* Kyle Huey <me@xxxxxxxxxxxx> wrote:
> To ultimately allow bpf programs attached to perf events to completely
> suppress all of the effects of a perf event overflow (rather than just the
> sample output, as they do today), call bpf_overflow_handler() from
> __perf_event_overflow() directly rather than modifying struct perf_event's
> overflow_handler. Return the bpf program's return value from
> bpf_overflow_handler() so that __perf_event_overflow() knows how to
> proceed. Remove the now unnecessary orig_overflow_handler from struct
> perf_event.
>
> This patch is solely a refactoring and results in no behavior change.
>
> Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx>
> Suggested-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> Acked-by: Song Liu <song@xxxxxxxxxx>
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> include/linux/perf_event.h | 6 +-----
> kernel/events/core.c | 28 +++++++++++++++-------------
> 2 files changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index d2a15c0c6f8a..c7f54fd74d89 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -810,7 +810,6 @@ struct perf_event {
> perf_overflow_handler_t overflow_handler;
> void *overflow_handler_context;
> #ifdef CONFIG_BPF_SYSCALL
> - perf_overflow_handler_t orig_overflow_handler;
> struct bpf_prog *prog;
> u64 bpf_cookie;
> #endif
Could we reduce the #ifdeffery please?
On distros CONFIG_BPF_SYSCALL is almost always enabled, so it's not like
this truly saves anything on real systems.
I'd suggest making the perf_event::prog and perf_event::bpf_cookie fields
unconditional.
> +#ifdef CONFIG_BPF_SYSCALL
> +static int bpf_overflow_handler(struct perf_event *event,
> + struct perf_sample_data *data,
> + struct pt_regs *regs);
> +#endif
If the function definitions are misordered then first do a patch that moves
the function earlier in the file, instead of slapping a random prototype
into a random place.
> - READ_ONCE(event->overflow_handler)(event, data, regs);
> +#ifdef CONFIG_BPF_SYSCALL
> + if (!(event->prog && !bpf_overflow_handler(event, data, regs)))
> +#endif
> + READ_ONCE(event->overflow_handler)(event, data, regs);
This #ifdef would go away too - on !CONFIG_BPF_SYSCALL event->prog should
always be NULL.
Please keep the #ifdeffery reduction and function-moving patches separate
from these other changes.
Thanks,
Ingo
