北京大學操作系統(tǒng)實習jos-lab1實驗報告

1、操作系統(tǒng)JOS實習第一次報告張弛00848231zhangchitc@March182011Contents1PCBootstrap21.1GettingStartedwithx86assembly.................21.2Simulatingthex86..........................21.3ThePC’sPhysicalAddressSpace..................21.4TheRO

2、MBIOS............................22TheBootLoader32.1LoadingtheKernel..........................52.2Linkvs.LoadAddress........................63TheKernel83.1FmattedPrintingtotheConsole.................103.2TheStack........

3、........................161操作系統(tǒng)實習報告張弛008482312TheBootLoaderExercise3.TakealookatthelabtoolsguideespeciallythesectiononGDBcomms.Evenifyou’refamiliarwithGDBthisincludessomeesotericGDBcommsthatareusefulfOSwk.Setabreakpointa

4、taddress0x7c00whichiswherethebootsectwillbeloaded.Continueexecutionuntilthatbreakpoint.Tracethroughthecodeinbootboot.Susingthesourcecodethedisassemblyfileobjbootboot.asmtokeeptrackofwhereyouare.AlsousethexicomminGDBtodis

5、assemblesequencesofinstructionsinthebootloadercomparetheiginalbootloadersourcecodewithboththedisassemblyinobjbootboot.asmGDB.Traceintobootmain()inbootmain.cthenintoreadsect().Identifytheexactassemblyinstructionsthatcresp

6、ondtoeachofthestatementsinreadsect().Tracethroughtherestofreadsect()backoutintobootmain()identifythebeginendofthefloopthatreadstheremainingsectsofthekernelfromthedisk.Findoutwhatcodewillrunwhentheloopisfinishedsetabreakp

7、ointtherecontinuetothatbreakpoint.Thenstepthroughtheremainderofthebootloader.Beabletoanswerthefollowingquestions:?Atwhatpointdoestheprocessstartexecuting32bitcodeWhatexactlycausestheswitchfrom16to32bitmode?Whatisthelasti

8、nstructionofthebootloaderexecutedwhatisthefirstinstructionofthekernelitjustloaded?Whereisthefirstinstructionofthekernel?HowdoesthebootloaderdecidehowmanysectsitmustreadindertofetchtheentirekernelfromdiskWheredoesitfindth

9、isinfmation1.處理器從BIOS進入bootloader后，在bootboot.S中第48行到第51行代碼，bootloader將將將寄寄寄存存存器器器cr0的的的末末末位位位更更更改改改為為為1，，，使使使得得得處處處理理理器器器從從從實實實模模模式式式更更更改改改到到到保保保護護護模模模式式式。bootboot.S??44#SwitchfromrealtoprotectedmodeusingabootstrapGDT45#

10、segmenttranslationthatmakesvirtualaddresses46#identicaltotheirphysicaladdressessothatthe47#effectivememymapdoesnotchangeduringtheswitch.48lgdtgdtdesc49movl%cr0%eax50l$CR0_PE_ON%eax51movl%eax%cr0??2.bootloader執(zhí)執(zhí)執(zhí)行行行的的的最最最