There is a base register exist for displacement addressing mode.
Base register contains a pointer to a memory location. An integer ( or constant) is also referred to as a displacement. The address of the operand is obtained by adding the contents of the base register plus the constant.
a self-relocating program is a program that relocates its own address-dependent instructions and data when run, and is therefore capable of being loaded into memory at any address.
So self relocating means self modifying .