Re: [Qemu-devel] [PATCH v5 1/4] target/arm: implement SHA-512 instructions

[Ard Biesheuvel]

On 6 February 2018 at 18:45, Peter Maydell <address@hidden> wrote:
> On 22 January 2018 at 17:26, Ard Biesheuvel <address@hidden> wrote:
>> This implements emulation of the new SHA-512 instructions that have
>> been added as an optional extensions to the ARMv8 Crypto Extensions
>> in ARM v8.2.
>>
>> Signed-off-by: Ard Biesheuvel <address@hidden>
>
>
>> +void HELPER(crypto_sha512h)(void *vd, void *vn, void *vm)
>> +{
>> +    uint64_t *rd = vd;
>> +    uint64_t *rn = vn;
>> +    uint64_t *rm = vm;
>> +
>> +    rd[1] += S1_512(rm[1]) + cho512(rm[1], rn[0], rn[1]);
>> +    rd[0] += S1_512(rd[1] + rm[0]) + cho512(rd[1] + rm[0], rm[1], rn[0]);
>
> This gives the wrong answer if the destination register
> happens to be the same as one of the inputs, because the
> assignment to rd[1] will overwrite the input before the
> calculation of rd[0] uses it.
>

It is supposed to use the new value of rd[1], so this is expected.

> Some extra temporaries should fix this. I'll try fixing
> that up locally and see if it passes tests then.
>
> thanks
> -- PMM