WINE vs. FreeBSD

[John Baldwin]

On Monday 24 July 2006 21:58, Tijl Coosemans wrote:
> On Monday 24 July 2006 18:49, Daniel Eischen wrote:
> > On Mon, 24 Jul 2006, Tijl Coosemans wrote:
> > > On Monday 24 July 2006 17:39, Daniel Eischen wrote:
> > >> On Mon, 24 Jul 2006, Tijl Coosemans wrote:
> > >>> I've attached two patches that accomplish this, but this seems to
> > >>> trigger other problems, so use at your own risk. If you want to
> > >>> try them, place them in the port's files/ directory and add a
> > >>> line containing "USE_AUTOTOOLS= autoconf:259" to the Makefile.
> > >>> This seems to break wine+libpthread, so I've also changed the
> > >>> port to use libthr instead.
> > >>>
> > >>> For the libpthread experts, I haven't investigated that much
> > >>> further yet, but libpthread seems to fail in create_stack() from
> > >>> _pthread_create() from _thr_start_sig_daemon().
> > >>
> > >> See my response to this in a previous reply to this thread. 
> > >> libthr and libpthread use LDT's for TLS.  WINE is stomping on them
> > >> because it doesn't properly create LDTs.  This is not a problem
> > >> with either of the thread libraries and this issue has been known
> > >> ever since we implemented TLS years ago.
> > >
> > > And as I stated later on in that thread, I don't see where
> > > libpthread and libthr still use LDT entries. As far as I understand
> > > the code, instead of using an LDT entry per thread (as it sure used
> > > to be), only one single GDT entry is used whose base address is
> > > updated during a context switch. Looking at the cvs history, it has
> > > been working like this since a couple commits of Peter Wemm about a
> > > year ago.
> > >
> > > And if nothing but Wine uses the LDT, Wine's static allocation of
> > > LDT entries can't be the problem.
> >
> > Look, we use %gs for TLS, period.  Go see
> > libpthread/arch/i386/i386/pthread_md.c for how libpthread does it. 
> > TLS would not work without setting aside a register for the threads
> > library (and rtld) to use.
> 
> Aaarrrrgghhh :)
> 
> What you say is true of course, but %gs points to a GDT entry, not LDT. 
> libpthread and libthr no longer use LDT entries...
> 
> There would be a problem of course if Wine or Windows programs 
> change %gs. Wine does seem to touch %gs but I've never actually seen it 
> change. It's always 0x001B, which is the correct value (GUGS_SEL).
> 
> However, Wine/Windows uses %fs for TLS and it appears that the FreeBSD 
> kernel doesn't preserve it. It always ends up pointing to GUDATA_SEL.

The kernel should preserve %fs across syscalls, traps, and faults.  Can you 
point to a specific case where %fs is not preserved?  It sounds like %fs is 
never set to a value in Wine.

-- 
John Baldwin