EmbeddedMonotonicCounter.c

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#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;
}