View difference between Paste ID: XszHNdcx and RaAbGh6G

 section .data
 
 %macro full_line 1
     times %1 db "X"
     db 0x0a
 %endmacro
 
 %macro hollow_line 1
     db "X"
     times %1-2 db " "
     db "X", 0x0a
 %endmacro
 
 %macro box 2 ; width, height
     full_line %1
     %rep %2
         hollow_line %1
     %endrep
     full_line %1
 %endmacro
 
 board:
     box 80, 25
 
 board_size  equ     $ - board
 
 section .text
 
 global main
 
 main:
     mov rax, 0x2000004          ; syscall: SYS_write
     mov rdi, 1                  ; file descriptor: STDOUT_FILENO
-    mov rsi, board              ; buf (filler value)
+    mov rsi, board              ; buf
     mov rdx, board_size         ; nbytes
     syscall
 
     mov rax, 0x2000001          ; syscall: exit
     mov rdi, 0                  ; exit code
     syscall