从另一个文件调用程序集函数

我有下面的代码来计算一个数字的平方,它工作得很好:

        .section .data

        .section .text

        .globl _start
        .globl square

_start:
        pushl $10

        call square
        addl $4, %esp

        movl %eax, %ebx
        movl $1, %eax
        int $0x80

        .type square,@function

square:
        pushl %ebp
        movl %esp, %ebp
        movl 8(%ebp), %eax

        imull %eax, %eax

end_square:
        movl %ebp, %esp
        popl %ebp
        ret     

我想调用函数 square 从另一个名为 square_test.s . 这是我的尝试:

        .section .data

        .section .text

        .globl _start

_start:

        pushl $12
        call square
        addl $4, %esp

        movl %eax, %ebx
        movl $1, %eax
        int $0x80

但当链接时,我会犯这个错误:

$ as --32 square_test.s -o square_test.o
$ as --32 square.s -o square.o
$ ld -m elf_i386 square.o square_test.o -o square_test
square_test.o: In function `_start':
(.text+0x0): multiple definition of `_start'
square.o:(.text+0x0): first defined here

我该怎么解决?