GRUB2のマニュアルの1.4より引用．
Only kernels loaded at 1 megabyte or above are presently supported. Any attempt to load below that boundary will simply result in immediate failure and an error message reporting the problem.
1MBより下には読み込んではいけないという記述を多々見つけたものの，根拠がなかった．やっと見つけた．
