Separate abstractions from implementations following DIP:
servers/ drivers/
│ │
▼ ▼
ports/ (trait-only crates, zero deps)
New crates:
ports/ (abstractions):
- port-framebuffer: Framebuffer trait
- port-block-device: BlockDevice trait + SectorId
- port-input-device: InputDevice trait + InputEvent types
drivers/ (implementations depend on ports/):
- driver-framebuffer-virtio: VirtIO GPU framebuffer
- driver-framebuffer-mock: test double
- driver-block-virtio: VirtIO block device
bins/ (composition roots wire server + driver):
- display-qemu: DisplayServer<VirtioFramebuffer>
- storage-qemu: storage server with VirtIO block
Servers no longer own their hardware traits or driver code.
Neither server nor driver depends on the other — both point
inward to the port abstraction.
Complete microkernel boot pipeline: adapter loads only init + storage + display
from disk. Init bootstraps all other servers by reading binaries from the
storage server via IPC, parsing ELF, creating processes, mapping pages, and
spawning threads.
New syscalls:
- CreateEndpoint: userspace endpoint creation with full capability grant
- DebugPutchar: debug output to UART from userspace
- MapPage: cross-process page mapping (init loads binaries into children)
- SpawnThreadIn: spawn thread in another process via capability
Key fixes:
- Per-process L1 page tables for VPN[2]=0 (prevents cross-process corruption)
- Separate kernel_pt from page_tables[0] (init pid=0 overwrote kernel PT ref)
- Thread Running state set in switch_to_next (syscalls rejected without it)
- Pending IPC results applied during context switch
- SIE disabled during boot (timer can't preempt into unready processes)
- User heap VA starts at 0x40000 (avoids shared buffer at 0x30000)
- RequestPages maps at user VAs via per-process heap allocator
VirtIO GPU:
- Adapter probes for GPU device, initializes resource/scanout/backing
- Display server writes to mapped framebuffer, flushes via GPU virtqueue
- 640x480 BGRA framebuffer with transfer-to-host and resource-flush
Storage server:
- Userspace VirtIO block driver using pre-mapped MMIO and DMA pages
- FAT16 filesystem reader serving file-read requests via IPC
- Shared buffer protocol: init writes filename, storage writes file data
Echo app for IPC testing (adapter-loaded echo proved the pipeline end-to-end).
Every server now has lib.rs (testable) + main.rs (deployable binary).
Binary is 3 lines: extern crate userspace_rt + call run().
Hardware servers use feature flags for adapter selection.
9 RISC-V binaries ready for the disk image.
