Hi Mike, On Mon, Jan 11, 2021 at 12:09:12PM +0000, Mike Leach wrote: > Hi Leo, > > I think there is an issue here in that your modification assumes that > all cpus in the system are of the same ETM type. The original routine > allowed for differing ETM types, thus differing cpu ETM field lengths > between ETMv4 / ETMv3, the field size was used after the relevant > magic number for the cpu ETM was read. > > You have replaced two different sizes - with a single calculated size.
Thanks for pointing out this. > Moving forwards we are seeing the newer FEAT_ETE protocol drivers > appearing on the list, which will ultimately need a new metadata > structure. > > We have had discussions within ARM regarding the changing of the > format to be more self describing - which should probably be opened > out to the CS mailing list. I think here have two options. One option is I think we can use __perf_cs_etmv3_magic/__perf_cs_etmv4_magic as indicator for the starting of next metadata array; when copy the metadata, always check the next item in the buffer, if it's __perf_cs_etmv3_magic or __perf_cs_etmv4_magic, will break loop and start copying metadata array for next CPU. The suggested change is pasted in below. Another option is I drop patches 03,05/07 in the series and leave the backward compatibility fixing for a saperate patch series with self describing method. Especially, if you think the first option will introduce trouble for enabling self describing later, then I am happy to drop patches 03,05. How about you think for this? Thanks, Leo ---8<--- diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index a2a369e2fbb6..edaec57362f0 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -2558,12 +2558,19 @@ int cs_etm__process_auxtrace_info(union perf_event *event, err = -ENOMEM; goto err_free_metadata; } - for (k = 0; k < CS_ETM_PRIV_MAX; k++) + for (k = 0; k < CS_ETM_PRIV_MAX; k++) { metadata[j][k] = ptr[i + k]; + if (ptr[i + k + 1] == __perf_cs_etmv3_magic || + ptr[i + k + 1] == __perf_cs_etmv4_magic) { + k++; + break; + } + } + /* The traceID is our handle */ idx = metadata[j][CS_ETM_ETMTRACEIDR]; - i += CS_ETM_PRIV_MAX; + i += k; } else if (ptr[i] == __perf_cs_etmv4_magic) { metadata[j] = zalloc(sizeof(*metadata[j]) * CS_ETMV4_PRIV_MAX); @@ -2571,12 +2578,19 @@ int cs_etm__process_auxtrace_info(union perf_event *event, err = -ENOMEM; goto err_free_metadata; } - for (k = 0; k < CS_ETMV4_PRIV_MAX; k++) + for (k = 0; k < CS_ETMV4_PRIV_MAX; k++) { metadata[j][k] = ptr[i + k]; + if (ptr[i + k + 1] == __perf_cs_etmv3_magic || + ptr[i + k + 1] == __perf_cs_etmv4_magic) { + k++; + break; + } + } + /* The traceID is our handle */ idx = metadata[j][CS_ETMV4_TRCTRACEIDR]; - i += CS_ETMV4_PRIV_MAX; + i += k; } /* Get an RB node for this CPU */