??? .text The .text directive is used to hold the program??™s commands.
For example, the following assembly program prints ???Hello, haxor!??? to the screen:
section .data ;section declaration
msg db "Hello, haxor!",0xa ;our string with a carriage return
len equ $ - msg ;length of our string, $ means here
section .text ;mandatory section declaration
;export the entry point to the ELF linker or
global _start ;loaders conventionally recognize
; _start as their entry point
_start:
;now, write our string to stdout
;notice how arguments are loaded in reverse
mov edx,len ;third argument (message length)
mov ecx,msg ;second argument (pointer to message to write)
mov ebx,1 ;load first argument (file handle (stdout))
Gray Hat Hacking: The Ethical Hacker??™s Handbook
136
Register Registers hold the data to be manipulated. No
memory interaction. Both registers must be the
same size.
mov ebx, edx
add al, ch
Immediate Source operand is a numerical value. Decimal is
assumed; use h for hex.
mov eax, 1234h
mov dx, 301
Direct First operand is the address of memory to
manipulate. It??™s marked with brackets.
mov bh, 100
mov[4321h], bh
Register Indirect The first operand is a register in brackets that
holds the address to be manipulated.
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