在XP系统中， 系统服务在内核的入口是KiFastCallEntry，我们从该入口开始，分析这一段代码都做了什么工作。
由于水平有限和背景知识不够，本人没有完全读懂它们，作为抛砖引玉，我先将我所看懂的和大家分享，希望大家多多指教!
KiFastCallEntry的主要功能有：
●
nt!KiFastCallEntry:
// 当线程在内核模式下执行时的数据段选择子是23h
// 当线程在内核模式下执行时，在FS寄存器中加载的是选择子30，
// 用于寻址PCR结构体
804de6f0 mov ecx,23h
804de6f5 push 30h
804de6f7 pop fs
// 23h->ds;23h->es
804de6f9 mov ds,cx
804de6fb mov es,cx
// dword ptr fs:[40h] == dword ptr ds:[0FFDFF040h]{TSS}
// dword ptr [ecx+4] 为当前线程的内核模式栈顶指针的值
804de6fd mov ecx,dword ptr ds:[0FFDFF040h]
804de703 mov esp,dword ptr [ecx+4]
// ==========================================
// 将当前（执行Sysenter前各寄存器的值）上下文压入系统堆栈，
// _KTRAP_FRAME.HardwareSegSs
804de706 push 23h
// _KTRAP_FRAME.HardwareEsp
804de708 push edx
// _KTRAP_FRAME.EFags
804de709 pushfd
804de70a push 2
804de70c add edx,8
// EFlags = 2
804de70f popfd
804de710 or byte ptr [esp+1],2
// _KTRAP_FRAME.SegCs
804de715 push 1Bh
// ds:[0FFDF0304h] 是SystemCallReturn（_KUser_Shared_Data）
// _KTRAP_FRAME.Eip
804de717 push dword ptr ds:[0FFDF0304h]
//_KTRAP_FRAME.ErrorCode
804de71d push 0
//_KTRAP_FRAME.Ebp
804de71f push ebp
//_KTRAP_FRAME.Ebx
804de720 push ebx
//_KTRAP_FRAME.Esi
804de721 push esi
//_KTRAP_FRAME.Edi
804de722 push edi
//ebx<-_KPCR.SelfPcr
804de723 mov ebx,dword ptr ds:[0FFDFF01Ch]
// _KTRAP_FRAME.SegFs
804de729 push 3Bh
//esi=_KPCR.PrcbData.CurrentThread
804de72b mov esi,dword ptr [ebx+124h]
//_KTRAP_FRAME.ExceptionList
804de731 push dword ptr [ebx]
// 初始化链表
804de733 mov dword ptr [ebx],0FFFFFFFFh
//ebp = KPCR.PrcbData.CurrentThread. InitialStack
804de739 mov ebp,dword ptr [esi+18h]
//_KTRAP_FRAME.PreviousPreviousMode = 1
804de73c push 1
// esp->_KTRAP_FRAME
804de73e sub esp,48h
// ebp ->_KTRAP_FRAME
804de741 sub ebp,29Ch
// CurrentThread +124 = 1
804de747 mov byte ptr [esi+140h],1
// 比较
804de74e cmp ebp,esp
// 不相等，发生了异常
804de750 jne nt!KiFastCallEntry2+0x24 (804de6c8)
// _KTRAP_FRAME.Dr7 = 0
804de756 and dword ptr [ebp+2Ch],0
// [esi+2Ch]是KTHREAD.DebugActive当前线程的调试标志
//不等于0xFF表示调试中？
804de75a test byte ptr [esi+2Ch],0FFh
804de75e mov dword ptr [esi+134h],ebp
804de764 jne nt!Dr_FastCallDrSave (804de5b0)
// ebx = _KTRAP_FRAME.Ebp
804de76a mov ebx,dword ptr [ebp+60h]
// edi = _KTRAP_FRAME.EIP
804de76d mov edi,dword ptr [ebp+68h]
// _KTRAP_FRAME.DbgArgPointer
804de770 mov dword ptr [ebp+0Ch],edx
// _KTRAP_FRAME.DbgArgPointer = DbgArgMark
804de773 mov dword ptr [ebp+8],0BADB0D00h
//_KTRAP_FRAME.DbgEbp
804de77a mov dword ptr [ebp],ebx
//_KTRAP_FRAME.DbgEip = _KTRAP_FRAME.EIP
804de77d mov dword ptr [ebp+4],edi
//==================================
// 开中断
804de780 sti
//eax为函数序号，但是在KeServiceDescriptorTableShadow时
//是函数序号+1000h,所以在KeServiceDescriptorTableShadow
//经过下面运算ecx最终为10h，否则为0
804de781 mov edi,eax
804de783 shr edi,8
804de786 and edi,30h
804de789 mov ecx,edi
//KTHREAD.ServiceTable gdi32.dll和user32.dll调用时,
//ServiceTable为KeServiceDescriptorTableShadow，
//ntdll.dll调用时ServiceTable为KeServiceDescriptorTable
//在KeServiceDescriptorTableShadow时+10正好得到win32.sys调用
804de78b add edi,dword ptr [esi+0E0h]
804de791 mov ebx,eax
//保留三个字节，得到正真的序号
804de793 and eax,0FFFh
//和ssdt或shadow ssdt总共项数比较，eax大则跳
804de798 cmp eax,dword ptr [edi+8]
804de79b jae nt!KiBBTUnexpectedRange (804de4e2)
//判断是shadow ssdt还是ssdt，不跳则是shadow ssdt，跳则是ssdt
804de7a1 cmp ecx,10h
804de7a4 jne nt!KiFastCallEntry+0xcc (804de7c0)
// TIB地址送ecx
804de7a6 mov ecx,dword ptr ds:[0FFDFF018h]
// [ecx+0xf70] 是什么东东？
804de7ac xor ebx,ebx
804de7ae or ebx,dword ptr [ecx+0F70h]
804de7b4 je nt!KiFastCallEntry+0xcc (804de7c0)
804de7b6 push edx
804de7b7 push eax
804de7b8 call dword ptr [nt!KeGdiFlushUserBatch (8055a164)]
804de7be pop eax
804de7bf pop edx
// SSDT
// ds:[0FFDFF638h](fs:[638h]) KeSystemCalls
// 仅仅用来记录系统调用的次数，无太多用处
804de7c0 inc dword ptr ds:[0FFDFF638h]
// edx中是参数(堆栈顶的指针)
804de7c6 mov esi,edx
804de7c8 mov ebx,dword ptr [edi+0Ch]
804de7cb xor ecx,ecx
804de7cd mov cl,byte ptr [eax+ebx]
//edi=KeServiceDescriptorTable->ServiceTableBase
804de7d0 mov edi,dword ptr [edi]
//计算服务例程地址（edi为KiServiceTable，eax为函数序号）
804de7d2 mov ebx,dword ptr [edi+eax*4]
804de7d5 sub esp,ecx
804de7d7 shr ecx,2
804de7da mov edi,esp
// 检查esi是否指向用户空间
804de7dc cmp esi,dword ptr ds:[0EED02CF4h]
804de7e2 jae nt!KiSystemCallExit2+0x9f (804de990)
//把参数复制到内核
804de7e8 rep movs dword ptr es:[edi],dword ptr [esi]
//转入服务例程入口
804de7ea call ebx
// 恢复堆栈
804de7ec mov esp,ebp
// fs:[124h]中储存着当前线程的ETHREAD
// ETHREAD的偏移134h处为TrapFrame
804de7ee mov ecx,dword ptr ds:[0FFDFF124h]
804de7f4 mov edx,dword ptr [ebp+3Ch]
804de7f7 mov dword ptr [ecx+134h],edx
。。。。
804de904 sysexit
//附相关数据结构 ：
lkd> dt nt!_KPCR
+0x000 NtTib : _NT_TIB
+0x01c SelfPcr : Ptr32 _KPCR
+0x020 Prcb : Ptr32 _KPRCB
+0x024 Irql : UChar
+0x028 IRR : Uint4B
+0x02c IrrActive : Uint4B
+0x030 IDR : Uint4B
+0x034 KdVersionBlock : Ptr32 Void
+0x038 IDT : Ptr32 _KIDTENTRY
+0x03c GDT : Ptr32 _KGDTENTRY
+0x040 TSS : Ptr32 _KTSS
+0x044 MajorVersion : Uint2B
+0x046 MinorVersion : Uint2B
+0x048 SetMember : Uint4B
+0x04c StallScaleFactor : Uint4B
+0x050 DebugActive : UChar
+0x051 Number : UChar
+0x052 Spare0 : UChar
+0x053 SecondLevelCacheAssociativity : UChar
+0x054 VdmAlert : Uint4B
+0x058 KernelReserved : [14] Uint4B
+0x090 SecondLevelCacheSize : Uint4B
+0x094 HalReserved : [16] Uint4B
+0x0d4 InterruptMode : Uint4B
+0x0d8 Spare1 : UChar
+0x0dc KernelReserved2 : [17] Uint4B
+0x120 PrcbData : _KPRCB
lkd> dt nt!_NT_TIB
+0x000 ExceptionList : Ptr32 _EXCEPTION_REGISTRATION_RECORD
+0x004 StackBase : Ptr32 Void
+0x008 StackLimit : Ptr32 Void
+0x00c SubSystemTib : Ptr32 Void
+0x010 FiberData : Ptr32 Void
+0x010 Version : Uint4B
+0x014 ArbitraryUserPointer : Ptr32 Void
+0x018 Self : Ptr32 _NT_TIB
lkd> dt nt!_KPRCB
+0x000 MinorVersion : Uint2B
+0x002 MajorVersion : Uint2B
+0x004 CurrentThread : Ptr32 _KTHREAD
+0x008 NextThread : Ptr32 _KTHREAD
+0x00c IdleThread : Ptr32 _KTHREAD
+0x010 Number : Char
+0x011 Reserved : Char
+0x012 BuildType : Uint2B
+0x014 SetMember : Uint4B
+0x018 CpuType : Char
+0x019 CpuID : Char
+0x01a CpuStep : Uint2B
+0x01c ProcessorState : _KPROCESSOR_STATE
+0x33c KernelReserved : [16] Uint4B
+0x37c HalReserved : [16] Uint4B
+0x3bc PrcbPad0 : [92] UChar
+0x418 LockQueue : [16] _KSPIN_LOCK_QUEUE
+0x498 PrcbPad1 : [8] UChar
+0x4a0 NpxThread : Ptr32 _KTHREAD
+0x4a4 InterruptCount : Uint4B
+0x4a8 KernelTime : Uint4B
+0x4ac UserTime : Uint4B
+0x4b0 DpcTime : Uint4B
+0x4b4 DebugDpcTime : Uint4B
+0x4b8 InterruptTime : Uint4B
+0x4bc AdjustDpcThreshold : Uint4B
+0x4c0 PageColor : Uint4B
+0x4c4 SkipTick : Uint4B
+0x4c8 MultiThreadSetBusy : UChar
+0x4c9 Spare2 : [3] UChar
+0x4cc ParentNode : Ptr32 _KNODE
+0x4d0 MultiThreadProcessorSet : Uint4B
+0x4d4 MultiThreadSetMaster : Ptr32 _KPRCB
+0x4d8 ThreadStartCount : [2] Uint4B
+0x4e0 CcFastReadNoWait : Uint4B
+0x4e4 CcFastReadWait : Uint4B
+0x4e8 CcFastReadNotPossible : Uint4B
+0x4ec CcCopyReadNoWait : Uint4B
+0x4f0 CcCopyReadWait : Uint4B
+0x4f4 CcCopyReadNoWaitMiss : Uint4B
+0x4f8 KeAlignmentFixupCount : Uint4B
+0x4fc KeContextSwitches : Uint4B
+0x500 KeDcacheFlushCount : Uint4B
+0x504 KeExceptionDispatchCount : Uint4B
+0x508 KeFirstLevelTbFills : Uint4B
+0x50c KeFloatingEmulationCount : Uint4B
+0x510 KeIcacheFlushCount : Uint4B
+0x514 KeSecondLevelTbFills : Uint4B
+0x518 KeSystemCalls : Uint4B
+0x51c SpareCounter0 : [1] Uint4B
+0x520 PPLookasideList : [16] _PP_LOOKASIDE_LIST
+0x5a0 PPNPagedLookasideList : [32] _PP_LOOKASIDE_LIST
+0x6a0 PPPagedLookasideList : [32] _PP_LOOKASIDE_LIST
+0x7a0 PacketBarrier : Uint4B
+0x7a4 ReverseStall : Uint4B
+0x7a8 IpiFrame : Ptr32 Void
+0x7ac PrcbPad2 : [52] UChar
+0x7e0 CurrentPacket : [3] Ptr32 Void
+0x7ec TargetSet : Uint4B
+0x7f0 WorkerRoutine : Ptr32 void
+0x7f4 IpiFrozen : Uint4B
+0x7f8 PrcbPad3 : [40] UChar
+0x820 RequestSummary : Uint4B
+0x824 SignalDone : Ptr32 _KPRCB
+0x828 PrcbPad4 : [56] UChar
+0x860 DpcListHead : _LIST_ENTRY
+0x868 DpcStack : Ptr32 Void
+0x86c DpcCount : Uint4B
+0x870 DpcQueueDepth : Uint4B
+0x874 DpcRoutineActive : Uint4B
+0x878 DpcInterruptRequested : Uint4B
+0x87c DpcLastCount : Uint4B
+0x880 DpcRequestRate : Uint4B
+0x884 MaximumDpcQueueDepth : Uint4B
+0x888 MinimumDpcRate : Uint4B
+0x88c QuantumEnd : Uint4B
+0x890 PrcbPad5 : [16] UChar
+0x8a0 DpcLock : Uint4B
+0x8a4 PrcbPad6 : [28] UChar
+0x8c0 CallDpc : _KDPC
+0x8e0 ChainedInterruptList : Ptr32 Void
+0x8e4 LookasideIrpFloat : Int4B
+0x8e8 SpareFields0 : [6] Uint4B
+0x900 VendorString : [13] UChar
+0x90d InitialApicId : UChar
+0x90e LogicalProcessorsPerPhysicalProcessor : UChar
+0x910 MHz : Uint4B
+0x914 FeatureBits : Uint4B
+0x918 UpdateSignature : _LARGE_INTEGER
+0x920 NpxSaveArea : _FX_SAVE_AREA
+0xb30 PowerState : _PROCESSOR_POWER_STATE
lkd> dt nt!_KTHREAD
+0x000 Header : _DISPATCHER_HEADER
+0x010 MutantListHead : _LIST_ENTRY
+0x018 InitialStack : Ptr32 Void
+0x01c StackLimit : Ptr32 Void
+0x020 Teb : Ptr32 Void
+0x024 TlsArray : Ptr32 Void
+0x028 KernelStack : Ptr32 Void
+0x02c DebugActive : UChar
+0x02d State : UChar
+0x02e Alerted : [2] UChar
+0x030 Iopl : UChar
+0x031 NpxState : UChar
+0x032 Saturation : Char
+0x033 Priority : Char
+0x034 ApcState : _KAPC_STATE
+0x04c ContextSwitches : Uint4B
+0x050 IdleSwapBlock : UChar
+0x051 Spare0 : [3] UChar
+0x054 WaitStatus : Int4B
+0x058 WaitIrql : UChar
+0x059 WaitMode : Char
+0x05a WaitNext : UChar
+0x05b WaitReason : UChar
+0x05c WaitBlockList : Ptr32 _KWAIT_BLOCK
+0x060 WaitListEntry : _LIST_ENTRY
+0x060 SwapListEntry : _SINGLE_LIST_ENTRY
+0x068 WaitTime : Uint4B
+0x06c BasePriority : Char
+0x06d DecrementCount : UChar
+0x06e PriorityDecrement : Char
+0x06f Quantum : Char
+0x070 WaitBlock : [4] _KWAIT_BLOCK
+0x0d0 LegoData : Ptr32 Void
+0x0d4 KernelApcDisable : Uint4B
+0x0d8 UserAffinity : Uint4B
+0x0dc SystemAffinityActive : UChar
+0x0dd PowerState : UChar
+0x0de NpxIrql : UChar
+0x0df InitialNode : UChar
+0x0e0 ServiceTable : Ptr32 Void
+0x0e4 Queue : Ptr32 _KQUEUE
+0x0e8 ApcQueueLock : Uint4B
+0x0f0 Timer : _KTIMER
+0x118 QueueListEntry : _LIST_ENTRY
+0x120 SoftAffinity : Uint4B
+0x124 Affinity : Uint4B
+0x128 Preempted : UChar
+0x129 ProcessReadyQueue : UChar
+0x12a KernelStackResident : UChar
+0x12b NextProcessor : UChar
+0x12c CallbackStack : Ptr32 Void
+0x130 Win32Thread : Ptr32 Void
+0x134 TrapFrame : Ptr32 _KTRAP_FRAME
+0x138 ApcStatePointer : [2] Ptr32 _KAPC_STATE
+0x140 PreviousMode : Char
+0x141 EnableStackSwap : UChar
+0x142 LargeStack : UChar
+0x143 ResourceIndex : UChar
+0x144 KernelTime : Uint4B
+0x148 UserTime : Uint4B
+0x14c SavedApcState : _KAPC_STATE
+0x164 Alertable : UChar
+0x165 ApcStateIndex : UChar
+0x166 ApcQueueable : UChar
+0x167 AutoAlignment : UChar
+0x168 StackBase : Ptr32 Void
+0x16c SuspendApc : _KAPC
+0x19c SuspendSemaphore : _KSEMAPHORE
+0x1b0 ThreadListEntry : _LIST_ENTRY
+0x1b8 FreezeCount : Char
+0x1b9 SuspendCount : Char
+0x1ba IdealProcessor : UChar
+0x1bb DisableBoost : UChar
lkd> dt nt!_KUSER_SHARED_DATA
+0x000 TickCountLow : Uint4B
+0x004 TickCountMultiplier : Uint4B
+0x008 InterruptTime : _KSYSTEM_TIME
+0x014 SystemTime : _KSYSTEM_TIME
+0x020 TimeZoneBias : _KSYSTEM_TIME
+0x02c ImageNumberLow : Uint2B
+0x02e ImageNumberHigh : Uint2B
+0x030 NtSystemRoot : [260] Uint2B
+0x238 MaxStackTraceDepth : Uint4B
+0x23c CryptoExponent : Uint4B
+0x240 TimeZoneId : Uint4B
+0x244 Reserved2 : [8] Uint4B
+0x264 NtProductType : _NT_PRODUCT_TYPE
+0x268 ProductTypeIsValid : UChar
+0x26c NtMajorVersion : Uint4B
+0x270 NtMinorVersion : Uint4B
+0x274 ProcessorFeatures : [64] UChar
+0x2b4 Reserved1 : Uint4B
+0x2b8 Reserved3 : Uint4B
+0x2bc TimeSlip : Uint4B
+0x2c0 AlternativeArchitecture : _ALTERNATIVE_ARCHITECTURE_TYPE
+0x2c8 SystemExpirationDate : _LARGE_INTEGER
+0x2d0 SuiteMask : Uint4B
+0x2d4 KdDebuggerEnabled : UChar
+0x2d5 NXSupportPolicy : UChar
+0x2d8 ActiveConsoleId : Uint4B
+0x2dc DismountCount : Uint4B
+0x2e0 ComPlusPackage : Uint4B
+0x2e4 LastSystemRITEventTickCount : Uint4B
+0x2e8 NumberOfPhysicalPages : Uint4B
+0x2ec SafeBootMode : UChar
+0x2f0 TraceLogging : Uint4B
+0x2f8 TestRetInstruction : Uint8B
+0x300 SystemCall : Uint4B
+0x304 SystemCallReturn : Uint4B
+0x308 SystemCallPad : [3] Uint8B
+0x320 TickCount : _KSYSTEM_TIME
+0x320 TickCountQuad : Uint8B
+0x330 Cookie : Uint4B
lkd> dt _KTRAP_FRAME
nt!_KTRAP_FRAME
+0x000 DbgEbp : Uint4B
+0x004 DbgEip : Uint4B
+0x008 DbgArgMark : Uint4B
+0x00c DbgArgPointer : Uint4B
+0x010 TempSegCs : Uint4B
+0x014 TempEsp : Uint4B
+0x018 Dr0 : Uint4B
+0x01c Dr1 : Uint4B
+0x020 Dr2 : Uint4B
+0x024 Dr3 : Uint4B
+0x028 Dr6 : Uint4B
+0x02c Dr7 : Uint4B
+0x030 SegGs : Uint4B
+0x034 SegEs : Uint4B
+0x038 SegDs : Uint4B
+0x03c Edx : Uint4B
+0x040 Ecx : Uint4B
+0x044 Eax : Uint4B
+0x048 PreviousPreviousMode : Uint4B
+0x04c ExceptionList : Ptr32 _EXCEPTION_REGISTRATION_RECORD
+0x050 SegFs : Uint4B
+0x054 Edi : Uint4B
+0x058 Esi : Uint4B
+0x05c Ebx : Uint4B
+0x060 Ebp : Uint4B
+0x064 ErrCode : Uint4B
+0x068 Eip : Uint4B
+0x06c SegCs : Uint4B
+0x070 EFlags : Uint4B
+0x074 HardwareEsp : Uint4B
+0x078 HardwareSegSs : Uint4B
+0x07c V86Es : Uint4B
+0x080 V86Ds : Uint4B
+0x084 V86Fs : Uint4B
+0x088 V86Gs : Uint4B
初始化系统堆栈
将上下文压入系统堆栈，压栈顺序见KTrap_Frame内核堆栈框架
将参数从用户模式堆栈复制到内核堆栈，以上步骤在关中断下进行的，应为要用到KUser_Shared_Data
确定服务例程的入口地址，包括使用那个服务表，是Shadow SSDT还是SSDT
转入服务例程入口
[招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
