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

[Zachary Leaf]

On 13/02/2023 14:30, Björn Töpel wrote:
> 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.

Similar use case. There also seems to be a lot of issues building these
tests out of tree.

I have some potential fixes up to 6.1 but linux-next seems to have
introduced a few more issues on top.

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