ReactOS系统NtReadFile函数的实现。

ReactOS系统NtReadFile函数的实现。

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NtReadFile()是windows的一个系统调用，内核中有一个叫NtReadFile的函数

NtReadFile函数的定义

NTSTATUS  WINAPI NtReadFile(HANDLE,HANDLE,PIO_APC_ROUTINE,PVOID,PIO_STATUS_BLOCK,PVOID,ULONG,PLARGE_INTEGER,PULONG);

上面的函数看起来很费解。
我们用另外一个函数来看

这里涉及到内核的快速调用的知识。
eax,0B7h：系统调用号：指向NtReadFile(xxxxxxxxx)函数
edx,7ffe0300h:系统调用函数的地址

这样之后就实现了。R3与R0的隔离

NtReadFile函数的实现

NTSTATUS
NTAPI
NtReadFile(IN HANDLE FileHandle,IN HANDLE Event OPTIONAL,IN PIO_APC_ROUTINE ApcRoutine OPTIONAL,IN PVOID ApcContext OPTIONAL,OUT PIO_STATUS_BLOCK IoStatusBlock,OUT PVOID Buffer,IN ULONG Length,IN PLARGE_INTEGER ByteOffset OPTIONAL,IN PULONG Key OPTIONAL)
{NTSTATUS Status = STATUS_SUCCESS;PFILE_OBJECT FileObject;PIRP Irp;PDEVICE_OBJECT DeviceObject;PIO_STACK_LOCATION StackPtr;KPROCESSOR_MODE PreviousMode = KeGetPreviousMode();PKEVENT EventObject = NULL;LARGE_INTEGER CapturedByteOffset;ULONG CapturedKey = 0;BOOLEAN Synchronous = FALSE;PMDL Mdl;PAGED_CODE();CapturedByteOffset.QuadPart = 0;IOTRACE(IO_API_DEBUG, "FileHandle: %p\n", FileHandle);/* Validate User-Mode Buffers */if(PreviousMode != KernelMode){_SEH_TRY{/* Probe the status block */ProbeForWriteIoStatusBlock(IoStatusBlock);/* Probe the read buffer */ProbeForWrite(Buffer, Length, 1);/* Check if we got a byte offset */if (ByteOffset){/* Capture and probe it */CapturedByteOffset = ProbeForReadLargeInteger(ByteOffset);}/* Capture and probe the key */if (Key) CapturedKey = ProbeForReadUlong(Key);}_SEH_HANDLE{/* Get the exception code */Status = _SEH_GetExceptionCode();}_SEH_END;/* Check for probe failure */if (!NT_SUCCESS(Status)) return Status;}else{/* Kernel mode: capture directly */if (ByteOffset) CapturedByteOffset = *ByteOffset;if (Key) CapturedKey = *Key;}/* Get File Object */Status = ObReferenceObjectByHandle(FileHandle,FILE_READ_DATA,IoFileObjectType,PreviousMode,(PVOID*)&FileObject,NULL);if (!NT_SUCCESS(Status)) return Status;/* Check for event */if (Event){/* Reference it */Status = ObReferenceObjectByHandle(Event,EVENT_MODIFY_STATE,ExEventObjectType,PreviousMode,(PVOID*)&EventObject,NULL);if (!NT_SUCCESS(Status)){/* Fail */ObDereferenceObject(FileObject);return Status;}/* Otherwise reset the event */KeClearEvent(EventObject);}/* Check if we should use Sync IO or not */if (FileObject->Flags & FO_SYNCHRONOUS_IO){/* Lock the file object */IopLockFileObject(FileObject);/* Check if we don't have a byte offset avilable */if (!(ByteOffset) ||((CapturedByteOffset.u.LowPart == FILE_USE_FILE_POINTER_POSITION) &&(CapturedByteOffset.u.HighPart == -1))){/* Use the Current Byte Offset instead */CapturedByteOffset = FileObject->CurrentByteOffset;}/* Rememer we are sync */Synchronous = TRUE;}else if (!(ByteOffset) &&!(FileObject->Flags & (FO_NAMED_PIPE | FO_MAILSLOT))){/* Otherwise, this was async I/O without a byte offset, so fail */if (EventObject) ObDereferenceObject(EventObject);ObDereferenceObject(FileObject);return STATUS_INVALID_PARAMETER;}/* Get the device object */DeviceObject = IoGetRelatedDeviceObject(FileObject);/* Clear the File Object's event */KeClearEvent(&FileObject->Event);/* Allocate the IRP */Irp = IoAllocateIrp(DeviceObject->StackSize, FALSE);if (!Irp) return IopCleanupFailedIrp(FileObject, NULL, NULL);/* Set the IRP */Irp->Tail.Overlay.OriginalFileObject = FileObject;Irp->Tail.Overlay.Thread = PsGetCurrentThread();Irp->RequestorMode = KernelMode;Irp->Overlay.AsynchronousParameters.UserApcRoutine = ApcRoutine;Irp->Overlay.AsynchronousParameters.UserApcContext = ApcContext;Irp->UserIosb = IoStatusBlock;Irp->UserEvent = EventObject;Irp->PendingReturned = FALSE;Irp->Cancel = FALSE;Irp->CancelRoutine = NULL;Irp->AssociatedIrp.SystemBuffer = NULL;Irp->MdlAddress = NULL;/* Set the Stack Data */StackPtr = IoGetNextIrpStackLocation(Irp);StackPtr->MajorFunction = IRP_MJ_READ;StackPtr->FileObject = FileObject;StackPtr->Parameters.Read.Key = CapturedKey;StackPtr->Parameters.Read.Length = Length;StackPtr->Parameters.Read.ByteOffset = CapturedByteOffset;/* Check if this is buffered I/O */if (DeviceObject->Flags & DO_BUFFERED_IO){/* Check if we have a buffer length */if (Length){/* Enter SEH */_SEH_TRY{/* Allocate a buffer */Irp->AssociatedIrp.SystemBuffer =ExAllocatePoolWithTag(NonPagedPool,Length,TAG_SYSB);}_SEH_HANDLE{/* Allocating failed, clean up */IopCleanupAfterException(FileObject, Irp, NULL, Event);Status = _SEH_GetExceptionCode();}_SEH_END;if (!NT_SUCCESS(Status)) return Status;/* Set the buffer and flags */Irp->UserBuffer = Buffer;Irp->Flags = (IRP_BUFFERED_IO |IRP_DEALLOCATE_BUFFER |IRP_INPUT_OPERATION);}else{/* Not reading anything */Irp->Flags = IRP_BUFFERED_IO | IRP_INPUT_OPERATION;}}else if (DeviceObject->Flags & DO_DIRECT_IO){/* Check if we have a buffer length */if (Length){/* Allocate an MDL */Mdl = IoAllocateMdl(Buffer, Length, FALSE, TRUE, Irp);MmProbeAndLockPages(Mdl, PreviousMode, IoWriteAccess);}/* No allocation flags */Irp->Flags = 0;}else{/* No allocation flags, and use the buffer directly */Irp->Flags = 0;Irp->UserBuffer = Buffer;}/* Now set the deferred read flags */Irp->Flags |= (IRP_READ_OPERATION | IRP_DEFER_IO_COMPLETION);
#if 0/* FIXME: VFAT SUCKS */if (FileObject->Flags & FO_NO_INTERMEDIATE_BUFFERING) Irp->Flags |= IRP_NOCACHE;
#endif/* Perform the call */return IopPerformSynchronousRequest(DeviceObject,Irp,FileObject,TRUE,PreviousMode,Synchronous,IopReadTransfer);
}

//从上面可以看出ReadFile函数是很大的，可以对文件，IO，事件等的处理