NCS 2.1 + MCUboot + nRF5340 overwriting .noinit areas

[dstude]

In NCS 2.1 with MCUboot on a nRF5340, a huge 256k area is allocated into .bss (see below) called "mock_flash".

unfortunately this writes far enough into RAM that it overwrites some areas we are trying to keep .noinit.

Any chance this can instead be done in .noinit and initialize as the buffer is needed?

 .bss.mock_flash
                0x00000000200061cd    0x40000 zephyr/drivers/flash/libdrivers__flash.a(flash_simulator.c.obj)

[amo-inv]

Hello.

The 256KB buffer is used by Flash simulator driver, automatically enabled by board dts file when a 'flash_sim' is defined. The flash simulator seem to have no use except for mcuboot (to be confirmed), so you can disable it in your project configuration with

CONFIG_FLASH_SIMULATOR=n

You will save 256KB of RAM...

Arnaud.

[dstude]

Thank you.  As you noted, can you please let me know what the functionality of the flash simulator is - or what is lost by disabling it?

Also my comment still stands - if this has some critical function and needs to be allocated, I'd like to request it is done with .noinit - outside the .bss - also to avoid such a huge RAM initialization.

[amo-inv]

As far as I understand (but I didn't dig into it), it is used by mcuboot for net core upgrade.

[amo-inv]

As far as I understand (but I didn't dig into it), it is used by mcuboot for net core upgrade.