You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
48 lines
985 B
48 lines
985 B
mov ah, 0x0e
|
|
|
|
; attempt 1
|
|
; Fails because it tries to print the memory address (i.e. pointer)
|
|
; not its actual contents
|
|
mov al, "1"
|
|
int 0x10
|
|
mov al, the_secret
|
|
int 0x10
|
|
|
|
; attempt 2
|
|
; It tries to print the memory address of 'the_secret' which is the correct approach.
|
|
; However, BIOS starts loading at address 0x7c00
|
|
; so we need to add that padding beforehand. We'll do that in attempt 3
|
|
mov al, "2"
|
|
int 0x10
|
|
mov al, [the_secret]
|
|
int 0x10
|
|
|
|
; attempt 3
|
|
; Add the BIOS starting offset 0x7c00 to the memory address of the X
|
|
; and then dereference the contents of that pointer
|
|
mov al, "3"
|
|
int 0x10
|
|
mov bx, the_secret
|
|
add bx, 0x7c00
|
|
mov al, [bx]
|
|
int 0x10
|
|
|
|
; attempt 4
|
|
; We try a shortcut since we know that the X is stored at byte 0x2d in our binary
|
|
mov al, "4"
|
|
int 0x10
|
|
mov al, [0x7c2d]
|
|
int 0x10
|
|
|
|
|
|
jmp $
|
|
|
|
|
|
the_secret:
|
|
; ASCII code 0x58 is stored just before the zero-padding
|
|
; on this code that is at byte 0x2d (check it out using xdd)
|
|
db "X"
|
|
|
|
times 510-($-$$) db 0
|
|
dw 0xaa55
|