linux-kernel - [PATCH v4 05/17] perf: cs-etm: Only save valid trace IDs into files

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Message-Id: <20240625133105.671245-6-james.clark@arm.com>
Date: Tue, 25 Jun 2024 14:30:48 +0100
From: James Clark <james.clark@....com>
To: coresight@...ts.linaro.org,
	suzuki.poulose@....com,
	gankulkarni@...amperecomputing.com,
	mike.leach@...aro.org,
	leo.yan@...ux.dev,
	anshuman.khandual@....com,
	jszu@...dia.com,
	bwicaksono@...dia.com
Cc: James Clark <james.clark@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	John Garry <john.g.garry@...cle.com>,
	Will Deacon <will@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-perf-users@...r.kernel.org
Subject: [PATCH v4 05/17] perf: cs-etm: Only save valid trace IDs into files

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@....com>
---
 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