UEFI : ROM 格式

相關設定請參考 .fdf (Flash Description Files)檔案

UEFI對於ROM的格式，可以分為下面幾項：(由大集合到小集合)

● Firmware Device (FD):

Bios Rom即是一個 FD, 一個FD可以由多個FV組成

● Firmware Volume (FV):

每個FV通常是由一個 header+N個Firmware Files所組成, 一般說的Boot Firmware Volume/ Recovery Firmware Volume/ Main Firmware Volume就是以這個為單位, FV的細部定義如下:

C# 呼叫 VC++ 的dll 檔

fallowing example been tested ok in VC 2010

UEFI 各階段資料的傳遞方式

  將bios 選單變數(ex: SetupData.my_var)傳遞到PEI及DXE的方法

  //
  // PEI 接收資料
  //
  Status = (*PeiServices)->LocatePpi (
                          PeiServices,
                          &gEfiPeiReadOnlyVariablePpiGuid,
                          0,
                          NULL,
                          &ReadOnlyVariable
                          );
                          
  ASSERT_PEI_ERROR (PeiServices, Status);
  VariableSize = sizeof (SETUP_DATA);
  
  Status = ReadOnlyVariable->GetVariable (
                            PeiServices,
                            L"Setup",
                            &gEfiSetupGuid,
                            NULL,
                            &VariableSize,
                            &SetupData
                            );
                            
  if (EFI_ERROR (Status)) 
      return;

SMBios (System Management Bios)

使用者可以透過SMBios知道這台電腦的詳細規格，RW everything / RW這些tool都有提供SMBios data查詢。

SMBios是一份軟體的spec, 他定義了兩個table, 即EPS ( Entry Point structure) 和 Structure Table

EPS位於記憶體1MB以下64K之間，也就是0xF0000 ~ 0xFFFFF之間。透過程式搜尋搜尋_SM_和_DMI_這兩個Keyword可以找到這個table。

以下是 SMBIOS 2.1 (32-bit) Entry Point structure，這邊列出比較重要的部分

Offset	Name	Length	Description
00h	Anchor String	4 BYTEs	_SM_, specified as four ASCII characters (5F 53 4D 5F).
10h	Intermediate Anchor String	5 BYTEs	_DMI_, specified as five ASCII characters (5F 44 4D 49 5F)
16h	Structure Table Length	WORD	Total length of SMBIOS Structure Table, pointed to by the Structure Table Address, in bytes
18h	Structure Table Address	DWORD	32-bit physical starting address of the read-only SMBIOS Structure
1Ch	Number of SMBIOS Structures	WORD	Handle的數量

UEFI : DXE Driver

● 何謂Protocol:  

typedef的結構。在UEFI下會綁定GUID，並且透過Driver來安裝Protocol instance到handle上. 上層若要控制device，必須透過呼叫Protocol instance來達成。

● Bus Driver Vs. Device Driver: 

Bus Driver會Create Child handle 但Device Driver不會。如果Bus Driver Create的 Child handle是Physical device, Bus Driver 必須安裝Device Path Protocol instance到Child handle

● Driver Initialization:

Driver Image會從儲存裝置(Rom, flash,...)中載入,也就是說，一旦在儲存裝置中找到Driver Image, 就會使用Boot Service的LoadImage(), 將Driver Image載入到System Memory. 同時該driver會生成自己的Handle，並且在該Handle下安裝EFI_LOADED_IMAGE_PROTOCOL。

typedef

EFI_STATUS

LoadImage (

  IN BOOLEAN BootPolicy,

  IN EFI_HANDLE ParentImageHandle,

  IN EFI_DEVICE_PATH_PROTOCOL *DevicePath, // The DeviceHandle specific file path from which the image is loaded.

  IN VOID *SourceBuffer OPTIONAL,

  IN UINTN SourceSize,

  OUT EFI_HANDLE *ImageHandle // Pointer to the returned image handle that is created when the image is successfully loaded.

  );

裝了EFI_LOADED_IMAGE_PROTOCOL 的Handle稱之為Image Handle。

接著，透過Boot Service的StartImage()來啟動driver，driver會在Image Handle上安裝其它的Protocol，如果是EFI Driver Model的driver，那麼會安裝EFI_DRIVER_BINDING_PROTOCOL, 如下，這時Driver Image才真正被當作Driver來處理

//

// Interface structure for the ControllerHandle Driver Protocol

//

typedef struct _EFI_DRIVER_BINDING_PROTOCOL {

  EFI_DRIVER_BINDING_SUPPORTED  Supported;

  EFI_DRIVER_BINDING_START      Start;

  EFI_DRIVER_BINDING_STOP       Stop;

  UINT32                        Version;

  EFI_HANDLE                    ImageHandle;

  EFI_HANDLE                    DriverBindingHandle;

} EFI_DRIVER_BINDING_PROTOCOL;

LoadImage()和StartImage()做完之後，driver會等待被Boot Service的ConnectController()調用(invoked)去連接到某個Controller。這時在System Memory中已經Load了很多的Driver都在等待被connect到Controller，這時ConnectController()會以Polling的方式去調用每個Driver Handle中的EFI_DRIVER_BINDING_PROTOCOL.Supported()，如果回EFI_SUCCESS，那麼該driver就會被connect到controller上。之後會透過EFI_DRIVER_BINDING_PROTOCOL.Start()來初始化以及安裝特定的Protocol到此Controller。

UEFI : PEI Phase Code Trace

$ PEI (Pre Efi Initialization)的概述:

● Small, tight startup code

• Startup with transitory memory store for call-stack (I.e., cache)       

• XIP from ROM

● Core locates, validates, and dispatches PEIMs

● Publishes own protocol and call-abstraction with PPI

• Silicon/platform abstractions

● Primary goals

• Discover boot mode       

• Launch modules that initialize main memory       

• Discovery & launch DXE core- Convey platform info into DXE

UEFI : SEC Phase Code Trace

UEFI 架構只有SEC這個phase因為是machine dependent而且cache/memory尚未初始化，所以剛開始是組合語言寫的，最主要就是做以下這幾件事:

1. 切32位元(或64位元)flat mode
2. Cache As Ram (在Flat32.asm中jump到CacheAsRam函數的位址)
3. 找BFV(Boot Firmware Volume), BFV指的是存放PEI Foundation/PEIMs的FV
4. 找到以C寫的SEC phase entry point
5. 跳到以C code寫的SEC point (SecStartup)，最後Transfer the control to the PEI core

VOID EFIAPI SecStartup (   IN UINT32    SizeOfRam,   IN UINT32    TempRamBase,   IN VOID      *BootFirmwareVolume   ) {    ... }

從上電的reset vector, trace Code如下:

進入點為 UefiCpuPkg\ResetVector\Vtf0\Ia16\ResetVectorVtf0.asm

;; Reset Vector ; ; This is where the processor will begin execution ;     nop     nop     jmp     short EarlyBspInitReal16