ALOS - Alexy Operating System

ALOS is a minimalist operating system kernel written in C and x86 Assembly, designed for learning purposes and running on QEMU. It implements core OS concepts including memory management, interrupt handling, storage, filesystem support, and a TCP/IP networking stack.

Note: Code comments in this project are written in French. The codebase serves as both a learning resource and a functional kernel.

Features implemented and future plans

Core System ✓

• GDT/IDT setup
• Physical Memory Manager
• Kernel Heap
• Virtual Memory (Paging) - Identity mapping
• RTC Real-Time Clock
• PIT Programmable Interval Timer
• Kernel Logging System (file-based, /system/logs)
• System logs
• ACPI Support (power management, shutdown/reboot)
• SMP/Multi-core support
• APIC/x2APIC (Advanced interrupt handling)
• Kernel modules loading (dynamic drivers)

Memory Management

• Virtual Memory (Paging) - Identity mapping
• Demand paging / Page fault handler
• Copy-on-Write (COW)
• Memory-mapped files (mmap)
• Shared memory (SHM)
• Swap support

Process & Scheduling

• Multitasking (Round Robin scheduler)
• Context Switching (kernel threads)
• User Space (Ring 3) with TSS
• System Calls (POSIX/BSD-like interface)
• Priority-based scheduler
• Process groups and sessions
• Fork/exec implementation
• Signals (POSIX-like)
• Real-time scheduling (SCHED_FIFO, SCHED_RR)

IPC (Inter-Process Communication)

• Pipes (anonymous and named/FIFO)
• Message queues
• Semaphores
• Shared memory segments
• Unix domain sockets

Storage & File Systems

• PCI Enumeration
• ATA/IDE Driver (PIO)
• VFS Layer
• Ext2 Read Support
• Ext2 Write Support
• File/Directory Creation (vfs_create, vfs_mkdir)
• AHCI/SATA driver (DMA support)
• NVMe driver
• FAT32 support
• ISO9660 (CD-ROM filesystem)
• File locking mechanisms
• Inotify/fsnotify (file change notifications)
• RAID support (software)

Network Stack

• Ethernet/ARP
• IPv4/ICMP
• UDP/DHCP
• DNS Resolver (A, PTR, CNAME + cache)
• Ping with DNS support
• TCP Implementation (full state machine)
• Simple HTTP server based on storage
• IPv6 support
• Network bridging/routing
• Firewall/packet filtering (iptables-like)
• Raw sockets
• Unix domain sockets
• TLS/SSL
• SSH server/client
• FTP/SFTP
• NFS client

Device Drivers

• VGA Console
• PS/2 Keyboard
• Azerty keyboard (with keymap abstraction)
• USB stack (XHCI/EHCI/UHCI)
• USB HID (keyboard/mouse)
• USB Mass Storage
• Audio driver (AC97/Intel HDA)
• Ethernet driver Intel I219-V
• WiFi support (with WPA2/WPA3)
• Graphics card drivers (Intel/AMD/NVIDIA)
• Serial port (COM1-4) advanced support
• Parallel port support

User Interface

• Interactive Shell with history
• Persistent history (/config/history)
• GUI + Mouse
• Window manager/compositor
• OpenGL support
• Framebuffer console (VESA/GOP)
• UTF-8 string and console
• Font rendering (TrueType/FreeType)
• Desktop environment
• Widget toolkit
• Multi-monitor support

User Space & Applications

• ELF Loader (32-bit executables)
• ELF 64-bit support
• Dynamic linking (shared libraries .so)
• Standard C library (libc)
• POSIX thread library (pthread)
• Math library (libm)
• Compression libraries (zlib, gzip)
• Core utilities (ls, cp, mv, rm, cat, grep, etc.)
• Text editor (vi/nano-like)
• Package manager
• GCC/Compiler toolchain port

Configuration & Scripts

• Scripting files (/config/startup.sh)
• Network configuration files (/config/network.conf)
• Persistent history (/config/history)
• Init system (systemd/OpenRC-like)
• Service management
• Environment variables
• User authentication (/etc/passwd, /etc/shadow)
• Permissions and ACL
• Cron/scheduled tasks

Security

• User/group management
• File permissions (chmod/chown)
• Access Control Lists (ACL)
• Sandboxing/containers
• Secure boot support
• ASLR (Address Space Layout Randomization)
• DEP/NX bit enforcement
• Encrypted filesystems
• SELinux/AppArmor-like MAC

Development & Debugging

• GDB stub (remote debugging)
• Kernel debugger (kdb)
• System call tracing (strace-like)
• Performance profiling tools
• Memory leak detection
• Code coverage tools

Advanced Features

• Virtualization support (KVM guest)
• Containers/namespaces
• Control groups (cgroups)
• Hibernation support
• Laptop features (battery, backlight)
• Bluetooth stack
• TPM support
• Hot-plug devices support

Documentation & Testing

• API documentation
• User manual
• Automated testing suite
• Continuous integration
• Benchmarking suite

Project Structure

src/
├── arch/x86/          # x86-specific code (boot, GDT, IDT, TSS, usermode)
├── config/            # Kernel configuration
├── kernel/            # Kernel core (main, console, keyboard, syscalls, elf)
├── mm/                # Memory Management (PMM, heap, VMM)
├── drivers/           # Hardware drivers
│   ├── ata.c/h        # ATA/IDE disk driver
│   ├── pci.c/h        # PCI bus driver
│   └── net/           # Network drivers (PCnet)
├── fs/                # Filesystems
│   ├── vfs.c/h        # Virtual File System layer
│   └── ext2.c/h       # Ext2 filesystem driver
├── net/               # Network stack
│   ├── core/          # Network infrastructure
│   ├── l2/            # Layer 2 (Ethernet, ARP)
│   ├── l3/            # Layer 3 (IPv4, ICMP, Routing)
│   └── l4/            # Layer 4 (UDP, TCP, DHCP, DNS)
├── shell/             # Command interpreter
│   ├── shell.c/h      # Shell core (readline, history, parsing)
│   └── commands.c/h   # Built-in commands (help, ping, exec, etc.)
├── userland/          # User space programs (server, hello, test)
└── include/           # Shared headers (Multiboot, linker script, ELF)

Architecture Overview

┌─────────────────────────────────────────────────────────┐
│              User Space (Ring 3)                        │
│         ELF Programs  │  Userland libc                  │
├─────────────────────────────────────────────────────────┤
│                  System Calls (int 0x80)                │
├─────────────────────────────────────────────────────────┤
│              Kernel Space (Ring 0)                      │
├─────────────────────────────────────────────────────────┤
│     VFS API              │         Network API          │
│  (open, read, readdir)   │    (send, recv, socket)      │
├──────────────────────────┼──────────────────────────────┤
│   Ext2   │  (Future FS)  │  TCP/UDP  │ ICMP │ DHCP/DNS  │
├──────────────────────────┼──────────────────────────────┤
│      ATA Driver          │     IPv4  │  ARP  │ Ethernet │
├──────────────────────────┼──────────────────────────────┤
│      IDE Controller      │       PCnet Driver           │
├──────────────────────────┴──────────────────────────────┤
│                    PCI Bus                              │
├─────────────────────────────────────────────────────────┤
│              Hardware (x86)                             │
└─────────────────────────────────────────────────────────┘

Building

Prerequisites

• Cross-compiler: i686-elf-gcc (in ~/opt/cross/bin/)
• Assembler: nasm
• Emulator: qemu-system-i386
• Disk utilities: e2fsprogs (for creating Ext2 disk images)

Compilation

# Build the kernel
make

# Clean build artifacts
make clean

# Full rebuild
make clean && make

Creating a Disk Image

# Create a 32MB Ext2 disk image
dd if=/dev/zero of=disk.img bs=1M count=32
mkfs.ext2 disk.img

# Add files to the disk (using debugfs on macOS)
echo "Hello from ALOS!" > /tmp/hello.txt
debugfs -w disk.img -R "write /tmp/hello.txt hello.txt"

# Verify contents
debugfs disk.img -R "ls"

Running

make          # Compile le kernel
make iso      # Crée l'ISO bootable (télécharge Limine si nécessaire)
make run      # Lance QEMU avec l'ISO
make clean    # Nettoie les fichiers compilés
make distclean # Nettoie tout, y compris Limine

QEMU Configuration

Storage

• Primary Master IDE disk: disk.img (Ext2 formatted)

License

This project is intended for educational purposes.

Contributing

Contributions are welcome!