EmbeddedPkg/EmbeddedMonotonicCounter/EmbeddedMonotonicCounter.c

/** @file

  Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Uefi.h>

#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>

#include <Protocol/MonotonicCounter.h>

UINT64  gCurrentMonotonicCount = 0;

EFI_STATUS
EFIAPI
GetNextMonotonicCount (
  OUT UINT64  *Count
  )
{
  if (Count == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  *Count = gCurrentMonotonicCount++;
  return EFI_SUCCESS;
}

EFI_STATUS
EFIAPI
GetNextHighMonotonicCount (
  OUT UINT32  *HighCount
  )
{
  if (HighCount == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  gCurrentMonotonicCount += 0x0000000100000000ULL;

  *HighCount = (UINT32)RShiftU64 (gCurrentMonotonicCount, 32) & 0xFFFFFFFF;

  return EFI_SUCCESS;
}

EFI_STATUS
EFIAPI
MonotonicCounterDriverInitialize (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS  Status;
  EFI_HANDLE  Handle = NULL;

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

  // Fill in the EFI Boot Services and EFI Runtime Services Monotonic Counter Fields
  gBS->GetNextMonotonicCount     = GetNextMonotonicCount;
  gRT->GetNextHighMonotonicCount = GetNextHighMonotonicCount;

  // Install the Monotonic Counter Architectural Protocol onto a new handle
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &Handle,
                  &gEfiMonotonicCounterArchProtocolGuid,
                  NULL,
                  NULL
                  );
  return Status;
}