[Ovmsdev] OVMS v2 Memory/Settings Corruption

[Michael Balzer]

There's no memory management in the module, there's too few RAM
available to do dynamic allocations.

All buffers are static, the error can be some pointer corruption or
missing length check / end of string check.

A stack overflow could also be possible, the software stack is 256 bytes
(1 page). As there's not enough ROM left to support the crash debug
framework anymore in the Twizy build, I cannot tell if that happens again.

Julien, you could try a reduced build with crash debug recording enabled...

Regards,
Michael


Am 28.11.2016 um 22:00 schrieb Greg D.:
> Ah!  That sounds much more likely.
>
> Is there an error (timeout) path that might be freeing the buffer when
> it's still in use?
>
> Greg.
>
>
> Michael Balzer wrote:
>> Hi Greg, welcome :)
>>
>> Juliens parameter #0 has been overwritten with "Topping o", which is
>> part of the charge status message ("Topping off").
>>
>> So it's much more likely we've got a buffer corruption bug that's
>> triggered by (maybe) bad connectivity situations.
>>
>> Regards,
>> Michael
>>
>>
>> Am 28.11.2016 um 06:38 schrieb Greg D.:
>>> Hi all,
>>>
>>> New here, so this may be totally off the wall.
>>>
>>> I notice that the first example, with a "5" going to a "k", it may
>>> be more easily explained as a bit */shift/* instead of a set of
>>> flips.  Is there anywhere in the system where the bytes are clocked
>>> serially between devices, where there may be some marginal timing?
>>>
>>> Just a thought.
>>>
>>> Greg.
>>>
>>>
>>> Mark Webb-Johnson wrote:
>>>> $ perl -e 'printf "%08b\n",ord("5");'
>>>> 00110101
>>>> $ perl -e 'printf "%08b\n",ord("k");'
>>>> 01101011
>>>> $ perl -e 'printf "%08b\n",ord("8");'
>>>> 00111000
>>>> $ perl -e 'printf "%08b\n",ord("Z");'
>>>> 01011010
>>>>
>>>> Strange. Seems more than a simple bit flip. I haven’t seen this myself, or heard of it much from other users.
>>>>
>>>> Is the Twizy code using EEPROM for anything other than settings storage? I know that there are a very limit number of write cycles into that EEPROM space.
>>>>
>>>> I did some googling, but all I can find is corruption during writing (either power down, or interrupt during write). But, for our case of very very rare EEPROM writes, that shouldn’t be an issue.
>>>>
>>>> Regards, Mark.
>>>>
>>>>> On 25 Nov 2016, at 5:47 AM, Michael Balzer <dexter at expeedo.de> wrote:
>>>>>
>>>>> The EEPROM data loss is a known issue, and I'm afraid there's nothing we can do about that. It seems to be a bug in the PIC18.
>>>>>
>>>>> Regards
>>>>> Michael
>>>>>
>>>>> Am 24.11.2016 um 22:10 schrieb Julien Banchet:
>>>>>> Hi all,
>>>>>>
>>>>>> Thanks to Michaels last message to remind me to ask a question here:
>>>>>>
>>>>>> Since a few months, maybe a bit more because it happens only once in a while, I have noticed I wasn't receiving the SMS alerts (feature on SMSIP mode) , and sending a "Stats?" only gave me the nasty access denied answer.
>>>>>>
>>>>>> It turns out, using the application, I noticed that the phone number was getting corrupted (afaik, it's the only setting affected)
>>>>>>
>>>>>> Normally: "+33651886877" it became "+336k1886877" or "+33651886Z77" etc... like a solar flare bit flip !_______________________________________________
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>>>
>>>
>>>
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>>
>> -- 
>> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
>> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
>>
>>
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>
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-- 
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26

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