Re: [PATCH v2 00/20] Unify code coverage and add Clang source-based coverage with MC/DC

[Peter Oberparleiter]

On 03.11.2026 02:52, Sasha Levin wrote:
> The previous postings of Clang's source-based code coverage [1][2] drew
> objections [3][4]: rather than a third coverage implementation with its
> own interface next to gcov and KCOV, reviewers asked for a unified
> coverage interface, and for coverage instrumentation to honour noinstr.
> This series first restructures the existing coverage support into one
> framework, then adds source-based coverage and MC/DC as part of it.

Thanks for driving these improvements to the kernel coverage
infrastructure! The overall approach taken to unify the different
backends looks sane to me, and I'm looking forward to seeing this
integrated!

I successfully tested the gcov-backend on s390 with GCC 16.1.0, GCC
15.2.0 and latest Clang 24 (git).

[...]

> - Runtime interface: /sys/kernel/debug/coverage/, with "backend" naming
>   the backend and its features, "reset" resetting its data, and the
>   backend's data files. The existing gcov and kcov entries stay where
>   they are, for lcov and syzkaller, and are linked from there.

Just as a FYI - I found a minor incompatibility when using lcov with the
series applied where it fails to automatically determine the kernel base
directory due to the changed location of gcov-kernel base code, but
that's nothing that should affect the kernel series. The issue can be
worked around by specifying the path manually and I'm planning to
address this with a corresponding lcov change once the series is integrated.

-- 
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D