detecting particular memoy address is accessed

From: Joe Xu (josephjxu_at_yahoo.com)
Date: 02/21/04 

Date: 20 Feb 2004 21:38:50 -0800

I am new in linux development. In Linux, is it possible to detect when
a specified memory address (virtual or physic) is accessed? If answer
is yes, how?

Any clue or direction to it will be more than helpful.

Thanks -joe