[PATCH v1 0/2] Fixing RngDxe error for ARM/AARCH64

["Kun Qin" <kuqin12@gmail.com>]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4491

On an ARM system that does not support firmware TRNG, the current logic
from RngDxe will cause the system to assert at the below line:
`ASSERT (Index != mAvailableAlgoArrayCount);`

The reason seems to be:
1. When initializing the number of `mAvailableAlgoArrayCount`, the logic
will only treat the zero guid of "PcdCpuRngSupportedAlgorithm" as a
warning and still increment the counter because "RngGetBytes" might still
succeed:
https://github.com/tianocore/edk2/blob/1a39bdf2c53858ebb39e6de1362203c65c163c63/SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c#L51C3-L51C3.
2. This will cause the main entry to publish the RNG protocol and accept
further usage.
3. However, during usage, the zero guid is always filtered out: 
https://github.com/tianocore/edk2/blob/1a39bdf2c53858ebb39e6de1362203c65c163c63/SecurityPkg/RandomNumberGenerator/RngDxe/ArmRngDxe.c#L91.
Thus, this will cause the system to always not able to find the algorithm
and fail the boot with an assert.

The suggestion is to at least make the logic of initializing
"mAvailableAlgoArrayCount" consistent and filtering algorithm consistent.

In addition, the usage of `mAvailableAlgoArray` will always trigger a
data abortion error, which is caused by buffer allocated is
`RNG_AVAILABLE_ALGO_MAX` number of bytes, which should be
`RNG_AVAILABLE_ALGO_MAX` nubmer of EFI_RNG_ALGORITHM.

This patch fixed the 2 issues above. The change is verified on QEMU
virtual platform and proprietary physical platform.

Patch v1 branch: https://github.com/kuqin12/edk2/tree/fix_rng_edk2_v1

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Sami Mujawar <Sami.Mujawar@arm.com>
Cc: Pierre Gondois <pierre.gondois@arm.com>

Kun Qin (2):
  SecurityPkg: RngDxe: Unify handling of zero guid
  SecurityPkg: RngDxe: Fixing mAvailableAlgoArray allocator

 SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c | 9 +++++----
 SecurityPkg/RandomNumberGenerator/RngDxe/Arm/ArmAlgo.c         | 2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)

-- 
2.41.0.windows.1