proc filesystem souce code

["Xiangfei Jia" <xjianz@xxxxxxxxx>]

I want to study how proc filesytem reads information from the kernel.
Like I want to find out where are the souce codes for 
/proc/meminfo, /proc/cpuinfo, /proc/devices. Can I get some help where
I can locate the souce code in the 2.6 kernel. 

Thanks!!!

Fei