Appendix E: Glossary

Comprehensive glossary of UEFI terminology, acronyms, and error codes.

UEFI Terminology

A

Term Definition
ACPI Advanced Configuration and Power Interface - power management and hardware discovery
AML ACPI Machine Language - bytecode for ACPI control methods
ASL ACPI Source Language - high-level language compiled to AML

B

Term Definition
BDS Boot Device Selection - phase that discovers boot devices and launches OS
BL1 Boot Loader stage 1 (ARM) - ROM-resident trusted boot
BL2 Boot Loader stage 2 (ARM) - trusted boot loader
BL31 EL3 Runtime Firmware (ARM) - secure monitor
BL32 Secure-EL1 Payload (ARM) - optional secure OS
BL33 Non-secure EL2/1 Payload (ARM) - usually UEFI
BMC Baseboard Management Controller - out-of-band management
Boot Services Functions available before ExitBootServices()
BSA Base System Architecture (ARM) - hardware requirements
BSP Board Support Package / Bootstrap Processor

C

Term Definition
Capsule Firmware update package delivered to UEFI
ConIn Console Input device handle
ConOut Console Output device handle

D

Term Definition
DEC Package Declaration file (.dec)
DSC Platform Description file (.dsc)
DXE Driver Execution Environment - main firmware phase
DXE Core Central dispatcher for DXE phase
DXE Driver Driver loaded during DXE phase

E

Term Definition
EDK2 EFI Development Kit II - open source UEFI implementation
EFI Extensible Firmware Interface (predecessor to UEFI)
EL0-EL3 ARM Exception Levels (0=User, 1=OS, 2=Hypervisor, 3=Secure Monitor)
ESP EFI System Partition - FAT partition for boot files
Event Asynchronous notification mechanism in UEFI

F

Term Definition
FD Flash Device - binary firmware image
FDF Flash Description File (.fdf)
FFS Firmware File System - file system within FV
FIP Firmware Image Package (ARM TF-A)
FIT Firmware Interface Table
FV Firmware Volume - container for firmware files
FVB Firmware Volume Block protocol

G

Term Definition
GCD Global Coherency Domain - memory/IO space management
GIC Generic Interrupt Controller (ARM)
GOP Graphics Output Protocol - graphical display
GPT GUID Partition Table - disk partitioning scheme
GUID Globally Unique Identifier - 128-bit identifier

H

Term Definition
Handle Opaque pointer to a collection of protocols
Handle Database Collection of all handles and protocols
HII Human Interface Infrastructure - UI framework
HOB Hand-Off Block - data passed between phases
HVC Hypervisor Call (ARM EL2)

I

Term Definition
INF Module Information file (.inf)
Image Executable loaded by UEFI (PE/COFF format)
IPMI Intelligent Platform Management Interface

L

Term Definition
Library Class Abstract interface for code reuse
Library Instance Concrete implementation of library class
LoadedImage Protocol describing a loaded UEFI image

M

Term Definition
MdePkg Module Development Environment Package - core EDK2
MdeModulePkg Core UEFI modules package
Memory Map Description of system memory layout
MMIO Memory-Mapped I/O

N

Term Definition
NVRAM Non-Volatile RAM - stores UEFI variables

O

Term Definition
OVMF Open Virtual Machine Firmware - QEMU UEFI

P

Term Definition
PCD Platform Configuration Database - build-time/runtime config
PE/COFF Portable Executable - UEFI executable format
PEI Pre-EFI Initialization - early boot phase
PEIM PEI Module
PI Platform Initialization - lower-level specification
PPI PEI-to-PEI Interface - services in PEI phase
Protocol Interface exposed via handle database
PSCI Power State Coordination Interface (ARM)

R

Term Definition
RAS Reliability, Availability, Serviceability
RSDP Root System Description Pointer (ACPI)
Runtime Driver Driver persisting after ExitBootServices()
Runtime Services Functions available after ExitBootServices()

S

Term Definition
SBSA Server Base System Architecture (ARM)
SCT Self Certification Test - UEFI compliance tests
SEC Security phase - first code executed
Secure Boot Signature verification for boot images
SMC Secure Monitor Call (ARM EL3)
SMBIOS System Management BIOS - hardware info tables
SMM System Management Mode (x86)
SMM Driver Driver running in SMM
StdErr Standard Error output

T

Term Definition
TF-A Trusted Firmware-A (ARM reference implementation)
TPL Task Priority Level - interrupt priority
TPM Trusted Platform Module - security coprocessor
TrustZone ARM security architecture
TSL Transient System Load - boot phase

U

Term Definition
UEFI Unified Extensible Firmware Interface
UEFI Application Standalone executable (exits after use)
UEFI Driver Persistent module following driver model

V

Term Definition
Variable Persistent name-value pair in NVRAM
VFR Visual Forms Representation - HII forms language

EFI_STATUS Codes

Success Codes

Code Value Description
EFI_SUCCESS 0 Operation completed successfully

Error Codes (High bit set)

Code Value Description
EFI_LOAD_ERROR 1 Image failed to load
EFI_INVALID_PARAMETER 2 Parameter is incorrect
EFI_UNSUPPORTED 3 Operation not supported
EFI_BAD_BUFFER_SIZE 4 Buffer is wrong size
EFI_BUFFER_TOO_SMALL 5 Buffer is too small
EFI_NOT_READY 6 No data pending
EFI_DEVICE_ERROR 7 Physical device error
EFI_WRITE_PROTECTED 8 Cannot write to device
EFI_OUT_OF_RESOURCES 9 Resource allocation failed
EFI_VOLUME_CORRUPTED 10 File system is corrupted
EFI_VOLUME_FULL 11 No space on volume
EFI_NO_MEDIA 12 No medium in device
EFI_MEDIA_CHANGED 13 Medium has changed
EFI_NOT_FOUND 14 Item was not found
EFI_ACCESS_DENIED 15 Access was denied
EFI_NO_RESPONSE 16 Server not responding
EFI_NO_MAPPING 17 No mapping exists
EFI_TIMEOUT 18 Operation timed out
EFI_NOT_STARTED 19 Protocol not started
EFI_ALREADY_STARTED 20 Protocol already started
EFI_ABORTED 21 Operation was aborted
EFI_ICMP_ERROR 22 ICMP error received
EFI_TFTP_ERROR 23 TFTP error received
EFI_PROTOCOL_ERROR 24 Protocol error occurred
EFI_INCOMPATIBLE_VERSION 25 Version incompatibility
EFI_SECURITY_VIOLATION 26 Security check failed
EFI_CRC_ERROR 27 CRC check failed
EFI_END_OF_MEDIA 28 End of media reached
EFI_END_OF_FILE 31 End of file reached
EFI_INVALID_LANGUAGE 32 Language not supported
EFI_COMPROMISED_DATA 33 Security compromised
EFI_IP_ADDRESS_CONFLICT 34 IP address conflict
EFI_HTTP_ERROR 35 HTTP error occurred

Warning Codes

Code Value Description
EFI_WARN_UNKNOWN_GLYPH 1 Glyph not found
EFI_WARN_DELETE_FAILURE 2 Delete operation failed
EFI_WARN_WRITE_FAILURE 3 Write operation failed
EFI_WARN_BUFFER_TOO_SMALL 4 Buffer is too small
EFI_WARN_STALE_DATA 5 Data may be stale
EFI_WARN_FILE_SYSTEM 6 File system warning
EFI_WARN_RESET_REQUIRED 7 Reset is required

Error Handling Macros 

// Check if status is an error
#define EFI_ERROR(Status)  (((INTN)(RETURN_STATUS)(Status)) < 0)

// Common pattern
EFI_STATUS Status;
Status = SomeFunction();
if (EFI_ERROR(Status)) {
    DEBUG((DEBUG_ERROR, "Failed: %r\n", Status));
    return Status;
}

// Using ASSERT
ASSERT_EFI_ERROR(Status);  // Halts on error in DEBUG builds

Memory Types

Type Value Description After ExitBootServices
EfiReservedMemoryType 0 Not usable Reserved
EfiLoaderCode 1 UEFI app code Available
EfiLoaderData 2 UEFI app data Available
EfiBootServicesCode 3 Boot services code Available
EfiBootServicesData 4 Boot services data Available
EfiRuntimeServicesCode 5 Runtime code Preserved
EfiRuntimeServicesData 6 Runtime data Preserved
EfiConventionalMemory 7 Free memory Available
EfiUnusableMemory 8 Error-prone memory Unusable
EfiACPIReclaimMemory 9 ACPI tables Reclaimable
EfiACPIMemoryNVS 10 ACPI NVS Preserved
EfiMemoryMappedIO 11 MMIO Mapped
EfiMemoryMappedIOPortSpace 12 MMIO port Mapped
EfiPalCode 13 PAL code (Itanium) Preserved
EfiPersistentMemory 14 Persistent memory Preserved
EfiUnacceptedMemoryType 15 TDX unaccepted Must accept

Memory Attributes

Attribute Bit Description
EFI_MEMORY_UC 0 Uncacheable
EFI_MEMORY_WC 1 Write Combining
EFI_MEMORY_WT 2 Write Through
EFI_MEMORY_WB 3 Write Back
EFI_MEMORY_UCE 4 Uncacheable Exported
EFI_MEMORY_WP 12 Write Protected
EFI_MEMORY_RP 13 Read Protected
EFI_MEMORY_XP 14 Execute Protected
EFI_MEMORY_NV 15 Non-Volatile
EFI_MEMORY_MORE_RELIABLE 16 More reliable
EFI_MEMORY_RO 17 Read Only
EFI_MEMORY_SP 18 Specific Purpose
EFI_MEMORY_CPU_CRYPTO 19 CPU Crypto
EFI_MEMORY_RUNTIME 63 Runtime mapping needed

Boot Phase Events

TPL Levels

Level Value Description
TPL_APPLICATION 4 Normal application level
TPL_CALLBACK 8 Callback priority
TPL_NOTIFY 16 Notification level
TPL_HIGH_LEVEL 31 Highest priority (interrupts disabled)

Event Types

Event Description
EVT_TIMER Timer-based event
EVT_RUNTIME Survives ExitBootServices
EVT_NOTIFY_WAIT Checked via WaitForEvent
EVT_NOTIFY_SIGNAL Notification on signal
EVT_SIGNAL_EXIT_BOOT_SERVICES ExitBootServices notification
EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE SetVirtualAddressMap notification

Protocol GUIDs

Common System Protocols

Protocol Description
gEfiLoadedImageProtocolGuid Information about loaded image
gEfiDevicePathProtocolGuid Device path for a handle
gEfiSimpleTextInProtocolGuid Text input (keyboard)
gEfiSimpleTextOutProtocolGuid Text output (console)
gEfiGraphicsOutputProtocolGuid Graphics framebuffer
gEfiBlockIoProtocolGuid Block device access
gEfiDiskIoProtocolGuid Disk I/O with byte offsets
gEfiSimpleFileSystemProtocolGuid File system access
gEfiUnicodeCollationProtocolGuid String comparison

Driver Protocols

Protocol Description
gEfiDriverBindingProtocolGuid Driver binding interface
gEfiComponentNameProtocolGuid Component name (obsolete)
gEfiComponentName2ProtocolGuid Component name (current)
gEfiDriverDiagnosticsProtocolGuid Driver diagnostics
gEfiDriverConfiguration2ProtocolGuid Driver configuration
gEfiPlatformDriverOverrideProtocolGuid Driver override

Network Protocols

Protocol Description
gEfiSimpleNetworkProtocolGuid Raw network access
gEfiManagedNetworkProtocolGuid Managed network
gEfiArpProtocolGuid ARP protocol
gEfiIp4ProtocolGuid IPv4 protocol
gEfiTcp4ProtocolGuid TCPv4 protocol
gEfiUdp4ProtocolGuid UDPv4 protocol
gEfiDhcp4ProtocolGuid DHCPv4 client
gEfiDns4ProtocolGuid DNS resolver
gEfiHttpProtocolGuid HTTP client

Security Protocols

Protocol Description
gEfiSecurityArchProtocolGuid Security architecture
gEfiSecurity2ArchProtocolGuid Security2 architecture
gEfiTcg2ProtocolGuid TPM 2.0 interface
gEfiRngProtocolGuid Random number generator
gEfiHashProtocolGuid Hash algorithms
gEfiHash2ProtocolGuid Hash2 algorithms
gEfiPkcs7VerifyProtocolGuid PKCS7 verification

Variable Attributes

Attribute Value Description
EFI_VARIABLE_NON_VOLATILE 0x00000001 Stored in NVRAM
EFI_VARIABLE_BOOTSERVICE_ACCESS 0x00000002 Accessible in boot services
EFI_VARIABLE_RUNTIME_ACCESS 0x00000004 Accessible at runtime
EFI_VARIABLE_HARDWARE_ERROR_RECORD 0x00000008 Hardware error log
EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS 0x00000010 Deprecated
EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS 0x00000020 Authenticated
EFI_VARIABLE_APPEND_WRITE 0x00000040 Append to variable

Standard Variables

Variable Vendor GUID Description
BootOrder gEfiGlobalVariableGuid Boot option order
BootXXXX gEfiGlobalVariableGuid Boot option N
BootNext gEfiGlobalVariableGuid Next boot option
BootCurrent gEfiGlobalVariableGuid Current boot option
Timeout gEfiGlobalVariableGuid Boot timeout
PlatformLang gEfiGlobalVariableGuid Platform language
ConIn gEfiGlobalVariableGuid Console input devices
ConOut gEfiGlobalVariableGuid Console output devices
ErrOut gEfiGlobalVariableGuid Error output devices
PK gEfiGlobalVariableGuid Platform Key
KEK gEfiGlobalVariableGuid Key Exchange Keys
db gEfiImageSecurityDatabaseGuid Allowed signatures
dbx gEfiImageSecurityDatabaseGuid Forbidden signatures
SecureBoot gEfiGlobalVariableGuid Secure Boot status
SetupMode gEfiGlobalVariableGuid Setup Mode status

References

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