On Wed, Feb 07, 2018 at 01:57:25PM +0000, Robert Walker wrote:
> 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.wal...@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;
> -

this...

>                       err = cs_etm_decoder__process_data_block(
>                               etmq->decoder,
>                               etmq->offset,
>                               &buffer.buf[buffer_used],
>                               buffer.len - buffer_used,
>                               &processed);
> -

and this should have gone in the first patch.

>                       if (err)
>                               return err;
>  
>                       etmq->offset += processed;
>                       buffer_used += processed;
>  
> +                     /* Process each packet in this chunk */

And probably this too.

With the above changes:

Acked-by: Mathieu Poirier <mathieu.poir...@linaro.org>

>                       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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