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perf intel-pt: Ensure never to set 'last_ip' when packet 'count' is zero
authorAdrian Hunter <adrian.hunter@intel.com>
Fri, 26 May 2017 08:17:07 +0000 (11:17 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 27 Jul 2017 22:07:57 +0000 (15:07 -0700)
commit f952eaceb089b691eba7c4e13686e742a8f26bf5 upstream.

Intel PT uses IP compression based on the last IP. For decoding purposes,
'last IP' is not updated when a branch target has been suppressed, which is
indicated by IPBytes == 0. IPBytes is stored in the packet 'count', so
ensure never to set 'last_ip' when packet 'count' is zero.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-7-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tools/perf/util/intel-pt-decoder/intel-pt-decoder.c

index 958db8d..81c03c5 100644 (file)
@@ -1468,7 +1468,8 @@ static int intel_pt_walk_psbend(struct intel_pt_decoder *decoder)
 
                case INTEL_PT_FUP:
                        decoder->pge = true;
-                       intel_pt_set_last_ip(decoder);
+                       if (decoder->packet.count)
+                               intel_pt_set_last_ip(decoder);
                        break;
 
                case INTEL_PT_MODE_TSX:
@@ -1754,8 +1755,9 @@ next:
 
 static inline bool intel_pt_have_ip(struct intel_pt_decoder *decoder)
 {
-       return decoder->have_last_ip || decoder->packet.count == 0 ||
-              decoder->packet.count == 3 || decoder->packet.count == 6;
+       return decoder->packet.count &&
+              (decoder->have_last_ip || decoder->packet.count == 3 ||
+               decoder->packet.count == 6);
 }
 
 /* Walk PSB+ packets to get in sync. */