Not sure right now, but ST link should be able to load code into any location of memory? However it is much more convenient to have one file, or you can use the gnu tools to append one code at the end of other or so to create one binary out of it (objcopy???). I think it's the same process as loading a bootloader and an app into the MCU.
It is not a problem for me to load the code at any position, but the problem is: how to get the machine code which will run at any position (this means no absolute adresses, jumps etc.).
Linux style code which can be ram loaded anywhere in the memory space is to be in demand in embedded bare metal or rtos space. It basically forbid to use the satically defined heap space by the linker. In 1990's HW access was done through what became the bios, through so called SWI #nn to make code more relocatable. If the code only use stack, then something might be ironed out. Indirect addressing in accessing data or function by pointers may cost cycles and acceleration bumps. These are performance or energy penalties when developping deep embedded apps on battery budget.
