selftests/bpf: Make skeleton headers order-only prerequisites of .test.d

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The .test.d dependency files are generated by the C preprocessor and list
the headers each test file actually #includes. Skeleton headers appear in
those generated lists, so the .test.o -> .skel.h dependency is already
tracked by the .d file content.

Making skeletons order-only prerequisites of .test.d means that a missing
or skipped skeleton does not prevent .test.d generation, and regenerating a
skeleton does not force .test.d to be recreated. This avoids unnecessary
recompilation and, more importantly, avoids build errors when a skeleton
was intentionally skipped due to a BPF compilation failure.

$$(BPFOBJ) is intentionally kept as a normal prerequisite: a libbpf
rebuild legitimately invalidates .test.d, since libbpf header changes
can affect the headers .test.o sees. Only the skeleton headers are
moved to order-only.

Note that adding a new BPF skeleton via a modified existing local header
still works correctly: GNU make builds order-only prerequisites that do
not exist (the order-only qualifier only suppresses timestamp-driven
rebuilds, not existence-driven builds), so a brand-new .skel.h listed in
TRUNNER_BPF_SKELS is generated even when .test.d is otherwise up to date.
The modified local header invalidates .test.o through the previously
included .d content, forcing a recompile that regenerates .test.d with
the new .skel.h dependency captured by gcc -MMD.

Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-5-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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This commit is contained in:

Ricardo B. Marlière 2026-06-02 10:02:54 -03:00 • committed by Alexei Starovoitov

parent a97bfc9aae

commit 5498e47741

1 changed files with 2 additions and 2 deletions

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tools/testing/selftests/bpf/Makefile

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