Re: [PATCH v2 2/7] perf cs-etm: Use new OpenCSD consistency checks

[Leo Yan]

On 9/12/24 16:11, James Clark wrote:> 
> Previously when the incorrect binary was used for decode, Perf would
> silently continue to generate incorrect samples. With OpenCSD 1.5.4 we
> can enable consistency checks that do a best effort to detect a mismatch
> in the image. When one is detected a warning is printed and sample
> generation stops until the trace resynchronizes with a good part of the
> image.
>
> Reported-by: Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/all/20240719092619.274730-1-gankulkarni@xxxxxxxxxxxxxxxxxxxxxx/
> Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
> ---
>   tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> index b78ef0262135..b85a8837bddc 100644
> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> @@ -685,9 +685,14 @@ cs_etm_decoder__create_etm_decoder(struct cs_etm_decoder_params *d_params,
>          }
>
>          if (d_params->operation == CS_ETM_OPERATION_DECODE) {
> +               int decode_flags = OCSD_CREATE_FLG_FULL_DECODER;
> +#ifdef OCSD_OPFLG_N_UNCOND_DIR_BR_CHK
> +               decode_flags |= OCSD_OPFLG_N_UNCOND_DIR_BR_CHK | OCSD_OPFLG_CHK_RANGE_CONTINUE |
> +                               ETM4_OPFLG_PKTDEC_AA64_OPCODE_CHK;
> +#endif

Looks good to me.

Just one question: should the flag ETM4_OPFLG_PKTDEC_AA64_OPCODE_CHK be set
according to ETM version? E.g. it should be only set for ETMv4 or this is
fine for ETE as well.

Thanks,
Leo

>                  if (ocsd_dt_create_decoder(decoder->dcd_tree,
>                                             decoder->decoder_name,
> -                                          OCSD_CREATE_FLG_FULL_DECODER,
> +                                          decode_flags,
>                                             trace_config, &csid))
>                          return -1;
>
> --
> 2.34.1