ZwMapViewOfSectionEx function (wdm.h)

Article
05/22/2024

The ZwMapViewOfSectionEx routine maps a view of a section into the virtual address space of a subject process.

Syntax

NTSYSAPI NTSTATUS ZwMapViewOfSectionEx(
  [in]                HANDLE                  SectionHandle,
  [in]                HANDLE                  ProcessHandle,
  [in, out]           PVOID                   *BaseAddress,
  [in, out, optional] PLARGE_INTEGER          SectionOffset,
  [in, out]           PSIZE_T                 ViewSize,
  [in]                ULONG                   AllocationType,
  [in]                ULONG                   PageProtection,
  [in, out, optional] PMEM_EXTENDED_PARAMETER ExtendedParameters,
  [in]                ULONG                   ExtendedParameterCount
);

Parameters

[in] SectionHandle

Handle to a section object. This handle is created by a successful call to ZwCreateSection or ZwOpenSection.

[in] ProcessHandle

Handle to the object that represents the process that the view should be mapped into. Use the ZwCurrentProcess macro to specify the current process. The handle must have been opened with PROCESS_VM_OPERATION access.

[in, out] BaseAddress

Pointer to a variable that receives the base address of the view. If the value of this parameter is not NULL, the view is allocated starting at the specified virtual address rounded down to the next 64-kilobyte address boundary.

[in, out, optional] SectionOffset

A pointer to a variable that receives the offset, in bytes, from the beginning of the section to the view. If this pointer is not NULL, the offset is rounded down to the next allocation-granularity size boundary.

[in, out] ViewSize

A pointer to a SIZE_T variable. If the initial value of this variable is zero, ZwMapViewOfSectionEx maps a view of the section that starts at SectionOffset and continues to the end of the section. Otherwise, the initial value specifies the view's size, in bytes. ZwMapViewOfSectionEx always rounds this value up to the nearest multiple of PAGE_SIZE before mapping the view.

On return, the value receives the actual size, in bytes, of the view.

[in] AllocationType

Specifies a set of flags that describes the type of allocation to be performed for the specified region of pages. The valid flags are MEM_RESERVE, MEM_TOP_DOWN, MEM_LARGE_PAGES, MEM_DIFFERENT_IMAGE_BASE_OK and MEM_REPLACE_PLACEHOLDER. Although MEM_COMMIT is not allowed, it is implied unless MEM_RESERVE is specified. For more information about the MEM_XXX flags, see the description of the VirtualAlloc and MapViewOfFile3 routines.

[in] PageProtection

Specifies the page protection to be applied to the mapped view.

For section objects created with the SEC_IMAGE attribute, the PageProtection parameter has no effect, and can be set to any valid value such as PAGE_READONLY.

For section objects created with the SEC_IMAGE_NO_EXECUTE attribute, the PageProtection value must be set to PAGE_READONLY.

For non-image sections, the value of the PageProtection parameter must be compatible with the section's page protection that was specified when ZwCreateSection was called.

ZwMapViewOfSectionEx always sets the cache type of the mapped pages to match the cache type supplied when the section object was created. For example, if ZwCreateSection was called with the SEC_NOCACHE flag, ZwMapViewOfSectionEx will map the pages uncached, regardless of whether the PageProtection parameter includes the PAGE_NOCACHE flag or not.

[in, out, optional] ExtendedParameters

An optional pointer to one or more extended parameters of type MEM_EXTENDED_PARAMETER. For more information about extended parameters, see the description of the MapViewOfFile3 routine.

[in] ExtendedParameterCount

Specifies the number of elements in the ExtendedParameters array.

Return value

ZwMapViewOfSectionEx returns an NTSTATUS value. Possible return values include the following:

Return code	Description
STATUS_SUCCESS	The routine successfully performed the requested operation.
STATUS_CONFLICTING_ADDRESSES	The specified address range conflicts with a range that is already reserved.
STATUS_INVALID_PAGE_PROTECTION	The value specified for the PageProtection parameter is invalid.
STATUS_SECTION_PROTECTION	The value specified for the PageProtection parameter is incompatible with the page protection specified when the section was created.

Remarks

Several different views of a section can be concurrently mapped into the virtual address space of one or more processes.

Do not use ZwMapViewOfSectionEx to map a memory range from \Device\PhysicalMemory into user mode, unless your driver has directly allocated the memory range through MmAllocatePagesForMdlEx or another method guaranteeing that no other system component has mapped the same memory range with a different MEMORY_CACHING_TYPE value.

User applications cannot access \Device\PhysicalMemory directly starting with Windows Server 2003 with Service Pack 1 (SP1) and can access it only if the driver passes a handle to the application.

For more information about section objects, see Section Objects and Views.

If the call to this function occurs in user mode, you should use the name "NtMapViewOfSectionEx" instead of "ZwMapViewOfSectionEx".

For calls from kernel-mode drivers, the NtXxx and ZwXxx versions of a Windows Native System Services routine can behave differently in the way that they handle and interpret input parameters. For more information about the relationship between the NtXxx and ZwXxx versions of a routine, see Using Nt and Zw Versions of the Native System Services Routines.

Requirements

Requirement	Value
Minimum supported client	Windows 11, version 24H2
Header	wdm.h

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