Download Polygonal Broadcast, Secret Maturity and the Firing Sensors

Toward a Self-Stabilized
Operating System
Shlomi Dolev, BGU
Reuven Yagel, BGU-Rafael
Talk Outline
• Operating Systems & Self Stabilization
• OS Research
• …..
Operating Systems & Self
Stabilization
• Goal: Find the means of making the core(main)
components of an OS behave in a Self-Stabilized
manner.
• Self Stabilization
– Usually Distributed Computing Oriented
– Fair composition [Dolev]
• Operating Systems
– Top-down vs. Bottom-up view
Virtual Machine vs. Resource Manager [Tanenbaum]
OS Research
• Deprecated by industry & hackers
– # of courses in univ.
• Base abstraction for higher abstractions
(middleware, protocol stacks)
• Essential for system reliability.[kernel
projects]
• Operating System.Net (Ideas will move on
to distributed OSs – see sciam article, .Net Framework diagram
Top-down vs. Bottom-up
• Top-down
– Linux kernel: 2M source code lines
– Windows 2000: ~30M
– Shell
• Bottom-Up
– We know what we have!
– Will take some time to become full operational.
Research Directions
• Build on Linux
– Open, Modern, Documented, Unix tradition, Cool…
– But: “Hackered”, Monolithic
– Case study for OS components.
• Hardening
– Security of servers
• SS-Shell
– First try, difficult to prove.
• Watchdog
The Problem (or: What can go wrong?)
• Everything!
• Soft errors (Processor, Memory, Bus).
– Approximately 98% of RAM errors are soft
errors.
• Software Errors.
Watchdog
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a) Reset processor (+ ROM OS)
b) Reinstalling OS periodically
c) Warmboot
d) Full self-stabilization
Platform
• IA-32 Architecture
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CPU modes
Boot process
Memory map, ROM areas
Hardware Changes
• Watchdog handler
– ROM (Liskov’s article), Harvard Model
– Program Restart
OS Stabilizer Code
Definitions & Assumptions
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Initial Configuration
Stabilized Processor & Watchdog.
Processor will react to watchdog interrupt.
Stabilizer code is stable (ROM)
Proof Sketch
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Lemma 1
Lemma 2
Lemma 3
Theorem
Screen Shots