Daniel Samson
d19a0ae38d
The shared kernel<->user ABI contract (BootInformation, the SystemCall numbers, DeviceDescriptor, page_size, ...) is now the `system` module at system/system.zig, following the convention that a directory's root file takes the directory's name. One overlap to note: the runtime's syscall wrappers are already `runtime.system`, so the single file that uses both the contract and those wrappers (library/runtime/heap.zig) aliases the wrappers locally as `system_calls`. The two are distinct (top-level `system` vs `runtime.system`); everywhere else the contract is just `system`. Also: the QEMU run's serial capture now lands in the FHS log location, zig-out/var/log/system/serial0-<timestamp>.log — a stand-in for the kernel's own logging system, which will eventually write there itself. Suite 35/35 plus host tests green.
69 lines
2.7 KiB
Markdown
69 lines
2.7 KiB
Markdown
# DanOS
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Codename: Shodan
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Version: 1
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A small operating system, written from scratch in Zig — a bootloader (`boot/`)
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and a microkernel (`system/kernel/`), sharing a neutral handoff contract (`system/system.zig`).
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It boots x86-64 via UEFI, and so far has a framebuffer console, a physical frame
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allocator, its own paging with W^X permissions, interrupt/exception handling, a
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LAPIC timer, a kernel heap, a fixed-priority preemptive scheduler, and in-kernel IPC
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channels. See [`docs/`](docs/README.md) for how each piece works.
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## Prerequisites
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- **Zig 0.16.x** — the build is pinned to this line (`.zig-version`); other minor
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versions are rejected, because Zig makes breaking changes between releases
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pre-1.0. A toolchain manager such as [zvm](https://github.com/tristanisham/zvm)
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or `zigup` will pick up `.zig-version` automatically.
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- **QEMU** (`qemu-system-x86_64`) — to run and test the kernel. On macOS,
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`brew install qemu` also bundles the OVMF firmware below.
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- **OVMF** UEFI firmware — the `edk2-ovmf` package (Arch), `ovmf` (Debian/Ubuntu),
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or `edk2-ovmf` (Fedora); on macOS it ships inside the Homebrew `qemu` formula.
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Both the build and the test harness probe the known Arch/Debian/Fedora/macOS
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layouts and use the first that exists, so no configuration is normally needed.
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Override with `-Dovmf-code=` / `-Dovmf-vars=` (build) if yours lives elsewhere.
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- **Python 3** — for the QEMU integration test harness.
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## Build
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```sh
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zig build
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```
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Produces a FHS-shaped `zig-out/` that *is* the danos filesystem and the boot volume:
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the UEFI bootloader at `zig-out/EFI/BOOT/BOOTX64.efi`, the kernel at
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`zig-out/system/kernel`, init at `zig-out/system/services/init`, drivers under
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`zig-out/system/drivers/`, and the initial-ramdisk at `zig-out/boot/`.
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## Run
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Boot it in QEMU with OVMF (opens a display window):
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```sh
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zig build run-x86-64
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# distro with OVMF elsewhere:
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zig build run-x86-64 -Dovmf-code=/path/OVMF_CODE.fd -Dovmf-vars=/path/OVMF_VARS.fd
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```
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## Test
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```sh
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zig build test # host unit tests (the platform-independent shared code)
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python3 test/qemu_test.py # QEMU integration tests: boots the kernel and asserts
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# on its serial output (see docs/testing.md)
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```
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The integration harness builds and boots the kernel once per test case, checking
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memory, the frame allocator, paging (incl. NX and the null guard), the heap,
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interrupts, and exception handling. It exits non-zero on any failure, so it drops
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straight into CI.
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## Documentation
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Design notes explaining the *why* behind the code live in
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[`docs/`](docs/README.md) — start with [`docs/README.md`](docs/README.md).
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## Logo
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San Serif Text "Dan OS" with a black karate belt around it.
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