Subject: Re: [PATCH v21 bpf-next 18/23] libbpf: Add SEC name for xdp_mb programs

From: Lorenzo Bianconi <[email-masked]>
Date: Wed, 12 Jan 2022 19:35:25 +0100

> On Wed, Jan 12, 2022 at 10:18 AM Lorenzo Bianconi <[email-masked]> wrote:
> >
> > > On Sun, Jan 9, 2022 at 7:05 AM Lorenzo Bianconi <[email-masked]> wrote:
> > > >
> > > > Introduce support for the following SEC entries for XDP multi-buff
> > > > property:
> > > > - SEC("xdp_mb/")
> > > > - SEC("xdp_devmap_mb/")
> > > > - SEC("xdp_cpumap_mb/")
> > >
> > > Libbpf seemed to went with .<suffix> rule (e.g., fentry.s for
> > > sleepable, seems like we'll have kprobe.multi or  something along
> > > those lines as well), so let's stay consistent and call this "xdp_mb",
> > > "xdp_devmap.mb", "xdp_cpumap.mb" (btw, is "mb" really all that
> > > recognizable? would ".multibuf" be too verbose?). Also, why the "/"
> > > part? Also it shouldn't be "sloppy" either. Neither expected attach
> > > type should be optional.  Also not sure SEC_ATTACHABLE is needed. So
> > > at most it should be SEC_XDP_MB, probably.
> >
> > ack, I fine with it. Something like:
> >
> >         SEC_DEF("lsm.s/",               LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
> >         SEC_DEF("iter/",                TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),
> >         SEC_DEF("syscall",              SYSCALL, 0, SEC_SLEEPABLE),
> > +       SEC_DEF("xdp_devmap.multibuf",  XDP, BPF_XDP_DEVMAP, 0),
> >         SEC_DEF("xdp_devmap/",          XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),
> > +       SEC_DEF("xdp_cpumap.multibuf",  XDP, BPF_XDP_CPUMAP, 0),
> >         SEC_DEF("xdp_cpumap/",          XDP, BPF_XDP_CPUMAP, SEC_ATTACHABLE),
> > +       SEC_DEF("xdp.multibuf",         XDP, BPF_XDP, 0),
> 
> yep, but please use SEC_NONE instead of zero

ack, I will fix it.

> 
> >         SEC_DEF("xdp",                  XDP, BPF_XDP, SEC_ATTACHABLE_OPT | SEC_SLOPPY_PFX),
> >         SEC_DEF("perf_event",           PERF_EVENT, 0, SEC_NONE | SEC_SLOPPY_PFX),
> >         SEC_DEF("lwt_in",               LWT_IN, 0, SEC_NONE | SEC_SLOPPY_PFX),
> >
> > >
> > > >
> > > > Acked-by: Toke Hoiland-Jorgensen <[email-masked]>
> > > > Acked-by: John Fastabend <[email-masked]>
> > > > Signed-off-by: Lorenzo Bianconi <[email-masked]>
> > > > ---
> > > >  tools/lib/bpf/libbpf.c | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > > > index 7f10dd501a52..c93f6afef96c 100644
> > > > --- a/tools/lib/bpf/libbpf.c
> > > > +++ b/tools/lib/bpf/libbpf.c
> > > > @@ -235,6 +235,8 @@ enum sec_def_flags {
> > > >         SEC_SLEEPABLE = 8,
> > > >         /* allow non-strict prefix matching */
> > > >         SEC_SLOPPY_PFX = 16,
> > > > +       /* BPF program support XDP multi-buff */
> > > > +       SEC_XDP_MB = 32,
> > > >  };
> > > >
> > > >  struct bpf_sec_def {
> > > > @@ -6562,6 +6564,9 @@ static int libbpf_preload_prog(struct bpf_program *prog,
> > > >         if (def & SEC_SLEEPABLE)
> > > >                 opts->prog_flags |= BPF_F_SLEEPABLE;
> > > >
> > > > +       if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_MB))
> > > > +               opts->prog_flags |= BPF_F_XDP_MB;
> > >
> > > I'd say you don't even need SEC_XDP_MB flag at all, you can just check
> > > that prog->sec_name is one of "xdp.mb", "xdp_devmap.mb" or
> > > "xdp_cpumap.mb" and add the flag. SEC_XDP_MB doesn't seem generic
> > > enough to warrant a flag.
> >
> > ack, something like:
> >
> > +       if (prog->type == BPF_PROG_TYPE_XDP &&
> > +           (!strcmp(prog->sec_name, "xdp_devmap.multibuf") ||
> > +            !strcmp(prog->sec_name, "xdp_cpumap.multibuf") ||
> > +            !strcmp(prog->sec_name, "xdp.multibuf")))
> > +               opts->prog_flags |= BPF_F_XDP_MB;
> 
> yep, can also simplify it a bit with strstr(prog->sec_name,
> ".multibuf") instead of three strcmp

ack, I will fix it.

Regards,
Lorenzo

> 
> >
> > Regards,
> > Lorenzo
> >
> > >
> > > > +
> > > >         if ((prog->type == BPF_PROG_TYPE_TRACING ||
> > > >              prog->type == BPF_PROG_TYPE_LSM ||
> > > >              prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
> > > > @@ -8600,8 +8605,11 @@ static const struct bpf_sec_def section_defs[] = {
> > > >         SEC_DEF("lsm.s/",               LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
> > > >         SEC_DEF("iter/",                TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),
> > > >         SEC_DEF("syscall",              SYSCALL, 0, SEC_SLEEPABLE),
> > > > +       SEC_DEF("xdp_devmap_mb/",       XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE | SEC_XDP_MB),
> > > >         SEC_DEF("xdp_devmap/",          XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),
> > > > +       SEC_DEF("xdp_cpumap_mb/",       XDP, BPF_XDP_CPUMAP, SEC_ATTACHABLE | SEC_XDP_MB),
> > > >         SEC_DEF("xdp_cpumap/",          XDP, BPF_XDP_CPUMAP, SEC_ATTACHABLE),
> > > > +       SEC_DEF("xdp_mb/",              XDP, BPF_XDP, SEC_ATTACHABLE_OPT | SEC_SLOPPY_PFX | SEC_XDP_MB),
> > > >         SEC_DEF("xdp",                  XDP, BPF_XDP, SEC_ATTACHABLE_OPT | SEC_SLOPPY_PFX),
> > > >         SEC_DEF("perf_event",           PERF_EVENT, 0, SEC_NONE | SEC_SLOPPY_PFX),
> > > >         SEC_DEF("lwt_in",               LWT_IN, 0, SEC_NONE | SEC_SLOPPY_PFX),
> > > > --
> > > > 2.33.1
> > > >