Re: [PATCH] ARM: Fix find_next_zero_bit and related assembly

From: Nicolas Pitre
Date: Tue Nov 23 2010 - 16:26:53 EST


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@xxxxxxxxxx>
> Tested-by: Stephen Warren <swarren@xxxxxxxxxx>

Reviewed-by: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>

Please send to RMK's patch system.



> ---
> 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
>
> --
> 1.7.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/