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

The 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 TRNG library.

Signed-off-by: Sami Mujawar <sami.mujawar@...>
---

Notes:
v2:
- MdePkg\Include\Library\TrngLib.h is base type [LIMING]
library. It can use RETURN_STATUS instead of
EFI_STATUS.
- Replaced EFI_STATUS with RETURN_STATUS. [SAMI]
- MdePkg\Include\Library\TrngLib.h API parameter [LIMING]
doesn't require CONST. CONST means the value
specified by the input pointer will not be
changed in API implementation.
- Removed the use of constant pointers in the [SAMI]
TRNG API.

MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.c | 111 ++++++++++++++++++++
MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.inf | 30 ++++++
MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.uni | 12 +++
MdePkg/MdePkg.dsc | 1 +
4 files changed, 154 insertions(+)

diff --git a/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.c b/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.c
new file mode 100644
index 0000000000000000000000000000000000000000..406a1e8587ccfb0cd903bf7a3794f16627eb0a84
--- /dev/null
+++ b/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.c
@@ -0,0 +1,111 @@
+/** @file
+ Null version of TRNG (True Random Number Generator) services.
+
+ Copyright (c) 2021, Arm Limited. All rights reserved.<BR>
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+
+ @par Glossary:
+ - TRNG - True Random Number Generator
+**/
+
+#include <Library/DebugLib.h>
+#include <Library/TrngLib.h>
+
+/** Get the TRNG version.
+
+ A TRNG may be implemented by the system firmware, in which case this
+ function shall return the version information for the TRNG implementation.
+ Returning version information is optional and if not implemented,
+ RETURN_UNSUPPORTED shall be returned.
+
+ @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 Function not implemented.
+**/
+RETURN_STATUS
+EFIAPI
+GetTrngVersion (
+ OUT UINT16 *MajorRevision,
+ OUT UINT16 *MinorRevision
+ )
+{
+ ASSERT (FALSE);
+ return RETURN_UNSUPPORTED;
+}
+
+/** Get the UUID of the TRNG backend.
+
+ A TRNG may be implemented by the system firmware, in which case this
+ function shall return the UUID for the TRNG implementation.
+ Returning the TRNG UUID is optional and if not implemented, RETURN_UNSUPPORTED
+ shall be returned.
+
+ @param [out] Guid UUID of the TRNG backend.
+
+ @retval RETURN_SUCCESS The function completed successfully.
+ @retval RETURN_INVALID_PARAMETER Invalid parameter.
+ @retval RETURN_UNSUPPORTED Function not implemented.
+**/
+RETURN_STATUS
+EFIAPI
+GetTrngUuid (
+ 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 GetEntropy().
+**/
+UINTN
+EFIAPI
+GetTrngMaxSupportedEntropyBits (
+ VOID
+ )
+{
+ ASSERT (FALSE);
+ return 0;
+}
+
+/** Returns N bits of conditioned entropy.
+
+ See [3] 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.
+ Note: In this implementation this function returns a status code instead
+ of a boolean value.
+
+ @param [in] EntropyBits Number of entropy bits requested.
+ @param [out] Buffer Buffer to return the entropy bits.
+ @param [in] BufferSize Size of the Buffer in bytes.
+
+ @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
+GetEntropy (
+ IN CONST UINTN EntropyBits,
+ OUT UINT8 *Buffer,
+ IN CONST UINTN BufferSize
+ )
+{
+ ASSERT (FALSE);
+ return RETURN_UNSUPPORTED;
+}
diff --git a/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.inf b/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.inf
new file mode 100644
index 0000000000000000000000000000000000000000..a700cf66f457f8898d5c51a7b9c0b3d7643ff7f9
--- /dev/null
+++ b/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.inf
@@ -0,0 +1,30 @@
+## @file
+# Null instance of TRNG (True Random Number Generator) Library.
+#
+# Copyright (c) 2021, Arm Limited. All rights reserved.<BR>
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+ INF_VERSION = 0x0001001B
+ BASE_NAME = BaseTrngLibNull
+ MODULE_UNI_FILE = BaseTrngLibNull.uni
+ FILE_GUID = ABDE1C87-4F50-4B82-9133-7A79E13F69AB
+ MODULE_TYPE = BASE
+ VERSION_STRING = 1.0
+ LIBRARY_CLASS = TrngLib
+
+#
+# VALID_ARCHITECTURES = IA32 X64 ARM AARCH64
+#
+
+[Sources]
+ BaseTrngLibNull.c
+
+[Packages]
+ MdePkg/MdePkg.dec
+
+[LibraryClasses]
+ DebugLib
diff --git a/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.uni b/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.uni
new file mode 100644
index 0000000000000000000000000000000000000000..1ec7def522e5975e9621eb280776251b1e5502ca
--- /dev/null
+++ b/MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.uni
@@ -0,0 +1,12 @@
+// /** @file
+// Null Instance of TRNG (True Random Number Generator) Library.
+//
+// Copyright (c) 2021, 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 TrngLib class, but never actually call TrngLib APIs for consuming Entropy."
diff --git a/MdePkg/MdePkg.dsc b/MdePkg/MdePkg.dsc
index a94959169b2fd9d4b5bf7ad903bf5ce06566c60e..f83753e132e9b9eb4152927fc182701fb1e70ca4 100644
--- a/MdePkg/MdePkg.dsc
+++ b/MdePkg/MdePkg.dsc
@@ -67,6 +67,7 @@ [Components]
MdePkg/Library/DxeRngLib/DxeRngLib.inf
MdePkg/Library/BaseRngLibNull/BaseRngLibNull.inf
MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf
+ MdePkg/Library/BaseTrngLibNull/BaseTrngLibNull.inf

MdePkg/Library/BaseSerialPortLibNull/BaseSerialPortLibNull.inf
MdePkg/Library/BaseSynchronizationLib/BaseSynchronizationLib.inf
--
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'