16bit.asm

可在Intel x86上执行的最小OS,完全用组语撰写 可做DISK IO,Process Scheduling...等

[BITS 16]
[ORG KERNEL_START]

Start:
	mov ax, cs
	mov ds, ax
	mov es, ax
	mov ss, ax
	mov sp, 0x0000

	; switch to protected mode
	cli
	cld
	call PrepareIRQs
	call A20En

	lgdt [_GDT - KERNEL_START]	; load GDT
	lidt [_IDTR - KERNEL_START]	; load IDT

; CR0 :: PG CD NW 0		31..28
;        0 0 0 0		27..24
;        0 0 0 0		23..20
;        0 AM 0 WP		19..16
;        0 0 0 0		15..12
;        0 0 0 0		11.. 8
;        0 0 NE ET		 7.. 4
;        TS EM MP PE		 3.. 0

	mov eax, cr0
	or eax,  00000000000000000000000000000001b
	and eax, 10011111111110101111111111111111b
	mov cr0, eax
	jmp DWORD (kernel_code - _GDT):Begin32c