1st clear the basics....
Kernel space: Linux manages the comp's HW in a simple and efficient manner, offering the user a simple and uniform programming interface. In the same way, the kernel, and in particular its device drivers, form a bridge or interface between the end-user/programmer and HW. User space: End-user programs, like the UNIX shell or other GUI based applications r part of the user space. Obviously, these applications need to interact with the system's HW. However, they don’t do so directly, but through the kernel supported functions.
Here is the references : www.cromwell-intl.com/unix/linux-kernel.html
OR
http://alien.slackbook.org/dokuwiki/doku.php?id=linux:kernelbuilding
AND for Device driver: www.linux.com/learn/answers/view/950-how-to-make-linux-device-driver-with-assembly-language

Hi, this site may help:

http://buildroot.uclibc.org/