On Wed, Jan 12, 2022 at 10:24 AM Andrii Nakryiko
[off-list ref] wrote:

On Wed, Jan 12, 2022 at 10:18 AM Lorenzo Bianconi [off-list ref] wrote:

quoted

quoted

On Sun, Jan 9, 2022 at 7:05 AM Lorenzo Bianconi [off-list ref] wrote:

quoted

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

quoted

        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),

quoted

quoted

Acked-by: Toke Hoiland-Jorgensen <redacted>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.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;

yep, can also simplify it a bit with strstr(prog->sec_name,
".multibuf") instead of three strcmp

Maybe ".mb" ?
".multibuf" is too verbose.
We're fine with ".s" for sleepable :)