142 многовато, вот 128

$ cat hello.asm 
; fasm demonstration of writing simple ELF executable
format ELF executable 3
entry start
segment readable executable
start:
        mov     eax,4
        mov     ebx,1
        mov     ecx,msg
        mov     edx,msg_size
        int     0x80
        mov     eax,1
        xor     ebx,ebx
        int     0x80
;segment readable writeable
msg db 'Hello world!',0xA
msg_size = $-msg

$ fasm hello.asm 
flat assembler  version 1.73.06  (16384 kilobytes memory)
2 passes, 128 bytes.

$ ./hello
Hello world!