Re: [PATCH v2 bpf-next 7/9] libbpf: complete SEC() table unification for BPF_APROG_SEC/BPF_EAPROG_SEC

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Sep 21, 2021 at 6:42 PM Dave Marchevsky <davemarchevsky@fb.com> wrote:
>
> On 9/20/21 7:43 PM, Andrii Nakryiko wrote:
> > Complete SEC() table refactoring towards unified form by rewriting
> > BPF_APROG_SEC and BPF_EAPROG_SEC definitions with
> > SEC_DEF(SEC_ATTACHABLE_OPT) (for optional expected_attach_type) and
> > SEC_DEF(SEC_ATTACHABLE) (mandatory expected_attach_type), respectively.
> > Drop BPF_APROG_SEC, BPF_EAPROG_SEC, and BPF_PROG_SEC_IMPL macros after
> > that, leaving SEC_DEF() macro as the only one used.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> > ---
> >  tools/lib/bpf/libbpf.c | 136 +++++++++++------------------------------
> >  1 file changed, 35 insertions(+), 101 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 734be7dc52a0..56082865ceff 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -7959,32 +7959,6 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog,
> >       prog->expected_attach_type = type;
> >  }
> >
> > -#define BPF_PROG_SEC_IMPL(string, ptype, eatype, eatype_optional,        \
> > -                       attachable, attach_btf)                           \
> > -     {                                                                   \
> > -             .sec = string,                                              \
> > -             .prog_type = ptype,                                         \
> > -             .expected_attach_type = eatype,                             \
> > -             .cookie = (long) (                                          \
> > -                     (eatype_optional ? SEC_EXP_ATTACH_OPT : 0) |   \
> > -                     (attachable ? SEC_ATTACHABLE : 0) |                 \
> > -                     (attach_btf ? SEC_ATTACH_BTF : 0)                   \
> > -             ),                                                          \
> > -             .preload_fn = libbpf_preload_prog,                          \
> > -     }
> > -
> > -/* Programs that can be attached. */
> > -#define BPF_APROG_SEC(string, ptype, atype) \
> > -     BPF_PROG_SEC_IMPL(string, ptype, atype, true, 1, 0)
> > -
> > -/* Programs that must specify expected attach type at load time. */
> > -#define BPF_EAPROG_SEC(string, ptype, eatype) \
> > -     BPF_PROG_SEC_IMPL(string, ptype, eatype, false, 1, 0)
> > -
> > -/* Programs that use BTF to identify attach point */
> > -#define BPF_PROG_BTF(string, ptype, eatype) \
> > -     BPF_PROG_SEC_IMPL(string, ptype, eatype, false, 0, 1)
> > -
>
> Similar thoughts about comment usefulness as patch 6.
>

I'll add succinct comments to each SEC_xxx flag, trying to emphasize
what it is about

> >  #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {                     \
> >       .sec = sec_pfx,                                                     \
> >       .prog_type = BPF_PROG_TYPE_##ptype,                                 \
> > @@ -8003,10 +7977,8 @@ static struct bpf_link *attach_iter(const struct bpf_program *prog, long cookie)
> >
> >  static const struct bpf_sec_def section_defs[] = {
> >       SEC_DEF("socket",               SOCKET_FILTER, 0, SEC_NONE),
> > -     BPF_EAPROG_SEC("sk_reuseport/migrate",  BPF_PROG_TYPE_SK_REUSEPORT,
> > -                                             BPF_SK_REUSEPORT_SELECT_OR_MIGRATE),
> > -     BPF_EAPROG_SEC("sk_reuseport",          BPF_PROG_TYPE_SK_REUSEPORT,
> > -                                             BPF_SK_REUSEPORT_SELECT),
> > +     SEC_DEF("sk_reuseport/migrate", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, SEC_ATTACHABLE),
> > +     SEC_DEF("sk_reuseport",         SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT, SEC_ATTACHABLE),
>
> Ah, I see that after this patch the alignment issue from patch 6 is better.
> Nevermind then.
>
> >       SEC_DEF("kprobe/",              KPROBE, 0, SEC_NONE, attach_kprobe),
> >       SEC_DEF("uprobe/",              KPROBE, 0, SEC_NONE),
> >       SEC_DEF("kretprobe/",           KPROBE, 0, SEC_NONE, attach_kprobe),
>
> [...]
>
> > +     SEC_DEF("sk_skb/stream_parser", SK_SKB, BPF_SK_SKB_STREAM_PARSER, SEC_ATTACHABLE_OPT),
> > +     SEC_DEF("sk_skb/stream_verdict",SK_SKB, BPF_SK_SKB_STREAM_VERDICT, SEC_ATTACHABLE_OPT),
>
> checkpatch really doesn't like the lack of space after comma here, I agree
> with it.

it was either this, or one extra tab for all other entries making
every line longer still. But I guess I'll just do s/SEC_DEF/SECDEF/
and get that space back :)

But keep in mind, checkpatch.pl is a guide, not a law.

>
> >       SEC_DEF("sk_skb",               SK_SKB, 0, SEC_NONE),
> > -     BPF_APROG_SEC("sk_msg",                 BPF_PROG_TYPE_SK_MSG,
> > -                                             BPF_SK_MSG_VERDICT),
> > -     BPF_APROG_SEC("lirc_mode2",             BPF_PROG_TYPE_LIRC_MODE2,
>
> [...]
>