Operating Systems

Course preview

What you will be able to do

• Explain what a system call costs and follow one from your code into the kernel and back
• Start, wait for, and clean up processes correctly — including the failure modes that leak them
• Write threaded code that shares data safely, and recognise a race condition before it ships
• Diagnose a deadlock from its four conditions instead of guessing
• Read a process's memory map and explain page faults, copy-on-write, and memory-mapped files
• Judge whether a privileged program is safe, and why setuid is where so many local exploits live

This is the full learning route. Lessons build on earlier work; required checkpoints are the points where the route asks you to demonstrate it.

1. 01

   Two worlds: kernel mode and user mode

   Lesson · 16 min

2. 02

   How a program asks the kernel for something

   Lesson · 18 min

   Builds on: Two worlds: kernel mode and user mode

3. 03

   Follow one system call all the way down

   Required checkpoint · 20 min

   Builds on: How a program asks the kernel for something

4. 04

   How a program starts another program

   Lesson · 20 min

   Builds on: Follow one system call all the way down

5. 05

   Zombies, orphans, and who cleans up

   Lesson · 16 min

   Builds on: How a program starts another program · Signals: the operating system interrupting you

6. 06

   Signals: the operating system interrupting you

   Lesson · 18 min

   Builds on: How a program starts another program

7. 07

   What a signal handler is allowed to do

   Lesson · 17 min

   Builds on: Signals: the operating system interrupting you

8. 08

   Threads and processes: what is actually shared

   Lesson · 16 min

   Builds on: How a program starts another program

9. 09

   Writing a threaded program

   Lesson · 18 min

   Builds on: Threads and processes: what is actually shared

10. 10

    Race conditions: when timing decides the answer

    Lesson · 19 min

    Builds on: Writing a threaded program

11. 11

    Mutual exclusion, and what it costs

    Lesson · 18 min

    Builds on: Race conditions: when timing decides the answer

12. 12

    Waiting properly: semaphores and condition variables

    Lesson · 19 min

    Builds on: Mutual exclusion, and what it costs

13. 13

    Build a producer-consumer queue that does not corrupt

    Required checkpoint · 22 min

    Builds on: Waiting properly: semaphores and condition variables

14. 14

    Deadlock: four conditions and how to break one

    Lesson · 18 min

    Builds on: Mutual exclusion, and what it costs · Waiting properly: semaphores and condition variables

15. 15

    How the scheduler decides who runs next

    Lesson · 18 min

    Builds on: Threads and processes: what is actually shared

16. 16

    What a process sees: the virtual address space

    Lesson · 18 min

    Builds on: How a program starts another program

17. 17

    From virtual to physical: page tables and the TLB

    Lesson · 19 min

    Builds on: What a process sees: the virtual address space

18. 18

    Paging on demand, and what a page fault really is

    Lesson · 18 min

    Builds on: From virtual to physical: page tables and the TLB

19. 19

    Copy-on-write and mapping files into memory

    Required checkpoint · 21 min

    Builds on: Paging on demand, and what a page fault really is

20. 20

    Privilege levels the hardware itself enforces

    Lesson · 15 min

    Builds on: Two worlds: kernel mode and user mode

21. 21

    Two ways to answer 'is this allowed?'

    Lesson · 17 min

    Builds on: Privilege levels the hardware itself enforces

22. 22

    setuid: the most dangerous bit on the filesystem

    Required checkpoint · 20 min

    Builds on: Two ways to answer 'is this allowed?'