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 <[email protected]>
---
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/[email protected]
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/[email protected]
---
Ricardo B. Marlière (11):
selftests/bpf: Fix test_kmods KDIR to honor O= and distro kernels
selftests/bpf: Route test_kmods through the kselftest module flow
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 | 135 +++++++++++++--------
.../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, 129 insertions(+), 62 deletions(-)
---
base-commit: a1aa9ef47c299c5bbc30594d3c2f0589edf908e6
change-id: 20260401-selftests-bpf_misconfig-4c33ef5c56da
Best regards,
--
Ricardo B. Marlière <[email protected]>
