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SubjectRe: [PATCH] ARM: Fix find_next_zero_bit and related assembly
Date
On Tuesday 23 November 2010 13:26:47 Nicolas Pitre wrote:
> On Thu, 11 Nov 2010, James Jones wrote:
> > 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.
> >
> > Signed-off-by: James Jones <jajones@nvidia.com>
> > Tested-by: Stephen Warren <swarren@nvidia.com>
>
> Reviewed-by: Nicolas Pitre <nicolas.pitre@linaro.org>
>
> Please send to RMK's patch system.

Thanks for the review. It's already in the patch system, but I updated the
entry to include your reviewed-by line.

-James

> > ---
> >
> > 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


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