Re: [PATCH v3 0/4] selftests: shared lib.bpf.mk for building BPF progs and skeletons

[Ziyang Men <ziyang.meme@gmail.com>]

Hi Reviewers,

Just want to follow-up on this patch series. Please let me know the possible
issues and I will fix them.

Thanks very much!

Best,
Ziyang

On Fri, Aug 14, 2026 at 12:50:50AM -0700, Ziyang Men wrote:
>This series re-factors the bpf-related toolchain for selftests, which
>currently duplicated across selftests/{bpf,sched_ext,hid}/. Unify them
>into a single includable fragment, the tools/testing/selftests/lib.bpf.mk,
>and wires up three consumers. We believe this will simplify the work for
>configuring selftests with the bpf, for both the existing and future ones.
>
>Patch 1 adds lib.bpf.mk mentioned above.
>
>Patch 2 adds a new selftest, selftests/cgroup/test_memcg_stat_cross_cpu,
>which checks the cgroup flush happens correctly by comparing the bpf
>read value matches the file reading. Existing test
>bpf/cgroup_iter_memcg only ensures whether the number is non-zero, which
>is trivial in some cases.
>
>Patches 3 and 4 replace the duplicated parts in selftests/{hid,
>sched_ext} with the lib.bpf.mk
>
>===
>Changes since v2:
>For shared Makefile:
>- The lib.bpf.mk now use the USERCFLAGS (and USERLDFLAGS) to extend the
>  CFLAGS and LDFLAGS.
>- OPT_FLAGS/RELEASE and EXTRA_CFLAGS now reach the libbpf and bpftool
>  sub-makes as well.
>- One rule per BPF source instead of a vpath, which is global and also
>  applied to the caller's own %.c rules.
>- HOSTCC/HOSTLD come from lib.mk instead of including Makefile.include,
>  which also rewrote the caller's AR, LD and CFLAGS.
>- A missing vmlinux is reported by the recipe rather than at parse time,
>  so "make clean" still works without BTF.
>
>For cgroup selftest:
>- Only one cgroup tree is created, one flush is performed, follows by
>  bpf read and file read.
>- More common cgroup functions e.g., cg_read_key_long() and
>  value_close(), are used in the selftests.
>- Use cpu_set_t rather than manually allocated cpu lists.
>- Use test_memcontrol.c's anon allocator and moving it into cgroup_util.
>- Other suggestion from the review.
>
>Others:
>- Bot reviews are fixed.
>
>===
>Changes since v1:
>  - Generalized lib.bpf.mk (source layout/suffix, extra hdrs/cflags,
>    skeleton suffix, subskeletons, configurable output dirs) so it can
>    serve hid and sched_ext, not just cgroup.
>  - Added patch 3 (hid) and patch 4 (sched_ext), converting those folders
>    to the shared fragment.
>
>Ziyang Men (4):
>  selftests: add shared lib.bpf.mk to build BPF progs and skeletons
>  selftests/cgroup: add memcg_stat_cross_cpu correctness test for flush
>  selftests/hid: build the BPF program via the shared lib.bpf.mk
>  selftests/sched_ext: build BPF schedulers via the shared lib.bpf.mk
>
> tools/testing/selftests/cgroup/.gitignore     |   8 +
> tools/testing/selftests/cgroup/Makefile       |  52 ++
> tools/testing/selftests/cgroup/config         |   5 +
> .../selftests/cgroup/lib/cgroup_util.c        |  83 +++
> .../cgroup/lib/include/cgroup_util.h          |   3 +
> .../cgroup/memcg_stat_cross_cpu.bpf.c         |  86 +++
> .../selftests/cgroup/memcg_stat_cross_cpu.h   |  21 +
> .../cgroup/test_memcg_stat_cross_cpu.c        | 596 ++++++++++++++++++
> .../selftests/cgroup/test_memcontrol.c        |  29 +-
> tools/testing/selftests/hid/.gitignore        |   1 +
> tools/testing/selftests/hid/Makefile          | 180 +-----
> tools/testing/selftests/lib.bpf.mk            | 296 +++++++++
> tools/testing/selftests/sched_ext/Makefile    | 146 +----
> 13 files changed, 1204 insertions(+), 302 deletions(-)
> create mode 100644 tools/testing/selftests/cgroup/memcg_stat_cross_cpu.bpf.c
> create mode 100644 tools/testing/selftests/cgroup/memcg_stat_cross_cpu.h
> create mode 100644 tools/testing/selftests/cgroup/test_memcg_stat_cross_cpu.c
> create mode 100644 tools/testing/selftests/lib.bpf.mk
>
>-- 
>2.53.0-Meta
>