here is my code, along with my a20 enabler code incase that causes some problem
bochs reports that the index requested is greater than the limit which it says is 0 but it should be 3(or 24 bytes)
Code: Select all
[BITS 16]
jmp strt
tGDT:
;null;this is a generic gdt
dw 0
dw 0
dw 0
dw 0
;data
dw 0xffff
dw 0
db 0
db 0x92
db 0xff
db 0
;code
dw 0xffff
dw 0
db 0
db 0x9A
db 0xff
db 0
tGDT_END:
GDTR:
GDTsize DW 8*3-1
GDTbase DD tGDT
wkc:
xor al,al
in al, 0x64 ; get kbd status
test al, 2 ; is bit 1 clear?
jnz wkc ; if not wait some more
ret
halt:
mov byte [gs:0],al
mov byte [gs:1],0x04
cli
hlt
;; 'wait keyboard to be full' function ;;
wkf:
xor cx,cx
in al, 0x64 ; get kbd status
test al, 1 ; is bit 0 clear?
jz wkf ; if not wait some more
ret
strt:
;enable a20
cli
call wkc ; wait for kbd buffer to clear
mov al,0xd1 ; tell it we want to write to output port
out 0x64,al
call wkc ; wait again for kbd to clear
mov al,0xdf ; set desired settings (A20 gate)
out 0x60,al ; send value to data reg
call wkc ; wait for kbd to clear
mov cx,0x10
kbdwait:
xor ax,ax ; do anything
out 0xe0,ax ; some mor nonsense
loop kbdwait ; loop to waste time
;check if a20 was enabled
mov al,0xd0
out 0x64,al ; tell kbdc we want to read output port
call wkf ; wait for data to get in it
in al,0x60 ; get it
test al,2 ; test if A20 is on
jnz a20_on ; if it is clear, then it is off
mov al,'A' ; Error: A20 gate not enabled, halt pc
call halt
a20_on:
xor edx,edx
xor eax,eax
;says data not relocatable for 16bit stuff
mov eax,cr0
or al,1
cli
mov bx,0xb800
mov es,bx
mov bx,0
mov byte [es:bx],'h'
mov cr0,eax
[bits 32]
lgdt [GDTR]
mov bx,0x08
mov ds,bx
mov es,bx
mov ss,bx
mov gs,bx
mov fs,bx
jmp 0x10:t
t:
