uVisor IRQ blinky example

Warning: uVisor is superseded by the Secure Partition Manager (SPM) defined in the ARM Platform Security Architecture (PSA). uVisor is deprecated as of Mbed OS 5.10, and being replaced by a native PSA-compliant implementation of SPM.

This is a simple example to show how to write a uVisor-secured threaded application with IRQ support. One LED blinks periodically from the public box main thread. The second LED is exclusively owned by a secure box and toggles when the user button is pressed.

Supported devices:

Target	Toolchain	Public box LED	Secure box LED	User button	Baud rate
K64F	GCC_ARM	LED_BLUE	LED_RED	SW2	9600
DISCO_F429ZI	GCC_ARM	LED1	LED2	USER_BUTTON	9600
EFM32GG_STK3700	GCC_ARM	LED1	LED2	SW0	9600

Quickstart

The instructions here are specific to the K64F target, but can be easily extended to other supported targets as well.

For a release build, please enter:

$ mbed compile -m K64F -t GCC_ARM -c

You will find the resulting binary in BUILD/K64F/GCC_ARM/mbed-os-example-uvisor.bin. You can drag and drop it onto your board USB drive.

Press the reset button. You will see the public box LED blinking. Whenever you press the user button, the secure box LED will toggle. This interrupt is being served in the secure box and cannot be tampered with by the public box.

If you want, you can also read the output on the serial port. The example below is using the program "screen", and is connected to port tty.usbmodem1422, with a baud rate of 9600. To determine the proper port your board is connected to, you can run the command 'mbed detect':

$ screen /dev/tty.usbmodem1422 9600

You will see an output similar to the following one (assuming you press the user button after 4 loops count):

**** IRQ blinky uVisor example *****
Main loop count: 0
Main loop count: 1
Main loop count: 2
Main loop count: 3

Pressed switch, printing from interrupt - LED now on.

Main loop count: 4
Main loop count: 5
...

Debug

When a debugger is connected, you can observe debug output from uVisor. Please note that these messages are sent through semihosting, which halts the program execution if a debugger is not connected. For more information please read the Debugging uVisor on mbed OS guide. To build a debug version of this example, please enter:

$ mbed compile -m K64F -t GCC_ARM --profile mbed-os/tools/profiles/debug.json -c

Known issues

• Use of exporters for multiple IDEs is not supported at the moment.
• uVisor will halt the system on unregistered interrupts arrival. Do not attempt to push any SW buttons not listed in this document.

Troubleshooting

If you have problems, you can review the documentation for suggestions on what could be wrong and how to fix it.