linux-kernel - Re: next/master bisection: baseline.login on rk3288-rock2-square

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Message-ID: <253b2987-c8e9-fcb6-c1b9-81e765c0cc2a@collabora.com>
Date:   Thu, 4 Feb 2021 21:31:06 +0000
From:   Guillaume Tucker <guillaume.tucker@...labora.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     "kernelci-results@...ups.io" <kernelci-results@...ups.io>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Nicolas Pitre <nico@...xnic.net>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: next/master bisection: baseline.login on rk3288-rock2-square

On 04/02/2021 18:23, Nick Desaulniers wrote:
> On Thu, Feb 4, 2021 at 10:12 AM Nathan Chancellor <nathan@...nel.org> 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 <ardb@...nel.org> wrote:
>>>>
>>>> On Thu, 4 Feb 2021 at 16:53, Guillaume Tucker
>>>> <guillaume.tucker@...labora.com> wrote:
>>>>>
>>>>> On 04/02/2021 15:42, Ard Biesheuvel wrote:
>>>>>> On Thu, 4 Feb 2021 at 12:32, Guillaume Tucker
>>>>>> <guillaume.tucker@...labora.com> 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

Hope that helps,
Guillaume