On Wed, Sep 20, 2023 at 2:32 PM Jiri Olsa <jolsa@xxxxxxxxxx> 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@xxxxxxxxxx>
> Reviewed-and-tested-by: Song Liu <song@xxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> 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?
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
>
>
