unikraft VS FreeRTOS-Kernel

It seemed to be in a similar space to Genode when I had a brief look. Is it clear how it compares?

A system that claims to allow you to configure it in microkernel and other modes might be interesting for comparison of the approaches, but I've only noticed it via a local connexion: https://project-flexos.github.io/

Thanks for the feedback, we're in the process of adding a security section[0] which will detail more on the on-goings, but we'll work on adding more highlights on the main page.

I need to highlight we have separate research[1][2] which will make its way upstream soon which aims to provide hardening between internal libraries (e.g. isolating the network stack or scheduler) using gates like Intel MPK or separate hardware-accelerated services.

[0]: https://github.com/unikraft/docs/pull/32

[1]: https://project-flexos.github.io/

[2]: https://github.com/project-flexos/unikraft

Here is the port - https://github.com/FreeRTOS/FreeRTOS-Kernel/tree/main/portable/ThirdParty/GCC/Posix

Freertos has support for generic cortex m3: https://github.com/FreeRTOS/FreeRTOS-Kernel/tree/main/portable/GCC/ARM_CM3 It could very well work almost out of the box with your mcu.

the only OS written in iso c i found was RTOS and they have open bug reports due to strict aliasing in simple things like their linked list implementation, which they don't bother to fix because somehow that causes even more problems (?!): https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/54

You likely put the requirements of POSIX just to have an excuse. Fyi, FreeRTOS kernel, the only thing you need, is here: https://github.com/FreeRTOS/FreeRTOS-Kernel/

- https://github.com/FreeRTOS/FreeRTOS-Kernel (architecture, C)

FreeRTOS comes with 5 quite simple reference implementations of the heap memory allocator. You can study how it works.

The main branch is single-core. You're looking for the SMP branch.

On non-POSIX systems, malloc & free are implemented differently. EG FreeRTOS has some very simple malloc (and optionally free) implementations, eg heap_2.c (has malloc & free, but doesn't consolidate blocks), or heap_4.c (more complex, tries to prevent fragmentation by consolidating blocks, still less optmized & simpler than the glibc malloc/free used by most Linux systems).