[PATCH] fbcon: Console Rotation - Fix wrong shift calculation

The shift value (amount to shift the bitmap so first pixel starts at
origin(0,0)) is incorrect.  This causes corrupted characters or a kernel crash
if fontwidth is not divisible by 8 at 270 degrees, or fontheight not divisible
by 8 at 180 degrees.

Report and part of the fix contributed by Knut Petersen.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/video/console/fbcon_rotate.h b/drivers/video/console/fbcon_rotate.h
index 90c6720..e504fbf 100644 (file)
--- a/drivers/video/console/fbcon_rotate.h
+++ b/drivers/video/console/fbcon_rotate.h
@@ -49,7 +49,7 @@ static inline void pattern_set_bit(u32 x, u32 y, u32 pitch, char *pat)
 static inline void rotate_ud(const char *in, char *out, u32 width, u32 height)
 {
        int i, j;
-       int shift = width % 8;
+       int shift = (8 - (width % 8)) & 7;
 
        width = (width + 7) & ~7;
 
@@ -85,7 +85,7 @@ static inline void rotate_cw(const char *in, char *out, u32 width, u32 height)
 static inline void rotate_ccw(const char *in, char *out, u32 width, u32 height)
 {
        int i, j, h = height, w = width;
-       int shift = width % 8;
+       int shift = (8 - (width % 8)) & 7;
 
        width = (width + 7) & ~7;
        height = (height + 7) & ~7;