hello world nasm

hello.asm

; hello world in intel 64bit x86 assembly

; drawn on from examples here:
; https://en.wikipedia.org/wiki/Netwide_Assembler
; http://www.nasm.us/xdoc/2.11.06/html/nasmdoc0.html

; the `start` global defined the entry point to the program
global start

; osx system call numbers
%define SYSCALL_EXIT 0x2000001
%define SYSCALL_READ 0x2000003
%define SYSCALL_WRITE 0x2000004

; i/o file descriptors
%define STDIN 0
%define STDOUT 1
%define STDERR 2

; exit codes
%define OK 0

%macro print 1
    ; execute a system call to write (`man 2 write`)
    ; first line, puts the syscall number into the `rax` register
    ; the next lines fill in the params for `write` - see the signature
    ;   ssize_t write(int fildes, const void *buf, size_t nbyte);
    mov rax, SYSCALL_WRITE
    mov rdi, STDOUT ; file descriptor
    mov rsi, %1     ; buffer
    mov rdx, %1.len ; size
    syscall
%endmacro

%macro wait_for_enter 0
    mov rax, SYSCALL_READ
    mov rdi, STDIN
    mov rdx, 1
    syscall
%endmacro

%macro exit 1
    mov rax, SYSCALL_EXIT
    mov rdi, %1
    syscall
%endmacro


section .data
    message db "hello hello, world!"
    .len equ $-message

    newline db 0x0a
    .len equ $-newline


section .text
start:
    print message
    print newline
    wait_for_enter
    exit OK

Makefile

# osx nasm compile using macho64

NASM=/usr/local/bin/nasm
LD=/usr/bin/ld

all: hello
	@./hello

hello: hello.o
	@$(LD) -macosx_version_min 10.0 -o hello hello.o

hello.o:
	@$(NASM) -f macho64 hello.asm -o hello.o

clean:
	@rm -f hello hello.o

.PHONY: clean hello hello.o