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Linux Assembler Cheat Sheet by

Linux Assembler Basics

General Registers

EAX
Accumu­lator
EBX
Base
ECX
Counter
EDX
Data
General Registers: specific values are expected when calling the kernel.

Pointe­r-R­egi­sters

ESP
Stackp­ointer
EBP
Basepo­inter
EIP
Instru­cti­onp­ointer

Index-­Reg­isters

ESI
Source Index
EDI
Destin­ation Index

Segment- Registers

ECS
Code-S­egment
EDS
Data-S­egment
ESS
Stack-­Segment
EES
Extra-­Segment

Flags

NASM Basics

-f
filesystem
-g
debugg­infos
-o
output

Compiling a Code

nasm -f elf32 -g -o filename.o filename.nasm
ld -o filename filename.o
in 64bit Archit­ecture use -f elf64
  

Syscal­l-N­umbers Linux

EAX
Name(EBX, ECX, EDX)
1
exit( int)
2
fork( pointer)
3
read( uint, char*, int)
4
write( uint, char*, int)
5
open( char *, int, int)

NASM Code-S­ections

.text
Code
.data
initia­lized Data
.bss
uninit­ialized Data

Example

global _start

.data
    msg db "Hello World",0xa
    len equ $-msg

.text

_start:
    mov eax, 0x4                     
    mov ebx, 0x1       
    mov ecx, msg     
    mov edx, len        
    int 0x80               

exit:
    mov eax, 0x1
    mov ebx, 0x1
    int 0x80

Misc

int Nr
call Interrup Nr
 
call label
jumps to label
 
ret
returns to call
 
nop
no operation
 
lea dest,src
load effective addr. to dest
 
int 0x80
calls the Kernel in Linux

Logical Operations

neg op
two-Co­mpl­ement
 
not op
invert each bit
 
and dest,source
dest= dest source
 
or dest,source
dest=dest source
 
xor dest, surce
dest = dest XOR source
 

Control / Jumps (signed Int)

cmp op1,op2
Compare op1 with op2
 
test op1,op2
bitwise comparison
 
jmp dest
uncond­itional Jump
 
je dest
Jump if equal
 
jne dest
Jump if not equal
 
jz dest
Jump if zero
 
jnz dest
Jump if not zero
 
jg dest
Jump if greater
 
jge dest
Jump if greater or equal
 
jl dest
Jump if less
 
jle dest
Jump if less or equal
For unsigned Integer use 
 ja, jae
(above) or 
jb, jbe
(below)

Mnemonics Intel

mov dest, source
Moves Data
 
add dest, value
Add value to dest
 
sub dest,value
Subtract value3 from dest*
 
inc dest
Increment dest
 
dec dest
Decrement dest
 
mul src
Multiply EAX and src
 
imul dest, source
dest = dest * source
General Structure:
[label] mnemonic [operands] [;comment]

Stack Operations

push source
Insert Value onto the stack
pop dest
Remove value from stack
Stack is a LIFO-S­torage (Last In First Out)
 

Metadata

  • Languages:
  • Published: 13th January, 2015
  • Last Updated: 11th May, 2016
  • Rated: 5 out of 5 stars based on 1 ratings

Favourited By

rce343 lucas0080 imjustsarah

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