audk/SecurityPkg/Tcg/MemoryOverwriteControl/TcgMor.c

/** @file
  TCG MOR (Memory Overwrite Request) Control Driver.

  This driver initilize MemoryOverwriteRequestControl variable. It 
  will clear MOR_CLEAR_MEMORY_BIT bit if it is set.

Copyright (c) 2009 - 2014, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials 
are licensed and made available under the terms and conditions of the BSD License 
which accompanies this distribution.  The full text of the license may be found at 
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include "TcgMor.h"

UINT8    mMorControl;

/**
  Ready to Boot Event notification handler.

  Sequence of OS boot events is measured in this event notification handler.

  @param[in]  Event     Event whose notification function is being invoked
  @param[in]  Context   Pointer to the notification function's context

**/
VOID
EFIAPI
OnReadyToBoot (
  IN      EFI_EVENT                 Event,
  IN      VOID                      *Context
  )
{
  EFI_STATUS  Status;
  UINTN       DataSize;
  
  if (MOR_CLEAR_MEMORY_VALUE (mMorControl) == 0x0) {
    //
    // MorControl is expected, directly return to avoid unnecessary variable operation
    //
    return ;
  }
  //
  // Clear MOR_CLEAR_MEMORY_BIT
  //
  DEBUG ((EFI_D_INFO, "TcgMor: Clear MorClearMemory bit\n"));
  mMorControl &= 0xFE;  

  DataSize = sizeof (mMorControl);
  Status   = gRT->SetVariable (
               MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME, 
               &gEfiMemoryOverwriteControlDataGuid, 
               EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
               DataSize, 
               &mMorControl
               );
  if (EFI_ERROR (Status)) {
    DEBUG ((EFI_D_ERROR, "TcgMor: Clear MOR_CLEAR_MEMORY_BIT failure, Status = %r\n"));
  }
}


/**
  Entry Point for TCG MOR Control driver.

  @param[in] ImageHandle  Image handle of this driver.
  @param[in] SystemTable  A Pointer to the EFI System Table.

  @retval EFI_SUCEESS     
  @return Others          Some error occurs.
**/
EFI_STATUS
EFIAPI
MorDriverEntryPoint (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS  Status;
  UINTN       DataSize;
  EFI_EVENT   Event;

  ///
  /// The firmware is required to create the MemoryOverwriteRequestControl UEFI variable.
  ///

  DataSize = sizeof (mMorControl);
  Status = gRT->GetVariable (
                  MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME, 
                  &gEfiMemoryOverwriteControlDataGuid, 
                  NULL, 
                  &DataSize, 
                  &mMorControl
                  );
  if (EFI_ERROR (Status)) {
    //
    // Set default value to 0
    //
    mMorControl = 0;
    Status = gRT->SetVariable (
                    MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME, 
                    &gEfiMemoryOverwriteControlDataGuid, 
                    EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
                    DataSize, 
                    &mMorControl
                    );
    DEBUG ((EFI_D_INFO, "TcgMor: Create MOR variable! Status = %r\n", Status));
  } else {
    //
    // Create a Ready To Boot Event and Clear the MorControl bit in the call back function.
    //
    DEBUG ((EFI_D_INFO, "TcgMor: Create ReadyToBoot Event for MorControl Bit cleanning!\n"));
    Status = EfiCreateEventReadyToBootEx (
               TPL_CALLBACK,
               OnReadyToBoot,
               NULL,
               &Event
               );
  }    
  
  return Status;
}