[PATCH] crypto: arm/speck - fix building in Thumb2 mode

[stefan@agner.ch (Stefan Agner)]

On 19.06.2018 00:33, Eric Biggers wrote:
> Building the kernel with CONFIG_THUMB2_KERNEL=y and
> CONFIG_CRYPTO_SPECK_NEON set fails with the following errors:
> 
>     arch/arm/crypto/speck-neon-core.S: Assembler messages:
> 
>     arch/arm/crypto/speck-neon-core.S:419: Error: r13 not allowed here
> -- `bic sp,#0xf'
>     arch/arm/crypto/speck-neon-core.S:423: Error: r13 not allowed here
> -- `bic sp,#0xf'
>     arch/arm/crypto/speck-neon-core.S:427: Error: r13 not allowed here
> -- `bic sp,#0xf'
>     arch/arm/crypto/speck-neon-core.S:431: Error: r13 not allowed here
> -- `bic sp,#0xf'
> 
> The problem is that the 'bic' instruction can't operate on the 'sp'
> register in Thumb2 mode.  Fix it by using a temporary register.  This
> isn't in the main loop, so the performance difference is negligible.
> This also matches what aes-neonbs-core.S does.
> 
> Reported-by: Stefan Agner <stefan@agner.ch>
> Fixes: ede9622162fa ("crypto: arm/speck - add NEON-accelerated
> implementation of Speck-XTS")
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  arch/arm/crypto/speck-neon-core.S | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/crypto/speck-neon-core.S
> b/arch/arm/crypto/speck-neon-core.S
> index 3c1e203e53b9..57caa742016e 100644
> --- a/arch/arm/crypto/speck-neon-core.S
> +++ b/arch/arm/crypto/speck-neon-core.S
> @@ -272,9 +272,11 @@
>  	 * Allocate stack space to store 128 bytes worth of tweaks.  For
>  	 * performance, this space is aligned to a 16-byte boundary so that we
>  	 * can use the load/store instructions that declare 16-byte alignment.
> +	 * For Thumb2 compatibility, don't do the 'bic' directly on 'sp'.
>  	 */
> -	sub		sp, #128
> -	bic		sp, #0xf
> +	sub		r12, sp, #128
> +	bic		r12, #0xf
> +	mov		sp, r12

Looks good to me and compiles fine here. Thanks!

Reviewed-by: Stefan Agner <stefan@agner.ch>

--
Stefan

>  
>  .if \n == 64
>  	// Load first tweak