perf auxtrace: Add option to synthesize branch stacks on samples

Add AUX area tracing option 'l' to synthesize branch stacks on samples
just like sample type PERF_SAMPLE_BRANCH_STACK.  This is taken into use
by Intel PT in a subsequent patch.
Based-on-patch-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-9-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/itrace.txt

@@ -6,6 +6,7 @@
 		e	synthesize error events
 		d	create a debug log
 		g	synthesize a call chain (use with i or x)
+		l	synthesize last branch entries (use with i or x)
 
 	The default is all events i.e. the same as --itrace=ibxe
 
@@ -20,3 +21,6 @@
 
 	Also the call chain size (default 16, max. 1024) for instructions or
 	transactions events can be specified.
+
+	Also the number of last branch entries (default 64, max. 1024) for
+	instructions or transactions events can be specified.

tools/perf/util/auxtrace.c

@@ -926,6 +926,8 @@ s64 perf_event__process_auxtrace(struct perf_tool *tool,
 #define PERF_ITRACE_DEFAULT_PERIOD		100000
 #define PERF_ITRACE_DEFAULT_CALLCHAIN_SZ	16
 #define PERF_ITRACE_MAX_CALLCHAIN_SZ		1024
+#define PERF_ITRACE_DEFAULT_LAST_BRANCH_SZ	64
+#define PERF_ITRACE_MAX_LAST_BRANCH_SZ		1024
 
 void itrace_synth_opts__set_default(struct itrace_synth_opts *synth_opts)
 {
@@ -936,6 +938,7 @@ void itrace_synth_opts__set_default(struct itrace_synth_opts *synth_opts)
 	synth_opts->period_type = PERF_ITRACE_DEFAULT_PERIOD_TYPE;
 	synth_opts->period = PERF_ITRACE_DEFAULT_PERIOD;
 	synth_opts->callchain_sz = PERF_ITRACE_DEFAULT_CALLCHAIN_SZ;
+	synth_opts->last_branch_sz = PERF_ITRACE_DEFAULT_LAST_BRANCH_SZ;
 }
 
 /*
@@ -1043,6 +1046,23 @@ int itrace_parse_synth_opts(const struct option *opt, const char *str,
 				synth_opts->callchain_sz = val;
 			}
 			break;
+		case 'l':
+			synth_opts->last_branch = true;
+			synth_opts->last_branch_sz =
+					PERF_ITRACE_DEFAULT_LAST_BRANCH_SZ;
+			while (*p == ' ' || *p == ',')
+				p += 1;
+			if (isdigit(*p)) {
+				unsigned int val;
+
+				val = strtoul(p, &endptr, 10);
+				p = endptr;
+				if (!val ||
+				    val > PERF_ITRACE_MAX_LAST_BRANCH_SZ)
+					goto out_err;
+				synth_opts->last_branch_sz = val;
+			}
+			break;
 		case ' ':
 		case ',':
 			break;

tools/perf/util/auxtrace.h

@@ -63,7 +63,9 @@ enum itrace_period_type {
  * @calls: limit branch samples to calls (can be combined with @returns)
  * @returns: limit branch samples to returns (can be combined with @calls)
  * @callchain: add callchain to 'instructions' events
+ * @last_branch: add branch context to 'instruction' events
  * @callchain_sz: maximum callchain size
+ * @last_branch_sz: branch context size
  * @period: 'instructions' events period
  * @period_type: 'instructions' events period type
  */
@@ -79,7 +81,9 @@ struct itrace_synth_opts {
 	bool			calls;
 	bool			returns;
 	bool			callchain;
+	bool			last_branch;
 	unsigned int		callchain_sz;
+	unsigned int		last_branch_sz;
 	unsigned long long	period;
 	enum itrace_period_type	period_type;
 };