cbof is the kernel of CharlotteOS. It is a monolithic kernel that is designed to provide a flexible and low level interface to program running ontop of it.

cbof is the successor to Charlotte Core our previous kernel in development. The kernel was redeveloped due to a lack of sufficient modularity, compatibility with the C ABI in all public interfaces, and improper code organization which could not be easily refactored in place. cbof is the result of that redevelopment though it does reuse a substantial amount of code from Charlotte Core. A fork of Charlotte Core is available as an archive in the CharlotteOS GitHub organization.

cbof is in very early development and does not yet support a userspace. Run it at your own risk.

cbof is written in Rust and Assembly language

• x86_64-unknown-none
• aarch64-unknown-none
• riscv64gc-unknown-none-elf

• Device firmware is required to either implement both UEFI and ACPI or the EBBR standard on all targets

The following commands are used to build the debug and release versions of the kernel.

make build-x86_64-debug    # debug
make build-x86_64-release  # release

make run-x86_64-debug    # For testing a debug build in qemu
make run-x86_64-release  # For testing a release build in qemu

The x86_64 portion of any of the previous commands can be replaced with aarch64 or riscv64 to build the kernel for the Arm and RISC-V architectures respectively however it should be noted that support for these ISAs is much less complete than for x86_64 for the time being.

Follow the steps in the Building section above, replacing make run-x86_64-debug for run-x86_64-debugprobe, this will start qemu, but it will appear unresponsive this is because it's waiting for gdb to connect, on linux this can be achieved by in another terminal running:

gdb charlotte_core/target/x86_64-unknown-none/debug/charlotte_core

and once gdb is open:

(gdb) target remote localhost:1234
make sure to set some breakpoints or the code will just go straight to the halt at the end of main currently
(gdb) c

OR Use the .gdbinit file present in the repo, to do this you need to allow gdb to load the .gdbinit file, this can be accomplished by adding add-auto-load-safe-path [path to the repo here]/.gdbinit to $HOME/.config/gdb/gdbinit, wit this done you just need to run:

# in terminal 1
make run-x86_64-debugprobe
# in another terminal
gdb

if you are currently in the repo main folder you may use the snippet bellow to add the loading allow to gdbinit

mkdir -p $HOME/.config/gdb/;echo "add-auto-load-safe-path $(pwd)/.gdbinit" >> $HOME/.config/gdb/gdbinit

further reference Qemu GDB docs

Detailed documentation will eventually be available in this repository's GitHub wiki and at CharlotteOS's website.

Contributions are always welcome and highly appreciated. Please create a new branch for your work and submit a pull request on GitHub. Make sure to rebase all your changes on master to maintain a linear commit history avoiding merge commits to the extent possible. Feel free to grab any unassigned issues in the GitHub issue tracker for this repository.

Also please join our community on Discord to stay up to date with the latest on CharlotteOS development.