Protect bootloader from overwrite/erase

RE: Protect bootloader from overwrite/erase

Asbjørn — Wed, 24 Sep 2014 09:18:08 GMT

I finally was able to see the behavior you are describing and I had to change the chip and use a nRF51822 revision 1. It's marked with N51822, QFAACA, 1230AA. The second line is the important one here, on revision 1 of the nrf51822 it will say QFAACx, where x can be A or 0. I do suspect that the chip you are working on are marked with CA or C0 and hence a revision 1 chip.

I've been testing this on revision 2 of the chip QFAAGx and this is the first version where the flash protect was implemented and hence I have not be able to recreate the behavior you see as expected.

RE: Protect bootloader from overwrite/erase

Eric Salem — Thu, 18 Sep 2014 12:49:06 GMT

The flash write and erase routines are pstorage as it is the setup in the DFU/bootloader examples.

The store is done in dfu_dual_bank:

uint32_t dfu_data_pkt_handle(dfu_update_packet_t * p_packet) {
     switch(m_dfu_state) {
          case DFU_STATE_RX_DATA_PKT:
               err_code = pstorage_raw_store(&m_storage_handle_app, (uint8_t*) p_data, data_length, m_app_data_received);
     }
}

Erase is done in dfu_dual_bank:

uint32_t dfu_image_size_set(uint32_t image_size) {
     switch (m_dfu_state)   {
          case DFU_STATE_IDLE: 
                err_code = pstorage_raw_clear(&m_storage_handle_app, image_size);
      }
}

And the setup is in main {

// Initialize.
    timers_init();
    gpiote_init();
    ble_stack_init();
    scheduler_init();
    sd_flash_protect((uint32_t)0,(uint32_t)0xFFFFFFFF);
}

where

static void ble_stack_init(void)
{
    uint32_t err_code;
    
    SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_XTAL_250_PPM, true);

    err_code = softdevice_sys_evt_handler_set(sys_evt_dispatch);
    APP_ERROR_CHECK(err_code);
}

Note: It is very hard to write and edit this comment in the 3 line editor window this forum gives me.

RE: Protect bootloader from overwrite/erase

Asbjørn — Thu, 18 Sep 2014 11:19:13 GMT

I added an attachment to my initial reply here. Please have a look at that main.c file.

If I understand you correctly you also set sd_flash_protect(0,0xFFFFFFFF) but are still allowed to write to that upper half of the memory? Any chance you could share the flash write routine that you use?

RE: Protect bootloader from overwrite/erase

Eric Salem — Tue, 16 Sep 2014 18:58:19 GMT

I added in the call sd_flash_protect(0,0xFFFFFFFF); to the bootloader after the softdevice is enabled just to verify that it will hardfault(per spec) instead of completing its process. I know the bootloader is not only erasing that area, but my firmware is getting written to that area as it is almost 100K in size. Using this to test, I not only have been able to successfully write firmware every time, but I have been able to erase the bootloader.

I have tested this with and without a debugger connected.

RE: Protect bootloader from overwrite/erase

Asbjørn — Tue, 16 Sep 2014 12:51:49 GMT

You can use the registers PROTENSETx to protect you bootloader. If you have enabled the softdevice these registers are accessed through the sd_flash_protect call. PROTENSETx enables you to protect 64 different blocks of the memory. For the nRF51x22 these blocks are 4 k big.

Update: main.c I edited the standard .../nRF6310/S110/bla_app_hrs example. The main file is above here. I added code to set the PROTENSET and protect the upper half of flash and then try to write to that area. It fails and gives me an error code.

UPDATE 2: Always make sure that you are using nRF51 of second revision if you are using sd_flash_protect() or PROTENSET. On nRF51 revision 1 this functionality is not available.