DEV300: DEV300: A Tiny CPU and OS in C#A Tiny CPU and OS in C#

Scott HanselmanScott HanselmanTechnology Evangelist/ArchitectTechnology Evangelist/ArchitectCorillian CorporationCorillian Corporationscott@corillian.comscott@corillian.com

Tiny CPU and OSTiny CPU and OSDesign GoalsDesign Goals

Creation of an Abstract MachineCreation of an Abstract Machine Simulate Running and Scheduling of Simulate Running and Scheduling of

ProcessesProcesses Provide Paging, Virtual Memory, Provide Paging, Virtual Memory,

Memory ProtectionMemory Protection Each Process scheduled independentlyEach Process scheduled independently Inter-process CommunicationInter-process Communication

Tiny CPU and OSTiny CPU and OSDisclaimerDisclaimer

GoalsGoals Meant to teach C# and exercise librariesMeant to teach C# and exercise libraries Meant to teach basic OS/CPU conceptsMeant to teach basic OS/CPU concepts Meant to simulate OS behaviorsMeant to simulate OS behaviors

NOT GOALSNOT GOALS Not meant to get any work doneNot meant to get any work done Not meant as a “perfect” simulationNot meant as a “perfect” simulation

CPU and OSCPU and OS

The CPU is a 32-bit machine The CPU is a 32-bit machine all addresses and registers are 32-bits all addresses and registers are 32-bits

CPUCPU 10 registers 32-bits wide10 registers 32-bits wide IP – Instruction PointerIP – Instruction Pointer SP – Stack PointerSP – Stack Pointer

OSOS 32 basic OpCodes32 basic OpCodes Each OpCode takes 1 clock cycleEach OpCode takes 1 clock cycle

Basic DesignBasic DesignObject mapping to actual OS/CPU piecesObject mapping to actual OS/CPU pieces

ProgramProgram

InstructionInstructionCollectionCollection

InstructionInstruction

InstructionInstruction

InstructionInstruction

InstructionInstructionProcessProcesscreateProcess()createProcess()

6 r4, $0 ;move 0 into r46 r4, $0 ;move 0 into r4

new Instruction(raw)new Instruction(raw)

Program File on DiskProgram File on Disk

Process in the OSProcess in the OS

Basic DesignBasic DesignObject mapping to actual OS/CPU piecesObject mapping to actual OS/CPU pieces

CPUCPU

Operating System (at run-time)Operating System (at run-time)

Scheduler LoopScheduler Loop

Running Processes CollectionRunning Processes Collection

ProcessProcess ProcessProcess ProcessProcess ProcessProcess

Each Process scheduled independentlyEach Process scheduled independently Poorly behaved processes are terminatedPoorly behaved processes are terminated Memory is protected unless sharedMemory is protected unless shared

CPU and OSCPU and OS

Executed like this from command-line:Executed like this from command-line: C:> OS 2048 prog1.txt prog2.txtC:> OS 2048 prog1.txt prog2.txt

Many Configuration optionsMany Configuration options<configuration><configuration>

<appSettings><appSettings><add key="PhysicalMemory" <add key="PhysicalMemory"

value="128" />value="128" /><add key="ProcessMemory" value="384" /><add key="ProcessMemory" value="384" /><add key="DumpPhysicalMemory" <add key="DumpPhysicalMemory"

value="true" />value="true" /><add key="DumpInstruction" value="true" <add key="DumpInstruction" value="true"

/>/><add key="DumpRegisters" <add key="DumpRegisters"

value="true" />value="true" /><add key="MemoryPageSize" value="16" /><add key="MemoryPageSize" value="16" /><add key="StackSize" value="16" /><add key="StackSize" value="16" /><add key="DataSize" value="16" /><add key="DataSize" value="16" />

</appSettings></appSettings></configuration></configuration>

Instruction Set ExampleInstruction Set ExampleOpcodeOpcode ## FormatFormat

Sleep 25 Sleep r1; Sleep the # of clock cycles as indicated in r1. Another process or the idle process must be scheduled at this point. If the time to sleep is 0, the process sleeps infinitely.

SetPriority 26 SetPriority r1; Set the priority of the current process to the value in register r1; See priorities discussion in Operating system design

Exit 27 Exit. This opcode is executed by a process to exit and be unloaded. Another process or the idle process must now be scheduled.

FreeMemory 28 FreeMemory r1; Free the memory allocated whose address is in r1.

MapSharedMem

29 MapSharedMem r1, r2; Map the shared memory region identified by r1 and return the start address in r2.

SignalEvent 30 SignalEvent r1; Signal the event indicated by the value in register r1.

WaitEvent 31 WaitEvent r1; Wait for the event in register r1 to be triggered. This results in context-switches happening.

Input 32 Input r1; read the next 32-bit value into register r1.

MemoryClear 33 MemoryClear r1, r2; set the bytes starting at address r1 of length r2 bytes to zero.

Example Idle LoopExample Idle Loop

66 r4, $0r4, $0 ;move 0 into r4;move 0 into r4

2626 r4r4 ;lower priority TO 0;lower priority TO 0

66 r1, $20 r1, $20 ;move 20 into r1;move 20 into r1

1111 r1r1 ;print the number 20;print the number 20

66 r2, $-19r2, $-19 ;back up the ip 19;back up the ip 19

1313 r2r2 ;loop (jump back 19);loop (jump back 19)

Like a “Tiny Assembly Language”Like a “Tiny Assembly Language” Instructions are fetched from memory Instructions are fetched from memory

by the CPU and routed to the OS object by the CPU and routed to the OS object No compilation necessary – possible future enhancement?No compilation necessary – possible future enhancement?

Demo: Basic ProgramsDemo: Basic Programs

Manipulating RegistersManipulating Registers Moving Memory, using the StackMoving Memory, using the Stack Small FunctionsSmall Functions Inter-process CommunicationInter-process Communication

Tiny OS MemoryTiny OS Memory ““Physical Memory” just array of bytesPhysical Memory” just array of bytes

internal static byte[] physicalMemory;internal static byte[] physicalMemory;

Virtual Memory may be much larger!Virtual Memory may be much larger! But each Process has it’s own “view”But each Process has it’s own “view”

Virtual Memory hidden in code via Virtual Memory hidden in code via [] Operator Overloading[] Operator Overloading

// Copy the code in one byte at a time// Copy the code in one byte at a timeProcess pProcess p == new new Process(++idPool, memSize);Process(++idPool, memSize);uint uint index = 0;index = 0;foreach foreach ((byte byte bb in in processCodeprocessCode))

memoryMgr[p.PCB.pid, index++] = b;memoryMgr[p.PCB.pid, index++] = b;

Tiny OS MemoryTiny OS Memory

1231230

2551 255

4564562

45645600

00100111

31031022

PhysicalPhysicalVirtualVirtualProcessProcess

25525533

05205244

12312355

056056……

635

456

412

324

123

644

543

654

Of course, the OS Of course, the OS can can address address more more memory than it memory than it has physically. has physically. So, you might So, you might have 256 bytes of have 256 bytes of memory, but can memory, but can address 1024!address 1024!

All memory All memory operations such operations such as paging and as paging and swapping are swapping are hidden from the hidden from the Process.Process.

Tiny OS MemoryTiny OS Memory

1231230

2551 255

4564562

45645600

00100111

31031022

PhysicalPhysicalVirtualVirtualProcessProcess

25525533

05205244

12312355

056056……

635

456

412

324

123

644

543

654

<xml/><xml/>pages pages on diskon disk

Tiny OS Memory Tiny OS Memory with small physical memory and pagingwith small physical memory and paging

1231230

2551 255

4564562

45645600

00100111

31031022

PhysicalPhysicalVirtualVirtualProcessProcess

25525533

05205244

12312355

056056……

635

456

412

324

123

644

543

654

For the Process, For the Process, everything stays everything stays the same, except the same, except now parts of now parts of virtual memory virtual memory map to disk!map to disk!

Tiny OS Memory Tiny OS Memory memory becomes fragmentedmemory becomes fragmented

Major Elements (1 of 2)Major Elements (1 of 2) Typed CollectionsTyped Collections

Generated by ToolGenerated by Tool

unsafe unsafe codecode Like “inline C”Like “inline C”

Delegates Delegates Object-Oriented Function PointersObject-Oriented Function Pointers

Object SerializationObject Serialization Memory Pages serialized to diskMemory Pages serialized to disk

Major Elements (2 of 2)Major Elements (2 of 2) Custom ExceptionsCustom Exceptions

Specific Derived Classes for each Specific Derived Classes for each purposepurpose

Regular ExpressionsRegular Expressions Simplifies Program ParsingSimplifies Program Parsing

IComparableIComparable Custom Sorting in CollectionsCustom Sorting in Collections

Demo: Changing the OSDemo: Changing the OS

Changing Configuration OptionsChanging Configuration Options Modifying Virtual Memory Swapping!Modifying Virtual Memory Swapping! Adjusting Memory Page SizeAdjusting Memory Page Size Analyzing Statistics and ProfilingAnalyzing Statistics and Profiling

SummarySummaryTiny CPU and OSTiny CPU and OS

Learn C# and .NETLearn C# and .NET Find a problem and solve it!Find a problem and solve it! Make use of the .NET Framework Classes!Make use of the .NET Framework Classes! Imagine how you’d do it in other Imagine how you’d do it in other

languages!languages!

What .NET can do will surprise you!What .NET can do will surprise you!

Additional ResourcesAdditional Resources

Get the Deep Technical Drill Down Get the Deep Technical Drill Down DEV366: .NET Framework Under the HoodDEV366: .NET Framework Under the Hood

Learn how to Architect an applicationLearn how to Architect an application DEV310: Architecting Enterprise DEV310: Architecting Enterprise

Applications with Applications with Visual Studio .NETVisual Studio .NET

DEV358: Architecting N-Tier .NET DEV358: Architecting N-Tier .NET ApplicationsApplications

DEV402: Design Choices for Implementing DEV402: Design Choices for Implementing Distributed Applications in .NETDistributed Applications in .NET

http://msdn.microsoft.comhttp://msdn.microsoft.com

© 2002 Microsoft Corporation. All rights reserved.© 2002 Microsoft Corporation. All rights reserved.This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.