How to call printf from x86/32 GNU assembler?

Question

I have written a small x86/32 assembler program that calls printf and gets compiled with gcc -m32 x.s:

     .data
format:
    .string "%d\n"
    .text
    .global main
    .type   main, @function
main:
    mov     $56, %eax
    push    %eax
    call    get_pc_eax
    add     $format - ., %eax
    push    %eax
    # call  printf@PLT
    call    get_pc_eax
    add     $_GLOBAL_OFFSET_TABLE_, %eax
    mov     printf@GOT(%eax), %eax
    call    *%eax
    add     $8, %esp
    xor     %eax, %eax
    ret
get_pc_eax:
    mov     (%esp), %eax
    ret
.section .note.GNU-stack,"",@progbits

If I enable the commented-out line call printf@PLT instead of the 4 lines after it (like it is now), then nothing happens on execution. I have some questions:

• Do I have to initialize the PLT before calling into it?
• Is this the recommended way to call a function in position independent code? It feels somewhat clumsy.
• I have searched for several hours and could not find a tutorial for i386 assembler on Linux using gas/gcc that also explains calling into libc and position independent code. I would be grateful if anyone could post a link.

UPDATE: After some extended discussion I came up with this code for main:

 1  push    %ebx
 2  mov     $56, %ebx
 3  push    %ebx
 4  call    get_pc_ebx
 5  add     $format - ., %ebx
 6  push    %ebx
 7  call    get_pc_ebx
 8  add     $_GLOBAL_OFFSET_TABLE_, %ebx
 9  xor     %eax, %eax
10  call    printf@PLT
11  add     $8, %esp
12  pop     %ebx
13  xor     %eax, %eax
14  ret

This code works. If I comment out the setup of %ebx in lines 7 and 8 the code crashes. From this I figure %ebx needs to point to the global offset table.

Can anyone link a tutorial/article/source that explains this mechanism?