PaX & ATI Troubles in 2.6.26 / 2.6.27

[Klaus Kusche]

Dear PaX Team / ATI developers!

I've had troubles after upgrading to the latest Xorg drivers with
2.6.26, and I've had even more troubles after upgrading to 2.6.27.

Environment:
* x86-64 pure (no 32 bit support), kernel with PaX (Gentoo-hardened)
* ATI RV515 (Radeon X1300), Xorg server with "radeon" driver, 
drm enabled in kernel. 
* High-res text mode (no framebuffer) on console.


Troubles in 2.6.26:
2.6.26 was already working fine, 
but after upgrading to the latest Xorg server, libs and drivers, 
the Xorg server process got a kernel null pointer when starting.
The system was still alive, but the console was black & out of control
(console switching did not work, nor did Alt-SysRq console kill).

Turning off drm in the kernel solved the problem (but made X dog slow).
I've no idea if this was PaX-related, I didn't suspect PaX at that time.

(now that I have 2.6.27 up and running fine,
I don't care any longer about these 2.6.26 problems).


Troubles in 2.6.27:
System rebooted while bringing up the kernel.
Some initial kernel boot text lines displayed for tenths of a second,
then came the BIOS counting memory...
As far as I can tell, the reboot happened at the moment where
the kernel tries to switch from VGA to high-res text mode
(that's why I assume this is ATI-related...).

The problem is related to PaX kernel-mode (not user-mode!) 
execute protection, which is enabled in my kernel: 
If kernel-mode exec protection is turned off,
everything is fine (system boots, X works, even with drm).

(however, I would really like to have my kernel exec prot back!)


My questions:
* Are any of these problems known?
* Are the latest ATI drivers in the kernel
doing something which might collide with kernel-mode execute protection
(i.e. do they execute some code with is not part of the kernel code,
but e.g. taken from the BIOS?).


Many thanks in advance for your help!

Greetings from snowy Austria

-- 
DI. Dr. Klaus Kusche
Email: Klaus.Kusche at computerix.info    WWW: http://www.computerix.info/
Phone @ home: +43 7234 83894           Phone @ work: +43 732 7090 23120
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