CONFIG_ARM_MPU

ARM MPU Support

Type: bool

Help

MCU implements Memory Protection Unit.

Notes: The ARMv6-M and ARMv8-M MPU architecture requires a power-of-two alignment of MPU region base address and size.

The NXP MPU as well as the ARMv8-M MPU do not require MPU regions to have power-of-two alignment for base address and region size.

The ARMv8-M MPU requires the active MPU regions be non-overlapping. As a result of this, the ARMv8-M MPU needs to fully partition the memory map when programming dynamic memory regions (e.g. PRIV stack guard, user thread stack, and application memory domains), if the system requires PRIV access policy different from the access policy of the ARMv8-M background memory map. The allication developer may enforce full PRIV (kernel) memory partition by enabling the CONFIG_MPU_GAP_FILLING option. By not enforcing full partition, MPU may leave part of kernel SRAM area covered only by the default ARMv8-M memory map. This is fine for User Mode, since the background ARM map does not allow nPRIV access at all. However, since the background map policy allows instruction fetches by privileged code, forcing this Kconfig option off prevents the system from directly triggering MemManage exceptions upon accidental attempts to execute code from SRAM in XIP builds. Since this does not compromise User Mode, we make the skipping of full partitioning the default behavior for the ARMv8-M MPU driver.

Direct dependencies

CPU_HAS_MPU && ARM

(Includes any dependencies from ifs and menus.)

Defaults

No defaults. Implicitly defaults to n.

Symbols that select this symbol

Kconfig definition

At arch/arm/core/cortex_m/mpu/Kconfig:8

Included via Kconfig:8Kconfig.zephyr:31arch/Kconfig:12arch/arm/Kconfig:9arch/arm/core/Kconfig:277

Menu path: (Top) → ARM Options

config ARM_MPU
    bool "ARM MPU Support"
    select MEMORY_PROTECTION
    select THREAD_STACK_INFO
    select ARCH_HAS_EXECUTABLE_PAGE_BIT
    select MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT if !(CPU_HAS_NXP_MPU || ARMV8_M_BASELINE || ARMV8_M_MAINLINE)
    select MPU_REQUIRES_NON_OVERLAPPING_REGIONS if CPU_HAS_ARM_MPU && (ARMV8_M_BASELINE || ARMV8_M_MAINLINE)
    depends on CPU_HAS_MPU && ARM
    help
      MCU implements Memory Protection Unit.

      Notes:
      The ARMv6-M and ARMv8-M MPU architecture requires a power-of-two
      alignment of MPU region base address and size.

      The NXP MPU as well as the ARMv8-M MPU do not require MPU regions
      to have power-of-two alignment for base address and region size.

      The ARMv8-M MPU requires the active MPU regions be non-overlapping.
      As a result of this, the ARMv8-M MPU needs to fully partition the
      memory map when programming dynamic memory regions (e.g. PRIV stack
      guard, user thread stack, and application memory domains), if the
      system requires PRIV access policy different from the access policy
      of the ARMv8-M background memory map. The allication developer may
      enforce full PRIV (kernel) memory partition by enabling the
      CONFIG_MPU_GAP_FILLING option.
      By not enforcing full partition, MPU may leave part of kernel
      SRAM area covered only by the default ARMv8-M memory map. This
      is fine for User Mode, since the background ARM map does not
      allow nPRIV access at all. However, since the background map
      policy allows instruction fetches by privileged code, forcing
      this Kconfig option off prevents the system from directly
      triggering MemManage exceptions upon accidental attempts to
      execute code from SRAM in XIP builds.
      Since this does not compromise User Mode, we make the skipping
      of full partitioning the default behavior for the ARMv8-M MPU
      driver.

(The ‘depends on’ condition includes propagated dependencies from ifs and menus.)