634a1c5f6a
The previous method of VMA page tracking relied on the VMA always being mapped at least into one space and just kept track of pages in the spaces' page tables. This had a number of drawbacks, and the mapper system was too complex without much benefit. Now make VMAs themselves keep track of spaces that they're a part of, and make them responsible for knowing what page goes where. This simplifies most types of VMA greatly. The new vm_area_open (nee vm_area_shared, but there is now no reason for most VMAs to be explicitly shareable) adds a 64-ary radix tree for tracking allocated pages. The page_tree cannot yet handle taking pages away, but this isn't something jsix can do yet anyway.
jsix: A hobby operating system
jsix is the hobby operating system that I am currently building. It's far from finished, or even being usable. Instead, it's a sandbox for me to play with kernel-level code and explore architectures.
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 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. Modular design may be tossed out (hopefully temporarily) in some places to allow me to play around with 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.
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.
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