linux-kernel - Re: [RFC] perf build: Allow passing extra Clang flags via EXTRA_CLANG

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Message-ID: <CADHxFxQyOBurB0LB9qRdc3DEDNU+vatqOybNdcizPnWZngiPZg@mail.gmail.com>
Date: Wed, 15 Oct 2025 19:47:04 +0800
From: hupu <hupu.gm@...il.com>
To: Leo Yan <leo.yan@....com>
Cc: Ian Rogers <irogers@...gle.com>, namhyung@...nel.org, peterz@...radead.org, 
	mingo@...hat.com, acme@...nel.org, mark.rutland@....com, 
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org, adrian.hunter@...el.com, 
	nathan@...nel.org, nick.desaulniers+lkml@...il.com, morbo@...gle.com, 
	justinstitt@...gle.com, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: Re: [RFC] perf build: Allow passing extra Clang flags via EXTRA_CLANG_FLAGS

Hi Leo,
Thank you for your reply.

On Wed, Oct 15, 2025 at 5:30 PM Leo Yan <leo.yan@....com> wrote:
>
> Have you installed the GCC cross packages ?
>
>  $ sudo apt-get install gcc-aarch64-linux-gnu g++-aarch64-linux-gnu
>  $ sudo apt-get install libc6-dev-aarch64-cross linux-libc-dev-aarch64-cross
>  $ sudo apt-get install libc6-dev-arm64-cross linux-libc-dev-arm64-cross
>
> My understanding is arm64 cross compilation tries to find headers in the
> path /usr/aarch64-linux-gnu/include/ (I confirmed this on Ubuntu/Debian
> distros).  After install GCC cross packages, the headers should appear
> in the folder.
>

I hadn’t installed the packages you mentioned earlier, but after
running the installation commands you provided, I was indeed able to
successfully build perf.

In fact, I’m currently working on creating an SDK package, which
includes a cross-toolchain that I built myself using crosstool-NG. My
initial idea was to install certain third-party libraries (such as the
packages you mentioned) into the cross-toolchain’s sysroot directory.
With this approach, even when developing on different host machines,
we could simply specify the header search path (pointing to the
cross-toolchain’s sysroot directory) during compilation, and the build
should succeed without requiring any additional package installation
on the system.

Based on this, I think allowing users to extend some options via
EXTRA_CLANG_FLAGS could be a flexible way to handle such cases.
However, this is just my personal thought and might not be entirely
correct, so I’d like to hear your advice.

Thanks，
hupu