Undocumented Win32k function: EngAllocSectionMem

Hello.
In looking at the imports of some display drivers and the exports of
win32k.sys, I came across EngAllocSectionMem / EngFreeSectionMem. Has
anyone used these functions, and if so, what are the benefits of using them
instead of EngAllocMem / EngFreeMem? The function takes arguments similar
to EngAllocMem, but apparently calls MmCreateSection to allocate the
memory, and then calls MmMapViewInSessionSpace on the allocated memory…
And the DDK docs state that MmMapViewInSessionSpace should only be used by
the OS, so that makes me even more curious…
Any ideas why would this be preferable over calling EngAllocMem, which
uses the ExAllocatePool* routines, or what benefits ‘section’ memory has
over plain old pool memory??? (or for that matter, what is the concept
behind ‘section memory’)…
I can’t find them in the DDK docs anywhere, so I’m assuming that they’re
undocumented… but I’m curious nonetheless…

Thanks,
sean


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