vt: fix background color on line feed

A command that causes a line feed while a background color is active,
such as

	perl -e 'print "x" x 60, "\e[44m", "x" x 40, "\e[0m\n"'
and
	perl -e 'print "x" x 40, "\e[44m\n", "x" x 40, "\e[0m\n"'

causes the line that was started as a result of the line feed to be completely
filled with the currently active background color instead of the default
color.

When scrolling, part of the current screen is memcpy'd/memmove'd to the new
region, and the new line(s) that will appear as a result are cleared using
memset.  However, the lines are cleared with vc->vc_video_erase_char, causing
them to be colored with the currently active background color.  This is
different from X11 terminal emulators which always paint the new lines with
the default background color (e.g.  `xterm -bg black`).

The clear operation (\e[1J and \e[2J) also use vc_video_erase_char, so a new
vc->vc_scrl_erase_char is introduced with contains the erase character used
for scrolling, which is built from vc->vc_def_color instead of vc->vc_color.

Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index df4c3ead9e2b..1c2660477135 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -301,7 +301,7 @@ static void scrup(struct vc_data *vc, unsigned int t, unsigned int b, int nr)
         d = (unsigned short *)(vc->vc_origin + vc->vc_size_row * t);
         s = (unsigned short *)(vc->vc_origin + vc->vc_size_row * (t + nr));
         scr_memmovew(d, s, (b - t - nr) * vc->vc_size_row);
-        scr_memsetw(d + (b - t - nr) * vc->vc_cols, vc->vc_video_erase_char,
+        scr_memsetw(d + (b - t - nr) * vc->vc_cols, vc->vc_scrl_erase_char,
                     vc->vc_size_row * nr);
 }
 
@@ -319,7 +319,7 @@ static void scrdown(struct vc_data *vc, unsigned int t, unsigned int b, int nr)
         s = (unsigned short *)(vc->vc_origin + vc->vc_size_row * t);
         step = vc->vc_cols * nr;
         scr_memmovew(s + step, s, (b - t - nr) * vc->vc_size_row);
-        scr_memsetw(s, vc->vc_video_erase_char, 2 * step);
+        scr_memsetw(s, vc->vc_scrl_erase_char, 2 * step);
 }
 
 static void do_update_region(struct vc_data *vc, unsigned long start, int count)
@@ -400,7 +400,7 @@ static u8 build_attr(struct vc_data *vc, u8 _color, u8 _intensity, u8 _blink,
  *  Bit 7   : blink
  */
         {
-        u8 a = vc->vc_color;
+        u8 a = _color;
         if (!vc->vc_can_do_color)
                 return _intensity |
                        (_italic ? 2 : 0) |
@@ -434,6 +434,7 @@ static void update_attr(struct vc_data *vc)
                       vc->vc_blink, vc->vc_underline,
                       vc->vc_reverse ^ vc->vc_decscnm, vc->vc_italic);
         vc->vc_video_erase_char = (build_attr(vc, vc->vc_color, 1, vc->vc_blink, 0, vc->vc_decscnm, 0) << 8) | ' ';
+        vc->vc_scrl_erase_char = (build_attr(vc, vc->vc_def_color, 1, false, false, false, false) << 8) | ' ';
 }
 
 /* Note: inverting the screen twice should revert to the original state */