Daniel Samson
a581712b09
ipc_call and ipc_reply_wait grow a `send_cap` argument (r9) and a `received_cap` return (r8): an endpoint travels alongside a message, installed into the receiver's handle table. The transfer is a share, not a move — the endpoint's refcount is bumped and the sender keeps its handle. If the receiver's table is full the call fails -ENOSPC and the message is NOT delivered (a half-delivered capability is worse than a failed send); a bad handle fails -EBADF. Both directions carry a cap: a client's call hands one to the server (seen in the server's replyWait), and the server's reply hands one back (seen in the client's call return). This is the "open" primitive the driver model was blocked on: a bus driver mints a per-device endpoint and hands it to a class driver, giving it a private channel to one device without the 8-slot global name registry. Kernel: shareCapability in ipc-synchronous.zig at both copy points; new setSystemCallResult3 (r8, saved/restored by the syscall stub); Task gains ipc_send_cap / ipc_received_cap. Runtime: callCap + Reply, replyWait gains send_cap and Received.cap; plain call/replyWait delegate with no_cap. New abi.no_cap. New ipc-cap test (two kernel tasks exercise both directions, each verifying the endpoint it received is the same object shared, refcount bumped to 2). No class driver consumes callCap yet — it lands with the first one. Suite 37/37 plus host tests.
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.