30. May 2024, 17:07
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;A20 Gate aktivieren
;GDT laden
;Protected Mode schalten
;jmp 0x10000:0000
mov esp, 0x100
enableA20:
pusha
;; Make sure interrupts are disabled
cli
;; Keep a counter so that we can make up to 5 attempts to turn
;; on A20 if necessary
mov CX, 5
.startAttempt1:
;; Wait for the controller to be ready for a command
.commandWait1:
xor AX, AX
in AL, 64h
bt AX, 1
jc .commandWait1
.
.
.
.
.
;A20 Gate aktivieren
;GDT laden
;Protected Mode schalten
;jmp 0x10000:0000
enableA20:
pusha
;; Make sure interrupts are disabled
cli
;; Keep a counter so that we can make up to 5 attempts to turn
;; on A20 if necessary
mov CX, 5
.startAttempt1:
;; Wait for the controller to be ready for a command
.commandWait1:
xor AX, AX
in AL, 64h
bt AX, 1
jc .commandWait1
;; Tell the controller we want to read the current status.
;; Send the command D0h: read output port.
mov AL, 0D0h
out 64h, AL
;; Wait for the controller to be ready with a byte of data
.dataWait1:
xor AX, AX
in AL, 64h
bt AX, 0
jnc .dataWait1
;; Read the current port status from port 60h
xor AX, AX
in AL, 60h
;; Save the current value of (E)AX
push AX ; 16-BIT
;; push EAX ; 32-BIT
;; Wait for the controller to be ready for a command
.commandWait2:
in AL, 64h
bt AX, 1
jc .commandWait2
;; Tell the controller we want to write the status byte again
mov AL, 0D1h
out 64h, AL
;; Wait for the controller to be ready for the data
.commandWait3:
xor AX, AX
in AL, 64h
bt AX, 1
jc .commandWait3
;; Write the new value to port 60h. Remember we saved the old
;; value on the stack
pop AX ; 16-BIT
;; pop EAX ; 32-BIT
;; Turn on the A20 enable bit
or AL, 00000010b
out 60h, AL
;; Finally, we will attempt to read back the A20 status
;; to ensure it was enabled.
;; Wait for the controller to be ready for a command
.commandWait4:
xor AX, AX
in AL, 64h
bt AX, 1
jc .commandWait4
;; Send the command D0h: read output port.
mov AL, 0D0h
out 64h, AL
;; Wait for the controller to be ready with a byte of data
.dataWait2:
xor AX, AX
in AL, 64h
bt AX, 0
jnc .dataWait2
;; Read the current port status from port 60h
xor AX, AX
in AL, 60h
;; Is A20 enabled?
bt AX, 1
;; Check the result. If carry is on, A20 is on.
jc .success
;; Should we retry the operation? If the counter value in ECX
;; has not reached zero, we will retry
loop .startAttempt1
;; Well, our initial attempt to set A20 has failed. Now we will
;; try a backup method (which is supposedly not supported on many
;; chipsets, but which seems to be the only method that works on
;; other chipsets).
;; Keep a counter so that we can make up to 5 attempts to turn
;; on A20 if necessary
mov CX, 5
.startAttempt2:
;; Wait for the keyboard to be ready for another command
.commandWait6:
xor AX, AX
in AL, 64h
bt AX, 1
jc .commandWait6
;; Tell the controller we want to turn on A20
mov AL, 0DFh
out 64h, AL
;; Again, we will attempt to read back the A20 status
;; to ensure it was enabled.
;; Wait for the controller to be ready for a command
.commandWait7:
xor AX, AX
in AL, 64h
bt AX, 1
jc .commandWait7
;; Send the command D0h: read output port.
mov AL, 0D0h
out 64h, AL
;; Wait for the controller to be ready with a byte of data
.dataWait3:
xor AX, AX
in AL, 64h
bt AX, 0
jnc .dataWait3
;; Read the current port status from port 60h
xor AX, AX
in AL, 60h
;; Is A20 enabled?
bt AX, 1
;; Check the result. If carry is on, A20 is on, but we might warn
;; that we had to use this alternate method
jc .warn
;; Should we retry the operation? If the counter value in ECX
;; has not reached zero, we will retry
loop .startAttempt2
;; OK, we weren't able to set the A20 address line. Do you want
;; to put an error message here?
jmp .fail
.warn:
;; Here you may or may not want to print a warning message about
;; the fact that we had to use the nonstandard alternate enabling
;; method
.success:
sti
popa
xor EAX, EAX
mov si, msg_a20_ok
call putstr
ret
.fail:
sti
popa
mov EAX, -1
mov si, msg_a20_fail
call putstr
ret
msg_a20_ok db "A20 Gate aktiviert",13,10,0
msg_a20_fail db "A20 Gate konnte nicht aktiviert werden",13,10,0
putstr:
lodsb
or al, al
jz short putstrd
mov ah, 0x0E
mov bx, 0x007
int 0x10
jmp putstr
putstrd:
retn
times 512-($-$$) db 0
mov ax, 0x1000
mov ds, ax
mov es, ax
start:
mov si, msg
call putstr
;mov si, msg1
;call putstr
;call getkey
;mov bl, 'r'
;cmp al, bl
;je gleich
;jmp ungleich
call read_str
mov dl, check
cmp dl, al
je gleich
jne ungleich
;################
msg db "Welcome to an OS Kernel",13,10,0
msg1 db "Gib etwas ein: ",13,10,0
msg2 db "Gleich",13,10,0
msg3 db "Ungleich",13,10,0
check db "Hallo",13,10,0
gleich:
mov si, msg2
call putstr
jmp $
ungleich:
mov si, msg3
call putstr
jmp $
putstr:
lodsb
or al, al
jz short putstrend
mov ah, 0x0E
mov bx, 0x0007
int 0x10
jmp putstr
putstrend:
retn
return:
ret
read_str:
mov ah,0
int 16h
cmp al,13
JE return
mov ah,0eh
int 10h
mov [bx],al
inc bx
jmp read_str
getkey:
mov ah, 0
int 0x16
mov ah, 0x0e
int 0x10
retn
times 512-($-$$) db 0
nasm os.asm
nasm files.asm
nasm hello.asm
nasm ask.asm
nasm ls.asm
partcopy os 0 200 -f0
partcopy files 0 200 -f0 200
partcopy hello 0 200 -f0 400
partcopy ask 0 200 -f0 600
partcopy ls 0 200 -f0 800
call getkey
mov dl, 'r'
cmp al, dl
je gleich
jmp ungleich
getkey:
mov ah, 0
int 0x16
mov ah, 0x0e
int 0x10
readchar:
mov ah, 0
int 0x16
cmp buchstabenadresse, 'r' case '\n':
vidmem = (vidmem/160)*160 + 160;
break;
