《一个64位系统的设计与实现》－－BootLoader(2)

一、在boot文件中添加文件加载功能

在上一篇文章中介绍了如何制作一个简单的boot引导程序，这篇文章在此基础上加上文件加载的功能，实现完整的Boot引导功能。

本系统使用逻辑简单的FAT12文件系统来装载Loader程序和内核程序，在boot中添加FAT12文件系统的信息。具体的理论知识参考书，这里直接贴上代码和操作步骤。

将上一篇文章中的boot.asm文件用下面这段代码替代，并重新执行之后的步骤。

 org 0x7c00 
 
BaseOfStack equ 0x7c00
 
BaseOfLoader equ 0x1000
OffsetOfLoader equ 0x00
 
RootDirSectors equ 14
SectorNumOfRootDirStart equ 19
SectorNumOfFAT1Start equ 1
SectorBalance equ 17 
 
 jmp short Label_Start
 nop
 BS_OEMName db 'MINEboot'
 BPB_BytesPerSec dw 512
 BPB_SecPerClus db 1
 BPB_RsvdSecCnt dw 1
 BPB_NumFATs db 2
 BPB_RootEntCnt dw 224
 BPB_TotSec16 dw 2880
 BPB_Media db 0xf0
 BPB_FATSz16 dw 9
 BPB_SecPerTrk dw 18
 BPB_NumHeads dw 2
 BPB_HiddSec dd 0
 BPB_TotSec32 dd 0
 BS_DrvNum db 0
 BS_Reserved1 db 0
 BS_BootSig db 0x29
 BS_VolID dd 0
 BS_VolLab db 'boot loader'
 BS_FileSysType db 'FAT12   '
 
Label_Start:
 
 mov ax, cs
 mov ds, ax
 mov es, ax
 mov ss, ax
 mov sp, BaseOfStack
 
;======= clear screen
 
 mov ax, 0600h
 mov bx, 0700h
 mov cx, 0
 mov dx, 0184fh
 int 10h
 
;======= set focus
 
 mov ax, 0200h
 mov bx, 0000h
 mov dx, 0000h
 int 10h
 
;======= display on screen : Start Booting......
 
 mov ax, 1301h
 mov bx, 000fh
 mov dx, 0000h
 mov cx, 10
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, StartBootMessage
 int 10h
 
;======= reset floppy
 
 xor ah, ah
 xor dl, dl
 int 13h
 
;======= search loader.bin
 mov word [SectorNo], SectorNumOfRootDirStart
 
Lable_Search_In_Root_Dir_Begin:
 
 cmp word [RootDirSizeForLoop], 0
 jz Label_No_LoaderBin
 dec word [RootDirSizeForLoop] 
 mov ax, 00h
 mov es, ax
 mov bx, 8000h
 mov ax, [SectorNo]
 mov cl, 1
 call Func_ReadOneSector
 mov si, LoaderFileName
 mov di, 8000h
 cld
 mov dx, 10h
 
Label_Search_For_LoaderBin:
 
 cmp dx, 0
 jz Label_Goto_Next_Sector_In_Root_Dir
 dec dx
 mov cx, 11
 
Label_Cmp_FileName:
 
 cmp cx, 0
 jz Label_FileName_Found
 dec cx
 lodsb 
 cmp al, byte [es:di]
 jz Label_Go_On
 jmp Label_Different
 
Label_Go_On:
 
 inc di
 jmp Label_Cmp_FileName
 
Label_Different:
 
 and di, 0ffe0h
 add di, 20h
 mov si, LoaderFileName
 jmp Label_Search_For_LoaderBin
 
Label_Goto_Next_Sector_In_Root_Dir:
 
 add word [SectorNo], 1
 jmp Lable_Search_In_Root_Dir_Begin
 
;======= display on screen : ERROR:No LOADER Found
 
Label_No_LoaderBin:
 
 mov ax, 1301h
 mov bx, 008ch
 mov dx, 0100h
 mov cx, 21
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, NoLoaderMessage
 int 10h
 jmp BaseOfLoader:OffsetOfLoader
 
 
;======= found loader.bin name in root director struct
 
Label_FileName_Found:
 
 mov ax, RootDirSectors
 and di, 0ffe0h
 add di, 01ah
 mov cx, word [es:di]
 push cx
 add cx, ax
 add cx, SectorBalance
 mov ax, BaseOfLoader
 mov es, ax
 mov bx, OffsetOfLoader
 mov ax, cx
 
Label_Go_On_Loading_File:
 push ax
 push bx
 mov ah, 0eh
 mov al, '.'
 mov bl, 0fh
 int 10h
 pop bx
 pop ax
 
 mov cl, 1
 call Func_ReadOneSector
 pop ax
 call Func_GetFATEntry
 cmp ax, 0fffh
 jz Label_File_Loaded
 push ax
 mov dx, RootDirSectors
 add ax, dx
 add ax, SectorBalance
 add bx, [BPB_BytesPerSec]
 jmp Label_Go_On_Loading_File
 
Label_File_Loaded:
 
 jmp BaseOfLoader:OffsetOfLoader
 
;======= read one sector from floppy
 
Func_ReadOneSector:
 
 push bp
 mov bp, sp
 sub esp, 2
 mov byte [bp - 2], cl
 push bx
 mov bl, [BPB_SecPerTrk]
 div bl
 inc ah
 mov cl, ah
 mov dh, al
 shr al, 1
 mov ch, al
 and dh, 1
 pop bx
 mov dl, [BS_DrvNum]
Label_Go_On_Reading:
 mov ah, 2
 mov al, byte [bp - 2]
 int 13h
 jc Label_Go_On_Reading
 add esp, 2
 pop bp
 ret
 
;======= get FAT Entry
 
Func_GetFATEntry:
 
 push es
 push bx
 push ax
 mov ax, 00
 mov es, ax
 pop ax
 mov byte [Odd], 0
 mov bx, 3
 mul bx
 mov bx, 2
 div bx
 cmp dx, 0
 jz Label_Even
 mov byte [Odd], 1
 
Label_Even:
 
 xor dx, dx
 mov bx, [BPB_BytesPerSec]
 div bx
 push dx
 mov bx, 8000h
 add ax, SectorNumOfFAT1Start
 mov cl, 2
 call Func_ReadOneSector
 
 pop dx
 add bx, dx
 mov ax, [es:bx]
 cmp byte [Odd], 1
 jnz Label_Even_2
 shr ax, 4
 
Label_Even_2:
 and ax, 0fffh
 pop bx
 pop es
 ret
 
;======= tmp variable
 
RootDirSizeForLoop dw RootDirSectors
SectorNo  dw 0
Odd   db 0
 
;======= display messages
 
StartBootMessage: db "Start Boot"
NoLoaderMessage: db "ERROR:No LOADER Found"
LoaderFileName:  db "LOADER  BIN",0
 
;======= fill zero until whole sector
 
 times 510 - ($ - $$) db 0
 dw 0xaa55

二、制作loder文件

Loader引导加载程序负责①检测硬件信息　②处理器模式切换　③向内核传递数据　三部分工作。

首先，新建一个文件，命名为loader.asm，代码内容如下：

org 10000h
 jmp Label_Start
 
%include "fat12.inc"
 
BaseOfKernelFile equ 0x00
OffsetOfKernelFile equ 0x100000
 
BaseTmpOfKernelAddr equ 0x00
OffsetTmpOfKernelFile equ 0x7E00
 
MemoryStructBufferAddr equ 0x7E00
 
[SECTION gdt]
 
LABEL_GDT:  dd 0,0
LABEL_DESC_CODE32: dd 0x0000FFFF,0x00CF9A00
LABEL_DESC_DATA32: dd 0x0000FFFF,0x00CF9200
 
GdtLen equ $ - LABEL_GDT
GdtPtr dw GdtLen - 1
 dd LABEL_GDT
 
SelectorCode32 equ LABEL_DESC_CODE32 - LABEL_GDT
SelectorData32 equ LABEL_DESC_DATA32 - LABEL_GDT
 
[SECTION gdt64]
 
LABEL_GDT64:  dq 0x0000000000000000
LABEL_DESC_CODE64: dq 0x0020980000000000
LABEL_DESC_DATA64: dq 0x0000920000000000
 
GdtLen64 equ $ - LABEL_GDT64
GdtPtr64 dw GdtLen64 - 1
  dd LABEL_GDT64
 
SelectorCode64 equ LABEL_DESC_CODE64 - LABEL_GDT64
SelectorData64 equ LABEL_DESC_DATA64 - LABEL_GDT64
 
[SECTION .s16]
[BITS 16]
 
Label_Start:
 
 mov ax, cs
 mov ds, ax
 mov es, ax
 mov ax, 0x00
 mov ss, ax
 mov sp, 0x7c00
 
;======= display on screen : Start Loader......
 
 mov ax, 1301h
 mov bx, 000fh
 mov dx, 0200h  ;row 2
 mov cx, 12
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, StartLoaderMessage
 int 10h
 
;======= open address A20
 push ax
 in al, 92h
 or al, 00000010b
 out 92h, al
 pop ax
 
 cli
 
 db 0x66
 lgdt [GdtPtr] 
 
 mov eax, cr0
 or eax, 1
 mov cr0, eax
 
 mov ax, SelectorData32
 mov fs, ax
 mov eax, cr0
 and al, 11111110b
 mov cr0, eax
 
 sti
 
;======= reset floppy
 
 xor ah, ah
 xor dl, dl
 int 13h
 
;======= search kernel.bin
 mov word [SectorNo], SectorNumOfRootDirStart
 
Lable_Search_In_Root_Dir_Begin:
 
 cmp word [RootDirSizeForLoop], 0
 jz Label_No_LoaderBin
 dec word [RootDirSizeForLoop] 
 mov ax, 00h
 mov es, ax
 mov bx, 8000h
 mov ax, [SectorNo]
 mov cl, 1
 call Func_ReadOneSector
 mov si, KernelFileName
 mov di, 8000h
 cld
 mov dx, 10h
 
Label_Search_For_LoaderBin:
 
 cmp dx, 0
 jz Label_Goto_Next_Sector_In_Root_Dir
 dec dx
 mov cx, 11
 
Label_Cmp_FileName:
 
 cmp cx, 0
 jz Label_FileName_Found
 dec cx
 lodsb 
 cmp al, byte [es:di]
 jz Label_Go_On
 jmp Label_Different
 
Label_Go_On:
 
 inc di
 jmp Label_Cmp_FileName
 
Label_Different:
 
 and di, 0FFE0h
 add di, 20h
 mov si, KernelFileName
 jmp Label_Search_For_LoaderBin
 
Label_Goto_Next_Sector_In_Root_Dir:
 
 add word [SectorNo], 1
 jmp Lable_Search_In_Root_Dir_Begin
 
;======= display on screen : ERROR:No KERNEL Found
 
Label_No_LoaderBin:
 
 mov ax, 1301h
 mov bx, 008Ch
 mov dx, 0300h  ;row 3
 mov cx, 21
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, NoLoaderMessage
 int 10h
 jmp $
 
;======= found loader.bin name in root director struct
 
Label_FileName_Found:
 mov ax, RootDirSectors
 and di, 0FFE0h
 add di, 01Ah
 mov cx, word [es:di]
 push cx
 add cx, ax
 add cx, SectorBalance
 mov eax, BaseTmpOfKernelAddr ;BaseOfKernelFile
 mov es, eax
 mov bx, OffsetTmpOfKernelFile ;OffsetOfKernelFile
 mov ax, cx
 
Label_Go_On_Loading_File:
 push ax
 push bx
 mov ah, 0Eh
 mov al, '.'
 mov bl, 0Fh
 int 10h
 pop bx
 pop ax
 
 mov cl, 1
 call Func_ReadOneSector
 pop ax
 
;;;;;;;;;;;;;;;;;;;;;;; 
 push cx
 push eax
 push fs
 push edi
 push ds
 push esi
 
 mov cx, 200h
 mov ax, BaseOfKernelFile
 mov fs, ax
 mov edi, dword [OffsetOfKernelFileCount]
 
 mov ax, BaseTmpOfKernelAddr
 mov ds, ax
 mov esi, OffsetTmpOfKernelFile
 
Label_Mov_Kernel: ;------------------
 
 mov al, byte [ds:esi]
 mov byte [fs:edi], al
 
 inc esi
 inc edi
 
 loop Label_Mov_Kernel
 
 mov eax, 0x1000
 mov ds, eax
 
 mov dword [OffsetOfKernelFileCount], edi
 
 pop esi
 pop ds
 pop edi
 pop fs
 pop eax
 pop cx
;;;;;;;;;;;;;;;;;;;;;;; 
 
 call Func_GetFATEntry
 cmp ax, 0FFFh
 jz Label_File_Loaded
 push ax
 mov dx, RootDirSectors
 add ax, dx
 add ax, SectorBalance
 
 jmp Label_Go_On_Loading_File
 
Label_File_Loaded:
  
 mov ax, 0B800h
 mov gs, ax
 mov ah, 0Fh    ; 0000: 黑底    1111: 白字
 mov al, 'G'
 mov [gs:((80 * 0 + 39) * 2)], ax ; 屏幕第 0 行, 第 39 列。
 
KillMotor:
 
 push dx
 mov dx, 03F2h
 mov al, 0 
 out dx, al
 pop dx
 
;======= get memory address size type
 
 mov ax, 1301h
 mov bx, 000Fh
 mov dx, 0400h  ;row 4
 mov cx, 24
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, StartGetMemStructMessage
 int 10h
 
 mov ebx, 0
 mov ax, 0x00
 mov es, ax
 mov di, MemoryStructBufferAddr 
 
Label_Get_Mem_Struct:
 
 mov eax, 0x0E820
 mov ecx, 20
 mov edx, 0x534D4150
 int 15h
 jc Label_Get_Mem_Fail
 add di, 20
 
 cmp ebx, 0
 jne Label_Get_Mem_Struct
 jmp Label_Get_Mem_OK
 
Label_Get_Mem_Fail:
 
 mov ax, 1301h
 mov bx, 008Ch
 mov dx, 0500h  ;row 5
 mov cx, 23
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, GetMemStructErrMessage
 int 10h
 jmp $
 
Label_Get_Mem_OK:
 
 mov ax, 1301h
 mov bx, 000Fh
 mov dx, 0600h  ;row 6
 mov cx, 29
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, GetMemStructOKMessage
 int 10h 
 
;======= get SVGA information
 
 mov ax, 1301h
 mov bx, 000Fh
 mov dx, 0800h  ;row 8
 mov cx, 23
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, StartGetSVGAVBEInfoMessage
 int 10h
 
 mov ax, 0x00
 mov es, ax
 mov di, 0x8000
 mov ax, 4F00h
 
 int 10h
 
 cmp ax, 004Fh
 
 jz .KO
 
;======= Fail
 
 mov ax, 1301h
 mov bx, 008Ch
 mov dx, 0900h  ;row 9
 mov cx, 23
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, GetSVGAVBEInfoErrMessage
 int 10h
 
 jmp $
 
.KO:
 
 mov ax, 1301h
 mov bx, 000Fh
 mov dx, 0A00h  ;row 10
 mov cx, 29
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, GetSVGAVBEInfoOKMessage
 int 10h
 
;======= Get SVGA Mode Info
 
 mov ax, 1301h
 mov bx, 000Fh
 mov dx, 0C00h  ;row 12
 mov cx, 24
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, StartGetSVGAModeInfoMessage
 int 10h
 
 
 mov ax, 0x00
 mov es, ax
 mov si, 0x800e
 
 mov esi, dword [es:si]
 mov edi, 0x8200
 
Label_SVGA_Mode_Info_Get:
 
 mov cx, word [es:esi]
 
;======= display SVGA mode information
 
 push ax
 
 mov ax, 00h
 mov al, ch
 call Label_DispAL
 
 mov ax, 00h
 mov al, cl 
 call Label_DispAL
 
 pop ax
 
;=======
 
 cmp cx, 0FFFFh
 jz Label_SVGA_Mode_Info_Finish
 
 mov ax, 4F01h
 int 10h
 
 cmp ax, 004Fh
 
 jnz Label_SVGA_Mode_Info_FAIL 
 
 add esi, 2
 add edi, 0x100
 
 jmp Label_SVGA_Mode_Info_Get
  
Label_SVGA_Mode_Info_FAIL:
 
 mov ax, 1301h
 mov bx, 008Ch
 mov dx, 0D00h  ;row 13
 mov cx, 24
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, GetSVGAModeInfoErrMessage
 int 10h
 
Label_SET_SVGA_Mode_VESA_VBE_FAIL:
 
 jmp $
 
Label_SVGA_Mode_Info_Finish:
 
 mov ax, 1301h
 mov bx, 000Fh
 mov dx, 0E00h  ;row 14
 mov cx, 30
 push ax
 mov ax, ds
 mov es, ax
 pop ax
 mov bp, GetSVGAModeInfoOKMessage
 int 10h
 
;======= set the SVGA mode(VESA VBE)
 
 mov ax, 4F02h
 mov bx, 4180h ;========================mode : 0x180 or 0x143
 int  10h
 
 cmp ax, 004Fh
 jnz Label_SET_SVGA_Mode_VESA_VBE_FAIL
 
;======= init IDT GDT goto protect mode 
 
 cli   ;======close interrupt
 
 db 0x66
 lgdt [GdtPtr]
 
; db 0x66
; lidt [IDT_POINTER]
 
 mov eax, cr0
 or eax, 1
 mov cr0, eax 
 
 jmp dword SelectorCode32:GO_TO_TMP_Protect
 
[SECTION .s32]
[BITS 32]
 
GO_TO_TMP_Protect:
 
;======= go to tmp long mode
 
 mov ax, 0x10
 mov ds, ax
 mov es, ax
 mov fs, ax
 mov ss, ax
 mov esp, 7E00h
 
 call support_long_mode
 test eax, eax
 
 jz no_support
 
;======= init temporary page table 0x90000
 
 mov dword [0x90000], 0x91007
 mov dword [0x90800], 0x91007  
 
 mov dword [0x91000], 0x92007
 
 mov dword [0x92000], 0x000083
 
 mov dword [0x92008], 0x200083
 
 mov dword [0x92010], 0x400083
 
 mov dword [0x92018], 0x600083
 
 mov dword [0x92020], 0x800083
 
 mov dword [0x92028], 0xa00083
 
;======= load GDTR
 
 db 0x66
 lgdt [GdtPtr64]
 mov ax, 0x10
 mov ds, ax
 mov es, ax
 mov fs, ax
 mov gs, ax
 mov ss, ax
 
 mov esp, 7E00h
 
;======= open PAE
 
 mov eax, cr4
 bts eax, 5
 mov cr4, eax
 
;======= load cr3
 
 mov eax, 0x90000
 mov cr3, eax
 
;======= enable long-mode
 
 mov ecx, 0C0000080h  ;IA32_EFER
 rdmsr
 
 bts eax, 8
 wrmsr
 
;======= open PE and paging
 
 mov eax, cr0
 bts eax, 0
 bts eax, 31
 mov cr0, eax
 
 jmp SelectorCode64:OffsetOfKernelFile
 
;======= test support long mode or not
 
support_long_mode:
 
 mov eax, 0x80000000
 cpuid
 cmp eax, 0x80000001
 setnb al 
 jb support_long_mode_done
 mov eax, 0x80000001
 cpuid
 bt edx, 29
 setc al
support_long_mode_done:
 
 movzx eax, al
 ret
 
;======= no support
 
no_support:
 jmp $
 
;======= read one sector from floppy
 
[SECTION .s16lib]
[BITS 16]
 
Func_ReadOneSector:
 
 push bp
 mov bp, sp
 sub esp, 2
 mov byte [bp - 2], cl
 push bx
 mov bl, [BPB_SecPerTrk]
 div bl
 inc ah
 mov cl, ah
 mov dh, al
 shr al, 1
 mov ch, al
 and dh, 1
 pop bx
 mov dl, [BS_DrvNum]
Label_Go_On_Reading:
 mov ah, 2
 mov al, byte [bp - 2]
 int 13h
 jc Label_Go_On_Reading
 add esp, 2
 pop bp
 ret
 
;======= get FAT Entry
 
Func_GetFATEntry:
 
 push es
 push bx
 push ax
 mov ax, 00
 mov es, ax
 pop ax
 mov byte [Odd], 0
 mov bx, 3
 mul bx
 mov bx, 2
 div bx
 cmp dx, 0
 jz Label_Even
 mov byte [Odd], 1
 
Label_Even:
 
 xor dx, dx
 mov bx, [BPB_BytesPerSec]
 div bx
 push dx
 mov bx, 8000h
 add ax, SectorNumOfFAT1Start
 mov cl, 2
 call Func_ReadOneSector
 
 pop dx
 add bx, dx
 mov ax, [es:bx]
 cmp byte [Odd], 1
 jnz Label_Even_2
 shr ax, 4
 
Label_Even_2:
 and ax, 0FFFh
 pop bx
 pop es
 ret
 
;======= display num in al
 
Label_DispAL:
 
 push ecx
 push edx
 push edi
 
 mov edi, [DisplayPosition]
 mov ah, 0Fh
 mov dl, al
 shr al, 4
 mov ecx, 2
.begin:
 
 and al, 0Fh
 cmp al, 9
 ja .1
 add al, '0'
 jmp .2
.1:
 
 sub al, 0Ah
 add al, 'A'
.2:
 
 mov [gs:edi], ax
 add edi, 2
 
 mov al, dl
 loop .begin
 
 mov [DisplayPosition], edi
 
 pop edi
 pop edx
 pop ecx
 
 ret
 
 
;======= tmp IDT
 
IDT:
 times 0x50 dq 0
IDT_END:
 
IDT_POINTER:
  dw IDT_END - IDT - 1
  dd IDT
 
;======= tmp variable
 
RootDirSizeForLoop dw RootDirSectors
SectorNo  dw 0
Odd   db 0
OffsetOfKernelFileCount dd OffsetOfKernelFile
 
DisplayPosition  dd 0
 
;======= display messages
 
StartLoaderMessage: db "Start Loader"
NoLoaderMessage: db "ERROR:No KERNEL Found"
KernelFileName:  db "KERNEL  BIN",0
StartGetMemStructMessage: db "Start Get Memory Struct."
GetMemStructErrMessage: db "Get Memory Struct ERROR"
GetMemStructOKMessage: db "Get Memory Struct SUCCESSFUL!"
 
StartGetSVGAVBEInfoMessage: db "Start Get SVGA VBE Info"
GetSVGAVBEInfoErrMessage: db "Get SVGA VBE Info ERROR"
GetSVGAVBEInfoOKMessage: db "Get SVGA VBE Info SUCCESSFUL!"
 
StartGetSVGAModeInfoMessage: db "Start Get SVGA Mode Info"
GetSVGAModeInfoErrMessage: db "Get SVGA Mode Info ERROR"
GetSVGAModeInfoOKMessage: db "Get SVGA Mode Info SUCCESSFUL!"

该段程序中加载了一个fat12.inc的文件，该文件包含了FAT12系统的基本信息。在loader.asm同一路径下新建一个文件fat12.inc，文件内容如下。

RootDirSectors equ 14
SectorNumOfRootDirStart equ 19
SectorNumOfFAT1Start equ 1
SectorBalance equ 17 
 
 BS_OEMName db 'MINEboot'
 BPB_BytesPerSec dw 512
 BPB_SecPerClus db 1
 BPB_RsvdSecCnt dw 1
 BPB_NumFATs db 2
 BPB_RootEntCnt dw 224
 BPB_TotSec16 dw 2880
 BPB_Media db 0xf0
 BPB_FATSz16 dw 9
 BPB_SecPerTrk dw 18
 BPB_NumHeads dw 2
 BPB_hiddSec dd 0
 BPB_TotSec32 dd 0
 BS_DrvNum db 0
 BS_Reserved1 db 0
 BS_BootSig db 29h
 BS_VolID dd 0
 BS_VolLab db 'boot loader'
 BS_FileSysType db 'FAT12   '

之后编译loader.asm文件，编译命令为：　　nasm loader.asm -o loader.bin

编译结束后，将生成的二进制程序loader.bin 复制到虚拟软盘镜像文件boot.img中。由于此时的boot.img已经有了FAT12文件系统，所以现在可以使用挂载文件系统的方式将loader.bin 复制到文件系统中。依次执行：

mount (bochs路径)/boot.img /media/ -t vfat -o loop
cp loader.bin /media/
sync
umount /media/

执行之后，即可如上一篇中所述运行bochs，运行后界面如下，由于现在还没有转到内核中，会显示找不到内核文件的错误。

《一个64位系统的设计与实现》－－BootLoader(2)

一、在boot文件中添加文件加载功能

二、制作loder文件

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