For enhanced security ARMv8-M firmware doesn't allow the hardfault
handler to be hooked by non-secure code. Because of this there is no
way to recover from the MPU fault tests. This PR disables those tests
until hardfault recovery is supported by secure firmware.
Ensure that code written to ram is flushed and that caches are cleared
before attempting to executing from ram. This fixes CI failures on the
MPU test when it is built for Cotex-M7 devices such as the
NUCLEO-F746ZG.
Create a dedicated MPU directory for standard Arm MPU implementations
in preparation for the Arm v8m MPU. Replace MBED_MPU_ENABLED with
DEVICE_MPU to align with the porting layer of other HAL APIs.
Test that the MPU correctly stops execution of memory in the stack
region, heap region, data region and bss region. Also check that the
MPU can be enabled, disabled and freed.
Kevin Bracey
Russ Butler