gnu: xorg: Add patch to fix sis driver crashes.

* gnu/packages/patches/xf86-video-sis-fix-exa-crash.patch: New file.
* gnu/packages/xorg.scm (xf86-video-sis): Use it.
* gnu-system.am (dist_patch_DATA): Add it.

gnu-system.am

@@ -562,6 +562,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/xf86-video-openchrome-glibc-2.20.patch	\
   gnu/packages/patches/xf86-video-r128-glibc-2.20.patch		\
   gnu/packages/patches/xf86-video-siliconmotion-remove-mibstore.patch \
+  gnu/packages/patches/xf86-video-sis-fix-exa-crash.patch	\
   gnu/packages/patches/xf86-video-sis-update-api.patch		\
   gnu/packages/patches/xf86-video-tdfx-remove-mibstore.patch	\
   gnu/packages/patches/xf86-video-tga-remove-mibstore.patch	\

gnu/packages/patches/xf86-video-sis-fix-exa-crash.patch

@@ -0,0 +1,45 @@
+Fix X server crash when sis driver is used with EXA acceleration.
+
+Source: http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/trusty/xserver-xorg-video-sis/trusty/revision/24/debian/patches/fix-exa-crash.diff
+
+The patch was originally proposed by nihui:
+https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-sis/+bug/1066464/comments/13
+
+--- a/src/sis310_accel.c
++++ b/src/sis310_accel.c
+@@ -1874,7 +1874,7 @@
+ {
+ 	ScrnInfoPtr pScrn = xf86ScreenToScrn(pDst->drawable.pScreen);
+ 	SISPtr pSiS = SISPTR(pScrn);
+-	unsigned char *dst = pDst->devPrivate.ptr;
++	unsigned char *dst = ((unsigned char *) pSiS->FbBase) + exaGetPixmapOffset(pDst);
+ 	int dst_pitch = exaGetPixmapPitch(pDst);
+ 
+ 	(pSiS->SyncAccel)(pScrn);
+@@ -1882,7 +1882,7 @@
+ 	if(pDst->drawable.bitsPerPixel < 8)
+ 	   return FALSE;
+ 
+-	dst += (x * pDst->drawable.bitsPerPixel / 8) + (y * src_pitch);
++	dst += (x * pDst->drawable.bitsPerPixel / 8) + (y * dst_pitch);
+ 	while(h--) {
+ 	   SiSMemCopyToVideoRam(pSiS, dst, (unsigned char *)src,
+ 				(w * pDst->drawable.bitsPerPixel / 8));
+@@ -1953,7 +1953,7 @@
+ {
+ 	ScrnInfoPtr pScrn = xf86ScreenToScrn(pSrc->drawable.pScreen);
+ 	SISPtr pSiS = SISPTR(pScrn);
+-	unsigned char *src = pSrc->devPrivate.ptr;
++	unsigned char *src = ((unsigned char *) pSiS->FbBase) + exaGetPixmapOffset(pSrc);
+ 	int src_pitch = exaGetPixmapPitch(pSrc);
+ 	int size = src_pitch < dst_pitch ? src_pitch : dst_pitch;
+ 
+@@ -1964,7 +1964,7 @@
+ 
+ 	src += (x * pSrc->drawable.bitsPerPixel / 8) + (y * src_pitch);
+ 	while(h--) {
+-	   SiSMemCopyFromVideoRam(pSiS, (unsigned char *)dst, src, size);
++	   SiSMemCopyFromVideoRam(pSiS, (unsigned char *)dst, src, (w * pSrc->drawable.bitsPerPixel / 8));
+ 	   src += src_pitch;
+ 	   dst += dst_pitch;
+ 	}

gnu/packages/xorg.scm

@@ -2932,7 +2932,8 @@ graphics cards.")
         (sha256
           (base32
            "1l0w84x39gq4y9j81dny9r6rma1xkqvxpsavpkd8h7h8panbcbmy"))
-        (patches (list (search-patch "xf86-video-sis-update-api.patch")))))
+        (patches (list (search-patch "xf86-video-sis-update-api.patch")
+                       (search-patch "xf86-video-sis-fix-exa-crash.patch")))))
     (build-system gnu-build-system)
     (inputs `(("mesa" ,mesa)
               ("xf86dgaproto" ,xf86dgaproto)