计算机系统基础课件：汇编

1从程序到可执行代码

汇编（2）

5次课2ProcedureCall3BasicConceptTerminologyCallerCalleef()g()call-1h()call-2call-1Caller:fCallee:gcall-2Caller:gCallee:h4Procedure/FunctionImplementationInvokecalleeReturntocallerPassingdataRegistersLocalvariable5Procedure/FunctionImplementationInvokecallee:call(newinstructions)ReturntocallerPassingdataRegistersLocalvariable6InvokeCalleeInstructioncalllabel(direct)call*operand

(indirect)Behaviordescription(byhardware)SavereturnaddressinthestackJumptotheentry

ofcallee call=push+jmppushretaddrjmp

callee7Procedure/FunctionImplementation

Invokecallee:call(newinstructions)Returntocaller:ret(newinstructions)PassingdataRegistersLocalvariable8ReturntoCallerInstructionretBehaviordescription(byhardware)PopreturnaddressfromstackJumptoreturnaddress

incaller

ret=pop+jmppopretaddrjmp

retaddr9Procedure/FunctionImplementation

Invokecallee:call(newinstructions)

Returntocaller:ret(newinstructions)Passingdata:stack,registerRegistersLocalvariable10StackFrameStructureTheportionofstackallocatedforaprocedureAstackframeisdelimitedbyTheframepointer%ebpThestackpointer%espThestackpointercanmovewhentheprocedureisexecuting(dynamic)TheframepointerisstaticFrame%ebp%esp11StackFrameStructurecall:savereturnaddressinthestackret:popreturnaddressfromstackTheendofcaller’sstackframeCallee

Frame%ebp%espretaddrCaller

Frame12FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp1.callcallee13FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechainedretaddr%ebp%esp

1.callcalleecallee:2.push%ebp3.mov%esp,%ebpretaddr%ebp14FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp

1.callcalleecallee:

2.push%ebp3.mov%esp,%ebpretaddrold%ebp15FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp

1.callcalleecallee:

2.push%ebp3.mov%esp,%ebpretaddrold%ebp16FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp

1.callcalleecallee:2.push%ebp3.mov%esp,%ebp ...n-2.mov%ebp,%espn-1.pop%ebpn.retretaddrold%ebp17FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp

1.callcalleecallee:

2.push%ebp3.mov%esp,%ebp ...n-2.mov%ebp,%espn-1.pop%ebpn.retretaddrold%ebp18FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp

1.callcalleecallee:

2.push%ebp3.mov%esp,%ebp ...n-2.mov%ebp,%espn-1.pop%ebpn.retretaddrold%ebp19FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechained%ebp%esp

1.callcalleecallee:

2.push%ebp3.mov%esp,%ebp ...n-2.mov%ebp,%espn-1.pop%ebp

n.ret20FrameChainPointers(%ebp/%esp)onlydelimittopmost

frameFramesarechainedold%ebpold%ebpold%ebp%ebp%esp21MemoryLayoutUserstack

argumentN22PassingData:ArgumentspushargumentN%ebp%espCaller

Frameargument1......argumentN23PassingData:ArgumentspushargumentN...pushargument1%ebp%espCaller

Frameargument1......argumentN24PassingData:ArgumentspushargumentN...pushargument1callcallee%ebp%espretaddrCaller

FramepushargumentN...pushargument1callcalleepush%ebp%ebpargument1......argumentN25PassingData:Arguments%ebp%espretaddrCaller

FrameCallee

Frameold%ebpargument1......argumentN26PassingData:ArgumentspushargumentN...pushargument1callcalleepush%ebpmov%esp,%ebp...%ebp%esp/retaddrCaller

FrameCallee

Frameargument1......argumentN27PassingData:ArgumentsPushedbyCallerSavedincallerframeJustuponofreturnaddressFromNthto1st(fromrighttoleft)UsedbyCalleeRelativeto%ebpOffset:4+4*i+%ebpCallee

Frame%ebp%espretaddrCaller

Frame28PassingData:ReturnValueSpecificregistertokeepthereturnvalue%eaxisusedtopasstheresultofcalleetocaller29Procedure/FunctionImplementation

Invokecallee:call(newinstructions)

Returntocaller:ret(newinstructions)

Passingdata:stack,registerRegisters:callingconventionLocalvariable30CallingConventionRegistersactasasingleresourcesharedbyalloftheproceduresOnly1procedurecanbeactivePartitionregistersbetweencallerandcalleeSaller-saveregisterCallee-saveregisterOnlyconsidertheregistersusedbytheprocedure31CallingConventionCaller-saveregisters%eax,%edx,%ecxSavedbycallerCalleecanusetheseregistersfreelyThecontentsintheseregistersmaybechangedafterreturnCallermustrestorethemifittriestousethemaftercallingSaved%eaxargument1......argumentN32Caller-saveRegisterspush%eaxpushargumentN...pushargument1callcallee%ebp%espretaddrCaller

Frame33CallingConventionCallee-saveregisters%ebx,%esi,%ediSavedbycalleeCallercanusetheseregistersfreelyCalleemustsavethembeforeusingCalleemustrestorethembeforereturn34Callee-saveRegisterscallcalleepush%ebpmov%esp,%ebppush%ebx...Old%ebpSaved%ebxCallee

Frame%ebp%espretaddr35Procedure/FunctionImplementation

Invokecallee:call(newinstructions)

Returntocaller:ret(newinstructions)

Passingdata:stack,register

Registers:callingconventionLocalvariable:stack36LocalVariableWhynotstorelocalvariablesinregisters?NoenoughregistersArrayandstructures(e.g.,a[2])Needaddress(e.g.,&a)Old%ebpLocalvariableSavedregs37LocalVariableAllocationBelowsavedregsorold%ebpmove/sub%esp,(e.g.,subl$4,%esp)De-allocationmove/add%esp,(e.g.,addl$4,%esp)UsageRelativeto%esp/%ebp,(e.g.,movl%eax,8(%esp))Callee

Frame%ebp%espretaddr38PutitTogetherCaller

Frame%ebp%espcaller-saveregisters39PutitTogether1.Savecaller-saveregisters

(%eax,%edx,%ecx)Caller

Frame%ebp%esparguments(n~1)caller-saveregisters40PutitTogether1.Savecaller-saveregisters

(%eax,%edx,%ecx)2.Pushactualarguments

fromrighttoleftCaller

Frame%ebp%esparguments(n~1)caller-saveregisters41PutitTogether1.Savecaller-saveregisters

(%eax,%edx,%ecx)2.Pushactualarguments

fromrighttoleft3.CallinstructionSavereturnaddressTransfercontroltocalleeretaddrCaller

Frame%ebp%esparguments(n~1)42PutitTogether4.Savecaller%ebpcaller-saveregisters%ebpretaddrCaller

Frame%ebp%esparguments(n~1)43PutitTogether4.Savecaller%ebp5.Setcallee%ebpcaller-saveregistersold%ebpretaddrCaller

Frame%esp/%ebparguments(n~1)44PutitTogether4.Savecaller%ebp5.Setcallee%ebp6.Savecallee-saveregisters

(%ebx,%edi,%esi)caller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisters%ebp%esparguments(n~1)45PutitTogether4.Savecaller%ebp5.Setcallee%ebp6.Savecallee-saveregisters

(%ebx,%edi,%esi)7.Allocatespaceforlocal

variablecaller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisterslocalvariables%ebp%esp46PutitTogether...n-4.savereturnvaluein%eaxarguments(n~1)caller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisterslocalvariables%ebp%esp47PutitTogether...n-4.savereturnvaluein%eaxn-3.de-allocatelocalvariablearguments(n~1)caller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisterslocalvariables%ebp%esp48PutitTogether...n-4.savereturnvaluein%eaxn-3.de-allocatelocalvariablen-2.Restorecallee-saveregistersarguments(n~1)caller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisterslocalvariables%ebp%esp/49PutitTogether...n-4.savereturnvaluein%eaxn-3.de-allocatelocalvariablen-2.Restorecallee-saveregistersn-1.Restorecaller%ebparguments(n~1)caller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisterslocalvariables%ebp%esp50PutitTogether...n-4.savereturnvaluein%eaxn-3.de-allocatelocalvariablen-2.Restorecallee-saveregistersn-1.Restorecaller%ebpn.RetinstructionpopreturnaddressTransfercontroltocallerarguments(n~1)caller-saveregistersold%ebpretaddrCaller

Framecallee-saveregisterslocalvariables%ebp%esp51Example1intswap_add(int*xp,int*yp)2{3 intx=*xp;4 inty=*yp;56 *xp=y;7 *yp=x;8 returnx+y;9}1052Example11intcaller()12{13 intarg1=534;14 intarg2=1057;15 intsum=swap_add(&arg1,&arg2);16 intdiff=arg1-arg2;1718 returnsum*diff;19}53Finishingcodeinswap_add0Saved%ebp-4arg2(534)-8arg1(1057)-12yp(&arg2)-16xp(&arg1)-20ReturnAddrSaved%ebpSaved%ebxStackframeforcaller12popl%ebxRestore%ebx13movl%ebp,%esp

Restore%esp14popl%ebpRestore%ebp15ret

ReturntocallerCallbyvalue%ebpxp(=&arg1=%ebp+16)%edxyp(=&arg2=%ebp+20)%ecxoriginalvalue%ebx1591%eax%esp54Array55AccessingArrayTA[N];AllocateacontiguousregioninmemoryThesizeoftheregionissizeof(T)

*

NbytesThestartingaddressofanarrayAisdenotedasXAArrayelementscanbeaccessedUsinganintegerindexrangingbetween0andN-1ArrayelementiisstoredataddressXA+sizeof(T)*i56Array012345678910110481216chara[12];xaxa+4xa+8char*b[5];xbxb+4xb+8xb+12xb+1657Array0481216doublec[2];xcxc+8double*d[5];xdxd+4xd+8xd+12xd+1658PointerArithmeticAdditionandsubtractionp+i,p-i(resultisapointer)p-q(resultisanint)Referencing&dereferencing*p,&ESubscriptionA[i],*(A+i)59MemoryreferencinginstructionEisanarrayofint’sAddressofEisstoredinregister%edxIndexiisstoredinregister%ecxThearrayelementE[i]istranslatedintomovl (%edx,%ecx,4),%eax60PointerArithmeticExpressionTypeValueAssemblycodeEint*xEmovl%edx,%eaxE[0]intM[xE]movl(%edx),%eaxE[i]

intM[xE+4i]movl(%edx,%ecx,4),%eax&E[2]

int*xE+8leal8(%edx,)%eaxE+i-1int*xE+4i-4lea-4(%edx,%ecx,4),%eax*(&E[i]+i)

intM[xE+4i+4i]movl(%edx,%ecx,8),%eax&E[i]-E

intimovl%ecx,%eax61NestedArrayintA[4][3];ArrayAisatwo-dimensionalarraywithfourrowsandthreecolumnsItisreferencedasA[0][0]throughA[3][2]RowElementAddressA[0]A[0][0]xAA[0][1]xA+4A[0][2]xA+8A[1]A[1][0]xA+12A[1][1]xA+16A[1][2]xA+20A[2]A[2][0]xA+24A[2][1]xA+28A[2][2]xA+32A[3]A[3][0]xA+36A[3][1]xA+40A[3][2]xA+4462NestedArrayintA[4][3];Arrayofarraytypedefintrow3_t[3];

row3_tA[4];ArrayAcontains4elements,

eachrequiring12bytesto

store3integersThewholesizeofarrayAis48bytesRowmajororderedinmemory63NestedArrayTD[R][C];D[i][j]isatmemoryaddressxD+L*(C*i+j)Lissizeof(T)64AccessA[i,j]ItisinmemoryM[xA+j*4+i*12]%eaxcontainsxA%edxholdsi,%ecxholdsjsall$2,%ecx #j*4leal(%edx,%edx,2),%edx#i*3leal(%ecx,%edx,4),%ecx#j*4+i*12movl(%eax,%ecx),%eax

65Fixed-sizeArrays#defineN16typedefintfix_matrix[N][N];/*Computei,koffixedmatrixproduct*/intfix_prod_ele(fix_matrixA,fix_matrixB,

inti,intk){

intj;

intresult=0;

for(j=0;j<N;j++)

result+=A[i][j]*B[j][k];

returnresult;}66Fixed-sizeArrays/*Computei,koffixedmatrixproduct*/intfix_prod_ele_opt(fix_matrixA,fix_matrixB,

inti,intk){

int*Arow=&A[i][0],*Bptr=&B[0][k];

intj,result=0;

for(j=0;j<16;j++){

result+=Arow[j]*(*Bptr);

Bptr+=N;

}

returnresult;}67Fixed-sizeArraysAptrin%esi,Bptrin%ecxresultin%ebx,jin%edx.L6: #loop:movl(%ecx),%eax #Get*Bptrimull(%esi,%edx,4),%eax #MultiplybyArow[j]addl%eax,%ebx #Addtoresultaddl$1,%edx #j++addl$64,%ecx #Add16*4toBptrcmpl$16,%edx #comparej:16jne.L6 #if!=,gotoloop68Variable-SizeArraysintvar_ele(intn,intA[n][n],inti,intj){

returnA[i][j];}DeclareanarrayintA[exp1][exp2]eitherasalocalvariableorasanargumenttoafunctionThedimensionsofthearrayaredeterminedbyevaluatingtheexpressionsatthetimethedeclarationisencounterd69AssemblyCodenat%ebp+8,Aat%ebp+12iat%ebp+16,jat%ebp+20movl8(%ebp),%eax #Getnsall$2,%eax #Compute4*nmovl%eax,%edx #Copy4*nimull16(%ebp),%edx #Compute4*n*imovl20(%ebp),%eax #Getjsall$2,%eax #Compute4*jaddl12(%ebp),%eax #ComputexA+4∗jmovl(%eax,%edx),%eax#ReadfromxA+4∗(n∗i+j)70HeterogeneousDataStructures&Alignment71OutlineStructUnionAlignmentPointers72StructuresGroupobjectsintoasingleobjectstructrect{ intllx;/*Xcoordinateoflower-leftcorner*/ intlly;/*Ycoordinateoflower-leftcorner*/ intcolor;/*Codingofcolor*/ intwidth;/*Width(inpixels)*/ intheight;/*Height(inpixels)*/};73StructuresMemorylayoutAllthecomponentsarestoredinacontiguousregionofmemoryApointertoastructureistheaddressofitsfirstbyte74Structurestructrec{ inti; intj; inta[3]; int*p;}*r;ija[0]a[1]a[2]pContentsOffset0482075StructureReferencestostructureelementsUsingoffsetsasdisplacementsr->j=r->i(Copyelementr->itoelementr->j)risinregister%edx.1 movl (%edx),%eax Getr->i2 movl %eax,4(%edx) Storeinr->jija[0]a[1]a[2]pContentsOffset0482076Structure&(r->a[i])rin%eax,iin%edx：1leal8(%eax,%edx,4),%ecx Generate&r->a[i]ija[0]a[1]a[2]pContentsOffset0482077Structurer->p=&r->a[r->i+r->j];rinregister%edx:1 movl4(%edx),%eax Getr->j2 addl(%edx),%eax Addr->i3 leal8(%edx,%eax,4),%eax Compute&r->a[r->i+r->j]4 movl%eax,20(%edx) Storeinr->pija[0]a[1]a[2]pContentsOffset0482078UnionsAsingleobjectcanbereferencedbyusingdifferentdatatypesThesyntaxofauniondeclarationisidenticaltothatforstructures,butitssemanticsareverydifferentRatherthanhavingthedifferentfieldsreferencedifferentblocksofmemory,theyallreferencethesameblock79UnionsstructS3{ charc; inti[2]; doublev;};unionU3{ charc; inti[2]; doublev;};TypecivsizeS3041220U30008Theoffsetsofthefields,aswellasthetotalsizeofdatatypesS3andU3,are:80UnionsstructNODE{ intis_leaf; union{ struct{ structNODE*left; structNODE*right; }internal; doubledata; }info;};81Unions1

unsignedfloat2bit(floatf)2

{3

union{4

floatf;5

unsignedu;6

}temp;7

temp.f=f;8

returntemp.u;9

}1

movl 8(%ebp),%eax82AlignmentAlignmentrestrictionsTheaddressforsometypeofobjectmustbeamultipleofsomevaluek

(typically2,4,or8)SimplifythehardwaredesignoftheinterfacebetweentheprocessorandthememorysystemInIA32hardwarewillworkcorrectlyregardlessofthealignmentofdataAligneddatacanimprovememorysystemperformance83AlignmentLinuxalignmentrestriction1-bytedatatypesareabletohaveanyaddress2-bytedatatypesmusthaveanaddressthatismultipleof2Anylargerdatatypesmusthaveanaddressthatismultipleof484SimpleExamplestructxxx{ inti; charc; doubled;};structxxxx[2];0x000x040x080x0C0x100x14&x[0].i&x[0].c&x[0].d&x[1].iComplexExamplestructxxx{shorts;charc0;inti;longl;charc1;chara[2];doubled;charc2;};structxxxx[2];850x000x040x080x0C0x100x140x180x1C&x[0].s&x[0].c0&x[0].i&x[0].l&x[0].c1&x[0].a[0]&x[0].a[1]&x[0].d&x[0].c2&x[1].s86Arraystructccc{charc1;chara[3];charc2;};structcccc[2];0x000x040x080x0C0x100x14&c[0].c1&c[0].a[0]&c[0].c2&c[1].c1&c[1].a[0]&c[1].c287Arraystructccc{charc1;shorta[3];charc2;};structssss[2];0x000x040x080x0C0x100x14&s[0].c1&s[0].c2&s[0].a[0]&s[1].c1&s[1].c2&s[1].a[0]88Arraystructiii{charc1;inta[3];charc2;};structiiii[2];0x000x040x080x0C0x100x14&s[0].c1&s[0].c2&x[0].i&s[1].c189PointersEverypointerhasatypeIftheobjecthastypeTApointertothisobjecthastypeT*Specialvoid*typeRepresentsagenericpointermallocreturnsagenericpointerEverypointerhasavalue90PointersPointersarecreatedwiththe&operatorAppliedtolvalueexpressionLvalueexpressioncanappearontheleftsideofassignmentPointersaredereferencedwiththeoperator*TheresultisavaluehavingthetypeassociatedwiththepointerArraysandpointersareclosedrelatedThenameofarraycanbeviewedasapointerconstantip[0]isequivalentto*ip91PointerArithmeticAdditionandsubtractionp+i,p-i(resultisapointer)p-q(resultisaint)Referencing&dereferencing*p,&ESubscriptionA[i],*(A+i)92Pointerscanpointtofunctionsvoid(*f)(int*)fisapointertofunctionThefunctiontakenint*asargumentThereturntypeofthefunctionisvoidAssignmentmakesfpointtofuncf=funcNoticetheprecedenceoftheoperatorsvoid*f(int*)declaresfisafunction(void*)f(int*)93PointerDeclarationchar **argv;int (*daytab)[13]int (*comp)()char (*(*x())[])()Functionreturningpointertoarray[]ofpointertofunctionreturningcharchar (*(*x[3])())[5]Array[3]ofpointertofunctionreturningpointertoarray[5]ofchar94CoperatorsOperators Associativity()[]->.++-- lefttoright!~++--+-*&(type)sizeof righttoleft*/% lefttoright+- lefttoright<<>> lefttoright<<=>>= lefttoright==!= lefttoright& lefttoright^ lefttoright| lefttoright&& lefttoright|| lefttoright?: righttoleft=+=-=*=/=%=&=^=!=<<=>>= righttoleft, lefttorightNote:Unary+,-,and*havehigherprecedencethanbinaryforms95ParameterPassingCallbyvaluef(xp)Callbyreferencef(&xp)96BufferOverflow97Out-of-BoundsMemoryReferences1/*Implementationoflibraryfunctiongets()*/2char*gets(char*s)3{4 intc;5 char*dest=s;6 intgot_char=0;/Hasatleastonecharacterbeenread?*/7 while((c=getchar())!=’\n’&&c!=EOF){8 *dest++=c;/*Noboundschecking*/9 gotchar=1;10 }11 *dest++=’\0’; /*TerminateString*/12 if(c==EOF&&!gotchar)13 returnNULL;/*Endoffileorerror*/14 returns;15}98Out-of-BoundsMemoryReferences14/*Readinputlineandwriteitback*/15voidecho()16{17 charbuf[8]; /*Waytoosmall!*/18 gets(buf);19 puts(buf);20}99Out-of-BoundsMemoryReferencesReturnaddressSaved%ebpSaved%ebx[7][6][5][4][3][2][1][0]%ebpbufStackframeforcallerStackframeforecho100Out-of-BoundsMemoryReferencesReturnaddressSaved%ebp[11][10][9][8][7][6][5][4][3][2][1][0]%ebpbufStackframeforcallerStackframeforecho101Out-of-BoundsMemoryReferencesReturnaddress[15]1[4][13][12][11][10][9][8][7][6][5][4][3][2][1][0]%ebpbufStackframeforcallerStackframeforecho102Out-of-BoundsMemoryReferences[19][18][17][16][15]1[4][13][12][11][10][9][8][7][6][5][4][3][2][1][0]%ebpbufStackframeforcallerStackframeforecho103MaliciousUseofBufferOverflowvoidbar(){charbuf[64];gets(buf);...}voidfoo(){bar();...}returnaddressAStackaftercalltogets()BfoostackframebarstackframeBexploitcodepaddatawrittenbygets()104TheFamousInternetWormofNovember1988TogainaccesstomanyofthecomputersacrosstheInternet4differentwaysOnewasabufferoverflowattackonthefingerdHundredsofmachineswereeffectivelyparalyzedTheauthorofthewormwascaughtandprosecuted.Hewassentencedto3yearsprobation400hoursofcommunityserviceanda$10,500fine105MorrisWormRobertTappanMorrisbornNovember8,1965aprofessoratMITHeisthesonofRobertMorristheformerchiefscientistattheNationalComputerSecurityCenteradivisionoftheNationalSecurityAgency(NSA)106ThwartingBufferOverflowAttacksStackRandomizationStackCorruptionDetectionLimitingExecutableCodeRegions107Machine-LevelRepresentation

ofPrograms(x86-64)108SizeofDataTypeDataTypesinCLanguageDataTypeIA32(Linux)x86-64(Linux)char11short22int44longint48longlong88float44double88longdouble1216pointer(e.g.char*)48IntegerRegisterExtendexistregistersto64bits%rbp%rsp%rdi%rsi%rdx%rcx%rbx%rax%eax%edx%ecx%ebx%esi%edi%esp%ebp%al%ah%dl%dh%cl%ch%bl%bhIntegerRegisterAdd8new64bitsregisters%rbp%rsp%rdi%rsi%rdx%rcx%rbx%rax%eax%ebx%ecx%edx%esi%edi%esp%ebp%al%ah%dl%dh%cl%ch%bl%bh%r15%r14%r13%r12%r11%r10%r9%r8%r8d%r9d%r10d%r11d%r12d%r13d%r14d%r15d111InstructionsLongwordl(4Bytes)↔Quadwordq(8Bytes)NewInstructionsmovl→movqaddl→addqsall→salqetc.32-bitinstructionsgenerate32-bitresultsSethigherorderbitsofdestinationregisterto0Example:addlIA32/LinuxStackFrameCallerStackFrameArgumentsforthiscallReturnAddress(pushedby“call”)CalleeStackFrameOld%ebp(savedby“push%ebp”)SavedregistersLocalvariablesArgumentsfornextcall112Procedures-StackRetAddrArgumentsOld%ebpSavedregistersLocalvariablesArguments%ebp%espframepointerstackpointerIA32/LinuxRegisterUsage%eax,%edx,%ecxCallersavespriorthecall

ifvaluesareusedbylater%eaxReturnintegervalue%ebx,%esi,%ediCalleesavesifwantto

usedthem%esp,%ebpspecial113Procedures-Register%eax%edx%ecx%ebx%esi%edi%esp%ebpCaller-SaveCallee-SaveSpecial%rbp%rsp%rdi%rsi%rdx%rcx%rbx%rax%r15%r14%r13%r12%r11%r10%r9%r8X86-64/LinuxRegisterUsageCaller-Save%rax%rcx%rdx

%rsi%rdi%r8%r9Callee-Save%rbx%rbp%r10%r12%r13%r14%r15Special%rsp,%r11114Procedures-Register%rbp%rsp%rdi%rsi%rdx%rcx%rbx%rax%r15%r14%r13%r12%r11%r10%r9%r8X86-64/LinuxRegisterUsageArgumentspassedviaregs%rcx%rdx%rsi%rdi

%r8%r9Ifmorethan6integer

parameters,thenpass

restonstackReturnvalueby%raxNoframepointerSpecial%rspstackpointer%r11usedforlinking115Procedures-Register%rbp%rsp%rdi%rsi%rdx%rcx%rbx%rax%r15%r14%r13%r12%r11%r10%r9%r8%rdiarg#1%rsiarg#2%rdxarg#3%rcxarg#4%r9arg#6%r8arg#5%raxret%rspstack%r11linkx86-64/LinuxStackFrameCallerStackFrameArgumentspassedviaregistersReturnAddress(pushedby“call”)CalleeStackFrameSavedregistersLocalvariables116Procedures-StackRetAddrSavedregistersLocalvariables%rspstackpointer117X86-64SwapOperandspassedinregistersFirst(xp)in%rdi,second(yp)in%rsiNostackoperationsrequired(exceptret)AvoidstackCanholdalllocalinformationinregistersvoidswap(long*xp,long*yp){longt0=*xp;longt1=*yp;*xp=t1;*yp=t0;}swap:movq(%rdi),%rdxmovq(%rsi),%raxmovq%rax,(%rdi)movq%rdx,(%rsi)ret118AlignmentBytesIA32x86-64TypeAlignmentTypeAlignment1charNocharNo2short02short024int,float,pointer002int,

float0028double0002(Win)002(Lin)double,pointer000212/16longdouble002longdouble00002ExampleIA32LinuxK=4;doubletreatedlikea4-bytedatatypeX86-64orIA32Windows:K=8;duetodoubleelementstructs1{charc;inti[2];doubled;}*p;C3bytesi[0]i[1]4bytesdp+0p+4p+8p+16p+24C3bytesi[0]i[1]dp+0p+4p+8p+12p+20119120从程序到可执行代码

指令编码和汇编器

1次课Y86ProcessorStateProgramRegistersSame8aswithIA32.Each32bitsConditionCodesSingle-bitflagssetbyarithmeticorlogicalinstructionsOF:OverflowZF:ZeroSF:NegativeProgramCounterIndicatesaddressofinstructionMemoryByte-addressablestoragearrayWordsstoredinlittle-endianbyteorder%eax%ecx%edx%ebx%esi%edi%esp%ebpProgramregistersConditioncodesPCMemoryOFZFSFY86InstructionsFormat1--6bytesofinformationreadfrommemoryCandetermineinstructionlengthfromfirstbyteNotasmanyinstructiontypes,andsimplerencodingthanwithIA32Eachaccessesandmodifiessomepart(s)oftheprogramstateY86InstructionsFormat(P259)1--6bytesofinformationreadfrommemoryCandetermineinstructionlengthfromfirstbyteNotasmanyinstructiontypes,andsimplerencodingthanwithIA32Eachaccessesandmodifiessomepart(s)oftheprogramstateErrata:JXXandcallare5byteslong.Format(P259)1--6bytesofinformationreadfrommemoryCandetermineinstructionlengthfromfirstbyteNotasmanyinstructiontypes,andsimplerencodingthanwithIA32Eachaccessesandmodifiessomepart(s)oftheprogramstateErrata:JXXandcallare5byteslong.EncodingRegistersEachregisterhas4-bitIDSameencodingasinIA32,butIA32usingonly3-bitIDRegisterIDFindicates“noregister”Willusethisinourhardwaredesigninmultipleplaces%eax%ecx%edx%ebx%esi%edi%esp%ebp012367451InstructionExampleAdditionInstructione.g.,addl%eax,%esi

Encoding:

6006Two-byteencodingFirstindicatesinstructiontypeSecondgivessourceanddestinationregistersEncodedRepresentationGe