monotoniccounter.c

来自「EFI BIOS是Intel提出的下一代的BIOS标准。这里上传的Edk源代码是」· C语言 代码 · 共 292 行

/*++

Copyright (c) 2006, Intel Corporation                                                         
All rights reserved. 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.             

Module Name:

  MonotonicCounter.c

Abstract:

  Produced the Monotonic Counter Services as defined in the DXE CIS

Revision History:

--*/

#include "MonotonicCounter.h"

//
// The Monotonic Counter Handle
//
EFI_HANDLE  mMonotonicCounterHandle = NULL;

//
// The current Monotonic count value
//
UINT64      mEfiMtc = 0xFFFFFFFFFFFFFFFF;

//
// Event to use to update the Mtc's high part when wrapping
//
EFI_EVENT   mEfiMtcEvent;

//
// EfiMtcName - Variable name of the MTC value
//
CHAR16      *mEfiMtcName = L"MTC";

//
// EfiMtcGuid - Guid of the MTC value
//
EFI_GUID    mEfiMtcGuid = { 0xeb704011, 0x1402, 0x11d3, 0x8e, 0x77, 0x0, 0xa0, 0xc9, 0x69, 0x72, 0x3b };

//
// Worker functions
//
EFI_BOOTSERVICE
EFI_STATUS
EFIAPI
MonotonicCounterDriverGetNextMonotonicCount (
  OUT UINT64  *Count
  )
/*++

Routine Description:
  Increase low 32bits. Increase high 32bits and clear low 32bits if overflow.

Arguments:
  Count - return the increased total 64 bits

Returns:

--*/
{
  EFI_TPL     OldTpl;
  UINT32      HighCount;
  UINTN       BufferSize;
  EFI_STATUS  Status;

  //
  // Can not be called after ExitBootServices()
  //
  if (EfiAtRuntime ()) {
    return EFI_UNSUPPORTED;
  }
  //
  // Check input parameters
  //
  if (Count == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Read the last high part
  //
  BufferSize = sizeof (UINT32);
  Status = EfiGetVariable (
             mEfiMtcName,
             &mEfiMtcGuid,
             NULL,
             &BufferSize,
             &HighCount
             );
  if (EFI_ERROR (Status)) {
    HighCount = 0;
  }

  //
  // There is four reasons cause change of high 32bits of MTC
  // 1. It's first call to GetNextMTC
  // 2. Real NV is started, and MTC is patched
  // 3. GetNextHighMTC is called by user
  // 4. low 32bits overflow
  // of these, only the reason 1&2 can cause the difference between high 32bits of mEfiMtc and HighCount
  //
  if ((UINT32) RShiftU64 (mEfiMtc, 32) != HighCount) {
    mEfiMtc = LShiftU64 (HighCount, 32);
  }
  
  //
  // Update the monotonic counter with a lock
  //
  OldTpl  = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
  *Count  = mEfiMtc;
  mEfiMtc++;
  gBS->RestoreTPL (OldTpl);

  //
  // If the MSB bit of the low part toggled, then signal that the high
  // part needs updated now
  //
  if ((((UINT32) mEfiMtc) ^ ((UINT32) *Count)) & 0x80000000) {
    gBS->SignalEvent (mEfiMtcEvent);
  }

  return EFI_SUCCESS;
}

EFI_RUNTIMESERVICE
EFI_STATUS
EFIAPI
MonotonicCounterDriverGetNextHighMonotonicCount (
  OUT UINT32  *HighCount
  )
/*++

Routine Description:
  Increase high 32bits and clear low 32bits.

Arguments:
  HighCount - return the increased high 32bits
Returns:

--*/
{
  EFI_STATUS  Status;
  EFI_TPL     OldTpl;
  UINTN       BufferSize;

  //
  // Check input parameters
  //
  if (HighCount == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Read the last high part
  //
  BufferSize = sizeof (UINT32);
  Status = EfiGetVariable (
             mEfiMtcName,
             &mEfiMtcGuid,
             NULL,
             &BufferSize,
             HighCount
             );
  if (EFI_ERROR (Status)) {
    *HighCount = 0;
  }

  if (!EfiAtRuntime ()) {
    OldTpl      = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
    *HighCount += 1;
    mEfiMtc     = LShiftU64 (*HighCount, 32);
    gBS->RestoreTPL (OldTpl);
  } else {
    *HighCount += 1;
    mEfiMtc     = LShiftU64 (*HighCount, 32);
  }
  //
  // Update the NvRam store to match the new high part
  //
  Status = EfiSetVariable (
             mEfiMtcName,
             &mEfiMtcGuid,
             EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS,
             sizeof (UINT32),
             HighCount
             );

  return Status;
}

EFI_STATUS
EFIAPI
EfiMtcEventHandler (
  IN EFI_EVENT                Event,
  IN VOID                     *Context
  )
/*++

Routine Description:

  Monotonic count event handler.  This handler updates the high monotonic count.

Arguments:

  Event         The event to handle
  Context       The event context

Returns:

  EFI_SUCCESS       The event has been handled properly 
  EFI_NOT_FOUND     An error occurred updating the variable.

--*/
{
  UINT32  HighCount;

  return MonotonicCounterDriverGetNextHighMonotonicCount (&HighCount);
}

EFI_DRIVER_ENTRY_POINT (MonotonicCounterDriverInitialize)

EFI_STATUS
EFIAPI
MonotonicCounterDriverInitialize (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
/*++

Routine Description:

Arguments:
  (Standard EFI Image entry - EFI_IMAGE_ENTRY_POINT)

Returns:

--*/
{
  EFI_STATUS  Status;

  EfiInitializeRuntimeDriverLib (ImageHandle, SystemTable, NULL);

  //
  // Make sure the Monotonic Counter Architectural Protocol is not already installed in the system
  //
  ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiMonotonicCounterArchProtocolGuid);

  //
  // Initialize event to handle overflows
  //
  Status = gBS->CreateEvent (
                  EFI_EVENT_NOTIFY_SIGNAL,
                  EFI_TPL_CALLBACK,
                  EfiMtcEventHandler,
                  NULL,
                  &mEfiMtcEvent
                  );
  ASSERT_EFI_ERROR (Status);



  //
  // Fill in the EFI Boot Services and EFI Runtime Services Monotonic Counter Fields
  //
  gBS->GetNextMonotonicCount                      = MonotonicCounterDriverGetNextMonotonicCount;
  gST->RuntimeServices->GetNextHighMonotonicCount = MonotonicCounterDriverGetNextHighMonotonicCount;

  //
  // Install the Monotonic Counter Architctural Protocol onto a new handle
  //
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &mMonotonicCounterHandle,
                  &gEfiMonotonicCounterArchProtocolGuid,
                  NULL,
                  NULL
                  );
  ASSERT_EFI_ERROR (Status);

  return EFI_SUCCESS;
}