boot引导升级，成功引导运行loader

接上文：简单的boot引导的实现代码(内有详细注解，asm INT10的使用）_What’smean的博客-CSDN博客简单的boot引导的实现代码(内有详细注解，asm INT10的使用）https://blog.csdn.net/weixin_42492218/article/details/127665541?spm=1001.2014.3001.5501

        本文仅对boot中的内容进行更新实现引导loader的功能

        将下列代码代替原boot.asm(内涵部分注释）

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	$
 
;=======	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	$
 
;=======	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
 
;=========================
 
Label_File_Loaded:
	jmp BaseOfLoader:OffsetOfLoader
 
;=======	fill zero until whole sector
 
	times	510 - ($ - $$)	db	0
	dw	0xaa55
 
 

 其他同上文。

代码详解请看：

完整boot引导代码详解（完整无注释代码boot.asm+简单loader.asm）_What’smean的博客-CSDN博客完整boot引导代码详解（完整无注释代码boot.asm+简单loader.asm）https://blog.csdn.net/weixin_42492218/article/details/127752246

        在原有基础上添加 loader.asm(简单的显示功能）

        loader.asm内容

org 10000h
	mov ax,cs
	mov ds,ax
	mov es,ax
	mov ax,0x00
	mov ss,ax
	mov sp,0x7c00
;========== 显示 Start Loader....
	mov ax,1301h
	mov bx,000fh
	mov dx,0200h
	mov cx,12
	push ax
	mov ax,ds
	mov es,ax
	pop ax
	mov bp,StartLoaderMessage
	int 10h
	jmp $
;=============
StartLoaderMessage : db "Start Loader"		

        对loader.asm进行下列操作：

nasm loader.asm -o loader.bin

        当loader.asm程序编译结束后，必须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。此处的复制过程与boot.bin程序的写入过程采用了完全不同方法，当boot.bin程序写入到boot.img虚拟软盘镜像文件后，boot.img虚拟软盘已经拥有了FAT12文件系统，那么应该借助挂载命令mount和复制命令cp,把引导加载程序loader.bin复制到文件系统中。

        整个复制过程需要执行以下命令:

mount boot.img /media/ -t vfat -o loop 挂载 目录 -t vfat 指定磁盘文件系统
cp loader.bin /media/ 复制到文件系统
sync //强制同步命令
umount /media/ //卸载目录

然后运行引导成功即可：

具体运行请参考：在Linux下安装配置bochs，并成功跑一个简单的boot引导（超详细）_What’smean的博客-CSDN博客