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From: "PierreGondois" <pierre.gondois@arm.com>
To: devel@edk2.groups.io
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>,
	Leif Lindholm <leif@nuviainc.com>,
	Sami Mujawar <sami.mujawar@arm.com>,
	Jiewen Yao <jiewen.yao@intel.com>,
	Jian J Wang <jian.j.wang@intel.com>
Subject: [PATCH v3 3/4] SecurityPkg/RngDxe: Conditionally install EFI_RNG_PROTOCOL
Date: Thu, 24 Nov 2022 17:17:55 +0100
Message-Id: <20221124161756.216996-4-Pierre.Gondois@arm.com>
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In-Reply-To: <20221124161756.216996-1-Pierre.Gondois@arm.com>
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From: Pierre Gondois <pierre.gondois@arm.com>

On Arm platforms, the number of available RNG algorithms is
dynamically detected and can be 0 in the absence of FEAT_RNG
and firmware TRNG.
In this case, the EFI_RNG_PROTOCOL should not be installed to
prevent from installing an empty protocol.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
---
 .../RandomNumberGenerator/RngDxe/RngDxe.c     | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/SecurityPkg/RandomNumberGenerator/RngDxe/RngDxe.c b/Security=
Pkg/RandomNumberGenerator/RngDxe/RngDxe.c
index 421abb52b8bf..d30cb7f47696 100644
--- a/SecurityPkg/RandomNumberGenerator/RngDxe/RngDxe.c
+++ b/SecurityPkg/RandomNumberGenerator/RngDxe/RngDxe.c
@@ -63,6 +63,18 @@ RngDriverEntry (
   EFI_STATUS  Status;
   EFI_HANDLE  Handle;
=20
+  //
+  // Get the list of available algorithm.
+  //
+  Status =3D GetAvailableAlgorithms ();
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  if (mAvailableAlgoArrayCount =3D=3D 0) {
+    return EFI_UNSUPPORTED;
+  }
+
   //
   // Install UEFI RNG (Random Number Generator) Protocol
   //
@@ -74,13 +86,10 @@ RngDriverEntry (
                   NULL
                   );
   if (EFI_ERROR (Status)) {
-    return Status;
+    FreeAvailableAlgorithms ();
   }
=20
-  //
-  // Get the list of available algorithm.
-  //
-  return GetAvailableAlgorithms ();
+  return Status;
 }
=20
 /**
--=20
2.25.1