Hi,
On 8/28/2023 3:55 PM, Jiri Olsa wrote:
> Add missed value to kprobe attached through perf link info to
> hold the stats of missed kprobe handler execution.
>
> The kprobe's missed counter gets incremented when kprobe handler
> is not executed due to another kprobe running on the same cpu.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> include/linux/trace_events.h | 6 ++++--
> include/uapi/linux/bpf.h | 1 +
> kernel/bpf/syscall.c | 14 ++++++++------
> kernel/trace/bpf_trace.c | 5 +++--
> kernel/trace/trace_kprobe.c | 5 ++++-
> tools/include/uapi/linux/bpf.h | 1 +
> 6 files changed, 21 insertions(+), 11 deletions(-)
>
SNIP
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 17c21c0b2dd1..998c88874507 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1546,7 +1546,8 @@ NOKPROBE_SYMBOL(kretprobe_perf_func);
>
> int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
> const char **symbol, u64 *probe_offset,
> - u64 *probe_addr, bool perf_type_tracepoint)
> + u64 *probe_addr, unsigned long *missed,
> + bool perf_type_tracepoint)
> {
> const char *pevent = trace_event_name(event->tp_event);
> const char *group = event->tp_event->class->system;
> @@ -1565,6 +1566,8 @@ int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
> *probe_addr = kallsyms_show_value(current_cred()) ?
> (unsigned long)tk->rp.kp.addr : 0;
> *symbol = tk->symbol;
> + if (missed)
> + *missed = tk->rp.kp.nmissed;
According to the implement of probes_profile_seq_show(), the missed
counter for kretprobe should be tk->rp.kp.nmissed + tk->rp.nmissed. I
think it would be a good idea to factor out a common helper to get the
missed counter for kprobe or kretprobe.
> return 0;
> }
> #endif /* CONFIG_PERF_EVENTS */
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index b754edfb0cd7..5a39c7a13499 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -6539,6 +6539,7 @@ struct bpf_link_info {
> __u32 name_len;
> __u32 offset; /* offset from func_name */
> __u64 addr;
> + __u64 missed;
> } kprobe; /* BPF_PERF_EVENT_KPROBE, BPF_PERF_EVENT_KRETPROBE */
> struct {
> __aligned_u64 tp_name; /* in/out */
