Created attachment 22322 [details] [review]
Patch to prevent Xorg from crashing

Overview:
  Moving a Xv window off the screen makes Xorg crash with SIGSEGV

Steps to reproduce:
  - play a film (probably in high resolution?) with mplayer -vo xv
  - move the Xvideo window leftwards so that parts of it are off the screen
  - Xorg crashes with SIGSEGV as soon as 1 pixel is off screen

System information:
  - FreeBSD 8.0-CURRENT on a Lenovo Thinkpad T400
  - Xorg 7.4 built from the FreeBSD ports system
  - Graphics adapter: Mobile Intel® GM45 Express Chipset, card=0x211217aa chip=0x2a428086 rev=0x07
  - xorg.conf, Xorg.0.log attached
  - more information on request

Analysis:

Commit d5a80e1e3ab5724d34b20f9ee6f830efd0f5b076 introduced two shortcuts with memcpy when srcPitch2 == dstPitch. These are the points where Xorg 7.4 from the FreeBSD ports crashes. Even if one is fixed, the other crashes.

Could it be that these memcpy()s are not the same as the "for() memcpy;" loop even if srcPitch2 == dstPitch? Or just in this special case when cropping the left part of the video window?

There is another similar shortcut in the code. This one could also be problematic.

Workaround: 

See attached patch.


Could somebody with more insight in the driver look at this?