BIOS Memory Service Overview

System Memory

  • MEMORY SERVICES
  • HOB TYPE
    • RESOURCE HOB
      • Type:
      • Attributes:
  • (System)MEMORY TYPE
  • DXE/SMM: PAGE ALLOCATION TYPE
  • PEI MEMORY LAYOUT
  • DXE MEMORY LAYOUT
  • MEMMAP

MEMORY SERVICES

  • PEI on CAR and System Memory
    • CreateHob
    • AllocatePool: Light version. Don』t support memory type. No FreePool API. It bases on HOB.
    • AllocatePages/FreePages: Don』t support memory allocate type.
  • DXE on System Memory
    • AllocatePool/FreePool
    • AllocatePages/FreePages
  • SMM on SMRAM
    • AllocatePool/FreePool: support runtime data/code only
    • AllocatePages/FreePages: support runtime data/code only

HOB TYPE

根據使用的不同需求，定義以下型別：

  • EFI_HOB_TYPE_HANDOFF: Basic Hob information，描述Hob空間的起始結束地址以及那些空間可用
  • EFI_HOB_TYPE_MEMORY_ALLOCATION：描述已被申請的memory的起始地址和結束地址
    • Describe the allocated page memory base address, size and type
  • EFI_HOB_TYPE_RESOURCE_DESCRIPTOR：描述系統資源及屬性情況，包括系統空間屬性等
    • Describe the system resource and attribute, include memory,SMRAM IO and MMIO
  • EFI_HOB_TYPE_GUID_EXTENSION：為了在模組和內部的function之間共享資料
  • Main usage is to share data between pre-memory and after-memory
  • EFI_HOB_TYPE_FV：每個FV可以有一個HOB，Fv Hob是給DXE階段使用，
    • FV reported to DXE phase
  • EFI_HOB_TYPE_CPU
  • EFI_HOB_TYPE_MEMORY_POOL
    在開發過程中可能用到的，RESOURCE_DESCRIPTOR、GUID_EXTENSION、FV

RESOURCE HOB

Type:

? EFI_RESOURCE_SYSTEM_MEMORY：記憶體，可以執行程式碼儲存資料等操作
? EFI_RESOURCE_MEMORY_MAPPED_IO
? EFI_RESOURCE_IO
? EFI_RESOURCE_FIRMWARE_DEVICE：描述flash這一塊空間
? EFI_RESOURCE_MEMORY_MAPPED_IO_PORT
? EFI_RESOURCE_MEMORY_RESERVED
? EFI_RESOURCE_IO_RESERVED

Attributes:

? EFI_RESOURCE_ATTRIBUTE_PRESENT：是否存在
? EFI_RESOURCE_ATTRIBUTE_INITIALIZED：是否初始化
? EFI_RESOURCE_ATTRIBUTE_TESTED：是否已測試
? EFI_RESOURCE_ATTRIBUTE_PERSISTENT：是否一直存在（掉電不遺失）

(System)MEMORY TYPE

  • EfiConventionalMemory: Available memory space

  • EfiLoaderCode: UEFI Application code

  • EfiLoaderData: UEFI Application data

  • EfiBootServicesCode: UEFI/PEI/DXE driver

  • EfiBootServicesData: UEFI/PEI/DXE driver allocated memory

  • EfiPersistentMemory

  • EfiRuntimeServicesCode: Runtime driver. It can』t be used by OS.

  • EfiRuntimeServicesData: Runtime data. It can』t be used by OS.

  • EfiReservedMemoryType: Reserved memory in BIOS. It can』t be used by OS.

  • EfiACPIReclaimMemory: Used by ACPI.

  • EfiACPIMemoryNVS: Used by ACPI. It can』t be used by OS.

  • EfiMemoryMappedIO

  • EfiMemoryMappedIOPortSpace

DXE/SMM: PAGE ALLOCATION TYPE

? AllocateAnyPages: Allocate memory in the available memory space.
? AllocateMaxAddress: Allocate memory based on the specified max address.
? AllocateAddress: Allocate memory at the specified base address.

PEI MEMORY LAYOUT

Example HOB Producer Phase Memory Map and Usage
上圖中：PHIT就是一個HOB，Handoff型別，包含基本的information，由下往上，PHIT作為第一個HOB,管理方式為不斷疊加，一旦某塊資料越界，整體的HOB會毀壞，但由於PEI階段的resource有限，尚不構成影響。某塊HOB失去作用時，也是沒有辦法取走的，只能不停新增。memory為從高往低進行分配，與HOB並不從衝突，當無空間可用則會報錯out of resource。Allocate申請的記憶體為Free space部分

DXE MEMORY LAYOUT

  • Top reserved memory ranges are specified by EFI_MEMORY_TYPE_INFORMATION.
  • Memory allocation is from top to bottom.
  • Memory allocation is from its reserved memory type range. If no enough, it will be allocated from the remaining memory.
  • Pool and Page are in the same memory range.
  • PEI Memory is reported in PEI phase.

MEMMAP

memorymap 這個command會羅列出當前系統中所有的memory，包括其分配情況，剩餘量等。

Type Start End # Pages Attributes
BS_Data 00000000B5002000 -00000000B53B9FFF 00000000000003B8 000000000000000F
BS_Code 00000000B53BA000 -00000000B53E6FFF 000000000000002D 000000000000000F
…
Reserved 00000000BBE5F000 -00000000BBE5FFFF 0000000000000001 000000000000000F
ACPI_Recl 00000000BBE60000 -00000000BC02FFFF 00000000000001D0 000000000000000F
ACPI_NVS 00000000BC030000 -00000000BC08FFFF 0000000000000060 000000000000000F
RT_Data 00000000BC090000 -00000000BF67FFFF 00000000000035F0 800000000000000F
RT_Code 00000000BF7C0000 -00000000BFC7FFFF 00000000000004C0 800000000000000F
Available 0000400100000000 -00004007FFFFFFFF 0000000000700000 000000000000000F
MMIO 00001000026D0000 -00001000026DFFFF 0000000000000010 8000000000000000
Reserved : 869 Pages (3,559,424 Bytes)
LoaderCode: 339 Pages (1,388,544 Bytes)
LoaderData: 0 Pages (0 Bytes)
BS_Code : 11,391 Pages (46,657,536 Bytes)
BS_Data : 16,957 Pages (69,455,872 Bytes)
RT_Code : 1,216 Pages (4,980,736 Bytes)
RT_Data : 16,496 Pages (67,567,616 Bytes)
ACPI_Recl : 479 Pages (1,961,984 Bytes)
ACPI_NVS : 96 Pages (393,216 Bytes)
MMIO : 32 Pages (131,072 Bytes)
MMIO_ Port : 0 Pages (0 Bytes)
PalCode : 0 Pages (0 Bytes)
Available : 16,401,949 Pages (67,182,383,104 Bytes)
Persistent: 0 Pages (0 Bytes)
Total Memory: 64,253 MB (67,374,788,608 Bytes)