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, 1 insertions, 0 deletions

diff --git a/include/linux/console_struct.h b/include/linux/console_struct.h
index d71f7c0f931..b03f80a078b 100644
--- a/include/linux/console_struct.h
+++ b/include/linux/console_struct.h
@@ -53,6 +53,7 @@ struct vc_data {
         unsigned short  vc_hi_font_mask;        /* [#] Attribute set for upper 256 chars of font or 0 if not supported */
         struct console_font vc_font;            /* Current VC font set */
         unsigned short  vc_video_erase_char;    /* Background erase character */
+        unsigned short  vc_scrl_erase_char;     /* Erase character for scroll */
         /* VT terminal data */
         unsigned int    vc_state;               /* Escape sequence parser state */
         unsigned int    vc_npar,vc_par[NPAR];   /* Parameters of current escape sequence */