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對於理解操作系統的工作我已經做它加載一個小的測試程序進行測試保護模式等的啓動扇區已在0x7c00被加載後,引導加載器加載測試代碼在段爲0x2000一個simpel引導程序並開始第一條指令。但是,當我嘗試進入保護模式時,系統將重新啓動。任何人都可以幫我解決這個問題嗎?進入保護模式重新啓動
這是我的部分代碼爲0x2000
BITS 16
; Entering_ProtectedMode:
cli
mov ax, 2000h
mov ss, ax
mov sp, 0FFFFh
sti
cld
mov ax, 2000h
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
;xor ax, ax
;mov ds, ax ; update data segment
cli ; clear interrupts
lgdt [gdtr] ; load GDT from GDTR (see gdt_32.inc)
call OpenA20Gate ; open the A20 gate
call EnablePMode ; jumps to ProtectedMode
OpenA20Gate:
in al, 0x93 ; switch A20 gate via fast A20 port 92
or al, 2 ; set A20 Gate bit 1
and al, ~1 ; clear INIT_NOW bit
out 0x92, al
ret
EnablePMode:
mov eax, cr0
or eax, 1
mov cr0, eax
jmp CODE_SEG : ProtectedMode
;*********************************
;* Global Descriptor Table (GDT) *
;*********************************
NULL_DESC:
dd 0 ; null descriptor
dd 0
CODE_DESC:
dw 0xFFFF ; limit low
dw 0 ; base low
db 0 ; base middle
db 10011010b ; access
db 11001111b ; granularity
db 0 ; base high
DATA_DESC:
dw 0xFFFF ; limit low
dw 0 ; base low
db 0 ; base middle
db 10010010b ; access
db 11001111b ; granularity
db 0 ; base high
gdtr:
dw gdtr - NULL_DESC - 1 ; length of GDT
dd NULL_DESC ; base of GDT
CODE_SEG equ CODE_DESC - NULL_DESC
DATA_SEG equ DATA_DESC - NULL_DESC
;******************
;* Protected Mode *
;******************
BITS 32
ProtectedMode:
.halt:
jmp .halt
;mov ax, 10h
;mov ds, ax ; update data segment