linux-kernel - [PATCH] libperf: fix alignment trap in perf stat

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Message-ID: <1566464769-16374-1-git-send-email-gerald.baeza@st.com>
Date:   Thu, 22 Aug 2019 09:07:01 +0000
From:   Gerald BAEZA <gerald.baeza@...com>
To:     "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Gerald BAEZA <gerald.baeza@...com>,
        Alexandre TORGUE <alexandre.torgue@...com>
Subject: [PATCH] libperf: fix alignment trap 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@...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 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);
-- 
2.7.4