From ff7ddc02b273f9159ef46fdb67d99062f8e598d9 Mon Sep 17 00:00:00 2001
From: Pierre Gondois <pierre.gondois@arm.com>
Date: Fri, 11 Aug 2023 16:33:10 +0200
Subject: SecurityPkg/RngDxe: Simplify Rng algorithm selection for Arm

The first element of mAvailableAlgoArray is defined as the default
Rng algorithm to use. Don't go through the array at each RngGetRNG()
call and just return the first element of the array.

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>
---
 SecurityPkg/RandomNumberGenerator/RngDxe/ArmRngDxe.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

(limited to 'SecurityPkg')

diff --git a/SecurityPkg/RandomNumberGenerator/RngDxe/ArmRngDxe.c b/SecurityPkg/RandomNumberGenerator/RngDxe/ArmRngDxe.c
index 78a18c5..7a42e3c 100644
--- a/SecurityPkg/RandomNumberGenerator/RngDxe/ArmRngDxe.c
+++ b/SecurityPkg/RandomNumberGenerator/RngDxe/ArmRngDxe.c
@@ -77,7 +77,6 @@ RngGetRNG (
   )
 {
   EFI_STATUS  Status;
-  UINTN       Index;
   GUID        RngGuid;
 
   if ((This == NULL) || (RNGValueLength == 0) || (RNGValue == NULL)) {
@@ -88,21 +87,13 @@ RngGetRNG (
     //
     // Use the default RNG algorithm if RNGAlgorithm is NULL.
     //
-    for (Index = 0; Index < mAvailableAlgoArrayCount; Index++) {
-      if (!IsZeroGuid (&mAvailableAlgoArray[Index])) {
-        RNGAlgorithm = &mAvailableAlgoArray[Index];
-        goto FoundAlgo;
-      }
-    }
-
-    if (Index == mAvailableAlgoArrayCount) {
-      // No algorithm available.
-      ASSERT (Index != mAvailableAlgoArrayCount);
-      return EFI_DEVICE_ERROR;
+    if (mAvailableAlgoArrayCount != 0) {
+      RNGAlgorithm = &mAvailableAlgoArray[0];
+    } else {
+      return EFI_UNSUPPORTED;
     }
   }
 
-FoundAlgo:
   Status = GetRngGuid (&RngGuid);
   if (!EFI_ERROR (Status) &&
       CompareGuid (RNGAlgorithm, &RngGuid))
-- 
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