[PATCH v2 2/2] perf cs-etm: Add support sample flags

[Leo Yan]

We have prepared the flags in the packet structure, so need to copy
the related value into sample structure thus perf tool can facilitate
sample flags.

The PREV_PACKET contains the branch instruction flags and PACKET
actually contains the flags for next branch instruction.  So this patch
is to set sample flags with 'etmq->prev_packet->flags'.

This patch includes three fixing up for sample flags based on the
packets context:

- If the packet is exception packet or exception return packet, update
  the previous packet for exception specific flags;
- If there has TRACE_ON or TRACE_OFF packet in the middle of instruction
  packets, this indicates the trace is discontinuous, so append the flag
  PERF_IP_FLAG_TRACE_END to the previous packet to indicate the trace
  has been ended;
- If one instruction packet is behind TRACE_OFF packet, this instruction
  is restarting trace packet.  So set flag PERF_IP_FLAG_TRACE_START to
  TRACE_OFF packet if one, this flag isn't used by TRACE_OFF packet but
  used to indicate trace restarting when generate sample.

Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
---
 tools/perf/util/cs-etm.c | 43 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 455f132..afca6f3 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -676,7 +676,7 @@ static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq,
 	sample.stream_id = etmq->etm->instructions_id;
 	sample.period = period;
 	sample.cpu = etmq->packet->cpu;
-	sample.flags = 0;
+	sample.flags = etmq->prev_packet->flags;
 	sample.insn_len = 1;
 	sample.cpumode = event->sample.header.misc;
 
@@ -735,7 +735,7 @@ static int cs_etm__synth_branch_sample(struct cs_etm_queue *etmq)
 	sample.stream_id = etmq->etm->branches_id;
 	sample.period = 1;
 	sample.cpu = etmq->packet->cpu;
-	sample.flags = 0;
+	sample.flags = etmq->prev_packet->flags;
 	sample.cpumode = event->sample.header.misc;
 
 	/*
@@ -878,6 +878,43 @@ static int cs_etm__synth_events(struct cs_etm_auxtrace *etm,
 	return 0;
 }
 
+static void cs_etm__fixup_flags(struct cs_etm_queue *etmq)
+{
+	/*
+	 * Decoding stream might insert one TRACE_OFF packet in the
+	 * middle of instruction packets, this means it doesn't
+	 * contain the pair packets with TRACE_OFF and TRACE_ON.
+	 * For this case, the instruction packet follows with
+	 * TRACE_OFF packet so we need to fixup prev_packet with flag
+	 * PERF_IP_FLAG_TRACE_BEGIN, this flag finally is used by the
+	 * instruction packet to generate samples.
+	 */
+	if (etmq->prev_packet->sample_type == CS_ETM_TRACE_OFF &&
+	    etmq->packet->sample_type == CS_ETM_RANGE)
+		etmq->prev_packet->flags = PERF_IP_FLAG_BRANCH |
+					   PERF_IP_FLAG_TRACE_BEGIN;
+
+	if (etmq->prev_packet->sample_type == CS_ETM_RANGE) {
+		/*
+		 * When the exception packet is inserted, update flags
+		 * so tell perf it is exception related branches.
+		 */
+		if (etmq->packet->sample_type == CS_ETM_EXCEPTION ||
+		    etmq->packet->sample_type == CS_ETM_EXCEPTION_RET)
+			etmq->prev_packet->flags = etmq->packet->flags;
+
+		/*
+		 * The trace is discontinuous, weather this is caused by
+		 * TRACE_ON packet or TRACE_OFF packet is coming, if the
+		 * previous packet is instruction packet, simply set flag
+		 * PERF_IP_FLAG_TRACE_END for previous packet.
+		 */
+		if (etmq->packet->sample_type == CS_ETM_TRACE_ON ||
+		    etmq->packet->sample_type == CS_ETM_TRACE_OFF)
+			etmq->prev_packet->flags |= PERF_IP_FLAG_TRACE_END;
+	}
+}
+
 static int cs_etm__sample(struct cs_etm_queue *etmq)
 {
 	struct cs_etm_auxtrace *etm = etmq->etm;
@@ -1100,6 +1137,8 @@ static int cs_etm__run_decoder(struct cs_etm_queue *etmq)
 					 */
 					break;
 
+				cs_etm__fixup_flags(etmq);
+
 				switch (etmq->packet->sample_type) {
 				case CS_ETM_RANGE:
 					/*
-- 
2.7.4