Question

I’m interesting in compile a 32bit assembly code using a 64bit machine.

This is the 32 bit code:

.global factorial

factorial:
    pushl %ebp          
    movl %esp, %ebp
    subl $8, %esp       
      pushl %esi
      pushl %ebx

    movl $1,-4(%ebp)
    movl $2,%esi
for:  
      cmpl 8(%ebp), %esi
    jg endfor
      movl -4(%ebp), %ebx
      imull %esi, %ebx
      movl  %ebx, -4(%ebp)
    incl %esi   

    jmp for
endfor:
      movl -4(%ebp), %eax   

    popl %ebx       
    popl %esi   
    movl %ebp, %esp
    popl %ebp   
    ret

I’m building:

> gcc test32.s -m32 -o test32

But I’m obtaining:

/usr/lib/gcc/x86_64-linux-gnu/4.6.1/../../../../lib32/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status

know someone who’s going? Thanks in advance!

Answer 1

You are trying to compile and link to an executable. For that to work, you need a main function that contains the programs start function.

All you have is a single mathematical function, without any way to define inputs and outputs.