Patch "perf evsel: Fix swap for samples with raw data" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

perf evsel: Fix swap for samples with raw data

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-evsel-fix-swap-for-samples-with-raw-data.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jiri Olsa <[email protected]>
Date: Wed, 29 Nov 2017 19:43:46 +0100
Subject: perf evsel: Fix swap for samples with raw data

From: Jiri Olsa <[email protected]>

[ Upstream commit f9d8adb345d7adbb2d3431eea73beb89c8d6d612 ]

When we detect a different endianity we swap event before processing. It's tricky for samples because we have no idea what's inside. We treat it as an array of u64s, swap them and later on we swap back parts which are different.

We mangle this way also the tracepoint raw data, which ends up in report showing wrong data:

1.95% comm=Q^B pid=29285 prio=16777216 target_cpu=000 1.67% comm=l^B pid=0 prio=16777216 target_cpu=000

Luckily the traceevent library handles the endianity by itself (thank you Steven!), so we can pass the RAW data directly in the other endianity.

2.51% comm=beah-rhts-task pid=1175 prio=120 target_cpu=002 2.23% comm=kworker/0:0 pid=11566 prio=120 target_cpu=000

The fix is basically to swap back the raw data if different endianity is detected.

---
 tools/perf/util/evsel.c            |   20 +++++++++++++++++---
 tools/perf/util/python-ext-sources |    1 +
 2 files changed, 18 insertions(+), 3 deletions(-)

@@ -36,6 +36,7 @@
 #include "debug.h"
 #include "trace-event.h"
 #include "stat.h"
+#include "memswap.h"
 #include "util/parse-branch-options.h"
 
 #include "sane_ctype.h"

@@ -2120,14 +2121,27 @@ int perf_evsel__parse_sample(struct perf
 	if (type & PERF_SAMPLE_RAW) {
 		OVERFLOW_CHECK_u64(array);
 		u.val64 = *array;
-		if (WARN_ONCE(swapped,
-			      "Endianness of raw data not corrected!\n")) {
-			/* undo swap of u64, then swap on individual u32s */
+
+		/*
+		 * Undo swap of u64, then swap on individual u32s,
+		 * get the size of the raw area and undo all of the
+		 * swap. The pevent interface handles endianity by
+		 * itself.
+		 */
+		if (swapped) {
 			u.val64 = bswap_64(u.val64);
 			u.val32[0] = bswap_32(u.val32[0]);
 			u.val32[1] = bswap_32(u.val32[1]);
 		}
 		data->raw_size = u.val32[0];
+
+		/*
+		 * The raw data is aligned on 64bits including the
+		 * u32 size, so it's safe to use mem_bswap_64.
+		 */
+		if (swapped)
+			mem_bswap_64((void *) array, data->raw_size);
+
 		array = (void *)array + sizeof(u32);
 
 		OVERFLOW_CHECK(array, data->raw_size, max_size);

@@ -10,6 +10,7 @@ util/ctype.c
 util/evlist.c
 util/evsel.c
 util/cpumap.c
+util/memswap.c
 util/mmap.c
 util/namespaces.c
 ../lib/bitmap.c

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/perf-evsel-fix-swap-for-samples-with-raw-data.patch queue-4.15/perf-tools-fix-copyfile_offset-update-of-output-offset.patch queue-4.15/perf-report-fix-a-no-annotate-browser-displayed-issue.patch