Re: Bisected: RED State Exception in 4.5 on E420R

[Rob Gardner <rob.gardner@oracle.com>]

On 04/27/2016 02:01 PM, David Miller wrote:
> From: Rob Gardner <rob.gardner@oracle.com>
> Date: Wed, 27 Apr 2016 13:46:46 -0600
>
>> On 04/27/2016 01:36 PM, David Miller wrote:
>>> From: David Miller <davem@davemloft.net>
>>> Date: Wed, 27 Apr 2016 15:33:55 -0400 (EDT)
>>>
>>>> Therefore some other aspect of the change is causing problems and I
>>>> think that aspect is the size of the new code.
>>> Actually, there is a way to prove that this is indeed the bug, Meelis
>>> what does the entry for "swapper_tsb" say in your System.map file for
>>> a failing kernel?
>>>
>>> If it is not "0000000000408000", then that shows the bug.
>>>
>>
>> I've run into this situation, and the assembler emits a warning that
>> looks like this:
>>
>> arch/sparc/kernel/head_64.S:869: Warning: .space or .fill with
>> negative value, ignored
>>
>> I've worked around it by moving some of the includes to after the
>> ttable include. I think this is ok as long as code doesn't get
>> situated too far away for the branch displacement to handle.
> Maybe older binutils don't catch this properly.
>
> On my config here I definitely can see that the size is getting
> really close to the limit, and that's without all of the mentioned
> features enabled.
>
> Meanwhile, I'll keep working on the patch I said I'd do which trims
> down the size of all of this code.

Also, perhaps think about a way to make the assembler emit something 
fatal instead of a warning when this situation occurs? People tend to 
ignore warnings. ;)

Rob