Hacking Replacing a RPL export?

[gudenau]

I would like to work on a modification to an RPL to change/log what data is passed and returned from various exported methods inside of RPL. I have a few questions regarding the process I could use to do this. I can already inject larger segments into the RPL files.

1. How would one go about making a method that the new export will point to without disturbing the parameters for the method? From what I can see, this should be a few instructions for storing the registers, but I am fairly new to PPC. I can not tell if they are going into the stack or some data segment.
2. How could I use expanded data segments to hold global variables? How could I hold a String?
3. How could I recreate the original method in C, so that I can get out of ASM? I have the signatures for the methods to replace.