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FsRtlAllocatePoolWithTag macro (ntifs.h)

  • Article

The FsRtlAllocatePoolWithTag routine allocates pool memory.

Syntax

void FsRtlAllocatePoolWithTag(
  [in]  PoolType,
  [in]  NumberOfBytes,
  [in]  Tag
);

Parameters

[in] PoolType

Type of pool to allocate. One of the following:

  • NonPagedPool
  • PagedPool
  • NonPagedPoolCacheAligned
  • PagedPoolCacheAligned

The NonPagedPoolMustSucceed and NonPagedPoolCacheAlignedMustS pool types are obsolete and should no longer be used.

[in] NumberOfBytes

Number of bytes to allocate. This parameter is required and cannot be zero.

[in] Tag

Specifies the pool tag for the allocated memory. Drivers normally specify the pool tag as a string of one to four 7-bit ASCII characters, delimited by single quotation marks (for example, 'abcd'). This parameter is required and cannot be zero.

Return value

None

Remarks

If a pool allocation failure occurs, FsRtlAllocatePoolWithTag raises a STATUS_INSUFFICIENT_RESOURCES exception. To gain control if this pool allocation failure occurs, the driver should wrap the call to FsRtlAllocatePoolWithTag in a try-except or try-finally statement.

The system associates the pool tag specified by the Tag parameter with the allocated buffer. Programming tools, such as the Windows Debugger (WinDbg), can display the pool tag associated with each allocated buffer. The value of the pool tag is normally displayed in reversed order. For example, if a caller passes 'Fred' as the value of the Tag parameter, this value would appear as 'derF' if pool is dumped or when tracking pool usage in the debugger.

For more information about memory management, see Memory Management.

Memory that FsRtlAllocatePoolWithTag allocates is uninitialized. A kernel-mode driver must first zero this memory if it is going to make it visible to user-mode software (to avoid leaking potentially privileged contents).

Callers of FsRtlAllocatePoolWithTag must be running at IRQL <= DISPATCH_LEVEL. A caller at DISPATCH_LEVEL must specify a NonPagedXxx PoolType. Otherwise, the caller must be running at IRQL <= APC_LEVEL.

Requirements

Requirement Value
Target Platform Universal
Header ntifs.h (include Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
IRQL <= DISPATCH_LEVEL (see Remarks section)

See also

ExAllocatePoolWithTag

ExFreePool