linux-kernel - Re: [PATCH] MIPS: Add comment about CONFIG_MIPS32_O32 in loongson3

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Date:   Fri, 5 Mar 2021 10:22:47 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH] MIPS: Add comment about CONFIG_MIPS32_O32 in
 loongson3_defconfig when build with Clang



在 2021/3/5 上午7:08, Maciej W. Rozycki 写道:
> On Thu, 4 Mar 2021, Tiezhu Yang wrote:
> 
>> 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".
> 
>   Huh?  Is that a joke?  From the o32 psABI's point of view a MIPS64 CPU is
> exactly the same as a MIPS32 one (for whatever ISA revision), so there's
> nothing to support there really other than the CPU/ISA name.

Clang treat MIPS32 as a different backend so we may need some extra 
effort....

TBH it is a toolchain issue and kernel workaround seems bogus.

 From my point view we can "s/mips64r2/mips32r2" when doing syscall checks
to workaround clang issue instead of disable it for kernel.

Thanks.

- Jiaxun

> 
>   As much as I dislike all the hacks the Clang community seems to come up
> with for the shortcomings of their tool there has to be a saner workaround
> available rather than forcibly disabling support for the o32 ABI with
> CONFIG_64BIT kernels, but the report is missing the compiler invocation
> line triggering the issue (V=1 perhaps?), which should be included with
> any commit description anyway, so I can't suggest anything based on the
> limited information provided.
> 
>    Maciej
>