Re: [RFC PATCH bpf-next v5 6/8] selftests/bpf: extract BPF skeleton generation into a helper script

[Eduard Zingerman <eddyz87@gmail.com>]

On Tue, 2026-08-04 at 10:01 -0700, Mykola Lysenko wrote:
> The four skeleton generation recipes (regular, light, signed light and
> linked) are near-identical five-step pipelines - link via "bpftool gen
> object" three times, compare the second and third results as a
> regression test for bpftool's determinism, generate the skeleton (and
> possibly subskeleton), remove intermediates - duplicated with small
> variations inside DEFINE_TEST_RUNNER_RULES, where every line pays the
> double-expansion escaping tax.
> 
> Move the pipeline into gen_bpf_skel.sh; the differences between the
> four variants become the --lskel, --sign and --subskel flags. Signing
> takes the key and certificate from $PRIVATE_KEY and $VERIFICATION_CERT
> in the environment, like the bpftool binary comes from $BPFTOOL. The
> distinct linked/llinked intermediate infixes are kept but derived
> inside the script: tests listed in LSKELS_EXTRA generate both a
> .skel.h and a .lskel.h from the same .bpf.o, and distinct intermediate
> names are what keeps parallel builds from racing. Build-log messages
> stay in the recipes with the usual $(call msg,...) helpers; behavior
> is unchanged.
> 
> Suggested-by: Eduard Zingerman <eddyz87@gmail.com>
> Assisted-by: Claude:claude-fable-5 shellcheck
> Signed-off-by: Mykola Lysenko <nickolay.lysenko@gmail.com>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

I need to print this out and hang it at my desk.

  ┌────────────┬─────────────────┬───────────────────────────┬─────┐
  │ expression │     x unset     │           x=""            │ x=v │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x-D}     │ D               │ `` (empty)                │ v   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x:-D}    │ D               │ D                         │ v   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x+A}     │ ``              │ A                         │ A   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x:+A}    │ ``              │ ``                        │ A   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x=D}     │ D (and assigns) │ `` (no assign — x is set) │ v   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x:=D}    │ D (and assigns) │ D (and assigns)           │ v   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x?msg}   │ abort           │ ``                        │ v   │
  ├────────────┼─────────────────┼───────────────────────────┼─────┤
  │ ${x:?msg}  │ abort           │ abort                     │ v   │
  └────────────┴─────────────────┴───────────────────────────┴─────┘

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