Re: [PATCH] selftests/bpf: Elide a check for LLVM versions that can't compile it

[Toke HÃiland-JÃrgensen]

Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx> writes:

> The current stable LLVM BPF backend fails to compile the BPF selftests
> due to a compiler bug.  The bug has been fixed in trunk, but that fix
> hasn't landed in the binary packages I'm using yet (Fedora arm64).
> Without this workaround the tests don't compile for me.
>
> This patch triggers a preprocessor warning on LLVM versions that
> definitely have the bug.  The test may be conservative (ie, I'm not sure
> if 9.1 will have the fix), but it should at least make the current set
> of stable releases work together.
>
> See https://reviews.llvm.org/D69438 for more information on the fix.  I
> obtained the workaround from
> https://lore.kernel.org/linux-kselftest/aed8eda7-df20-069b-ea14-f06628984566@xxxxxxxxx/T/
>
> Fixes: 20a9ad2e7136 ("selftests/bpf: add CO-RE relocs array tests")
> Signed-off-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>

Having to depend on the latest trunk llvm to compile the selftests is
definitely unfortunate. I believe there are some tests that won't work
at all without trunk llvm (the fentry/fexit stuff comes to mind;
although I'm not sure if they'll fail to compile, just fail to run?).
Could we extend this type of checking to any such case?

-Toke