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Operating System written for me
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Daniel Samson 5ab7263c9c display-demo: stop drawing a cursor and stop blocking on the mouse 
Two real bugs visible in a normal `zig build run-x86-64` boot (but not in the
display-demo test, which spawns no input service):

  - Two cursors. The demo drew its own cursor layer while the display service
    now draws one too (its mouse-listener thread). The demo's went through the
    client IPC protocol and lagged; the service's is in-process and tracks
    tightly — "one responds better than the other."

  - Animation frozen until the mouse moves. The demo called a *blocking*
    `mouse.next()` (ipc_reply_wait) inside its animation loop, so the sliding
    box advanced only one frame per mouse event. In the display-demo test
    there is no input service, so subscribeMouse() returned null and the loop
    ran free on its 30ms timer — which is exactly why the test passed while
    the real boot was broken.

The compositor now owns the cursor (docs/display.md), so the demo should draw
none and read no input: it becomes a pure client-animation proof whose loop is
independent of the mouse. Removes its cursor layer, mouse subscription, and the
blocking read.

Also harden displayDemoTest to spawn the `input` service alongside the demo
(matching real boot): a client that blocks its animation loop on a mouse read
would now stall before `display-demo: ok` and fail the test, instead of
passing because no input service happened to be present.

Verified: display / display-service / display-demo / display-cursor all green.
 		2026-07-21 02:37:47 +01:00
boot serial: make the log sink a build option, off by default 2026-07-13 22:05:08 +01:00
docs display-demo: stop drawing a cursor and stop blocking on the mouse 2026-07-21 02:37:47 +01:00
library docs+code: drop misleading fs.base notation for the thread pointer 2026-07-21 01:52:10 +01:00
system display-demo: stop drawing a cursor and stop blocking on the mouse 2026-07-21 02:37:47 +01:00
test display: track the mouse with a listener thread (Shape A) + cursor 2026-07-21 02:31:29 +01:00
tools build: release-x86-64 — the flashable hybrid ISO (Etcher/dd + optical), built in-repo 2026-07-20 13:37:10 +01:00
usr/share/fonts assets: add font families under usr/share/fonts 2026-07-14 18:39:23 +01:00
.editorconfig editorconfig 2026-07-12 16:09:11 +01:00
.gitattributes gitattributes 2026-07-12 16:09:18 +01:00
.gitignore gitignore: ignore .claude/ and .github/ 2026-07-10 14:09:38 +01:00
README.md update README.md 2026-07-20 13:39:03 +01:00
build.zig display: track the mouse with a listener thread (Shape A) + cursor 2026-07-21 02:31:29 +01:00
build.zig.zon started project with basic efi setup 2026-07-01 18:32:56 +01:00

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 or zigup will pick up .zig-version automatically.
  • QEMU (qemu-system-x86_64) — to run and test the kernel. On macOS, brew install qemu also bundles the OVMF firmware below.
  • OVMF UEFI firmware — the edk2-ovmf package (Arch), ovmf (Debian/Ubuntu), or edk2-ovmf (Fedora); on macOS it ships inside the Homebrew qemu formula. 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/.

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.

San Serif Text "Dan OS" with a black karate belt around it.