嵌入式作業(yè)系統(tǒng)實作

Implementationof

EmbeddedOperatingSystems

Introduction薛智文cwhsueh@.tw.tw/~cwhsueh/*/641OutlineIntroductiontoEmbeddedSystemIntroductiontoEmbeddedOperatingSystemCaseStudiesSoCKernel*/642PrefaceWindow2000,30Mlines.NetscapeCommunicator5,17Mlines.A圍棋program,0.01Mlines.ASOHOrouter,0.6Mlines.WhatisEmbedded(Linux/system)?Linuximagefilesdirectorieslinesbytes2.6.41150K134009605.6M167M2.4.251177K110006705M149M2.2.26507K51002802.5M75MThreadX129K158129K1.5MuC/OS-II55K1315.5K0.4MTinix’0.5K11200.5K*/643EmbeddedOStrends2001-2002,

sortedby2001*/644EmbeddedOStrends2001-2002,sortedby2002*/645電子書包發(fā)展硬體電子書包作業(yè)系統(tǒng)(OS/UI/CM)教學(xué)/同儕群體應(yīng)用軟體開發(fā)工具系統(tǒng)軟體開發(fā)工具(SDK)相容性測試軟體工具(TCK)ICEDDK開發(fā)工具電子書包平臺結(jié)構(gòu)教師教學(xué)應(yīng)用軟體電子書包教學(xué)應(yīng)用平臺電子書包教學(xué)數(shù)位內(nèi)容電子書包數(shù)位內(nèi)容開發(fā)工具同儕群體應(yīng)用軟體數(shù)位學(xué)習(xí)輔具數(shù)位學(xué)習(xí)平臺閱讀程式SCORMHTMLXML數(shù)位學(xué)習(xí)輔具數(shù)位學(xué)習(xí)平臺PhysicalSerialUSB1394IrDABluetooth802.11ProtocolSyncML電子書包與數(shù)位學(xué)習(xí)輔具分工架構(gòu)圖org07c00h;telltheassemblertoloadonto7c00,0100hforDOS

movax,csmovds,axmoves,axcallDispStr;callstringdisplayprocedure

jmp$;infiniteloopDispStr:movax,BootMessagemovbp,ax;ES:BP=stringaddress

movcx,16;CX=stringlength

movax,01301h;AH=13,AL=01hmovbx,000ch;pagenumberis0(BH=0)blackbackgroundredcharacter;(BL=0Ch,

highlight)movdl,0int10h;the10hsoftwareinterrupt

retBootMessage:db"Hello,OSworld!"times510-($-$$)db0;filltherestofsector(512bytes)with0dw0xaa55;endofsectorTinix’

-“自己動手寫作業(yè)系統(tǒng),”于淵*/647ExampleRS485RS485EthernetEthernet*/648Introduction

UnixSVR4,SystemVRelease4,AT&T,nowownedbySantaCruzOperation,Inc.;4.4BSD,UCBerkeleyDigitalUnix,DECCompaqHPAIX,IBMHP-UX,HPSolaris,SunMicrosystems,StanfordUniversityLinux,1991LinusTorvaldson80386Alpha,SPARC,680x0,PowerPC,IBM390,ARM,…AUnixkernelwithotherapplicationsavailableunderGNUGeneralPublicLicenseGNU’sNotUnixPOSIX,PortableOSbasedonUnix*/649OutlineIntroductiontoEmbeddedSystemIntroductiontoEmbeddedOperatingSystemSoftwareEngineeringCaseStudiesSoCKernelPaperdiscussion*/6410WhatisanEmbeddedSystem?Asystemdesignedtoperformaspecificfunction,e.g.eBook,PDA,eWatch,…Acombinationofcomputerhardwareandsoftware,andperhapsadditionalmechanicalorotherparts.Embeddedvs.General-PurposeWhatisaspecificfunction?Istherealimitation?Cost,Robust,Low-power,Small,…UsingC+Assembly,Java?*/6411EmbeddedSystemExamplesComputerperipheralsKeyboard,Mouse,…InformationAppliancesSet-UpBoxes,WebTV,…MonitorsandSensorsFireAlarm,HeartbeatDetector,…ControllersinElectronicsRefrigerator,AirConditioner,…CommunicationDevicesHub,Router,……*/6412BusinessIssuesofESTime-to-marketfornewdevicesDesigntodelivery:inweeksSustainedpressuretoreducecostsManyproprietarychoicesyieldlow-marginsLifecyclemanagementNewproductsoverlappingeachotherPositioningnightmaresOpenplatformchoicesconsideredrisky?Resourcesexpendedon“recreatingthewheel…”notonproductdifferentiation.*/6413ESTechnologyIssuesNeedmorecomplextechnologyintegratedfornewservicesbroadband,wireless,real-time,low-power,…Multipleemergingstandardsneedtobedeployedsimultaneously.Productreleasedgloballyonthesameday!Tools,Tools,Tools,…ThirdpartysoftwareNoonecompanycandoitallanymoreSupportnightmaresLackofsourcesfromproprietarychoicesOpensourcessoundseductive…butrisky.*/6414Real-TimeSystemsvs.EmbeddedSystemsRTSESRTES.Radar.Calculator.ABS*/6415Real-TimeSystemsTimeValueHardRTSSoftRTSFirmRTSDeadline-Value*/6416Real-TimeSystems(RTS)FirmRTSSoftRTSHardRTSProprietaryOpenCentralizedDistributedEmbedded*/6417OutlineIntroductiontoEmbeddedSystemIntroductiontoEmbeddedOperatingSystemSoftwareEngineeringCaseStudiesSoCKernelPaperdiscussion*/6418Linux2.2AimstobecompliantwithIEEEPOSIXSourcecodesfromotherUnix-likekernelcanbecompiledandexecutedwithlittleefforts,evenwithoutpatches.IncludemodernOSfeatures,i.e.virtualmemory,virtualfilesystem,lightweightprocesses,signals,IPC,SMP,…WasnotveryinnovativeexceptGeneralPublicLicense(GPL).*/6419Linuxvs.OtherUnix-LikeKernelsLinuxkernelismonolithic.SameasmostotherUnixvariantswhileMach3.0,usesmicrokernel(taskmanagement+semaphore+timer),fromCMULinuxsupportsmodules.Traditionalkernelsarecompiledandlinkedstatically.Limitedkernelthreadscannotexecuteuserprograms,Nonstandardlightweightprocess,usingclone().Linuxisanonpreemptivekernel.OnlySolaris2.x,Mach3.0arefullypreemptive.Introducefixedpreemptionpointstocure.*/6420Linuxvs.OtherUnix-LikeKernels(cont.)Multiprocessorsupportafter2.2.filesystemandnetworkoperationstillremainsequential.FilesystemisstandardbutiseasytoportotherfilesystemthroughVFS.EXT2,EXT3(Journaling),ReiserFS(smallfiles)IBMAIX,JournalingFileSystemSGIIrix,XFSfilesystem,forbigvolume,guaranteedI/Orate,andjournaling.NoSTREAMSI/Osubsystem,fromSVR4,popularinotherUnixkernelsforwritingdevicedrivers,terminaldrivers,andnetworkprotocols.rejectedbyLinusbecauseofperformance.*/6421WhyLinux?Free,nocharge.Free,fullycustomizableinallcomponents.Runsonlow-endcheapHWplatforms.EmbeddedLinuxisveryhot.Powerful.opensourcesoastofullyutilizeHW.Highstandardforsourcecodequality.lowfailurerateandmaintenancetime.Kernelcanbeverysmallandcompact.HighlycompatiblewithotherOSes.Filesystem,networking,codeexecuteddirectly.Wellsupported.*/6422HardwareDependencyLinuxmaintainsaneatdistinctionbetweenhardware-dependentandhardware-independentsourcecode.alphaHewlett-Packard'sAlphaworkstationsarmARMprocessor-basedcomputersandembeddeddevicescris"CodeReducedInstructionSet"CPUsusedbyAxisinitsthin-servers,suchaswebcamerasordevelopmentboardsi386IBM-compatiblepersonalcomputersbasedon80x86microprocessorsia64WorkstationsbasedonIntel64-bitItaniummicroprocessorm68kPersonalcomputersbasedonMotorolaMC680x0microprocessorsmipsWorkstationsbasedonMIPSmicroprocessorsmips64

Workstationsbasedon64-bitMIPSmicroprocessorsparisc

WorkstationsbasedonHewlettPackardHP9000PA-RISCmicroprocessorsppcWorkstationsbasedonMotorola-IBMPowerPCmicroprocessorss39032-bitIBMESA/390andzSeriesmainframess390x

IBM64-bitzSeriesserverssh

SuperHembeddedcomputersdevelopedjointlybyHitachiandSTMicroelectronicssparc

WorkstationsbasedonSunMicrosystemsSPARCmicroprocessorssparc64

WorkstationsbasedonSunMicrosystems64-bitUltraSPARCmicroprocessorsTaiwanCore*/6423PowerManagementHaltingintheidleprocessidleprocessexecuteshltonIntellow-powerconsumptionmodeSuspendingthesystempatchesforsuspendingtodiskAPM:AdvancePowerManagementlaptopstandardpowermanagementACPI:AdvancedConfigurationandPowerInterfacenewcomprehensivestandardfromIntel-MicrosoftPower-managementisessentialformobilesystems*/6424Linux2.6HighlightsNewschedulerNewarchitecturesandprocessortypeshavebeenadded–includingsupportforMMU-lesssystemsNewsetofdriversforaudioandmultimediahavebeenaddedOthers(kernelcoredumping,fastmutexsupport,animprovedI/Osubsysemetc.)*/64252.4vs.2.6Kernel2.4hadAGlobalrunqueue.AllCPUshadtowaitforotherCPUstofinishexecution.AnO(n)scheduler.In2.4,theschedulerusedtogothroughtheentire“globalrunqueue”todeterminethenexttasktoberun.ThiswasanO(n)algorithmwhere'n'isthenumberofprocesses.Thetimetakenwasproportionaltothenumberofactiveprocessesinthesystem.Thisleadtolargeperformancehitsduringheavyworkloads.*/6426DriverPortingtoLinux2.6QuickerkernelbuildsystemNewsetofmoduleutilitiesMakefilesfor2.4won’tworkin2.6.komoduleobjectinsteadofan.omodule_initandmodule_exitinsteadofinit_moduleandcleanup_moduleNewmoduleloadingutilityminimizetheoccurrenceofraceconditionsThemoduleusagecountmovetooutsideofmodulecode*/6427WorkqueueInterfaceUsedtoschedulekerneltasksEachworkqueuehasdedicatedworkerthreadsassociatedwithitandallthetasksfromtherunqueueruninthecontextoftheprocessDrivercanusethedefaultworkqueueprovidedbythekernel*/6428OtherNotableChangesFilesystemsIBM’sJFS(journalingfilesystem)andSGI’sXFShavebeenmergedinto2.6AudioNewLinuxaudioarchitectureALSA(AdvancedLinuxSoundArchitecture)replacesOSS(OpenSoundSystem)*/6429OtherNotableChangesPowermanagementSupportforACPI(AdvancedConfigurationandPowerInterface),forCPUscalingUndertestingNetworkingandIPSecTheIPSecfeatureusesthenewcryptoAPI,includingMD4,MD5,DES,etcSupportforthenewNFSv4UserinterfacelayerSupporttouchscreen,brailledevice,etc*/6430DownsizingWhy?1M500K300K100K46K16K5KHow?*/6431WhatisaReal-TimeSystem?Asystemenforcingtimingconstraints,e.g.Avionics,MissileControl,…Thecorrectnessofthesystemdependsnotonlyonthelogicalresultofthecomputation,butalsoonthetimeatwhichtheresultsareproduced.Real-Timevs.HighPerformanceWhatisatimingconstraint?Aconstraintoftimingrequirements,e.g.period,distance,deadline,readytime,…Functionalandtemporalcorrect.*/6432Whatisa

Real-TimeOperatingSystem?Anoperatingsystemenforcingtimingconstraints,Lynx,pSOS,VxWorks,eCOS,uCLinux,LynxOS,RTLinux,KURT,uC/OS-II,QNX,…*/6433SystemsIssuesInRTS,theOSandAPareverytightlycoupled,thantime-sharingsystems.sharedmemory,specialbuses(instruction,data,event,memory,control,invalidate,…).ARTOSmustresponsetointernalandexternaleventsdeterministically.Low-prioritytasksmaywaitforhigh-prioritytaskoreventsindefinitely.Systemarchitectureneedstoprovidehighcomputationalspeed,high-speedinterrupthandling,andhighI/Othroughput,+fault-tolerance.TORNADOII：

VxWorks*/6435TORNADOII：VxWorksEmbeddedDevelopmentToolsVxWorksRealTimeOperatingSystemWindMicrokernelSnapshootofHostDevelopmentTools*/6436TheNextGenerationofEmbeddedDevelopmentTools*/6437VxWorks*/6438WindMicrokernel*/6439EmbeddedInternet*/6440VirtualMemory*/6441Multiprocessing*/6442Graphics*/6443FileSystems*/6444Networking*/6445WindView*/6446Stethoscope*/6447Tipstobefamiliarwith

embeddedboardsBuyanewnotebookforeachofyourembeddedboard.Lotsofnotestobekept.Searchforon-lineandoff-linemanuals.Asksomeonewhounderstandstheboard.Callyourvendors.Theremaybenewsgroupstodiscussallkindsquestionsonyourvenders’homepage.Jointhem!!SearchonGoogle.*/6448WhyHardware?Asoftwareengineerwhowritesonlyapplicationsmayspendanentirecareerandlearnnothingabouthardware,BUT…Anembeddedsoftwareengineermustoften:understandthehardwareinordertowritecorrectsoftware,mustinstallthesoftwareonthehardware,mustfigureoutwhetheraproblemisasoftwarebugorhardwareerror,andreadhardwareschematicdiagramandsuggestcorrections.*/6449Overview(1/2)TheLinuxiscomposedoffourmajorsubsystems.UserApplicationO/SservicesLinuxKernelHardwarecontrollerUserApplicationO/SServicesLinuxKernelHardwareControllerDecomposionofLinuxsystem*/6450Overview(2/2)BeforeweportLinuxintotargetboard,wemustknowhardwaredifferencesbetweenhostandtarget.Usually,targetboardhaslimithardwaresupport.ItmighthavenoMMUorfloatingpoint.Targetboardmightsupportotherspecialhardwareormechanismthathosthasnot.*/6451LinuxKernelwithMMU(1/5)TheLinuxkerneluseMMUtomanagememoryusage.But,Samsung-S3C4doesnothaveMMUfunctiononit.WeneedtoconsidermanypartofLinuxKernelfortargetwithoutMMU.*/6452LinuxKernelwithMMU(2/5)ARMMMUfunctionsTranslatevirtualaddressintophysicaladdressControlmemoryaccesspermissionsDomaincontrolHardwarerequirementforMMUTLB(Translationlookasidebuffer)AccesscontrollogicTranslation-table-walkinglogic*/6453LinuxKernelwithMMU(3/5)Virtualmemorydoesmorethanjustmakeyourcomputer’smemorygofurther.Itprovides:LargeaddressspacesProtectionMemorymappingFairphysicalmemoryallocationSharedvirtualmemory*/6454LinuxKernelwithMMU(4/5)MemoryaccesscontrolSomememory,suchasthatcontainingexecutablecode,naturallyreadonlymemory.Theoperatingsystemshouldnotallowaprocesstowritedataoveritsexecutablecode.*/6455LinuxKernelwithMMU(5/5)LinuxpagetableNeedtotranslateavirtualaddressintoaphysicalone.Pageallocationandde-allocationProcessWhilewecreateaprocess,Linuxusesatechniquecalled“copyonwrite”.Thereadonlymemory,forexampletheexecutablecode,willalwaysbeshared.Whilethenewprocesswrites,thenLinuxwouldallocateanewpageforwriting.Processesusedynamiclinkinglibrarytosharememory.*/6456LinuxKernelwithoutMMU(1/5)LinuxkernelbasedonMMU.WemustchangetheLinuxkerneltosupporttargetdevicesinwhichhasnoMMU.VirtualmemoryThetargethasnoMMUcannotusevirtualmemorytoallocatememory.Thefunctionthatallocateandde-allocatevirtualmemoryaremodifiedintophysicalmemoryallocationandde-allocationfunction.*/6457LinuxKernelwithoutMMU(2/5)MemoryaccesscontrolThetargethasnoMMUcannotcontrolmemoryaccesspermissionsanddomain.AlloftheMMUcontrol,andmemoryaccesscontrolfunctionsaremaskedtosupportflatmemory.Flatmemorymodeltreatstheentirememoryonyourcomputerthesame,withoutartificialboundariesorspecialexclusions.*/6458Pageallocationandde-allocationBecauseofnoMMU,virtualmemorycannotbeused.Allimageshavetobeloadedtomemory.ProcessWithoutMMU,processescannotmapimagefromfiledirectlywithELForA.OUTformat.WeconvertELFintoFLATbyusingapplicationelf2flat.LinuxKernelwithoutMMU(3/5)*/6459LinuxKernelwithoutMMU(4/5)vLinuxmemorymapvLinuxusesverysimplememorymaptosupporttargetwithoutMMU.Pagetableentryisnotusedbutreservedforotherplatform.Programsareloadedintofreememoryareawhenexecute.*/6460LinuxKernelwithoutMMU(5/5)ExceptionHandlerPageTableEn