An example of making a syscall in assembly on OS X

mkdir.asm

; nasm -f macho64 mkdir.asm && ld -o mkdir mkdir.o && ./mkdir

%define SYSCALL_MKDIR 0x2000088
%define SYSCALL_EXIT  0x2000001

global start

section .text
start:
  call mkdir
  call exit
  ret

mkdir:
  mov rax, SYSCALL_MKDIR
  mov rdi, directory
  mov rsi, 0x1ED
  syscall

exit:
  mov rax, SYSCALL_EXIT
  mov rdi, 0
  syscall

section .data
directory: db 'tmp', 0

nasm -f macho64 mkdir.asm && ld -e start -static -o mkdir mkdir.o

correct way to build