AT&T Assembly Far Jump to reload CS:IP

[teodori]

Hello,
is it possible to do a far like this:

Code: Select all

initseg:
	.word 0x0050
initoff:
	.word 0x0000

ljmp initseg, initoff # does not work
ljmp $0x0050, $0x0000 # works

Thank you

[thepowersgang]

I suggest you read the intel manuals, the type of jump you want is possible, but that is not the way to do it.

[teodori]

Hy found it

Code: Select all

BOOTDEV = 0x01ff
BOOTSEG = 0x07c0
INITSEG = 0x0050

.section .rodata

msg:
	.asciz "booting..."
msgend:

msglen:
	.word (msgend - msg)

errmsg:
	.asciz "disk error!"
errmsgend:

errmsglen:
	.word (errmsgend - errmsg)

.section .text

.globl Start

Start:
	.code16

ReloadCsIp:
	movw $BOOTSEG, %ax
	movw %ax, %ds				# Set Data Segment
	movw %ax, %es				# Set Extra Segment
	movw %ax, %fs				# Set Data2 Segment
	movw %ax, %gs				# Set Data3 Segment
	movw %ax, %ss				# Set Stack Segment
	ljmp $BOOTSEG, $SaveDev

SaveDev:
	movb %dl, BOOTDEV		# Save Boot Device to Memory
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