Is there a method to debug the bootloader with GDB?
That depends if the code that you which to debug is the ROM or the RAM image of the bootloader. If the code that you which to debug is the RAM image you can simply load the RAM image with GDB and debug it as a normal application. It might be a little more difficult since the RAM image has optimize flags to reduce the size but you can temporarily remove them if this causes problems. The ram images is in the ramImage directory and the images that you shall load is blram.elf. Hope it helps.