perf record: Add new option to sample identifier

In preparation for recording sideband events in a virtual machine guest so
that they can be injected into a host perf.data file.

Add an option to always include sample type PERF_SAMPLE_IDENTIFIER.

Committer testing:

# perf record sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.020 MB perf.data (7 samples) ]
# perf evlist -v
cycles: size: 128, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
#
#
# perf record --sample-identifier sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.022 MB perf.data (7 samples) ]
# perf evlist -v
cycles: size: 128, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|IDENTIFIER, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
#

Signed-off-by: Adrian Hunter <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-record.txt

···
 --sample-cpu::
 	Record the sample cpu.
 
+--sample-identifier::
+	Record the sample identifier i.e. PERF_SAMPLE_IDENTIFIER bit set in
+	the sample_type member of the struct perf_event_attr argument to the
+	perf_event_open system call.
+
 -n::
 --no-samples::
 	Don't sample.

tools/perf/builtin-record.c

···
 	OPT_BOOLEAN(0, "code-page-size", &record.opts.sample_code_page_size,
 		    "Record the sampled code address (ip) page size"),
 	OPT_BOOLEAN(0, "sample-cpu", &record.opts.sample_cpu, "Record the sample cpu"),
+	OPT_BOOLEAN(0, "sample-identifier", &record.opts.sample_identifier,
+		    "Record the sample identifier"),
 	OPT_BOOLEAN_SET('T', "timestamp", &record.opts.sample_time,
 			&record.opts.sample_time_set,
 			"Record the sample timestamps"),

tools/perf/util/record.c

···
 	evlist__for_each_entry(evlist, evsel)
 		evsel__config_leader_sampling(evsel, evlist);
 
-	if (opts->full_auxtrace) {
+	if (opts->full_auxtrace || opts->sample_identifier) {
 		/*
 		 * Need to be able to synthesize and parse selected events with
 		 * arbitrary sample types, which requires always being able to

tools/perf/util/record.h

···
 	bool	      sample_time;
 	bool	      sample_time_set;
 	bool	      sample_cpu;
+	bool	      sample_identifier;
 	bool	      period;
 	bool	      period_set;
 	bool	      running_time;