我在字節碼注入方面很新穎。直到現在,我能夠通過詳盡的研究和痛苦的試驗和錯誤獲得我想要的一切:-)但是我似乎已經達到了我目前所追求的目標。所以,這裏是:我的第一個stackoverflow問題!帶有ASM的Java字節碼檢測:INVOKESPECIAL指令處的代碼注入驗證錯誤
我的目標是通過一個Java代理跟蹤方法調用的對象的引用。我正在使用ASM 4.0庫並已實施了一個AdviceAdapter。 我重寫visitMethodInsn() - 方法是這樣的:
/**
* Visits a method instruction. A method instruction is an instruction that invokes a method.
* The stack before INVOKEINTERFACE, INVOKESPECIAL and INVOKEVIRTUAL instructions is:
* "objectref, [arg1, arg2, ...]"
*
* @param opcode the opcode of the type instruction to be visited. This opcode is either INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC or INVOKEINTERFACE.
* @param owner the internal name of the method's owner class.
* @param name the method's name.
* @param desc the method's descriptor.
*/
@Override
public void visitMethodInsn(int opcode, String owner, String name, String desc) {
if (isExcluded()) {
super.visitMethodInsn(opcode, owner, name, desc);
return;
}
int arraySlot = -1;
boolean isStatic = false;
if (opcode == INVOKEVIRTUAL || opcode == INVOKEINTERFACE) {
arraySlot = saveMethodParameters(owner, desc);
super.visitMethodInsn(opcode, owner, name, desc);
} else if (opcode == INVOKESTATIC) {
isStatic = true;
super.visitMethodInsn(opcode, owner, name, desc);
} else if (opcode == INVOKESPECIAL && !owner.equals("java/lang/Object")) {
//TODO: Causes VerifyError
arraySlot = saveMethodParameters(owner, desc);
super.visitMethodInsn(opcode, owner, name, desc);
} else {
super.visitMethodInsn(opcode, owner, name, desc);
}
if (arraySlot > 0) {
loadLocal(arraySlot);
push(0);
arrayLoad(Type.getType(Object.class));
} else {
super.visitInsn(ACONST_NULL);
}
super.visitMethodInsn(INVOKESTATIC, "net/myjavaagent/MethodLogger",
"writeToLoggerTest", "(Ljava/lang/Object;)V");
}
/**
* Pops the method invocation' arguments and objectref off the stack, saves them into a local array variable and
* then puts them back on the stack again.
*
* @param owner owner class of the method
* @param desc method descriptor
* @return the identifier of the local variable containing the parameters.
*/
private int saveMethodParameters(String owner, String desc) {
JavaTracerAgent.agentErrorLogger.info("Save method parameters: " + owner + " " + desc);
// Preparing the array construction
Type objectType = Type.getType(Object.class);
Type objectArrayType = Type.getType("[Ljava/lang/Object;");
Type[] invokeParamTypes = getMethodParamTypes(owner, desc);
int invokeParamCount = invokeParamTypes.length;
// allocate a slot for the method parameters array
int arrayLocal = newLocal(objectArrayType);
// construct the object array
push(invokeParamCount);
newArray(objectType);
// store array in the local variable
storeLocal(arrayLocal);
// pop the arguments off the stack into the array
// note: the top one is the last parameter !
for (int i = invokeParamCount - 1; i >= 0; i--) {
Type type = invokeParamTypes[i];
JavaTracerAgent.agentErrorLogger.info("Get from stack [" + i + "]:" + type.toString());
if (type != null) {
// convert value to object if needed
box(type);
// load array and swap under value
loadLocal(arrayLocal);
swap(objectArrayType, objectType);
// load index and swap under value
push(i);
swap(Type.INT_TYPE, objectType);
} else {
// this is a static method and index is 0 so we put null into the array
// load array index and then null
loadLocal(arrayLocal);
push(i);
push((Type) null);
}
// store the value in the array as an object
arrayStore(objectType);
}
// now restore the stack and put back the arguments from the array in increasing order
for (int i = 0; i < invokeParamCount; i++) {
Type type = invokeParamTypes[i];
JavaTracerAgent.agentErrorLogger.info("Put to stack [" + i + "]:" + type.toString());
if (type != null) {
// load the array
loadLocal(arrayLocal);
//retrieve the object at index i
push(i);
arrayLoad(objectType);
//unbox if needed
unbox(type);
} else {
// this is a static method so no target instance has to be put on stack
}
}
return arrayLocal;
}
/**
* Returns a type array containing the parameters of a method invocation:
* <ul><li>owner type</li><li>arg1 type</li><li>arg2 type</li><li>...</li><li>argN type</li></ul>
*
* @param owner owner class
* @param desc method descriptor
* @return method parameter types
*/
public Type[] getMethodParamTypes(String owner, String desc) {
Type ownerType = Type.getObjectType(owner);
Type[] argTypes = Type.getArgumentTypes(desc);
int numArgs = argTypes.length;
Type[] result = new Type[numArgs + 1];
result[0] = ownerType;
System.arraycopy(argTypes, 0, result, 1, numArgs);
return result;
}
總之,我試圖挽救一切之前執行到一個局部變量的INVOKESOMETHING操作是在棧上。 爲了啓用方法操作的執行,我必須把整個東西放回堆棧。之後,我假設被調用對象的引用是我本地數組中的第一個條目。
下面是我的一個測試類。這其中的道理很簡單:它纔剛剛開始另一個線程:
/**
* My test class.
*/
public class ThreadStarter {
public static void main(String args[]) {
Thread thread = new Thread("Hugo") {
@Override
public void run() {
System.out.println("Hello World");
}
};
thread.start();
}
}
關於INVOKEVIRTUAL,INVOKEINTERFACE和INVOKESTATIC我沒有遇到任何問題。一切似乎都很好,日誌輸出正是我所期望的。 但是,INVOKESPECIAL指令似乎存在問題。我在這裏遇到了一個醜陋的VerifyError,所以我想在處理堆棧的過程中必然會出現問題。
Exception in thread "main" java.lang.VerifyError: (class: net/petafuel/qualicore/examples/ThreadStarter, method: main signature: ([Ljava/lang/String;)V) Expecting to find object/array on stack
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:171)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:113)
用「-noverify」啓動測試類會使VerifyError消失。一切似乎都完美地工作,我得到所需的輸出。我可以把它這樣,但實際上整個問題是導致我的痛苦,讓我睡得很不好;-)
如果我的理解是正確的,有些像聲明中「新的Thread()」原來是
NEW java/lang/Thread
DUP
INVOKESPECIAL <init>
in bytecode。在構造函數被調用之前,新創建的對象是否仍然未初始化會是一個問題嗎?
我不明白爲什麼代碼工作,但JVM校驗過程中抱怨。
即使在看反編譯的代碼改編後並不能幫助我:
// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3)
// Source File Name: ThreadStarter.java
public class ThreadStarter
{
public ThreadStarter()
{
MethodLogger.writeToLoggerTest(null);
}
public static void main(String args[])
{
JVM INSTR new #2 <Class ThreadStarter$1>;
JVM INSTR dup ;
"Hugo";
Object aobj[] = new Object[2];
aobj;
JVM INSTR swap ;
1;
JVM INSTR swap ;
JVM INSTR aastore ;
aobj;
JVM INSTR swap ;
0;
JVM INSTR swap ;
JVM INSTR aastore ;
((_cls1)aobj[0])._cls1((String)aobj[1]);
MethodLogger.writeToLoggerTest(aobj[0]);
Thread thread;
thread;
thread;
Object aobj1[] = new Object[1];
aobj1;
JVM INSTR swap ;
0;
JVM INSTR swap ;
JVM INSTR aastore ;
((Thread)aobj1[0]).start();
MethodLogger.writeToLoggerTest(aobj1[0]);
return;
}
}
一些額外的信息: 我用的IntelliJ IDEA 10.5.4深化發展和使用jdk1.6.0_39。
最後,我希望這裏有人能幫助我獲得必要的洞察力。提前致謝!
據我所知,關於傳遞單元化實例有一些限制。 (也就是用「new」創建的對象,但尚未調用構造函數的對象),我想這會導致您的驗證錯誤。有關更詳細的驗證輸出,請嘗試使用內置於ASM中的驗證程序。它提供了有關錯誤的更多信息 – ruediste 2013-05-06 07:34:25
感謝您的回覆以及使用ASM驗證程序的提示。雖然我沒有得到任何關於使用ASM驗證器的問題的任何輸出,但我會考慮它可能面臨的任何即將出現的問題。 – 2013-05-07 14:48:43