why this built-in kernel module's init function won't be called on startup?

I'm using Linux on an MMU-less ARM platform, so, normal ELF files won't work and I should use FDPIC_ELF executable. but my kernel couldn't execute fdpic executables (error -8 (ENOEXEC)).

so, I decided to put some printk in binfmt_elf_fdpic.c init function to trace it. but it won't work.

static int __init init_elf_fdpic_binfmt(void){    printk("  Mahyar: elf_fdpic: init started\n"); // delete me later!    register_binfmt(&elf_fdpic_format);    printk("  Mahyar: elf_fdpic: init finished\n"); // delete me later!    return 0;}

I've enabled the fdpic elf support in menuconfig->executable-formats as built-in feature (not a kernel module).

also my kernel log level is 15 (the highest level (should print everything))

when I change something in binfmt_elf_fdpic.c file, and run the make command, it compile that file again. so it means this file should work.but why it won't load into kernel while startup?