Mk Kernel

The Mk Kernel is a bare-metal, zero-dependency Real-Time Operating System (RTOS) core written from scratch in C and ARM Thumb-2 assembly. Designed specifically for the ARM Cortex-M7 processor (targeting the STM32F74xxx and STM32F75xxx MCU families), it sits at the Foundation layer of the Mk OS software ecosystem.

It provides a deterministic execution environment with memory protection, hardware-accelerated $O(1)$ scheduling, zero dynamic memory allocation, and zero-latency interrupt handling.

---

Key Features

• Preemptive $O(1)$ Scheduler: Fixed-priority scheduling with Round-Robin time-slicing for tasks of equal priority. Uses the ARM CLZ (Count Leading Zeros) instruction for instantaneous selection of the highest-priority ready task.
• Hardware-Enforced Security & Isolation (TEE): Software Trusted Execution Environment leveraging the Cortex-M7 Memory Protection Unit (MPU) and privilege levels.
• Zero Dynamic Allocation: Built entirely on fixed-size memory pools (T_mkPool), completely eliminating heap fragmentation and non-deterministic allocation delays.
• FPU Context Management: Full support for floating-point (K_MK_TYPE_FLOATING) and non-floating-point tasks.
• Synchronization Primitives: Semaphores, Mutexes (with priority inheritance), Event Fields, and Mailboxes.
• Zero-Latency Interrupts: High-priority hardware interrupts (7 to 0) are never masked by the kernel (BASEPRI masking).
• Asynchronous Callback Manager: Deferred execution engine handling up to 30 concurrent function callbacks via dedicated background tasks.
• Structured Fault Handling: Built-in trap handlers for HardFault, MemManage, BusFault, UsageFault, and stack overflow detection.
• Zero External Dependencies: Pure standalone implementation written in C and Assembly.

---

Documentation

ℹ️ For detailed technical articles and API documentation, visit La Fabrique du MCU.

---

Build

Requirements

• GNU Arm Embedded Toolchain 15.3 (rel1)
• CMake ≥ 3.25
• Ninja

Build system

The project uses CMake with presets defined in CMakePresets.json. Two presets are available:

Preset	Board	Type
release	STM32F746G-Eval2	Release (-Ofast)
debug	STM32F746G-Eval2	Debug (-O0 -g3)

Steps

1. Configure the project using the desired preset:

   cmake --preset debug
   

2. Build the firmware:

   cmake --build --preset debug
   

   This produces in build/<preset>/:

   • Mk.elf — programming file
   • Mk.map — linker map file

Compiler versions used

Tool	Version
arm-none-eabi-gcc	10.3.1 20210824 (GNU Arm Embedded Toolchain 10.3-2021.10)
arm-none-eabi-g++	10.3.1 20210824 (GNU Arm Embedded Toolchain 10.3-2021.10)
CMake	≥ 3.25
Ninja	latest

Flashing and debugging

Debug configurations for VS Code are included in the repository in .vscode/launch.json, using the Cortex-Debug extension with J-Link:

Configuration	Type	Binary flashed
Debug Mk (J-Link)	Debug	build/debug/Mk.elf
Release Mk (J-Link)	Release	build/release/Mk.elf

All configurations require a J-Link probe (or a ST-Link flashed with the J-Link firmware) and the J-Link Software installed.

License

Copyright © 2018-2026 Mathieu Renard. All rights reserved.

This project is licensed under the BSD 3-Clause License — see the LICENSE file for details.