Can firmware be overwritten by fds?

RE: Can firmware be overwritten by fds?

Einar Thorsrud — Mon, 04 Apr 2022 13:21:43 GMT

Hi,

Yes, when you use a bootloader, FDS will use the pages immediately below the bootloader. If you don't use a bootloader, the FDS pages are located at the end of the flash. Note that when you use FDS and a bootloader you also need to ensure that you configure NRF_DFU_APP_DATA_AREA_SIZE in the bootloader's sdk_config.h correctly, so that the FDS pages are not overwritten during a DFU procedure.

RE: Can firmware be overwritten by fds?

Mike Tuev R9FT — Mon, 04 Apr 2022 12:53:03 GMT

Thank you for explanation.

I added the following LOG message to know exact addresses where FDS memory allocated:

#include "nrf_log.h"
static void flash_bounds_set(void)
{
    uint32_t flash_size  = (FDS_PHY_PAGES * FDS_PHY_PAGE_SIZE * sizeof(uint32_t));
    m_fs.end_addr   = flash_end_addr();
    m_fs.start_addr = m_fs.end_addr - flash_size;
    NRF_LOG_INFO("FDS  start: %x  end: %x",m_fs.start_addr,m_fs.end_addr);
}

By default in Keil examples these addresses overlaps with IROM1 memory area in Keil's project options.

Besides, FDS addresses are differerent when I run my application with secure_bootloader_ble (I use mergehex, nrfutil and nrfjprog for manually program firmware with bootloader, softdevice, application, bootloader settings).

RE: Can firmware be overwritten by fds?

Einar Thorsrud — Mon, 04 Apr 2022 12:04:52 GMT

Hi,

FDS automatically ensures that the FDS pages occupy the flash immediately below the bootloader (if used). That is essentially what happens in flash_bounds_set() and flash_end_addr(). FDS does not check where your application ends. It is your responsibility to have control over the memory layout and ensure that the various regions does not overlap. I suggest you refer to the Memory layout figure in the bootloader documentation if to help visualize how this looks.

If you want an error when building a too large application, you should adjust the flash size in your linker configuration to only include the size you have reserved for the application. Then you would get a build error if the application grows into the FDS pages.