Getnexthighmonotoniccount() - Intel Extensible Firmware Interface Specification

Extensible Firmware Interface Specification
3.8.5

GetNextHighMonotonicCount()

Summary
Returns the next high 32 bits of the platform's monotonic counter.
Prototype
EFI_STATUS
GetNextHighMonotonicCount (
OUT UINT32
);
Parameters
HighCount
Description
The
GetNextHighMonotonicCount()
monotonic counter.
The platform's monotonic counter is comprised of two 32 bit quantities: the high 32 bits and the
low 32 bits. During boot service time the low 32 bit value is volatile: it is reset to zero on every
system reset and is increased by 1 on every call to
32 bit value is non-volatile and is increased by 1 whenever the system resets or whenever the low
32 bit count [returned by GetNextMonoticCount()] overflows.
The
GetNextMonotonicCount()
operating system wishes to extend the platform monotonic counter to runtime, it may do so by
utilizing GetNextHighMonotonicCount(). To do this, before calling
ExitBootServices()
obtain the current platform monotonic count. The operating system would then provide an
interface that returns the next count by:
•
Adding 1 to the last count.
•
Before the lower 32 bits of the count overflows, call GetNextHighMonotonicCount().
This will increase the high 32 bits of the platform's non-volatile portion of the monotonic count
by 1.
This function may only be called at Runtime.
Status Codes Returned
EFI_SUCCESS
EFI_DEVICE_ERROR
EFI_INVALID_PARAMETER
102
*HighCount
Pointer to returned value.
function returns the next high 32 bits of the platform's
GetNextMonotonicCount().
function is only available at boot services time. If the
the operating system would call
The next high monotonic count was returned.
The device is not functioning properly.
One of the parameters has an invalid value.
12/12/00
GetNextMonotonicCount()
Version 1.02
The high
to