Thema: A20 Line aktivieren

[syxce]

Hallo,
ich versuche schon eine Weile das A20 Gate zu aktivieren aber ich erhalte immer von Bochs den Fehler: "PUSHAD: eSP < 16"
Die Meldung das es erfolgreich aktiviert wurde wird jedoch ausgegeben.
Was ist der Fehler ?
danke

Code: [Auswählen]

;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

[syxce]

Hallo,
das habe ich gemacht jedoch erhalte ich jetzt folgenden Fehler, zuerst der Code, dann ein Pic von Bochs.

Code: [Auswählen]

;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
.
.
.
.
.


[Osbios]

Du springs direkt auf die Punkte .fail und .succses

Code: [Auswählen]

jmp .success

jmp .fail

Versuchst dann aber mit einem RET zurückzukehren!

Code: [Auswählen]

.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

Entweder du benutzt call um .fail und .success aufzurufen oder du machst nach ihrem Aufruf direkt weiter, anstelle ein ret einzusetzen!

Kleiner TIP: Um das Programm kontrolliert zu stoppen benutzt man Endlosschleifen wie JMP $

Und noch etwas, was bei bochs zwar keine Roll spielt aber bei echten PCs nötig ist: Am Ende eines Bootsektors gehört eine Bootsignatur, also anstelle von:

Code: [Auswählen]

times 512-($-$$) db 0

das hier:

Code: [Auswählen]

times 510-($-$$) db 0
dw 0xAA55

[syxce]

Ok danke, ich hab nun die "ret" mit einem jmp $ ersetzt und jetzt passts.
Achja wegen der Bootsignatur, das ist nicht der Bootloader sondern einer der Kernel, trotzdem danke.