Memory Protection Unit (MPU) Sample

Overview

This application provides a set options to check the correct MPU configuration against the following security issues:

Read at an address that is reserved in the memory map.
Write into the boot Flash/ROM.
Run code located in SRAM.

If the MPU configuration is correct each option selected ends up in an MPU fault.

Building and Running

This project can be built and executed as follows:

west build -b v2m_beetle samples/mpu/mpu_test
west flash

To build the single thread version, use the supplied configuration file for single thread: prj_single.conf:

west build -b v2m_beetle samples/mpu/mpu_test -- -DCONF_FILE=prj_single.conf
west build -t run

To build a version that allows writes to the flash device, edit prj.conf, and follow the directions in the comments to enable the proper configs.

Sample Output

uart:~$ mpu read
<err> os: ***** BUS FAULT *****
<err> os:   Precise data bus error
<err> os:   BFAR Address: 0x24000000
<err> os: r0/a1:  0x00009a5c  r1/a2:  0x00000008  r2/a3:  0x20001aa8
<err> os: r3/a4:  0x24000000 r12/ip:  0x00000000 r14/lr:  0x000029b7
<err> os:  xpsr:  0x21000000
<err> os: Faulting instruction address (r15/pc): 0x000003c8
<err> os: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
<err> os: Current thread: 0x20000708 (shell_uart)
<err> os: Halting system

uart:~$ mpu write
write address: 0x4000
<err> os: ***** MPU FAULT *****
<err> os:   Data Access Violation
<err> os:   MMFAR Address: 0x4000
<err> os: r0/a1:  0x00000000  r1/a2:  0x0000000e  r2/a3:  0x0badc0de
<err> os: r3/a4:  0x00004000 r12/ip:  0x00000004 r14/lr:  0x000003ab
<err> os:  xpsr:  0x61000000
<err> os: Faulting instruction address (r15/pc): 0x000003b2
<err> os: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
<err> os: Current thread: 0x20000708 (shell_uart)
<err> os: Halting system

uart:~$ mpu run
<err> os: ***** MPU FAULT *****
<err> os:   Instruction Access Violation
<err> os: r0/a1:  0x00009a5c  r1/a2:  0x00000001  r2/a3:  0x20001aa8
<err> os: r3/a4:  0x20000000 r12/ip:  0x00000000 r14/lr:  0x00006673
<err> os:  xpsr:  0x60000000
<err> os: Faulting instruction address (r15/pc): 0x20000000
<err> os: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
<err> os: Current thread: 0x20000708 (shell_uart)
<err> os: Halting system