第五回 | 進(jìn)入保護(hù)模式前的最后一次折騰內(nèi)存

start:
????mov?ax,#0x9000??;?this?is?done?in?bootsect?already,?but...
????mov?ds,ax
????mov?ah,#0x03????;?read?cursor?pos
????xor?bh,bh
????int?0x10????????;?save?it?in?known?place,?con_init?fetches
????mov?[0],dx??????;?it?from?0x90000.

比如獲取內(nèi)存信息。
; Get memory size (extended mem, kB)
    mov ah,#0x88
    int 0x15
    mov [2],ax
獲取顯卡顯示模式。
; Get video-card data:
    mov ah,#0x0f
    int 0x10
    mov [4],bx      ; bh = display page
    mov [6],ax      ; al = video mode, ah = window width
檢查顯示方式并取參數(shù)
; check for EGA/VGA and some config parameters
    mov ah,#0x12
    mov bl,#0x10
    int 0x10
    mov [8],ax
    mov [10],bx
    mov [12],cx
獲取第一塊硬盤的信息。
; Get hd0 data
    mov ax,#0x0000
    mov ds,ax
    lds si,[4*0x41]
    mov ax,#INITSEG
    mov es,ax
    mov di,#0x0080
    mov cx,#0x10
    rep
    movsb
獲取第二塊硬盤的信息。
; Get hd1 data
    mov ax,#0x0000
    mov ds,ax
    lds si,[4*0x46]
    mov ax,#INITSEG
    mov es,ax
    mov di,#0x0090
    mov cx,#0x10
    rep
    movsb

cli?????????;?no?interrupts?allowed?;

;?first?we?move?the?system?to?it's?rightful?place
????mov?ax,#0x0000
????cld?????????;?'direction'=0,?movs?moves?forward
do_move:
????mov?es,ax???????;?destination?segment
????add?ax,#0x1000
????cmp?ax,#0x9000
????jz??end_move
????mov?ds,ax???????;?source?segment
????sub?di,di
????sub?si,si
????mov?cx,#0x8000
????rep?movsw
????jmp?do_move
;?then?we?load?the?segment?descriptors
end_move:
????...