[PATCH bpf-next] selftests/bpf: Cross-compile bpftool

[Björn Töpel]

Björn Töpel <bjorn at kernel.org> writes:

> From: Björn Töpel <bjorn at rivosinc.com>
>
> When the BPF selftests are cross-compiled, only the a host version of
> bpftool is built. This version of bpftool is used to generate various
> intermediates, e.g., skeletons.
>
> The test runners are also using bpftool. The Makefile will symlink
> bpftool from the selftest/bpf root, where the test runners will look
> for the tool:
>
>   | ...
>   | $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \
>   |    $(OUTPUT)/$(if $2,$2/)bpftool
>
> There are two issues for cross-compilation builds:
>
>  1. There is no native (cross-compilation target) build of bpftool
>  2. The bootstrap variant of bpftool is never cross-compiled (by
>     design)
>
> Make sure that a native/cross-compiled version of bpftool is built,
> and if CROSS_COMPILE is set, symlink to the native/non-bootstrap
> version.

...and the grand master plan is to add BPF CI support for riscv64, where
this patch a prerequisite to [1]. I would suspect that other platforms
might benefit from cross-compilation builds as well.

[1] https://github.com/kernel-patches/vmtest/pull/194