HXNU

HXNU is the new Rust-based kernel line for Neonix. The old heartix/kernel tree remains the legacy reference implementation; new kernel bring-up starts here.

Current Scope

• New repository dedicated to the kernel rewrite
• First release target: 2605 for May 2026
• Hybrid kernel direction
• First target: x86_64
• aarch64 is planned for phase 2, after the x86_64 boot and memory path is stable
• POSIX and legacy Ghost support are planned as compatibility layers
• init startup and process handoff are expected to follow Linux or Unix-like conventions
• ABI compatibility with existing userspace is explicitly deferred until the native kernel core is stable

Licensing

HXNU currently should be treated as GPLv3-or-later.

Reason: the current bootstrap code is not a clean-room implementation. It already reuses Ghost/Heartix-derived implementation material for boot protocol setup and early bring-up structure. See NOTICE.md for the current licensing position.

Repository Layout

• kernel/: Rust kernel crate
• boot/: Limine configuration
• scripts/: bootstrap, ISO build, and QEMU run helpers
• docs/: roadmap and architecture notes

Core design notes live in docs/architecture.md.

Prerequisites

• rustup
• xorriso
• qemu-system-x86_64
• curl
• tar

Bootstrap

./scripts/bootstrap.sh
cargo build -p hxnu-kernel

Current builds use Rust's built-in x86_64-unknown-none target with a custom linker script. A dedicated HXNU target JSON can be introduced later when the kernel ABI and memory model diverge enough to justify it.

Build A Bootable ISO

./scripts/build-iso.sh

prepare-limine.sh first tries to reuse a local ../heartix/target/limine-9.2.0 tree during bootstrap. If that does not exist, it downloads the pinned Limine binary archive for 9.2.0 and stages the required artifacts under vendor/.

build-initrd.sh generates a small cpio newc archive from initrd/ and places it at /boot/initrd.cpio in the ISO. Limine exposes it to the kernel as the initrd boot module.

Run Under QEMU

./scripts/run-qemu.sh

run-qemu.sh prefers Homebrew's QEMU UEFI firmware when available and falls back to plain CD boot otherwise.

Expected first output on the serial console:

HXNU: x86_64 early bootstrap
HXNU: Limine protocol handshake ok
HXNU: Rust kernel skeleton online

Current bring-up logs also include:

• boot-relative timestamps
• HHDM and memory map summary
• UEFI framebuffer or GOP handoff summary
• output-only TTY console bootstrap with serial and framebuffer sinks
• multiple virtual TTY screen foundation with framebuffer redraw and active-console switching
• styled framebuffer console output for accent, success, warning, error, and fatal paths
• frame allocator and heap bootstrap summary
• GDT and IDT activation summary
• CPUID vendor, brand, leaf, and feature summary
• CPUID topology leaf summary from 0x0B/0x1F
• local APIC capability and base-address probe
• local APIC timer one-shot self-test summary
• minimal ACPI discovery with RSDP, XSDT, MADT, and FADT summaries
• SMP topology inventory and AP bring-up target summary from MADT
• read-only procfs snapshot bootstrap
• read-only devfs namespace bootstrap
• minimal VFS mount and read facade for /, /dev, /proc, and /initrd
• normalized VFS path resolution and node lookup facade for mount-backed paths
• cpio newc initrd module discovery and /initrd read path
• /initrd/init executable candidate discovery with format probe
• /initrd/init load-prep inspection for shebang and ELF64 program headers
• ELF PT_LOAD vm-map planning summary with RWX permissions and zero-fill (BSS) accounting
• early Unix-like interpreter resolution fallback from /bin/* to /initrd/bin/*
• periodic scheduler tick bootstrap summary
• scheduler thread and runqueue model summary
• bootstrap to idle context-switch summary
• structured panic and fatal exception reports
• controlled exception self-test output

Self-Tests

The x86_64 bring-up currently supports controlled boot-time self-tests.

• default: breakpoint
• page fault
• general protection fault
• kernel panic
• power reset

Examples:

./scripts/build-iso.sh
./scripts/run-qemu.sh

HXNU_CARGO_ARGS='--features exception-test-page-fault' ./scripts/build-iso.sh
./scripts/run-qemu.sh

HXNU_CARGO_ARGS='--features exception-test-general-protection' ./scripts/build-iso.sh
./scripts/run-qemu.sh

HXNU_CARGO_ARGS='--features panic-self-test' ./scripts/build-iso.sh
./scripts/run-qemu.sh

HXNU_CARGO_ARGS='--features power-reset-self-test' ./scripts/build-iso.sh
./scripts/run-qemu.sh

power-reset-self-test currently reaches the FADT reset-register write path on the default q35 + OVMF + TCG test setup. On this host, serial output stops immediately after the 0xcf9 reset write, so treat it as partial validation until it is cross-checked on another platform.