Building the Linux kernel with Clang and LLVM
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From: "Arnd Bergmann" <arnd@arndb.de>
To: "Nathan Chancellor" <nathan@kernel.org>,
	"Arnd Bergmann" <arnd@kernel.org>
Cc: "Masahiro Yamada" <masahiroy@kernel.org>,
	"Nicolas Schier" <nicolas@fjasle.eu>,
	"Nick Desaulniers" <nick.desaulniers+lkml@gmail.com>,
	"Bill Wendling" <morbo@google.com>,
	"Justin Stitt" <justinstitt@google.com>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	llvm@lists.linux.dev
Subject: Re: [PATCH] kbuild: hdrcheck: fix cross build with clang
Date: Fri, 21 Feb 2025 22:39:59 +0100	[thread overview]
Message-ID: <4045e93b-3352-428e-91c6-a86dc8f9c8bd@app.fastmail.com> (raw)
In-Reply-To: <20250221212603.GA3561672@ax162>

On Fri, Feb 21, 2025, at 22:26, Nathan Chancellor wrote:
> On Fri, Feb 21, 2025 at 10:20:07PM +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>> 
>> The headercheck tries to call clang with a mix of compiler arguments
>> that don't include the target architecture. When building e.g. x86
>> headers on arm64, this produces a warning like
>> 
>>    clang: warning: unknown platform, assuming -mfloat-abi=soft
>> 
>> Add in the CLANG_FLAGS, which contain the target, in order to make it
>> build properly.
>> 
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> This looks like a similar problem as the one fixed by
> commit 1b71c2fb04e7 ("kbuild: userprogs: fix bitsize and target
> detection on clang"), should it be addressed in the same manner
> (especially since I think the Fixes commit would be the same)? Given
> that the filter expression is the same, maybe it would be possible to
> unify them but that could happen as a follow up.

My bad, I actually had an old patch that addressed both issues
and then dropped it when the Thomas' patch made it into linux-next
but ended up picking my old change for usr/include/Makefile instead
of trying to understand the difference.

I'll send a v2 after some more build testing.

     Arnd

      reply	other threads:[~2025-02-21 21:40 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-21 21:20 [PATCH] kbuild: hdrcheck: fix cross build with clang Arnd Bergmann
2025-02-21 21:26 ` Nathan Chancellor
2025-02-21 21:39   ` Arnd Bergmann [this message]

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