[MPlayer-users] Re: Mplayer crashes with wmv-files

[Alex Eskin]

    This is not an athlon problem,  but a fedora problem.

   There is a bad interaction on Fedora between exec-shield, prelink,
   and anything which uses windows dll's (i.e. wine, but also 
   mplayer and xine). The immediate symptom I was seeing was a 
   segmentation fault when trying to play windows media 9 files 
   in mplayer.

   The cause of the problem is the following:

   The exec-shield patches in Fedora Core 1 also randomize the 
   loading addresses of the system libraries. Because of prelink, 
   this random assignment occurs during full-prelink time (which is 
   normally every two weeks). Also, to help combat ASCII buffer 
   overflow attacks, the libraries are packed as much as possible
   into the first megabyte. 

   Now mplayer wants to load windows dll's at virtual address 
   0x400000. If an important system library happens to be there, 
   you get a segmentation fault. Whether or not it works literally
   depends on the pahse of the moon :). 

   (This is not as much a problem as it used to be since mplayer
    now plays most formats natively, but it is still annoying). 

   There is currently no workaround which is local to mplayer. 
   The best one so far (which I found on codeweavers.com) is the
   the following:

   
   a) edit /etc/syconfig/prelink and change PRELINK_OPTS=-mR
         to PRELINK_OPTS="-mR --no-exec-shield"

   b) touch /var/lib/misc/prelink.force
   c) /etc/cron.daily/prelink 

  This relinks all the applications, and it takes
  quite a while. The undocumented --no-exec-shield option
  to /usr/sbin/prelink has the effect of randomizing
  the library locations starting at 0x40000000 (so you
  abandon the attempt to protect against ASCII overflows). 

  I hope a better solution will come along in the future. 


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