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.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
index c4993b2..7f10430a 100644
--- a/tools/perf/util/auxtrace.c
+++ b/tools/perf/util/auxtrace.c
@@ -926,6 +926,8 @@
 #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 @@
 	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 @@
 				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;