Subject: Re: [PATCH v3 3/6] perf cs-etm: Support thread stack

From: Mathieu Poirier <[email-masked]>
Date: Fri, 11 Oct 2019 11:53:53 -0600

On Sat, Oct 05, 2019 at 05:16:11PM +0800, Leo Yan wrote:
> Since Arm CoreSight doesn't support thread stack, the decoding cannot
> display symbols with indented spaces to reflect the stack depth.
> 
> This patch adds support thread stack for Arm CoreSight, this allows
> 'perf script' to display properly for option '-F,+callindent'.
> 
> Before:
> 
>   # perf script -F,+callindent
>             main  2808          1          branches: coresight_test1                      ffff8634f5c8 coresight_test1+0x3c (/root/coresight_test/libcstest.so)
>             main  2808          1          branches: printf@plt                           aaaaba8d37ec main+0x28 (/root/coresight_test/main)
>             main  2808          1          branches: printf@plt                           aaaaba8d36bc printf@plt+0xc (/root/coresight_test/main)
>             main  2808          1          branches: _init                                aaaaba8d3650 _init+0x30 (/root/coresight_test/main)
>             main  2808          1          branches: _dl_fixup                            ffff86373b4c _dl_runtime_resolve+0x40 (/lib/aarch64-linux-gnu/ld-2.28.so)
>             main  2808          1          branches: _dl_lookup_symbol_x                  ffff8636e078 _dl_fixup+0xb8 (/lib/aarch64-linux-gnu/ld-2.28.so)
>   [...]
> 
> After:
> 
>   # perf script -F,+callindent
>             main  2808          1          branches:                 coresight_test1                                      ffff8634f5c8 coresight_test1+0x3c (/root/coresight_test/libcstest.so)
>             main  2808          1          branches:                 printf@plt                                           aaaaba8d37ec main+0x28 (/root/coresight_test/main)
>             main  2808          1          branches:                     printf@plt                                       aaaaba8d36bc printf@plt+0xc (/root/coresight_test/main)
>             main  2808          1          branches:                     _init                                            aaaaba8d3650 _init+0x30 (/root/coresight_test/main)
>             main  2808          1          branches:                     _dl_fixup                                        ffff86373b4c _dl_runtime_resolve+0x40 (/lib/aarch64-linux-gnu/ld-2.28.s
>             main  2808          1          branches:                         _dl_lookup_symbol_x                          ffff8636e078 _dl_fixup+0xb8 (/lib/aarch64-linux-gnu/ld-2.28.so)
>   [...]
> 
> Signed-off-by: Leo Yan <[email-masked]>
> ---
>  tools/perf/util/cs-etm.c | 44 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 58ceba7b91d5..780abbfd1833 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -1117,6 +1117,45 @@ static void cs_etm__copy_insn(struct cs_etm_queue *etmq,
>  			   sample->insn_len, (void *)sample->insn);
>  }
>  
> +static void cs_etm__add_stack_event(struct cs_etm_queue *etmq,
> +				    struct cs_etm_traceid_queue *tidq)
> +{
> +	struct cs_etm_auxtrace *etm = etmq->etm;
> +	u8 trace_chan_id = tidq->trace_chan_id;
> +	int insn_len;
> +	u64 from_ip, to_ip;
> +
> +	if (etm->synth_opts.thread_stack) {
> +		from_ip = cs_etm__last_executed_instr(tidq->prev_packet);
> +		to_ip = cs_etm__first_executed_instr(tidq->packet);
> +
> +		insn_len = cs_etm__instr_size(etmq, trace_chan_id,
> +					      tidq->prev_packet->isa, from_ip);
> +
> +		/*
> +		 * Create thread stacks by keeping track of calls and returns;
> +		 * any call pushes thread stack, return pops the stack, and
> +		 * flush stack when the trace is discontinuous.
> +		 */
> +		thread_stack__event(tidq->thread, tidq->prev_packet->cpu,
> +				    tidq->prev_packet->flags,
> +				    from_ip, to_ip, insn_len,
> +				    etmq->buffer->buffer_nr);

Details are a little fuzzy in my head but I'm pretty sure
we want trace_chan_id here.  

> +	} else {
> +		/*
> +		 * The thread stack can be output via thread_stack__process();
> +		 * thus the detailed information about paired calls and returns
> +		 * will be facilitated by Python script for the db-export.
> +		 *
> +		 * Need to set trace buffer number and flush thread stack if the
> +		 * trace buffer number has been alternate.
> +		 */
> +		thread_stack__set_trace_nr(tidq->thread,
> +					   tidq->prev_packet->cpu,
> +					   etmq->buffer->buffer_nr);

Same here.

> +	}
> +}
> +
>  static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq,
>  					    struct cs_etm_traceid_queue *tidq,
>  					    u64 addr, u64 period)
> @@ -1393,6 +1432,9 @@ static int cs_etm__sample(struct cs_etm_queue *etmq,
>  		tidq->period_instructions = instrs_over;
>  	}
>  
> +	if (tidq->prev_packet->last_instr_taken_branch)
> +		cs_etm__add_stack_event(etmq, tidq);
> +
>  	if (etm->sample_branches) {
>  		bool generate_sample = false;
>  
> @@ -2593,6 +2635,8 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
>  		itrace_synth_opts__set_default(&etm->synth_opts,
>  				session->itrace_synth_opts->default_no_sample);
>  		etm->synth_opts.callchain = false;
> +		etm->synth_opts.thread_stack =
> +				session->itrace_synth_opts->thread_stack;
>  	}
>  
>  	err = cs_etm__synth_events(etm, session);
> -- 
> 2.17.1
> 

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