Re: [PATCH v3 0/4] ArmPkg/SecurityPkg: Fixes for ArmTrngLib/RngDxe

["PierreGondois" <pierre.gondois@arm.com>]

Hello Ard,

On 11/26/22 15:33, Ard Biesheuvel wrote:
> On Thu, 24 Nov 2022 at 17:18, <Pierre.Gondois@arm.com> wrote:
>>
>> From: Pierre Gondois <pierre.gondois@arm.com>
>>
>> v1:
>> - https://edk2.groups.io/g/devel/message/96356
>> v2:
>> - https://edk2.groups.io/g/devel/message/96434
>> - Reformulate commit message.
>> - Do not warn if no algorithm is found as the message
>>    would be printed on non-Arm platforms.
>> v3:
>> - Add the following patches:
>>    1. ArmPkg/ArmTrngLib: Remove ASSERTs in ArmTrngLibConstructor()
>>       Requested by Ard.
>>       Cf https://edk2.groups.io/g/devel/message/96495
>>    2. SecurityPkg/RngDxe: Conditionally install EFI_RNG_PROTOCOL
>>       Do not install EFI_RNG_PROTOCOL if no RNG algorithm is available.
>>       Cf. https://edk2.groups.io/g/devel/message/96494
>>    3. SecurityPkg/RngDxe: Fix Rng algo selection for Arm
>>       Coming from v2 patch being split.
>>
>> Some issues were found by Ard/Sami on the RngDxe/ArmTrngLib after
>> recent patches were merged. This patch serie intends to fix them.
>>
>> Pierre Gondois (4):
>>    ArmPkg/ArmTrngLib: Remove ASSERTs in ArmTrngLibConstructor()
> 
> Thanks for the fixed
> 
> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> 
> I pushed this one as #3663 (pending CI verification atm)
> 
>>    SecurityPkg/RngDxe: Correctly update mAvailableAlgoArrayCount
>>    SecurityPkg/RngDxe: Conditionally install EFI_RNG_PROTOCOL
>>    SecurityPkg/RngDxe: Fix Rng algo selection for Arm
>>
> 
> The remaining code still looks a bit clunky to me. Can't we just
> return an error from the library constructor of the library cannot
> initialize due to a missing prerequisite?

In RngDriverEntry(), GetAvailableAlgorithms() probe the available
RNG algorithms. If there are none, then we return an error code.
Otherwise we install EFI_RNG_PROTOCOL.

I assume the prerequisite you a referring to is 'checking there is
at least one available RNG algorithm that RngDxe can use', so if
ArmTrngLib's constructor fails, we should not prevent RngDxe to be
loaded (as the RngLib could be used for instance).

Does it answer your question, or did I understand it incorrectly ?

Regards,
Pierre

> 
> 
>>   ArmPkg/Library/ArmTrngLib/ArmTrngLib.c        |  5 -----
>>   .../RandomNumberGenerator/RngDxe/ArmRngDxe.c  | 18 +++++-------------
>>   .../RngDxe/Rand/RngDxe.c                      |  9 ++++++++-
>>   .../RandomNumberGenerator/RngDxe/RngDxe.c     | 19 ++++++++++++++-----
>>   4 files changed, 27 insertions(+), 24 deletions(-)
>>
>> --
>> 2.25.1
>>