:orphan:

.. title:: ARM_MPU

.. option:: CONFIG_ARM_MPU

*ARM MPU Support*

Type: ``bool``

Help
====

MCU implements Memory Protection Unit.

Notes:
The ARMv6-M and ARMv7-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 application 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
===================

\ :option:`CPU_HAS_MPU <CONFIG_CPU_HAS_MPU>` && \ :option:`CPU_CORTEX_M <CONFIG_CPU_CORTEX_M>` && !\ :option:`ARM64 <CONFIG_ARM64>` && \ :option:`ARM <CONFIG_ARM>`

*(Includes any dependencies from ifs and menus.)*

Defaults
========

No defaults. Implicitly defaults to ``n``.

Symbols selected by this symbol
===============================

- \ :option:`MPU <CONFIG_MPU>`
- \ :option:`SRAM_REGION_PERMISSIONS <CONFIG_SRAM_REGION_PERMISSIONS>`
- \ :option:`THREAD_STACK_INFO <CONFIG_THREAD_STACK_INFO>`
- \ :option:`ARCH_HAS_EXECUTABLE_PAGE_BIT <CONFIG_ARCH_HAS_EXECUTABLE_PAGE_BIT>`
- \ :option:`MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT <CONFIG_MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT>` if !(\ :option:`CPU_HAS_NXP_MPU <CONFIG_CPU_HAS_NXP_MPU>` || \ :option:`ARMV8_M_BASELINE <CONFIG_ARMV8_M_BASELINE>` || \ :option:`ARMV8_M_MAINLINE <CONFIG_ARMV8_M_MAINLINE>`)
- \ :option:`MPU_REQUIRES_NON_OVERLAPPING_REGIONS <CONFIG_MPU_REQUIRES_NON_OVERLAPPING_REGIONS>` if \ :option:`CPU_HAS_ARM_MPU <CONFIG_CPU_HAS_ARM_MPU>` && (\ :option:`ARMV8_M_BASELINE <CONFIG_ARMV8_M_BASELINE>` || \ :option:`ARMV8_M_MAINLINE <CONFIG_ARMV8_M_MAINLINE>`)

Symbols that select this symbol
===============================

- \ :option:`ETH_MCUX <CONFIG_ETH_MCUX>`

Kconfig definition
==================

.. highlight:: kconfig

At ``arch/arm/core/aarch32/cortex_m/mpu/Kconfig:8``

Included via ``Kconfig:8`` → ``Kconfig.zephyr:29`` → ``arch/Kconfig:12`` → ``arch/arm/Kconfig:42`` → ``arch/arm/core/aarch32/Kconfig:237`` → ``arch/arm/core/aarch32/cortex_m/Kconfig:308``

Menu path: (Top) → ARM Options

.. parsed-literal::

    config ARM_MPU
    	bool "ARM MPU Support"
    	select \ :option:`MPU <CONFIG_MPU>`
    	select \ :option:`SRAM_REGION_PERMISSIONS <CONFIG_SRAM_REGION_PERMISSIONS>`
    	select \ :option:`THREAD_STACK_INFO <CONFIG_THREAD_STACK_INFO>`
    	select \ :option:`ARCH_HAS_EXECUTABLE_PAGE_BIT <CONFIG_ARCH_HAS_EXECUTABLE_PAGE_BIT>`
    	select \ :option:`MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT <CONFIG_MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT>` if !(\ :option:`CPU_HAS_NXP_MPU <CONFIG_CPU_HAS_NXP_MPU>` || \ :option:`ARMV8_M_BASELINE <CONFIG_ARMV8_M_BASELINE>` || \ :option:`ARMV8_M_MAINLINE <CONFIG_ARMV8_M_MAINLINE>`)
    	select \ :option:`MPU_REQUIRES_NON_OVERLAPPING_REGIONS <CONFIG_MPU_REQUIRES_NON_OVERLAPPING_REGIONS>` if \ :option:`CPU_HAS_ARM_MPU <CONFIG_CPU_HAS_ARM_MPU>` && (\ :option:`ARMV8_M_BASELINE <CONFIG_ARMV8_M_BASELINE>` || \ :option:`ARMV8_M_MAINLINE <CONFIG_ARMV8_M_MAINLINE>`)
    	depends on \ :option:`CPU_HAS_MPU <CONFIG_CPU_HAS_MPU>` && \ :option:`CPU_CORTEX_M <CONFIG_CPU_CORTEX_M>` && !\ :option:`ARM64 <CONFIG_ARM64>` && \ :option:`ARM <CONFIG_ARM>`
    	help
    	  MCU implements Memory Protection Unit.
	  
    	  Notes:
    	  The ARMv6-M and ARMv7-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 application 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.)*