main.c

别人的根据linux0.11改的一个小的操作系统

/*
 * main.c
 *
 * kernel main function
 * You can see whole progress.
 * 1 boot.bin (boot.asm)
 *      |
 *      V
 * 2 setup.bin (setup.asm)
 *      |
 *      V
 * 3 system.bin
 * system.bin is the kernel...
 */
#include "def.h"
#include "time.h"
#include "sched.h"
#include "system.h"

#define BCD_TO_BIN(val) ((val)=((val)&0xf)+((val)>>4)*10)

void init();                        /*task0     */
void task1();                       /*task1     */
void task2();                       /*task2     */

static long startup_time=0;         /*sign the system time  */
/*
 * Initialize system time,the time will be
 * saved in startup_time.
 */
static void time_init(void)
{
	struct t_time time;

	do{
		time.tm_sec=CMOS_READ(0);
		time.tm_min=CMOS_READ(2);
		time.tm_hour=CMOS_READ(4);
		time.tm_day=CMOS_READ(7);
		time.tm_mon=CMOS_READ(8);
		time.tm_year=CMOS_READ(9);
	}while(time.tm_sec!=CMOS_READ(0));

	BCD_TO_BIN(time.tm_sec);
	BCD_TO_BIN(time.tm_min);
	BCD_TO_BIN(time.tm_hour);
	BCD_TO_BIN(time.tm_day);
	BCD_TO_BIN(time.tm_mon);
	BCD_TO_BIN(time.tm_year);
	time.tm_mon--;
	startup_time=getStartTime(&time);
}
/*
 * Main function.
 * From here,we programme in c language.
 * 1. Clear screen.
 * 2. Print tip message.
 * 3. Initilize task 0 and global task struct arrays.
 * 4. Initilize char device.
 * 5. Open the timer interupt.
 * 6. Set interrupt flag bit.
 * 7. Entry user mode.(ring0->ring3)
 * 7. Initilize task 1 and 2.
 * 8. Loop,task 0,1 and 2 will alternative run.
 */
int main()
{
    clrscr();                       /* clear screen */
    printk("------MINIOS is running------\n");

    sched_init();                   /* initialize task 0 and global task struct arrays */
    char_drv_init();                /* initialize char device,fill keyboard interrupt vector */

    outportb(0x21,inportb(0x21)&0xfe);
	sti();                          /* open timer interrupt and set interrupt flag bit */
    move_to_user_mode();            /* entry user mode.From here,system will run in ring3 */

    //printf("Very well.%x Minios is startting...\n",255);
    task_init(task1);
    task_init(task2);               /* initialize task 1 and 2 */

	while(1){                       /* wait for new task,if there have no any new task,
                                            task0 will run forever */
        init();
	}

    return 0;
}
/*
 * Initialize task 0 and global task struct arrays.
 * Set task 0 tss descriptor and ldt descriptor.
 * Load task0's tr and ldtr.
 */
void sched_init()
{
    int i;

    for (i=0; i<NR_TASK; i++)       /* Initialize global task struct arrays */
    {
        task[i].pid = -1;           /* pid=-1 repersent that the task struct is available. */
        task[i].priority = -1;
        task[i].counter = -1;
        task[i].ldt_sel = -1;
        task[i].tss_sel = -1;
    }

    process_id = 1;
    p_current = NULL;
    p_current = NULL;
    p_previous = NULL;
    p_ready = NULL;
    p_head = NULL;

	set_tss_desc(0, _tss0);
	set_ldt_desc(0, _ldt0);

	cl_nt();                       /* prapre for move to user mode. */
    lldt(0);                       /* load task 0 ldtr */
	ltr(0);                        /* load task 0 tr */
}
/*
 * Task 0
 * Only print a char '0'.
 */
void init()
{
    unsigned long i;

    while(1)
    {
        putchar('0');
        for (i=0; i<0x3fff; i++);
    }
}
/*
 * Task 1
 * print a char 'A',keep it simply...
 */
void task1()
{
    unsigned long i;

    while(1)
    {
        putchar('A');
        for (i=0; i<0x3fff; i++);
    }
}
/*
 * Task2
 * print a char 'B',also simply...
 */
void task2()
{
    unsigned long i;

    while(1)
    {
        putchar('B');
        for (i=0; i<0x3fff; i++);
    }
}