On Tue, Dec 1, 2020 at 12:19 AM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Mon, Nov 30, 2020 at 12:12:39PM -0800, Nick Desaulniers wrote:
On Wed, Nov 25, 2020 at 10:38 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
Is the mainline 4.9 tree supposed to work with clang? I didn't think that upstream effort started until 4.19 or so.
(For historical records, separate from the initial bug report that started this thread)
I consider 785f11aa595b ("kbuild: Add better clang cross build support") to be the starting point of a renewed effort to upstream clang support. 785f11aa595b landed in v4.12-rc1. I think most patches landed between there and 4.15 (would have been my guess). From there, support was backported to 4.14, 4.9, and 4.4 for x86_64 and aarch64. We still have CI coverage of those branches+arches with Clang today. Pixel 2 shipped with 4.4+clang, Pixel 3 and 3a with 4.9+clang, Pixel 4 and 4a with 4.14+clang. CrOS has also shipped clang built kernels since 4.4+.
Thanks for the info. Naresh, does this help explain why maybe testing these kernel branches with clang might not be the best thing to do?
On the contrary, I think it's very much worthwhile to test these branches with Clang. Particularly since CrOS is shipping x86_64 devices built with Clang since 4.4.y. This looks like a problem that's potentially been fixed but the fix not yet identified and backported. It would be good for us to identify and fix the issue before it becomes a problem for CrOS.
Though, it looks like CrOS just skipped 4.9...? Looking at: https://chromium.googlesource.com/chromiumos/third_party/kernel/+refs I don't see a chromeos-4.9 branch.
That said, I still find such reports helpful to track.