perf intel-pt: Fix overlap calculation for padding

Auxtrace records might have up to 7 bytes of padding appended. Adjust
the overlap accordingly.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20190206103947.15750-3-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 34 insertions, 2 deletions

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 4503f3ca45ab..ecd25cdc1d3e 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -26,6 +26,7 @@
 
 #include "../cache.h"
 #include "../util.h"
+#include "../auxtrace.h"
 
 #include "intel-pt-insn-decoder.h"
 #include "intel-pt-pkt-decoder.h"
@@ -2575,6 +2576,34 @@ static int intel_pt_tsc_cmp(uint64_t tsc1, uint64_t tsc2)
         }
 }
 
+#define MAX_PADDING (PERF_AUXTRACE_RECORD_ALIGNMENT - 1)
+
+/**
+ * adj_for_padding - adjust overlap to account for padding.
+ * @buf_b: second buffer
+ * @buf_a: first buffer
+ * @len_a: size of first buffer
+ *
+ * @buf_a might have up to 7 bytes of padding appended. Adjust the overlap
+ * accordingly.
+ *
+ * Return: A pointer into @buf_b from where non-overlapped data starts
+ */
+static unsigned char *adj_for_padding(unsigned char *buf_b,
+                                      unsigned char *buf_a, size_t len_a)
+{
+        unsigned char *p = buf_b - MAX_PADDING;
+        unsigned char *q = buf_a + len_a - MAX_PADDING;
+        int i;
+
+        for (i = MAX_PADDING; i; i--, p++, q++) {
+                if (*p != *q)
+                        break;
+        }
+
+        return p;
+}
+
 /**
  * intel_pt_find_overlap_tsc - determine start of non-overlapped trace data
  *                             using TSC.
@@ -2625,8 +2654,11 @@ static unsigned char *intel_pt_find_overlap_tsc(unsigned char *buf_a,
 
                         /* Same TSC, so buffers are consecutive */
                         if (!cmp && rem_b >= rem_a) {
+                                unsigned char *start;
+
                                 *consecutive = true;
-                                return buf_b + len_b - (rem_b - rem_a);
+                                start = buf_b + len_b - (rem_b - rem_a);
+                                return adj_for_padding(start, buf_a, len_a);
                         }
                         if (cmp < 0)
                                 return buf_b; /* tsc_a < tsc_b => no overlap */
@@ -2689,7 +2721,7 @@ unsigned char *intel_pt_find_overlap(unsigned char *buf_a, size_t len_a,
                 found = memmem(buf_a, len_a, buf_b, len_a);
                 if (found) {
                         *consecutive = true;
-                        return buf_b + len_a;
+                        return adj_for_padding(buf_b + len_a, buf_a, len_a);
                 }
 
                 /* Try again at next PSB in buffer 'a' */