ASM 中的 Java 方法参数值
我正在尝试获取 Java 程序方法参数的值.我正在使用 ASM 来检测字节码并获取这些值.但是,我遇到了一些麻烦.
I am trying to get the values of a Java program's method's parameters. I am using ASM to instrument the bytecode and getting these values. However, I'm running into some troubles.
这是用于检测代码的 visitCode() 方法.它正在做的是:
Here is the visitCode() method used to instrument the code. What it is doing is :
- 创建一个空数组来存储收集到的参数.
- 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(将在其中使用值).
.
@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,当方法显然有多个参数时,这不起作用.
However, this is not working when apparently the method have more than one parameter.
获得的类文件显示如下:
The class file obtained shows things like this :
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);
这里创建了 2 个本地对象,而不是加载参数.
Where 2 local objects are created instead of loading the parameters.
字节码没有显示任何奇怪的东西:
The bytecode doesn't show anything weird :
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,显示的错误是(使用 -noverify 时):
And finally, the error showed is (when using -noverify):
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)
否则就是:
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,这应该更有效,因为我只是从堆栈帧中加载信息.我也尝试检查静态 &非静态方法(此处解释的堆栈:http://www.artima.com/insidejvm/ed2/jvm8.html),但仍然没有成功.
Normally, this should rather work as I am just loading information from the stack frame. I tried also to check static & non static methods (as of the stack explained here : http://www.artima.com/insidejvm/ed2/jvm8.html), but still with no success.
对为什么会发生这种情况有任何想法,或者可能有解决方案的想法吗?
Any idea on why this is happening, or possibly an idea of a solution ?
谢谢:)
它现在可以在打包原始类型时工作(感谢下面 int3 的建议 :)).这是 visitCode() 方法的工作代码:
It is now working when boxing up primitive types (thanks to suggestions by int3 below :) ). Here is the working code of visitCode() method :
@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();
}
推荐答案
您正在使用 aastore
将 char
存储到对象数组中,这是类型错误.aastore
只能用于存储对象和数组,这可能就是错误提示预期的对象/数组在堆栈上"的原因.字符应使用 castore
存储在 char 数组中.但是,由于您希望它适用于任意签名,您可能希望将原始类型打包成对象,然后您可以在其上使用 aastore
- 例如char
应该装在 java.lang.Character
对象中.
You are using aastore
to store a char
into an object array, which is a type error. aastore
should only be used to store objects and arrays, which is probably why the error says 'expected object/array on stack'. Characters should be stored in a char array using castore
. However, since you want this to work for arbitrary signatures, you'll probably want to box up the primitive types into objects which you can then use aastore
upon -- e.g. char
should be boxed up in a java.lang.Character
object.
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