On Thu, Apr 14, 2022 at 3:45 PM Alexander Lobakin <alobakin@xxxxx> wrote:
>
> When CONFIG_PERF_EVENTS is not set, struct perf_event remains empty.
> However, the structure is being used by bpftool indirectly via BTF.
> This leads to:
>
> skeleton/pid_iter.bpf.c:49:30: error: no member named 'bpf_cookie' in 'struct perf_event'
> return BPF_CORE_READ(event, bpf_cookie);
> ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
>
> ...
>
> skeleton/pid_iter.bpf.c:49:9: error: returning 'void' from a function with incompatible result type '__u64' (aka 'unsigned long long')
> return BPF_CORE_READ(event, bpf_cookie);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Tools and samples can't use any CONFIG_ definitions, so the fields
> used there should always be present.
> Move CONFIG_BPF_SYSCALL block out of the CONFIG_PERF_EVENTS block
> to make it available unconditionally.
>
> Fixes: cbdaf71f7e65 ("bpftool: Add bpf_cookie to link output")
> Signed-off-by: Alexander Lobakin <alobakin@xxxxx>
While I can't think of a real failure with this approach, it does feel
weird to me. Can we fix this with bpf_core_field_exists()?
Thanks,
Song
> ---
> include/linux/perf_event.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index af97dd427501..b1d5715b8b34 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -762,12 +762,14 @@ struct perf_event {
> u64 (*clock)(void);
> perf_overflow_handler_t overflow_handler;
> void *overflow_handler_context;
> +#endif /* CONFIG_PERF_EVENTS */
> #ifdef CONFIG_BPF_SYSCALL
> perf_overflow_handler_t orig_overflow_handler;
> struct bpf_prog *prog;
> u64 bpf_cookie;
> #endif
>
> +#ifdef CONFIG_PERF_EVENTS
> #ifdef CONFIG_EVENT_TRACING
> struct trace_event_call *tp_event;
> struct event_filter *filter;
> --
> 2.35.2
>
>
