kccmp

kccmp is a simple tool for comparing two linux kernel ".config" files.

It has the following features:

Displays the configuration variables with different values.
Displays the configuration variables and values which are found in only one of the compared files.

usage: % kccmp /path/to/first/.config /path/to/second/.config

example: % kccmp /usr/src/linux/.config /usr/src/linux/.config.old