From: Jiri Olsa <olsajiri@gmail.com>
To: Song Liu <song@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Hou Tao <houtao1@huawei.com>,
bpf@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Daniel Xu <dxu@dxuuu.xyz>
Subject: Re: [PATCHv3 bpf-next 2/9] bpf: Add missed value to kprobe_multi link info
Date: Sat, 23 Sep 2023 10:21:36 +0200 [thread overview]
Message-ID: <ZQ6gEHioaIwBYgwV@krava> (raw)
In-Reply-To: <CAPhsuW5fn=zaayBL2R1D+rKkO5AWuPmwp1WydGkKcCD7QO6U2w@mail.gmail.com>
On Thu, Sep 21, 2023 at 11:52:16AM -0700, Song Liu wrote:
> On Wed, Sep 20, 2023 at 2:32 PM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Add missed value to kprobe_multi link info to hold the stats of missed
> > kprobe_multi probe.
> >
> > The missed counter gets incremented when fprobe fails the recursion
> > check or there's no rethook available for return probe. In either
> > case the attached bpf program is not executed.
> >
> > Acked-by: Hou Tao <houtao1@huawei.com>
> > Reviewed-and-tested-by: Song Liu <song@kernel.org>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> > include/uapi/linux/bpf.h | 1 +
> > kernel/trace/bpf_trace.c | 1 +
> > tools/include/uapi/linux/bpf.h | 1 +
> > 3 files changed, 3 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 73b155e52204..e5216420ec73 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -6530,6 +6530,7 @@ struct bpf_link_info {
> > __aligned_u64 addrs;
> > __u32 count; /* in/out: kprobe_multi function count */
> > __u32 flags;
> > + __u64 missed;
>
> This does not make bpf_link_info bigger. So if we use newer user space
> on older kernel, the user space cannot tell whether missed == 0 or the
> kernel doesn't support "missed". Right?
hum, I think that's right.. but I think that would be the case
even if it did make bpf_link_info bigger, because we'd need to
pass zeroed value in 'missed' field and it'd not be changed by
older kernel
user space could maybe check if there's 'missed field in
bpf_link_info.perf_event.kprobe.missed ?
jirka
>
> Thanks,
> Song
>
> > } kprobe_multi;
> > struct {
> > __u32 type; /* enum bpf_perf_event_type */
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 279a3d370812..aec52938c703 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -2614,6 +2614,7 @@ static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link *link,
> > kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
> > info->kprobe_multi.count = kmulti_link->cnt;
> > info->kprobe_multi.flags = kmulti_link->flags;
> > + info->kprobe_multi.missed = kmulti_link->fp.nmissed;
> >
> > if (!uaddrs)
> > return 0;
> > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> > index 73b155e52204..e5216420ec73 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -6530,6 +6530,7 @@ struct bpf_link_info {
> > __aligned_u64 addrs;
> > __u32 count; /* in/out: kprobe_multi function count */
> > __u32 flags;
> > + __u64 missed;
> > } kprobe_multi;
> > struct {
> > __u32 type; /* enum bpf_perf_event_type */
> > --
> > 2.41.0
> >
> >
next prev parent reply other threads:[~2023-09-23 8:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-20 21:31 [PATCHv3 bpf-next 0/9] bpf: Add missed stats for kprobes Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 1/9] bpf: Count stats for kprobe_multi programs Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 2/9] bpf: Add missed value to kprobe_multi link info Jiri Olsa
2023-09-21 18:52 ` Song Liu
2023-09-23 8:21 ` Jiri Olsa [this message]
2023-09-20 21:31 ` [PATCHv3 bpf-next 3/9] bpf: Add missed value to kprobe perf " Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 4/9] bpf: Count missed stats in trace_call_bpf Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 5/9] bpftool: Display missed count for kprobe_multi link Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 6/9] bpftool: Display missed count for kprobe perf link Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 7/9] selftests/bpf: Add test for missed counts of perf event link kprobe Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 8/9] selftests/bpf: Add test for recursion " Jiri Olsa
2023-09-20 21:31 ` [PATCHv3 bpf-next 9/9] selftests/bpf: Add test for recursion counts of perf event link tracepoint Jiri Olsa
2023-09-25 23:50 ` [PATCHv3 bpf-next 0/9] bpf: Add missed stats for kprobes patchwork-bot+netdevbpf
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