linux-kernel - [PATCH v2] raid6/test/test.c: bug fix: Specify aligned(alignment) attributes to the char arrays

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Date:   Mon, 26 Sep 2016 14:37:38 -0700
From:   Gayatri Kammela <gayatri.kammela@...el.com>
To:     linux-raid@...r.kerenl.org
Cc:     linux-kernel@...r.kernel.org, shli@...nel.org,
        ravi.v.shankar@...el.com, fenghua.yu@...el.com,
        Gayatri Kammela <gayatri.kammela@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH v2] raid6/test/test.c: bug fix: Specify aligned(alignment) attributes to the char arrays

Specifying the aligned attributes to the char data[NDISKS][PAGE_SIZE],
char recovi[PAGE_SIZE] and char recovi[PAGE_SIZE] arrays, so that all
malloc memory is page boundary aligned.

Without these alignment attributes, the test causes a segfault in
userspace when the NDISKS are changed to 4 from 16.

The RAID stripes will be page aligned anyway, so we want to test what
the kernel actually will execute.

Cc: H. Peter Anvin <hpa@...or.com>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>
Signed-off-by: Gayatri Kammela <gayatri.kammela@...el.com>
Reviewed-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 lib/raid6/test/test.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/raid6/test/test.c b/lib/raid6/test/test.c
index 3bebbabdb510..b07f4d8e6b03 100644
--- a/lib/raid6/test/test.c
+++ b/lib/raid6/test/test.c
@@ -21,12 +21,13 @@
 
 #define NDISKS		16	/* Including P and Q */
 
-const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
+const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
 struct raid6_calls raid6_call;
 
 char *dataptrs[NDISKS];
-char data[NDISKS][PAGE_SIZE];
-char recovi[PAGE_SIZE], recovj[PAGE_SIZE];
+char data[NDISKS][PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+char recovi[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+char recovj[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
 
 static void makedata(int start, int stop)
 {
-- 
2.7.4