实验
预备工作-8259A初始化，读写IMR寄存器，发送EOI控制字等
1.自定义软中断的实现(内部中断处理)
2.时钟中断的响应及处理
需要编写的函数
1.编写延迟函数
2.编写8259A初始化函数
3.编写8259A中断屏蔽寄存器读写函数
4.编写8259A中断结束符写入函数
读写IMR寄存器-使用OCW1设置IMR的目标值，同时写入对应端口(0x21或0xA1)
在这里需要知道的是，汇编语言中支持预处理语句，与C语言相似，汇编预处理语句常用于文本替换，如下图所示
实验一
1.自定义保护模式下的软中断(0x80)
2.0x80中断使用后，在屏幕下打印字符串
实现的思路-编写中断程序-创建中断描述符-加载中断描述符表-通过int指令触发软中断，需要注意的是x86处理器一共支持256个中断类型，因此中断描述符表中需要有256个描述符与之对应
设置过程
%include "inc.asm"
org 0x9000
jmp ENTRY_SEGMENT
[section .gdt]
; GDT definition
; 段基址， 段界限， 段属性
GDT_ENTRY : Descriptor 0, 0, 0
CODE32_DESC : Descriptor 0, Code32SegLen - 1, DA_C + DA_32
VIDEO_DESC : Descriptor 0xB8000, 0x07FFF, DA_DRWA + DA_32
DATA32_DESC : Descriptor 0, Data32SegLen - 1, DA_DRW + DA_32
STACK32_DESC : Descriptor 0, TopOfStack32, DA_DRW + DA_32
; GDT end
GdtLen equ $ - GDT_ENTRY
GdtPtr:
dw GdtLen - 1
dd 0
; GDT Selector
Code32Selector equ (0x0001 << 3) + SA_TIG + SA_RPL0
VideoSelector equ (0x0002 << 3) + SA_TIG + SA_RPL0
Data32Selector equ (0x0003 << 3) + SA_TIG + SA_RPL0
Stack32Selector equ (0x0004 << 3) + SA_TIG + SA_RPL0
; end of [section .gdt]
[section .idt]
align 32
[bits 32]
IDT_ENTRY:
; IDT definition
; Selector, Offset, DCount, Attribute
%rep 128
Gate Code32Selector, DefaultHandler, 0, DA_386IGate
%endrep
Int0x80 : Gate Code32Selector, Int0x80Handler, 0, DA_386IGate
%rep 127
Gate Code32Selector, DefaultHandler, 0, DA_386IGate
%endrep
IdtLen equ $ - IDT_ENTRY
IdtPtr:
dw IdtLen - 1
dd 0
; end of [section .idt]
TopOfStack16 equ 0x7c00
[section .dat]
[bits 32]
DATA32_SEGMENT:
DTOS db "D.T.OS!", 0
DTOS_OFFSET equ DTOS - $$
INT_80H db "int 0x80", 0
INT_80H_OFFSET equ INT_80H - $$
Data32SegLen equ $ - DATA32_SEGMENT
[section .s16]
[bits 16]
ENTRY_SEGMENT:
mov ax, cs
mov ds, ax
mov es, ax
mov ss, ax
mov sp, TopOfStack16
; initialize GDT for 32 bits code segment
mov esi, CODE32_SEGMENT
mov edi, CODE32_DESC
call InitDescItem
mov esi, DATA32_SEGMENT
mov edi, DATA32_DESC
call InitDescItem
mov esi, STACK32_SEGMENT
mov edi, STACK32_DESC
call InitDescItem
; initialize GDT pointer struct
mov eax, 0
mov ax, ds
shl eax, 4
add eax, GDT_ENTRY
mov dword [GdtPtr + 2], eax
; initialize IDT pointer struct
mov eax, 0
mov ax, ds
shl eax, 4
add eax, IDT_ENTRY
mov dword [IdtPtr + 2], eax
; 1. load GDT
lgdt [GdtPtr]
; 2. close interrupt and load IDT
cli
lidt [IdtPtr]
; 3. open A20
in al, 0x92
or al, 00000010b
out 0x92, al
; 4. enter protect mode
mov eax, cr0
or eax, 0x01
mov cr0, eax
; 5. jump to 32 bits code
jmp dword Code32Selector : 0
; esi --> code segment label
; edi --> descriptor label
InitDescItem:
push eax
mov eax, 0
mov ax, cs
shl eax, 4
add eax, esi
mov word [edi + 2], ax
shr eax, 16
mov byte [edi + 4], al
mov byte [edi + 7], ah
pop eax
ret
[section .s32]
[bits 32]
CODE32_SEGMENT:
mov ax, VideoSelector
mov gs, ax
mov ax, Stack32Selector
mov ss, ax
mov eax, TopOfStack32
mov esp, eax
mov ax, Data32Selector
mov ds, ax
call Init8259A
mov ax, 0xFF
mov dx, MASTER_IMR_PORT
call WriteIMR
mov ax, 0xFF
mov dx, SLAVE_IMR_PORT
call WriteIMR
mov ebp, DTOS_OFFSET
mov bx, 0x0C
mov dh, 12
mov dl, 33
call PrintString
mov ebp, INT_80H_OFFSET
mov bx, 0x0C
mov dh, 13
mov dl, 32
int 0x80
jmp $
;
;
Delay:
%rep 5
nop
%endrep
ret
;
;
Init8259A:
push ax
; master
; ICW1
mov al, 00010001B
out MASTER_ICW1_PORT, al
call Delay
; ICW2
mov al, 0x20
out MASTER_ICW2_PORT, al
call Delay
; ICW3
mov al, 00000100B
out MASTER_ICW3_PORT, al
call Delay
; ICW4
mov al, 00010001B
out MASTER_ICW4_PORT, al
call Delay
; slave
; ICW1
mov al, 00010001B
out SLAVE_ICW1_PORT, al
call Delay
; ICW2
mov al, 0x28
out SLAVE_ICW2_PORT, al
call Delay
; ICW3
mov al, 00000010B
out SLAVE_ICW3_PORT, al
call Delay
; ICW4
mov al, 00000001B
out SLAVE_ICW4_PORT, al
call Delay
pop ax
ret
; al --> IMR register value
; dx --> 8259A port
WriteIMR:
out dx, al
call Delay
ret
; dx --> 8259A
; return:
; ax --> IMR register value
ReadIMR:
in ax, dx
call Delay
ret
;
; dx --> 8259A port
WriteEOI:
push ax
mov al, 0x20
out dx, al
call Delay
pop ax
ret
;
;
DefaultHandlerFunc:;默认中断程序直接返回
iret
DefaultHandler equ DefaultHandlerFunc - $$;计算偏移量
;
;
Int0x80HandlerFunc:;0x80中断
call PrintString
iret
Int0x80Handler equ Int0x80HandlerFunc - $$
;
;
; ds:ebp --> string address
; bx --> attribute
; dx --> dh : row, dl : col
PrintString:
push ebp
push eax
push edi
push cx
push dx
print:
mov cl, [ds:ebp]
cmp cl, 0
je end
mov eax, 80
mul dh
add al, dl
shl eax, 1
mov edi, eax
mov ah, bl
mov al, cl
mov [gs:edi], ax
inc ebp
inc dl
jmp print
end:
pop dx
pop cx
pop edi
pop eax
pop ebp
ret
Code32SegLen equ $ - CODE32_SEGMENT
[section .gs]
[bits 32]
STACK32_SEGMENT:
times 1024 * 4 db 0
Stack32SegLen equ $ - STACK32_SEGMENT
TopOfStack32 equ Stack32SegLen - 1通过如上的四步设置之后实验运行结果