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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Thu, 4 Mar 2021 09:37:39 -0800
Message-ID: <CAKwvOd=TXBzBb-nJsAMHO99P7y7eOZRJB=veDtesPFNDPuhy2w@mail.gmail.com>
Subject: Re: [PATCH v3] MIPS: Make MIPS32_O32 depends on !CC_IS_CLANG
To:     Tiezhu Yang <yangtiezhu@loongson.cn>
Cc:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Nathan Chancellor <nathan@kernel.org>,
        linux-mips@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Xuefeng Li <lixuefeng@loongson.cn>
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On Thu, Mar 4, 2021 at 12:04 AM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> When building with Clang [1]:
>
> $ make CC=clang loongson3_defconfig
> $ make CC=clang
>
> there exists the following error:
>
>   Checking missing-syscalls for O32
>   CALL    scripts/checksyscalls.sh
> error: ABI 'o32' is not supported on CPU 'mips64r2'
> make[1]: *** [Kbuild:48: missing-syscalls] Error 1
> make: *** [arch/mips/Makefile:419: archprepare] Error 2
>
> This is a known bug [2] with Clang, as Simon Atanasyan said,
> "There is no plan on support O32 for MIPS64 due to lack of
> resources".

It's my hope we will fix the resourcing issue.  I'm working on that;
it's a non-technical challenge though.
Acked-by: Nick Desaulniers <ndesaulniers@google.com>

>
> It is not a good idea to remove CONFIG_MIPS32_O32=y directly
> in defconfig because GCC works, as Nathan said, the config
> should not even be selectable when building with Clang, so
> just make MIPS32_O32 depends on !CC_IS_CLANG.
>
> [1] https://www.kernel.org/doc/html/latest/kbuild/llvm.html
> [2] https://bugs.llvm.org/show_bug.cgi?id=38063
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> Acked-by: Nathan Chancellor <nathan@kernel.org>
> ---
>
> v3: Update the commit message suggested by Nathan, thank you!
>
>  arch/mips/Kconfig | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 3a38d27..f6ba59f 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -3318,6 +3318,8 @@ config SYSVIPC_COMPAT
>  config MIPS32_O32
>         bool "Kernel support for o32 binaries"
>         depends on 64BIT
> +       # https://bugs.llvm.org/show_bug.cgi?id=38063
> +       depends on !CC_IS_CLANG
>         select ARCH_WANT_OLD_COMPAT_IPC
>         select COMPAT
>         select MIPS32_COMPAT
> --
> 2.1.0
>
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-- 
Thanks,
~Nick Desaulniers