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duck-os

基于scheme写的os

使用

编译

提前安装 bochs

./configure --with-sdl --enable-disasm --enable-all-optimizations --enable-readline  --disable-debugger-gui --enable-x86-debugger --enable-a20-pin --enable-fast-function-calls --enable-debugger

编译

mkdir build
make

运行镜像

make run

文档

目录结构

boot.ss    加载loader到内存中，跳转到init
init.ss 加载内核到内存中，进入保护模式，跳转到内核
kernel.ss 内核文件

BIOS 基本功能

显示相关

INT 10h

  1. 设置光标位置 AH=02H BH=页码，DH=列，DL=行

  2. 清除屏幕 AH=06H AL=滚动的行（0=清除，被用于CH，CL，DH，DL）， BH=背景颜色和前景颜色，BH=43H，意义为背景颜色为红色，前景颜色为青色。请参考BIOS颜色属性。 CH=高行数，CL=左列数，DH=低行数，DL=右列数

颜色显示
二进制数	颜色	例子	二进制数	颜色	例子
0000	黑色	black	1000	灰色	gray
0001	蓝色	blue	1001	淡蓝色	light blue
0010	绿色	green	1010	淡绿色	light green
0011	青色	cyan	1000	淡青色	light cyan
0100	红色	red	1100	淡红色	light red
0101	紫红色	magenta	1101	淡紫红色	light magenta
0110	棕色	brown	1110	黄色	yellow
0111	银色	light gray	1111	白色	white

磁盘相关

INT 13h

  1. 复位 AH 00h DL Drive (bit 7 set means reset both hard and floppy disks)
DL = 00h	1st floppy disk ( "drive A:" )
DL = 01h	2nd floppy disk ( "drive B:" )
DL = 02h	3rd floppy disk ( "drive B:" )
. . .
DL = 7Fh	128th floppy disk)
DL = 80h	1st hard disk
DL = 81h	2nd hard disk
DL = 82h	3rd hard disk
. . .
DL = E0h	CD/DVD[citation needed], or 97th hard disk
. . .
DL = FFh	128th hard disk
  1. 读取一个扇区 AH=02h: Read Sectors From Drive
AH	02h
AL	Sectors To Read Count
CH	Cylinder
CL	Sector
DH	Head
DL	Drive
ES:BX	Buffer Address Pointer
Results
CF	Set On Error, Clear If No Error
AH	Return Code
AL	Actual Sectors Read Count

保护模式

GDT（Global Descriptor Table，全局描述符表） LDT (Local Descriptor Table，局部描述符表)

GDT的每个表项，抽象地可以看成包含四个字段的数据结构：基地址（Base），大小（Limit），标志（Flag），访问信息（Access Byte）。

GDT
1st Double word:
Bits	Function	Description
0-15	Limit 0:15	First 16 bits in the segment limiter
16-31	Base 0:15	First 16 bits in the base address

2nd Double word:
Bits	Function	Description
0-7	Base 16:23	Bits 16-23 in the base address
8-12	Type	Segment type and attributes
13-14	Privilege Level	0 = Highest privilege (OS), 3 = Lowest privilege (User applications)
15	Present flag	Set to 1 if segment is present
16-19	Limit 16:19	Bits 16-19 in the segment limiter
20-22	Attributes	Different attributes, depending on the segment type
23	Granularity	Used together with the limiter, to determine the size of the segment
24-31	Base 24:31	The last 24-31 bits in the base address


The GDT Descriptor
Bits	Function	Description
0-15	Limit	Size of GDT in bytes
16-47	Address	GDT's memory address

分页

无分页模式

    线性地址等于物理地址
    CR0.PG = 0

32bit模式

    CR0.PG = 1 and CR4.PAE = 0
    0-11:  页内偏移
    12-21: 页表 (Page Table)
    22-31: 页表目录表（Page Table Directory

PAE模式

    CR0.PG = 1, CR4.PAE = 1, and IA32_EFER.LME = 0
    0-11：页内偏移
    12-20：页表（Page Table）                          PT   PTE 512个
    21-29：页表目录表（Page Table Directory）           PTD  PDE 512个
    30-31：页目录指针表（Page Directory Pointer Table） PDPT PDPTE 4个

    CR3=>31:30
    PDPTE=>29:21
    PDE=> 20:12

内存地址

    0x0500  init
    0x4000 page entry
    0x7c00 boot
    0x8000 kernel

任务切换

TSS 任务状态段

x86 Structure
offset	0 - 15	16 - 31
0x00	LINK	reserved
0x04	ESP0
0x08	SS0	reserved
0x0C	ESP1
0x10	SS1	reserved
0x14	ESP2
0x18	SS2	reserved
0x1C	CR3
0x20	EIP
0x24	EFLAGS
0x28	EAX
0x2C	ECX
0x30	EDX
0x34	EBX
0x38	ESP
0x3C	EBP
0x40	ESI
0x44	EDI
0x48	ES	reserved
0x4C	CS	reserved
0x50	SS	reserved
0x54	DS	reserved
0x58	FS	reserved
0x5C	GS	reserved
0x60	LDTR	reserved
0x64	reserved	IOPB offset

save esp ,eip restore esp ,eip

参考

https://en.wikipedia.org/wiki/INT_10H
https://en.wikipedia.org/wiki/INT_13H
https://stanislavs.org/helppc/int_13-1.html https://baike.baidu.com/item/INT10H/22788179?fr=aladdin https://wiki.osdev.org/GDT_Tutorial http://www.osdever.net/tutorials/view/the-world-of-protected-mode https://files.osdev.org/mirrors/geezer/os/pm.htm https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-3a-part-1-manual.html https://wiki.osdev.org/Task_State_Segment https://wiki.osdev.org/Memory_Map_(x86) http://www.uruk.org/orig-grub/mem64mb.html https://wiki.osdev.org/Detecting_Memory_(x86) https://zh.wikipedia.org/wiki/%E5%85%A8%E5%B1%80%E6%8F%8F%E8%BF%B0%E7%AC%A6%E8%A1%A8