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/** @file
Generic Monotonic Counter services
Copyright (c) 2007, Intel Corporation<BR>
Portions copyright (c) 2008-2009, Apple Inc. All rights reserved.
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.
**/
//
// The current Monotonic count value
//
UINT64 mEfiMtc = 0;
//
// 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
//
VOID
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;
EfiGetNextHighMonotonicCount (&HighCount);
return;
}
VOID
LibMtcVirtualAddressChangeEvent (VOID)
{
}
EFI_STATUS
EFIAPI
LibMtcGetNextHighMonotonicCount (
OUT UINT32 *HighCount
)
{
EFI_STATUS Status;
EFI_TPL OldTpl;
//
// Check input parameters
//
if (HighCount == NULL) {
return EFI_INVALID_PARAMETER;
}
if (!EfiAtRuntime ()) {
// Use a lock if called before ExitBootServices()
OldTpl = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
}
*HighCount = (UINT32) RShiftU64 (mEfiMtc, 32) + 1;
mEfiMtc = LShiftU64 (*HighCount, 32);
if (!EfiAtRuntime ()) {
gBS->RestoreTPL (OldTpl);
}
//
// 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
LibMtcGetNextMonotonicCount (
OUT UINT64 *Count
)
{
EFI_STATUS Status;
EFI_TPL OldTpl;
UINT32 HighCount;
UINTN BufferSize;
//
// Can not be called after ExitBootServices()
//
if (EfiAtRuntime ()) {
return EFI_UNSUPPORTED;
}
//
// Check input parameters
//
if (Count == NULL) {
return EFI_INVALID_PARAMETER;
}
if (mEfiMtc == 0) {
//
// If the MTC has not been initialized read the variable
//
//
// Read the last high part
//
BufferSize = sizeof (UINT32);
Status = EfiGetVariable (
mEfiMtcName,
&mEfiMtcGuid,
NULL,
&BufferSize,
&HighCount
);
if (EFI_ERROR (Status)) {
HighCount = 0;
}
//
// Set the current value
//
mEfiMtc = LShiftU64 (HighCount, 32);
//
// Increment the upper 32 bits for this boot
// Continue even if it fails. It will only fail if the variable services are
// not functional.
//
Status = EfiGetNextHighMonotonicCount (&HighCount);
}
//
// 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;
}
VOID
LibMtcInitialize (
VOID
)
{
EFI_STATUS Status;
//
// Initialize event to handle overflows
//
Status = gBS->CreateEvent (
EVT_NOTIFY_SIGNAL,
EFI_TPL_CALLBACK,
EfiMtcEventHandler,
NULL,
&mEfiMtcEvent
);
ASSERT_EFI_ERROR (Status);
}
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