[tip: perf/core] libperf: Fix alignment trap with xyarray contents in 'perf stat'

[tip-bot2 for Gerald BAEZA]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     d9c5c083416500e95da098c01be092b937def7fa
Gitweb:        https://git.kernel.org/tip/d9c5c083416500e95da098c01be092b937def7fa
Author:        Gerald BAEZA <gerald.baeza@xxxxxx>
AuthorDate:    Thu, 22 Aug 2019 09:07:01 
Committer:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitterDate: Thu, 22 Aug 2019 17:16:57 -03:00

libperf: Fix alignment trap with xyarray contents in 'perf stat'

Following the patch 'perf stat: Fix --no-scale', an alignment trap
happens in process_counter_values() on ARMv7 platforms due to the
attempt to copy non 64 bits aligned double words (pointed by 'count')
via a NEON vectored instruction ('vld1' with 64 bits alignment
constraint).

This patch sets a 64 bits alignment constraint on 'contents[]' field in
'struct xyarray' since the 'count' pointer used above points to such a
structure.

Signed-off-by: Gerald Baeza <gerald.baeza@xxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Alexandre Torgue <alexandre.torgue@xxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1566464769-16374-1-git-send-email-gerald.baeza@xxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/lib/include/internal/xyarray.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/lib/include/internal/xyarray.h b/tools/perf/lib/include/internal/xyarray.h
index 3bf70e4..51e35d6 100644
--- a/tools/perf/lib/include/internal/xyarray.h
+++ b/tools/perf/lib/include/internal/xyarray.h
@@ -2,6 +2,7 @@
 #ifndef __LIBPERF_INTERNAL_XYARRAY_H
 #define __LIBPERF_INTERNAL_XYARRAY_H
 
+#include <linux/compiler.h>
 #include <sys/types.h>
 
 struct xyarray {
@@ -10,7 +11,7 @@ struct xyarray {
 	size_t entries;
 	size_t max_x;
 	size_t max_y;
-	char contents[];
+	char contents[] __aligned(8);
 };
 
 struct xyarray *xyarray__new(int xlen, int ylen, size_t entry_size);