Re: Towards a working "wine". [long]

On 6/17/05, Maxim Sobolev <sobomax_at_portaone.com> wrote:
> Peter Edwards wrote:
> > Y'all,
> >
> > I wanted to run a substantial windows app using "wine", and failed
> > miserably. Looking around, it appears to be an acknowledged fact
> > that wine is borked on FreeBSD, so I did some hacking about.
> >
> > The problems I found are centered around address space allocation:
> > Wine is inevitably somewhat sensitive to address space layout,
> > seeing as it has to present the Win32 binaries with a reasonably
> > familiar environment. (All this assumes standard kernel, etc. Fixed
> > addresses are the order of the day)
> >
> > Problem 1:
> >
> > When starting up, Wine needs to mmap stuff at address 0x80000000,
> > but does so without using MAP_FIXED: I think the intention is that
> > the code involved should be "best effort" to map to the hint address
> > supplied to mmap(), rather than an all-or-nothing thing.
> >
> > FreeBSD's mmap sees this as an address in the data segment (see
> > problem 2 below), and shifts the hint along to an address past
> > there.  There appears to be a MAP_TRYFIXED flag that wine uses on
> > some systems that affords the hint more weight, which is pretty
> > trivial to implement (see wine_mmap.txt).  That was enough to get
> > my app running, but not for long.
> 
> Well, there is really no point of adding another MAP_TRYFIXED flag,
> since wine can call mmap(2) with MAP_FIXED and then if that fails try to
> call mmap(2) without it and deal with consequences. This will provide
> the same functionality but you won't get dependency on particular
> FreeBSD version to get MAP_TRYFIXED define.
> 

Nope: MAP_FIXED will unconditionally overwrite any existing mapping at
the requested address.