5.1 Services that UEFI drivers commonly use

The following table lists UEFI services commonly used by UEFI drivers. Following that, discussions briefly describe each service, why they are commonly used, or the particular circumstance in which they are useful. Code examples show how the services are typically used by UEFI drivers and are grouped by Service Type.
Table 18-UEFI services that are commonly used by UEFI drivers
Service
Type
Service Type
Description
AllocatePool()
Boot
Memory Allocation
Allocates a memory buffer of a particular type.
FreePool()
Boot
Memory Allocation
Frees a previously allocated memory buffer.
AllocatePages()
Boot
Memory Allocation
Allocates one memory buffer of a particular type with a 4KB aligned start address and a 4KB aligned length.
FreePages()
Boot
Memory Allocation
Frees a memory buffer previously allocated with AllocatePages().
CopyMem()
Boot
Miscellaneous
Copies a buffer from one location to another.
SetMem()
Boot
Miscellaneous
Initializes the contents of a buffer with a specified value.
InstallMultipleProtocolInterfa ces()
Boot
Protocol Handler
Installs one or more protocol interfaces onto a handle. Replaces the InstallProtocolInterface() service.
UninstallMultipleProtocolInter faces()
Boot
Protocol Handler
Uninstalls one or more protocol interfaces from a handle. Replaces the UninstallProtocolInterface() service.
LocateHandleBuffer()
Boot
Protocol Handler
Retrieves a list of handles from the handle database meeting the search criteria. The return buffer is automatically allocated.
LocateProtocol()
Boot
Protocol Handler
Finds the first handle in the handle database supporting the requested protocol.
OpenProtocol()
Boot
Protocol Handler
Adds elements to the list of agents consuming a protocol interface.
OpenProtocolInformation()
Boot
Protocol Handler
Retrieves the list of agents currently consuming a protocol interface.
CloseProtocol()
Boot
Protocol Handler
Removes elements from the list of agents consuming a protocol interface.
RaiseTPL()
Boot
Task Priority
Raises the task priority level.
RestoreTPL()
Boot
Task Priority
Restores/lowers the task priority level.
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CreateEvent()
Boot
Event
Creates a general-purpose event structure.
CreateEventEx()
Boot
Event
Creates an event structure as part of an event group. This service is new.
CloseEvent()
Boot
Event
Closes and frees an event structure.
SignalEvent()
Boot
Event
Signals an event.
CheckEvent()
Boot
Event
Checks whether an event is in the signaled state.
SetTimer()
Boot
Time-related
Sets an event to be signaled at a particular time.
Stall()
Boot
Time-related
Waits for a specified number of microseconds. This is a time-related service with the highest accuracy.

5 UEFI Services

5.1.1 Memory Allocation Services

Last updated 1 year ago

Service	Type	Service Type	Description
AllocatePool()	Boot	Memory Allocation	Allocates a memory buffer of a particular type.
FreePool()	Boot	Memory Allocation	Frees a previously allocated memory buffer.
AllocatePages()	Boot	Memory Allocation	Allocates one memory buffer of a particular type with a 4KB aligned start address and a 4KB aligned length.
FreePages()	Boot	Memory Allocation	Frees a memory buffer previously allocated with AllocatePages().
CopyMem()	Boot	Miscellaneous	Copies a buffer from one location to another.
SetMem()	Boot	Miscellaneous	Initializes the contents of a buffer with a specified value.
InstallMultipleProtocolInterfa ces()	Boot	Protocol Handler	Installs one or more protocol interfaces onto a handle. Replaces the InstallProtocolInterface() service.
UninstallMultipleProtocolInter faces()	Boot	Protocol Handler	Uninstalls one or more protocol interfaces from a handle. Replaces the UninstallProtocolInterface() service.
LocateHandleBuffer()	Boot	Protocol Handler	Retrieves a list of handles from the handle database meeting the search criteria. The return buffer is automatically allocated.
LocateProtocol()	Boot	Protocol Handler	Finds the first handle in the handle database supporting the requested protocol.
OpenProtocol()	Boot	Protocol Handler	Adds elements to the list of agents consuming a protocol interface.
OpenProtocolInformation()	Boot	Protocol Handler	Retrieves the list of agents currently consuming a protocol interface.
CloseProtocol()	Boot	Protocol Handler	Removes elements from the list of agents consuming a protocol interface.
RaiseTPL()	Boot	Task Priority	Raises the task priority level.
RestoreTPL()	Boot	Task Priority	Restores/lowers the task priority level.

CreateEvent()	Boot	Event	Creates a general-purpose event structure.
CreateEventEx()	Boot	Event	Creates an event structure as part of an event group. This service is new.
CloseEvent()	Boot	Event	Closes and frees an event structure.
SignalEvent()	Boot	Event	Signals an event.
CheckEvent()	Boot	Event	Checks whether an event is in the signaled state.
SetTimer()	Boot	Time-related	Sets an event to be signaled at a particular time.
Stall()	Boot	Time-related	Waits for a specified number of microseconds. This is a time-related service with the highest accuracy.