We don't refer to _bss and _ebss any more.

src/arch/i386/core/hooks.c

 #include "registers.h"
 #include "main.h"
-#include "etherboot.h"
 #include "hooks.h"
 
-/* Symbols defined by the linker */
-extern char _bss[], _ebss[];
-
 /*
  * This file provides the basic entry points from assembly code.  See
  * README.i386 for a description of the entry code path.