UCAS-OS

Part 6 : File System

Features:

• Implement a simple file system
  • Disk and File system metadata management
  • Hierarchical directory structure
  • Use the SD card as the disk for your file system
  • Design and implement mkfs and statfs
  • Design and implement directory operations
  • Design and implement file operations
• Support common file system operations and unix-like commands:
  • FILE SYSTEM OPERATIONS :
    • mkfs : create a file system
    • statfs : print the information related to the file system including : size of the file system, number of inodes, start address of inodes, etc.
  • DIRECTORY OPERATIONS :
    • cd [directory name] or cd ./[directory name] or cd ./[directory name]/[directory name] : enter a directory
    • mkdir [directory name] or mkdir ./[directory name] : create a directory
    • rmdir [directory name] or rmdir ./[directory name] : delete a directory
    • ls : print the directory entries in the current directory
  • FILE OPERATIONS :
    • touch [file name] : create a file
    • cat [file name] : print the content of the file in shell
  • FILE FUNCTIONS :
    • int fopen(char *name, uint32_t mode)
    • int fwrite(int fd, char *buffer, int length)
    • int fread(int fd, char *buffer, int length)
    • void fclose(int fd)
  • ADDITIONAL OPERATIONS :
    • find [path] [name] : find out whether the file exists in the directory
    • rename [old name] [new name] : rename a file or directory
    • ln [src path] [new path] : create a link
    • ln -s [src path] [new path] : create a symble link
    • pwd
    • dump
    • du
    • df
    • diff [file name] [file name]
    • wc [file name]
    • rm [file name]
    • cp [file name] [file name]
    • mv [file name] [file name]
    • chmod [file name]
    • man [command name]
• Design file system structure:
  • Superblock : Metadata to describe the structure of the file system
  • Inodes : Metadata to describe file/directory
  • File descriptor table : Keeping information of opening files
  • Directories : A special file containing list of files and directories
  • Block bitmap : Allocation bitmap of all the blocks of the whole file system
  • Inode bitmap ; Allocation bitmap of the inodes of all the inodes of the whole file system
  • Inode table : Table of all the inodes

Disk Layout:

/*
* SD card file system for OS seminar
* This filesystem looks like this:
* FS size : 1GB
* 1 Block : 4KB, total Blocks : 256K
* 1 Inode : 128B
* Inode Bitmap size : 8K / 8 * 1B= 1KB
* Block Bitmap size : 256K / 8 * 1B= 32KB
* --------------------------------------------------------------------------------
* | Superblock   | Block Bitmap  | Inode Bitmap  | Inode Table    |  Blocks    |
* | 1 Block 4KB  | 8 Blocks 32KB | 1 Block  4KB  | 256 Blocks 1MB |  Others    |
* --------------------------------------------------------------------------------
*/

Features Test on Hardware:

Part 5 : Device Driver

Core Features

• Implement driver for network card

  • Setup MAC controller registers to allow network card initialization, and sending/receiving data without interrupt
  • Implement sending/receiving data with blocking
  • Implement network interrupt handler to serve receiving data

• Design Device Driver Structure

  • MAC controller : Include two parts of registers
    • MAC registers
    • DMA registers
  • Direct Memory Access
  • DMA descriptor
  • MAC interrupt handler

  

Part 4 : Virtual Memory

Core Features

• Implement virtual memory management for user process
  • Setup page table and TLB entries
  • Handle TLB exception to support TLB refill and invalid TLB exceptions
  • Handle page fault to support on demand paging assuming physical memory is enough
• Design virtual memory structure
  • Page tables
    • The data structure to store the mapping between virtual addresses and physical addresses
    • Each mapping is a page table entry
  • MMU and TLB
    • MMU stores a cache of recently used mappings from the page table, which is called translation lookaside buffer (TLB)
• Implement page fault handler with TLB miss and page fault, capable of isolating different processes
• Implement the page replacement when the required memory size exceeds the physical memory size. Choose an algorithm for the page replacement algorithm other than FIFO (my choice is clock algorithm)

Part 3 : Interactive OS and Process Management

Core Features

• Support interactive operation and basic process management
  • Implement a simple terminal and basic user commands
  • Implement four system calls: spawn, kill, wait, and exit
  • Implement three synchronization primitives
  • Implement inter-process communication mechanism: mailbox and use it to solve Producer-consumer problem
• Design Simple terminal
  • Screen
    • Use the provided printf to show input command
  • Shell
    • A user level process
    • Parse input command and invoke corresponding syscalls
    • Show the input command
• Implement synchronization primitives
  • condition variable
  • semaphores
  • barriers

Part 2 : A Simple Kernel

Core Features

• Write a simple kernel (non-preemptive)
  • Start a set of user processes and kernel threads
  • Perform context switches between processes and threads
  • Provide non-preemptive kernel support with context switch
  • Support basic mutex to allow BLOCK state of processes/threads
• Write a simple kernel (preemptive)
  • Provide preemptive kernel support with clock interrupt handler and priority based scheduling
  • Support system calls

Part 1 : Bootloader

Core Features

• Write a bootloader to start a simple kernel based on Openloongson SoC board
  • BIOS
    • Basic Input/Output System
    • Firmware used to perform hardware initialization after power-on
    • Load bootloader
  • Bootblock
    • Loaded by BIOS
    • Hard disk
  • Bootloader
    • A small program to enable operating system
    • Load the kernel
    • Switch control to the kernel