linux-kernel - [PATCH v2] [SCSI] mvsas: fix undefined bit shift

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Message-ID: <50A69693.2050002@gmail.com>
Date:	Fri, 16 Nov 2012 14:40:03 -0500
From:	Xi Wang <xi.wang@...il.com>
To:	Xiangliang Yu <yuxiangl@...vell.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>
CC:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH v2] [SCSI] mvsas: fix undefined bit shift

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>
Cc: Xiangliang Yu <yuxiangl@...vell.com>
Cc: James Bottomley <JBottomley@...allels.com>
Cc: stable@...r.kernel.org
---
As suggested by James, v2 is a single patch with a stable tag.
---
 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;		\
-- 
1.7.10.4

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