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Emulating MPS2 Cortex M3 AN385 on QEMU

Requirements​

  1. GNU Arm Embedded Toolchain download here (tested on versiom 9.3.1 20200408)
  2. qemu-arm-system download here (tested on version 5.0.1 (v5.0.1-dirty))
  3. Make (tested on version 3.82)
  4. Linux OS (tested on Ubuntu 18.04)

How to download​

Navigate to a directory of your choice and run the following command

$ git clone https://github.com/FreeRTOS/FreeRTOS.git --recurse-submodules --depth 1

The previous command should create a directory named FreeRTOS

Getting Started on Windows using WSL​

The Windows Subsystem for Linux allows you to run native Linux applications from a shell on your windows machine.

To set up your Windows 10 machine to run this QEMU based demo you can follow these steps

  1. Install Ubuntu 20.04 LTS version from Microsoft Store, search for "Ubuntu"
  2. Update apt-get
sudo apt-get update
  1. Install Make and Qemu
sudo apt-get install -y make qemu qemu-system-arm
  1. Download and unzip Arm tools
cd ~
curl https://armkeil.blob.core.windows.net/developer/Files/downloads/gnu-rm/10-2020q4/gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2 -o gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2
tar -xjvf gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2
  1. Update your path to include the arm toolchain Edit ".profile", add the unzipped bin folder to the front of the path. You can run the same command in the terminal to update the path temporarily in the current shell
export PATH="$HOME/gcc-arm-none-eabi-10-2020-q4-major/bin:$PATH"
  1. Clone FreeRTOS
git clone https://github.com/FreeRTOS/FreeRTOS.git --recurse-submodules
  1. Compile the code
$ cd ./FreeRTOS/FreeRTOS/Demo/CORTEX_MPU_M3_MPS2_QEMU_GCC
$ export PATH=/path/to/arm/toolchain:$PATH
$ make

a file named ./build/RTOSDemo.axf will be generated

  1. Run the MPU Demo
sudo qemu-system-arm -machine mps2-an385 -monitor null -semihosting --semihosting-config enable=on,target=native -kernel ./build/RTOSDemo.axf -serial stdio -nographic -s -S

The options __ -s -S __ in the above command will start the program waiting for the debugger. Check the next section on how to attach the debugger to the program. Place a breakpoint on the MemMang_Handler function in startup.c file and observe how the program repeated generates memory faults and gracefully recovers from those.

How to start debugging​

  1. Build the debug version by using DEBUG=1:
$ make DEBUG=1
  1. Run the binary with -s and -S flags:
$ sudo qemu-system-arm -machine mps2-an385 -monitor null -semihosting \
        --semihosting-config enable=on,target=native \
        -kernel ./build/RTOSDemo.axf \
        -serial stdio -nographic -s -S

The options:
-s allows gdb to be attached to the process remotely at port 1234
-S starts the program in the paused state.

  1. Open another terminal to run GDB and connect to the process:
$ arm-none-eabi-gdb -q ./build/RTOSDemo.axf
(gdb) target remote :1234
(gdb) break main
(gdb) break MemMang_Handler
(gdb) c