hello world

hello.s

@@ -0,0 +1,27 @@
+global _start
+
+; constants
+SYS_WRITE   equ 1
+SYS_EXIT    equ 60
+STDOUT      equ 1
+
+SECTION .data
+hello           db  "Hello world!", 0x0a
+hello_len       equ $ - hello
+
+SECTION .text
+
+_start:
+    ; syscall(SYS_WRITE, STDOUT, hello, hello_len);
+    mov     rax, SYS_WRITE
+    mov     rdi, STDOUT
+    mov     rsi, hello
+    mov     rdx, hello_len
+    syscall
+    push    rax
+
+    ; syscall(SYS_EXIT, <sys_write return value> - hello_len);
+    mov     rax, SYS_EXIT
+    pop     rdi
+    sub     rdi, hello_len
+    syscall