Inhaltszusammenfassung zur Seite Nr. 1
Tru64 UNIX
Kernel Debugging
Part Number: AA-RH99A-TE
July 1999
Product Version: Tru64UNIX Version 5.0or higher
Thismanualexplainshowtousetoolstodebugakernelandanalyzea
crashdumpoftheTru64UNIX(formerlyDIGITALUNIX)operating
system.Also,thismanualexplainshowtowriteextensionstothekernel
debuggingtools.
Compaq Computer Corporation
Houston, Texas
Inhaltszusammenfassung zur Seite Nr. 2
©1999CompaqComputerCorporation COMPAQandtheCompaqlogoRegisteredinU.S.PatentandTrademarkOffice. AlphaandTru64are trademarksofCompaqInformationTechnologiesGroup,L.PintheUnitedStatesandothercountries. MicrosoftandWindowsaretrademarksofMicrosoftCorporationintheUnitedStatesandothercountries. UNIXandTheOpenGrouparetrademarksofTheOpenGroup.Allotherproductnamesmentionedherein maybetrademarksoftheirrespectivecompanies. Confidentialcomputersoftware. ValidlicensefromCompaqrequiredforpossession,use,orcopyin
Inhaltszusammenfassung zur Seite Nr. 3
Contents About This Manual 1 Introduction to Kernel Debugging 1.1 LinkingaKernelImageforDebugging............................ 1–1 1.2 DebuggingKernelPrograms ........................................ 1–3 1.3 DebuggingtheRunningKernel..................................... 1–3 1.4 AnalyzingaCrashDumpFile ...................................... 1–5 2 Kernel Debugging Utilities 2.1 ThedbxDebugger .................................................... 2–2 2.1.1 InvokingthedbxDebuggerforKernelDebugging ...
Inhaltszusammenfassung zur Seite Nr. 4
2.2.3.9 DisassemblingInstructions ................................ 2–21 2.2.3.10 DisplayingRemoteExportedEntries .................... 2–21 2.2.3.11 DisplayingtheFileTable .................................. 2–21 2.2.3.12 DisplayingtheudbandtcbTables........................ 2–22 2.2.3.13 PerformingCommandsonLists .......................... 2–22 2.2.3.14 DisplayingthelockstatsStructures ...................... 2–24 2.2.3.15 DisplayinglockinfoStructures ............................ 2–25 2.2.3.16 Disp
Inhaltszusammenfassung zur Seite Nr. 5
3.2.7 CheckingArgumentsPassedtoanExtension ............... 3–7 3.2.8 CheckingtheFieldsinaStructure............................ 3–7 3.2.9 SettingthekdbxContext ....................................... 3–8 3.2.10 PassingCommandstothedbxDebugger..................... 3–9 3.2.11 DereferencingaPointer ......................................... 3–9 3.2.12 DisplayingtheErrorMessagesStoredinFields ............ 3–10 3.2.13 ConvertingaLongAddresstoaStringAddress ............ 3–10 3.2.14 FreeingMemory .......
Inhaltszusammenfassung zur Seite Nr. 6
A Output from the crashdc Command Index Examples 3–1 TemplateExtensionUsingLists.................................... 3–23 3–2 ExtensionThatUsesLinkedLists:callout.c ..................... 3–24 3–3 TemplateExtensionsUsingArrays ................................ 3–27 3–4 ExtensionThatUsesArrays:file.c................................. 3–28 3–5 ExtensionThatUsesGlobalSymbols:sum.c..................... 3–34 Figures 2–1 UsingaGatewaySystemDuringRemoteDebugging........... 2–38 Tables 2–1 ThedbxAddressMod
Inhaltszusammenfassung zur Seite Nr. 7
About This Manual Thismanualprovidesinformationonthetoolsusedtodebugakerneland analyzeacrashdumpfileoftheTru64™UNIX(formerlyDIGITALUNIX) operatingsystem. Italsoexplainshowtowriteextensionstothekernel debuggingtools. Youcanuseextensionstodisplaycustomizedinformation fromkerneldatastructuresoracrashdumpfile. Audience Thismanualisintendedforsystemprogrammerswhowriteprogramsthat usekerneldatastructuresandarebuiltintothekernel. Itisalsointended forsystemadministratorswhoareresponsibleformanagingtheop
Inhaltszusammenfassung zur Seite Nr. 8
Organization Thismanualconsistsoffourchaptersandoneappendix: Chapter1 Introduces the concepts of kernel debugging and crash dump analysis. Describes the tools used to debug kernels and Chapter2 analyze crash dump files. Chapter3 Describeshowtowritea kdbxdebuggerextension. This chapterassumesyouhavepurchasedandinstalledaTru64 UNIXSourceKitandsohaveaccesstosourcefiles. Chapter4 Providesbackgroundinformationusefulforandexamples of analyzing crashdump files. AppendixA Containsexampleoutputfromthe cr
Inhaltszusammenfassung zur Seite Nr. 9
G Manuals for general users S Manualsforsystemandnetworkadministrators P Manuals for programmers R Manualsforreferencepage users Somemanualsinthedocumentationhelpmeettheneedsofseveral audiences. Forexample,theinformationinsomesystemmanualsisalso usedbyprogrammers. Keepthisinmindwhensearchingforinformation onspecifictopics. TheDocumentationOverviewprovidesinformationonallofthemanualsin theTru64UNIXdocumentationset. Reader’s Comments Compaqwelcomesanycommentsandsuggestionsyouhaveonthisand otherTru
Inhaltszusammenfassung zur Seite Nr. 10
% $ ApercentsignrepresentstheCshellsystemprompt. Adollarsignrepresentsthesystempromptforthe Bourne,Korn,andPOSIXshells. # Anumbersignrepresentsthesuperuserprompt. % cat Boldfacetypeininteractiveexamplesindicates typeduserinput. file Italic(slanted)typeindicatesvariablevalues, placeholders,andfunctionargumentnames. [|] {|} Insyntaxdefinitions,bracketsindicateitemsthat areoptionalandbracesindicateitemsthatare required. Verticalbarsseparatingitemsinside bracketsorbracesindicatethatyouchooseoneitem
Inhaltszusammenfassung zur Seite Nr. 11
1 Introduction to Kernel Debugging Kerneldebuggingisatasknormallyperformedbysystemsengineerswriting kernelprograms. Akernelprogramisonethatisbuiltaspartofthekernel andthatreferenceskerneldatastructures. Systemadministratorsmight alsodebugthekernelinthefollowingsituations: • Aprocessishungorstopsrunningunexpectedly • Theneedarisestoexamine,andpossiblymodify,kernelparameters • Thesystemitselfhangs,panics,orcrashes Thismanualdescribeshowtodebugkernelprogramsandthekernel.Italso includesinformationab
Inhaltszusammenfassung zur Seite Nr. 12
textfilethatdescribesthehardwareandsoftwarethatwillbepresenton therunningsystem. Usingthisinformation,thebootstraplinkerlinksthe modulesthatareneededtosupportthishardwareandsoftware.Thelinker buildsthekerneldirectlyintomemory. Youcannotdirectlydebugabootstrap-linkedkernelbecauseyoumustsupply thenameofanimagetothekerneldebuggingtools.Withouttheimage,the toolshavenoaccesstosymbolnames,variablenames,andsoon.Therefore, thefirststepinanykerneldebuggingeffortistodeterminewhetheryour kernelwaslinkedatb
Inhaltszusammenfassung zur Seite Nr. 13
1.2 Debugging Kernel Programs Kernelprogramscanbedifficulttodebugbecauseyounormallycannot controlkernelexecution. Tomakedebuggingkernelprogramsmore convenient,thesystemprovidesthe kdebugdebugger. The kdebug debuggeriscodethatresidesinsidethekernelandallowsyoutousethedbx debuggertocontrolexecutionofarunningkernelinthesamemanneras youcontrolexecutionofauserspaceprogram. Todebugakernelprogram inthismanner,followthesesteps: 1. Buildyourkernelprogramintothekernelonatestsystem. 2. Setupthe kdebugdebug
Inhaltszusammenfassung zur Seite Nr. 14
# dbx -k /vmunix /dev/mem Thiscommandinvokes dbxwiththekerneldebuggingflag, −k,which mapskerneladdressestomakekerneldebuggingeasier.The/vmunixand /dev/memparameterscausethedebuggertooperateontherunningkernel. Onceinthedbxenvironment,youusedbxcommandstodisplayprocessIDs andtraceexecutionofprocesses.Youcanperformthesametasksusingthe kdbxdebugger. Thefollowingexampleshowsthedbxcommandyouuseto displayprocessIDs: (dbx) kps PID COMM 00000 kernel idle 00001 init 00014 kloadsrv 00016 update . . . Ifyouw
Inhaltszusammenfassung zur Seite Nr. 15
1.4 Analyzing a Crash Dump File Ifyoursystemcrashes,youcanoftenfindthecauseofthecrashbyusing dbxorkdbxtodebugoranalyzeacrashdumpfile. Theoperatingsystemcancrashbecauseoneofthefollowingoccurs: • Hardwareexception • Softwarepanic • Hungsystem Whenasystemhangs,itisoftennecessarytoforcethesystemtocreate dumpsthatyoucananalyzetodeterminewhythesystemhung. The SystemAdministrationmanualdescribestheprocedureforforcinga crashdumpofahungsystem. • Resourceexhaustion Thesystemcrashesorhangsbecauseitcannotco
Inhaltszusammenfassung zur Seite Nr. 16
Atsystemreboottime,thecopyofcorememorysavedintheswappartitions iscopiedintoafile,calledacrashdumpfile. Youcananalyzethecrash dumpfiletodeterminewhatcausedthecrash.Bydefault,thecrashdumpis apartial(ratherthanfull)dumpandisincompressedform. Forcomplete informationaboutmanagingcrashdumpsandcrashdumpfiles,including howtochangedefaultsettings,seetheSystemAdministrationmanual.For examplesofanalyzingcrashdumpfiles,seeChapter4. 1–6 Introduction to Kernel Debugging
Inhaltszusammenfassung zur Seite Nr. 17
2 Kernel Debugging Utilities TheTru64UNIXsystemprovidesseveraltoolsyoucanusetodebugthe kernelandkernelprograms.TheLadebugdebugger(availableasanoption) isalsocapableofdebuggingthekernel. Thischapterdescribesthreedebuggersandautilityforanalyzingcrash dumps: • Thedbxdebugger,whichisdescribedforkerneldebugginginSection2.1. (Forgeneraldbxuserinformation,seetheProgrammer’sGuide.) Youcanusethedbxdebuggertodisplaythevaluesofkernelvariables andkernelstructures. However,youmustunderstandthestructures andb
Inhaltszusammenfassung zur Seite Nr. 18
______________________ Note _______________________ StartingwithTru64UNIXVersion5.0,allthepreviously mentionedtoolscanbeusedwithcompressed(vmzcore.n)and uncompressed(vmcore.n)crashdumpfiles. Olderversionsof thesetoolscanreadonly vmcore.nfiles. Ifyouareusingan olderversionofatool,usetheexpand_dumputilitytoproduce a vmcore.nfilefroma vmzcore.nfile. Formoreinformation aboutcompressedanduncompressedcrashdumpfiles,see expand_dump(8)andtheSystemAdministrationmanual. 2.1 The dbx Debugger The dbxdebugge
Inhaltszusammenfassung zur Seite Nr. 19
• Thesystemcorememoryimage Thesefilesmaybefilesfromarunningsystem,suchas /vmunixand /dev/mem,ordumpfiles,suchasvmunix.nandvmzcore.n(compressed) orvmcore.n(uncompressed). Bydefault,crashdumpfilesarecreatedin the/var/adm/crashdirectory(seetheSystemAdministrationmanual). ______________________ Note _______________________ Youmightneedtobethesuperuser(rootlogin)toexaminethe runningsystemorcrashdumpfilesproducedby savecore. Whetheryouneedtobethesuperuserdependsonthedirectory andfileprotectionsforthef
Inhaltszusammenfassung zur Seite Nr. 20
wanttoaddasymboltabletoyourcurrentdebuggingsessionratherthan endthesessionandstartanewone. Toaddasymboltabletoyourcurrent debuggingsession,followthesesteps: 1. Gotoawindowotherthantheoneinwhichthedebuggerisrunning, orputthedebuggerinthebackground,andrebuildthemodulesfor whichyouneedasymboltable. 2. Oncethemodulesbuildcorrectly,usetheostripcommandtostripa symboltableoutoftheresultingexecutablefile. Forexample,ifyour executablefileisnamed kernel_program,issueacommandsuchas thefollowingone: % /usr/
