Re: [Xen-devel] [PATCH v3] gcov: add new interface and 3.4 and 4.7 format support

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Oct 12, 2016 at 02:40:08PM +0100, Wei Liu wrote:
> On Wed, Oct 12, 2016 at 09:29:04AM -0400, Konrad Rzeszutek Wilk wrote:
> [...]
> > > 
> > > Wouldn't it be just as easy, and more useful, to set a "has been
> > > livepatched" flag, and return errors for all gcov hypercalls if its' set?
> > > 
> > > I would expect most users to want to build a single hypervisor that can
> > > be used for both gcov testing and live patching (under different
> > > circumstances).
> > 
> > I actually would welcome livepatching and gcov to see if the test-cases I 
> > wrote
> > cover most of the code.
> > 
> 
> I don't follow. Gcov doesn't give you a call graph -- if that's what
> you're after.

It gives me an idea which functions/branches have run (not the livepatch
itself - just the infrastructure around adding a livepatch, doing ELF checks, 
etc).

And more importantly - which ones haven't run and need some more test-cases.

> 
> > Adding in checking livepatch (common/livepatch.c: prepare_payload) to 
> > examine
> > the .gcov_info and see if it matches the hypervisor one, is fine too.
> > 
> 
> This then involves a non-trivial amount of work to figure out all the
> corner cases. It's better to defer that to a later stage.

Sure thing. And the !LIVEPATCH is fine for now. I just need to get an idea
of what this would entail so it can get done.
> 
> Wei.
> 
> > > 
> > >  -George
> > > 

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