SecurityPkg/Tcg/Tcg2Smm/Tcg2Smm.c - third_party/edk2 - Git at Google

 /** @file
   It updates TPM2 items in ACPI table and registers SMI2 callback
   functions for Tcg2 physical presence, ClearMemory, and sample
   for dTPM StartMethod.

   Caution: This module requires additional review when modified.
   This driver will have external input - variable and ACPINvs data in SMM mode.
   This external input must be validated carefully to avoid security issue.

   PhysicalPresenceCallback() and MemoryClearCallback() will receive untrusted input and do some check.

 Copyright (c) 2015 - 2018, Intel Corporation. All rights reserved.<BR>
 Copyright (c) Microsoft Corporation.
 SPDX-License-Identifier: BSD-2-Clause-Patent

 **/

 #include "Tcg2Smm.h"

 EFI_SMM_VARIABLE_PROTOCOL  *mSmmVariable = NULL;
 TCG_NVS                    *mTcgNvs = NULL;
 UINTN                       mPpSoftwareSmi;
 UINTN                       mMcSoftwareSmi;
 EFI_HANDLE                  mReadyToLockHandle;

 /**
   Communication service SMI Handler entry.

   This handler takes requests to exchange Mmi channel and Nvs address between MM and DXE.

   Caution: This function may receive untrusted input.
   Communicate buffer and buffer size are external input, so this function will do basic validation.

   @param[in]      DispatchHandle    The unique handle assigned to this handler by SmiHandlerRegister().
   @param[in]      RegisterContext   Points to an optional handler context which was specified when the
                                     handler was registered.
   @param[in, out] CommBuffer        A pointer to a collection of data in memory that will
                                     be conveyed from a non-SMM environment into an SMM environment.
   @param[in, out] CommBufferSize    The size of the CommBuffer.

   @retval EFI_SUCCESS               The interrupt was handled and quiesced. No other handlers
                                     should still be called.
   @retval EFI_UNSUPPORTED           An unknown test function was requested.
   @retval EFI_ACCESS_DENIED         Part of the communication buffer lies in an invalid region.

 **/
 EFI_STATUS
 EFIAPI
 TpmNvsCommunciate (
   IN     EFI_HANDLE                   DispatchHandle,
   IN     CONST VOID                   *RegisterContext,
   IN OUT VOID                         *CommBuffer,
   IN OUT UINTN                        *CommBufferSize
   )
 {
   EFI_STATUS                Status;
   UINTN                     TempCommBufferSize;
   TPM_NVS_MM_COMM_BUFFER    *CommParams;

   DEBUG ((DEBUG_VERBOSE, "%a()\n", __FUNCTION__));

   //
   // If input is invalid, stop processing this SMI
   //
   if (CommBuffer == NULL || CommBufferSize == NULL) {
     return EFI_SUCCESS;
   }

   TempCommBufferSize = *CommBufferSize;

   if(TempCommBufferSize != sizeof (TPM_NVS_MM_COMM_BUFFER)) {
     DEBUG ((DEBUG_ERROR, "[%a] MM Communication buffer size is invalid for this handler!\n", __FUNCTION__));
     return EFI_ACCESS_DENIED;
   }
   if (!IsBufferOutsideMmValid ((UINTN) CommBuffer, TempCommBufferSize)) {
     DEBUG ((DEBUG_ERROR, "[%a] - MM Communication buffer in invalid location!\n", __FUNCTION__));
     return EFI_ACCESS_DENIED;
   }

   //
   // Farm out the job to individual functions based on what was requested.
   //
   CommParams = (TPM_NVS_MM_COMM_BUFFER*) CommBuffer;
   Status = EFI_SUCCESS;
   switch (CommParams->Function) {
     case TpmNvsMmExchangeInfo:
       DEBUG ((DEBUG_VERBOSE, "[%a] - Function requested: MM_EXCHANGE_NVS_INFO\n", __FUNCTION__));
       CommParams->RegisteredPpSwiValue = mPpSoftwareSmi;
       CommParams->RegisteredMcSwiValue = mMcSoftwareSmi;
       mTcgNvs = (TCG_NVS*) (UINTN) CommParams->TargetAddress;
       break;

     default:
       DEBUG ((DEBUG_INFO, "[%a] - Unknown function %d!\n", __FUNCTION__, CommParams->Function));
       Status = EFI_UNSUPPORTED;
       break;
   }

   CommParams->ReturnStatus = (UINT64) Status;
   return EFI_SUCCESS;
 }

 /**
   Software SMI callback for TPM physical presence which is called from ACPI method.

   Caution: This function may receive untrusted input.
   Variable and ACPINvs are external input, so this function will validate
   its data structure to be valid value.

   @param[in]      DispatchHandle  The unique handle assigned to this handler by SmiHandlerRegister().
   @param[in]      Context         Points to an optional handler context which was specified when the
                                   handler was registered.
   @param[in, out] CommBuffer      A pointer to a collection of data in memory that will
                                   be conveyed from a non-SMM environment into an SMM environment.
   @param[in, out] CommBufferSize  The size of the CommBuffer.

   @retval EFI_SUCCESS             The interrupt was handled successfully.

 **/
 EFI_STATUS
 EFIAPI
 PhysicalPresenceCallback (
   IN EFI_HANDLE                  DispatchHandle,
   IN CONST VOID                  *Context,
   IN OUT VOID                    *CommBuffer,
   IN OUT UINTN                   *CommBufferSize
   )
 {
   UINT32                MostRecentRequest;
   UINT32                Response;
   UINT32                OperationRequest;
   UINT32                RequestParameter;


   if (mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_RETURN_REQUEST_RESPONSE_TO_OS) {
     mTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibReturnOperationResponseToOsFunction (
                                              &MostRecentRequest,
                                              &Response
                                              );
     mTcgNvs->PhysicalPresence.LastRequest = MostRecentRequest;
     mTcgNvs->PhysicalPresence.Response = Response;
     return EFI_SUCCESS;
   } else if ((mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_SUBMIT_REQUEST_TO_BIOS)
           || (mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_SUBMIT_REQUEST_TO_BIOS_2)) {

     OperationRequest = mTcgNvs->PhysicalPresence.Request;
     RequestParameter = mTcgNvs->PhysicalPresence.RequestParameter;
     mTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibSubmitRequestToPreOSFunctionEx (
                                              &OperationRequest,
                                              &RequestParameter
                                              );
     mTcgNvs->PhysicalPresence.Request = OperationRequest;
     mTcgNvs->PhysicalPresence.RequestParameter = RequestParameter;
   } else if (mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_GET_USER_CONFIRMATION_STATUS_FOR_REQUEST) {
     mTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibGetUserConfirmationStatusFunction (mTcgNvs->PPRequestUserConfirm);
   }

   return EFI_SUCCESS;
 }


 /**
   Software SMI callback for MemoryClear which is called from ACPI method.

   Caution: This function may receive untrusted input.
   Variable and ACPINvs are external input, so this function will validate
   its data structure to be valid value.

   @param[in]      DispatchHandle  The unique handle assigned to this handler by SmiHandlerRegister().
   @param[in]      Context         Points to an optional handler context which was specified when the
                                   handler was registered.
   @param[in, out] CommBuffer      A pointer to a collection of data in memory that will
                                   be conveyed from a non-SMM environment into an SMM environment.
   @param[in, out] CommBufferSize  The size of the CommBuffer.

   @retval EFI_SUCCESS             The interrupt was handled successfully.

 **/
 EFI_STATUS
 EFIAPI
 MemoryClearCallback (
   IN EFI_HANDLE                  DispatchHandle,
   IN CONST VOID                  *Context,
   IN OUT VOID                    *CommBuffer,
   IN OUT UINTN                   *CommBufferSize
   )
 {
   EFI_STATUS                     Status;
   UINTN                          DataSize;
   UINT8                          MorControl;

   mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_SUCCESS;
   if (mTcgNvs->MemoryClear.Parameter == ACPI_FUNCTION_DSM_MEMORY_CLEAR_INTERFACE) {
     MorControl = (UINT8) mTcgNvs->MemoryClear.Request;
   } else if (mTcgNvs->MemoryClear.Parameter == ACPI_FUNCTION_PTS_CLEAR_MOR_BIT) {
     DataSize = sizeof (UINT8);
     Status = mSmmVariable->SmmGetVariable (
                              MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
                              &gEfiMemoryOverwriteControlDataGuid,
                              NULL,
                              &DataSize,
                              &MorControl
                              );
     if (EFI_ERROR (Status)) {
       mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_GENERAL_FAILURE;
       DEBUG ((EFI_D_ERROR, "[TPM] Get MOR variable failure! Status = %r\n", Status));
       return EFI_SUCCESS;
     }

     if (MOR_CLEAR_MEMORY_VALUE (MorControl) == 0x0) {
       return EFI_SUCCESS;
     }
     MorControl &= ~MOR_CLEAR_MEMORY_BIT_MASK;
   } else {
     mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_GENERAL_FAILURE;
     DEBUG ((EFI_D_ERROR, "[TPM] MOR Parameter error! Parameter = %x\n", mTcgNvs->MemoryClear.Parameter));
     return EFI_SUCCESS;
   }

   DataSize = sizeof (UINT8);
   Status = mSmmVariable->SmmSetVariable (
                            MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
                            &gEfiMemoryOverwriteControlDataGuid,
                            EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
                            DataSize,
                            &MorControl
                            );
   if (EFI_ERROR (Status)) {
     mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_GENERAL_FAILURE;
     DEBUG ((EFI_D_ERROR, "[TPM] Set MOR variable failure! Status = %r\n", Status));
   }

   return EFI_SUCCESS;
 }

 /**
   Notification for SMM ReadyToLock protocol.

   @param[in] Protocol   Points to the protocol's unique identifier.
   @param[in] Interface  Points to the interface instance.
   @param[in] Handle     The handle on which the interface was installed.

   @retval EFI_SUCCESS   Notification runs successfully.

 **/
 EFI_STATUS
 EFIAPI
 TcgMmReadyToLock (
   IN CONST EFI_GUID  *Protocol,
   IN VOID            *Interface,
   IN EFI_HANDLE      Handle
 )
 {
   EFI_STATUS Status;

   Status = EFI_SUCCESS;

   if (mReadyToLockHandle != NULL) {
     Status = gMmst->MmiHandlerUnRegister (mReadyToLockHandle);
     mReadyToLockHandle = NULL;
   }
   return Status;
 }

 /**
   The driver's common initialization routine.

   It install callbacks for TPM physical presence and MemoryClear, and locate
   SMM variable to be used in the callback function.

   @retval EFI_SUCCESS     The entry point is executed successfully.
   @retval Others          Some error occurs when executing this entry point.

 **/
 EFI_STATUS
 InitializeTcgCommon (
   VOID
   )
 {
   EFI_STATUS                     Status;
   EFI_SMM_SW_DISPATCH2_PROTOCOL  *SwDispatch;
   EFI_SMM_SW_REGISTER_CONTEXT    SwContext;
   EFI_HANDLE                     PpSwHandle;
   EFI_HANDLE                     McSwHandle;
   EFI_HANDLE                     NotifyHandle;

   if (!CompareGuid (PcdGetPtr(PcdTpmInstanceGuid), &gEfiTpmDeviceInstanceTpm20DtpmGuid)){
     DEBUG ((EFI_D_ERROR, "No TPM2 DTPM instance required!\n"));
     return EFI_UNSUPPORTED;
   }

   // Initialize variables first
   mReadyToLockHandle = NULL;
   SwDispatch = NULL;
   PpSwHandle = NULL;
   McSwHandle = NULL;
   NotifyHandle = NULL;

   // Register a root handler to communicate the NVS region and SMI channel between MM and DXE
   Status = gMmst->MmiHandlerRegister (TpmNvsCommunciate, &gTpmNvsMmGuid, &mReadyToLockHandle);
   ASSERT_EFI_ERROR (Status);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "[%a] Failed to register NVS communicate as root MM handler - %r!\n", __FUNCTION__, Status));
     goto Cleanup;
   }

   //
   // Get the Sw dispatch protocol and register SMI callback functions.
   //
   Status = gMmst->MmLocateProtocol (&gEfiSmmSwDispatch2ProtocolGuid, NULL, (VOID**)&SwDispatch);
   ASSERT_EFI_ERROR (Status);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "[%a] Failed to locate Sw dispatch protocol - %r!\n", __FUNCTION__, Status));
     goto Cleanup;
   }

   SwContext.SwSmiInputValue = (UINTN) -1;
   Status = SwDispatch->Register (SwDispatch, PhysicalPresenceCallback, &SwContext, &PpSwHandle);
   ASSERT_EFI_ERROR (Status);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "[%a] Failed to register PP callback as SW MM handler - %r!\n", __FUNCTION__, Status));
     goto Cleanup;
   }
   mPpSoftwareSmi = SwContext.SwSmiInputValue;

   SwContext.SwSmiInputValue = (UINTN) -1;
   Status = SwDispatch->Register (SwDispatch, MemoryClearCallback, &SwContext, &McSwHandle);
   ASSERT_EFI_ERROR (Status);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "[%a] Failed to register MC callback as SW MM handler - %r!\n", __FUNCTION__, Status));
     goto Cleanup;
   }
   mMcSoftwareSmi = SwContext.SwSmiInputValue;

   //
   // Locate SmmVariableProtocol.
   //
   Status = gMmst->MmLocateProtocol (&gEfiSmmVariableProtocolGuid, NULL, (VOID**)&mSmmVariable);
   ASSERT_EFI_ERROR (Status);
   if (EFI_ERROR (Status)) {
     // Should not happen
     DEBUG ((DEBUG_ERROR, "[%a] Failed to locate SMM variable protocol - %r!\n", __FUNCTION__, Status));
     goto Cleanup;
   }

   // Turn off the light before leaving the room... at least, take a remote...
   Status = gMmst->MmRegisterProtocolNotify (&gEfiMmReadyToLockProtocolGuid, TcgMmReadyToLock, &NotifyHandle);
   ASSERT_EFI_ERROR (Status);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "[%a] Failed to register ready to lock notification - %r!\n", __FUNCTION__, Status));
     goto Cleanup;
   }

   Tcg2NotifyMmReady ();

 Cleanup:
   if (EFI_ERROR (Status)) {
     // Something is whacked, clean up the mess...
     if (NotifyHandle != NULL) {
       gMmst->MmRegisterProtocolNotify (&gEfiMmReadyToLockProtocolGuid, NULL, &NotifyHandle);
     }
     if (McSwHandle != NULL && SwDispatch != NULL) {
       SwDispatch->UnRegister (SwDispatch, McSwHandle);
     }
     if (PpSwHandle != NULL && SwDispatch != NULL) {
       SwDispatch->UnRegister (SwDispatch, PpSwHandle);
     }
     if (mReadyToLockHandle != NULL) {
       gMmst->MmiHandlerUnRegister (mReadyToLockHandle);
     }
   }

   return Status;
 }
	/** @file
	It updates TPM2 items in ACPI table and registers SMI2 callback
	functions for Tcg2 physical presence, ClearMemory, and sample
	for dTPM StartMethod.

	Caution: This module requires additional review when modified.
	This driver will have external input - variable and ACPINvs data in SMM mode.
	This external input must be validated carefully to avoid security issue.

	PhysicalPresenceCallback() and MemoryClearCallback() will receive untrusted input and do some check.

	Copyright (c) 2015 - 2018, Intel Corporation. All rights reserved.<BR>
	Copyright (c) Microsoft Corporation.
	SPDX-License-Identifier: BSD-2-Clause-Patent

	**/

	#include "Tcg2Smm.h"

	EFI_SMM_VARIABLE_PROTOCOL *mSmmVariable = NULL;
	TCG_NVS *mTcgNvs = NULL;
	UINTN mPpSoftwareSmi;
	UINTN mMcSoftwareSmi;
	EFI_HANDLE mReadyToLockHandle;

	/**
	Communication service SMI Handler entry.

	This handler takes requests to exchange Mmi channel and Nvs address between MM and DXE.

	Caution: This function may receive untrusted input.
	Communicate buffer and buffer size are external input, so this function will do basic validation.

	@param[in] DispatchHandle The unique handle assigned to this handler by SmiHandlerRegister().
	@param[in] RegisterContext Points to an optional handler context which was specified when the
	handler was registered.
	@param[in, out] CommBuffer A pointer to a collection of data in memory that will
	be conveyed from a non-SMM environment into an SMM environment.
	@param[in, out] CommBufferSize The size of the CommBuffer.

	@retval EFI_SUCCESS The interrupt was handled and quiesced. No other handlers
	should still be called.
	@retval EFI_UNSUPPORTED An unknown test function was requested.
	@retval EFI_ACCESS_DENIED Part of the communication buffer lies in an invalid region.

	**/
	EFI_STATUS
	EFIAPI
	TpmNvsCommunciate (
	IN EFI_HANDLE DispatchHandle,
	IN CONST VOID *RegisterContext,
	IN OUT VOID *CommBuffer,
	IN OUT UINTN *CommBufferSize
	)
	{
	EFI_STATUS Status;
	UINTN TempCommBufferSize;
	TPM_NVS_MM_COMM_BUFFER *CommParams;

	DEBUG ((DEBUG_VERBOSE, "%a()\n", __FUNCTION__));

	//
	// If input is invalid, stop processing this SMI
	//
	if (CommBuffer == NULL \|\| CommBufferSize == NULL) {
	return EFI_SUCCESS;
	}

	TempCommBufferSize = *CommBufferSize;

	if(TempCommBufferSize != sizeof (TPM_NVS_MM_COMM_BUFFER)) {
	DEBUG ((DEBUG_ERROR, "[%a] MM Communication buffer size is invalid for this handler!\n", __FUNCTION__));
	return EFI_ACCESS_DENIED;
	}
	if (!IsBufferOutsideMmValid ((UINTN) CommBuffer, TempCommBufferSize)) {
	DEBUG ((DEBUG_ERROR, "[%a] - MM Communication buffer in invalid location!\n", __FUNCTION__));
	return EFI_ACCESS_DENIED;
	}

	//
	// Farm out the job to individual functions based on what was requested.
	//
	CommParams = (TPM_NVS_MM_COMM_BUFFER*) CommBuffer;
	Status = EFI_SUCCESS;
	switch (CommParams->Function) {
	case TpmNvsMmExchangeInfo:
	DEBUG ((DEBUG_VERBOSE, "[%a] - Function requested: MM_EXCHANGE_NVS_INFO\n", __FUNCTION__));
	CommParams->RegisteredPpSwiValue = mPpSoftwareSmi;
	CommParams->RegisteredMcSwiValue = mMcSoftwareSmi;
	mTcgNvs = (TCG_NVS*) (UINTN) CommParams->TargetAddress;
	break;

	default:
	DEBUG ((DEBUG_INFO, "[%a] - Unknown function %d!\n", __FUNCTION__, CommParams->Function));
	Status = EFI_UNSUPPORTED;
	break;
	}

	CommParams->ReturnStatus = (UINT64) Status;
	return EFI_SUCCESS;
	}

	/**
	Software SMI callback for TPM physical presence which is called from ACPI method.

	Caution: This function may receive untrusted input.
	Variable and ACPINvs are external input, so this function will validate
	its data structure to be valid value.

	@param[in] DispatchHandle The unique handle assigned to this handler by SmiHandlerRegister().
	@param[in] Context Points to an optional handler context which was specified when the
	handler was registered.
	@param[in, out] CommBuffer A pointer to a collection of data in memory that will
	be conveyed from a non-SMM environment into an SMM environment.
	@param[in, out] CommBufferSize The size of the CommBuffer.

	@retval EFI_SUCCESS The interrupt was handled successfully.

	**/
	EFI_STATUS
	EFIAPI
	PhysicalPresenceCallback (
	IN EFI_HANDLE DispatchHandle,
	IN CONST VOID *Context,
	IN OUT VOID *CommBuffer,
	IN OUT UINTN *CommBufferSize
	)
	{
	UINT32 MostRecentRequest;
	UINT32 Response;
	UINT32 OperationRequest;
	UINT32 RequestParameter;


	if (mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_RETURN_REQUEST_RESPONSE_TO_OS) {
	mTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibReturnOperationResponseToOsFunction (
	&MostRecentRequest,
	&Response
	);
	mTcgNvs->PhysicalPresence.LastRequest = MostRecentRequest;
	mTcgNvs->PhysicalPresence.Response = Response;
	return EFI_SUCCESS;
	} else if ((mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_SUBMIT_REQUEST_TO_BIOS)
	\|\| (mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_SUBMIT_REQUEST_TO_BIOS_2)) {

	OperationRequest = mTcgNvs->PhysicalPresence.Request;
	RequestParameter = mTcgNvs->PhysicalPresence.RequestParameter;
	mTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibSubmitRequestToPreOSFunctionEx (
	&OperationRequest,
	&RequestParameter
	);
	mTcgNvs->PhysicalPresence.Request = OperationRequest;
	mTcgNvs->PhysicalPresence.RequestParameter = RequestParameter;
	} else if (mTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_GET_USER_CONFIRMATION_STATUS_FOR_REQUEST) {
	mTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibGetUserConfirmationStatusFunction (mTcgNvs->PPRequestUserConfirm);
	}

	return EFI_SUCCESS;
	}


	/**
	Software SMI callback for MemoryClear which is called from ACPI method.

	Caution: This function may receive untrusted input.
	Variable and ACPINvs are external input, so this function will validate
	its data structure to be valid value.

	@param[in] DispatchHandle The unique handle assigned to this handler by SmiHandlerRegister().
	@param[in] Context Points to an optional handler context which was specified when the
	handler was registered.
	@param[in, out] CommBuffer A pointer to a collection of data in memory that will
	be conveyed from a non-SMM environment into an SMM environment.
	@param[in, out] CommBufferSize The size of the CommBuffer.

	@retval EFI_SUCCESS The interrupt was handled successfully.

	**/
	EFI_STATUS
	EFIAPI
	MemoryClearCallback (
	IN EFI_HANDLE DispatchHandle,
	IN CONST VOID *Context,
	IN OUT VOID *CommBuffer,
	IN OUT UINTN *CommBufferSize
	)
	{
	EFI_STATUS Status;
	UINTN DataSize;
	UINT8 MorControl;

	mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_SUCCESS;
	if (mTcgNvs->MemoryClear.Parameter == ACPI_FUNCTION_DSM_MEMORY_CLEAR_INTERFACE) {
	MorControl = (UINT8) mTcgNvs->MemoryClear.Request;
	} else if (mTcgNvs->MemoryClear.Parameter == ACPI_FUNCTION_PTS_CLEAR_MOR_BIT) {
	DataSize = sizeof (UINT8);
	Status = mSmmVariable->SmmGetVariable (
	MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
	&gEfiMemoryOverwriteControlDataGuid,
	NULL,
	&DataSize,
	&MorControl
	);
	if (EFI_ERROR (Status)) {
	mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_GENERAL_FAILURE;
	DEBUG ((EFI_D_ERROR, "[TPM] Get MOR variable failure! Status = %r\n", Status));
	return EFI_SUCCESS;
	}

	if (MOR_CLEAR_MEMORY_VALUE (MorControl) == 0x0) {
	return EFI_SUCCESS;
	}
	MorControl &= ~MOR_CLEAR_MEMORY_BIT_MASK;
	} else {
	mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_GENERAL_FAILURE;
	DEBUG ((EFI_D_ERROR, "[TPM] MOR Parameter error! Parameter = %x\n", mTcgNvs->MemoryClear.Parameter));
	return EFI_SUCCESS;
	}

	DataSize = sizeof (UINT8);
	Status = mSmmVariable->SmmSetVariable (
	MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
	&gEfiMemoryOverwriteControlDataGuid,
	EFI_VARIABLE_NON_VOLATILE \| EFI_VARIABLE_BOOTSERVICE_ACCESS \| EFI_VARIABLE_RUNTIME_ACCESS,
	DataSize,
	&MorControl
	);
	if (EFI_ERROR (Status)) {
	mTcgNvs->MemoryClear.ReturnCode = MOR_REQUEST_GENERAL_FAILURE;
	DEBUG ((EFI_D_ERROR, "[TPM] Set MOR variable failure! Status = %r\n", Status));
	}

	return EFI_SUCCESS;
	}

	/**
	Notification for SMM ReadyToLock protocol.

	@param[in] Protocol Points to the protocol's unique identifier.
	@param[in] Interface Points to the interface instance.
	@param[in] Handle The handle on which the interface was installed.

	@retval EFI_SUCCESS Notification runs successfully.

	**/
	EFI_STATUS
	EFIAPI
	TcgMmReadyToLock (
	IN CONST EFI_GUID *Protocol,
	IN VOID *Interface,
	IN EFI_HANDLE Handle
	)
	{
	EFI_STATUS Status;

	Status = EFI_SUCCESS;

	if (mReadyToLockHandle != NULL) {
	Status = gMmst->MmiHandlerUnRegister (mReadyToLockHandle);
	mReadyToLockHandle = NULL;
	}
	return Status;
	}

	/**
	The driver's common initialization routine.

	It install callbacks for TPM physical presence and MemoryClear, and locate
	SMM variable to be used in the callback function.

	@retval EFI_SUCCESS The entry point is executed successfully.
	@retval Others Some error occurs when executing this entry point.

	**/
	EFI_STATUS
	InitializeTcgCommon (
	VOID
	)
	{
	EFI_STATUS Status;
	EFI_SMM_SW_DISPATCH2_PROTOCOL *SwDispatch;
	EFI_SMM_SW_REGISTER_CONTEXT SwContext;
	EFI_HANDLE PpSwHandle;
	EFI_HANDLE McSwHandle;
	EFI_HANDLE NotifyHandle;

	if (!CompareGuid (PcdGetPtr(PcdTpmInstanceGuid), &gEfiTpmDeviceInstanceTpm20DtpmGuid)){
	DEBUG ((EFI_D_ERROR, "No TPM2 DTPM instance required!\n"));
	return EFI_UNSUPPORTED;
	}

	// Initialize variables first
	mReadyToLockHandle = NULL;
	SwDispatch = NULL;
	PpSwHandle = NULL;
	McSwHandle = NULL;
	NotifyHandle = NULL;

	// Register a root handler to communicate the NVS region and SMI channel between MM and DXE
	Status = gMmst->MmiHandlerRegister (TpmNvsCommunciate, &gTpmNvsMmGuid, &mReadyToLockHandle);
	ASSERT_EFI_ERROR (Status);
	if (EFI_ERROR (Status)) {
	DEBUG ((DEBUG_ERROR, "[%a] Failed to register NVS communicate as root MM handler - %r!\n", __FUNCTION__, Status));
	goto Cleanup;
	}

	//
	// Get the Sw dispatch protocol and register SMI callback functions.
	//
	Status = gMmst->MmLocateProtocol (&gEfiSmmSwDispatch2ProtocolGuid, NULL, (VOID**)&SwDispatch);
	ASSERT_EFI_ERROR (Status);
	if (EFI_ERROR (Status)) {
	DEBUG ((DEBUG_ERROR, "[%a] Failed to locate Sw dispatch protocol - %r!\n", __FUNCTION__, Status));
	goto Cleanup;
	}

	SwContext.SwSmiInputValue = (UINTN) -1;
	Status = SwDispatch->Register (SwDispatch, PhysicalPresenceCallback, &SwContext, &PpSwHandle);
	ASSERT_EFI_ERROR (Status);
	if (EFI_ERROR (Status)) {
	DEBUG ((DEBUG_ERROR, "[%a] Failed to register PP callback as SW MM handler - %r!\n", __FUNCTION__, Status));
	goto Cleanup;
	}
	mPpSoftwareSmi = SwContext.SwSmiInputValue;

	SwContext.SwSmiInputValue = (UINTN) -1;
	Status = SwDispatch->Register (SwDispatch, MemoryClearCallback, &SwContext, &McSwHandle);
	ASSERT_EFI_ERROR (Status);
	if (EFI_ERROR (Status)) {
	DEBUG ((DEBUG_ERROR, "[%a] Failed to register MC callback as SW MM handler - %r!\n", __FUNCTION__, Status));
	goto Cleanup;
	}
	mMcSoftwareSmi = SwContext.SwSmiInputValue;

	//
	// Locate SmmVariableProtocol.
	//
	Status = gMmst->MmLocateProtocol (&gEfiSmmVariableProtocolGuid, NULL, (VOID**)&mSmmVariable);
	ASSERT_EFI_ERROR (Status);
	if (EFI_ERROR (Status)) {
	// Should not happen
	DEBUG ((DEBUG_ERROR, "[%a] Failed to locate SMM variable protocol - %r!\n", __FUNCTION__, Status));
	goto Cleanup;
	}

	// Turn off the light before leaving the room... at least, take a remote...
	Status = gMmst->MmRegisterProtocolNotify (&gEfiMmReadyToLockProtocolGuid, TcgMmReadyToLock, &NotifyHandle);
	ASSERT_EFI_ERROR (Status);
	if (EFI_ERROR (Status)) {
	DEBUG ((DEBUG_ERROR, "[%a] Failed to register ready to lock notification - %r!\n", __FUNCTION__, Status));
	goto Cleanup;
	}

	Tcg2NotifyMmReady ();

	Cleanup:
	if (EFI_ERROR (Status)) {
	// Something is whacked, clean up the mess...
	if (NotifyHandle != NULL) {
	gMmst->MmRegisterProtocolNotify (&gEfiMmReadyToLockProtocolGuid, NULL, &NotifyHandle);
	}
	if (McSwHandle != NULL && SwDispatch != NULL) {
	SwDispatch->UnRegister (SwDispatch, McSwHandle);
	}
	if (PpSwHandle != NULL && SwDispatch != NULL) {
	SwDispatch->UnRegister (SwDispatch, PpSwHandle);
	}
	if (mReadyToLockHandle != NULL) {
	gMmst->MmiHandlerUnRegister (mReadyToLockHandle);
	}
	}

	return Status;
	}