hello-linux64.asm

; How to compile this file:
; $ nasm -felf64 -o hello.o hello-linux64.asm
; $ ld -o hello.out hello.o
; $ ./hello.out
;
; Elements of a NASM program:
; * labels
; * instructions
; * operands
; * directives
; * sections
;
; Some instructions:
; mov x,y  (x <- y)
; and x,y  (x <- x & y)
; or x,y   (x <- x | y)
; xor x,y  (x <- x ^ y)
; add x,y  (x <- x + y)
; sub x,y  (x <- x - y)
; inc x    (x <- x + 1)
; dec x    (x <- x - 1)
; syscall  (trigger OS call: rax = syscall number, rdi/rsi/rdx/... = args)
; db       (define bytes)
; equ      (similar to a C '#define')
;
; Kinds of operands:
; * register  (rdx, r2d, r2b, dh, ...)
; * memory    ([750], [rcx + rsi*4], [rbx - 8], ...)
; * immediate (200, 0xc8, 0b1100_1000, ...)
;
; 64-bit reg | low 32-bits | low 16-bits | low 8-bits  | 16-bit high half
; -----------|-------------|-------------|-------------|-----------------
; r0 aka rax | r0d aka eax | r0w aka ax  | r0b aka al  | ah
; r1 aka rcx | r1d aka ecx | ...         | r1b aka cl  | ch
; r2 aka rdx | ...         |             | r2b aka dl  | dh
; r3 aka rbx |             |             | r3b aka bl  | bh
; r4 aka rsp |             |             | r4b aka spl |
; r5 aka rbp |             |             | r5b aka bpl |
; r6 aka rsi |             |             | r6b aka sil |
; r7 aka rdi | r7d aka edi | r7w aka di  | r7b aka dil |
; ...        | ...         | ...         | ...         |
; r15        | r15d        | r15w        | r15b        |
;
; other regs
; -------------
; rflags/eflags
; xmm{0-15}
; mmx...
; ymm...
; zmm...
; ...

global _start

STDIN equ 0
STDOUT equ 1
STDERR equ 2

SYS_WRITE equ 1
SYS_EXIT equ 60

section .data
message db 'hello, world!',10
message_len equ $-message

section .text
_start:
	mov rax, SYS_WRITE
	mov rdi, STDOUT
	mov rsi, message
	mov rdx, message_len
	syscall
	mov rdi, rax
	mov rax, SYS_EXIT
	syscall

; vi:ft=nasm:

triangle.asm

; nasm -felf64 triangle.asm && ld triangle.o && ./a.out

global _start

STDOUT equ 1

SYS_WRITE equ 1
SYS_EXIT equ 60

N equ 8

section .data
chars db '*',10

section .text
_start:
	mov r9b, 1
	mov r8b, 0
	mov rdi, STDOUT

print_triangle:
	mov rax, SYS_WRITE
	mov rsi, chars
	mov rdx, 1
	syscall

	inc r8b
	cmp r8b, r9b
	jne print_triangle

	mov rax, SYS_WRITE
	mov rsi, chars+1
	syscall

	mov r8b, 0

	inc r9b
	cmp r9b, N
	jng print_triangle

	mov rax, SYS_EXIT
	mov rdi, 0
	syscall