linux-kernel - Re: jump_label: move 'asm goto' support test to Kconfig

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Message-ID: <CAK7LNASWScb7Qt0kmV8RyBdix2GPA24gv=eRNYVWu5dGGePbfQ@mail.gmail.com>
Date:   Thu, 3 Jan 2019 09:35:49 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Sedat Dilek <sedat.dilek@...il.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Will Deacon <will.deacon@....com>,
        "David S . Miller" <davem@...emloft.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-xtensa@...ux-xtensa.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        X86 ML <x86@...nel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: jump_label: move 'asm goto' support test to Kconfig

On Wed, Jan 2, 2019 at 9:14 PM Sedat Dilek <sedat.dilek@...il.com> wrote:
>
> Hi,
>
> I was not aware that CONFIG_JUMP_LABEL Kconfig setting depends on the
> support of asm-goto.
>
> Currently, I am doing experiments with clang-7 and a snapshot of
> clang-8 on Linux/x86.
> These compilers have no asm-goto support.
>
> What is your recommendation for Linux >= v4.20?
> I am asking as it is possible to set CONFIG_JUMP_LABEL=y when
> compiling with clang - which has no effect.
> This is confusing.
>
> Thanks, this patch makes things clearer and protects users from
> setting "wrong" in the sense of non-functional settings.
>
> I have tested this against recent Linus tree where kbuild/kconfig Git
> pulls were latest commits.
>
> Tested-by: Sedat Dilek <sedat.dilek@...il.com> [ x86 with LLVM/Clang
> v7 and v8 (snapshot) ]


Which part was tested?

x86 kernel cannot be compiled with Clang
since it lacks the asm-goto support.


$ make CC=clang
Compiler lacks asm-goto support.
arch/x86/Makefile:293: recipe for target 'checkbin' failed
make: *** [checkbin] Error 1






-- 
Best Regards
Masahiro Yamada