《UEFI内核导读》UEFI Firmware Storage简介

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          UEFI固件一般存储在被称之为“固件仓库”的非易失性存储器中，简称为FD（固件设备），当前主流的存储介质是NorFlash它拥有非易失性、XIP以及可二次编程的特性。

        固件设备可以分为物理设备和逻辑设备，一个NorFlash固件设备可以被划分为多个逻辑设备FV（Firmware Volume），同理多个物理固件设备也可以组成更大的逻辑设备，FV是最基本的“固件设备”管理单元，被称之为FFS（Firmware File System）。FV以唯一的GUID来区分，同时它会有不同的类型如FFS2或FFS3，以及对其读写控制的其他的属性。FD组织方式是：Section->Firmware File->FV->FD，下文分别介绍。

        Firmware File：用来存储代码或数据，在FV当中它是由GUID来唯一命名，具有文件类型、存储对齐方式、文件大小等属性。UEFI提供了基本的服务来访问Fireware File，在PEI阶段用EFI_PEI_SERVICES->(FfsFindNextFile, FfsFindFileByName、FfsGetFileInfo），在DXE阶段用EFI_FIRMWARE_VOLUME2_PROTOCOL->(ReadFile, ReadSection、WriteFile、GetNextFile）, 或EFI_BOOT_SERVICES->LoadImage()。

        Firmware File Section：组成Firmware File的最小单元，由2个最基本的属性，一个是类型，另一个是所占用的存储空间大小。UEFI提供了基本的服务来访问Fireware File Section,在PEI阶段用EFI_PEI_SERVICES->FfsFindSectionData，在DXE阶段用EFI_FIRMWARE_VOLUME2_PROTOCOL->ReadSection

FFS PI Firmware File Types:

PI File Type	Value	Mnemonic
EFI_FV_FILETYPE_RAW	0x01	Binary data
EFI_FV_FILETYPE_FREEFORM	0x02	Sectioned data
EFI_FV_FILETYPE_SECURITY_CORE	0x03	Platform core code used during the SEC phase
EFI_FV_FILETYPE_PEI_CORE	0x04	PEI Foundation
EFI_FV_FILETYPE_DXE_CORE	0x05	DXE Foundation
EFI_FV_FILETYPE_PEIM	0x06	PEI module (PEIM)
EFI_FV_FILETYPE_DRIVER	0x07	DXE driver
EFI_FV_FILETYPE_COMBINED_PEIM_DRIVER	0x08	Combined PEIM/DXE driver
EFI_FV_FILETYPE_APPLICATION	0x09	Application
EFI_FV_FILETYPE_MM	0x0A	Contains a PE32+ image that will be loaded into MMRAM in MM Traditional Mode.
EFI_FV_FILETYPE_FIRMWARE_VOLUME_IMAGE	0x0B	Firmware volume image
EFI_FV_FILETYPE_COMBINED_MM_DXE	0x0C	Contains PE32+ image that will be dispatched by the DXE Dispatcher and will also be loaded into MMRAM in MM Tradition Mode.
EFI_FV_FILETYPE_MM_CORE	0x0D	MM Foundation that support MM Traditional Mode
EFI_FV_FILETYPE_MM_STANDALONE	0x0E	Contains a PE32+ image that will be loaded into MMRAM in MM Standalone Mode.
EFI_FV_FILETYPE_MM_CORE_STANDALONE	0x0F	MM Foundation that support MM Tradition Mode and MM Standalone Mode
EFI_FV_FILETYPE_OEM_MIN… EFI_FV_FILETYPE_OEM_MAX	0xC0-0xDF	OEM File Types
EFI_FV_FILETYPE_DEBUG_MIN… EFI_FV_FILETYPE_DEBUG_MAX	0xE0- 0xEF	Debug/Test File Types
EFI_FV_FILETYPE_FFS_MIN… EFI_FV_FILETYPE_FFS_MAX	0xF0- 0xFF	Firmware File System Specific File Types
EFI_FV_FILETYPE_FFS_PAD	0xF0	Pad File For FFS

FFS PI Section Types:

PI Section Type	Value	Mnemonic
EFI_SECTION_COMPRESSION	0x01	Encapsulation section where other sections are compressed
EFI_SECTION_GUID_DEFINED	0x02	Encapsulation section where other sections have format defined by a GUID
EFI_SECTION_DISPOSABLE	0x03	Encapsulation section used during the build process but not required for execution
EFI_SECTION_PE32	0x10	PE32+ Executable image.
EFI_SECTION_PIC	0x11	Position-Independent Code
EFI_SECTION_TE	0x12	Terse Executable image
EFI_SECTION_DXE_DEPEX	0x13	DXE Dependency Expression
EFI_SECTION_VERSION	0x14	Version, Text and Numeric.
EFI_SECTION_USER_INTERFACE	0x15	User-Friendly name of the driver
EFI_SECTION_COMPATIBILITY16	0x16	DOS-style 16-bit EXE
EFI_SECTION_FIRMWARE_VOLUME_IMAGE	0x17	PI Firmware Volume image
EFI_SECTION_FREEFORM_SUBTYPE_GUID	0x18	Raw data with GUID in header to define format
EFI_SECTION_RAW	0x19	Raw data
EFI_SECTION_PEI_DEPEX	0x1b	PEI Dependency Expression
EFI_SECTION_MM_DEPEX	0x1c	Leaf section type for determining the dispatch order for an MM Traditional driver in MM Traditional Mode or MM Standaline driver in MM Standalone Mode

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