Indigo

This is a toy/educational OS/kernel I made for the sole purpose of learning how these work and how one goes about making them.

Basic anatomy:

Most (all) of the code is in the src/ directory, with subdirs containing different "bits":

• src/loader is a UEFI-compatible executable which loads the kernel image + trampoline image into memory, builds a memory map for it to read and launches it (and also handles UEFI stuff/exiting boot services)
• src/trampoline is what the loader jumps to, which handles setting up higher-half paging and mapping the kernel to negative 2GB in the address space (in accordance with relocation model = kernel), and then calls the actual kernel
• src/kernel is the "actual" kernel which handles everything else.
• src/libs is code I wrote when I didn't know where to put code, and might eventually vanish, but fttb it's a libraries directory for things I might find useful. It has some overlap with kernel's utils subdir though.

Deps

The only code dependency this thing has is posix-uefi from bzt (bztsrc@gitlab), which is used in loader only to make programming under UEFI more palatable.

Progress:

So far, the OS boots, handles 64-bit mode, and starts up all other cores detected, and all the other stuff required to get to a point where starting cores is a reasonable thing to do. The current focus is kernel modules, which we'll use to make an initramfs-stored file loader to load other modules which will contain everything else, from Actual Modules (shared objs, not just non-relocated objects) to the scheduler and multi-processing management stuff. We've also got a depencency-graph style loader, so we can write modules for everything and only load the ones which are actually required.

Installing and running this:

Installing

If you received this via git clone then the git stuff should be setup, otherwise run git init as normal. Install the (singular) runtime dependency with git submodule init && git submodule update. The only change that's been made to submodules is the removal of line 73 of vendor/posix-uefi/uefi/uefi.h (the wchar_t def), which you might need to do. (TODO: fork posix-uefi) This project has a large number of build dependencies, most of which I cannot remember. Off the top of my head you may need:

• clang/clang++ & GNU Make
• ld.lld (I think this comes with clang)
• NASM
• lldb (if debugging)
• qemu (for running in a VM)
• mkgpt
• the edk2-ovmf QEMU firmware (I have no idea how I installed this one, try looking here)
• A suitable PC Screen Font file symlinked to src/kernel/arch/x86_64/font.psfu.gz, which might be set up already but I'm not sure.
• mksquashfs (apt install squashfs-tools)
• mformat (apt install mtools)

Running

This project is by no means guaranteed to work on your machine. It also probably wants a Linux environment, I have no idea if this works under cygwin/WSL. To run, just invoke make run to run without debugging, or make run_dbg to launch the same image with QEMU bound to a LLDB session.

legacy content for legacy me:

sane coding conventions:

• CONSTS_IN_SCREAMING_SNAKE
• variables_in_snake
• TypesInPascal
• functionsInCamel
• membersInCamel