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From: Peter Rosin <peda@axentia.se>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Peter Rosin <peda@axentia.se>,
	Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH RESEND 2/3] lib/test_string: avoid masking memset16/32/64 failures
Date: Mon, 6 May 2019 12:47:07 +0000
Message-ID: <20190506124634.6807-3-peda@axentia.se> (raw)
In-Reply-To: <20190506124634.6807-1-peda@axentia.se>

If a memsetXX implementation is completely broken and fails in the first
iteration, when i, j, and k are all zero, the failure is masked as zero
is returned. Failing in the first iteration is perhaps the most likely
failure, so this makes the tests pretty much useless. Avoid the situation
by always setting a random unused bit in the result on failure.

Fixes: 03270c13c5ff ("lib/string.c: add testcases for memset16/32/64")
Signed-off-by: Peter Rosin <peda@axentia.se>
---
 lib/test_string.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/test_string.c b/lib/test_string.c
index 0fcdb82dca86..98a787e7a1fd 100644
--- a/lib/test_string.c
+++ b/lib/test_string.c
@@ -35,7 +35,7 @@ static __init int memset16_selftest(void)
 fail:
 	kfree(p);
 	if (i < 256)
-		return (i << 24) | (j << 16) | k;
+		return (i << 24) | (j << 16) | k | 0x8000;
 	return 0;
 }
 
@@ -71,7 +71,7 @@ static __init int memset32_selftest(void)
 fail:
 	kfree(p);
 	if (i < 256)
-		return (i << 24) | (j << 16) | k;
+		return (i << 24) | (j << 16) | k | 0x8000;
 	return 0;
 }
 
@@ -107,7 +107,7 @@ static __init int memset64_selftest(void)
 fail:
 	kfree(p);
 	if (i < 256)
-		return (i << 24) | (j << 16) | k;
+		return (i << 24) | (j << 16) | k | 0x8000;
 	return 0;
 }
 
-- 
2.11.0


  parent reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06 12:46 [PATCH RESEND 0/3] lib/string: search for NUL with strchr/strnchr Peter Rosin
2019-05-06 12:47 ` [PATCH RESEND 1/3] lib/string: allow searching for NUL with strnchr Peter Rosin
2019-05-06 12:47 ` Peter Rosin [this message]
2019-05-06 12:47 ` [PATCH RESEND 3/3] lib/test_string: add some testcases for strchr and strnchr Peter Rosin

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