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Subject[PATCH 2/2] perf inject: Emit instruction records on ETM trace discontinuity
Date
There may be discontinuities in the ETM trace stream due to overflows or
ETM configuration for selective trace. This patch emits an instruction
sample with the pending branch stack when a TRACE ON packet occurs
indicating a discontinuity in the trace data.

A new packet type CS_ETM_TRACE_ON is added, which is emitted by the low
level decoder when a TRACE ON occurs. The higher level decoder flushes the
branch stack when this packet is emitted.

Signed-off-by: Robert Walker <robert.walker@arm.com>
---
tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 9 +++
tools/perf/util/cs-etm-decoder/cs-etm-decoder.h | 1 +
tools/perf/util/cs-etm.c | 84 +++++++++++++++++--------
3 files changed, 69 insertions(+), 25 deletions(-)

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 8ff69df..640af88 100644
--- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
+++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
@@ -328,7 +328,14 @@ cs_etm_decoder__buffer_range(struct cs_etm_decoder *decoder,
}

return ret;
+}

+static ocsd_datapath_resp_t
+cs_etm_decoder__buffer_trace_on(struct cs_etm_decoder *decoder,
+ const uint8_t trace_chan_id)
+{
+ return cs_etm_decoder__buffer_packet(decoder, trace_chan_id,
+ CS_ETM_TRACE_ON);
}

static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer(
@@ -347,6 +354,8 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer(
decoder->trace_on = false;
break;
case OCSD_GEN_TRC_ELEM_TRACE_ON:
+ resp = cs_etm_decoder__buffer_trace_on(decoder,
+ trace_chan_id);
decoder->trace_on = true;
break;
case OCSD_GEN_TRC_ELEM_INSTR_RANGE:
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 a4fdd28..743f5f4 100644
--- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
+++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
@@ -24,6 +24,7 @@ struct cs_etm_buffer {

enum cs_etm_sample_type {
CS_ETM_RANGE = 1 << 0,
+ CS_ETM_TRACE_ON = 1 << 1,
};

struct cs_etm_packet {
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 6777246..a8d07bd 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -866,6 +866,8 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
* PREV_PACKET is a branch.
*/
if (etm->synth_opts.last_branch &&
+ etmq->prev_packet &&
+ etmq->prev_packet->sample_type == CS_ETM_RANGE &&
etmq->prev_packet->last_instr_taken_branch)
cs_etm__update_last_branch_rb(etmq);

@@ -918,6 +920,40 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
return 0;
}

+static int cs_etm__flush(struct cs_etm_queue *etmq)
+{
+ int err = 0;
+ struct cs_etm_packet *tmp;
+
+ 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
+ * circular buffer at the end of the trace.
+ *
+ * Use the address of the end of the last reported execution
+ * range
+ */
+ u64 addr = cs_etm__last_executed_instr(etmq->prev_packet);
+
+ err = cs_etm__synth_instruction_sample(
+ etmq, addr,
+ etmq->period_instructions);
+ etmq->period_instructions = 0;
+
+ /*
+ * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
+ * the next incoming packet.
+ */
+ tmp = etmq->packet;
+ etmq->packet = etmq->prev_packet;
+ etmq->prev_packet = tmp;
+ }
+
+ return err;
+}
+
static int cs_etm__run_decoder(struct cs_etm_queue *etmq)
{
struct cs_etm_auxtrace *etm = etmq->etm;
@@ -946,20 +982,19 @@ static int cs_etm__run_decoder(struct cs_etm_queue *etmq)
/* Run trace decoder until buffer consumed or end of trace */
do {
processed = 0;
-
err = cs_etm_decoder__process_data_block(
etmq->decoder,
etmq->offset,
&buffer.buf[buffer_used],
buffer.len - buffer_used,
&processed);
-
if (err)
return err;

etmq->offset += processed;
buffer_used += processed;

+ /* Process each packet in this chunk */
while (1) {
err = cs_etm_decoder__get_packet(etmq->decoder,
etmq->packet);
@@ -970,32 +1005,31 @@ static int cs_etm__run_decoder(struct cs_etm_queue *etmq)
*/
break;

- /*
- * If the packet contains an instruction
- * range, generate instruction sequence
- * events.
- */
- if (etmq->packet->sample_type & CS_ETM_RANGE)
- err = cs_etm__sample(etmq);
+ switch (etmq->packet->sample_type) {
+ case CS_ETM_RANGE:
+ /*
+ * If the packet contains an instruction
+ * range, generate instruction sequence
+ * events.
+ */
+ cs_etm__sample(etmq);
+ break;
+ case CS_ETM_TRACE_ON:
+ /*
+ * Discontinuity in trace, flush
+ * previous branch stack
+ */
+ cs_etm__flush(etmq);
+ break;
+ default:
+ break;
+ }
}
} while (buffer.len > buffer_used);

- /*
- * Generate a last branch event for the branches left in
- * the circular buffer at the end of the trace.
- */
- if (etm->sample_instructions &&
- etmq->etm->synth_opts.last_branch) {
- struct branch_stack *bs = etmq->last_branch_rb;
- struct branch_entry *be =
- &bs->entries[etmq->last_branch_pos];
-
- err = cs_etm__synth_instruction_sample(
- etmq, be->to, etmq->period_instructions);
- if (err)
- return err;
- }
-
+ if (err == 0)
+ /* Flush any remaining branch stack entries */
+ err = cs_etm__flush(etmq);
}

return err;
--
2.7.4
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