Re: Firmware debugging patches?

[Ben Greear <greearb@candelatech.com>]

On 06/08/2014 01:35 AM, Kalle Valo wrote:
> Ben Greear <greearb@candelatech.com> writes:
>
>>>> Perhaps the time-stamp is good enough?  I don't see a need for
>>>> a uuid, but perhaps I am missing something?
>>>
>>> UUID is supposed to be unique. If we use walltime there's no guarantee
>>> that the clock is correct and if we use local_clock() (my preference) it
>>> will be reset after every boot.
>>>
>>> I just think using something like UUID is more robust. Especially if one
>>> implements an automatic crash dump collector from thousands of deployed
>>> APs, having an UUID makes it a lot easier to manage.
>>
>> I can add since-boot timestamp as well.  Time-since-boot is less likely
>> to be unique than wall-time, and for systems that do have proper wall-time
>> clock configured, I think that provides some useful info.  (Would be interesting
>> if all APs in a stadium crashed near the same time, for instance.)
>>
>> I was thinking we should not add a MAC to the dump, for privacy concerns,
>> but whatever user-space tools gather the dump could add MAC if user perfers.
>
> The MAC addresses can be extracted from the target memory anyway so I
> don't see harm from including that in the dump. Is it even possible to
> address all privacy issues when dealing with firmware dumps?

It would be more difficult to find it in debug-log messages (and in most cases,
it is probably not the debug-log at all).  Probably not in the stack dump
most of the time either.

I'm not sure it will be in the BSS regions or not.  I have no plans to dump the
non-bss RAM on the firmware because I have no tools that can decode it anyway,
so probably the patches I've posted so far are relatively OK as far as privacy
is concerned.  Someone who is very paranoid should not be using this feature
anyway.


>> With time-of-day, time-since-boot, and MAC, each dump should be unique.
>
> But I would like to easily match from kernel log that the crash dump
> matches with log. uuid would provide that in a simple way (check that
> the uuid in the log matches with the uuid in the dump). What's so bad
> from using uuid?

Just tell me how you want me to create the uuid and I'll do so.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com