On 19 June 2018 at 00:33, Eric Biggers <ebiggers@xxxxxxxxxx> 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@xxxxxxxx>
> Fixes: ede9622162fa ("crypto: arm/speck - add NEON-accelerated implementation of Speck-XTS")
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> 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
>
> .if \n == 64
> // Load first tweak
Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
