Default [Q] Help with allowing KGDB debugging on Samsung Galaxy S4 I9505 via JTAG

Hi, I am currently working on a project to debug the kernel on Samsung Galaxy S4 I9505. I have a riff box, which allows connection to the phone via JTAG. I also downloaded the open source kernel from, and after searching the internet for ways to allow kernel debugging, I am still unable to achieve the goal. I found some websites which says that CONFIG_KGDB must be enabled, but when I searched through the source files for the kernel, I can't seem to find the flag. Can anyone give me pointers on how to proceed with this? I'm new to rom/kernel compiling and stuff, so I will gladly appreciate any help. Thank you!