README

## SBUnix : CSE 506 Project

Professor: [Mike Ferdman](http://compas.cs.stonybrook.edu/~mferdman/)

Course webpage: [Operating systems](https://compas.cs.stonybrook.edu/courses/cse506-operating-systems-fall-17/)

### Project Description

x86_64 Preemptive multitasking operating system with following functionalities:

Markup :  * Memory Subsystem (page descriptors, free list, page tables, kmalloc)
          * Process Subsystem (kernel threads, context switch)
          * User-level Subsystem (VMAs/vm_map_entrys, switch to ring 3, page faults)
          * I/O subsystem (syscalls, terminals, VFS, tarfs file access)
          * A Shell
            * Support changing current directory (cd /path)
            * Execute binaries interactively
            * Execute scripts (files that start with #!sbush)
            * Set and use PATH and PS1 variables
            * Launch background processes (ls &)

* The provided Makefile:
  1) builds a kernel
  2) copies it into rootfs/boot/kernel/kernel
  3) creates an ISO CD image with the rootfs/ contents

* To boot the system in QEMU, run:
qemu-system-x86_64 -curses -drive id=boot,format=raw,file=$USER.img,if=none -drive id=data,format=raw,file=$USER-data.img,if=none -device ahci,id=ahci -device ide-drive,drive=boot,bus=ahci.0 -device ide-drive,drive=data,bus=ahci.1 -gdb tcp::9999

Explanation of parameters:
  -curses         use a text console (omit this to use default SDL/VNC console)
  -drive ...      connect a CD-ROM or hard drive with corresponding image
  -device ...     configure an AHCI controller for the boot and data disks
  -gdb tcp::9999  listen for "remote" debugging connections on port NNNN
  -S              wait for GDB to connect at startup
  -no-reboot      prevent reboot when OS crashes

* When using the -curses mode, switch to the qemu> console with ESC-2.

* To connect a remote debugger to the running qemu VM, from a different window:
gdb ./kernel

At the (gdb) prompt, connect with:
target remote localhost:9999