xOS.nas

; xOS
; TAB=4
[INSTRSET "i486p"]

VBEMODE	EQU		0x105

BOTPAK	EQU		0x00280000
DSKCAC	EQU		0x00100000
DSKCAC0	EQU		0x00008000

; 有关BOOT_INFO
CYLS	EQU		0x0ff0			; 设定启动区
LEDS	EQU		0x0ff1
VMODE	EQU		0x0ff2			; 颜色位数
SCRNX	EQU		0x0ff4			; 分辨率的X
SCRNY	EQU		0x0ff6			; 分辨率的Y
VRAM	EQU		0x0ff8			; 图像缓冲区的开始地址

		ORG		0xc200			; 程序装载内存地址

; VBE确认是否存在

		MOV		AX,0x9000
		MOV		ES,AX
		MOV		DI,0
		MOV		AX,0x4f00
		INT		0x10
		CMP		AX,0x004f
		JNE		scrn320

		MOV		AX,[ES:DI+4]
		CMP		AX,0x0200
		JB		scrn320			; if (AX < 0x0200) goto scrn320

		MOV		CX,VBEMODE
		MOV		AX,0x4f01
		INT		0x10
		CMP		AX,0x004f
		JNE		scrn320

		CMP		BYTE [ES:DI+0x19],8
		JNE		scrn320
		CMP		BYTE [ES:DI+0x1b],4
		JNE		scrn320
		MOV		AX,[ES:DI+0x00]
		AND		AX,0x0080
		JZ		scrn320

		MOV		BX,VBEMODE+0x4000
		MOV		AX,0x4f02
		INT		0x10
		MOV		BYTE [VMODE],8		; 记录画面
		MOV		AX,[ES:DI+0x12]
		MOV		[SCRNX],AX
		MOV		AX,[ES:DI+0x14]
		MOV		[SCRNY],AX
		MOV		EAX,[ES:DI+0x28]
		MOV		[VRAM],EAX
		JMP		keystatus

scrn320:
		MOV		AL,0x13			; ; VGA显卡320*200*8位色彩
		MOV		AH,0x00
		INT		0x10
		MOV		BYTE [VMODE],8	; 画面モードをメモする（C言語が参照する）
		MOV		WORD [SCRNX],320
		MOV		WORD [SCRNY],200
		MOV		DWORD [VRAM],0x000a0000

; 用BIOS取得键盘上的各种LED指示灯的状态
keystatus:
		MOV		AH,0x02
		INT		0x16 			; keyboard BIOS
		MOV		[LEDS],AL

        MOV		AL,0xff
		OUT		0x21,AL
		NOP						
		OUT		0xa1,AL

		CLI						

		CALL	waitkbdout
		MOV		AL,0xd1
		OUT		0x64,AL
		CALL	waitkbdout
		MOV		AL,0xdf			
		OUT		0x60,AL
		CALL	waitkbdout
			

		LGDT	[GDTR0]			
		MOV		EAX,CR0
		AND		EAX,0x7fffffff	
		OR		EAX,0x00000001	
		MOV		CR0,EAX
		JMP		pipelineflush
pipelineflush:
		MOV		AX,1*8			
		MOV		DS,AX
		MOV		ES,AX
		MOV		FS,AX
		MOV		GS,AX
		MOV		SS,AX

		MOV		ESI,bootpack	
		MOV		EDI,BOTPAK		
		MOV		ECX,512*1024/4
		CALL	memcpy

		MOV		ESI,0x7c00		
		MOV		EDI,DSKCAC		
		MOV		ECX,512/4
		CALL	memcpy



		MOV		ESI,DSKCAC0+512	
		MOV		EDI,DSKCAC+512	
		MOV		ECX,0
		MOV		CL,BYTE [CYLS]
		IMUL	ECX,512*18*2/4	
		SUB		ECX,512/4		
		CALL	memcpy


; bootpack

		MOV		EBX,BOTPAK
		MOV		ECX,[EBX+16]
		ADD		ECX,3			; ECX += 3;
		SHR		ECX,2			; ECX /= 4;
		JZ		skip			
		MOV		ESI,[EBX+20]	
		ADD		ESI,EBX
		MOV		EDI,[EBX+12]	
		CALL	memcpy
skip:
		MOV		ESP,[EBX+12]	
		JMP		DWORD 2*8:0x0000001b

waitkbdout:
		IN		 AL,0x64
		AND		 AL,0x02
		JNZ		waitkbdout		
		RET

memcpy:
		MOV		EAX,[ESI]
		ADD		ESI,4
		MOV		[EDI],EAX
		ADD		EDI,4
		SUB		ECX,1
		JNZ		memcpy			
		RET


		ALIGNB	16
GDT0:
		RESB	8				
		DW		0xffff,0x0000,0x9200,0x00cf	
		DW		0xffff,0x0000,0x9a28,0x0047	

		DW		0
GDTR0:
		DW		8*3-1
		DD		GDT0

		ALIGNB	16
bootpack: