d2dfbcabf8
The folded header stops being a rule in a document and becomes the layout on the wire. Verbs number from sixteen, leaving describe, enumerate, subscribe and unsubscribe reserved and answered the same way by every provider — none of them writes a line to do it. What each protocol used to carry in a field of its own now travels in the header: a vfs node and a display layer are the packet's target, and a reply opens with a status the envelope stamps rather than one each protocol spelled for itself. Display gains the most. One forty-byte request had served eleven verbs, so attach_scanout smuggled stride through x, refresh through y and format through colour, and every coordinate crossed as a bitcast. Per-operation structs end all three: the fields have their own names and their own signs, and the tile payload grows to 224 bytes because the prefix shrank. Scanout loses a message maximum of 64 it had no business declaring — it answers calls, and the floor for a call is 256 — and virtio-gpu stops hard-coding that number at its harness. Two changes are semantic rather than notational. A directory now ends at an entry with no name, because the fixed part of a reply always travels and a zero-length reply no longer exists to mean anything. And input joins the service harness, the last loop in the tree that answered no ping and heard no terminate; its subscriber table, its pruning and its fan-out are the same code, and a shutdown now asks it to stop instead of killing it. A new conformance case reads the registry's own listing and asks every protocol it finds for its name, its version and its verb count, then offers a verb nobody defines and requires -ENOSYS — the envelope's promise, checked against providers rather than against itself. What it cannot reach in that boot it names on the serial line instead of passing quietly. Suite 110/110. |
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|---|---|---|
| boot | ||
| build | ||
| build-support | ||
| docs | ||
| library | ||
| system | ||
| test | ||
| tools | ||
| usr/share/fonts | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| README.md | ||
| build.zig | ||
| build.zig.zon | ||
README.md
DanOS
Codename: Shodan
A very small resilient operating system.
Zen of DanOS:
- Resilient Micro-Kernel Architecture.
- Every process run in an isolated user space not kernel space.
- Processes cannot take down the entire OS with it when they die or is killed
- Stable public runtime library, private OS ABI.
- Keeps a stable runtime for user space processes between OS versions (great for backwards compatibility)
- Allows the underlying OS to be changed without effecting applications
- Provides a boundary to enable compatibility between OS's e.g. POSIX, MUSL etc
- Drivers are just isolated processes in user space.
- Thin binaries that can be restarted like applications.
- Useful during driver development.
- Drivers can claim MMIO / ports
- Driver resources (e.g. IRQ/Port/MMIO) claims are automatically cleaned up if the driver dies or is killed
- Drivers can also hook into the process lifecycle to clean up or reset hardware
- No legacy to deal with
- Zig code uses a clean coding style (Zen of Zig)
- Favor reading code over writing code.
- No magic numbers.
- No shortened names unless its for ABI compatibility or acronyms
- Inter-Process Communication (IPC)
- Publish and subscribe to Asynchronous Messages
- Talk to services and processes synchronously
Prerequisites
- Zig 0.16.x — the build is pinned to this line (
.zig-version); other minor versions are rejected, because Zig makes breaking changes between releases pre-1.0. A toolchain manager such as zvm orzigupwill pick up.zig-versionautomatically. - QEMU (
qemu-system-x86_64) — to run and test the kernel. On macOS,brew install qemualso bundles the OVMF firmware below. - OVMF UEFI firmware — the
edk2-ovmfpackage (Arch),ovmf(Debian/Ubuntu), oredk2-ovmf(Fedora); on macOS it ships inside the Homebrewqemuformula. Both the build and the test harness probe the known Arch/Debian/Fedora/macOS layouts and use the first that exists, so no configuration is normally needed. Override with-Dovmf-code=/-Dovmf-vars=(build) if yours lives elsewhere. - Python 3 — for the QEMU integration test harness.
Build
zig build
Produces a FHS-shaped zig-out/ that is the danos filesystem and the boot volume:
the UEFI bootloader at zig-out/EFI/BOOT/BOOTX64.efi, the kernel at
zig-out/system/kernel, init at zig-out/system/services/init, drivers under
zig-out/system/drivers/, the test fixtures under zig-out/test/system/services/,
and the initial-ramdisk at zig-out/boot/.
Release media
zig build release-x86-64
Produces zig-out/danos-x86-64.iso, a hybrid ISO that boots flashed raw to a
USB stick (balenaEtcher, dd) or burned to optical media — see
docs/release-iso.md. zig build check-iso-image
validates it without booting.
Run
Boot it in QEMU with OVMF (opens a display window):
zig build run-x86-64
# distro with OVMF elsewhere:
zig build run-x86-64 -Dovmf-code=/path/OVMF_CODE.fd -Dovmf-vars=/path/OVMF_VARS.fd
Test
zig build test # host unit tests (the platform-independent shared code)
python3 test/qemu_test.py # QEMU integration tests: boots the kernel and asserts
# on its serial output (see docs/testing.md)
The integration harness builds and boots the kernel once per test case, checking memory, the frame allocator, paging (incl. NX and the null guard), the heap, interrupts, and exception handling. It exits non-zero on any failure, so it drops straight into CI.
Documentation
Design notes explaining why behind the code live in
docs/ — start with docs/README.md.
For the hardware needed to run DanOS — minimum specs plus a plain-language guide
matching Intel/AMD CPU generations by name — see
docs/system-requirements.md.
Logo
San Serif Text "Dan OS" with a black karate belt around it.