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Subject[PATCH v2 3/6] perf cs-etm: Fix start tracing packet handling
Date
Usually the start tracing packet is a CS_ETM_TRACE_ON packet, this
packet is passed to cs_etm__flush(); cs_etm__flush() will check the
condition 'prev_packet->sample_type == CS_ETM_RANGE' but 'prev_packet'
is allocated by zalloc() so 'prev_packet->sample_type' is zero in
initialization and this condition is false. So cs_etm__flush() will
directly bail out without handling the start tracing packet.

This patch is to introduce a new sample type CS_ETM_EMPTY, which is used
to indicate the packet is an empty packet. cs_etm__flush() will swap
packets when it finds the previous packet is empty, so this can record
the start tracing packet into 'etmq->prev_packet'.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
tools/perf/util/cs-etm-decoder/cs-etm-decoder.h | 1 +
tools/perf/util/cs-etm.c | 19 ++++++++++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
index 743f5f4..612b575 100644
--- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
+++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
@@ -23,6 +23,7 @@ struct cs_etm_buffer {
};

enum cs_etm_sample_type {
+ CS_ETM_EMPTY = 0,
CS_ETM_RANGE = 1 << 0,
CS_ETM_TRACE_ON = 1 << 1,
};
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 8b2c099..ae7c9c88 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -924,8 +924,14 @@ static int cs_etm__flush(struct cs_etm_queue *etmq)
int err = 0;
struct cs_etm_packet *tmp;

+ if (!etmq->prev_packet)
+ return 0;
+
+ /* Handle start tracing packet */
+ if (etmq->prev_packet->sample_type == CS_ETM_EMPTY)
+ goto swap_packet;
+
if (etmq->etm->synth_opts.last_branch &&
- etmq->prev_packet &&
etmq->prev_packet->sample_type == CS_ETM_RANGE) {
/*
* Generate a last branch event for the branches left in the
@@ -944,6 +950,10 @@ static int cs_etm__flush(struct cs_etm_queue *etmq)

etmq->period_instructions = 0;

+ }
+
+swap_packet:
+ if (etmq->etm->synth_opts.last_branch) {
/*
* Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
* the next incoming packet.
@@ -1023,6 +1033,13 @@ static int cs_etm__run_decoder(struct cs_etm_queue *etmq)
*/
cs_etm__flush(etmq);
break;
+ case CS_ETM_EMPTY:
+ /*
+ * Should not receive empty packet,
+ * report error.
+ */
+ pr_err("CS ETM Trace: empty packet\n");
+ return -EINVAL;
default:
break;
}
--
2.7.4
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