Subject: Re: interrupt variables
To: Robert Swindells <rjs@fdy2.demon.co.uk>
From: Richard Earnshaw <rearnsha@arm.com>
List: port-arm32
Date: 07/24/2001 09:46:45
> 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.