Magic numbers in elf-loader/platform/*/main.cc (ARM based platforms)

Hi All,
in the elf-loader/platform/*/main.cc there are magic numbers like the follwoing
--------csb337--------------
 void (*func)(unsigned long) = (void (*)(unsigned long)) (bootaddr -
0xD0000000);
----------------------------
Could somebody explain this?, more confusing is
#define PHYS_OFFSET 0x00000000
(and this is for all platforms)

I am trying to port L4Ka to a ARM Based platform, RAM mapped starts at
0x00000000 and shadows to 0x70000000, then what could be this magic
number for this platform?

/Thanks