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SubjectRe: [PATCH v1 2/3] perf session: Add swap operation for event TIME_CONV
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On 12/04/21 11:34 am, Leo Yan wrote:
> Since commit d110162cafc8 ("perf tsc: Support cap_user_time_short for
> event TIME_CONV"), the event PERF_RECORD_TIME_CONV has extended the data
> structure for clock parameters.
>
> To be backwards-compatible, this patch adds a dedicated swap operation
> for the event PERF_RECORD_TIME_CONV, based on checking the event size,
> it can support both for the old and new event formats.
>
> Fixes: d110162cafc8 ("perf tsc: Support cap_user_time_short for event TIME_CONV")
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> tools/perf/util/session.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 9a8808507bd9..afca3d5fc851 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -949,6 +949,26 @@ static void perf_event__stat_round_swap(union perf_event *event,
> event->stat_round.time = bswap_64(event->stat_round.time);
> }
>
> +static void perf_event__time_conv_swap(union perf_event *event,
> + bool sample_id_all __maybe_unused)
> +{
> + size_t time_zero_size;
> +
> + event->time_conv.time_shift = bswap_64(event->time_conv.time_shift);
> + event->time_conv.time_mult = bswap_64(event->time_conv.time_mult);
> + event->time_conv.time_zero = bswap_64(event->time_conv.time_zero);
> +
> + time_zero_size = (void *)&event->time_conv.time_cycles - (void *)event;
> + if (event->header.size > time_zero_size) {

I wonder if we could have a helper for this e.g. (untested)

#define event_contains(obj, mem) (obj.header.size > offsetof(typeof(obj), mem))

if (event_contains(event->time_conv, time_cycles)) {


> + event->time_conv.time_cycles = bswap_64(event->time_conv.time_cycles);
> + event->time_conv.time_mask = bswap_64(event->time_conv.time_mask);
> + event->time_conv.cap_user_time_zero =
> + bswap_32(event->time_conv.cap_user_time_zero);
> + event->time_conv.cap_user_time_short =
> + bswap_32(event->time_conv.cap_user_time_short);

'struct perf_record_time_conv' contains bool, the sizeof which, AFAIK, is not defined.
Is it really 4 bytes on your implementation? It is only 1 byte with gcc on x86.

Either way, you should change 'struct perf_record_time_conv' so it uses a type of known size.
Since you are the only one using it, it should match your implementation.

> + }
> +}
> +
> typedef void (*perf_event__swap_op)(union perf_event *event,
> bool sample_id_all);
>
> @@ -985,7 +1005,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
> [PERF_RECORD_STAT] = perf_event__stat_swap,
> [PERF_RECORD_STAT_ROUND] = perf_event__stat_round_swap,
> [PERF_RECORD_EVENT_UPDATE] = perf_event__event_update_swap,
> - [PERF_RECORD_TIME_CONV] = perf_event__all64_swap,
> + [PERF_RECORD_TIME_CONV] = perf_event__time_conv_swap,
> [PERF_RECORD_HEADER_MAX] = NULL,
> };
>
>

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