netdev - Re: [PATCH kselftest] fix single bpf test

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Message-ID: <c685c171-0d2d-4ef1-82ca-386c3a2e3df6@sirena.org.uk>
Date: Mon, 25 Nov 2024 13:11:46 +0000
From: Mark Brown <broonie@...nel.org>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: Jiayuan Chen <mrpre@....com>, linux-kselftest@...r.kernel.org,
	song@...nel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, martin.lau@...ux.dev, andrii@...nel.org,
	ast@...nel.org, kpsingh@...nel.org, jolsa@...nel.org
Subject: Re: [PATCH kselftest] fix single bpf test

On Fri, Nov 22, 2024 at 08:14:58AM -0700, Shuah Khan wrote:

> The commit 7a6eb7c34a78 went in 4 years ago? DO we have a better
> story for the LLVM tool chain to get rid of skipping bpf and sched_ext?

> Running make -C tools/testing/selftests/bpf/ gave me the following error.
> Does this mean we still can't include bpf in default run?

> make -C tools/testing/selftests/bpf/
> make: Entering directory '/linux/linux_6.12/tools/testing/selftests/bpf'
> 
> Auto-detecting system features:
> ...                                    llvm: [ OFF ]

The toolchain is in a better place now and we can run with released LLVM
versions.  The detection above is still needed since the LLVM version
needed is a bit newer than the version needed for the kernel itself,
it's LLVM 18 for BPF, and not everyone has LLVM.

>   GEN     /linux/linux_6.12/tools/testing/selftests/bpf/tools/build/bpftool/vmlinux.h
> libbpf: failed to find '.BTF' ELF section in /linux/linux_6.12/vmlinux
> Error: failed to load BTF from /linux/linux_6.12/vmlinux: No data available
> make[1]: *** [Makefile:209: /linux/linux_6.12/tools/testing/selftests/bpf/tools/build/bpftool/vmlinux.h] Error 195
> make[1]: *** Deleting file '/linux/linux_6.12/tools/testing/selftests/bpf/tools/build/bpftool/vmlinux.h'
> make: *** [Makefile:369: /linux/linux_6.12/tools/testing/selftests/bpf/tools/sbin/bpftool] Error 2
> make: Leaving directory '/linux/linux_6.12/tools/testing/selftests/bpf'

This bit still needs some attention - the build needs a kernel binary
with BTF information built in via CONFIG_DEBUG_INFO_BTF.  That is
enabled by the config fragment for BTF tests but it's not compatible
with the arm64 defconfig since that sets CONFIG_DEBUG_INFO_REDUCED which
isn't compatible with _BTF, and in general having it missing should be
handled a bit more gracefully.  I believe some of the tests would run
happily without the BTF information.  

TBH I'm a bit surprised we even tried to do this bit with LLVM not
available...

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