[PATCH v1 1/2] SecurityPkg: RngDxe: Unify handling of zero guid

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

From: Kun Qin <kuqin@microsoft.com>

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

The existing logic of initializing `mAvailableAlgoArrayCount` will treat
the zero GUID in `PcdCpuRngSupportedAlgorithm` as a legit case and
increment `mAvailableAlgoArrayCount`, causing the RNG protocol be
published.

However, when the protocol is invoked, any zero GUID will be filtered
out, leaving a possible edge case where the protocol only has a zero GUID
based algorithm and being filtered out will always result in an ASSERT.

This change marked the zero GUID as an issue and will not increment the
counter and thus avoid publishing the protocol completely.

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>

Signed-off-by: Kun Qin <kuqin@microsoft.com>
---
 SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c b/SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c
index e8be217f8a8c..de279cdadeea 100644
--- a/SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c
+++ b/SecurityPkg/RandomNumberGenerator/RngDxe/AArch64/AArch64Algo.c
@@ -47,15 +47,16 @@ GetAvailableAlgorithms (
       );
     mAvailableAlgoArrayCount++;
 
-    DEBUG_CODE_BEGIN ();
     if (IsZeroGuid (PcdGetPtr (PcdCpuRngSupportedAlgorithm))) {
+      DEBUG_CODE_BEGIN ();
       DEBUG ((
         DEBUG_WARN,
         "PcdCpuRngSupportedAlgorithm should be a non-zero GUID\n"
         ));
+
+      DEBUG_CODE_END ();
+      mAvailableAlgoArrayCount--;
     }
-
-    DEBUG_CODE_END ();
   }
 
   // Raw algorithm (Trng)
-- 
2.41.0.windows.1