how to get the physicall address of kernel code

$ cat /boot/System.map-2.6.32-27-generic | grep text

This command will give you virtual address. The first one is the start of kernel code, For example, on my Ubuntu:

$ cat /boot/System.map-2.6.32-27-generic | grep text 

c0100000 T _text

If you change the c to 0, you changed the virtual address to physical address on Linux. 

Why? please see: http://jianggmulab.blogspot.com/2009/09/blog-post.html

$ cat /boot/System.map-2.6.32-27-generic | grep etext

This one will give you the end virtual address of kernel code.

$ cat /proc/iomem

This command will give your general picture of current memory, and all the address are physical address. For example, on my Ubuntu:
  00100000-00592a36 : Kernel code