linux-rt does not provide hardware NX protection

[Laurent Bonnaud]

Hi,

here is the problem:

$ dmesg | grep NX
[ 0.000000] Using x86 segment limits to approximate NX protection
[...]

And indeed, PAE, which is necessary to have NX protection, is not set in the kernel config:

$ grep PAE /boot/config-2.6.31-7-rt
[nothing]

This contrasts with linux-image-2.6.31-13-generic-pae where:

$ dmesg | grep NX
[ 0.000000] NX (Execute Disable) protection: active
[...]

$ grep PAE /boot/config-2.6.31-13-generic-pae
CONFIG_X86_PAE=y

So currently I have to choose between increased security and low latency (my choice is security).

How about providing a linux-rt-pae kernel flavor ?

ProblemType: Bug
Architecture: i386
Date: Mon Oct 12 10:30:17 2009
DistroRelease: Ubuntu 9.10
Package: linux-image-2.6.31-7-rt 2.6.31-7.9
ProcVersionSignature: Ubuntu 2.6.31-7.9-rt
SourcePackage: linux-rt
Uname: Linux 2.6.31-7-rt i686
XsessionErrors:
 (polkit-gnome-authentication-agent-1:4324): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
 (gnome-settings-daemon:4341): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed

[Alessio Igor Bogani (abogani)]

Laurent,

Unfortunately there is no way to add a flavour (-PAE) for rt kernel in Karmic so if your still interested we'll could address that issue for Lucid (Ubuntu 10.04).

Thanks!

[Laurent Bonnaud (laurent-bonnaud)]

On Mon, 2009-10-12 at 12:22 +0000, Alessio Igor Bogani wrote:

> Unfortunately there is no way to add a flavour (-PAE) for rt kernel in
> Karmic

Too bad :<.

> so if your still interested we'll could address that issue for
> Lucid (Ubuntu 10.04).

Of course I'm still interested in running a -rt kernel. karmic is not
even out that I am already looking forward to lucid !

--
Laurent Bonnaud.
http://www.lis.inpg.fr/pages_perso/bonnaud/

[Robert Rose (rrose)]

I just installed the karmic rt kernel and was also disappointed to discover it does not include PAE, as I have 8gb RAM. (And I cannot run the 64bit kernel for compatibility reasons...)

[Laurent Bonnaud (laurent-bonnaud)]

Does anybody know if lucid offers a RT+PAE kernel ?

[Andy Whitcroft (apw)]

@Robert -- why can you not run the 64 bit kernel. You can use that with the 32 bit userspace if you are forceful about it.

[Laurent Bonnaud (laurent-bonnaud)]

I just tested lucid beta1+updates and the proposed -rt kernel is still a 2.6.31 version and PAE is not enabled.

[Laurent Bonnaud (laurent-bonnaud)]

NX is still not active in the lowlatency maverick kernel:

$ grep PAE /boot/config-2.6.35-20-lowlatency
[nothing]

[Laurent Bonnaud (laurent-bonnaud)]

NX protection is now available in natty in the -lowlatency-pae kernel flavor. Thanks !