Creating additional callbacks in JVMTI Agent

[anderruiz]

I'm trying to create a JVMTI Agent that uses ASM library to modify a class bytecode. I managed to create a simple agent extending JvmtiAgentBase that receives the normal callbacks. I was also able to install a hook in ClassFileLoadHook that is working.

My problem starts with the mapping of arguments. The native call is:

void JNICALL ClassFileLoadHook(jvmtiEnv* jvmti, JNIEnv* jni, jclass class_being_redefined, jobject loader, const char* name, jobject protection_domain, jint data_len, const unsigned char* data, jint* new_data_len, unsigned char** new_data)

How is this mapped to Java types?. I saw a similar example with:

void JNICALL VMInit(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread)

That is mapped to:

public static void onVMInit(JvmtiEnv jvmti, JNIEnvironment jni, @SuppressWarnings("unused") JNIObjectHandle thread)

My problem in this case is, how do I interact with thread, I tried using JNIObjectHandles class but I always get invalid handle errors

Any help is really appreciated

[anderruiz]

I was able to receive the callback property with this signature:

public static void onClassFileLoadHook(final JvmtiEnv jvmti, final JNIEnvironment jni, final JNIObjectHandle clazz,
	final JNIObjectHandle loader,
	final CCharPointer name, final Object protectionDomain, final int dataLen, final CCharPointer data,
	final CIntPointer newDataLength, final CCharPointerPointer newData)