mirror of https://github.com/acidanthera/audk.git
300 lines
7.8 KiB
C
300 lines
7.8 KiB
C
/*++
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Copyright (c) 2006, Intel Corporation
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All rights reserved. This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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Module Name:
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MonotonicCounter.c
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Abstract:
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Produced the Monotonic Counter Services as defined in the DXE CIS
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Revision History:
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--*/
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#include "MonotonicCounter.h"
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//
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// The Monotonic Counter Handle
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//
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EFI_HANDLE mMonotonicCounterHandle = NULL;
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//
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// The current Monotonic count value
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//
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UINT64 mEfiMtc;
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//
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// Event to use to update the Mtc's high part when wrapping
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//
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EFI_EVENT mEfiMtcEvent;
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//
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// EfiMtcName - Variable name of the MTC value
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//
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CHAR16 *mEfiMtcName = (CHAR16 *) L"MTC";
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//
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// EfiMtcGuid - Guid of the MTC value
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//
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EFI_GUID mEfiMtcGuid = { 0xeb704011, 0x1402, 0x11d3, { 0x8e, 0x77, 0x0, 0xa0, 0xc9, 0x69, 0x72, 0x3b } };
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//
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// Worker functions
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//
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STATIC
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EFI_STATUS
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EFIAPI
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MonotonicCounterDriverGetNextMonotonicCount (
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OUT UINT64 *Count
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)
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/*++
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Routine Description:
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Arguments:
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Returns:
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--*/
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{
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EFI_TPL OldTpl;
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//
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// Can not be called after ExitBootServices()
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//
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if (EfiAtRuntime ()) {
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return EFI_UNSUPPORTED;
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}
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//
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// Check input parameters
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//
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if (Count == NULL) {
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return EFI_INVALID_PARAMETER;
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}
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//
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// Update the monotonic counter with a lock
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//
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OldTpl = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
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*Count = mEfiMtc;
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mEfiMtc++;
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gBS->RestoreTPL (OldTpl);
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//
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// If the MSB bit of the low part toggled, then signal that the high
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// part needs updated now
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//
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if ((((UINT32) mEfiMtc) ^ ((UINT32) *Count)) & 0x80000000) {
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gBS->SignalEvent (mEfiMtcEvent);
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}
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return EFI_SUCCESS;
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}
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/**
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Returns the next high 32 bits of the platform's monotonic counter.
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The GetNextHighMonotonicCount() function returns the next high 32 bits
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of the platform's monotonic counter. The platform's monotonic counter is
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comprised of two 32 bit quantities: the high 32 bits and the low 32 bits.
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During boot service time the low 32 bit value is volatile: it is reset to
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zero on every system reset and is increased by 1 on every call to GetNextMonotonicCount().
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The high 32 bit value is non-volatile and is increased by 1 whenever the system resets
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or whenever the low 32 bit count [returned by GetNextMonoticCount()] overflows.
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The GetNextMonotonicCount() function is only available at boot services time.
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If the operating system wishes to extend the platform monotonic counter to runtime,
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it may do so by utilizing GetNextHighMonotonicCount(). To do this, before calling
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ExitBootServices() the operating system would call GetNextMonotonicCount() to obtain
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the current platform monotonic count. The operating system would then provide an
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interface that returns the next count by:
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Adding 1 to the last count.
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Before the lower 32 bits of the count overflows, call GetNextHighMonotonicCount().
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This will increase the high 32 bits of the platform's non-volatile portion of the monotonic
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count by 1.
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This function may only be called at Runtime.
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@param[out] HighCount Pointer to returned value.
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@retval EFI_INVALID_PARAMETER If HighCount is NULL.
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@retval EFI_SUCCESS Operation is successful.
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@retval EFI_OUT_OF_RESOURCES If variable service reports that not enough storage
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is available to hold the variable and its data.
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@retval EFI_DEVICE_ERROR The variable could not be saved due to a hardware failure.
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**/
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STATIC
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EFI_STATUS
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EFIAPI
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MonotonicCounterDriverGetNextHighMonotonicCount (
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OUT UINT32 *HighCount
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)
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/*++
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Routine Description:
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Arguments:
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Returns:
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--*/
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{
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EFI_TPL OldTpl;
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//
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// Check input parameters
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//
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if (HighCount == NULL) {
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return EFI_INVALID_PARAMETER;
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}
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if (!EfiAtRuntime ()) {
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//
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// Use a lock if called before ExitBootServices()
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//
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OldTpl = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
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*HighCount = (UINT32) RShiftU64 (mEfiMtc, 32) + 1;
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mEfiMtc = LShiftU64 (*HighCount, 32);
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gBS->RestoreTPL (OldTpl);
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} else {
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*HighCount = (UINT32) RShiftU64 (mEfiMtc, 32) + 1;
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mEfiMtc = LShiftU64 (*HighCount, 32);
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}
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//
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// Update the NvRam store to match the new high part
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//
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return EfiSetVariable (
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mEfiMtcName,
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&mEfiMtcGuid,
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EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS,
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sizeof (UINT32),
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HighCount
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);
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}
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STATIC
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VOID
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EFIAPI
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EfiMtcEventHandler (
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IN EFI_EVENT Event,
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IN VOID *Context
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)
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/*++
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Routine Description:
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Monotonic count event handler. This handler updates the high monotonic count.
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Arguments:
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Event The event to handle
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Context The event context
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Returns:
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EFI_SUCCESS The event has been handled properly
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EFI_NOT_FOUND An error occurred updating the variable.
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--*/
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{
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UINT32 HighCount;
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MonotonicCounterDriverGetNextHighMonotonicCount (&HighCount);
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}
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EFI_STATUS
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EFIAPI
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MonotonicCounterDriverInitialize (
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IN EFI_HANDLE ImageHandle,
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IN EFI_SYSTEM_TABLE *SystemTable
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)
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/*++
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Routine Description:
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Arguments:
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(Standard EFI Image entry - EFI_IMAGE_ENTRY_POINT)
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Returns:
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--*/
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{
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EFI_STATUS Status;
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UINT32 HighCount;
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UINTN BufferSize;
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//
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// Make sure the Monotonic Counter Architectural Protocol is not already installed in the system
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//
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ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiMonotonicCounterArchProtocolGuid);
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//
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// Initialize event to handle overflows
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//
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Status = gBS->CreateEvent (
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EFI_EVENT_NOTIFY_SIGNAL,
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EFI_TPL_CALLBACK,
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EfiMtcEventHandler,
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NULL,
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&mEfiMtcEvent
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);
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ASSERT_EFI_ERROR (Status);
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//
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// Read the last high part
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//
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BufferSize = sizeof (UINT32);
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Status = gRT->GetVariable (
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mEfiMtcName,
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&mEfiMtcGuid,
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NULL,
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&BufferSize,
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&HighCount
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);
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if (EFI_ERROR (Status)) {
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HighCount = 0;
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}
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//
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// Set the current value
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//
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mEfiMtc = LShiftU64 (HighCount, 32);
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//
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// Increment the upper 32 bits for this boot
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// Continue even if it fails. It will only fail if the variable services are
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// not functional.
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//
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Status = MonotonicCounterDriverGetNextHighMonotonicCount (&HighCount);
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//
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// Fill in the EFI Boot Services and EFI Runtime Services Monotonic Counter Fields
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//
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gBS->GetNextMonotonicCount = MonotonicCounterDriverGetNextMonotonicCount;
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gRT->GetNextHighMonotonicCount = MonotonicCounterDriverGetNextHighMonotonicCount;
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//
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// Install the Monotonic Counter Architctural Protocol onto a new handle
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//
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Status = gBS->InstallMultipleProtocolInterfaces (
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&mMonotonicCounterHandle,
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&gEfiMonotonicCounterArchProtocolGuid,
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NULL,
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NULL
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);
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ASSERT_EFI_ERROR (Status);
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return EFI_SUCCESS;
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}
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