8cdc39fdee
Removed the frame allocation logic from page_manager and replaced it
with using an instance of frame_allocator instead. This had several
major ripple effects:
- memory_initalize() had to change to support this new world
- Where to map used blocks is now passed as a flag, since blocks don't
track their virtual address anymore
- Instead of the complicated "find N contiguous pages that can be
mapped in with one page table", we now just have the bootloader give
us some (currently 64) pages to use both for tables and scratch
space.
- frame_allocator initialization was split into two steps to allow
mapping used blocks before std::move()ing them over
popcorn: A toy OS kernel
popcorn is the kernel for the hobby OS 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. 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. Given that there are no processes yet, the kernel is monolithic by default.
-
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.
Building
Popcorn uses the ninja build tool, and generates the build files for it with
the generate_build.py script. The other requirements are:
- python 3 for generating the build config
- The Jinja2 package is also required
- clang
- mtools
- ninja
- curl for downloading the toolchain
Setting up the cross toolchain
If you have clang and curl installed, runing the scripts/build_sysroot_clang.sh
script will download and build a nasm/binutils/LLVM toolchain configured for building
Popcorn host binaries.
Building and running Popcorn
Once the toolchain has been set up, running generate_build.py will set up the
build configuration, and ninja -C build will actually run the build. If you
have qemu-system-x86_64 installed, the qemu.sh script will to run Popcorn
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-6.0 mtools
sudo update-alternatives /usr/bin/clang clang /usr/bin/clang-6.0 1000
sudo update-alternatives /usr/bin/clang++ clang++ /usr/bin/clang++-6.0 1000