Re: [BISECTED] kexec regression on PowerBook G4

[Christophe Leroy <christophe.leroy@c-s.fr>]

Hi

Le 24/05/2019 à 00:23, Aaro Koskinen a écrit :
> Hi,
> 
> On Thu, May 23, 2019 at 08:58:11PM +0200, Christophe Leroy wrote:
>> Le 23/05/2019 à 19:27, Aaro Koskinen a écrit :
>>> On Thu, May 23, 2019 at 07:33:38AM +0200, Christophe Leroy wrote:
>>>> Ok, the Oops confirms that the error is due to executing the kexec control
>>>> code which is located outside the kernel text area.
>>>>
>>>> My yesterday's proposed change doesn't work because on book3S/32, NX
>>>> protection is based on setting segments to NX, and using IBATs for kernel
>>>> text.
>>>>
>>>> Can you try the patch I sent out a few minutes ago ?
>>>> (https://patchwork.ozlabs.org/patch/1103827/)
>>>
>>> It now crashes with "BUG: Unable to handle kernel instruction fetch"
>>> and the faulting address is 0xef13a000.
>>
>> Ok.
>>
>> Can you try with both changes at the same time, ie the mtsrin(...) and the
>> change_page_attr() ?
>>
>> I suspect that allthough the HW is not able to check EXEC flag, the SW will
>> check it before loading the hash entry.
> 
> Unfortunately still no luck... The crash is pretty much the same with both
> changes.

Right. In fact change_page_attr() does nothing because this part of RAM 
is mapped by DBATs so v_block_mapped() returns not NULL.

So, we have to set an IBAT for this area. I'll try and send you a new 
patch for that before noon (CET).

Christophe