A bunch of code that messes with low level stuff. That is:

- `arch/riscv/`: a bunch of samples on RISC-V running on M, S, or U mode.
- `fs/btrfs`: miscellanous tests on BTRFS.
- `kernel/`: samples that explore the API exposed by the Linux kernel, both from
    kernel and user space.
- `lang/c`: miscellanous code on the C programming language.

A lot of this is not taken solely from my brain, and I will give credit whenever
it's relevant to each piece of code. For the rest of the code, the GPLv3+
license applies.