FltCreateSectionForDataScan function

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The FltCreateSectionForDataScan routine creates a section object for a file. The filter manager can optionally synchronize I/O with the section created.

Syntax

NTSTATUS FLTAPI FltCreateSectionForDataScan(
  PFLT_INSTANCE      Instance,
  PFILE_OBJECT       FileObject,
  PFLT_CONTEXT       SectionContext,
  ACCESS_MASK        DesiredAccess,
  POBJECT_ATTRIBUTES ObjectAttributes,
  PLARGE_INTEGER     MaximumSize,
  ULONG              SectionPageProtection,
  ULONG              AllocationAttributes,
  ULONG              Flags,
  PHANDLE            SectionHandle,
  PVOID              *SectionObject,
  PLARGE_INTEGER     SectionFileSize
);

Parameters

Instance

The opaque instance pointer for the minifilter driver instance whose context is to be retrieved.

FileObject

The file object for an open file. The section object will be backed by the specified file. This parameter is required and cannot be NULL.

SectionContext

A pointer to a previously allocated section context.

DesiredAccess

The type of access for the section object as one or more of the following ACCESS_MASK flags.

DesiredAccess flag Allows caller to
SECTION_MAP_READ Read views of the section.
SECTION_MAP_WRITE Write views of the section.
SECTION_QUERY Query the section object for information about the section. Drivers should set this flag.
SECTION_ALL_ACCESS All actions defined by the previous flags as well as that defined by STANDARD_RIGHTS_REQUIRED. (For more information about STANDARD_RIGHTS_REQUIRED, see ACCESS_MASK.)

ObjectAttributes

A pointer to an OBJECT_ATTRIBUTES structure that specifies the object name and other attributes. Use the InitializeObjectAttributes macro to initialize this structure. Because FltCreateSectionForDataScan inserts this object into the process handle table, the caller must specify the OBJ_KERNEL_HANDLE attribute when it calls InitializeObjectAttributes.

MaximumSize

This parameter is reserved for future use.

SectionPageProtection

The protection to place on each page in the section. Specify one of the following values. This parameter is required and cannot be zero.

Flag Meaning
PAGE_READONLY Enables read-only access to the committed region of pages. An attempt to write to the committed region results in an access violation. If the system differentiates between read-only access and execute access, an attempt to execute code in the committed region results in an access violation.
PAGE_READWRITE Enables both read and write access to the committed region of pages.

AllocationAttributes

Bitmasks of the SEC_XXX flags determine the allocation attributes of the section. Specify one or more of the following values. This parameter is required and cannot be zero.

Flag Meaning
SEC_COMMIT Allocates physical storage in memory or in the paging file on disk for all pages of a section. This is the default setting. Note that this flag is required and cannot be omitted.
SEC_FILE The file specified by the FileObject parameter is a mapped file.

Flags

This parameter is reserved for future use.

SectionHandle

A pointer to a caller-allocated variable that receives an opaque handle to the section handle.

SectionObject

A pointer to a caller-allocated variable that receives an opaque pointer to the section object.

SectionFileSize

A pointer to a caller-allocated variable that receives the size, in bytes, of the file at the time the section object was created. This parameter is optional and can be NULL.

Return value

FltCreateSectionForDataScan returns STATUS_SUCCESS or an appropriate NTSTATUS value, such as one of the following.

Return code Description
STATUS_END_OF_FILE
The size of the file specified by the FileObject parameter is zero.
STATUS_FILE_LOCK_CONFLICT
The file specified by the FileObject parameter is locked.
STATUS_INSUFFICIENT_RESOURCES
FltCreateSectionForDataScan encountered a pool allocation failure.
STATUS_INVALID_FILE_FOR_SECTION
The file specified by the FileObject parameter does not support sections.
STATUS_INVALID_PARAMETER
The minifilter is not registered.
STATUS_INVALID_PARAMETER_8
The value specified for the SectionPageProtection parameter is invalid.
STATUS_INVALID_PARAMETER_9
The caller specified an invalid value for the AllocationAttributes parameter.
STATUS_NOT_SUPPORTED
The volume attached to this instance does not support section contexts.
STATUS_PRIVILEGE_NOT_HELD

The caller did not have the required privileges to create a section object with the access specified in the DesiredAccess parameter.

STATUS_FILE_IS_A_DIRECTORY

The file specified by the FileObject parameter is a directory.

STATUS_FLT_CONTEXT_ALREADY_DEFINED
The filter instance specified by Instance already has an open section for the stream. Only one section per stream, and therefore, per instance is supported.

Remarks

Prior to calling FltCreateSectionForDataScan, a minifilter must first register its volume for data scanning by calling FltRegisterForDataScan. As with other filter context elements, SectionContext is first allocated with FltAllocateContext.

Certain situations can occur where holding a section open is incompatible with current file I/O. In particular, file I/O that triggers a cache purge can cause cache incoherency if the cache purge is prevented because of an open section. A minifilter can provide an optional callback routine for notifications of these events. The minifilter driver implements a PFLT_SECTION_CONFLICT_NOTIFICATION_CALLBACK to receive these notifications. Conflict notifications are enabled if the SectionNotificationCallback member of FLT_REGISTRATION is set to this callback routine when the minifilter is registered. When a notification is received, the section can be closed to allow the conflicting I/O operation to continue.

Note  A section notification callback may occur before FltCreateSectionForDataScan returns. A minifilter must be able to receive the callback and handle the case where SectionHandle and SectionObject are not yet valid.
 
When the section object created by this routine is no longer necessary, be sure to close the section object's handle (SectionHandle) by calling the ZwClose routine and dereference the section object itself (SectionObject) by calling the ObDereferenceObject routine.

For overview information on creating mapped sections and views of memory, see Section Objects and Views. Also, see the documentation for the CreateFileMapping routine in the Microsoft Windows SDK.

Important  

Minifilters must not explicitly delete a section context passed to FltCreateSectionForDataScan. Do not call FltDeleteContext after a section context is passed to FltCreateSectionForDataScan. A section context is deallocated and removed from a stream by calling FltCloseSectionForDataScan in this case.

In general, sections should be created as read-only. In particular, if a read-only file is in a transaction and a minifilter does not create a read-only section, a write to the section is discarded and is not included as part of the transaction.

 

Requirements

   
Minimum supported client The FltCreateSectionForDataScan routine is available starting with Windows 8.
Target Platform Universal
Header fltkernel.h (include Fltkernel.h)
Library FltMgr.lib
IRQL <= APC_LEVEL