On Mon, Jul 26, 2021 at 09:12:02AM -0700, Andrii Nakryiko wrote:
> Add ability for users to specify custom u64 value when creating BPF link for
> perf_event-backed BPF programs (kprobe/uprobe, perf_event, tracepoints).
If I read this right, the value is dependent on the link, not the
program. In which case:
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 2d510ad750ed..97ab46802800 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -762,6 +762,7 @@ struct perf_event {
> #ifdef CONFIG_BPF_SYSCALL
> perf_overflow_handler_t orig_overflow_handler;
> struct bpf_prog *prog;
> + u64 user_ctx;
> #endif
>
> #ifdef CONFIG_EVENT_TRACING
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index 8ac92560d3a3..4543852f1480 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -675,7 +675,7 @@ trace_trigger_soft_disabled(struct trace_event_file *file)
>
> #ifdef CONFIG_BPF_EVENTS
> unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx);
> -int perf_event_attach_bpf_prog(struct perf_event *event, struct bpf_prog *prog);
> +int perf_event_attach_bpf_prog(struct perf_event *event, struct bpf_prog *prog, u64 user_ctx);
This API would be misleading, because it is about setting the program.
> void perf_event_detach_bpf_prog(struct perf_event *event);
> int perf_event_query_prog_array(struct perf_event *event, void __user *info);
> int bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *prog);
> @@ -9966,6 +9968,7 @@ static int perf_event_set_bpf_handler(struct perf_event *event, struct bpf_prog
> }
>
> event->prog = prog;
> + event->user_ctx = user_ctx;
> event->orig_overflow_handler = READ_ONCE(event->overflow_handler);
> WRITE_ONCE(event->overflow_handler, bpf_overflow_handler);
> return 0;
Also, the name @user_ctx is a bit confusing. Would something like
@bpf_cookie or somesuch not be a better name?
Combined would it not make more sense to add something like:
extern int perf_event_set_bpf_cookie(struct perf_event *event, u64 cookie);
