load warning: cannot find entry symbol _start
<p>I'm learning assembly programming. Below is the simple program that prints 'Hello, World!'. While the program runs perfectly, I'm getting the warning message while <code>loading</code></p>

<blockquote>
  <p>ld: warning: cannot find entry symbol _start; defaulting to 0000000008048080</p>
</blockquote>

<p>Here is the code :</p>

<pre><code>section .data
    msg db 'Hello, world!', 0xa
    len equ $ - msg

section .text
    global main

main:

    mov ebx, 1
    mov ecx, msg
    mov edx, len
    mov eax, 4
    int 0x80

    mov eax, 1
    int 0x80
</code></pre>

<p>Can anybody explain the meaning of this warning. I'm using <code>nasm</code> with <code>ubuntu 14</code>. </p>