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

Zachary Leaf [off-list ref] writes:

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

quoted

Björn Töpel [off-list ref] writes:

quoted

From: Björn Töpel <redacted>

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.

Ah, yes. FWIW, the BPF CI builds the selftests *in-tree*, so with this
patch (and my PRs) the BPF CI is capable of cross-compiling.


Björn