[X2Go-Commits] [nx-libs] 05/51: fb: Fix memcpy abuse

[git-admin at x2go.org]

This is an automated email from the git hooks/post-receive script.

x2go pushed a commit to branch master
in repository nx-libs.

commit 020ef045e0df09bc2f664d8d6e4b6600da53b41a
Author: Ulrich Sibiller <uli42 at gmx.de>
Date:   Tue Dec 18 21:32:37 2018 +0100

    fb: Fix memcpy abuse
    
    Fixes ArcticaProject/nx-libs#750
    
    Backport of this commit:
    
    commit e32cc0b4c85c78cd8743a6e1680dcc79054b57ce
    Author: Adam Jackson <ajax at redhat.com>
    Date:   Thu Apr 21 16:37:11 2011 -0400
    
        fb: Fix memcpy abuse
    
        The memcpy fast path implicitly assumes that the copy walks
        left-to-right.  That's not something memcpy guarantees, and newer glibc
        on some processors will indeed break that assumption.  Since we walk a
        line at a time, check the source and destination against the width of
        the blit to determine whether we can be sloppy enough to allow memcpy.
        (Having done this, we can remove the check for !reverse as well.)
    
        On an Intel Core i7-2630QM with an NVIDIA GeForce GTX 460M running in
        NoAccel, the broken code and various fixes for -copywinwin{10,100,500}
        gives (edited to fit in 80 columns):
    
        1: Disable the fastpath entirely
        2: Replace memcpy with memmove
        3: This fix
        4: The code before this fix
    
          1            2                 3                 4           Operation
          ------   ---------------   ---------------   ---------------   ------------
          258000   269000 (  1.04)   544000 (  2.11)   552000 (  2.14)   Copy 10x10
           21300    23000 (  1.08)    43700 (  2.05)    47100 (  2.21)   Copy 100x100
             960      962 (  1.00)     1990 (  2.09)     1990 (  2.07)   Copy 500x500
    
        So it's a modest performance hit, but correctness demands it, and it's
        probably worth keeping the 2x speedup from having the fast path in the
        first place.
    
        Signed-off-by: Adam Jackson <ajax at redhat.com>
        Signed-off-by: Keith Packard <keithp at keithp.com>
---
 nx-X11/programs/Xserver/fb/fbblt.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/nx-X11/programs/Xserver/fb/fbblt.c b/nx-X11/programs/Xserver/fb/fbblt.c
index e820a85..acec23b 100644
--- a/nx-X11/programs/Xserver/fb/fbblt.c
+++ b/nx-X11/programs/Xserver/fb/fbblt.c
@@ -67,6 +67,7 @@ fbBlt (FbBits   *srcLine,
     int	    n, nmiddle;
     Bool    destInvarient;
     int	    startbyte, endbyte;
+    int     careful;
     FbDeclareMergeRop ();
 
 #ifdef FB_24BIT
@@ -78,7 +79,11 @@ fbBlt (FbBits   *srcLine,
     }
 #endif
 
-    if (alu == GXcopy && pm == FB_ALLONES && !reverse &&
+    careful = !((srcLine < dstLine && srcLine + width * (bpp>>3) > dstLine) ||
+                (dstLine < srcLine && dstLine + width * (bpp>>3) > srcLine)) ||
+              (bpp & 7);
+
+    if (alu == GXcopy && pm == FB_ALLONES && !careful &&
             !(srcX & 7) && !(dstX & 7) && !(width & 7)) {
         int i;
         CARD8 *src = (CARD8 *) srcLine;

--
Alioth's /home/x2go-admin/maintenancescripts/git/hooks/post-receive-email on /srv/git/code.x2go.org/nx-libs.git