SecurityPkg/Tcg/MemoryOverwriteControl/TcgMor.c

   1 /** @file
   2   TCG MOR (Memory Overwrite Request) Control Driver.
   3
   4   This driver initilize MemoryOverwriteRequestControl variable. It
   5   will clear MOR_CLEAR_MEMORY_BIT bit if it is set.
   6
   7 Copyright (c) 2009 - 2011, Intel Corporation. All rights reserved.<BR>
   8 This program and the accompanying materials
   9 are licensed and made available under the terms and conditions of the BSD License
  10 which accompanies this distribution.  The full text of the license may be found at
  11 http://opensource.org/licenses/bsd-license.php
  12
  13 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  14 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  15
  16 **/
  17
  18 #include "TcgMor.h"
  19
  20 /**
  21   Entry Point for TCG MOR Control driver.
  22
  23   @param[in] ImageHandle  Image handle of this driver.
  24   @param[in] SystemTable  A Pointer to the EFI System Table.
  25
  26   @retval EFI_SUCEESS
  27   @return Others          Some error occurs.
  28 **/
  29 EFI_STATUS
  30 EFIAPI
  31 MorDriverEntryPoint (
  32   IN EFI_HANDLE        ImageHandle,
  33   IN EFI_SYSTEM_TABLE  *SystemTable
  34   )
  35 {
  36   EFI_STATUS  Status;
  37   UINT8       MorControl;
  38   UINTN       DataSize;
  39
  40   ///
  41   /// The firmware is required to create the MemoryOverwriteRequestControl UEFI variable.
  42   ///
  43
  44   DataSize = sizeof (MorControl);
  45   Status = gRT->GetVariable (
  46                   MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
  47                   &gEfiMemoryOverwriteControlDataGuid,
  48                   NULL,
  49                   &DataSize,
  50                   &MorControl
  51                   );
  52   if (EFI_ERROR (Status)) {
  53     //
  54     // Set default value to 0
  55     //
  56     MorControl = 0;
  57   } else {
  58     if (MOR_CLEAR_MEMORY_VALUE (MorControl) == 0x0) {
  59       //
  60       // MorControl is expected, directly return to avoid unnecessary variable operation
  61       //
  62       return EFI_SUCCESS;
  63     }
  64     //
  65     // Clear MOR_CLEAR_MEMORY_BIT
  66     //
  67     DEBUG ((EFI_D_INFO, "TcgMor: Clear MorClearMemory bit\n"));
  68     MorControl &= 0xFE;
  69   }
  70
  71   Status = gRT->SetVariable (
  72                   MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
  73                   &gEfiMemoryOverwriteControlDataGuid,
  74                   EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
  75                   DataSize,
  76                   &MorControl
  77                   );
  78   ASSERT_EFI_ERROR (Status);
  79   return Status;
  80 }
  81
  82