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 - 2014, 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   EFI_STATUS  Status;
  39   UINTN       DataSize;
  40
  41   if (MOR_CLEAR_MEMORY_VALUE (mMorControl) == 0x0) {
  42     //
  43     // MorControl is expected, directly return to avoid unnecessary variable operation
  44     //
  45     return ;
  46   }
  47   //
  48   // Clear MOR_CLEAR_MEMORY_BIT
  49   //
  50   DEBUG ((EFI_D_INFO, "TcgMor: Clear MorClearMemory bit\n"));
  51   mMorControl &= 0xFE;
  52
  53   DataSize = sizeof (mMorControl);
  54   Status   = gRT->SetVariable (
  55                MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
  56                &gEfiMemoryOverwriteControlDataGuid,
  57                EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
  58                DataSize,
  59                &mMorControl
  60                );
  61   if (EFI_ERROR (Status)) {
  62     DEBUG ((EFI_D_ERROR, "TcgMor: Clear MOR_CLEAR_MEMORY_BIT failure, Status = %r\n"));
  63   }
  64 }
  65
  66
  67 /**
  68   Entry Point for TCG MOR Control driver.
  69
  70   @param[in] ImageHandle  Image handle of this driver.
  71   @param[in] SystemTable  A Pointer to the EFI System Table.
  72
  73   @retval EFI_SUCEESS
  74   @return Others          Some error occurs.
  75 **/
  76 EFI_STATUS
  77 EFIAPI
  78 MorDriverEntryPoint (
  79   IN EFI_HANDLE        ImageHandle,
  80   IN EFI_SYSTEM_TABLE  *SystemTable
  81   )
  82 {
  83   EFI_STATUS  Status;
  84   UINTN       DataSize;
  85   EFI_EVENT   Event;
  86
  87   ///
  88   /// The firmware is required to create the MemoryOverwriteRequestControl UEFI variable.
  89   ///
  90
  91   DataSize = sizeof (mMorControl);
  92   Status = gRT->GetVariable (
  93                   MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
  94                   &gEfiMemoryOverwriteControlDataGuid,
  95                   NULL,
  96                   &DataSize,
  97                   &mMorControl
  98                   );
  99   if (EFI_ERROR (Status)) {
 100     //
 101     // Set default value to 0
 102     //
 103     mMorControl = 0;
 104     Status = gRT->SetVariable (
 105                     MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
 106                     &gEfiMemoryOverwriteControlDataGuid,
 107                     EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
 108                     DataSize,
 109                     &mMorControl
 110                     );
 111     DEBUG ((EFI_D_INFO, "TcgMor: Create MOR variable! Status = %r\n", Status));
 112   } else {
 113     //
 114     // Create a Ready To Boot Event and Clear the MorControl bit in the call back function.
 115     //
 116     DEBUG ((EFI_D_INFO, "TcgMor: Create ReadyToBoot Event for MorControl Bit cleanning!\n"));
 117     Status = EfiCreateEventReadyToBootEx (
 118                TPL_CALLBACK,
 119                OnReadyToBoot,
 120                NULL,
 121                &Event
 122                );
 123   }
 124
 125   return Status;
 126 }
 127
 128