linux-kernel - Re: [PATCH v2] tools/build: Add clang cross-compilation flags to feature detection

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Date: Fri, 26 Apr 2024 12:31:17 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Jiri Olsa <olsajiri@...il.com>, Arnaldo Carvalho de Melo
 <acme@...hat.com>, Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc: linux-kernel@...r.kernel.org, Björn Töpel
 <bjorn@...osinc.com>, Nathan
 Chancellor <nathan@...nel.org>, Nick Desaulniers
 <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>, bpf@...r.kernel.org,
 Anders Roxell <anders.roxell@...aro.org>, llvm@...ts.linux.dev, Jiri Olsa
 <olsajiri@...il.com>
Subject: Re: [PATCH v2] tools/build: Add clang cross-compilation flags to
 feature detection

Jiri Olsa <olsajiri@...il.com> writes:

> On Thu, Nov 02, 2023 at 11:32:52AM +0100, Björn Töpel wrote:
>> From: Björn Töpel <bjorn@...osinc.com>
>> 
>> When a tool cross-build has LLVM=1 set, the clang cross-compilation
>> flags are not passed to the feature detection build system. This
>> results in the host's features are detected instead of the targets.
>> 
>> E.g, triggering a cross-build of bpftool:
>> 
>>   cd tools/bpf/bpftool
>>   make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- LLVM=1
>> 
>> would report the host's, and not the target's features.
>> 
>> Correct the issue by passing the CLANG_CROSS_FLAGS variable to the
>> feature detection makefile.
>> 
>> Fixes: cebdb7374577 ("tools: Help cross-building with clang")
>> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
>
> Acked-by: Jiri Olsa <jolsa@...nel.org>

Waking up the dead!

Arnaldo, Jean-Philippe: I'm still stung by what this patch fixes. LMK
what you need from me/this patch to pick it up.


Cheers,
Björn