BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4151
The EFI_RNG_PROTOCOL can rely on the RngLib. The RngLib has multiple
implementations, some of them are unsafe (e.g. BaseRngLibTimerLib).
To allow the RngDxe to detect when such implementation is used,
a GetRngGuid() function was added in a previous patch.
The EFI_RNG_PROTOCOL can advertise multiple algorithms through
Guids. The PcdCpuRngSupportedAlgorithm is currently used to
advertise the RngLib in the Arm implementation.
The issues of doing that are:
- the RngLib implementation might not use CPU instructions,
cf. the BaseRngLibTimerLib
- most platforms don't set PcdCpuRngSupportedAlgorithm
A GetRngGuid() was added to the RngLib in a previous patch,
allowing to identify the algorithm implemented by the RngLib.
Make use of this function and place the unsage algorithm
at the last position in the mAvailableAlgoArray.
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Tested-by: Kun Qin <kun.qin@microsoft.com>
19438cff97