Re: Debian SID kernel doesn't boot on PowerBook 3400c

Le 04/08/2021 à 02:34, Finn Thain a écrit :

On Tue, 3 Aug 2021, Christophe Leroy wrote:

quoted

Looks like the memory errors are linked to KUAP (Kernel Userspace Access
Protection). Based on the places the problems happen, I don't think
there are any invalid access, so there must be something wrong in the
KUAP logic, probably linked to some interrupts happenning in kernel mode
while the KUAP window is opened. And because is not selected by default
on book3s/32 until 5.14, probably nobody ever tested it in a real
environment before you.

I think the issue may be linked to commit
https://github.com/linuxppc/linux/commit/c16728835 which happened
between 5.12 and 5.13.

The messages, "Kernel attempted to write user page (c6207c) - exploit
attempt? (uid: 0)", appear in the console logs generated by v5.13. Those
logs come from the Powerbook G3 discussion in the other thread. Could that
be the same bug?

Yes, most likely.

So you confirm this appears with 5.13 and not 5.12 ?

Can you check if they happen at commit c16728835
Can you check if they DO NOT happen at preceding commit c16728835~

Could you test without CONFIG_PPC_KUAP
Could you test with CONFIG_PPC_KUAP and CONFIG_PPC_KUAP_DEBUG

Thanks
Christophe