Hardware flash write protection

The hardware flash write protection driver (fprotect) can be used to protect flash areas from writing. The driver uses a hardware peripheral (BPROT, ACL, or SPU, depending on the chip model) to protect the area. The protection is irreversible until a reset occurs.

The following example shows how to protect PM_B0_SIZE bytes of the flash area starting from PM_B0_ADDRESS:

int err = fprotect_area(PM_B0_ADDRESS, PM_B0_SIZE);

API documentation

Header file: include/fprotect.h
Source files: lib/fprotect/
group fprotect

API for write protection of flash areas using Hardware peripheral.

Functions

int fprotect_area(uint32_t start, size_t length)

Protect flash area against writes.

Parameters:

  • start – [in] Start of range to protect.

  • length – [in] Length in bytes of range to protect.

Return values:

  • 0 – On success.

  • -EINVAL – If any of the argument are incorrect.

  • -EFAULT – If the protection was not applied properly.

  • -ENOSPC – If function is called too many times. Applies to devices where there is a limited number of configuration registers which are used for all address ranges.

int fprotect_area_no_access(uint32_t start, size_t length)

Protect flash area against reads/writes.

Parameters:

  • start – [in] Start of range to protect.

  • length – [in] Length in bytes of range to protect.

Return values:

  • 0 – On success.

  • -EINVAL – If any of the argument are incorrect.

  • -EFAULT – If the protection was not applied properly.

  • -ENOSPC – If function is called too many times. Applies to devices where there is a limited number of configuration registers which are used for all address ranges.

uint32_t fprotect_is_protected(uint32_t addr)

Check whether a block has already been protected.

NB: Only supported on HW platforms with ACL (CONFIG_HAS_HW_NRF_ACL).

Parameters:

  • addr – [in] The address to check. The block containing this address will be checked.

Return values:

  • 0 – If not protected

  • 1 – If only write protected

  • 2 – If only read protected

  • 3 – If write and read protected