Question

I have an embedded linux system running on cortexA8.I understand the kernel symbol PHYS_OFFSET represents the physical start address of RAM http://www.kernelport.org/defines.html. I need the value of this symbol in user space for some validation purpose in some shell script that runs after kernel has booted up. The /proc filesystem doesnt have this info. Pls let me know if I can get this value by some means.

Answer 1

You can try to utilize I/O memory map by reading /proc/iomem which should tell about System RAM – all address in iomem is real / physical addresses.

This is from my Android phone which has a 1GB ram (0xbfffffff – 0x80000000).

$cat /proc/iomem
...
80200000-88cfffff : System RAM
  80300000-80c708cf : Kernel text
  80d00000-80fb1dcb : Kernel data
88d00000-88d00fff : ramdumpinfo
88d01000-88d04fff : amsslog
88de0000-88dfffff : ram_console
90000000-ab4fffff : System RAM
b9a02000-bfffffff : System RAM

You somehow need to convert the range specified in System RAM to what you need.