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OS Motivation

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Computer Structures and Operating Systems 2023
Dr. Jens Lechtenbörger (License Information)

1. Introduction

1.1. Learning Objectives

  • Discuss role of OSs to control computers
    • Performance aspects
    • Ownership and control
  • Discuss role of licenses to control software

1.2. Performance Aspects

  • OS manages computer’s resources: CPU, memory, I/O
  • OS understanding helps to identify and reason about resource bottlenecks.
    • Improve design, analysis, and implementation of information systems.
    • E.g., why is my computer/application slow? How to improve that?
  • (Above are “traditional” topics for OS courses; this presentation takes a different direction.)

1.3. Whom do Computers Obey?

  • Recall (long-term) goal of CSOS


    Notebook” under CC0 1.0; from Pixabay

    • “Play and experiment with and control any computer, at any level of interest”
  • In CS part, you learned how to build a computer.
    • How does that feel?
  • In OS part, we investigate Operating Systems (OSs) to control computers.


    Search” under CC0 1.0; from Pixabay

    • OS controls what is executing when.
    • Who controls the OS?
    • Who controls the computer, then?

1.4. Computers


Server” under CC0 1.0; cropped from Pixabay


C64” under CC0 1.0; from Pixabay


Notebook” under CC0 1.0; from Pixabay


Router” under CC0 1.0; from Pixabay


Car” under CC0 1.0; from Pixabay


Doll” under CC0 1.0; from Pixabay


TV” under CC0 1.0; from Pixabay

Smart watch

Smart watch” under CC0 1.0; cropped from Pixabay

Fairphone 2

Fairphone 2” by Kaihsu Tai under CC BY-SA 4.0; cropped from Wikimedia Commons

1.5. Enlightenment

Enlightenment is man’s emergence from his self-incurred immaturity. (Immanuel Kant)

  • Your computer does whatever it is programmed to do.
  • You can succumb to somebody else’s programming.
  • Or emerge.

2. Choices and Consequences

2.1. Impact of Choices

  • Economic and ecological/social impact

    Man with megaphone

    Man with megaphone” under CC0 1.0; from Pixabay

    • What do you buy/use/create?
      • What do you advertise?
      • What do you impose on others?
  • Economic impact
    • Should be obvious
  • Ecological/social impact

    Magnet attracting people

    Figure” under CC0 1.0; from Pixabay

    • If you use some social/communication service, you increase its appeal and value
    • If you choose communication under surveillance capitalism, you impose surveillance on your family, friends, colleagues …

2.2. Rationale

  • If you want to own a device containing a computer (“smart” anything, recall slide on computers), you need to control its software.
    • (Including firmware and underlying hardware)
      • (Topic in its own right)

3. Software

3.1. Free Software

3.2. Free vs Open Source

  • Mostly philosophical distinction, sometimes religious
    • I prefer the term “free software” because it emphasizes freedom
    • If you do not want your academic works (theses, code, project results) to disappear, publish them under free licenses

3.3. GNU/Linux

  • Tux, the Linux mascot

    Tux, the Linux mascot” under CC0 1.0; from Wikimedia Commons

    • I encourage you to try out GNU/Linux, which is free software,
      • the major OS for cloud infrastructures,
      • the server OS in lots of project seminars.
    • Upcoming assignments are based on GNU/Linux
      • Several GNU/Linux distributions can be started as live systems from CD/DVD or USB stick without changing your current installation

3.4. Firmware

  • Firmware = Software that is embedded in hardware by vendor
    • Stored in (EP)ROM, flash
    • Initialization and control of hardware
      • E.g., BIOS, (U)EFI; but also video BIOS of graphics card, Management Engine of Intel CPUs
        • Typically shipped as binary blobs
        • NSA ANT catalog also contains firmware trojans (in wake of Snowden revelations)

3.4.1. CPU Rings

  • Outlook: CPUs have rings/privilege levels
    • Instruction set restricted depending on ring
      • Ring 3: User programs (I/O and memory access restricted)
      • Ring 2, 1: Usually unused (originally for system services and device drivers)
      • Ring 0: OS kernel (traditionally, ring 0 was most privileged)
      • More rings [Fra19]
        • Ring -1: Hypervisor (virtual machine monitor)
        • Ring -2: System management mode (SMM), unified extensible firmware interface (UEFI)
        • Ring -3: Management Engine

3.4.2. Free and Open Firmware

  • Articles by Jessie Frazelle
    • [Fra19]
      • “Between Ring -2 and Ring -3 there are at least two and a half other kernels in our stack that have many capabilities. Each of these kernels has its own networking stacks and web servers, which is unnecessary and potentially dangerous, especially if you do not want these rings reaching out over the network to update themselves. The code can also modify itself and persist across power cycles and reinstalls. There is very little visibility into what the code in these rings is actually doing, which is horrifying, considering these rings have the most privileges.”
    • [Fra20a]
      • “It’s an alarming problem that the code running with the most privilege has the least visibility and inspectability.”
    • [Fra20b]
      • “If you would like to help with the open source firmware movement, push back on your vendors and platforms you are using to make their firmware open source.”

4. Conclusions

4.1. Summary

  • Do you care?


License Information

This document is part of an Open Educational Resource (OER) course on Operating Systems. Source code and source files are available on GitLab under free licenses.

Except where otherwise noted, the work “OS Motivation”, © 2018-2023 Jens Lechtenbörger, is published under the Creative Commons license CC BY-SA 4.0.

No warranties are given. The license may not give you all of the permissions necessary for your intended use.

In particular, trademark rights are not licensed under this license. Thus, rights concerning third party logos (e.g., on the title slide) and other (trade-) marks (e.g., “Creative Commons” itself) remain with their respective holders.