Daniel Samson
a5fe63c1dd
Processes now start with C-compatible arguments: the kernel builds the System V AMD64 entry block (argc, argv, empty envp, auxiliary vector) at the top of the stack, argv[0] is the path or initial-ramdisk name the process was spawned as, and system_spawn carries an optional NUL-separated blob that becomes argv[1..]. The runtime parses the block (runtime.argumentCount/argument) and its spawn wrappers pass arguments through. The name is also recorded on the task, so a fault report says which binary died, not just its id. The user stack grows from one page to eight (32 KiB, parameters.user_stack_pages), with the page below left unmapped as a guard so an overflow faults into a clean process kill rather than corrupting the image. Task.name_buffer is zero-initialised, not undefined: an undefined default is materialised as a 0xAA fill that moved the static task pool out of .bss and made the whole kernel ~7x slower under QEMU TCG (caught by the affinity test). Proven end to end by the new args test: args-echo respawns itself with arguments via the syscall blob, burns more stack than one page could hold, and echoes its argv intact. Full suite: 44/44.
DanOS
Codename: Shodan Version: 1
A small operating system, written from scratch in Zig — a bootloader (boot/)
and a microkernel (system/kernel/), sharing a neutral handoff contract (system/boot-handoff.zig).
It boots x86-64 via UEFI, and so far has a framebuffer console, a physical frame
allocator, its own paging with W^X permissions, interrupt/exception handling, a
LAPIC timer, a kernel heap, a fixed-priority preemptive scheduler, and in-kernel IPC
channels. See docs/ for how each piece works.
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 the why behind the code live in
docs/ — start with docs/README.md.
Logo
San Serif Text "Dan OS" with a black karate belt around it.