[PATCH v2 0/4] selftests: shared lib.bpf.mk for building BPF progs and skeletons

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, tools/testing/selftests/lib.bpf.mk,
and wires up three consumers. We believe this will simplify the work for
configuraing selftests with the bpf, for both the existing and future ones.

Patch 1 adds lib.bpf.mk: it builds the in-tree libbpf.a and a host
bpftool, generates vmlinux.h from the kernel's BTF, compiles *.bpf.c into
BPF objects and skeletons, and exports the include paths, a bpf_link
helper, and BPF_LDLIBS.  Use can control the behavior by several knobs
(source layout/suffix, extra headers/cflags, skeleton suffix,
subskeletons, output dirs) that can be used commonly in general cases.

Patch 2 adds a new selftest, test_memcg_stat_cross_cpu, under
selftests/cgroup. This test is a memory-cgroup statistics correctness
test that compares the memcg BPF kfuncs against memory.stat over a whole
cgroup subtree charged across many CPUs, and checks the cross-CPU rstat
flush. It is the first in-tree consumer of lib.bpf.mk outside
selftests/bpf.

Patches 3 and 4 convert the duplicated parts in Makefile for two
existing duplicating bpf consumers, the selftests/hid and
selftests/sched_ext, to lib.bpf.mk.  The generated skeletons keep
a byte-identical public API and land in the same locations as before.
The folders build cleanly under both plain make and LLVM=1.

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     |   6 +
 tools/testing/selftests/cgroup/Makefile       |  21 +
 tools/testing/selftests/cgroup/config         |   4 +
 .../selftests/cgroup/lib/cgroup_util.c        |  48 ++
 .../cgroup/lib/include/cgroup_util.h          |   1 +
 .../cgroup/memcg_stat_cross_cpu.bpf.c         |  86 ++
 .../selftests/cgroup/memcg_stat_cross_cpu.h   |  27 +
 .../cgroup/test_memcg_stat_cross_cpu.c        | 780 ++++++++++++++++++
 tools/testing/selftests/hid/Makefile          | 182 +---
 tools/testing/selftests/lib.bpf.mk            | 247 ++++++
 tools/testing/selftests/sched_ext/Makefile    | 153 +---
 11 files changed, 1275 insertions(+), 280 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


base-commit: 6eb8711ece2ce27e52e327a5b7a628ed39b97f45
-- 
2.53.0-Meta