[Pharo-project] can I debug a primitive?

Yes, I am newbie with low stuff like this. I have downloaded VMMaker and browse the class Interpreter to see the smalltalk (slang) code of the primitives I want to investigate that are primitiveStoreImageSegment and primitiveLoadImageSegment.....now, the question is, should I be able to put a self halt there and debug it? I tried but I did nothing. Is this possible ? I thought it was :( Thanks for the help. Mariano