foliOS

foliOS is an experimental operating system built around Strata, a kernel that explores the Ambikernel model. Conventional process isolation remains the baseline. Selected signed modules may execute in explicit kernel-adjacent domains when lower transition overhead justifies the additional runtime contract.

This repository contains experimental research code. Its documentation records implemented behavior, intended invariants, and planned design work; some mechanisms remain incomplete.

Core Ideas

Strata separates execution into three conceptual strata:

• User space contains ordinary processes with isolated address spaces. They access kernel services through KRT syscall entry points.
• Signed modules may execute in kernel-adjacent domains under explicit runtime gates, module contexts, and protection state.
• The kernel retains authority over physical memory, page tables, scheduling, interrupt routing, handle tables, and system-wide recovery.

The Ambikernel model keeps component ownership visible across separate domains. Selected driver and service paths may avoid process-style IPC when the ABI clearly specifies memory lifetime, authority, and fault attribution.

The design relies on the following mechanisms:

• Module protection shards provide scalable module isolation without making architecture-specific hardware-key limits part of the generic ABI.
• KRT defines the entry points for current user-to-kernel transitions and planned module calls.
• Cross-domain sharing uses descriptors with explicit ownership, lifetime, and revocation rules rather than raw pointers.
• GNT provides a capability-oriented global namespace for kernel services, device interfaces, files, and resources managed by the planned package system.
• stload defines the normalized boot-information contract between the loader and Strata.

Current Focus

• Strata's memory model and module isolation boundary.
• The stload loader-to-kernel handoff ABI.
• Vellum's BIOS boot path and QEMU-based development workflow.
• The foliSDK build pipeline for the kernel, runtime, and user-space components.

Components

• Strata is the kernel and the project's main architectural experiment.
• Vellum provides the BIOS bootloader core and its module environment.
• load_folios is a Vellum module that loads Strata and builds the stload handoff table passed to the kernel.
• foliSDK supplies the toolchain, C runtime, and build environment for the kernel and user-space components.
• docs/ contains architecture notes, subsystem references, ADRs, and development guides.

Read Next

• Architecture
• Ambikernel
• Boot Flow
• Strata Memory
• Global Node Tree
• stload ABI
• Build
• Disk Images

Build & Run

Prerequisites:

• Python 3 and the foliSDK host prerequisites.
• i686-elf-gcc for the IA-32 BIOS bootloader build.
• QEMU for local testing.

git clone https://github.com/kms1212/foliOS --recursive
cd foliOS

(cd folisdk && ./build.py --arch x86_64 --builddir-layout --jobs 18)
export PATH="$(pwd)/folisdk/build/folisdk-host/bin:$(pwd)/folisdk/build/folisdk-x86_64/bin:$PATH"

folisdk/build/folisdk-host/bin/cmake \
    -S . \
    -B build \
    -DCMAKE_BUILD_TYPE=Debug \
    -DTARGET=amd64-pc-bios \
    -DCMAKE_EXPORT_COMPILE_COMMANDS=ON

folisdk/build/folisdk-host/bin/cmake --build build --parallel=18

scripts/mkdisk.sh -a ia32 disk.img
scripts/run.sh --disk disk.img pc-amd64

The -a ia32 disk-image option selects the BIOS bootloader architecture. For the amd64-pc-bios target, Strata targets AMD64, but the Vellum BIOS loader is built for IA-32.

License

foliOS, Vellum, and Strata are licensed under the Apache License, Version 2.0. See LICENSE for details.