linux-kernel - [34-longterm 097/209] ARM: 6482/2: Fix find_next_zero

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Date:	Thu, 14 Apr 2011 13:42:07 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, James Jones <jajones@...dia.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 097/209] ARM: 6482/2: Fix find_next_zero_bit and related assembly

From: James Jones <jajones@...dia.com>

  =====================================================================
  | This is a commit scheduled for the next v2.6.34 longterm release. |
  | If you see a problem with using this for longterm, please comment.|
  =====================================================================

commit 0e91ec0c06d2cd15071a6021c94840a50e6671aa upstream.

The find_next_bit, find_first_bit, find_next_zero_bit
and find_first_zero_bit functions were not properly
clamping to the maxbit argument at the bit level. They
were instead only checking maxbit at the byte level.
To fix this, add a compare and a conditional move
instruction to the end of the common bit-within-the-
byte code used by all the functions and be sure not to
clobber the maxbit argument before it is used.

Reviewed-by: Nicolas Pitre <nicolas.pitre@...aro.org>
Tested-by: Stephen Warren <swarren@...dia.com>
Signed-off-by: James Jones <jajones@...dia.com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 arch/arm/lib/findbit.S |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S
index 1e4cbd4..64f6bc1 100644
--- a/arch/arm/lib/findbit.S
+++ b/arch/arm/lib/findbit.S
@@ -174,8 +174,8 @@ ENDPROC(_find_next_bit_be)
  */
 .L_found:
 #if __LINUX_ARM_ARCH__ >= 5
-		rsb	r1, r3, #0
-		and	r3, r3, r1
+		rsb	r0, r3, #0
+		and	r3, r3, r0
 		clz	r3, r3
 		rsb	r3, r3, #31
 		add	r0, r2, r3
@@ -190,5 +190,7 @@ ENDPROC(_find_next_bit_be)
 		addeq	r2, r2, #1
 		mov	r0, r2
 #endif
+		cmp	r1, r0			@ Clamp to maxbit
+		movlo	r0, r1
 		mov	pc, lr

-- 
1.7.4.4

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