2 Produce the UEFI boot service GetNextMonotonicCount() and runtime service
3 GetNextHighMonotonicCount().
5 Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
6 This program and the accompanying materials
7 are licensed and made available under the terms and conditions of the BSD License
8 which accompanies this distribution. The full text of the license may be found at
9 http://opensource.org/licenses/bsd-license.php
11 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
12 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
18 #include <Protocol/MonotonicCounter.h>
19 #include <Guid/MtcVendor.h>
21 #include <Library/BaseLib.h>
22 #include <Library/UefiDriverEntryPoint.h>
23 #include <Library/UefiRuntimeLib.h>
24 #include <Library/DebugLib.h>
25 #include <Library/UefiBootServicesTableLib.h>
26 #include <Library/UefiRuntimeServicesTableLib.h>
29 // The handle to install Monotonic Counter Architctural Protocol
31 EFI_HANDLE mMonotonicCounterHandle
= NULL
;
34 // The current monotonic counter value
39 // Event to update the monotonic Counter's high part when low part overflows.
41 EFI_EVENT mEfiMtcEvent
;
44 Returns a monotonically increasing count for the platform.
46 This function returns a 64-bit value that is numerically larger then the last
47 time the function was called.
48 The platform monotonic counter is comprised of two parts: the high 32 bits
49 and the low 32 bits. The low 32-bit value is volatile and is reset to zero on
50 every system reset. It is increased by 1 on every call to GetNextMonotonicCount().
51 The high 32-bit value is nonvolatile and is increased by one on whenever the
52 system resets or the low 32-bit counter overflows.
54 @param Count Pointer to returned value.
56 @retval EFI_SUCCESS The next monotonic count was returned.
57 @retval EFI_DEVICE_ERROR The device is not functioning properly.
58 @retval EFI_INVALID_PARAMETER Count is NULL.
59 @retval EFI_UNSUPPORTED This function is called at runtime.
64 MonotonicCounterDriverGetNextMonotonicCount (
71 // Cannot be called after ExitBootServices()
73 if (EfiAtRuntime ()) {
74 return EFI_UNSUPPORTED
;
77 // Check input parameters
80 return EFI_INVALID_PARAMETER
;
83 // Update the monotonic counter with a lock
85 OldTpl
= gBS
->RaiseTPL (TPL_HIGH_LEVEL
);
88 gBS
->RestoreTPL (OldTpl
);
91 // If the low 32-bit counter overflows (MSB bit toggled),
92 // then signal that the high part needs update now.
94 if ((((UINT32
) mEfiMtc
) ^ ((UINT32
) *Count
)) & BIT31
) {
95 gBS
->SignalEvent (mEfiMtcEvent
);
103 Returns the next high 32 bits of the platform's monotonic counter.
105 The GetNextHighMonotonicCount() function returns the next high 32 bits
106 of the platform's monotonic counter. The platform's monotonic counter is
107 comprised of two 32 bit quantities: the high 32 bits and the low 32 bits.
108 During boot service time the low 32 bit value is volatile: it is reset to
109 zero on every system reset and is increased by 1 on every call to GetNextMonotonicCount().
110 The high 32 bit value is non-volatile and is increased by 1 whenever the system resets,
111 whenever GetNextHighMonotonicCount() is called, or whenever the low 32 bit count
112 (returned by GetNextMonoticCount()) overflows.
113 The GetNextMonotonicCount() function is only available at boot services time.
114 If the operating system wishes to extend the platform monotonic counter to runtime,
115 it may do so by utilizing GetNextHighMonotonicCount(). To do this, before calling
116 ExitBootServices() the operating system would call GetNextMonotonicCount() to obtain
117 the current platform monotonic count. The operating system would then provide an
118 interface that returns the next count by:
119 Adding 1 to the last count.
120 Before the lower 32 bits of the count overflows, call GetNextHighMonotonicCount().
121 This will increase the high 32 bits of the platform's non-volatile portion of the monotonic
124 This function may only be called at Runtime.
126 @param HighCount Pointer to returned value.
128 @retval EFI_SUCCESS The next high monotonic count was returned.
129 @retval EFI_INVALID_PARAMETER HighCount is NULL.
130 @retval EFI_DEVICE_ERROR The variable could not be saved due to a hardware failure.
131 @retval EFI_OUT_OF_RESOURCES If variable service reports that not enough storage
132 is available to hold the variable and its data.
137 MonotonicCounterDriverGetNextHighMonotonicCount (
138 OUT UINT32
*HighCount
144 // Check input parameters
146 if (HighCount
== NULL
) {
147 return EFI_INVALID_PARAMETER
;
150 if (!EfiAtRuntime ()) {
152 // Use a lock if called before ExitBootServices()
154 OldTpl
= gBS
->RaiseTPL (TPL_HIGH_LEVEL
);
155 *HighCount
= (UINT32
) RShiftU64 (mEfiMtc
, 32) + 1;
156 mEfiMtc
= LShiftU64 (*HighCount
, 32);
157 gBS
->RestoreTPL (OldTpl
);
159 *HighCount
= (UINT32
) RShiftU64 (mEfiMtc
, 32) + 1;
160 mEfiMtc
= LShiftU64 (*HighCount
, 32);
163 // Update the NV variable to match the new high part
165 return EfiSetVariable (
168 EFI_VARIABLE_NON_VOLATILE
| EFI_VARIABLE_RUNTIME_ACCESS
| EFI_VARIABLE_BOOTSERVICE_ACCESS
,
176 Monotonic counter event handler. This handler updates the high part of monotonic counter.
178 @param Event The event to handle.
179 @param Context The event context.
191 MonotonicCounterDriverGetNextHighMonotonicCount (&HighCount
);
195 Entry point of monotonic counter driver.
197 @param ImageHandle The image handle of this driver.
198 @param SystemTable The pointer of EFI_SYSTEM_TABLE.
200 @retval EFI_SUCCESS The initialization is successful.
205 MonotonicCounterDriverInitialize (
206 IN EFI_HANDLE ImageHandle
,
207 IN EFI_SYSTEM_TABLE
*SystemTable
215 // Make sure the Monotonic Counter Architectural Protocol has not been installed in the system yet.
217 ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL
, &gEfiMonotonicCounterArchProtocolGuid
);
220 // Initialize event to handle low-part overflow
222 Status
= gBS
->CreateEvent (
229 ASSERT_EFI_ERROR (Status
);
232 // Read the last high part
234 BufferSize
= sizeof (UINT32
);
235 Status
= EfiGetVariable (
242 if (EFI_ERROR (Status
)) {
246 // Set the current value
248 mEfiMtc
= LShiftU64 (HighCount
, 32);
251 // Increment the upper 32 bits for this boot
252 // Continue even if it fails. It will only fail if the variable services are
255 MonotonicCounterDriverGetNextHighMonotonicCount (&HighCount
);
258 // Fill in the EFI Boot Services and EFI Runtime Services Monotonic Counter Fields
260 gBS
->GetNextMonotonicCount
= MonotonicCounterDriverGetNextMonotonicCount
;
261 gRT
->GetNextHighMonotonicCount
= MonotonicCounterDriverGetNextHighMonotonicCount
;
264 // Install the Monotonic Counter Architctural Protocol onto a new handle
266 Status
= gBS
->InstallMultipleProtocolInterfaces (
267 &mMonotonicCounterHandle
,
268 &gEfiMonotonicCounterArchProtocolGuid
,
272 ASSERT_EFI_ERROR (Status
);