Re: [PATCH 01/14] perf/x86: Introduce PERF_RECORD_OVERHEAD

[Peter Zijlstra]

On Wed, Nov 23, 2016 at 04:44:39AM -0500, kan.li...@intel.com wrote:
> +struct perf_overhead_entry {
> +     __u32   cpu;
> +     __u64   nr;
> +     __u64   time;
> +};

> +void perf_log_overhead(struct perf_event *event, u32 type,
> +                    struct perf_overhead_entry *entry)
> +{
> +     struct perf_output_handle handle;
> +     struct perf_sample_data sample;
> +     int ret;
> +
> +     struct {
> +             struct perf_event_header        header;
> +             u32                             type;

There's two u32 sized holes here.

> +             struct perf_overhead_entry      overhead;
> +     } overhead_event = {
> +             .header = {
> +                     .type = PERF_RECORD_OVERHEAD,
> +                     .misc = 0,
> +                     .size = sizeof(overhead_event),
> +             },
                .type = type,
                .overhead = *event,
> +     };

> +     overhead_event.type = type;
> +     memcpy(&overhead_event.overhead, entry, 
> sizeof(overhead_event.overhead));

Do the above named initialization instead.

> +
> +     perf_event_header__init_id(&overhead_event.header, &sample, event);
> +     ret = perf_output_begin(&handle, event, overhead_event.header.size);
> +
> +     if (ret)
> +             return;
> +
> +     perf_output_put(&handle, overhead_event);
> +     perf_event__output_id_sample(event, &handle, &sample);
> +
> +     perf_output_end(&handle);
> +     memset(entry, 0, sizeof(*entry));
> +}