This protocol is similar with DXE FVB protocol and used in the UEFI SMM evvironment.
Include/Protocol/SmmFirmwareVolumeBlock.h

PROTOCOL Information

PROTOCOL's Guid Name	PROTOCOL's Guid
gEfiSmmFirmwareVolumeBlockProtocolGuid	{ 0xd326d041, 0xbd31, 0x4c01, { 0xb5, 0xa8, 0x62, 0x8b, 0xe8, 0x7f, 0x6, 0x53 }}

Refer to Header File