linux-kernel - Re: [PATCH] arm64: Make CPU_BIG_ENDIAN depend on !LD_IS

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Date:   Tue, 2 Feb 2021 12:51:33 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] arm64: Make CPU_BIG_ENDIAN depend on !LD_IS_LLD

On Tue, Feb 02, 2021 at 09:04:34AM +0100, Arnd Bergmann wrote:
> On Tue, Feb 2, 2021 at 3:25 AM Nathan Chancellor <nathan@...nel.org> wrote:
> >
> > Similar to commit 28187dc8ebd9 ("ARM: 9025/1: Kconfig: CPU_BIG_ENDIAN
> > depends on !LD_IS_LLD"), ld.lld does not support aarch64 big endian,
> > leading to the following build error when CONFIG_CPU_BIG_ENDIAN is
> > selected:
> >
> > ld.lld: error: unknown emulation: aarch64linuxb
> 
> While this is the original error message I reported, I think it would be
> better to explain that lld actually does support linking big-endian
> kernels but they don't boot, for unknown reasons.

That statement seems to contradict what Peter Smith says:

https://github.com/ClangBuiltLinux/linux/issues/1288#issuecomment-770693582

https://reviews.llvm.org/D58655#1410282

> I can send a patch to address the build error and mark big-endian
> as "depends on !LD_IS_LLD || COMPILE_TEST" to reflect that
> and help with randconfig testing.

I have no strong opinion on handling this though.

Cheers,
Nathan