FOS'24 Project

About The Project

The OS'24 Project is a comprehensive, hands-on implementation of an operating system designed to teach fundamental concepts like memory management, process scheduling, synchronization, and fault handling. It emphasizes modularity and provides students with a strong foundation in systems programming.

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Modules

Command Prompt

• A simple command-line interface to execute kernel-level commands.
• Supports commands like kernel_info, nclock, and others for testing and interaction.

System Calls

• Provides a bridge between user programs and the kernel, enabling secure execution of privileged operations.
• Validates user-provided pointers and ensures proper handling of invalid memory access.

Dynamic Allocator

• Kernel Heap: Implemented block and page-level allocators for dynamic memory allocation.
  • First-Fit Strategy: Used for both block and page allocations.
  • Supports functions like kmalloc, kfree.
• User Heap: Memory allocation for user programs with lazy allocation using system calls.

Memory Manager

• Page Allocator: Handles memory on a page-level granularity for efficient management.
• Shared Memory: Allows multiple processes to share memory regions for interprocess communication.

Fault Handler

• Page Fault Handling: Implements lazy allocation and replacement policies to manage memory faults efficiently.
• Nth Chance Clock Replacement: Optimized page replacement algorithm for balancing performance and memory utilization.

Synchronization and protection (Locks & Semaphores)

• Locks:
  • Implemented spinlocks for short critical sections with busy-waiting.
  • Designed sleeplocks to handle longer critical sections by blocking threads and avoiding CPU wastage.
  • Ensures safe access to shared kernel resources.
• Semaphores:
  • User-level semaphores to synchronize processes.
  • Operations include:
    • semWait: Decreases the semaphore value and blocks the process if the value is negative.
    • semSignal: Increases the semaphore value and unblocks waiting processes if needed.
  • Handles common issues like deadlocks and priority inversion with proper locking mechanisms.

CPU Scheduler

• Priority Round-Robin Scheduler:
  • Preemptive scheduling with multiple priority levels.
  • Prevents starvation by promoting processes based on their waiting time.
  • Supports commands like schedPRIRR for dynamic configuration.