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Re: [PATCH 0/2] x86/shadow: address two Coverity issues


  • To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Wed, 13 Oct 2021 17:10:00 +0100
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  • Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 13/10/2021 16:36, Jan Beulich wrote:
> It's not clear to me why the tool spotted them now and not before,

Several reasons.

The Coverity backend is a software product just like everything else. 
IIRC, it releases quarterly.

"If something's free, then you are the product".  The value of offering
free scanning of open source codebases comes from us (the free users)
integrating a massive corpus of code into Coverity's system, upon which
they can evaluate the effectiveness of new heuristics.


Second, and far more likely in this case, "x86/mm: avoid building
multiple .o from a single .c file".  Coverity has always choked on that
in Xen, because it's intermediate database is keyed on source file with
latest takes precedent, so we were only seeing the 4-level case previously.


And to also answer your question from patch 1 here, there are upper time
and complexity bounds on all analysis, because scanning is an
exponential problem with the size of the source file.  I don't know
exactly where the cutoffs are, and I fear that some of our larger files
never have later functions looked at.

~Andrew




 


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