[Intel-gfx] [PATCH] drm/i915: Enable fine-grained kcov instrumentation

[Joonas Lahtinen]

On to, 2016-08-04 at 07:30 +0100, Chris Wilson wrote:
> On Thu, Aug 04, 2016 at 09:12:07AM +0300, Joonas Lahtinen wrote:
> > 
> > On ke, 2016-08-03 at 20:38 +0100, Chris Wilson wrote:
> > > 
> > > In the next merge, we can build support for kcov at the individual file,
> > > or driver level. This is useful to filter out the noise when doing
> > > coverage test, i.e. we do get edges through code outside of i915.ko.
> > > 
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Umm, is not KCOV enabled by selecting KCOV and then instrumentation is
> > only disabled on select objects? "KCOV_INSTRUMENT_foo.o := n"?
> commit a4691deabf284a601149a067525759939cc563b2
> Author: Vegard Nossum <vegard.nossum at oracle.com>
> Date:   Tue Aug 2 14:07:30 2016 -0700
> 
>     kcov: allow more fine-grained coverage instrumentation
>     
>     For more targeted fuzzing, it's better to disable kernel-wide
>     instrumentation and instead enable it on a per-subsystem basis.  This
>     follows the pattern of UBSAN and allows you to compile in the kcov
>     driver without instrumenting the whole kernel.
>     
>     To instrument a part of the kernel, you can use either
>     
>         # for a single file in the current directory
>         KCOV_INSTRUMENT_filename.o := y
>     
>     or
>     
>         # for all the files in the current directory (excluding subdirectories)
>         KCOV_INSTRUMENT := y
>     
>     or
>     
>         # (same as above)
>         ccflags-y += $(CFLAGS_KCOV)
>     
>     or
>     
>         # for all the files in the current directory (including subdirectories)
>         subdir-ccflags-y += $(CFLAGS_KCOV)
> 
> 
> The commit itself adds KCOV_INSTRUMENT_ALL config target to enable
> kernel-wide coverage, with KCOV then just enabling the debug interface.

Could reference the patch in commit message if you especially want this
reviewed upfront. I see it could be merged after we get the commit to
our tree, too.

Regards, Joonas

> -Chris
> 
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation