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>

6 files changed, 14 insertions, 12 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 */
diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 8eda7b60df8f..ad31983b43eb 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -1881,7 +1881,7 @@ static int fbcon_scroll(struct vc_data *vc, int t, int b, int dir,
                         scr_memsetw((unsigned short *) (vc->vc_origin +
                                                         vc->vc_size_row *
                                                         (b - count)),
-                                    vc->vc_video_erase_char,
+                                    vc->vc_scrl_erase_char,
                                     vc->vc_size_row * count);
                         return 1;
                         break;
@@ -1953,7 +1953,7 @@ static int fbcon_scroll(struct vc_data *vc, int t, int b, int dir,
                         scr_memsetw((unsigned short *) (vc->vc_origin +
                                                         vc->vc_size_row *
                                                         (b - count)),
-                                    vc->vc_video_erase_char,
+                                    vc->vc_scrl_erase_char,
                                     vc->vc_size_row * count);
                         return 1;
                 }
@@ -1972,7 +1972,7 @@ static int fbcon_scroll(struct vc_data *vc, int t, int b, int dir,
                         scr_memsetw((unsigned short *) (vc->vc_origin +
                                                         vc->vc_size_row *
                                                         t),
-                                    vc->vc_video_erase_char,
+                                    vc->vc_scrl_erase_char,
                                     vc->vc_size_row * count);
                         return 1;
                         break;
@@ -2042,7 +2042,7 @@ static int fbcon_scroll(struct vc_data *vc, int t, int b, int dir,
                         scr_memsetw((unsigned short *) (vc->vc_origin +
                                                         vc->vc_size_row *
                                                         t),
-                                    vc->vc_video_erase_char,
+                                    vc->vc_scrl_erase_char,
                                     vc->vc_size_row * count);
                         return 1;
                 }
diff --git a/drivers/video/console/mdacon.c b/drivers/video/console/mdacon.c
index bd8d995fe25d..38a296bbdfc9 100644
--- a/drivers/video/console/mdacon.c
+++ b/drivers/video/console/mdacon.c
@@ -531,7 +531,7 @@ static void mdacon_cursor(struct vc_data *c, int mode)
 
 static int mdacon_scroll(struct vc_data *c, int t, int b, int dir, int lines)
 {
-        u16 eattr = mda_convert_attr(c->vc_video_erase_char);
+        u16 eattr = mda_convert_attr(c->vc_scrl_erase_char);
 
         if (!lines)
                 return 0;
diff --git a/drivers/video/console/sticon.c b/drivers/video/console/sticon.c
index 67a682d6cc7b..a11cc2fdd4cd 100644
--- a/drivers/video/console/sticon.c
+++ b/drivers/video/console/sticon.c
@@ -170,12 +170,12 @@ static int sticon_scroll(struct vc_data *conp, int t, int b, int dir, int count)
     switch (dir) {
     case SM_UP:
         sti_bmove(sti, t + count, 0, t, 0, b - t - count, conp->vc_cols);
-        sti_clear(sti, b - count, 0, count, conp->vc_cols, conp->vc_video_erase_char);
+        sti_clear(sti, b - count, 0, count, conp->vc_cols, conp->vc_scrl_erase_char);
         break;
 
     case SM_DOWN:
         sti_bmove(sti, t, 0, t + count, 0, b - t - count, conp->vc_cols);
-        sti_clear(sti, t, 0, count, conp->vc_cols, conp->vc_video_erase_char);
+        sti_clear(sti, t, 0, count, conp->vc_cols, conp->vc_scrl_erase_char);
         break;
     }
 
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 6df29a62d720..bd1f57b259d9 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1350,7 +1350,7 @@ static int vgacon_scroll(struct vc_data *c, int t, int b, int dir,
                 } else
                         c->vc_origin += delta;
                 scr_memsetw((u16 *) (c->vc_origin + c->vc_screenbuf_size -
-                                     delta), c->vc_video_erase_char,
+                                     delta), c->vc_scrl_erase_char,
                             delta);
         } else {
                 if (oldo - delta < vga_vram_base) {
@@ -1363,7 +1363,7 @@ static int vgacon_scroll(struct vc_data *c, int t, int b, int dir,
                 } else
                         c->vc_origin -= delta;
                 c->vc_scr_end = c->vc_origin + c->vc_screenbuf_size;
-                scr_memsetw((u16 *) (c->vc_origin), c->vc_video_erase_char,
+                scr_memsetw((u16 *) (c->vc_origin), c->vc_scrl_erase_char,
                             delta);
         }
         c->vc_scr_end = c->vc_origin + c->vc_screenbuf_size;
diff --git a/include/linux/console_struct.h b/include/linux/console_struct.h
index d71f7c0f931b..b03f80a078be 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 */