ExAllocatePool

The ExAllocatePool routine is obsolete, and is exported only for existing binaries. Use ExAllocatePoolWithTag instead.

ExAllocatePool allocates pool memory of the specified type and returns a pointer to the allocated block.

PVOID 
  ExAllocatePool(
    IN POOL_TYPE  PoolType,
    IN SIZE_T  NumberOfBytes
    );

Parameters

PoolType

Specifies the type of pool memory to allocate. For a description of the available pool memory types, see POOL_TYPE.

NumberOfBytes

Specifies the number of bytes to allocate.

Return Value

ExAllocatePool returns NULL if there is insufficient memory in the free pool to satisfy the request. Otherwise the routine returns a pointer to the allocated memory.

Headers

Declared in wdm.h and ntddk.h. Include wdm.h or ntddk.h.

Comments

This routine is used for the general pool allocation of memory.

If the NumberOfBytes requested is PAGE_SIZE or greater, a page-aligned buffer is allocated. Memory allocations of PAGE_SIZE or less do not cross page boundaries. Memory allocations of less than PAGE_SIZE are not necessarily page-aligned but are aligned on an 8-byte boundary.

A successful allocation requesting NumberOfBytes < PAGE_SIZE of nonpaged pool gives the caller exactly the number of requested bytes of memory. Any successful allocation that requests NumberOfBytes > PAGE_SIZE wastes all unused bytes on the last-allocated page.

If ExAllocatePool returns NULL, the caller should return the NTSTATUS value STATUS_INSUFFICIENT_RESOURCES or should delay processing to another point in time.

Callers of ExAllocatePool must be executing at IRQL <= DISPATCH_LEVEL. A caller executing at DISPATCH_LEVEL must specify a NonPagedXxx value for PoolType. A caller executing at IRQL < DISPATCH_LEVEL can specify any POOL_TYPE value.

See Also

ExAllocatePoolWithTag, ExFreePool