netdev - Re: [PATCH v21 bpf-next 18/23] libbpf: Add SEC name for xdp

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Date:   Wed, 12 Jan 2022 19:17:56 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Shay Agroskin <shayagr@...zon.com>,
        john fastabend <john.fastabend@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Saeed Mahameed <saeed@...nel.org>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        tirthendu.sarkar@...el.com,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH v21 bpf-next 18/23] libbpf: Add SEC name for xdp_mb
 programs

> On Sun, Jan 9, 2022 at 7:05 AM Lorenzo Bianconi <lorenzo@...nel.org> 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),
 	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 <toke@...hat.com>
> > Acked-by: John Fastabend <john.fastabend@...il.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> >  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;

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
> >

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