143 lines
5.4 KiB
Markdown
143 lines
5.4 KiB
Markdown
|
|
|
|
# The jsix operating system
|
|
|
|
**jsix** is a custom multi-core x64 operating system that I am building from
|
|
scratch. It's far from finished, or even being usable - see the *Status and
|
|
Roadmap* section, below.
|
|
|
|
The design goals of the project are:
|
|
|
|
* Modernity - I'm not interested in designing for legacy systems, or running on
|
|
all hardware out there. My target is only 64 bit architecutres, and modern
|
|
commodity hardware. Currently that means x64 systems with Nehalem or newer
|
|
CPUs and UEFI firmware. (See [this list][cpu_features] for the currently
|
|
required CPU features.) Eventually I'd like to work on an AArch64 port,
|
|
partly to force myself to factor out the architecture-dependent pieces of the
|
|
code base.
|
|
|
|
* Modularity - I'd like to pull as much of the system out into separate
|
|
processes as possible, in the microkernel fashion. A sub-goal of this is to
|
|
explore where the bottlenecks of such a microkernel are now, and whether
|
|
eschewing legacy hardware will let me design a system that's less bogged down
|
|
by the traditional microkernel problems.
|
|
|
|
* Exploration - I'm really mostly doing this to have fun learning and exploring
|
|
modern OS development. Initial feature implementations may temporarily throw
|
|
away modular design to allow for exploration of the related hardware.
|
|
|
|
A note on the name: This kernel was originally named Popcorn, but I have since
|
|
discovered that the Popcorn Linux project is also developing a kernel with that
|
|
name, started around the same time as this project. So I've renamed this kernel
|
|
jsix (Always styled _jsix_ or `j6`, never capitalized) as an homage to L4, xv6,
|
|
and my wonderful wife.
|
|
|
|
[cpu_features]: https://github.com/justinian/jsix/blob/master/src/libraries/cpu/include/cpu/features.inc
|
|
|
|
## Status and Roadmap
|
|
|
|
The following major feature areas are targets for jsix development:
|
|
|
|
#### UEFI boot loader
|
|
|
|
_Done._ The bootloader loads the kernel and initial userspace programs, and
|
|
sets up necessary kernel arguments about the memory map and EFI GOP
|
|
framebuffer. Possible future ideas:
|
|
|
|
- take over more init-time functions from the kernel
|
|
- rewrite it in Zig
|
|
|
|
#### Memory
|
|
|
|
_Virtual memory: Sufficient._ The kernel manages virtual memory with a number
|
|
of kinds of `vm_area` objects representing mapped areas, which can belong to
|
|
one or more `vm_space` objects which represent a whole virtual memory space.
|
|
(Each process has a `vm_space`, and so does the kernel itself.)
|
|
|
|
Remaining to do:
|
|
|
|
- TLB shootdowns
|
|
- Page swapping
|
|
|
|
_Physical page allocation: Sufficient._ The current physical page allocator
|
|
implementation suses a group of block representing up-to-1GiB areas of usable
|
|
memory as defined by the bootloader. Each block has a three-level bitmap
|
|
denoting free/used pages.
|
|
|
|
#### Multitasking
|
|
|
|
_Sufficient._ The global scheduler object keeps separate ready/blocked lists
|
|
per core. Cores periodically attempt to balance load via work stealing.
|
|
|
|
User-space tasks are able to create threads as well as other processes.
|
|
|
|
Several kernel-only tasks exist, though I'm trying to reduce that. Eventually
|
|
only the timekeeping task should be a separate kernel-only thread.
|
|
|
|
#### API
|
|
|
|
_In progress._ User-space tasks are able to make syscalls to the kernel via
|
|
fast SYSCALL/SYSRET instructions.
|
|
|
|
Major tasks still to do:
|
|
|
|
- The process initialization protocol needs to be re-built entirely.
|
|
- Processes' handles to kernel objects need the ability to check capabilities
|
|
|
|
#### Hardware Support
|
|
|
|
* Framebuffer driver: _In progress._ Currently on machines with a video
|
|
device accessible by UEFI, jsix starts a user-space framebuffer driver that
|
|
only prints out kernel logs.
|
|
* Serial driver: _To do._ Machines without a video device should have a
|
|
user-space log output task like the framebuffer driver, but currently this
|
|
is done inside the kernel.
|
|
* USB driver: _To do_
|
|
* AHCI (SATA) driver: _To do_
|
|
|
|
## Building
|
|
|
|
jsix uses the [Ninja][] build tool, and generates the build files for it with a
|
|
custom tool called [Bonnibel][]. Bonnibel can be installed with [Cargo][], or
|
|
downloaded as a prebuilt binary from its Github repository.
|
|
|
|
[Ninja]: https://ninja-build.org
|
|
[Bonnibel]: https://github.com/justinian/bonnibel_rs
|
|
[Cargo]: https://crates.io/crates/bonnibel
|
|
|
|
Requrirements:
|
|
|
|
* bonnibel
|
|
* ninja
|
|
* clang
|
|
* nasm
|
|
* mtools
|
|
* curl for downloading the toolchain
|
|
|
|
### Setting up the cross toolchain
|
|
|
|
Running `pb sync` will download and unpack the toolchain into `sysroot`.
|
|
|
|
#### Compiling the toolchain yourself
|
|
|
|
If you have `clang` and `curl` installed, runing the `scripts/build_sysroot.sh`
|
|
script will download and build a LLVM toolchain configured for building jsix
|
|
host binaries.
|
|
|
|
### Building and running jsix
|
|
|
|
Once the toolchain has been set up, running Bonnibel's `pb init` command will
|
|
set up the build configuration, and `pb build` will actually run the build. If
|
|
you have `qemu-system-x86_64` installed, the `qemu.sh` script will to run jsix
|
|
in QEMU `-nographic` mode.
|
|
|
|
I personally run this either from a real debian amd64 testing/buster machine or
|
|
a windows WSL debian testing/buster installation. The following should be
|
|
enough to set up such a system to build the kernel:
|
|
|
|
sudo apt install qemu-system-x86 nasm clang-10 mtools curl ninja-build
|
|
sudo update-alternatives /usr/bin/clang clang /usr/bin/clang-10 1000
|
|
sudo update-alternatives /usr/bin/clang++ clang++ /usr/bin/clang++-10 1000
|
|
curl -L -o pb https://github.com/justinian/bonnibel_rs/releases/download/v2.3.0/pb-linux-amd64 && chmod a+x pb
|
|
|