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CONFIG_ARM_MPU

ARM MPU Support

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.

Help

MPU implements Memory Protection Unit.

Notes:
The ARMv8-R MPU architecture requires a power-of-two alignment
of MPU region base address and size(64 bytes aligned).

The ARMv8-R MPU requires the active MPU regions be non-overlapping.
As a result of this, the ARMv8-R 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-R 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-R 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-R MPU
driver.

Direct dependencies

(CPU_HAS_MPU && ARM) || (CPU_HAS_MPU && CPU_AARCH64_CORTEX_R && ARM64)

(Includes any dependencies from ifs and menus.)

Default

  • y

Symbols that select this symbol

Kconfig definitions

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

Included via Kconfig:8Kconfig.zephyr:39arch/Kconfig:12arch/arm/Kconfig:57arch/arm/core/aarch32/Kconfig:297

Menu path: (Top) → ARM Options

config ARM_MPU
    bool "ARM MPU Support"
    select MPU
    select SRAM_REGION_PERMISSIONS
    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 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.

At arch/arm64/core/cortex_r/mpu/Kconfig:10

Included via Kconfig:8Kconfig.zephyr:39arch/Kconfig:12arch/arm64/Kconfig:32arch/arm64/core/Kconfig:140

Menu path: (Top) → ARM64 Options

config ARM_MPU
    bool "ARM MPU Support"
    default y
    select THREAD_STACK_INFO
    depends on CPU_HAS_MPU && CPU_AARCH64_CORTEX_R && ARM64
    help
      MPU implements Memory Protection Unit.

      Notes:
      The ARMv8-R MPU architecture requires a power-of-two alignment
      of MPU region base address and size(64 bytes aligned).

      The ARMv8-R MPU requires the active MPU regions be non-overlapping.
      As a result of this, the ARMv8-R 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-R 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-R 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-R MPU
      driver.

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