1b1c587c14
Three services had each written the same thing and got it three different ways: input polled the process list to notice a dead subscriber, and only when someone else subscribed; the power service never noticed at all; the device manager noticed drivers but not subscribers. The harness owns the table now, driven by the events a protocol declares — it registers on the reserved verb, frames each event once, posts to everyone interested without waiting on any of them, and reclaims a slot when the kernel says its owner died. Interest masks moved to the envelope, so a subscriber that wants only mice asks the same way everywhere. Two consequences the plan had not foreseen. The device manager now hears a supervised child's death twice, once as its supervisor and once as a subscriber, so restart backoff counted every crash twice and gave up after half as many; it retires the id before counting. And the kernel's published exit table had eight slots for what is now six subscriptions in a plain boot, so it holds sixteen. The other half is a hole the design named early and left standing: a backend handed out a small integer and then honoured it from anyone. A process that guessed a file's node id read another client's file; a display layer had no owner at all, so any client could reconfigure or destroy any layer; a USB device token was never checked against the client that opened it. Each is now bound to the task that opened it, and a wrong owner gets exactly what an unknown id gets — the refusal must not become the oracle the identical answers elsewhere were designed to remove. Closing a file changed with it: it used to succeed unconditionally, which would have told a caller which ids existed. Suite 111/111, with a new case in which one process holds a file and a layer, hands both ids to a second process, and finds them untouched after that process has tried everything with them. |
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| 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.