[PATCH] smcc: fix sign bit expansion

[Jens Wiklander]

On Tue, Jan 05, 2021 at 08:03:11PM +0000, Volodymyr Babchuk wrote:
> Signed ARM_SMCCC_FAST_CALL value is shifted to 31'st bit. Then, it is expanded
> to 64 bit value, which results in 1s in higher 32 bits.
> 
> This causes corrupted values in 64-bit SMC IDs and issues in buggy handlers of
> 32-bit calls.
> 
> We need to make ARM_SMCCC_FAST_CALL unsigned long, so it would work properly
> on 32 bit architectures.
> 
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk at epam.com>
> ---
>  include/linux/arm-smccc.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Jens Wiklander <jens.wiklander at linaro.org>

You may want to make the prefix "smccc:" (note the extra c) instead.

Cheers,
Jens

> 
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 2d1e6cc156..7f2be23394 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -11,8 +11,8 @@
>   * http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html
>   */
>  
> -#define ARM_SMCCC_STD_CALL		0
> -#define ARM_SMCCC_FAST_CALL		1
> +#define ARM_SMCCC_STD_CALL		0UL
> +#define ARM_SMCCC_FAST_CALL		1UL
>  #define ARM_SMCCC_TYPE_SHIFT		31
>  
>  #define ARM_SMCCC_SMC_32		0
> -- 
> 2.29.2