Making a tiny executable for linux

Question

I was trying to make a tiny hello world executable in Linux but the smallest I could get was a bit over 8k.

I have been following this article. In that article, the author is iteratively making smaller and smaller executables. At some point in it, it provides the following code for NASM:

; tiny.asm
BITS 32
GLOBAL _start
SECTION .text
_start:
    mov     eax, 1
    mov     ebx, 42  
    int     0x80

and this should be the commands to compile it:

nasm -f elf tiny.asm
gcc -Wall -s -nostdlib tiny.o

According to the author, the executable size at that point should be 372 bytes. However, for me it's more than 12KBytes. The only thing I did differently is adding the -m32 to gcc so it compiles as 32 bits.

I manged to get it down to a bit over 8KBytes by using ld for linking instead of gcc and then using strip.

ld -m elf_i386 -s tiny.o
strip -s a.out

But it's still to large compered to the result in the article. Am I missing anything? I guess the article is quite old since it's compiling 32 bits by default. Could it be that newer Linux versions require bigger executables?

EDIT: code for my hello world program:

SECTION .data
msg: db "hello",10
msgLen: equ $ - msg ; the $ sign means the current byte address. That means the address where the next byte would go

SECTION .text

global _start ; "global" means that the symbol can be accessed in other modules. In order to refer to a global symbol from another module, you must use the "extern" keyboard
_start:
    mov eax, 4 ; syscall: write
    mov ebx, 1 ; stdout
    mov ecx, msg
    mov edx, msgLen
    int 0x80 ; call!

    mov eax, 1 ; syscal: exit
    mov ebx, 0 ; return code
    int 0x80

Making a tiny executable for linux

0 Answers