ArmPkg/Library/ArmTrngLib/ArmTrngLib.c - edk2 - Git at Google

 /** @file
   Arm Firmware TRNG interface library.

   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
     - FID  - Function ID
 **/

 #include <Base.h>
 #include <Library/ArmLib.h>
 #include <Library/ArmMonitorLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>

 #include "ArmTrngDefs.h"

 /** Convert TRNG status codes to RETURN status codes.

   @param [in]  TrngStatus    TRNG status code.

   @retval  RETURN_SUCCESS            Success.
   @retval  RETURN_UNSUPPORTED        Function not implemented or
                                      negative return code.
   @retval  RETURN_INVALID_PARAMETER  A parameter is invalid.
   @retval  RETURN_NOT_READY          No Entropy available.
 **/
 STATIC
 RETURN_STATUS
 TrngStatusToReturnStatus (
   IN  INT32  TrngStatus
   )
 {
   switch (TrngStatus) {
     case TRNG_STATUS_NOT_SUPPORTED:
       return RETURN_UNSUPPORTED;

     case TRNG_STATUS_INVALID_PARAMETER:
       return RETURN_INVALID_PARAMETER;

     case TRNG_STATUS_NO_ENTROPY:
       return RETURN_NOT_READY;

     case TRNG_STATUS_SUCCESS:
       return RETURN_SUCCESS;

     default:
       if (TrngStatus < 0) {
         return RETURN_UNSUPPORTED;
       }

       return RETURN_SUCCESS;
   }
 }

 /** 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
   )
 {
   RETURN_STATUS     Status;
   ARM_MONITOR_ARGS  Parameters;
   INT32             Revision;

   if ((MajorRevision == NULL) || (MinorRevision == NULL)) {
     return RETURN_INVALID_PARAMETER;
   }

   ZeroMem (&Parameters, sizeof (Parameters));

   Parameters.Arg0 = ARM_SMC_ID_TRNG_VERSION;
   ArmMonitorCall (&Parameters);

   Revision = (INT32)Parameters.Arg0;
   Status   = TrngStatusToReturnStatus (Revision);
   if (RETURN_ERROR (Status)) {
     return Status;
   }

   *MinorRevision = (Revision & TRNG_REV_MINOR_MASK);
   *MajorRevision = ((Revision >> TRNG_REV_MAJOR_SHIFT) & TRNG_REV_MAJOR_MASK);
   return RETURN_SUCCESS;
 }

 /** Get the features supported by the Arm TRNG backend.

   The caller can determine if functions defined in the Arm TRNG ABI are
   present in the ABI implementation.

   @param [in]  FunctionId         Function Id.
   @param [out] Capability         Function specific capability if present.

   @retval  RETURN_SUCCESS            The function completed successfully.
   @retval  RETURN_INVALID_PARAMETER  Invalid parameter.
   @retval  RETURN_UNSUPPORTED        Function not implemented.
 **/
 STATIC
 RETURN_STATUS
 EFIAPI
 GetArmTrngFeatures (
   IN  CONST UINT32  FunctionId,
   OUT       UINT32  *Capability      OPTIONAL
   )
 {
   ARM_MONITOR_ARGS  Parameters;
   RETURN_STATUS     Status;

   ZeroMem (&Parameters, sizeof (Parameters));

   Parameters.Arg0 = ARM_SMC_ID_TRNG_FEATURES;
   Parameters.Arg1 = FunctionId;
   ArmMonitorCall (&Parameters);

   Status = TrngStatusToReturnStatus (Parameters.Arg0);
   if (RETURN_ERROR (Status)) {
     return Status;
   }

   if (Capability != NULL) {
     *Capability = (UINT32)Parameters.Arg0;
   }

   return RETURN_SUCCESS;
 }

 /** 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
   )
 {
   ARM_MONITOR_ARGS  Parameters;

   if (Guid == NULL) {
     return RETURN_INVALID_PARAMETER;
   }

   ZeroMem (&Parameters, sizeof (Parameters));

   Parameters.Arg0 = ARM_SMC_ID_TRNG_GET_UUID;
   ArmMonitorCall (&Parameters);

   // Only invalid value is TRNG_STATUS_NOT_SUPPORTED (-1).
   if ((INT32)Parameters.Arg0 == TRNG_STATUS_NOT_SUPPORTED) {
     return TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
   }

   Guid->Data1 = (Parameters.Arg0 & MAX_UINT32);
   Guid->Data2 = (Parameters.Arg1 & MAX_UINT16);
   Guid->Data3 = ((Parameters.Arg1 >> 16) & MAX_UINT16);

   Guid->Data4[0] = (Parameters.Arg2 & MAX_UINT8);
   Guid->Data4[1] = ((Parameters.Arg2 >> 8) & MAX_UINT8);
   Guid->Data4[2] = ((Parameters.Arg2 >> 16) & MAX_UINT8);
   Guid->Data4[3] = ((Parameters.Arg2 >> 24) & MAX_UINT8);

   Guid->Data4[4] = (Parameters.Arg3 & MAX_UINT8);
   Guid->Data4[5] = ((Parameters.Arg3 >> 8) & MAX_UINT8);
   Guid->Data4[6] = ((Parameters.Arg3 >> 16) & MAX_UINT8);
   Guid->Data4[7] = ((Parameters.Arg3 >> 24) & MAX_UINT8);

   DEBUG ((DEBUG_INFO, "FW-TRNG: UUID %g\n", Guid));

   return RETURN_SUCCESS;
 }

 /** 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
   )
 {
   return MAX_ENTROPY_BITS;
 }

 /** 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
   )
 {
   RETURN_STATUS     Status;
   ARM_MONITOR_ARGS  Parameters;
   UINTN             EntropyBytes;
   UINTN             LastValidBits;
   UINTN             BytesToClear;
   UINTN             EntropyData[3];

   if ((EntropyBits == 0)                ||
       (EntropyBits > MAX_ENTROPY_BITS)  ||
       (Buffer == NULL))
   {
     return RETURN_INVALID_PARAMETER;
   }

   EntropyBytes = (EntropyBits + 7) >> 3;
   if (EntropyBytes > BufferSize) {
     return RETURN_BAD_BUFFER_SIZE;
   }

   ZeroMem (Buffer, BufferSize);
   ZeroMem (&Parameters, sizeof (Parameters));

   Parameters.Arg0 = ARM_SMC_ID_TRNG_RND;
   Parameters.Arg1 = EntropyBits;
   ArmMonitorCall (&Parameters);

   Status = TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
   if (RETURN_ERROR (Status)) {
     return Status;
   }

   // The entropy data is returned in the Parameters.Arg<3..1>
   // With the lower order bytes in Parameters.Arg3 and the higher
   // order bytes being stored in Parameters.Arg1.
   EntropyData[0] = Parameters.Arg3;
   EntropyData[1] = Parameters.Arg2;
   EntropyData[2] = Parameters.Arg1;

   CopyMem (Buffer, EntropyData, EntropyBytes);

   // Mask off any unused top bytes, in accordance with specification.
   BytesToClear = BufferSize - EntropyBytes;
   if (BytesToClear != 0) {
     ZeroMem (&Buffer[EntropyBytes], BytesToClear);
   }

   // Clear the unused MSB bits of the last byte.
   LastValidBits = EntropyBits & 0x7;
   if (LastValidBits != 0) {
     Buffer[EntropyBytes - 1] &= (0xFF >> (8 - LastValidBits));
   }

   return Status;
 }

 /** The constructor checks that the FW-TRNG interface is supported
     by the host firmware.

   It will ASSERT() if FW-TRNG is not supported.
   It will always return RETURN_SUCCESS.

   @retval RETURN_SUCCESS   The constructor always returns RETURN_SUCCESS.
 **/
 RETURN_STATUS
 EFIAPI
 ArmTrngLibConstructor (
   VOID
   )
 {
   ARM_MONITOR_ARGS  Parameters;
   RETURN_STATUS     Status;
   UINT16            MajorRev;
   UINT16            MinorRev;
   GUID              Guid;

   ZeroMem (&Parameters, sizeof (Parameters));

   Parameters.Arg0 = SMCCC_VERSION;
   ArmMonitorCall (&Parameters);
   Status = TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
   if (RETURN_ERROR (Status)) {
     goto ErrorHandler;
   }

   // Cf [1] s2.1.3 'Caller responsibilities',
   // SMCCC version must be greater or equal than 1.1
   if ((INT32)Parameters.Arg0 < 0x10001) {
     goto ErrorHandler;
   }

   Status = GetArmTrngVersion (&MajorRev, &MinorRev);
   if (RETURN_ERROR (Status)) {
     goto ErrorHandler;
   }

   // Check that the required features are present.
   Status = GetArmTrngFeatures (ARM_SMC_ID_TRNG_RND, NULL);
   if (RETURN_ERROR (Status)) {
     goto ErrorHandler;
   }

   // Check if TRNG UUID is supported and if so trace the GUID.
   Status = GetArmTrngFeatures (ARM_SMC_ID_TRNG_GET_UUID, NULL);
   if (RETURN_ERROR (Status)) {
     goto ErrorHandler;
   }

   DEBUG_CODE_BEGIN ();

   Status = GetArmTrngUuid (&Guid);
   if (RETURN_ERROR (Status)) {
     goto ErrorHandler;
   }

   DEBUG ((
     DEBUG_INFO,
     "FW-TRNG: Version %d.%d, GUID {%g}\n",
     MajorRev,
     MinorRev,
     &Guid
     ));

   DEBUG_CODE_END ();

   return RETURN_SUCCESS;

 ErrorHandler:
   DEBUG ((DEBUG_ERROR, "ArmTrngLib could not be correctly initialized.\n"));
   return RETURN_SUCCESS;
 }
	/** @file
	Arm Firmware TRNG interface library.

	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
	- FID - Function ID
	**/

	#include <Base.h>
	#include <Library/ArmLib.h>
	#include <Library/ArmMonitorLib.h>
	#include <Library/BaseMemoryLib.h>
	#include <Library/DebugLib.h>

	#include "ArmTrngDefs.h"

	/** Convert TRNG status codes to RETURN status codes.

	@param [in] TrngStatus TRNG status code.

	@retval RETURN_SUCCESS Success.
	@retval RETURN_UNSUPPORTED Function not implemented or
	negative return code.
	@retval RETURN_INVALID_PARAMETER A parameter is invalid.
	@retval RETURN_NOT_READY No Entropy available.
	**/
	STATIC
	RETURN_STATUS
	TrngStatusToReturnStatus (
	IN INT32 TrngStatus
	)
	{
	switch (TrngStatus) {
	case TRNG_STATUS_NOT_SUPPORTED:
	return RETURN_UNSUPPORTED;

	case TRNG_STATUS_INVALID_PARAMETER:
	return RETURN_INVALID_PARAMETER;

	case TRNG_STATUS_NO_ENTROPY:
	return RETURN_NOT_READY;

	case TRNG_STATUS_SUCCESS:
	return RETURN_SUCCESS;

	default:
	if (TrngStatus < 0) {
	return RETURN_UNSUPPORTED;
	}

	return RETURN_SUCCESS;
	}
	}

	/** 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
	)
	{
	RETURN_STATUS Status;
	ARM_MONITOR_ARGS Parameters;
	INT32 Revision;

	if ((MajorRevision == NULL) \|\| (MinorRevision == NULL)) {
	return RETURN_INVALID_PARAMETER;
	}

	ZeroMem (&Parameters, sizeof (Parameters));

	Parameters.Arg0 = ARM_SMC_ID_TRNG_VERSION;
	ArmMonitorCall (&Parameters);

	Revision = (INT32)Parameters.Arg0;
	Status = TrngStatusToReturnStatus (Revision);
	if (RETURN_ERROR (Status)) {
	return Status;
	}

	*MinorRevision = (Revision & TRNG_REV_MINOR_MASK);
	*MajorRevision = ((Revision >> TRNG_REV_MAJOR_SHIFT) & TRNG_REV_MAJOR_MASK);
	return RETURN_SUCCESS;
	}

	/** Get the features supported by the Arm TRNG backend.

	The caller can determine if functions defined in the Arm TRNG ABI are
	present in the ABI implementation.

	@param [in] FunctionId Function Id.
	@param [out] Capability Function specific capability if present.

	@retval RETURN_SUCCESS The function completed successfully.
	@retval RETURN_INVALID_PARAMETER Invalid parameter.
	@retval RETURN_UNSUPPORTED Function not implemented.
	**/
	STATIC
	RETURN_STATUS
	EFIAPI
	GetArmTrngFeatures (
	IN CONST UINT32 FunctionId,
	OUT UINT32 *Capability OPTIONAL
	)
	{
	ARM_MONITOR_ARGS Parameters;
	RETURN_STATUS Status;

	ZeroMem (&Parameters, sizeof (Parameters));

	Parameters.Arg0 = ARM_SMC_ID_TRNG_FEATURES;
	Parameters.Arg1 = FunctionId;
	ArmMonitorCall (&Parameters);

	Status = TrngStatusToReturnStatus (Parameters.Arg0);
	if (RETURN_ERROR (Status)) {
	return Status;
	}

	if (Capability != NULL) {
	*Capability = (UINT32)Parameters.Arg0;
	}

	return RETURN_SUCCESS;
	}

	/** 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
	)
	{
	ARM_MONITOR_ARGS Parameters;

	if (Guid == NULL) {
	return RETURN_INVALID_PARAMETER;
	}

	ZeroMem (&Parameters, sizeof (Parameters));

	Parameters.Arg0 = ARM_SMC_ID_TRNG_GET_UUID;
	ArmMonitorCall (&Parameters);

	// Only invalid value is TRNG_STATUS_NOT_SUPPORTED (-1).
	if ((INT32)Parameters.Arg0 == TRNG_STATUS_NOT_SUPPORTED) {
	return TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
	}

	Guid->Data1 = (Parameters.Arg0 & MAX_UINT32);
	Guid->Data2 = (Parameters.Arg1 & MAX_UINT16);
	Guid->Data3 = ((Parameters.Arg1 >> 16) & MAX_UINT16);

	Guid->Data4[0] = (Parameters.Arg2 & MAX_UINT8);
	Guid->Data4[1] = ((Parameters.Arg2 >> 8) & MAX_UINT8);
	Guid->Data4[2] = ((Parameters.Arg2 >> 16) & MAX_UINT8);
	Guid->Data4[3] = ((Parameters.Arg2 >> 24) & MAX_UINT8);

	Guid->Data4[4] = (Parameters.Arg3 & MAX_UINT8);
	Guid->Data4[5] = ((Parameters.Arg3 >> 8) & MAX_UINT8);
	Guid->Data4[6] = ((Parameters.Arg3 >> 16) & MAX_UINT8);
	Guid->Data4[7] = ((Parameters.Arg3 >> 24) & MAX_UINT8);

	DEBUG ((DEBUG_INFO, "FW-TRNG: UUID %g\n", Guid));

	return RETURN_SUCCESS;
	}

	/** 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
	)
	{
	return MAX_ENTROPY_BITS;
	}

	/** 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
	)
	{
	RETURN_STATUS Status;
	ARM_MONITOR_ARGS Parameters;
	UINTN EntropyBytes;
	UINTN LastValidBits;
	UINTN BytesToClear;
	UINTN EntropyData[3];

	if ((EntropyBits == 0) \|\|
	(EntropyBits > MAX_ENTROPY_BITS) \|\|
	(Buffer == NULL))
	{
	return RETURN_INVALID_PARAMETER;
	}

	EntropyBytes = (EntropyBits + 7) >> 3;
	if (EntropyBytes > BufferSize) {
	return RETURN_BAD_BUFFER_SIZE;
	}

	ZeroMem (Buffer, BufferSize);
	ZeroMem (&Parameters, sizeof (Parameters));

	Parameters.Arg0 = ARM_SMC_ID_TRNG_RND;
	Parameters.Arg1 = EntropyBits;
	ArmMonitorCall (&Parameters);

	Status = TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
	if (RETURN_ERROR (Status)) {
	return Status;
	}

	// The entropy data is returned in the Parameters.Arg<3..1>
	// With the lower order bytes in Parameters.Arg3 and the higher
	// order bytes being stored in Parameters.Arg1.
	EntropyData[0] = Parameters.Arg3;
	EntropyData[1] = Parameters.Arg2;
	EntropyData[2] = Parameters.Arg1;

	CopyMem (Buffer, EntropyData, EntropyBytes);

	// Mask off any unused top bytes, in accordance with specification.
	BytesToClear = BufferSize - EntropyBytes;
	if (BytesToClear != 0) {
	ZeroMem (&Buffer[EntropyBytes], BytesToClear);
	}

	// Clear the unused MSB bits of the last byte.
	LastValidBits = EntropyBits & 0x7;
	if (LastValidBits != 0) {
	Buffer[EntropyBytes - 1] &= (0xFF >> (8 - LastValidBits));
	}

	return Status;
	}

	/** The constructor checks that the FW-TRNG interface is supported
	by the host firmware.

	It will ASSERT() if FW-TRNG is not supported.
	It will always return RETURN_SUCCESS.

	@retval RETURN_SUCCESS The constructor always returns RETURN_SUCCESS.
	**/
	RETURN_STATUS
	EFIAPI
	ArmTrngLibConstructor (
	VOID
	)
	{
	ARM_MONITOR_ARGS Parameters;
	RETURN_STATUS Status;
	UINT16 MajorRev;
	UINT16 MinorRev;
	GUID Guid;

	ZeroMem (&Parameters, sizeof (Parameters));

	Parameters.Arg0 = SMCCC_VERSION;
	ArmMonitorCall (&Parameters);
	Status = TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
	if (RETURN_ERROR (Status)) {
	goto ErrorHandler;
	}

	// Cf [1] s2.1.3 'Caller responsibilities',
	// SMCCC version must be greater or equal than 1.1
	if ((INT32)Parameters.Arg0 < 0x10001) {
	goto ErrorHandler;
	}

	Status = GetArmTrngVersion (&MajorRev, &MinorRev);
	if (RETURN_ERROR (Status)) {
	goto ErrorHandler;
	}

	// Check that the required features are present.
	Status = GetArmTrngFeatures (ARM_SMC_ID_TRNG_RND, NULL);
	if (RETURN_ERROR (Status)) {
	goto ErrorHandler;
	}

	// Check if TRNG UUID is supported and if so trace the GUID.
	Status = GetArmTrngFeatures (ARM_SMC_ID_TRNG_GET_UUID, NULL);
	if (RETURN_ERROR (Status)) {
	goto ErrorHandler;
	}

	DEBUG_CODE_BEGIN ();

	Status = GetArmTrngUuid (&Guid);
	if (RETURN_ERROR (Status)) {
	goto ErrorHandler;
	}

	DEBUG ((
	DEBUG_INFO,
	"FW-TRNG: Version %d.%d, GUID {%g}\n",
	MajorRev,
	MinorRev,
	&Guid
	));

	DEBUG_CODE_END ();

	return RETURN_SUCCESS;

	ErrorHandler:
	DEBUG ((DEBUG_ERROR, "ArmTrngLib could not be correctly initialized.\n"));
	return RETURN_SUCCESS;
	}