DXE阶段为PEI阶段后，BSD阶段前，是实例化system table中具体的boot service的阶段。在此阶段中会完成内存的初始化。
Dxe的文件主函数文件在/MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c文件中。
其入口函数为DxeMain
EFI_STATUS
EFIAPI
DxeMain(
IN VOID *HobStart
)
{
EFI_STATUS Status;
EFI_PHYSICAL_ADDRESS MemoryBaseAddress;
UINT64 MemoryLength;
PE_COFF_LOADER_IMAGE_CONTEXT ImageContext;
UINTN Index;
EFI_HOB_GUID_TYPE *GuidHob;
EFI_VECTOR_HANDOFF_INFO *VectorInfoList;
EFI_VECTOR_HANDOFF_INFO *VectorInfo;
VIOD *EntryPoint;
// Setup the default exception handlers
VectorInfoList = NULL;
GuidHob = GetNextGuidHob (&gEfiVectorHandoffInfoPpiGuid, HobStart);
if (GuidHob != NULL) {
VectorInfoList = (EFI_VECTOR_HANDOFF_INFO *)(GET_GUID_HOB_DATA (GuidHob));
}
Status = InitializeCpuExceptionHandlers (VectorInfoList);
ASSERT_EFI_ERROR (Status);
// Setup Exception Stack
Status = InitializeSeparateExceptionStacks (NULL, NULL);
ASSERT_EFI_ERROR (Status);
// Initialize Debug Agent to support source level debug in DXE phase
InitializeDebugAgent (DEBUG_AGENT_INIT_DXE_CORE, HobStart, NULL);
// Initialize Memory Services
CoreInitializeMemoryServices (&HobStart, &MemoryBaseAddress, &MemoryLength);
MemoryProfileInit (HobStart);
// Start the Handle Services.
Status = CoreInitializeHandleServices ();
ASSERT_EFI_ERROR (Status);
// Initialize the Global Coherency Domain Services
Status = CoreInitializeGcdServices (&HobStart, MemoryBaseAddress, MemoryLength);
ASSERT_EFI_ERROR (Status);
// Allocate the EFI System Table and EFI Runtime Service Table from EfiRuntimeServicesData
// Use the templates to initialize the contents of the EFI System Table and EFI Runtime Services Table
gDxeCoreST = AllocateRuntimeCopyPool (sizeof (EFI_SYSTEM_TABLE), &mEfiSystemTableTemplate);
ASSERT (gDxeCoreST != NULL);
gDxeCoreRT = AllocateRuntimeCopyPool (sizeof (EFI_RUNTIME_SERVICES), &mEfiRuntimeServicesTableTemplate);
ASSERT (gDxeCoreRT != NULL);
gDxeCoreST->RuntimeServices = gDxeCoreRT;
// Update DXE Core Loaded Image Protocol with allocated UEFI System Table
gDxeCoreLoadedImage->SystemTable = gDxeCoreST;
// Call constructor for all libraries
ProcessLibraryConstructorList (gDxeCoreImageHandle, gDxeCoreST);
PERF_CROSSMODULE_END ("PEI");
PERF_CROSSMODULE_BEGIN ("DXE");
// Create the aligned system table pointer structure that is used by external
// debuggers to locate the system table... Also, install debug image info
// configuration table.
CoreInitializeDebugImageInfoTable ();
CoreNewDebugImageInfoEntry (
EFI_DEBUG_IMAGE_INFO_TYPE_NORMAL,
gDxeCoreLoadedImage,
gDxeCoreImageHandle
);
DEBUG(......);
}HOB表的struct在MdePkg/Include/Pi/PiHob.h
对于HOB表来说，包含了如下几个不同的类型：（HOB表的本质是存储在连续物理内存中的单向结构体链表）
EFI_HOB_GENERIC_HANDER：所有HOB的通用头部，包含HobType和HobLength两个主要字段。
EFI_HOB_HANDOFF_INFO_TABLE：PHIT HOB，是整个HOB列表的起点，描述了PHIT自身信息和启动模式。
EFI_HOB_MEMORY_ALLOCATION：描述内存分配信息的HOB。
EFI_HOB_RESOURCE_DESCRIPTOR：描述物理内存资源信息的HOB。
EFI_HOB_GUID_TYPE：GUID Extension HOB，用于传递自定义数据，这是PEI向DXE传递平台特定信息最常用的手段。
EFI_HOB_FIRMWARE_VOLUME：描述固件卷（FV）位置的HOB。
EFI_HOB_CPU：描述CPU信息的HOB。
HOB表在PEI阶段负责创建和写入，在DXE阶段后变为只读。DXE核心会遍历这个列表，将其中的系统资源信息（如内存布局、固件卷位置）提取出来，用于构建UEFI系统表。
typedef struct {
///
/// Identifies the HOB data structure type.
///
UINT16 HobType;
///
/// The length in bytes of the HOB.
///
UINT16 HobLength;
///
/// This field must always be set to zero.
///
UINT32 Reserved;
} EFI_HOB_GENERIC_HEADER;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_HANDOFF.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// The version number pertaining to the PHIT HOB definition.
/// This value is four bytes in length to provide an 8-byte aligned entry
/// when it is combined with the 4-byte BootMode.
///
UINT32 Version;
///
/// The system boot mode as determined during the HOB producer phase.
///
EFI_BOOT_MODE BootMode;
///
/// The highest address location of memory that is allocated for use by the HOB producer
/// phase. This address must be 4-KB aligned to meet page restrictions of UEFI.
///
EFI_PHYSICAL_ADDRESS EfiMemoryTop;
///
/// The lowest address location of memory that is allocated for use by the HOB producer phase.
///
EFI_PHYSICAL_ADDRESS EfiMemoryBottom;
///
/// The highest address location of free memory that is currently available
/// for use by the HOB producer phase.
///
EFI_PHYSICAL_ADDRESS EfiFreeMemoryTop;
///
/// The lowest address location of free memory that is available for use by the HOB producer phase.
///
EFI_PHYSICAL_ADDRESS EfiFreeMemoryBottom;
///
/// The end of the HOB list.
///
EFI_PHYSICAL_ADDRESS EfiEndOfHobList;
} EFI_HOB_HANDOFF_INFO_TABLE;
typedef struct {
///
/// A GUID that defines the memory allocation region's type and purpose, as well as
/// other fields within the memory allocation HOB. This GUID is used to define the
/// additional data within the HOB that may be present for the memory allocation HOB.
/// Type EFI_GUID is defined in InstallProtocolInterface() in the UEFI 2.0
/// specification.
///
EFI_GUID Name;
///
/// The base address of memory allocated by this HOB. Type
/// EFI_PHYSICAL_ADDRESS is defined in AllocatePages() in the UEFI 2.0
/// specification.
///
EFI_PHYSICAL_ADDRESS MemoryBaseAddress;
///
/// The length in bytes of memory allocated by this HOB.
///
UINT64 MemoryLength;
///
/// Defines the type of memory allocated by this HOB. The memory type definition
/// follows the EFI_MEMORY_TYPE definition. Type EFI_MEMORY_TYPE is defined
/// in AllocatePages() in the UEFI 2.0 specification.
///
EFI_MEMORY_TYPE MemoryType;
///
/// Padding for Itanium processor family
///
UINT8 Reserved[4];
} EFI_HOB_MEMORY_ALLOCATION_HEADER;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_MEMORY_ALLOCATION.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// An instance of the EFI_HOB_MEMORY_ALLOCATION_HEADER that describes the
/// various attributes of the logical memory allocation.
///
EFI_HOB_MEMORY_ALLOCATION_HEADER AllocDescriptor;
//
// Additional data pertaining to the "Name" Guid memory
// may go here.
//
} EFI_HOB_MEMORY_ALLOCATION;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_MEMORY_ALLOCATION.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// An instance of the EFI_HOB_MEMORY_ALLOCATION_HEADER that describes the
/// various attributes of the logical memory allocation.
///
EFI_HOB_MEMORY_ALLOCATION_HEADER AllocDescriptor;
} EFI_HOB_MEMORY_ALLOCATION_STACK;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_MEMORY_ALLOCATION.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// An instance of the EFI_HOB_MEMORY_ALLOCATION_HEADER that describes the
/// various attributes of the logical memory allocation.
///
EFI_HOB_MEMORY_ALLOCATION_HEADER AllocDescriptor;
} EFI_HOB_MEMORY_ALLOCATION_BSP_STORE;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_MEMORY_ALLOCATION.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// An instance of the EFI_HOB_MEMORY_ALLOCATION_HEADER that describes the
/// various attributes of the logical memory allocation.
///
EFI_HOB_MEMORY_ALLOCATION_HEADER MemoryAllocationHeader;
///
/// The GUID specifying the values of the firmware file system name
/// that contains the HOB consumer phase component.
///
EFI_GUID ModuleName;
///
/// The address of the memory-mapped firmware volume
/// that contains the HOB consumer phase firmware file.
///
EFI_PHYSICAL_ADDRESS EntryPoint;
} EFI_HOB_MEMORY_ALLOCATION_MODULE;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_RESOURCE_DESCRIPTOR.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// A GUID representing the owner of the resource. This GUID is used by HOB
/// consumer phase components to correlate device ownership of a resource.
///
EFI_GUID Owner;
///
/// The resource type enumeration as defined by EFI_RESOURCE_TYPE.
///
EFI_RESOURCE_TYPE ResourceType;
///
/// Resource attributes as defined by EFI_RESOURCE_ATTRIBUTE_TYPE.
///
EFI_RESOURCE_ATTRIBUTE_TYPE ResourceAttribute;
///
/// The physical start address of the resource region.
///
EFI_PHYSICAL_ADDRESS PhysicalStart;
///
/// The number of bytes of the resource region.
///
UINT64 ResourceLength;
} EFI_HOB_RESOURCE_DESCRIPTOR;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_GUID_EXTENSION.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// A GUID that defines the contents of this HOB.
///
EFI_GUID Name;
//
// Guid specific data goes here
//
} EFI_HOB_GUID_TYPE;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_FV.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// The physical memory-mapped base address of the firmware volume.
///
EFI_PHYSICAL_ADDRESS BaseAddress;
///
/// The length in bytes of the firmware volume.
///
UINT64 Length;
} EFI_HOB_FIRMWARE_VOLUME;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_FV2.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// The physical memory-mapped base address of the firmware volume.
///
EFI_PHYSICAL_ADDRESS BaseAddress;
///
/// The length in bytes of the firmware volume.
///
UINT64 Length;
///
/// The name of the firmware volume.
///
EFI_GUID FvName;
///
/// The name of the firmware file that contained this firmware volume.
///
EFI_GUID FileName;
} EFI_HOB_FIRMWARE_VOLUME2;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_CPU.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// Identifies the maximum physical memory addressability of the processor.
///
UINT8 SizeOfMemorySpace;
///
/// Identifies the maximum physical I/O addressability of the processor.
///
UINT8 SizeOfIoSpace;
///
/// This field will always be set to zero.
///
UINT8 Reserved[6];
} EFI_HOB_CPU;
typedef struct {
///
/// The HOB generic header. Header.HobType = EFI_HOB_TYPE_MEMORY_POOL.
///
EFI_HOB_GENERIC_HEADER Header;
} EFI_HOB_MEMORY_POOL;
typedef struct {
///
/// The HOB generic header where Header.HobType = EFI_HOB_TYPE_UEFI_CAPSULE.
///
EFI_HOB_GENERIC_HEADER Header;
///
/// The physical memory-mapped base address of an UEFI capsule. This value is set to
/// point to the base of the contiguous memory of the UEFI capsule.
/// The length of the contiguous memory in bytes.
///
EFI_PHYSICAL_ADDRESS BaseAddress;
UINT64 Length;
} EFI_HOB_UEFI_CAPSULE;
typedef union {
EFI_HOB_GENERIC_HEADER *Header;
EFI_HOB_HANDOFF_INFO_TABLE *HandoffInformationTable;
EFI_HOB_MEMORY_ALLOCATION *MemoryAllocation;
EFI_HOB_MEMORY_ALLOCATION_BSP_STORE *MemoryAllocationBspStore;
EFI_HOB_MEMORY_ALLOCATION_STACK *MemoryAllocationStack;
EFI_HOB_MEMORY_ALLOCATION_MODULE *MemoryAllocationModule;
EFI_HOB_RESOURCE_DESCRIPTOR *ResourceDescriptor;
EFI_HOB_GUID_TYPE *Guid;
EFI_HOB_FIRMWARE_VOLUME *FirmwareVolume;
EFI_HOB_FIRMWARE_VOLUME2 *FirmwareVolume2;
EFI_HOB_FIRMWARE_VOLUME3 *FirmwareVolume3;
EFI_HOB_CPU *Cpu;
EFI_HOB_MEMORY_POOL *Pool;
EFI_HOB_UEFI_CAPSULE *Capsule;
UINT8 *Raw;
} EFI_PEI_HOB_POINTERS;
由于这一部分内容有点过于多了，这里只做一个简介，具体的PEI是如何实现基本的四大件工作：内存管理基本管理、GUID基本管理、Firmware固件基本管理、CPU基本管理的，有待后续进一步文章研究。