Wine 32-bit address space

[Nick Burns]

According to
    http://msdn2.microsoft.com/en-gb/library/aa366912.aspx

The range 3GB (0xC0000000) - 4GB (0xFFFFFFFF) is considered system memory 
and apps should not write here (not sure why you would want to read from 
there either).

But Wine tries to mmap this range (on Mac OSX at least)

I was wondering why this is?
Should this range just be left as it is? -- is there a reason to mmap this 
range?

Any ideas?

for reference -- this mmap is spurred from libs/wine/mmap.c:356 (mmap_init)

- Nick

[Alexandre Julliard]

"Nick Burns"  writes:
> The range 3GB (0xC0000000) - 4GB (0xFFFFFFFF) is considered system
> memory and apps should not write here (not sure why you would want to
> read from there either).
>
> But Wine tries to mmap this range (on Mac OSX at least)
>
> I was wondering why this is?
> Should this range just be left as it is? -- is there a reason to mmap
> this range?

Yes, it's to prevent things like builtin libraries from being mapped
there, since it's a range the Window apps don't expect to see.

[Nick Burns]

Ok that is understandable -- but if wine takes up the entire 4gb address 
space -- where are builtin libs supposed to live ((be mapped)/alloc to)?

(im assuming that opengl is a builtin lib -- in this context)

In my case If I let wine take up my entire address space -- libraries (like 
opengl) will get angry when it can no longer allocate memory (like for 
textures, bufer objects, contexts, various random temporary allocations, 
etc... )

Why not let builtin libs (like opengl) use that 3gb -> 4gb space (since wine 
does not use it)?

But maybe that would cause problems if builtin libs returned addresses in 
that space? (not sure)

- Nick
> From: Alexandre Julliard 
> To: "Nick Burns" 
> CC: [e-mail]
> Subject: Re: Wine 32-bit address space
> Date: Mon, 01 Jan 2007 11:29:51 +0100
>
> "Nick Burns"  writes:
> > The range 3GB (0xC0000000) - 4GB (0xFFFFFFFF) is considered system
> > memory and apps should not write here (not sure why you would want to
> > read from there either).
> >
> > But Wine tries to mmap this range (on Mac OSX at least)
> >
> > I was wondering why this is?
> > Should this range just be left as it is? -- is there a reason to mmap
> > this range?
>
> Yes, it's to prevent things like builtin libraries from being mapped
> there, since it's a range the Window apps don't expect to see.
>
> --
> Alexandre Julliard
> [e-mail]

[Alexandre Julliard]

"Nick Burns"  writes:
> Ok that is understandable -- but if wine takes up the entire 4gb
> address space -- where are builtin libs supposed to live ((be
> mapped)/alloc to)?

There is free space between 0x60000000 and 0x80000000.
> Why not let builtin libs (like opengl) use that 3gb -> 4gb space
> (since wine does not use it)?
>
> But maybe that would cause problems if builtin libs returned addresses
> in that space? (not sure)

Yes, it would.