#ifndef _NTRTL_H

typedef _Function_class_(QUERY_VIRTUAL_MEMORY_CALLBACK)
NTSTATUS NTAPI QUERY_VIRTUAL_MEMORY_CALLBACK(
    _Inout_ HANDLE CallbackContext,
    _In_ HANDLE ProcessHandle,
    _In_opt_ PVOID BaseAddress,
    _In_ HEAP_MEMORY_INFO_CLASS MemoryInformationClass,
    _Out_writes_bytes_(MemoryInformationLength) PVOID MemoryInformation,
    _In_ SIZE_T MemoryInformationLength,
    _Out_opt_ PSIZE_T ReturnLength
    );

#endif
View code on GitHub

// ntifs.h

QUERY_VIRTUAL_MEMORY_CALLBACK QueryVirtualMemoryCallback;

NTSTATUS QueryVirtualMemoryCallback(
  HANDLE CallbackContext,
  HANDLE ProcessHandle,
  PVOID BaseAddress,
  HEAP_MEMORY_INFO_CLASS MemoryInformationClass,
  PVOID MemoryInformation,
  SIZE_T MemoryInformationLength,
  PSIZE_T ReturnLength
)
{...}
View the official Windows Driver Kit DDI reference