kogata operating system project

kogata operating system : small and ~~beautiful~~small.

Project characteristics

Written in C

I have considered using higher-level languages but for lack of understanding of the associated compiler, I never have had the same impression of understanding exactly what was happening that I had with C. Also, the necessity of a runtime is bothering. I do regret not being able to exploit the magic of strongly typed functional languages, but what can I do...

Monolithic design

I would have liked to have more of a client/server architecture (microkernel-like), but the necessity for asynchronous communication makes it much more difficult to code, and contradicts the goal of having simple and straightforward code.

Emphasis on code quality and reliability

The code for the project must make sense, be simple and straightforward, and be easily understandable in complete detail so that we can track bugs and extend the system more easily.

Capability-like security system

A normal ring-3 application managed by a ring-0 kernel is a bit like a virtual machine in which the process runs : it has a full memory space and doesn't see it when it is interrupted by other things happening on the system. We take this a bit further by saying that a process that creates a child process creates a "box" in which some of the resources of the parent can be made accessible, possibly with some restrictions. In particular this is true of filesystems : each process has its own filesystem namespace. Basically it means that the login manager has full access to all disk devices and system hardware, the session manager for a user session only has access to the user's data and read-only access to system files, and an untrusted user application can be sandboxed in an environment where it will only see its own data and necessary libraries, with "bridges" enabling access to user-approved data (for instance a file chooser, or taking a picture with a webcam or such). Also when a process has a child, it is seen as sharing part of it's computing resources with the child, therefore when a process is terminated, all its children are terminated as well.

Goal : small and cool

I would love to have kogata fit on a 1.44MB floppy and run with a full GUI and some cool apps (remember the QNX demo floppy!). Also, I want to be able to use it on older computers and prove that such machines can still be put to use.

And more...

See files in the doc/ folder of the repository for more details about some parts of the system (some of that is only plans for the distant future).

How to build

Requirements

git for accessing the repository
the bam build tool https://matricks.github.io/bam/
i586-elf cross-compiler built by these scripts.
nasm
for testing, either qemu or bochs
Optionnal: scan-build (included with Clang) for static analysis

Building and running

To build, clone the git repository somewhere and simply run:

$ make

Launching qemu is also included in the makefile:

$ make run_qemu

Warning: dependencies between portions of code are not necessarily well handled by the makefile system. If you made changes and the OS fails miserably, try doing a make rebuild before blaming your code.

Running the tests

The directory src/tests/ contains a few tests for some of the core components. The running of these tests is automated. To run the test suite, simply invoke the corresponding make target (everything is rebuilt before running the tests):

$ make run_tests

Structure of the project

Modules

The kernel
Libraries
libkogata : basic system functionality (memory allocator, mutexes, debugging)
libc : implementation of a (very restricted) subset of the standard C library, basically just the functions that were needed somewhere
libalgo : useful data structures (hashtables, AVL trees, maybe more in the future)
Userspace : not much work done yet

Files in the repository

doc/                        documentation
src/
src/kernel/                 code for the kogata kernel
src/common/                 code shared between kernel and userspace libs
src/common/include/proto    datastructures & constants used for system calls
src/lib/                    code for userspace libraries
src/lib/include/proto       definition of IPC protocols used in the system
src/sysbin/                 userspace system binaries
src/tests/                  test suite

Licence

None of the source files have a licence header because it's cumbersome. All the code and associated documentation found in this repository is released under the ISC licence as detailed in the COPYING file. Some parts of the code are very directly inspired from examples found on the OSDev wiki, thank you all!