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 - 2012, 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 UINT8    mMorControl;
  21
  22 /**
  23   Ready to Boot Event notification handler.
  24
  25   Sequence of OS boot events is measured in this event notification handler.
  26
  27   @param[in]  Event     Event whose notification function is being invoked
  28   @param[in]  Context   Pointer to the notification function's context
  29
  30 **/
  31 VOID
  32 EFIAPI
  33 OnReadyToBoot (
  34   IN      EFI_EVENT                 Event,
  35   IN      VOID                      *Context
  36   )
  37 {
  38   UINTN       DataSize;
  39
  40   if (MOR_CLEAR_MEMORY_VALUE (mMorControl) == 0x0) {
  41     //
  42     // MorControl is expected, directly return to avoid unnecessary variable operation
  43     //
  44     return ;
  45   }
  46   //
  47   // Clear MOR_CLEAR_MEMORY_BIT
  48   //
  49   DEBUG ((EFI_D_INFO, "TcgMor: Clear MorClearMemory bit\n"));
  50   mMorControl &= 0xFE;
  51
  52   DataSize = sizeof (mMorControl);
  53   gRT->SetVariable (
  54          MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
  55          &gEfiMemoryOverwriteControlDataGuid,
  56          EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
  57          DataSize,
  58          &mMorControl
  59          );
  60
  61 }
  62
  63
  64 /**
  65   Entry Point for TCG MOR Control driver.
  66
  67   @param[in] ImageHandle  Image handle of this driver.
  68   @param[in] SystemTable  A Pointer to the EFI System Table.
  69
  70   @retval EFI_SUCEESS
  71   @return Others          Some error occurs.
  72 **/
  73 EFI_STATUS
  74 EFIAPI
  75 MorDriverEntryPoint (
  76   IN EFI_HANDLE        ImageHandle,
  77   IN EFI_SYSTEM_TABLE  *SystemTable
  78   )
  79 {
  80   EFI_STATUS  Status;
  81   UINTN       DataSize;
  82   EFI_EVENT   Event;
  83
  84   ///
  85   /// The firmware is required to create the MemoryOverwriteRequestControl UEFI variable.
  86   ///
  87
  88   DataSize = sizeof (mMorControl);
  89   Status = gRT->GetVariable (
  90                   MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
  91                   &gEfiMemoryOverwriteControlDataGuid,
  92                   NULL,
  93                   &DataSize,
  94                   &mMorControl
  95                   );
  96   if (EFI_ERROR (Status)) {
  97     //
  98     // Set default value to 0
  99     //
 100     mMorControl = 0;
 101     DEBUG ((EFI_D_INFO, "TcgMor: Create gEfiMemoryOverwriteControlDataGuid!\n"));
 102     Status = gRT->SetVariable (
 103                     MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
 104                     &gEfiMemoryOverwriteControlDataGuid,
 105                     EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
 106                     DataSize,
 107                     &mMorControl
 108                     );
 109     ASSERT_EFI_ERROR (Status);
 110
 111   } else {
 112     //
 113     // Create a Ready To Boot Event and Clear the MorControl bit in the call back function.
 114     //
 115     DEBUG ((EFI_D_INFO, "TcgMor: Create ReadyToBoot Event for MorControl Bit cleanning!\n"));
 116     Status = EfiCreateEventReadyToBootEx (
 117                TPL_CALLBACK,
 118                OnReadyToBoot,
 119                NULL,
 120                &Event
 121                );
 122   }
 123
 124   return Status;
 125 }
 126
 127