ExAllocateFromPagedLookasideList function (wdm.h)

Article
02/22/2024

The ExAllocateFromPagedLookasideList routine returns a pointer to a paged entry from the given lookaside list, or it returns a pointer to a newly allocated paged entry.

Syntax

PVOID ExAllocateFromPagedLookasideList(
  [in, out] PPAGED_LOOKASIDE_LIST Lookaside
);

Parameters

[in, out] Lookaside

A pointer to the PAGED_LOOKASIDE_LIST structure for the lookaside list, which the caller already initialized with ExInitializePagedLookasideList.

Return value

ExAllocateFromPagedLookasideList returns a pointer to an entry if one can be allocated. Otherwise, it returns NULL.

Remarks

Caution

Starting in Windows 11, version 22H2, this function changed from inline to exported. As a result, if you build your driver targeting the latest version of Windows, it will fail to load in older OS versions. To change the target OS version in Visual Studio, select Configuration Properties->Driver Settings->General.

If the given lookaside list is not empty, ExAllocateFromPagedLookasideList removes the first entry from the list and returns a pointer to this entry. Otherwise, ExAllocateFromPagedLookasideList either calls the Allocate routine specified at list initialization or ExAllocatePoolWithTag to return an entry pointer.

The caller can then set up the returned entry with any caller-determined data. The caller should release each entry with ExFreeToPagedLookasideList when it is no longer in use.

Because the entries in a paged lookaside list are allocated from pageable memory, they must not be accessed at an IRQL >= DISPATCH_LEVEL. You can use ExAllocateFromNPagedLookasideList to create a lookaside list with non-pageable entries.

On Windows 2000, drivers must use the -D_WIN2K_COMPAT_SLIST_USAGE switch to successfully link code that uses ExAllocateFromPagedLookasideList.

For more information, see Using Lookaside Lists.

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows 2000.
Target Platform	Universal
Header	wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	<= APC_LEVEL