Daniel Samson
0a8c81b17a
Add lib/ — the shared user-space runtime every user binary links against (init now, servers/drivers later): syscall wrappers, the heap, IPC stub, and the process start shim. - lib/heap.zig: the kernel first-fit free-list ported to user space, grown via the mmap syscall instead of pmm+mapPage. Dual API over one global free list: extern "C" malloc/free/calloc/realloc (C ABI for future C code) and a std.mem.Allocator adapter (with in-place resize) for Zig std containers. - lib/syscall.zig + sys.zig: raw syscall0..5 (arg3 in r10) and typed yield/write/sleep/exit/mmap/munmap over danos.Syscall. - lib/start.zig: naked _start -> rt_start -> root.main() (SysV realign via call), panic -> exit(127). - lib/user.ld: the user link script, moved from sbin/linker.ld (shared by all user binaries). - build.zig: register the `rt` module; add an addUserBinary() helper that is the one recipe for every user binary (freestanding, .large, use_lld, user.ld, image_base), replacing the bespoke init block. - sbin/init.zig: migrated onto rt; drops its hand-rolled syscall2/shims. Now proves the heap (alloc -> write from a heap pointer -> free) before the heartbeat loop. Serial shows "init: heap ok". Suite 28/28.
DanOS
Codename: Shodan Version: 1
A small operating system, written from scratch in Zig — a bootloader (src/boot/)
and a microkernel (src/kernel/), sharing a neutral handoff contract (src/root.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 the UEFI bootloader (zig-out/bin/BOOTX64.efi) and the kernel ELF
(zig-out/bin/kernel).
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.