How can I relocate firmware for stm32?

I have built firmware for stm32f4, so I have *.elf an *.bin files. If I load *.bin file into internal flash it runs correctly. But if I want load this firmware to another address different from default (0x08000000) and run it from my bootloader, of course it does not works. I fix memory area address in project settings (I use CooCox 1.7.6 if it matter) and it begins runing from the bootloader.

I don't want rebuild project every time I load firmware in standalone mode or using bootloader. So I'm looking for method that will allow me to make *.bin files from *.elf, which will be able to load from the different addresses.

I tried manualy interupt vector table fixing. It allow me to run small blinker project but it doesn't work for more complex projects. I must be missing something.

Then I tried objcopy with --change-addresses but unfortunately it doesn't work. I get the same file without any difference.

I think, it is a general problem and there are solution for it but I must be missing something important.

You have to compile your code as position independent. See the -fpic and -fPIC options of gcc. Or you need a loader that understands the relocation table of the ELF image.

I just happened to complete an odyssey on STM32 Cortex-M4 (and M0) with Position-Independent Code firmware images operated by a bootloader. I will give you and overview and link the full article below. My evaluation board is NUCLEO-L432KC with target MCU STM32L432KCU6U. The magic goes like this:

On high level, there are couple of things needed:

A very simple bootloader. It only needs to read 2 4-byte words from the flash location of the firmware image. First is stack pointer address and second is Reset_Handler address. Bootloader needs to jump to Reset_Handler. But as the firmware is relocated further in the flash, the Reset_Handler is actually a bit further. See this picture for clarification:

So, bootloader adds the correct offset before jumping to Reset_Handler of the firmware image. No other patching is done, but bootloader (in my solution at least) stores location and offset of the firmware image, calculates checksum and passes this information in registers for the firmware image to use.

Then we need modifications in firmware linker file to force the ISR vector table in the beginning of RAM. For Cortex-M4 and VTOR (Vector Offset Table Register) the ISR vector table needs to be aligned to 512 boundary. In the beginning of RAM it is there naturally. In linker script we also dedicate a position in RAM for Global Offset Table (GOT) for easier manipulation. Address ranges should be exported via linker script symbols also.

We need also C compiler options. Basically these:

-fpic

-mpic-register=r9

-msingle-pic-base

-mno-pic-data-is-text-relative

They go to C compiler only! This creates the Global Offset Table (GOT) accounting.

Finally we need dedicated and tedious assembly bootstrap routines in the firmware image project. These routines perform the normal startup task of setting up the C runtime environment, but they additionally also go and read ISR and GOT from flash and copy them to RAM. In RAM, the addresses of those tables pointing to flash are offset by the amount the firmware image is running apart from bootloader. Example pictures:

I spent last 6 months researching this subject and I have written an in-depth article about it here:

https://techblog.paalijarvi.fi/2022/01/16/portable-position-independent-code-pic-bootloader-and-firmware-for-arm-cortex-m0-and-cortex-m4/