SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world.
And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download two short videos (registration required) highlighting:

System Workbench for STM32

Incorrect binary size after compilation.

I will recommend you to do the following before changing the linker file

if the .elf works and you can download and debug I suggest to get the binary from the .elf file (elf and binary may be created with different settings i.e. compiler or linker flags may be different, epecially if you imported the project ), so to get the binary you can do it executing this command :
arm-none-eabi-objcopy -O binary add.elf add.bin

I am sure that that method shuld work because rememeber that the .elf file is the binary file + debug infomation and meta data, so you sould be able to extract only the binary data from a file that you already know that is working.

also you might want to take a look at this post: