[Ksummit-2012-discuss] [ATTEND] kernel core dump and "dying breath"

H. Peter Anvin hpa at zytor.com
Mon Jun 25 14:57:50 UTC 2012

On 06/25/2012 02:43 AM, Will Deacon wrote:
> Well, I think `prototype' is a bit strong but we did take a look at the
> feasibility of using QR codes for backtraces. The two problems were:
>    1. Even without any error correction, the QR code started to get pretty
>       large (and unreadable) after more than a few lines of backtrace. This
>       should be fairly easy to fix by encoding the data in a more sensible
>       manner rather than just verbatim (especially since a backtrace is
>       a well-structured log). Maybe you could even gzip the whole thing after
>       that too (then sell an android app to gunzip it :p)

Yes, this is the problem... the QR spec allows for large symbols, but 
unless you can find at least *one* decoder which can *reliably* decode 
large symbols photographed under non-ideal circumstances this is all 

>    2. Displaying the QR code on a panic could be problematic. We tried using
>       the ASCII option of libqrencode but we couldn't find any phone that
>       would read the result. So we need a way to get to the framebuffer once
>       we've sawn our head off (maybe this is easier with x86 and VGA modes?).

With KMS this shouldn't be a problem.


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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