libasm

Photo by Andreas M on Unsplash

Tiny library written on assembly language

Includes:

• ft_read.s
• ft_strcmp.s
• ft_strcpy.s
• ft_strdup.s
• ft_strlen.s
• ft_write.s

And tests: main.c

Install

git clone https://github.com/kukinpower/libasm.git && cd

make

Compile and run with tests: make main

Research

x86-64 64bit Registers: Usage Conventions

rax     ; Return value
rbx     ; Callee saved
rcx     ; Arg 4
rdx     ; Arg 3
rsi     ; Arg 2
rdi     ; Arg 1
rsp     ; Stack ptr
rbp     ; Callee saved
r8      ; Arg 5
r9      ; Arg 6
r10     ; Caller saved
r11     ; Caller saved
r12     ; Callee saved
r13     ; Callee saved
r14     ; Callee saved
r15     ; Callee saved

Jumps

jmp     ; Unconditional Jump
je      ; Jump if Equal
jne     ; Jump if Not Equal
jg      ; Jump if Greater
jge     ; Jump if Greater or Equal
ja      ; Jump if Above (unsigned comparison)
jae     ; Jump if Above or Equal (unsigned comparison)
jl      ; Jump if Lesser
jle     ; Jump if Less or Equal
jb      ; Jump if Below (unsigned comparison)
jz      ; Jump if Zero
jnz     ; Jump if Not Zero
jc      ; Jump if carry set (C == 1)
jnc     ; Jump if carry is not set (C == 0)

Little endian and big endian

NASM Tutorial

x86_64 NASM Assembly Quick Reference ("Cheat Sheet")

strlen() implementation in NASM

Difference between JE/JNE and JZ/JNZ

Assembly - Conditions

Mac OS X 64 bit Assembly System Calls

How to compile assembly code

nasm -f macho64 hello.s
ld -e start -macosx_version_min 10.13.0 -static -o hello hello.o
./hello