> IIRC, AP_KR is actually implemented as kernel READ-WRITE; there is no 
> protection mode in the MMU bits for kernel read-only.   Well, you can mark 
> pages as being AP=00,S=1,R=0, but the SR bits are in CP15r1 which means 
> that it's fiddly to keep changing them; the kernel isn't set up to do 
> that, and without doing that it would be impossible to spot the kernel 
> generating a genuine segfault.

Which of course is all a load of tosh (as 30 seconds looking at the source 
will show).  S=1,R=0 is how the system is configured (at least, that is 
how sa110_setup seems to be setting the register) and AP_KR is AP=00; so 
the pages should be mapped read-only.

Doh!

R.