MdePkg/ArmTrngLib: Add NULL instance of Arm TRNG Library

Bugzilla: 3668 (https://bugzilla.tianocore.org/show_bug.cgi?id=3668)

The Arm True Random Number Generator (TRNG) library defines an
interface to access the entropy source on a platform. On platforms
that do not have access to an entropy source, a NULL instance of
the TRNG library may be useful to satisfy the build dependency.

Therefore, add a NULL instance of the Arm TRNG library.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.c

@@ -0,0 +1,121 @@
+/** @file
+  Null version of the Arm TRNG (True Random Number Generator) services
+  (Cf [1]).
+
+  Copyright (c) 2021 - 2022, Arm Limited. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+  @par Reference(s):
+  - [1] Arm True Random Number Generator Firmware, Interface 1.0,
+        Platform Design Document.
+        (https://developer.arm.com/documentation/den0098/latest/)
+  - [2] NIST Special Publication 800-90B, Recommendation for the Entropy
+        Sources Used for Random Bit Generation.
+        (https://csrc.nist.gov/publications/detail/sp/800-90b/final)
+
+  @par Glossary:
+    - TRNG - True Random Number Generator
+**/
+
+#include <Library/DebugLib.h>
+#include <Library/ArmTrngLib.h>
+
+/** Get the version of the Arm TRNG backend.
+
+  A TRNG may be implemented by the system firmware, in which case this
+  function shall return the version of the Arm TRNG backend.
+  The implementation must return NOT_SUPPORTED if a Back end is not present.
+
+  @param [out]  MajorRevision     Major revision.
+  @param [out]  MinorRevision     Minor revision.
+
+  @retval  RETURN_SUCCESS            The function completed successfully.
+  @retval  RETURN_INVALID_PARAMETER  Invalid parameter.
+  @retval  RETURN_UNSUPPORTED        Backend not present.
+**/
+RETURN_STATUS
+EFIAPI
+GetArmTrngVersion (
+  OUT UINT16  *MajorRevision,
+  OUT UINT16  *MinorRevision
+  )
+{
+  ASSERT (FALSE);
+  return RETURN_UNSUPPORTED;
+}
+
+/** Get the UUID of the Arm TRNG backend.
+
+  A TRNG may be implemented by the system firmware, in which case this
+  function shall return the UUID of the TRNG backend.
+  Returning the Arm TRNG UUID is optional and if not implemented,
+  RETURN_UNSUPPORTED shall be returned.
+
+  Note: The caller must not rely on the returned UUID as a trustworthy Arm TRNG
+        Back end identity
+
+  @param [out]  Guid              UUID of the Arm TRNG backend.
+
+  @retval  RETURN_SUCCESS            The function completed successfully.
+  @retval  RETURN_INVALID_PARAMETER  Invalid parameter.
+  @retval  RETURN_UNSUPPORTED        Function not implemented.
+**/
+RETURN_STATUS
+EFIAPI
+GetArmTrngUuid (
+  OUT GUID  *Guid
+  )
+{
+  ASSERT (FALSE);
+  return RETURN_UNSUPPORTED;
+}
+
+/** Returns maximum number of entropy bits that can be returned in a single
+    call.
+
+  @return Returns the maximum number of Entropy bits that can be returned
+          in a single call to GetArmTrngEntropy().
+**/
+UINTN
+EFIAPI
+GetArmTrngMaxSupportedEntropyBits (
+  VOID
+  )
+{
+  ASSERT (FALSE);
+  return 0;
+}
+
+/** Returns N bits of conditioned entropy.
+
+  See [2] Section 2.3.1 GetEntropy: An Interface to the Entropy Source
+    GetEntropy
+      Input:
+        bits_of_entropy: the requested amount of entropy
+      Output:
+        entropy_bitstring: The string that provides the requested entropy.
+      status: A Boolean value that is TRUE if the request has been satisfied,
+              and is FALSE otherwise.
+
+  @param  [in]   EntropyBits  Number of entropy bits requested.
+  @param  [in]   BufferSize   Size of the Buffer in bytes.
+  @param  [out]  Buffer       Buffer to return the entropy bits.
+
+  @retval  RETURN_SUCCESS            The function completed successfully.
+  @retval  RETURN_INVALID_PARAMETER  Invalid parameter.
+  @retval  RETURN_UNSUPPORTED        Function not implemented.
+  @retval  RETURN_BAD_BUFFER_SIZE    Buffer size is too small.
+  @retval  RETURN_NOT_READY          No Entropy available.
+**/
+RETURN_STATUS
+EFIAPI
+GetArmTrngEntropy (
+  IN  UINTN  EntropyBits,
+  IN  UINTN  BufferSize,
+  OUT UINT8  *Buffer
+  )
+{
+  ASSERT (FALSE);
+  return RETURN_UNSUPPORTED;
+}

MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.inf

@@ -0,0 +1,30 @@
+## @file
+#  Null instance of the Arm TRNG (True Random Number Generator) Library.
+#
+#  Copyright (c) 2021 - 2022, Arm Limited. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.29
+  BASE_NAME                      = BaseArmTrngLibNull
+  MODULE_UNI_FILE                = BaseArmTrngLibNull.uni
+  FILE_GUID                      = ABDE1C87-4F50-4B82-9133-7A79E13F69AB
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = ArmTrngLib
+
+#
+#  VALID_ARCHITECTURES           = IA32 X64 ARM AARCH64 RISCV64
+#
+
+[Sources]
+  BaseArmTrngLibNull.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  DebugLib

MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.uni

@@ -0,0 +1,12 @@
+// /** @file
+// Null Instance of the Arm TRNG (True Random Number Generator) Library.
+//
+//  Copyright (c) 2021 - 2022, Arm Limited. All rights reserved.<BR>
+//
+// SPDX-License-Identifier: BSD-2-Clause-Patent
+//
+// **/
+
+#string STR_MODULE_ABSTRACT             #language en-US "Null instance of TRNG Library"
+
+#string STR_MODULE_DESCRIPTION          #language en-US "This library instance should be used with modules that inherit an (indirect) dependency on the ArmTrngLib class, but never actually call ArmTrngLib APIs for consuming Entropy."

MdePkg/MdeLibs.dsc.inc

@@ -12,6 +12,7 @@
 ##
 
 [LibraryClasses]
+  ArmTrngLib|MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.inf
   RegisterFilterLib|MdePkg/Library/RegisterFilterLibNull/RegisterFilterLibNull.inf
   CpuLib|MdePkg/Library/BaseCpuLib/BaseCpuLib.inf
   SmmCpuRendezvousLib|MdePkg/Library/SmmCpuRendezvousLibNull/SmmCpuRendezvousLibNull.inf

MdePkg/MdePkg.dsc

@@ -57,6 +57,7 @@
   MdePkg/Library/PciSegmentLibSegmentInfo/BasePciSegmentLibSegmentInfo.inf
   MdePkg/Library/PciSegmentLibSegmentInfo/DxeRuntimePciSegmentLibSegmentInfo.inf
   MdePkg/Library/BaseS3PciSegmentLib/BaseS3PciSegmentLib.inf
+  MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.inf
   MdePkg/Library/BasePeCoffGetEntryPointLib/BasePeCoffGetEntryPointLib.inf
   MdePkg/Library/BasePeCoffLib/BasePeCoffLib.inf
   MdePkg/Library/BasePeCoffExtraActionLibNull/BasePeCoffExtraActionLibNull.inf