(Opcodes.AASTORE);
i++;
}
// Load id, class name and method name
this.visitLdcInsn(new Integer(this.methodID));
this.visitLdcInsn(this.className);
this.visitLdcInsn(this.methodName);
// Load the array of parameters that we created
this.visitVarInsn(Opcodes.ALOAD, paramLength);
mv.visitMethodInsn(Opcodes.INVOKESTATIC,
"jalen/MethodStats",
"onMethodEntry",
"(ILjava/lang/String;Ljava/lang/String;[Ljava/lang/Object;)V");
super.visitCode();
}
但是,当显然该方法有多个参数时,这不起作用。
得到的类文件显示这样的事情:
static void moveDisk(char arg0, char arg1, PrintStream arg2) {
Object[] arrayOfObject = new Object[3]; arrayOfObject[0] = ???; arrayOfObject[1] = ???;
Object localObject;
arrayOfObject[2] = localObject; MethodStats.onMethodEntry(5, "hanoi/TowersOfHanoi", "moveDisk", arrayOfObject);
在其中创建而不是加载参数2个本地对象。
字节码不显示任何奇怪:
static void moveDisk(char, char, java.io.PrintStream);
Code:
0: bipush 3
2: anewarray #4 // class java/lang/Object
5: astore_3
6: aload_3
7: bipush 0
9: iload_0
10: aastore
11: aload_3
12: bipush 1
14: iload_1
15: aastore
16: aload_3
17: bipush 2
19: aload_2
20: aastore
21: ldc #118 // int 5
23: ldc #12 // String hanoi/TowersOfHanoi
25: ldc #119 // String moveDisk
27: aload_3
28: invokestatic #19 // Method jalen/MethodStats.onMethodEntry:(ILjava/lang/String;Ljava/lang/String;[Ljava/lang/Object;)V
最后,表明是(用时-noverify)错误:
param: [Ljava.lang.String;@420e54f3
Exception in thread "Jalen Agent" java.lang.NullPointerException
at hanoi.TowersOfHanoi.solveHanoi(TowersOfHanoi.java)
at hanoi.TowersOfHanoi.main(TowersOfHanoi.java:29)
否则,它是:
Exception in thread "Jalen Agent" java.lang.VerifyError: (class: hanoi/TowersOfHanoi, method: moveDisk signature: (CCLjava/io/PrintStream;)V) Expecting to find object/array on stack
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2442)
at java.lang.Class.getMethod0(Class.java:2685)
at java.lang.Class.getMethod(Class.java:1620)
at sun.launcher.LauncherHelper.getMainMethod(LauncherHelper.java:492)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:484)
通常情况下,这应该工作,因为我只是从堆栈帧加载信息。 我也试过检查静态的非静态方法&(这里解释的堆栈:http://www.artima.com/insidejvm/ed2/jvm8.html),但仍然没有成功。
任何想法为什么会发生这种情况,或者可能是解决方案的想法?
谢谢:)
编辑:
(由下面INT3 :)给点建议谢谢)拳击最多时的原始类型它现在的工作。下面是visitCode()方法的工作的代码:
@Override
public void visitCode() {
int paramLength = paramTypes.length;
// Create array with length equal to number of parameters
mv.visitIntInsn(Opcodes.BIPUSH, paramLength);
mv.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/Object");
mv.visitVarInsn(Opcodes.ASTORE, paramLength);
// Fill the created array with method parameters
int i = 0;
for (Type tp : paramTypes) {
mv.visitVarInsn(Opcodes.ALOAD, paramLength);
mv.visitIntInsn(Opcodes.BIPUSH, i);
if (tp.equals(Type.BOOLEAN_TYPE)) {
mv.visitVarInsn(Opcodes.ILOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Boolean", "valueOf", "(Z)Ljava/lang/Boolean;");
}
else if (tp.equals(Type.BYTE_TYPE)) {
mv.visitVarInsn(Opcodes.ILOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Byte", "valueOf", "(B)Ljava/lang/Byte;");
}
else if (tp.equals(Type.CHAR_TYPE)) {
mv.visitVarInsn(Opcodes.ILOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Character", "valueOf", "(C)Ljava/lang/Character;");
}
else if (tp.equals(Type.SHORT_TYPE)) {
mv.visitVarInsn(Opcodes.ILOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Short", "valueOf", "(S)Ljava/lang/Short;");
}
else if (tp.equals(Type.INT_TYPE)) {
mv.visitVarInsn(Opcodes.ILOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Integer", "valueOf", "(I)Ljava/lang/Integer;");
}
else if (tp.equals(Type.LONG_TYPE)) {
mv.visitVarInsn(Opcodes.LLOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Long", "valueOf", "(J)Ljava/lang/Long;");
i++;
}
else if (tp.equals(Type.FLOAT_TYPE)) {
mv.visitVarInsn(Opcodes.FLOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Float", "valueOf", "(F)Ljava/lang/Float;");
}
else if (tp.equals(Type.DOUBLE_TYPE)) {
mv.visitVarInsn(Opcodes.DLOAD, i);
mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Double", "valueOf", "(D)Ljava/lang/Double;");
i++;
}
else
mv.visitVarInsn(Opcodes.ALOAD, i);
mv.visitInsn(Opcodes.AASTORE);
i++;
}
// Load id, class name and method name
this.visitLdcInsn(new Integer(this.methodID));
this.visitLdcInsn(this.className);
this.visitLdcInsn(this.methodName);
// Load the array of parameters that we created
this.visitVarInsn(Opcodes.ALOAD, paramLength);
mv.visitMethodInsn(Opcodes.INVOKESTATIC,
"jalen/MethodStats",
"onMethodEntry",
"(ILjava/lang/String;Ljava/lang/String;[Ljava/lang/Object;)V");
super.visitCode();
}
如何将参数返回到堆栈,以便函数可以继续使用它们? – Shay