kernel.c

一个最简单的操作系统,boot用NASM写的,使用最简单的汇编知识,大家下载后自己看吧

/*
	esp=0x3ffff0
	ds=es=fs=gs=ss=0
	cs=0x80000

	0000:0000 boot drive ,word
	0000:0002 start physical address of loader's data dword


	copyright 2005 by YaoSiHai
	www.woos.cn
*/

#include "kernel.h"
//KDSM must be at the start address of linked file!!!
_asm
{
_DATA	segment dword public use32 'DATA'
		align 4
kdsm db 'K','d','S','m'
_DATA	ends
	
}
char *copyright ="shyna kernel v1";


void data_init();
void init_file_system_layer();
void hd_init();//initializing basic Disk Driver

void main_start()
{

	
	int x,y;
	char str[32];
	byte *tp;
	
	data_init();

	tp=adjust_address("Initializing kernel...");
	write_console(tp,0xa);

	hd_init();//initializing basic Disk Driver
	
	init_file_system_layer();
	
	tp=adjust_address("Kernel is ready.\n");
	write_console(tp,0xa);
	

	tp=adjust_address("OK,this is the end of the DEMO kernel process\n");
	write_console(tp,x);
	

	while(1)
    	{
		
		
		
	}
	
}



void init_file_system_layer()
{
	
	write_console(adjust_address("File System-->"),0xa);
	
}

void hd_init()//initializing basic Disk Driver
{
	write_console(adjust_address("Disk Driver-->"),0xa);
}

void data_init()
{
	//at this point DS,SS is at Kernel(DS=GS=0)

	int i;
	char *pp=LOADER_CODE_START;
	uint p,dt;
	
	//step 1:
	//Create a DS selector for this thread

	while(1)
	{
		if(pp[0]=='K'&&pp[1]=='d'&&pp[2]=='S'&&pp[3]=='m')
		{

			//adjust ,needed by compiler and linker
			p=pp;
			p&=0xfffffff0;
			break;
		}
		pp++;
	}	
	_asm
	{
		;ds=0=gs;
		mov eax,p;	
		mov dword ptr gs:[2],eax;
	}
	
}





void memset(byte *p,byte what,int size)
{
	//work at current ds
	while(size>0)
	{
		*p=what;
		p++;
		size--;
	}
}

void memcpy(byte *from,byte *to,int size)
{
        //work at current ds
        while(size>0)
        {
                *to=*from;
                from++;
                to++;
                size--;
        }
}
int memcmp(byte *a,byte*b,int size)
{
	while(size>0)
	{
		if(*a==*b)
			size--;
		else return FALSE;

                a++;b++;
	}
	return TRUE;
}


		
		

byte inb(uint reg)
{
	_asm
	{
		push edx
		mov edx,reg
		xor eax,eax
		in al,dx
		pop edx

	}
}
word inw(uint reg)
{
	_asm
	{
		push edx
		mov edx,reg
		in ax,dx
		pop edx

	}
}

void outw(u32 data,u32 reg)
{
	_asm
	{
		mov edx,reg
		mov eax,data
		out dx,ax
	}
}
void outb(u32 data,u32 reg)
{
	_asm
	{
		mov edx,reg
		mov eax,data
		out dx,al
	}
}
byte * adjust_address(byte *s)
{
	uint p;
	_asm
	{
		mov eax,dword ptr gs:[2];
		add eax,s;
		mov p,eax;
	}
	return p;
}
int get_boot_drive_id()
{
	int i;
	_asm
	{
		xor eax,eax
		mov ax,word ptr gs:[0];
		mov i,eax;
	}
	return i;
}