参考

https://blog.51cto.com/13475106/category6.html及狄泰软件相关课程

 主要代码文件

%include "common.asm"

global _start
global TimerHandlerEntry

extern TimerHandler

extern gCTaskAddr
extern gGdtInfo
extern gIdtInfo
extern InitInterrupt
extern EnableTimer
extern SendEOI
extern RunTask
extern KMain
extern ClearScreen

%macro BeginISR 0
    sub esp, 4
    
    pushad
    
    push ds
    push es
    push fs
    push gs
    
    mov dx, ss
    mov ds, dx
    mov es, dx
    
    mov esp, BaseOfLoader
%endmacro

%macro EndISR 0
    mov esp, [gCTaskAddr]
    
    pop gs
    pop fs
    pop es
    pop ds
    
    popad
    
    add esp, 4
    
    iret
%endmacro

[section .text]
[bits 32]
_start:
    mov ebp, 0
    
    call InitGlobal
    call ClearScreen
    call KMain
    
    jmp $
    
;
;    
InitGlobal:
    push ebp
    mov ebp, esp
    
    mov eax, dword [GdtEntry]
    mov [gGdtInfo], eax
    mov eax, dword [GdtSize]
    mov [gGdtInfo + 4], eax
    
    mov eax, dword [IdtEntry]
    mov [gIdtInfo], eax
    mov eax, dword [IdtSize]
    mov [gIdtInfo + 4], eax
    
    mov eax, dword [RunTaskEntry]
    mov dword [RunTask], eax
    
    mov eax, dword [InitInterruptEntry]
    mov [InitInterrupt], eax
    
    mov eax, dword [EnableTimerEntry]
    mov [EnableTimer], eax
    
    mov eax, dword [SendEOIEntry]
    mov [SendEOI], eax
    
    leave
    
    ret
    
;
;
TimerHandlerEntry:
BeginISR 
    call TimerHandler
EndISR
    

#include "kernel.h"
#include "screen.h"
#include "global.h"

void (* const InitInterrupt)() = NULL;
void (* const EnableTimer)() = NULL;
void (* const SendEOI)(uint port) = NULL;

Task* gCTaskAddr = NULL;
Task p = {0};

void Delay(int n)
{
    while( n > 0 )
    {
        int i = 0;
        int j = 0;
        
        for(i=0; i<1000; i++)
        {
            for(j=0; j<1000; j++)
            {
                asm volatile ("nop\n");
            }
        }
        
        n--;
    }
}

void TaskA()
{
    int i = 0;
    
    SetPrintPos(0, 12);
    
    PrintString("Task A: ");
    
    while(1)
    {
        SetPrintPos(8, 12);
        PrintChar('A' + i);
        i = (i + 1) % 26;
        Delay(1);
    }
}

void TimerHandlerEntry();

void TimerHandler()
{
    static uint i = 0;
    
    i = (i + 1) % 10;
    
    if( i == 0 )
    {
        static uint j = 0;
        
        SetPrintPos(0, 13);
        
        PrintString("Timer: ");
        
        SetPrintPos(8, 13);
        
        PrintIntDec(j++);
    }
    
    SendEOI(MASTER_EOI_PORT);
}

void KMain()
{
    int n = PrintString("D.T.OS\n");
    uint temp = 0;
    
    PrintString("GDT Entry: ");
    PrintIntHex((uint)gGdtInfo.entry);
    PrintChar('\n');
    
    PrintString("GDT Size: ");
    PrintIntDec((uint)gGdtInfo.size);
    PrintChar('\n');
    
    PrintString("IDT Entry: ");
    PrintIntHex((uint)gIdtInfo.entry);
    PrintChar('\n');
    
    PrintString("IDT Size: ");
    PrintIntDec((uint)gIdtInfo.size);
    PrintChar('\n');
    
    p.rv.cs = LDT_CODE32_SELECTOR;
    p.rv.gs = LDT_VIDEO_SELECTOR;
    p.rv.ds = LDT_DATA32_SELECTOR;
    p.rv.es = LDT_DATA32_SELECTOR;
    p.rv.fs = LDT_DATA32_SELECTOR;
    p.rv.ss = LDT_DATA32_SELECTOR;
    
    p.rv.esp = (uint)p.stack + sizeof(p.stack);
    p.rv.eip = (uint)TaskA;
    p.rv.eflags = 0x3202;
    
    p.tss.ss0 = GDT_DATA32_FLAT_SELECTOR;
    p.tss.esp0 = (uint)&p.rv + sizeof(p.rv);
    p.tss.iomb = sizeof(p.tss);
    
    SetDescValue(p.ldt + LDT_VIDEO_INDEX,  0xB8000, 0x07FFF, DA_DRWA + DA_32 + DA_DPL3);
    SetDescValue(p.ldt + LDT_CODE32_INDEX, 0x00,    0xFFFFF, DA_C + DA_32 + DA_DPL3);
    SetDescValue(p.ldt + LDT_DATA32_INDEX, 0x00,    0xFFFFF, DA_DRW + DA_32 + DA_DPL3);
    
    p.ldtSelector = GDT_TASK_LDT_SELECTOR;
    p.tssSelector = GDT_TASK_TSS_SELECTOR;
    
    SetDescValue(&gGdtInfo.entry[GDT_TASK_LDT_INDEX], (uint)&p.ldt, sizeof(p.ldt)-1, DA_LDT + DA_DPL0);
    SetDescValue(&gGdtInfo.entry[GDT_TASK_TSS_INDEX], (uint)&p.tss, sizeof(p.tss)-1, DA_386TSS + DA_DPL0);
    
    SetIntHandler(gIdtInfo.entry + 0x20, (uint)TimerHandlerEntry);
    
    InitInterrupt();
    
    EnableTimer();
    
    gCTaskAddr = &p;
    
    RunTask(gCTaskAddr);
}