UCHEBA/4 СЕМ/ОПЕРАЦИОННЫЕ СИСТЕМЫ/2 ЛАБА/bootsect.asm

.intel_syntax noprefix
 
.code16
.global _start
_start:
	xor ax, ax                # Clear AX
	mov ds, ax                # Set DS to 0
	mov es, ax                # Set ES to 0
	mov ss, ax                # Set SS to 0
	mov sp, 0x7C00            # Set stack pointer

	mov ax, 0x1000            # Load the address where the disk is located
	mov es, ax                # Set ES to point to this location
	mov bx, 0                 # BX = 0
	mov ah, 2                 # Read sectors function
	mov dl, 1                 # Drive number (1 = first floppy)
	mov dh, 0                 # Head number
	mov cl, 1                 # Starting sector (1)
	mov ch, 0                 # Cylinder number
	mov al, 88                # Number of sectors to read
	int 0x13                  # BIOS interrupt to read sectors

	mov ax, 0x0003
	int 0x10

LOAD:
	xor cx, cx
	xor dx, dx
	mov eax, 0xe801 
	int 0x15
	mov [0x3400], cx 	  # Количество Кб до 16 Мб 
	mov [0x3420], dx 	  # Количество страниц размером 64 Кб        

LOADING_OS_PRINT:
	mov ah, 0x0e
	mov al, 'L'
	int 0x10
	mov al, 'o'
	int 0x10
	mov al, 'a'
	int 0x10
	mov al, 'd'
	int 0x10
	mov al, 'i'
	int 0x10
	mov al, 'n'
	int 0x10
	mov al, 'g'
	int 0x10
	mov al, ' '
	int 0x10
	mov al, 'O'
	int 0x10
	mov al, 'S'
	int 0x10
	mov al, '.'
	int 0x10
	mov al, '.'
	int 0x10
	mov al, '.'
	int 0x10
	mov al, ' '
	int 0x10
	mov al, 'P'
	int 0x10
	mov al, 'r'
	int 0x10
	mov al, 'e'
	int 0x10
	mov al, 's'
	int 0x10
	mov al, 's'
	int 0x10
	mov al, ' '
	int 0x10
	mov al, 's'
	int 0x10
	mov al, 'p'
	int 0x10
	mov al, 'a'
	int 0x10
	mov al, 'c'
	int 0x10
	mov al, 'e'
	int 0x10
	mov al, ' '
	int 0x10
	mov al, 't'
	int 0x10
	mov al, 'o'
	int 0x10
	mov al, ' '
	int 0x10
	mov al, 'c'
	int 0x10
	mov al, 'o'
	int 0x10
	mov al, 'n'
	int 0x10
	mov al, 't'
	int 0x10
	mov al, 'i'
	int 0x10
	mov al, 'n'
	int 0x10
	mov al, 'u'
	int 0x10
	mov al, 'e'
	int 0x10
	mov al, '!'
	int 0x10

input:
	mov ah, 0 
	int 0x16
	cmp al, 0x20
	jne input
	mov ax, 0x03
	int 0x10

COMPLETE:
	mov ax, 0x3               # Read character from keyboard
	int 0x10                  # BIOS interrupt for video services

	lgdt gdt_info             # Load GDT
	cli                       # Clear interrupts
	in al, 0x70               # Read from port 0x70
	or al, 0x80               # Set bit 7
	out 0x70, al              # Write back to port 0x70

	mov eax, cr0              # Read control register 0
	or al, 1                  # Set PE bit to enter protected mode
	mov cr0, eax              # Write back to CR0

	jmp 0x8:protected_mode    # Jump to protected mode

.code32
protected_mode:
	mov ax, 0x10              # Load data segment selector
	mov es, ax                # Set ES
	mov ds, ax                # Set DS
	mov ss, ax                # Set SS

	call 0x10000              # Call code at new segment

inf_loop:
	jmp inf_loop              # Infinite loop

gdt:
	.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
	.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9A, 0xCF, 0x00
	.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xCF, 0x00
gdt_info:
	.word gdt_info - gdt
	.word gdt, 0

# Reserve space to ensure we have a valid boot sector
.zero (512 - ($ - _start) - 2)
.byte 0x55, 0xAA