Re: Your System ate a SPARC! Gah! in map_pages()

[Helge Deller <deller@gmx.de>]

On 12/10/21 20:53, Sven Schnelle wrote:
> Helge Deller <deller@gmx.de> writes:
>
>> On 12/7/21 23:07, John David Anglin wrote:
>>> On 2021-12-05 3:46 p.m., Helge Deller wrote:
>>>>>   10574:       43 ff ff 40     ldb 1fa0(sr3,r31),r31
>>>> This IIR is strange. We most likely don't touch userspace at this stage
>>>> when the kernel boots, and...
>>> I'm thinking IIR is sometimes unreliable.  I see the same value
>>> printed for the tst-minsigstksz-5 fault yet the actual fault
>>> instruction was "ldi 1,r25".
>>
>> Good finding.
>> It seems to be at least always unreliable if we get a trap 7 (Instruction access rights).
>> In that case the CPU couldn't execute the instruction due to missing
>> execute permissions. I believe the CPU simply didn't fetched the
>> instruction and as such has stale content in IIR.
>>
>> I'm sending a patch to the list which marks IIR with a magic value in that case.
>
> The same might happen with ISR and IOR - i wonder whether we should take
> a few bit in struct pt_regs, store the interruption code there, and only
> display the fields that are valid for a certain code? pt_regs has an
> unused pad0 field (at least i think it's unused...) which we could use.
> What's your take on this? I would prefer this over some magic values in
> the oops output...

It's a good idea, but do we really want to see such errors often?
So, I think it's not worth the efforts. Showing some magic "baadfood" is ok for me.
But if you like you can code it...

Helge

Btw, it seems I currently have vDSO (32bit) working with signal return code :-)