Re: [PATCH v2 1/1] MdePkg/BaseRngLib: Add a smoketest for RDRAND and check CPUID

["Jason A. Donenfeld" <Jason@zx2c4.com>]

On Tue, Nov 22, 2022 at 4:56 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
>
> On Tue, Nov 22, 2022 at 3:39 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>>
>> On Tue, Nov 22, 2022 at 4:32 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
>> > +  // Testing algorithm inspired by linux's arch/x86/kernel/cpu/rdrand.c:x86_init_rdrand
>> > +  // as relicensed by the author, Jason Donenfeld, in the EDK2 mailing list.
>> > +  // As is, the algorithm samples rdrand $RDRAND_TEST_SAMPLES times and expects
>> > +  // a different result $RDRAND_MIN_CHANGE times for reliable RDRAND usage.
>>
>> You don't need to pepper my name all over the source. :)
>
>
> I just wanted to properly credit you :) If you're not okay with it I can remove it in a v3.

Yes, please remove.

 >> > +  for (TestIteration = 0; TestIteration < RDRAND_TEST_SAMPLES;
TestIteration++) {
>> > +    UINT32  Sample;
>> > +    //
>> > +    // Note: We use a retry loop for rdrand. Normal users get this in BaseRng.c
>> > +    // Any failure to get a random number will assume RDRAND does not work.
>> > +    //
>> > +    for (Idx = 0; Idx < RDRAND_RETRIES; Idx++) {
>> > +      if (AsmRdRand32 (&Sample)) {
>>
>> The linux code will use a 64bit value on 64bit machines. I suggest you
>> do the same here -- use native word size. I think EFI calls this a
>> "UINTN".
>
>
> Hmm, do you reckon it makes a difference?

Yes, it does. Please account for this. Use an ifdef or something if
you need. It's not very hard.

Jason