Mmap/malloc redirection (bug 13335, seems to affect 3D games mainly)

Paul TBBle Hampson Paul.Hampson at
Wed Apr 29 10:46:44 CDT 2009

Bug 13335 [1] is basically "OpenGL games crash or run slow".

There's two symptoms here, and they're to do with proprietary video

When the nVidia driver fails to mmap stuff from /dev/nvidia0, it starts
failing OpenGL commands with GL_OUT_OF_MEMORY.

When the FireGL driver fails to mmap or malloc (I don't know which), it
falls back to indrect rendering.

The problem in both cases is because Wine mmaps most of the 32-bit
memory space for itself and then parcels this back out through HeapAlloc
and related methods.

When the GL libraries calls mmap and malloc themselves, for quite large
blocks of memory, they fail because there's nowhere in the address space
for those large blocks of memory to go.

The first linked patch [2] in bug 13335 fixes this by redirecting mmap calls
into ntdll which unmaps a block of address space, and performs the mmap
into that address space, effectively handing that address space over to
the library for the duration of the mmap's existence.

I can't claim credit for that, I merely took Thunderbird's
forward-ported version of Alexandre's original patch and forward-ported
it further to 1.1.19.

The second linked patch [3] simply redirects malloc and related calls to
RtlAllocateHeap, rather like the msvcrt malloc-type calls are handled.

The latter's almost certainly in the wrong place in ntdll, but it keeps
ntdll from needing two copies of the pthread_functions structure.

The bug's staring to accumulate some feedback that this helps for games
that otherwise tend to crash after playing for a little while, and I've
not had any luck catching people on IRC to look over the patches, so I'm
wondering if anyone would like to provide feedback on these patches, as
to whether they are the right approach, and if there are things that
could be handled more cleanly.


Paul "TBBle" Hampson, B.Sc, LPI, MCSE
Very-later-year Asian Studies student, ANU
The Boss, Bubblesworth Pty Ltd (ABN: 51 095 284 361)
Paul.Hampson at

Of course Pacman didn't influence us as kids. If it did,
we'd be running around in darkened rooms, popping pills and
listening to repetitive music.
 -- Marcus Brigstocke

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