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

[James Clark]

On 13/09/2024 12:54, Leo Yan wrote:
> 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

I asked Mike the same question about ETMv3 and he said none of the flags 
overlap and it was ok to always pass them. So I assume the same applies 
to ETE as well.