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

You are viewing a reply to Moving ISRs to ITCM RAM  

Moving ISRs to ITCM RAM

Before I go on to give advice here, let me state for the record that i’ve never tried to do with an ARM core device and GCC what you’re describing here, but I’m familiar in a general sense with the concept of placing a section of code that is “loaded” in ROM/FLASH and then copied/relocated to RAM, and have done this with different toolchains and MCUs other than the STM32.

I think you have the linker script syntax correct - in particular, the bit at the end of the .itcm_text section declaration (>ITCM_RAM AT >FLASH) is critical. You want to make sure that your itcm-destined code is loaded into ROM (flash), but is located in ITCM_RAM.

I think what you’re looking for is the appropriate attribute syntax that you add to all functions that you want placed in a non-standard section. Here’s what it would look like:

int foo(int bar) __attribute__((section(".itcm_text")))
    // Code

You’ll need to add the attribute directive shown in the example above to each function or variable declaration that you want to have placed in the .itcm_text section.

You might want to modify your linker command file to add some symbol definitions that will make it easier for your code to find (and copy) the .itcm_text section to ITCM_RAM

.itcm_text :
. = ALIGN(4);
itcm_text_start = .;
*(.itcm_text) /* Fast-executing code */
*(.itcm_text*) /* Fast-executing code */
. = ALIGN(4);
itcm_text_end = .;

When it comes time to copy the ITCM code in ROM to ITCM_RAM, you should be able to do something like this:

// The "variables" referenced here don't actually contain anything meaningful - they are defined as symbols
// within the linker script. To extract the value assigned to each of these symbols, you need to take the
// address-of them (use the & address-of operator); e.g.:
// unsigned int section_start = (unsigned int) &itcm_text_start;

extern const unsigned char itcm_text_start;	// Make these uint8_t/char so they are treated as byte pointers when address-of'ed
extern const unsigned char itcm_text_end;

unsigned int itcm_text_size = (unsigned int) (&itcm_text_end - &itcm_text_start); // Pointer math should will work if these are declared as a char/byte type
unsigned char *itcm_ram_addr = ??? // Fill this in - could also get it from linker symbol if you add one
memcpy(itcm_ram_addr, &itcm_text_start, itcm_text_size);

Caveat: I’ve written the above “off the cuff” after doing a little research - I’ve not actually tried or tested any of it. I’ve probably got one or more of the details wrong. I may need to do something like this in one of my own projects I’ll be working on soon so I figured I’d start to research it now and possibly answer laltmann’s question at the same time.