[PATCH] Support for game DRM which overwrite the GS segment selector

[Alessandro Pignotti]

Il giorno sab, 02/02/2013 alle 12.10 +0100, Austin English ha scritto:
> On Jan 31, 2013 8:15 AM, "Alessandro Pignotti"
> <alexpigna.dev at gmail.com> wrote:
> >
> > Hi again,
> >
> > I've quickly implemented the aforementioned idea of fixing the
> segment
> > in the segfault handler when needed. I'm attaching my proposed
> patch.
> >
> > Alessandro
> >
> > Il giorno mer, 30/01/2013 alle 16.44 +0100, Alessandro Pignotti ha
> > scritto:
> > > Hi everyone,
> > >
> > > I'm trying to get a specific game which employs a seemingly custom
> > > protection scheme to work. The DRM does various bad things as
> usual, but
> > > a very bad one is manipulating to GS segment selector and setting
> it to
> > > a NULL segment. The GS segment is used by libc though in various
> ways
> > > (stack protection and syscall support, and probably others).
> > >
> > > I managed to get the activation procedure to go further and
> further by
> > > enclosing each offending syscall using the following 2 macros.
> > >
> > > #define SAFE_GS_START \
> > >     do { \
> > >         wine_set_gs(ntdll_get_thread_data()->gs); \
> > >         do
> > >
> > > #define SAFE_GS_END \
> > >         while(0); \
> > >     } while(0)
> > >
> > > Still, this method is very cumbersome since system calls happens
> in many
> > > places even outside of ntdll. Fixing the GS is also needed to
> support
> > > sigsetjmp which is used by wine's exception handling.
> > >
> > > I'd like to ask for feedback about what would be a sane way of
> > > supporting this application. A possible solution would be to
> modify
> > > wine's segfault handler to check if the instruction has a GS
> prefix
> > > (0x65 IIRC) and try to execute the instruction again after fixing
> the
> > > GS.
> > >
> > > Please keep me in CC since I'm not subscribed to the ML.
> > >
> > > Regards,
> > > Alessandro Pignotti
> 
> Out of curiosity, what game is this? What protection does Protection
> ID show it uses?
> 
It's report as StarForce 32 Bit v5.70.040.000. The game is 'Of Orcs And
Men', the problem is also reported in wine forums

http://forum.winehq.org/viewtopic.php?f=2&t=17609

Alessandro