[SLOF] [PATCH v3 2/7] tcgbios: Use assembly for 32 bit rotr in sha256

[Alexey Kardashevskiy]

On 09/07/2021 12:53, Stefan Berger wrote:
> From: Stefan Berger <stefanb at linux.ibm.com>
> 
> Use assembly for the 32 bit rotr in the sha256 implementation.

Why bother with asm here?


> 
> Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
> ---
>   lib/libtpm/sha256.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/libtpm/sha256.c b/lib/libtpm/sha256.c
> index fb67e19..292e54e 100644
> --- a/lib/libtpm/sha256.c
> +++ b/lib/libtpm/sha256.c
> @@ -22,10 +22,16 @@ typedef struct _sha256_ctx {
>   	uint32_t h[8];
>   } sha256_ctx;
>   
> -static inline uint32_t rotr(uint32_t x, uint8_t n)
> -{
> -	return (x >> n) | (x << (32 - n));
> -}
> +#define rotr(VAL, N)				\
> +({						\
> +	uint32_t res;				\
> +	__asm__ (				\
> +		"rotrwi %0, %1, %2\n\t"		\
> +		: "=r" (res)			\
> +		: "r" (VAL), "i" (N)		\
> +	);					\
> +	res; 					\
> +})
>   
>   static inline uint32_t Ch(uint32_t x, uint32_t y, uint32_t z)
>   {
> 

-- 
Alexey