Kernel Initialization

Location: kernel/init/
Type: Kernel Core
Status: ✅ Fully Implemented
Components: Driver Init Order, Service Startup, Filesystem Mount, Process Manager, IPC System

Overview

The FreeWorld OS kernel initialization system provides a complete, ordered initialization sequence that ensures all subsystems are started in the correct dependency order. This includes driver initialization, service startup, filesystem mounting, process manager setup, and IPC system initialization.

UEFI-Aware Initialization Phases

UEFI Migration Complete (2025): The kernel now uses UEFI-aware initialization. All hardware information comes from UEFI (no legacy detection needed).

The kernel initialization follows a carefully ordered sequence for UEFI boot:

  1. Kernel Entry (UEFI) - kernel_entry_uefi.asm receives boot parameters, extracts UEFI data (framebuffer, memory map, ACPI RSDP)
  2. Framebuffer Console - Initialize GOP framebuffer console (replaces serial debugging)
  3. IDT Setup - Initialize Interrupt Descriptor Table for exception handling
  4. Physical Memory Manager - Initialize UEFI memory map-based frame allocator (replaces E820)
  5. ACPI Support - Initialize ACPI using RSDP from UEFI System Table (no memory searching)
  6. Interrupt Controllers - Initialize I/O APIC and Local APIC (replaces legacy PIC)
  7. Timers - Initialize HPET using ACPI address (replaces legacy PIT)
  8. Modern Drivers - Initialize USB xHCI, NVMe, AHCI via PCI enumeration
  9. Virtual Memory - Initialize paging, virtual memory, swap
  10. Process Scheduling - Initialize unified scheduler
  11. Kernel Debugging - Initialize KDB and debugging tools
  12. Kernel Logging - Initialize klog and syslog
  13. Kernel Modules - Initialize module system
  14. Power Management - Initialize power management
  15. Process Manager - Initialize process management
  16. IPC System - Initialize inter-process communication
  17. Filesystem Mounting - Mount virtual and root filesystems
  18. Service Startup - Start system services
  19. Init Process - Start initial user-space process

Driver Initialization Order

The driver initialization system ensures drivers are initialized in the correct dependency order across 9 phases:

Phase 0: Critical Drivers (UEFI-Aware)

  • HPET Timer - High Precision Event Timer (replaces legacy PIT)
  • I/O APIC - Modern interrupt controller (replaces legacy PIC)
  • Local APIC - Per-CPU interrupt controller

Phase 1: Storage Drivers (Modern)

  • NVMe Controllers - PCI enumeration, modern SSD support
  • AHCI/SATA Controllers - PCI enumeration, SATA drive support
  • SCSI controllers
  • CD/DVD drives (ATAPI)
  • ⚠️ Legacy ATA PIO - Deprecated, replaced by NVMe/AHCI

Phase 2: Filesystem Drivers

  • FAT32, ext2/3/4, NTFS, exFAT, Btrfs, XFS, ZFS
  • Virtual filesystems: /proc, /sys, /dev, /tmp, devtmpfs

Phase 3: Network Drivers

  • Ethernet drivers (RTL8139, E1000, VirtIO Net)
  • WiFi drivers (structure ready)
  • Bluetooth drivers (structure ready)

Phase 4: Graphics Drivers (UEFI-Aware)

  • GOP Framebuffer - Graphics Output Protocol (replaces VESA/VBE)
  • Framebuffer Console - Text output to GOP framebuffer (replaces serial/VGA)
  • GPU drivers (Intel, AMD, NVIDIA)
  • Display output (DisplayPort, HDMI, DVI)
  • Multi-monitor support
  • ⚠️ VESA/VBE - Deprecated, replaced by GOP

Phase 5: Audio Drivers

  • AC97 driver
  • HD Audio (Intel HDA) driver
  • USB audio (already initialized in USB phase)
  • Audio mixer

Phase 6: Input Drivers (Modern)

  • USB xHCI - USB 3.0+ host controllers (primary)
  • USB HID Devices - Keyboard, mouse via USB (replaces PS/2)
  • Touchpad, touchscreen (structure ready)
  • Game controllers (structure ready)
  • ⚠️ PS/2 Keyboard/Mouse - Deprecated, replaced by USB xHCI

Phase 7: USB Drivers (UEFI-Aware)

  • USB xHCI Controllers - PCI enumeration, modern USB 3.0+ support
  • USB HID devices
  • USB storage
  • USB audio
  • ⚠️ Legacy USB Controllers (UHCI, OHCI, EHCI) - Deprecated in favor of xHCI

Phase 8: Other Drivers

  • Video acceleration drivers
  • Miscellaneous drivers

API Functions

; Complete driver initialization
driver_init_order_complete() -> status

; Individual phase initialization
driver_init_phase_critical() -> status
driver_init_phase_storage() -> status
driver_init_phase_filesystem() -> status
driver_init_phase_network() -> status
driver_init_phase_graphics() -> status
driver_init_phase_audio() -> status
driver_init_phase_input() -> status
driver_init_phase_usb() -> status
driver_init_phase_other() -> status

Service Startup Sequence

The service startup system manages system services in the correct dependency order across 3 phases:

Phase 0: Critical Services

  • Service Manager (must be first)
  • Syslog service (needed for logging)
  • Udev/Devd service (device management)
  • D-Bus service (IPC)

Phase 1: System Services

  • Logd service (logging daemon)
  • Networkd service (network configuration)
  • Securityd service (security daemon)
  • Cron service (scheduled tasks)
  • Resource Manager service
  • IPC Manager service
  • Registry service (Windows compatibility)
  • File System Watcher service
  • Error Manager service

Phase 2: Application Services

  • GUI Server service
  • Display Manager service
  • Shell service (desktop shell)

Phase 3: User Services

User services are started after user login by the session manager.

API Functions

; Complete service startup
service_startup_sequence_complete() -> status

; Individual phase startup
service_startup_phase_critical() -> status
service_startup_phase_system() -> status
service_startup_phase_application() -> status
service_startup_phase_user() -> status

Filesystem Mounting Sequence

The filesystem mounting system handles mounting in the correct order:

Phase 0: Virtual Filesystems

Virtual filesystems are mounted first as they don't depend on storage:

  • /proc - Process and system information
  • /sys - System information and devices
  • /dev - Device nodes
  • /tmp - Temporary filesystem
  • devtmpfs - Automatic device node creation

Phase 1: Root Filesystem

The root filesystem is mounted with support for:

  • Boot parameter specification (root=/dev/sda1)
  • UUID-based mounting (root=UUID=...)
  • Auto-detection (tries common devices)
  • Filesystem type detection (FAT32, ext2/3/4, NTFS, etc.)
  • Mount options parsing
  • Read-only fallback on errors

Phase 2: Other Filesystems

Other filesystems are mounted from configuration (e.g., /etc/fstab).

API Functions

; Complete filesystem mounting
filesystem_mount_sequence_complete() -> status

; Mount root filesystem
mount_root_filesystem_complete() -> status

; Mount virtual filesystems
mount_virtual_filesystems() -> status

; Get root device info
get_root_device() -> device_path
get_root_fstype() -> filesystem_type

Process Manager Initialization

The process manager initialization sets up all process management subsystems:

Components Initialized

  • Process table - Process data structure management
  • Thread table - Thread data structure management
  • PID allocator - Process ID allocation
  • TID allocator - Thread ID allocation
  • Process groups - Process group management
  • Sessions - Session management
  • Signal handling - Signal delivery and handling
  • Process credentials - UID, GID, capabilities
  • Process limits - Resource limits (RLIMIT_*)
  • Process accounting - Process statistics
  • Process namespaces - Namespace isolation
  • Process monitoring - Process health monitoring

Kernel Process

Creates the kernel process (PID 0) which serves as the root of the process tree.

API Functions

; Initialize process manager
process_manager_init_complete() -> status

; Get init process PID
process_manager_get_init_pid() -> pid

; Check if initialized
process_manager_is_initialized() -> initialized

IPC System Initialization

The IPC system initialization sets up all inter-process communication mechanisms:

Components Initialized

  • Shared memory system - Shared memory segments
  • Message queues - POSIX message queues
  • Semaphores - POSIX semaphores
  • Pipes - Anonymous pipes
  • FIFOs - Named pipes
  • Sockets - Network sockets (if not already done)
  • Signals - Signal-based IPC (if not already done)
  • D-Bus - D-Bus IPC (if available)
  • IPC namespace - IPC namespace isolation
  • IPC permissions - Permission management
  • IPC monitoring - IPC usage monitoring

API Functions

; Initialize IPC system
ipc_system_init_complete() -> status

; Check if initialized
ipc_system_is_initialized() -> initialized

Error Handling

The initialization system includes comprehensive error handling:

  • Critical Failures - Process manager, IPC system, root filesystem mount failures cause system halt
  • Non-Critical Failures - Driver, service, and graphics failures are logged but don't halt the system
  • Fallback Mechanisms - System continues with available components
  • Error Logging - All errors are logged via klog

Build System

Initialization components are built using the Makefile in kernel/init/:

cd kernel/init
make

This produces object files that are linked into the kernel:

  • kernel_init.o - Main initialization sequence
  • driver_init_order.o - Driver initialization order
  • service_startup_sequence.o - Service startup sequence
  • filesystem_mount_sequence.o - Filesystem mounting
  • process_manager_init.o - Process manager initialization
  • ipc_system_init.o - IPC system initialization

Integration

The initialization system integrates with:

  • Boot System - Receives boot parameters and hardware info
  • ACPI - Uses ACPI device tree for hardware enumeration
  • Memory Management - Uses frame allocator for memory allocation
  • Process Management - Initializes process management before starting init
  • Filesystem - Mounts filesystems before starting services
  • Services - Starts services in dependency order
  • Logging - Uses klog for initialization logging