Re: [edk2-devel] CryptoPkg host test broken due to smoketest for RDRAND

["Ard Biesheuvel" <ardb@kernel.org>]

On Fri, 14 Jun 2024 at 18:45, Yao, Jiewen <jiewen.yao@intel.com> wrote:
>
>
> > -----Original Message-----
> > From: Ard Biesheuvel <ardb@kernel.org>
> > Sent: Saturday, June 15, 2024 12:14 AM
> > To: Yao, Jiewen <jiewen.yao@intel.com>
> > Cc: Li, Yi1 <yi1.li@intel.com>; Gerd Hoffmann <kraxel@redhat.com>;
> > devel@edk2.groups.io; Hou, Wenxing <wenxing.hou@intel.com>; Kinney, Michael
> > D <michael.d.kinney@intel.com>; Pedro Falcato <pedro.falcato@gmail.com>
> > Subject: Re: [edk2-devel] CryptoPkg host test broken due to smoketest for
> > RDRAND
> >
> > On Fri, 14 Jun 2024 at 18:09, Yao, Jiewen <jiewen.yao@intel.com> wrote:
> > >
> > > Hey
> > > This PR seems just a workaround.
> > >
> > > I don't feel it is right solution to hardcode BIT30.
> > > What if the host platform does not have such capability? You will get failure
> > later.
> > >
> >
> > Agreed. But that was already the case: RngLib assumed that RDRAND was
> > implemented without checking CPUID at all, and so the code was already
> > broken on systems without RDRAND.
>
> [Jiewen] Sorry, I don’t understand your comment. " implemented without checking CPUID at all "
>
> See below code. It does use CPUID to check the capability.
>
> EFI_STATUS
> EFIAPI
> BaseRngLibConstructor (
>   VOID
>   )
> {
>   UINT32  RegEcx;
>
>   //
>   // Determine RDRAND support by examining bit 30 of the ECX register returned by
>   // CPUID. A value of 1 indicates that processor support RDRAND instruction.
>   //
>   AsmCpuid (1, 0, 0, &RegEcx, 0);
>
>   mRdRandSupported = ((RegEcx & RDRAND_MASK) == RDRAND_MASK);
>
>   if (mRdRandSupported) {
>     mRdRandSupported = TestRdRand ();
>   }
>
>   return EFI_SUCCESS;
> }
>
>

See commit 9301e5644cef5a5234f71b178373dd508cabb9ee

The old code had

+BOOLEAN
+EFIAPI
+ArchIsRngSupported (
+  VOID
+  )
+{
+  /*
+     Existing software depends on this always returning TRUE, so for
+     now hard-code it.
+
+     return mRdRandSupported;
+  */
+  return TRUE;
+}



> >
> > >
> > > To fix this function, can we call real CPUID instruction to return real value?
> > >
> >
> > That would be better. But this change just restores the old behavior.
> > And on top of that, Yi Li already merged it.
>
> [Jiewen] I don’t think it is right to merge it without thorough review.
>
> I think we need follow 24 hour rule.
> Any patch requires at least 24 hours before merge, to give people chance to review and feedback.
>

Agreed.


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