Re: [PATCH v5 05/17] perf: cs-etm: Only save valid trace IDs into files

[Mike Leach]

On Fri, 12 Jul 2024 at 11:22, James Clark <james.clark@xxxxxxxxxx> wrote:
>
> From: James Clark <james.clark@xxxxxxx>
>
> This isn't a bug because Perf always masks with
> CORESIGHT_TRACE_ID_VAL_MASK before using these values, but to avoid it
> looking like it could be, make an effort to not save bad values.
>
> Signed-off-by: James Clark <james.clark@xxxxxxx>
> Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
> ---
>  tools/perf/arch/arm/util/cs-etm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
> index b0118546cd4d..14b8afabce3a 100644
> --- a/tools/perf/arch/arm/util/cs-etm.c
> +++ b/tools/perf/arch/arm/util/cs-etm.c
> @@ -643,7 +643,8 @@ static bool cs_etm_is_ete(struct perf_pmu *cs_etm_pmu, struct perf_cpu cpu)
>
>  static __u64 cs_etm_get_legacy_trace_id(struct perf_cpu cpu)
>  {
> -       return CORESIGHT_LEGACY_CPU_TRACE_ID(cpu.cpu);
> +       /* Wrap at 48 so that invalid trace IDs aren't saved into files. */
> +       return CORESIGHT_LEGACY_CPU_TRACE_ID(cpu.cpu % 48);
>  }
>
>  static void cs_etm_save_etmv4_header(__u64 data[], struct auxtrace_record *itr, struct perf_cpu cpu)
> --
> 2.34.1
>

Reviewed-by: Mike Leach <mike.leach@xxxxxxxxxx>

--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK