MSP430FR6989: Firmware update handled by firmware (without bootloader)

Hi,

I am trying to find a way to achieve firmware update handled by the firmware itself (without entering bootloader state). My idea is that I can have a function in my firmware that handles the firmware validation and writing into memory address. Let's call this function as function A. To achieve this, function A must be functional and not to be overwritten during firmware update. Is there any way to achieve this? Or more specifically, how to define in the linker file (I suppose this is the area to edit) to exclude or to prevent the memory address of function A from being overwritten, while function A remains as a part of the complete firmware?

I can't find much forum posts that discuss about this. Would really appreciate if anyone could also share with me if you find any forum post to be relevant.

Thank you.