0217662808
The compositor now survives the virtio-gpu driver dying and re-attaches when device-manager restarts it — the last piece of display v2. Three parts: - The driver hellos the device manager (role: bus). It never did, so the manager — which spawns it supervised and expects a hello — was stopping it at the 3s hello deadline every run (the gate markers just printed first). Now it is properly supervised: not stopped for silence, and restarted on death. - A kernel IPC fix so a call to a dead service errors instead of hanging. An endpoint records its owner; when that task dies, its registered endpoints are marked dead (and any parked senders woken with -EPEER), so ipc_call returns -EPEER rather than blocking on a reply that will never come. Without this the compositor's first present after the driver died blocked forever. General robustness — any client of any service benefits. - The compositor re-attaches. Its .scanout calls now fail cleanly (caught), freezing the last frame; when the restarted driver re-announces, attach_scanout detects the backend is already virtio and logs "scanout re-attached", mapping the fresh shared surface and re-looking-up .scanout. (The previous shm mapping leaks — no shm_unmap syscall yet — but its frames are the dead driver's, reclaimed on exit.) - device-manager gains a "test-scanout-restart" mode (like test-usb-restart) that kills the virtio-gpu driver once after it hellos; the displayReattachTest kernel scenario drives it. Gate: python3 test/qemu_test.py display-reattach — "scanout upgraded to virtio-gpu" then "scanout re-attached", no CPU exception, passing 3/3. host tests, ipc/ipc-call/ipc-cap, supervision, shm, display-service, display-demo, virtio-gpu, display-native, and display-modeset all pass; default zig build clean. v2 (V1-V6) complete. |
||
|---|---|---|
| boot | ||
| docs | ||
| library | ||
| system | ||
| test | ||
| tools | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| .zig-version | ||
| README.md | ||
| build.zig | ||
| build.zig.zon | ||
README.md
DanOS
Codename: Shodan Version: 1
A small resilient operating system, written from scratch in Zig.
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 lifecyle 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 shortend 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/, and the initial-ramdisk at zig-out/boot/.
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.