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arch: arm: mpu: Add support for disabling the background address map

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Arm provides a default address map defining default behaviors for
certain address ranges, which can be overlayed with additional regions
in the MPU. Users may also turn off this background map, so that only
regions explicitly programmed in the MPU are allowed.

This provides a Kconfig so that platforms using a non-standard address
map may disable the background address map and provide their own
explicit MPU regions.

Signed-off-by: Benjamin Gwin <bgwin@google.com>
This commit is contained in:
Benjamin Gwin 2022-11-11 10:22:31 -08:00 • committed by Carles Cufí
commit b5fe0f7304
2 changed files with 11 additions and 1 deletions
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6
arch/arm/core/aarch32/mpu/Kconfig
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@ -82,6 +82,12 @@ config MPU_ALLOW_FLASH_WRITE
help
Enable this to allow MPU RWX access to flash memory
config MPU_DISABLE_BACKGROUND_MAP
bool "Disables the default background address map"
help
Enable this to turn off the default background MPU address map. Your
SoC definition should likely provide its own custom MPU regions.
config CUSTOM_SECTION_ALIGN
bool "Custom Section Align"
help

6
arch/arm/core/aarch32/mpu/arm_mpu.c
View file

@ -180,9 +180,13 @@ void arm_core_mpu_disable(void)
void arm_core_mpu_enable(void)
{
/* Enable MPU and use the default memory map as a
* background region for privileged software access.
* background region for privileged software access if desired.
*/
#if defined(CONFIG_MPU_DISABLE_BACKGROUND_MAP)
MPU->CTRL = MPU_CTRL_ENABLE_Msk;
#else
MPU->CTRL = MPU_CTRL_ENABLE_Msk | MPU_CTRL_PRIVDEFENA_Msk;
#endif
/* Make sure that all the registers are set before proceeding */
__DSB();