linux-kernel - [ 088/173] [SCSI] mvsas: fix undefined bit shift

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Date:	Fri, 28 Dec 2012 20:04:58 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Xi Wang <xi.wang@...il.com>,
	Xiangliang Yu <yuxiangl@...vell.com>,
	James Bottomley <JBottomley@...allels.com>
Subject: [ 088/173] [SCSI] mvsas: fix undefined bit shift

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xi Wang <xi.wang@...il.com>

commit beecadea1b8d67f591b13f7099559f32f3fd601d upstream.

The macro bit(n) is defined as ((u32)1 << n), and thus it doesn't work
with n >= 32, such as in mvs_94xx_assign_reg_set():

	if (i >= 32) {
		mvi->sata_reg_set |= bit(i);
		...
	}

The shift ((u32)1 << n) with n >= 32 also leads to undefined behavior.
The result varies depending on the architecture.

This patch changes bit(n) to do a 64-bit shift.  It also simplifies
mv_ffc64() using __ffs64(), since invoking ffz() with ~0 is undefined.

Signed-off-by: Xi Wang <xi.wang@...il.com>
Acked-by: Xiangliang Yu <yuxiangl@...vell.com>
Signed-off-by: James Bottomley <JBottomley@...allels.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/mvsas/mv_94xx.h |   14 ++------------
 drivers/scsi/mvsas/mv_sas.h  |    2 +-
 2 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/scsi/mvsas/mv_94xx.h b/drivers/scsi/mvsas/mv_94xx.h
index 8f7eb4f..487aa6f 100644
--- a/drivers/scsi/mvsas/mv_94xx.h
+++ b/drivers/scsi/mvsas/mv_94xx.h
@@ -258,21 +258,11 @@ enum sas_sata_phy_regs {
 #define SPI_ADDR_VLD_94XX         	(1U << 1)
 #define SPI_CTRL_SpiStart_94XX     	(1U << 0)
 
-#define mv_ffc(x)   ffz(x)
-
 static inline int
 mv_ffc64(u64 v)
 {
-	int i;
-	i = mv_ffc((u32)v);
-	if (i >= 0)
-		return i;
-	i = mv_ffc((u32)(v>>32));
-
-	if (i != 0)
-		return 32 + i;
-
-	return -1;
+	u64 x = ~v;
+	return x ? __ffs64(x) : -1;
 }
 
 #define r_reg_set_enable(i) \
diff --git a/drivers/scsi/mvsas/mv_sas.h b/drivers/scsi/mvsas/mv_sas.h
index c04a4f5..da24955 100644
--- a/drivers/scsi/mvsas/mv_sas.h
+++ b/drivers/scsi/mvsas/mv_sas.h
@@ -69,7 +69,7 @@ extern struct kmem_cache *mvs_task_list_cache;
 #define DEV_IS_EXPANDER(type)	\
 	((type == EDGE_DEV) || (type == FANOUT_DEV))
 
-#define bit(n) ((u32)1 << n)
+#define bit(n) ((u64)1 << n)
 
 #define for_each_phy(__lseq_mask, __mc, __lseq)			\
 	for ((__mc) = (__lseq_mask), (__lseq) = 0;		\


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