Re: [PATCH v2] target/riscv: Use accelerated helper for AES64KS1I

[Alistair Francis <alistair23@gmail.com>]

On Fri, Sep 1, 2023 at 3:12 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> Use the accelerated SubBytes/ShiftRows/AddRoundKey AES helper to
> implement the first half of the key schedule derivation. This does not
> actually involve shifting rows, so clone the same value into all four
> columns of the AES vector to counter that operation.
>
> Cc: Richard Henderson <richard.henderson@linaro.org>
> Cc: Philippe Mathieu-Daudé <philmd@linaro.org>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Alistair Francis <alistair.francis@wdc.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
> v2: assign round constant to elements 0 and 1 only
>
>  target/riscv/crypto_helper.c | 17 +++++------------
>  1 file changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/target/riscv/crypto_helper.c b/target/riscv/crypto_helper.c
> index 4d65945429c6dcc4..bb084e00efe52d1b 100644
> --- a/target/riscv/crypto_helper.c
> +++ b/target/riscv/crypto_helper.c
> @@ -148,24 +148,17 @@ target_ulong HELPER(aes64ks1i)(target_ulong rs1, target_ulong rnum)
>
>      uint8_t enc_rnum = rnum;
>      uint32_t temp = (RS1 >> 32) & 0xFFFFFFFF;
> -    uint8_t rcon_ = 0;
> -    target_ulong result;
> +    AESState t, rc = {};
>
>      if (enc_rnum != 0xA) {
>          temp = ror32(temp, 8); /* Rotate right by 8 */
> -        rcon_ = round_consts[enc_rnum];
> +        rc.w[0] = rc.w[1] = round_consts[enc_rnum];
>      }
>
> -    temp = ((uint32_t)AES_sbox[(temp >> 24) & 0xFF] << 24) |
> -           ((uint32_t)AES_sbox[(temp >> 16) & 0xFF] << 16) |
> -           ((uint32_t)AES_sbox[(temp >> 8) & 0xFF] << 8) |
> -           ((uint32_t)AES_sbox[(temp >> 0) & 0xFF] << 0);
> +    t.w[0] = t.w[1] = t.w[2] = t.w[3] = temp;
> +    aesenc_SB_SR_AK(&t, &t, &rc, false);
>
> -    temp ^= rcon_;
> -
> -    result = ((uint64_t)temp << 32) | temp;
> -
> -    return result;
> +    return t.d[0];
>  }
>
>  target_ulong HELPER(aes64im)(target_ulong rs1)
> --
> 2.39.2
>
>