asm-study

This is a simple repo with my asm codes.

I am saving some pieces of codes to understand how its works, some programs and shellcods

I am not a nASM Guru. I am a beginner yet, so if you find mistakes, please show me that.

how to compile the codes

I am using nasm and gcc to compile my codes

nasm -f elf64 file.asm

gcc file.o -o file

Adding intel syntax in GDB

echo "set dis intel" > ~/.gdbinit

To see how instruction works i am using GDB

gdb file -q

To see the registers use this

layout regs

Conventions

###syscall numbers: /usr/src/linux/include/asm-x86_64/unistd.h

1. kernel parameters:
2. r9; 6th param
3. r8; 5th param
4. r10; 4th param
5. rdx; 3rd param
6. rsi; 2nd param
7. rdi; 1st param
8. rax; syscall_number
9. syscall

###return register:

1. rax; 1st
2. rdx; 2nd

preserved accross function call: RBX RBP ESP R12 R13 R14 R15

function parameter (when linked with external libraries):

1. r9; 6th param
2. r8; 5th param
3. rcx; 4th param
4. rdx; 3rd param
5. rsi; 2nd param
6. rdi; 1st param
7. call library