Example #1
0
/**
  Communication service SMI Handler entry.

  This SMI handler provides services for the variable wrapper driver.

  Caution: This function may receive untrusted input.
  This variable data and communicate buffer are external input, so this function will do basic validation.
  Each sub function VariableServiceGetVariable(), VariableServiceGetNextVariableName(),
  VariableServiceSetVariable(), VariableServiceQueryVariableInfo(), ReclaimForOS(),
  SmmVariableGetStatistics() should also do validation based on its own knowledge.

  @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_WARN_INTERRUPT_SOURCE_QUIESCED  The interrupt has been quiesced but other handlers should
                                              still be called.
  @retval EFI_WARN_INTERRUPT_SOURCE_PENDING   The interrupt is still pending and other handlers should still
                                              be called.
  @retval EFI_INTERRUPT_PENDING               The interrupt could not be quiesced.
**/
EFI_STATUS
EFIAPI
SmmVariableHandler (
  IN     EFI_HANDLE                                DispatchHandle,
  IN     CONST VOID                                *RegisterContext,
  IN OUT VOID                                      *CommBuffer,
  IN OUT UINTN                                     *CommBufferSize
  )
{
  EFI_STATUS                                       Status;
  SMM_VARIABLE_COMMUNICATE_HEADER                  *SmmVariableFunctionHeader;
  SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE         *SmmVariableHeader;
  SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME  *GetNextVariableName;
  SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO     *QueryVariableInfo;
  SMM_VARIABLE_COMMUNICATE_GET_PAYLOAD_SIZE        *GetPayloadSize;
  VARIABLE_INFO_ENTRY                              *VariableInfo;
  SMM_VARIABLE_COMMUNICATE_LOCK_VARIABLE           *VariableToLock;
  SMM_VARIABLE_COMMUNICATE_VAR_CHECK_VARIABLE_PROPERTY *CommVariableProperty;
  UINTN                                            InfoSize;
  UINTN                                            NameBufferSize;
  UINTN                                            CommBufferPayloadSize;
  UINTN                                            TempCommBufferSize;

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

  TempCommBufferSize = *CommBufferSize;

  if (TempCommBufferSize < SMM_VARIABLE_COMMUNICATE_HEADER_SIZE) {
    DEBUG ((EFI_D_ERROR, "SmmVariableHandler: SMM communication buffer size invalid!\n"));
    return EFI_SUCCESS;
  }
  CommBufferPayloadSize = TempCommBufferSize - SMM_VARIABLE_COMMUNICATE_HEADER_SIZE;
  if (CommBufferPayloadSize > mVariableBufferPayloadSize) {
    DEBUG ((EFI_D_ERROR, "SmmVariableHandler: SMM communication buffer payload size invalid!\n"));
    return EFI_SUCCESS;
  }

  if (!SmmIsBufferOutsideSmmValid ((UINTN)CommBuffer, TempCommBufferSize)) {
    DEBUG ((EFI_D_ERROR, "SmmVariableHandler: SMM communication buffer in SMRAM or overflow!\n"));
    return EFI_SUCCESS;
  }

  SmmVariableFunctionHeader = (SMM_VARIABLE_COMMUNICATE_HEADER *)CommBuffer;
  switch (SmmVariableFunctionHeader->Function) {
    case SMM_VARIABLE_FUNCTION_GET_VARIABLE:
      if (CommBufferPayloadSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name)) {
        DEBUG ((EFI_D_ERROR, "GetVariable: SMM communication buffer size invalid!\n"));
        return EFI_SUCCESS;
      }
      //
      // Copy the input communicate buffer payload to pre-allocated SMM variable buffer payload.
      //
      CopyMem (mVariableBufferPayload, SmmVariableFunctionHeader->Data, CommBufferPayloadSize);
      SmmVariableHeader = (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE *) mVariableBufferPayload;
      if (((UINTN)(~0) - SmmVariableHeader->DataSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name)) ||
         ((UINTN)(~0) - SmmVariableHeader->NameSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) + SmmVariableHeader->DataSize)) {
        //
        // Prevent InfoSize overflow happen
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }
      InfoSize = OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name)
                 + SmmVariableHeader->DataSize + SmmVariableHeader->NameSize;

      //
      // SMRAM range check already covered before
      //
      if (InfoSize > CommBufferPayloadSize) {
        DEBUG ((EFI_D_ERROR, "GetVariable: Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      if (SmmVariableHeader->NameSize < sizeof (CHAR16) || SmmVariableHeader->Name[SmmVariableHeader->NameSize/sizeof (CHAR16) - 1] != L'\0') {
        //
        // Make sure VariableName is A Null-terminated string.
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = VariableServiceGetVariable (
                 SmmVariableHeader->Name,
                 &SmmVariableHeader->Guid,
                 &SmmVariableHeader->Attributes,
                 &SmmVariableHeader->DataSize,
                 (UINT8 *)SmmVariableHeader->Name + SmmVariableHeader->NameSize
                 );
      CopyMem (SmmVariableFunctionHeader->Data, mVariableBufferPayload, CommBufferPayloadSize);
      break;

    case SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME:
      if (CommBufferPayloadSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name)) {
        DEBUG ((EFI_D_ERROR, "GetNextVariableName: SMM communication buffer size invalid!\n"));
        return EFI_SUCCESS;
      }
      //
      // Copy the input communicate buffer payload to pre-allocated SMM variable buffer payload.
      //
      CopyMem (mVariableBufferPayload, SmmVariableFunctionHeader->Data, CommBufferPayloadSize);
      GetNextVariableName = (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME *) mVariableBufferPayload;
      if ((UINTN)(~0) - GetNextVariableName->NameSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name)) {
        //
        // Prevent InfoSize overflow happen
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }
      InfoSize = OFFSET_OF(SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name) + GetNextVariableName->NameSize;

      //
      // SMRAM range check already covered before
      //
      if (InfoSize > CommBufferPayloadSize) {
        DEBUG ((EFI_D_ERROR, "GetNextVariableName: Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      NameBufferSize = CommBufferPayloadSize - OFFSET_OF(SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name);
      if (NameBufferSize < sizeof (CHAR16) || GetNextVariableName->Name[NameBufferSize/sizeof (CHAR16) - 1] != L'\0') {
        //
        // Make sure input VariableName is A Null-terminated string.
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = VariableServiceGetNextVariableName (
                 &GetNextVariableName->NameSize,
                 GetNextVariableName->Name,
                 &GetNextVariableName->Guid
                 );
      CopyMem (SmmVariableFunctionHeader->Data, mVariableBufferPayload, CommBufferPayloadSize);
      break;

    case SMM_VARIABLE_FUNCTION_SET_VARIABLE:
      if (CommBufferPayloadSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name)) {
        DEBUG ((EFI_D_ERROR, "SetVariable: SMM communication buffer size invalid!\n"));
        return EFI_SUCCESS;
      }
      //
      // Copy the input communicate buffer payload to pre-allocated SMM variable buffer payload.
      //
      CopyMem (mVariableBufferPayload, SmmVariableFunctionHeader->Data, CommBufferPayloadSize);
      SmmVariableHeader = (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE *) mVariableBufferPayload;
      if (((UINTN)(~0) - SmmVariableHeader->DataSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name)) ||
         ((UINTN)(~0) - SmmVariableHeader->NameSize < OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) + SmmVariableHeader->DataSize)) {
        //
        // Prevent InfoSize overflow happen
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }
      InfoSize = OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name)
                 + SmmVariableHeader->DataSize + SmmVariableHeader->NameSize;

      //
      // SMRAM range check already covered before
      // Data buffer should not contain SMM range
      //
      if (InfoSize > CommBufferPayloadSize) {
        DEBUG ((EFI_D_ERROR, "SetVariable: Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      if (SmmVariableHeader->NameSize < sizeof (CHAR16) || SmmVariableHeader->Name[SmmVariableHeader->NameSize/sizeof (CHAR16) - 1] != L'\0') {
        //
        // Make sure VariableName is A Null-terminated string.
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = VariableServiceSetVariable (
                 SmmVariableHeader->Name,
                 &SmmVariableHeader->Guid,
                 SmmVariableHeader->Attributes,
                 SmmVariableHeader->DataSize,
                 (UINT8 *)SmmVariableHeader->Name + SmmVariableHeader->NameSize
                 );
      break;

    case SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO:
      if (CommBufferPayloadSize < sizeof (SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO)) {
        DEBUG ((EFI_D_ERROR, "QueryVariableInfo: SMM communication buffer size invalid!\n"));
        return EFI_SUCCESS;
      }
      QueryVariableInfo = (SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO *) SmmVariableFunctionHeader->Data;

      Status = VariableServiceQueryVariableInfo (
                 QueryVariableInfo->Attributes,
                 &QueryVariableInfo->MaximumVariableStorageSize,
                 &QueryVariableInfo->RemainingVariableStorageSize,
                 &QueryVariableInfo->MaximumVariableSize
                 );
      break;

    case SMM_VARIABLE_FUNCTION_GET_PAYLOAD_SIZE:
      if (CommBufferPayloadSize < sizeof (SMM_VARIABLE_COMMUNICATE_GET_PAYLOAD_SIZE)) {
        DEBUG ((EFI_D_ERROR, "GetPayloadSize: SMM communication buffer size invalid!\n"));
        return EFI_SUCCESS;
      }
      GetPayloadSize = (SMM_VARIABLE_COMMUNICATE_GET_PAYLOAD_SIZE *) SmmVariableFunctionHeader->Data;
      GetPayloadSize->VariablePayloadSize = mVariableBufferPayloadSize;
      Status = EFI_SUCCESS;
      break;

    case SMM_VARIABLE_FUNCTION_READY_TO_BOOT:
      mEndOfDxe = TRUE;
      //
      // The initialization for variable quota.
      //
      InitializeVariableQuota ();
      if (AtRuntime()) {
        Status = EFI_UNSUPPORTED;
        break;
      }
      ReclaimForOS ();
      Status = EFI_SUCCESS;
      break;

    case SMM_VARIABLE_FUNCTION_EXIT_BOOT_SERVICE:
      mAtRuntime = TRUE;
      Status = EFI_SUCCESS;
      break;

    case SMM_VARIABLE_FUNCTION_GET_STATISTICS:
      VariableInfo = (VARIABLE_INFO_ENTRY *) SmmVariableFunctionHeader->Data;
      InfoSize = TempCommBufferSize - SMM_VARIABLE_COMMUNICATE_HEADER_SIZE;

      //
      // Do not need to check SmmVariableFunctionHeader->Data in SMRAM here.
      // It is covered by previous CommBuffer check
      //

      if (!SmmIsBufferOutsideSmmValid ((EFI_PHYSICAL_ADDRESS)(UINTN)CommBufferSize, sizeof(UINTN))) {
        DEBUG ((EFI_D_ERROR, "GetStatistics: SMM communication buffer in SMRAM!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = SmmVariableGetStatistics (VariableInfo, &InfoSize);
      *CommBufferSize = InfoSize + SMM_VARIABLE_COMMUNICATE_HEADER_SIZE;
      break;

    case SMM_VARIABLE_FUNCTION_LOCK_VARIABLE:
      if (mEndOfDxe) {
        Status = EFI_ACCESS_DENIED;
      } else {
        VariableToLock = (SMM_VARIABLE_COMMUNICATE_LOCK_VARIABLE *) SmmVariableFunctionHeader->Data;
        Status = VariableLockRequestToLock (
                   NULL,
                   VariableToLock->Name,
                   &VariableToLock->Guid
                   );
      }
      break;
    case SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_SET:
      if (mEndOfDxe) {
        Status = EFI_ACCESS_DENIED;
      } else {
        CommVariableProperty = (SMM_VARIABLE_COMMUNICATE_VAR_CHECK_VARIABLE_PROPERTY *) SmmVariableFunctionHeader->Data;
        Status = VarCheckVariablePropertySet (
                   CommVariableProperty->Name,
                   &CommVariableProperty->Guid,
                   &CommVariableProperty->VariableProperty
                   );
      }
      break;
    case SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_GET:
      if (CommBufferPayloadSize < OFFSET_OF (SMM_VARIABLE_COMMUNICATE_VAR_CHECK_VARIABLE_PROPERTY, Name)) {
        DEBUG ((EFI_D_ERROR, "VarCheckVariablePropertyGet: SMM communication buffer size invalid!\n"));
        return EFI_SUCCESS;
      }
      //
      // Copy the input communicate buffer payload to pre-allocated SMM variable buffer payload.
      //
      CopyMem (mVariableBufferPayload, SmmVariableFunctionHeader->Data, CommBufferPayloadSize);
      CommVariableProperty = (SMM_VARIABLE_COMMUNICATE_VAR_CHECK_VARIABLE_PROPERTY *) mVariableBufferPayload;
      if ((UINTN) (~0) - CommVariableProperty->NameSize < OFFSET_OF (SMM_VARIABLE_COMMUNICATE_VAR_CHECK_VARIABLE_PROPERTY, Name)) {
        //
        // Prevent InfoSize overflow happen
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }
      InfoSize = OFFSET_OF (SMM_VARIABLE_COMMUNICATE_VAR_CHECK_VARIABLE_PROPERTY, Name) + CommVariableProperty->NameSize;

      //
      // SMRAM range check already covered before
      //
      if (InfoSize > CommBufferPayloadSize) {
        DEBUG ((EFI_D_ERROR, "VarCheckVariablePropertyGet: Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      if (CommVariableProperty->NameSize < sizeof (CHAR16) || CommVariableProperty->Name[CommVariableProperty->NameSize/sizeof (CHAR16) - 1] != L'\0') {
        //
        // Make sure VariableName is A Null-terminated string.
        //
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = VarCheckVariablePropertyGet (
                 CommVariableProperty->Name,
                 &CommVariableProperty->Guid,
                 &CommVariableProperty->VariableProperty
                 );
      CopyMem (SmmVariableFunctionHeader->Data, mVariableBufferPayload, CommBufferPayloadSize);
      break;

    default:
      Status = EFI_UNSUPPORTED;
  }

EXIT:

  SmmVariableFunctionHeader->ReturnStatus = Status;

  return EFI_SUCCESS;
}
Example #2
0
/**
  Communication service SMI Handler entry.

  This SMI handler provides services for the variable wrapper driver.

  Caution: This function may receive untrusted input.
  This variable data and communicate buffer are external input, so this function will do basic validation.
  Each sub function VariableServiceGetVariable(), VariableServiceGetNextVariableName(), 
  VariableServiceSetVariable(), VariableServiceQueryVariableInfo(), ReclaimForOS(), 
  SmmVariableGetStatistics() should also do validation based on its own knowledge.

  @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_WARN_INTERRUPT_SOURCE_QUIESCED  The interrupt has been quiesced but other handlers should 
                                              still be called.
  @retval EFI_WARN_INTERRUPT_SOURCE_PENDING   The interrupt is still pending and other handlers should still 
                                              be called.
  @retval EFI_INTERRUPT_PENDING               The interrupt could not be quiesced.

**/
EFI_STATUS
EFIAPI
SmmVariableHandler (
  IN     EFI_HANDLE                                DispatchHandle,
  IN     CONST VOID                                *RegisterContext,
  IN OUT VOID                                      *CommBuffer,
  IN OUT UINTN                                     *CommBufferSize
  )
{
  EFI_STATUS                                       Status;
  SMM_VARIABLE_COMMUNICATE_HEADER                  *SmmVariableFunctionHeader;
  SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE         *SmmVariableHeader;
  SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME  *GetNextVariableName;
  SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO     *QueryVariableInfo;
  VARIABLE_INFO_ENTRY                              *VariableInfo;
  UINTN                                            InfoSize;

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

  if (*CommBufferSize < sizeof(SMM_VARIABLE_COMMUNICATE_HEADER) - 1) {
    return EFI_SUCCESS;
  }

  if (InternalIsAddressInSmram ((EFI_PHYSICAL_ADDRESS)(UINTN)CommBuffer, *CommBufferSize)) {
    DEBUG ((EFI_D_ERROR, "SMM communication buffer size is in SMRAM!\n"));
    return EFI_SUCCESS;
  }
  
  SmmVariableFunctionHeader = (SMM_VARIABLE_COMMUNICATE_HEADER *)CommBuffer;
    
  switch (SmmVariableFunctionHeader->Function) {
    case SMM_VARIABLE_FUNCTION_GET_VARIABLE:
      SmmVariableHeader = (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE *) SmmVariableFunctionHeader->Data;
      InfoSize = OFFSET_OF(SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) 
                 + SmmVariableHeader->DataSize + SmmVariableHeader->NameSize;

      //
      // SMRAM range check already covered before
      //
      if (InfoSize > *CommBufferSize - OFFSET_OF (SMM_VARIABLE_COMMUNICATE_HEADER, Data)) {
        DEBUG ((EFI_D_ERROR, "Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = VariableServiceGetVariable (
                 SmmVariableHeader->Name,
                 &SmmVariableHeader->Guid,
                 &SmmVariableHeader->Attributes,
                 &SmmVariableHeader->DataSize,
                 (UINT8 *)SmmVariableHeader->Name + SmmVariableHeader->NameSize
                 );
      break;
      
    case SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME:
      GetNextVariableName = (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME *) SmmVariableFunctionHeader->Data;
      InfoSize = OFFSET_OF(SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name) + GetNextVariableName->NameSize;

      //
      // SMRAM range check already covered before
      //
      if (InfoSize > *CommBufferSize - OFFSET_OF (SMM_VARIABLE_COMMUNICATE_HEADER, Data)) {
        DEBUG ((EFI_D_ERROR, "Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }

      Status = VariableServiceGetNextVariableName (
                 &GetNextVariableName->NameSize,
                 GetNextVariableName->Name,
                 &GetNextVariableName->Guid
                 );
      break;
      
    case SMM_VARIABLE_FUNCTION_SET_VARIABLE:
      SmmVariableHeader = (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE *) SmmVariableFunctionHeader->Data;
      Status = VariableServiceSetVariable (
                 SmmVariableHeader->Name,
                 &SmmVariableHeader->Guid,
                 SmmVariableHeader->Attributes,
                 SmmVariableHeader->DataSize,
                 (UINT8 *)SmmVariableHeader->Name + SmmVariableHeader->NameSize
                 );
      break;
      
    case SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO:
      QueryVariableInfo = (SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO *) SmmVariableFunctionHeader->Data;
      InfoSize = sizeof(SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO);

      //
      // SMRAM range check already covered before
      //
      if (InfoSize > *CommBufferSize - OFFSET_OF (SMM_VARIABLE_COMMUNICATE_HEADER, Data)) {
        DEBUG ((EFI_D_ERROR, "Data size exceed communication buffer size limit!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }
  
      Status = VariableServiceQueryVariableInfo (
                 QueryVariableInfo->Attributes,
                 &QueryVariableInfo->MaximumVariableStorageSize,
                 &QueryVariableInfo->RemainingVariableStorageSize,
                 &QueryVariableInfo->MaximumVariableSize
                 );
      break;

    case SMM_VARIABLE_FUNCTION_READY_TO_BOOT:
      if (AtRuntime()) {
        Status = EFI_UNSUPPORTED;
        break;
      }
      ReclaimForOS ();
      Status = EFI_SUCCESS;
      break;
  
    case SMM_VARIABLE_FUNCTION_EXIT_BOOT_SERVICE:
      mAtRuntime = TRUE;
      Status = EFI_SUCCESS;
      break;

    case SMM_VARIABLE_FUNCTION_GET_STATISTICS:
      VariableInfo = (VARIABLE_INFO_ENTRY *) SmmVariableFunctionHeader->Data;
      InfoSize = *CommBufferSize - OFFSET_OF (SMM_VARIABLE_COMMUNICATE_HEADER, Data);

      //
      // Do not need to check SmmVariableFunctionHeader->Data in SMRAM here. 
      // It is covered by previous CommBuffer check 
      //
     
      if (InternalIsAddressInSmram ((EFI_PHYSICAL_ADDRESS)(UINTN)CommBufferSize, sizeof(UINTN))) {
        DEBUG ((EFI_D_ERROR, "SMM communication buffer size is in SMRAM!\n"));
        Status = EFI_ACCESS_DENIED;
        goto EXIT;
      }  

      Status = SmmVariableGetStatistics (VariableInfo, &InfoSize);
      *CommBufferSize = InfoSize + OFFSET_OF (SMM_VARIABLE_COMMUNICATE_HEADER, Data);
      break;

    default:
      Status = EFI_UNSUPPORTED;
  }

EXIT:

  SmmVariableFunctionHeader->ReturnStatus = Status;
  return EFI_SUCCESS;
}