linux-kernel - Re: [PATCH] ARM: Allow pre-ARMv5 builds with ld.lld 16.0.0 and newer

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Date:   Fri, 27 Jan 2023 22:56:06 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Nathan Chancellor" <nathan@...nel.org>,
        "Russell King" <linux@...linux.org.uk>
Cc:     "Nick Desaulniers" <ndesaulniers@...gle.com>,
        "Tom Rix" <trix@...hat.com>, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev
Subject: Re: [PATCH] ARM: Allow pre-ARMv5 builds with ld.lld 16.0.0 and newer

On Wed, Jan 18, 2023, at 20:22, Nathan Chancellor wrote:
> Commit 6a7ee50f8f56 ("ARM: disallow pre-ARMv5 builds with ld.lld")
> prevented v4 or v4t kernels when ld.lld will link the kernel due to
> inserting unsupported blx instructions.
>
> ld.lld has been fixed in current main (16.0.0) to avoid inserting these
> instructions by inserting position independent thunks instead. Allow
> these configurations to be enabled when ld.lld 16.0.0 is used to link
> the kernel.
>
> Additionally, add a link to the upstream LLVM issue so that the reason
> for this dependency is clearly documented.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/964
> Link: 
> https://github.com/llvm/llvm-project/commit/6f9ff1beee9d12aca0c9caa9ae0051dc6d0a718c
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Thanks a lot for getting this fixed!

I gave this a spin on my randconfig build setup, which showed
nothing unusual.

Tested-by: Arnd Bergmann <arnd@...db.de>

Please add this to Russell's patch tracker.

      Arnd