On Sat, 6 Feb 2021 at 14:10, Guillaume Tucker <[email protected]> wrote: > > On 05/02/2021 12:05, Ard Biesheuvel wrote: > > On Fri, 5 Feb 2021 at 09:21, Ard Biesheuvel <[email protected]> wrote: > >> > >> On Thu, 4 Feb 2021 at 22:31, Guillaume Tucker > >> <[email protected]> wrote: > >>> > >>> On 04/02/2021 18:23, Nick Desaulniers wrote: > >>>> On Thu, Feb 4, 2021 at 10:12 AM Nathan Chancellor <[email protected]> > >>>> wrote: > >>>>> > >>>>> On Thu, Feb 04, 2021 at 10:06:08AM -0800, 'Nick Desaulniers' via Clang > >>>>> Built Linux wrote: > >>>>>> On Thu, Feb 4, 2021 at 8:02 AM Ard Biesheuvel <[email protected]> wrote: > >>>>>>> > >>>>>>> On Thu, 4 Feb 2021 at 16:53, Guillaume Tucker > >>>>>>> <[email protected]> wrote: > >>>>>>>> > >>>>>>>> On 04/02/2021 15:42, Ard Biesheuvel wrote: > >>>>>>>>> On Thu, 4 Feb 2021 at 12:32, Guillaume Tucker > >>>>>>>>> <[email protected]> wrote: > >>>>>>>>>> > >>>>>>>>>> Essentially: > >>>>>>>>>> > >>>>>>>>>> make -j18 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LLVM=1 > >>>>>>>>>> CC="ccache clang" zImage > >>>>>> > >>>>>> This command should link with BFD (and assemble with GAS; it's only > >>>>>> using clang as the compiler. > >>>>> > >>>>> I think you missed the 'LLVM=1' before CC="ccache clang". That should > >>>>> use all of the LLVM utilities minus the integrated assembler while > >>>>> wrapping clang with ccache. > >>>> > >>>> You're right, I missed `LLVM=1`. Adding `LD=ld.bfd` I think should > >>>> permit fallback to BFD. > >>> > >>> That was close, except we're cross-compiling with GCC for arm. > >>> So I've now built a plain next-20210203 (without Ard's fix) using > >>> this command line: > >>> > >>> make LD=arm-linux-gnueabihf-ld.bfd -j18 ARCH=arm > >>> CROSS_COMPILE=arm-linux-gnueabihf- LLVM=1 CC="ccache clang" zImage > >>> > >>> I'm using a modified Docker image gtucker/kernelci-build-clang-11 > >>> with the very latest LLVM 11 and gcc-8-arm-linux-gnueabihf > >>> packages added to be able to use the GNU linker. BTW I guess we > >>> should enable this kind of hybrid build setup on kernelci.org as > >>> well. > >>> > >>> Full build log + kernel binaries can be found here: > >>> > >>> > >>> https://storage.staging.kernelci.org/gtucker/next-20210203-ard-fix/v5.10-rc4-24722-g58b6c0e507b7-gtucker_single-staging-41/arm/multi_v7_defconfig/clang-11/ > >>> > >>> And this booted fine, which confirms it's really down to how > >>> ld.lld puts together the kernel image. Does it actually solve > >>> the debate whether this is an issue to fix in the assembly code > >>> or at link time? > >>> > >>> Full test job details for the record: > >>> > >>> https://lava.collabora.co.uk/scheduler/job/3176004 > >>> > >> > >> > >> So the issue appears to be in the way the linker generates the > >> _kernel_bss_size symbol, which obviously has an impact, given that the > >> queued fix takes it into account in the cache_clean operation. > >> > >> On GNU ld, I see > >> > >> 479: 00065e14 0 NOTYPE GLOBAL DEFAULT ABS _kernel_bss_size > >> > >> whereas n LLVM ld.lld, I see > >> > >> 433: c1c86e98 0 NOTYPE GLOBAL DEFAULT ABS _kernel_bss_size > >> > >> and adding this value may cause the cache clean to operate on unmapped > >> addresses, or cause the addition to wrap and not perform a cache clean > >> at all. > >> > >> AFAICT, this also breaks the appended DTB case in LLVM, so this needs > >> a separate fix in any case. > > > > I pushed a combined branch of torvalds/master, rmk/fixes (still > > containing my 9052/1 fix) and this patch to my for-kernelci branch > > > > https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/ > > > > Guillaume, > > > > It seems there is no Clang-11 coverage there, right? Mind giving this > > branch a spin? If this fixes the regressions, we can get these queued > > up. > > That's right, Clang builds are only enabled on linux-next and > mainline at the moment. We could enable it on any other branch > where it makes sense. How about just the main defconfig for arm, > arm64 and x86_64 on your ardb/for-kernelci branch? >
Yes, please. > For now I've run another set of builds with clang-11 and got the > following test results with your branch on staging: > > > https://staging.kernelci.org/test/job/ardb/branch/for-kernelci/kernel/v5.11-rc6-146-g923ca344043a/plan/baseline/ > > which are all passing. > > I'll reply to the thread with your patch to confirm. > Excellent, thanks a lot.
