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Subject[PATCH 2/5] perf intel-pt: Fix overlap calculation for padding
Date
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: stable@vger.kernel.org
---
.../util/intel-pt-decoder/intel-pt-decoder.c | 36 +++++++++++++++++--
1 file 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' */
--
2.17.1
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