Searching in source code is trivial in GNU/Linux terminal. Most used utility for this task is grep.
For recursively search in large source tree one can use follow command:
$ egrep -ir ';-\)' *
But I like ack utility more. For similar search with ack we can type:
$ ack-grep ';-\)'
So, let's take ack and try to find another smile in linux kernel — this one :-(
We most get linux sources, unpack it, navigate to its top directory and use ack.
Full output for last command you can find here (first command output from ack there).