linux-kernel - [PATCH 25/25] libperf: Fix alignment trap with xyarray contents in 'perf stat'

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Date:   Thu, 22 Aug 2019 18:01:00 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Gerald BAEZA <gerald.baeza@...com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 25/25] libperf: Fix alignment trap with xyarray contents in 'perf stat'

From: Gerald BAEZA <gerald.baeza@...com>

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@...com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@...com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1566464769-16374-1-git-send-email-gerald.baeza@st.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 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 3bf70e4d474c..51e35d6c8ec4 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);
-- 
2.21.0