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Roadmap

DaedalusOS development phases and milestones.

Project Goals

  • Primary: Learning project for OS internals and bare-metal ARM programming
  • Target: Raspberry Pi 4 exclusively (see ADR-001)
  • End Vision: Network-enabled device for remote GPIO control via HTTP
  • Development: Incremental milestones, each delivers working feature
  • Learning Focus: Hardware/driver layer (implement from scratch), protocols/algorithms (use existing no_std crates)

Current Status

Phase 4 In Progress 🔄 - Networking Stack Milestone #13 Complete ✅ - Frame Transmission & Reception

  • Working REPL with command parsing and shell history
  • Exception vector table with register dumps
  • 8 MB heap with bump allocator
  • Full alloc crate support (Box, Vec, String, collections)
  • System timer driver with microsecond precision delays
  • GIC-400 interrupt controller with interrupt-driven UART
  • MMU with 39-bit virtual address space (identity mapped)
  • Caching enabled for performance
  • GPIO driver with BCM2711 pull-up/down support
  • Shell commands for GPIO pin control (mode, pull, set, get, toggle)
  • GENET Ethernet controller with full TX/RX capability
  • VideoCore mailbox driver for querying firmware properties
  • MAC address retrieved from OTP (One-Time Programmable memory)
  • Ethernet and ARP protocol structures with 30 unit tests
  • Shell commands: eth-diag (diagnostics), arp-probe (TX/RX test)

Next: Milestone #14 - Interrupt-driven networking

Phase 1: Interactive Shell ✅ COMPLETE

Goal: Usable REPL running in QEMU

Completed Milestones:

  1. Boot & Console - Assembly entry, UART TX
  2. Testing Infrastructure - Custom test framework with QEMU
  3. UART Input - Polling RX, line editing (backspace, Ctrl-U, Ctrl-C)
  4. Command Parser - Line buffering, argument splitting
  5. Shell Loop - REPL with prompt, built-in commands (help, echo, clear, version, meminfo)
  6. Exception Vectors - 16-entry table, context save/restore, ESR/FAR decoding

Current Features:

  • Interactive shell prompt (daedalus>)
  • Commands: help, echo, clear, version, meminfo, exception
  • Line editing: backspace, Ctrl-U (clear line), Ctrl-C (cancel)
  • Full exception handling with register dumps

Phase 2: Memory & Interrupts ✅ COMPLETE

Goal: Dynamic allocation and interrupt-driven I/O

Milestone #7: Heap Allocator ✅ COMPLETE

  • ✅ Integrated Rust alloc crate
  • ✅ Simple bump allocator for shell history
  • ✅ Enabled String, Vec, collections
  • ✅ 8 MB heap region with proper alignment
  • ✅ Memory tracking (heap_size, used, free)
  • ✅ 6 allocator tests (Box, Vec, String, capacity, stats)

Milestone #8: System Timer ✅ COMPLETE

  • ✅ Configured BCM2711 system timer (base 0xFE003000)
  • ✅ Implemented delay functions (delay_us, delay_ms)
  • ✅ Added timestamp and uptime tracking functions
  • ✅ Added uptime shell command
  • ✅ 6 timer tests (counter, delays, monotonicity)
  • ✅ Comprehensive hardware documentation

Milestone #9: GIC-400 Setup ✅ COMPLETE

  • ✅ Initialize interrupt controller
  • ✅ Configure UART interrupts
  • ✅ Interrupt-driven I/O (replaced polling)

Milestone #10: MMU & Paging ✅ COMPLETE

  • ✅ 3-level translation tables with 2 MB block mappings
  • ✅ Identity map kernel (1 GB normal memory)
  • ✅ Identity map MMIO (device memory, non-cacheable)
  • ✅ 39-bit virtual address space (512 GB)
  • ✅ Memory attributes (cacheable normal, device-nGnRnE)
  • ✅ Shell command (mmu) for debugging MMU status
  • ✅ Comprehensive documentation

Phase 3: Hardware I/O 🔄 IN PROGRESS

Goal: Foundation for real-world device control

Milestone #11: GPIO Driver ✅ COMPLETE

  • ✅ Pin configuration (input/output, alt functions 0-5)
  • ✅ BCM2711 pull-up/down resistor control (new register mechanism)
  • ✅ Digital I/O (read/write/toggle GPIO pins)
  • ✅ Shell commands: gpio-mode, gpio-pull, gpio-set, gpio-get, gpio-toggle
  • ✅ Support for all 58 GPIO pins (BCM2711)
  • ✅ Comprehensive hardware documentation

Phase 4: Networking Stack 🔄 IN PROGRESS

Goal: Network-enabled device (the primary objective)

Milestone #12: Ethernet Driver Foundation ✅ COMPLETE

  • ✅ GENET v5 hardware detection and register access
  • ✅ MDIO protocol implementation (PHY communication)
  • ✅ BCM54213PE PHY detection and identification
  • ✅ Ethernet frame structures and parsing
  • ✅ ARP packet structures and parsing
  • ✅ Network byte order handling
  • ✅ 30 protocol unit tests passing
  • ✅ Comprehensive documentation (hardware, protocols, verification)
  • ✅ Shell command: eth-diag (hardware diagnostics)

Milestone #13: Frame Transmission & Reception ✅ COMPLETE

  • ✅ Frame TX implementation (polling mode with DMA descriptors)
  • ✅ Frame RX implementation (polling with ring buffers)
  • ✅ VideoCore mailbox driver for firmware communication
  • ✅ MAC address queried from OTP via mailbox (real hardware MAC)
  • ✅ Bus address translation (ARM physical → VideoCore bus)
  • ✅ Cache-line aligned message buffers (64-byte alignment)
  • ✅ Frame validation and error handling
  • ✅ Shell command: arp-probe (comprehensive TX/RX diagnostics)

Milestone #14: Interrupt-Driven Networking

  • Register GENET interrupts with GIC
  • RX interrupt handler
  • TX completion handling
  • Frame queuing for processing

Milestone #15: ARP Responder

  • ARP cache implementation with expiration
  • ARP request/reply handling
  • Respond to ARP requests for our IP
  • Shell command: arp-cache

Milestone #16: TCP/IP Stack Integration (smoltcp)

  • Integrate smoltcp no_std TCP/IP stack
  • Implement Device trait (maps to GENET driver)
  • IPv4 packet handling
  • ICMP echo (ping support)
  • DHCP client for IP configuration
  • UDP/TCP socket support

Milestone #17: Application Protocols

  • DNS resolver (A records)
  • HTTP/1.1 client (GET/POST)
  • Simple HTTP server for device control
  • Shell commands: ping, http-get, gpio-server

Phase 5: Advanced Features (Future Self-Implementation)

Goal: Optimizations and advanced capabilities

Milestone #18: DMA Controller

  • DMA channel setup
  • Optimize Ethernet for DMA-based transfers
  • Improve SD card performance (when implemented)

Milestone #19: Better Allocator

  • Replace bump allocator with buddy or slab allocator
  • Free/reallocation support
  • Fragmentation management

Milestone #20: Multi-Core Support

  • Wake secondary cores (cores 1-3)
  • Spinlocks and synchronization primitives
  • Per-core data structures

Milestone #21: Cooperative Scheduler

  • Task switching for async I/O
  • Event-driven network processing
  • Timer-based task scheduling

Phase 6: Storage & Persistence (Optional)

Goal: Persistent storage and filesystems

Milestone #22: SD Card Driver

  • EMMC controller initialization
  • Block read/write operations
  • Interrupt-driven I/O

Milestone #23: FAT32 Filesystem

  • Parse FAT32 structures
  • File operations (open, read, write, close)
  • Directory traversal

Phase 7: Advanced Hardware (Optional)

Goal: Additional peripherals and buses

Milestone #24: I2C/SPI Drivers

  • Bus initialization
  • Multi-device support
  • Sensor integration

Milestone #25: USB Host Controller

  • xHCI/EHCI initialization
  • USB device enumeration
  • Keyboard/mouse/storage support

Phase 8: Userspace (Optional)

Goal: Process isolation and privilege separation

Milestone #26: EL0 Userspace

  • Drop to EL0 for user programs
  • System call interface (SVC handler)
  • User/kernel memory isolation

Milestone #27: Process Management

  • Process creation/termination
  • Basic IPC mechanisms
  • Resource limits and scheduling

Development Practices

Each milestone must:

  1. Pass pre-commit script with no errors or warnings (./.githooks/pre-commit)
    • This verifies: formatting, clippy, documentation, tests, and build
  2. Run in QEMU (cargo run) for interactive verification
  3. Update documentation (code docs, milestone summary, and relevant guides)

Documentation Requirements

After each milestone, update:

  • README.md - Quick start, expected output
  • Roadmap (this file) - Mark milestone complete
  • Hardware docs - New peripherals
  • Architecture docs - New features