perf intel-pt: Fix last_ip usage

Intel PT uses IP compression based on the last IP. For decoding
purposes, 'last IP' is considered to be reset to zero whenever there is
a synchronization packet (PSB). The decoder wasn't doing that, and was
treating the zero value to mean that there was no last IP, whereas
compression can be done against the zero value. Fix by setting last_ip
to zero when a PSB is received and keep track of have_last_ip.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1495786658-18063-6-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/intel-pt-decoder/intel-pt-decoder.c

@@ -111,6 +111,7 @@ struct intel_pt_decoder {
 	bool have_tma;
 	bool have_cyc;
 	bool fixup_last_mtc;
+	bool have_last_ip;
 	uint64_t pos;
 	uint64_t last_ip;
 	uint64_t ip;
@@ -419,6 +420,7 @@ static uint64_t intel_pt_calc_ip(const struct intel_pt_pkt *packet,
 static inline void intel_pt_set_last_ip(struct intel_pt_decoder *decoder)
 {
 	decoder->last_ip = intel_pt_calc_ip(&decoder->packet, decoder->last_ip);
+	decoder->have_last_ip = true;
 }
 
 static inline void intel_pt_set_ip(struct intel_pt_decoder *decoder)
@@ -1672,6 +1674,8 @@ next:
 			break;
 
 		case INTEL_PT_PSB:
+			decoder->last_ip = 0;
+			decoder->have_last_ip = true;
 			intel_pt_clear_stack(&decoder->stack);
 			err = intel_pt_walk_psbend(decoder);
 			if (err == -EAGAIN)
@@ -1752,7 +1756,7 @@ next:
 
 static inline bool intel_pt_have_ip(struct intel_pt_decoder *decoder)
 {
-	return decoder->last_ip || decoder->packet.count == 0 ||
+	return decoder->have_last_ip || decoder->packet.count == 0 ||
 	       decoder->packet.count == 3 || decoder->packet.count == 6;
 }
 
@@ -1882,7 +1886,7 @@ static int intel_pt_walk_to_ip(struct intel_pt_decoder *decoder)
 				if (decoder->ip)
 					return 0;
 			}
-			if (decoder->packet.count)
+			if (decoder->packet.count && decoder->have_last_ip)
 				intel_pt_set_last_ip(decoder);
 			break;
 
@@ -1932,6 +1936,8 @@ static int intel_pt_walk_to_ip(struct intel_pt_decoder *decoder)
 			break;
 
 		case INTEL_PT_PSB:
+			decoder->last_ip = 0;
+			decoder->have_last_ip = true;
 			intel_pt_clear_stack(&decoder->stack);
 			err = intel_pt_walk_psb(decoder);
 			if (err)
@@ -2066,6 +2072,7 @@ static int intel_pt_sync(struct intel_pt_decoder *decoder)
 
 	decoder->pge = false;
 	decoder->continuous_period = false;
+	decoder->have_last_ip = false;
 	decoder->last_ip = 0;
 	decoder->ip = 0;
 	intel_pt_clear_stack(&decoder->stack);
@@ -2074,6 +2081,7 @@ static int intel_pt_sync(struct intel_pt_decoder *decoder)
 	if (err)
 		return err;
 
+	decoder->have_last_ip = true;
 	decoder->pkt_state = INTEL_PT_STATE_NO_IP;
 
 	err = intel_pt_walk_psb(decoder);
@@ -2116,6 +2124,7 @@ const struct intel_pt_state *intel_pt_decode(struct intel_pt_decoder *decoder)
 			err = intel_pt_sync(decoder);
 			break;
 		case INTEL_PT_STATE_NO_IP:
+			decoder->have_last_ip = false;
 			decoder->last_ip = 0;
 			decoder->ip = 0;
 			/* Fall through */