Currently the BPF selftests can only be built by using the minimum kernel
configuration defined in tools/testing/selftests/bpf/config*. This poses a
problem in distribution kernels that may have some of the flags disabled or
set as module. For example, we have been running the tests regularly in
openSUSE Tumbleweed [1] [2] but to work around this fact we created a
special package [3] that build the tests against an auxiliary vmlinux with
the BPF Kconfig. We keep a list of known issues that may happen due to,
amongst other things, configuration mismatches [4] [5].
The maintenance of this package is far from ideal, especially for
enterprise kernels. The goal of this series is to enable the common usecase
of running the following in any system:
```sh
make -C tools/testing/selftests install \
SKIP_TARGETS= \
TARGETS=bpf \
O=/lib/modules/$(uname -r)/build
```
As an example, the following script targeting a minimal config can be used
for testing:
```sh
make defconfig
scripts/config --file .config \
--enable DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT \
--enable DEBUG_INFO_BTF \
--enable BPF_SYSCALL \
--enable BPF_JIT
make olddefconfig
make -j$(nproc)
make -j$(nproc) -C tools/testing/selftests SKIP_TARGETS= TARGETS=bpf install
```
This produces a test_progs binary with 579 subtests, against the total of
708. Many of them will still fail or be skipped at runtime due to lack of
symbols, but at least there will be a clear way of building the tests.
[1]: https://openqa.opensuse.org/tests/5811715
[2]: https://openqa.opensuse.org/tests/5811730
[3]: https://src.opensuse.org/rmarliere/kselftests
[4]: https://github.com/openSUSE/kernel-qe/blob/main/kselftests_known_issues.yaml
[5]: https://openqa.opensuse.org/tests/5811730/logfile?filename=run_kselftests-config_mismatches.txt
Assisted-by: {codex,claude}
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
---
Changes in v4:
- Drop the test_kmods kselftest module flow patch: lib.mk gen_mods_dir
invokes $(MAKE) -C $(TEST_GEN_MODS_DIR) without forwarding
RESOLVE_BTFIDS, breaking ASAN and GCC BPF CI builds (Makefile.modfinal
cannot find resolve_btfids in the kbuild output tree)
- Link to v3:
https://patch.msgid.link/20260406-selftests-bpf_misconfig-v3-0-587a1114263c@suse.com
Changes in v3:
- Split test_kmods patch into two: fix KDIR handling (O= passthrough,
EXTRA_CFLAGS/EXTRA_LDFLAGS clearing) and wire into lib.mk via
TEST_GEN_MODS_DIR
- Pass O= through to the kernel module build so artifacts land in the
output tree, not the source tree
- Clear EXTRA_CFLAGS and EXTRA_LDFLAGS when invoking the kernel build to
prevent host flags (e.g. -static) leaking into module compilation
- Replace the bespoke test_kmods pattern rule with lib.mk module
infrastructure (TEST_GEN_MODS_DIR); lib.mk now drives build and clean
lifecycle
- Make the .ko copy step resilient: emit SKIP instead of failing when a
module is absent
- Expand the uprobe weak stub comment in bpf_cookie.c to explain why
noinline is required
- Link to v2:
https://patch.msgid.link/20260403-selftests-bpf_misconfig-v2-0-f06700380a9d@suse.com
Changes in v2:
- Skip test_kmods build/clean when KDIR directory does not exist
- Use `Module.symvers` instead of `.config` for in-tree detection
- Fix skeleton order-only prereqs commit message
- Guard BTFIDS step when .test.o is absent
- Add `__weak stack_mprotect()` stubs in `bpf_cookie.c` and `iters.c`
- Link to v1:
https://patch.msgid.link/20260401-selftests-bpf_misconfig-v1-0-3ae42c0af76f@suse.com
---
Ricardo B. Marlière (10):
selftests/bpf: Fix test_kmods KDIR to honor O= and distro kernels
selftests/bpf: Tolerate BPF and skeleton generation failures
selftests/bpf: Avoid rebuilds when running emit_tests
selftests/bpf: Make skeleton headers order-only prerequisites of .test.d
selftests/bpf: Tolerate test file compilation failures
selftests/bpf: Allow test_progs to link with a partial object set
selftests/bpf: Tolerate benchmark build failures
selftests/bpf: Provide weak definitions for cross-test functions
selftests/bpf: Skip tests whose objects were not built
selftests/bpf: Tolerate missing files during install
tools/testing/selftests/bpf/Makefile | 113 ++++++++++++++-------
.../testing/selftests/bpf/prog_tests/bpf_cookie.c | 24 ++++-
tools/testing/selftests/bpf/prog_tests/iters.c | 10 +-
tools/testing/selftests/bpf/test_kmods/Makefile | 15 ++-
tools/testing/selftests/bpf/test_progs.c | 7 +-
5 files changed, 120 insertions(+), 49 deletions(-)
---
base-commit: a1aa9ef47c299c5bbc30594d3c2f0589edf908e6
change-id: 20260401-selftests-bpf_misconfig-4c33ef5c56da
Best regards,
--
Ricardo B. Marlière <rbm@suse.com>