挑战30天写操作系统-day4-C语言与画面显示的练习

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C语言中如果使用了write_mem8函数，就会跳转到_write_mem8,此时参数指定的数字就存放在内存里，分别是：

我们想要取得参数指定的数字0x1234或者0x56内容，只需要用MOV指令读入寄存器即可。


naskfunc.nas代码

; naskfunc
; TAB=4

[FORMAT "WCOFF"]				; 制作目标文件的模式	
[INSTRSET "i486p"]				; 使用到486为止的指令
[BITS 32]						; 3制作32位模式用的机器语言
[FILE "naskfunc.nas"]			; 文件名

		GLOBAL	_io_hlt, _io_cli, _io_sti, _io_stihlt
		GLOBAL	_io_in8,  _io_in16,  _io_in32
		GLOBAL	_io_out8, _io_out16, _io_out32
		GLOBAL	_io_load_eflags, _io_store_eflags

[SECTION .text]

_io_hlt:	; void io_hlt(void);
		HLT
		RET

_io_cli:	; void io_cli(void);
		CLI
		RET

_io_sti:	; void io_sti(void);
		STI
		RET

_io_stihlt:	; void io_stihlt(void);
		STI
		HLT
		RET

_io_in8:	; int io_in8(int port);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,0
		IN		AL,DX
		RET

_io_in16:	; int io_in16(int port);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,0
		IN		AX,DX
		RET

_io_in32:	; int io_in32(int port);
		MOV		EDX,[ESP+4]		; port
		IN		EAX,DX
		RET

_io_out8:	; void io_out8(int port, int data);
		MOV		EDX,[ESP+4]		; port
		MOV		AL,[ESP+8]		; data
		OUT		DX,AL
		RET

_io_out16:	; void io_out16(int port, int data);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,[ESP+8]		; data
		OUT		DX,AX
		RET

_io_out32:	; void io_out32(int port, int data);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,[ESP+8]		; data
		OUT		DX,EAX
		RET

_io_load_eflags:	; int io_load_eflags(void);
		PUSHFD		; PUSH EFLAGS 
		POP		EAX
		RET

_io_store_eflags:	; void io_store_eflags(int eflags);
		MOV		EAX,[ESP+4]
		PUSH	EAX
		POPFD		; POP EFLAGS 
		RET

下面修改C语言，这次导入变量

bootpack.c代码

void io_hlt(void);
void io_cli(void);
void io_out8(int port, int data);
int io_load_eflags(void);
void io_store_eflags(int eflags);

void init_palette(void);
void set_palette(int start, int end, unsigned char *rgb);
void boxfill8(unsigned char *vram, int xsize, unsigned char c, int x0, int y0, int x1, int y1);

#define COL8_000000		0
#define COL8_FF0000		1
#define COL8_00FF00		2
#define COL8_FFFF00		3
#define COL8_0000FF		4
#define COL8_FF00FF		5
#define COL8_00FFFF		6
#define COL8_FFFFFF		7
#define COL8_C6C6C6		8
#define COL8_840000		9
#define COL8_008400		10
#define COL8_848400		11
#define COL8_000084		12
#define COL8_840084		13
#define COL8_008484		14
#define COL8_848484		15

void HariMain(void)
{
	char *vram;
	int xsize, ysize;

	init_palette();
	vram = (char *) 0xa0000;
	xsize = 320;
	ysize = 200;

	
	boxfill8(vram, xsize, COL8_008484,  0,         0,          xsize -  1, ysize - 29);
	boxfill8(vram, xsize, COL8_C6C6C6,  0,         ysize - 28, xsize -  1, ysize - 28);
	boxfill8(vram, xsize, COL8_FFFFFF,  0,         ysize - 27, xsize -  1, ysize - 27);
	boxfill8(vram, xsize, COL8_C6C6C6,  0,         ysize - 26, xsize -  1, ysize -  1);

	boxfill8(vram, xsize, COL8_FFFFFF,  3,         ysize - 24, 59,         ysize - 24);
	boxfill8(vram, xsize, COL8_FFFFFF,  2,         ysize - 24,  2,         ysize -  4);
	boxfill8(vram, xsize, COL8_848484,  3,         ysize -  4, 59,         ysize -  4);
	boxfill8(vram, xsize, COL8_848484, 59,         ysize - 23, 59,         ysize -  5);
	boxfill8(vram, xsize, COL8_000000,  2,         ysize -  3, 59,         ysize -  3);
	boxfill8(vram, xsize, COL8_000000, 60,         ysize - 24, 60,         ysize -  3);

	boxfill8(vram, xsize, COL8_848484, xsize - 47, ysize - 24, xsize -  4, ysize - 24);
	boxfill8(vram, xsize, COL8_848484, xsize - 47, ysize - 23, xsize - 47, ysize -  4);
	boxfill8(vram, xsize, COL8_FFFFFF, xsize - 47, ysize -  3, xsize -  4, ysize -  3);
	boxfill8(vram, xsize, COL8_FFFFFF, xsize -  3, ysize - 24, xsize -  3, ysize -  3);

	for (;;) {
		io_hlt();
	}
}

void init_palette(void)
{
	static unsigned char table_rgb[16 * 3] = {
		0x00, 0x00, 0x00,	
		0xff, 0x00, 0x00,	
		0x00, 0xff, 0x00,	
		0xff, 0xff, 0x00,	
		0x00, 0x00, 0xff,	
		0xff, 0x00, 0xff,	
		0x00, 0xff, 0xff,	
		0xff, 0xff, 0xff,	
		0xc6, 0xc6, 0xc6,	
		0x84, 0x00, 0x00,	
		0x00, 0x84, 0x00,	
		0x84, 0x84, 0x00,	
		0x00, 0x00, 0x84,	
		0x84, 0x00, 0x84,	
		0x00, 0x84, 0x84,	
		0x84, 0x84, 0x84	
	};
	set_palette(0, 15, table_rgb);
	return;

	
}

void set_palette(int start, int end, unsigned char *rgb)
{
	int i, eflags;
	eflags = io_load_eflags();	
	io_cli(); 					
	io_out8(0x03c8, start);
	for (i = start; i <= end; i++) {
		io_out8(0x03c9, rgb[0] / 4);
		io_out8(0x03c9, rgb[1] / 4);
		io_out8(0x03c9, rgb[2] / 4);
		rgb += 3;
	}
	io_store_eflags(eflags);	
	return;
}

void boxfill8(unsigned char *vram, int xsize, unsigned char c, int x0, int y0, int x1, int y1)
{
	int x, y;
	for (y = y0; y <= y1; y++) {
		for (x = x0; x <= x1; x++)
			vram[y * xsize + x] = c;
	}
	return;
}

原来书籍中代码较为简单运行后是白屏，没有参考价值，修改代码如上
下面执行make run或者make install为白屏

改动上述代码

CPU采用数值运算时，将会进行加减乘除，重要的是计算结果。而对图像进行处理时，更重要的是0和1的排列顺序，经常需要进行反转操作，如下

接下来运行

以下色号足够了

相关代码前面已经说明了。

总结一下
下面介绍标志寄存器


接下来说naskfunc.nas

; naskfunc
; TAB=4

[FORMAT "WCOFF"]				; 制作目标文件的模式	
[INSTRSET "i486p"]				; 使用到486为止的指令
[BITS 32]						; 3制作32位模式用的机器语言
[FILE "naskfunc.nas"]			; 文件名

		GLOBAL	_io_hlt, _io_cli, _io_sti, _io_stihlt
		GLOBAL	_io_in8,  _io_in16,  _io_in32
		GLOBAL	_io_out8, _io_out16, _io_out32
		GLOBAL	_io_load_eflags, _io_store_eflags

[SECTION .text]

_io_hlt:	; void io_hlt(void);
		HLT
		RET

_io_cli:	; void io_cli(void);
		CLI
		RET

_io_sti:	; void io_sti(void);
		STI
		RET

_io_stihlt:	; void io_stihlt(void);
		STI
		HLT
		RET

_io_in8:	; int io_in8(int port);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,0
		IN		AL,DX
		RET

_io_in16:	; int io_in16(int port);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,0
		IN		AX,DX
		RET

_io_in32:	; int io_in32(int port);
		MOV		EDX,[ESP+4]		; port
		IN		EAX,DX
		RET

_io_out8:	; void io_out8(int port, int data);
		MOV		EDX,[ESP+4]		; port
		MOV		AL,[ESP+8]		; data
		OUT		DX,AL
		RET

_io_out16:	; void io_out16(int port, int data);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,[ESP+8]		; data
		OUT		DX,AX
		RET

_io_out32:	; void io_out32(int port, int data);
		MOV		EDX,[ESP+4]		; port
		MOV		EAX,[ESP+8]		; data
		OUT		DX,EAX
		RET

_io_load_eflags:	; int io_load_eflags(void);
		PUSHFD		; PUSH EFLAGS 
		POP		EAX
		RET

_io_store_eflags:	; void io_store_eflags(int eflags);
		MOV		EAX,[ESP+4]
		PUSH	EAX
		POPFD		; POP EFLAGS 
		RET

运行