Daniel Samson
6328823ef1
The driver read the first 512 bytes of a configuration block into a fixed buffer and parsed those. The block's length is the device's own choice (wTotalLength, a u16), so anything larger was silently cut: interfaces past the cut did not exist as far as the host was concerned, while the SET_CONFIGURATION that follows still configured the device for all of them. A headset is 500-900 bytes, a UVC webcam 1-3 KB, a multifunction printer 600+. Now allocated at the declared length, so the ceiling is the field's u16 — the specification's number rather than one of ours. A block shorter than its own 9-byte header is refused rather than trusted. The bring-up line reports the declared length and the bytes actually read, so a truncation can never again be invisible, and usb-large-descriptor asserts they match with a backreference. That case has an honest limit, recorded in its comment: QEMU cannot produce a block over 512 bytes. The boot keyboard, mouse and stick are 34-44, and the largest device available is usb-audio in multi-channel mode at 211 — which is exactly why the suite never caught this, and why it cannot now reproduce the original trigger. What it does catch is the class: any clamp below the attached device's block fails it, verified by pinning the buffer to 128 and watching "config block 211 bytes, read 128" turn the case red. Suite 115 -> 116.
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.