releases/4.19.31/vt-perform-safe-console-erase-in-the-right-order.patch

   1 From a6dbe442755999960ca54a9b8ecfd9606be0ea75 Mon Sep 17 00:00:00 2001
   2 From: Nicolas Pitre <nicolas.pitre@linaro.org>
   3 Date: Mon, 11 Feb 2019 19:36:41 -0500
   4 Subject: vt: perform safe console erase in the right order
   5
   6 From: Nicolas Pitre <nicolas.pitre@linaro.org>
   7
   8 commit a6dbe442755999960ca54a9b8ecfd9606be0ea75 upstream.
   9
  10 Commit 4b4ecd9cb853 ("vt: Perform safe console erase only once") removed
  11 what appeared to be an extra call to scr_memsetw(). This missed the fact
  12 that set_origin() must be called before clearing the screen otherwise
  13 old screen content gets restored on the screen when using vgacon. Let's
  14 fix that by moving all the scrollback handling to flush_scrollback()
  15 where it logically belongs, and invoking it before the actual screen
  16 clearing in csi_J(), making the code simpler in the end.
  17
  18 Reported-by: Matthew Whitehead <tedheadster@gmail.com>
  19 Signed-off-by: Nicolas Pitre <nico@linaro.org>
  20 Tested-by: Matthew Whitehead <tedheadster@gmail.com>
  21 Fixes: 4b4ecd9cb853 ("vt: Perform safe console erase only once")
  22 Cc: stable@vger.kernel.org
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24
  25 ---
  26  drivers/tty/vt/vt.c |   15 +++++++--------
  27  1 file changed, 7 insertions(+), 8 deletions(-)
  28
  29 --- a/drivers/tty/vt/vt.c
  30 +++ b/drivers/tty/vt/vt.c
  31 @@ -935,8 +935,11 @@ static void flush_scrollback(struct vc_d
  32  {
  33         WARN_CONSOLE_UNLOCKED();
  34
  35 +       set_origin(vc);
  36         if (vc->vc_sw->con_flush_scrollback)
  37                 vc->vc_sw->con_flush_scrollback(vc);
  38 +       else
  39 +               vc->vc_sw->con_switch(vc);
  40  }
  41
  42  /*
  43 @@ -1506,8 +1509,10 @@ static void csi_J(struct vc_data *vc, in
  44                         count = ((vc->vc_pos - vc->vc_origin) >> 1) + 1;
  45                         start = (unsigned short *)vc->vc_origin;
  46                         break;
  47 +               case 3: /* include scrollback */
  48 +                       flush_scrollback(vc);
  49 +                       /* fallthrough */
  50                 case 2: /* erase whole display */
  51 -               case 3: /* (and scrollback buffer later) */
  52                         vc_uniscr_clear_lines(vc, 0, vc->vc_rows);
  53                         count = vc->vc_cols * vc->vc_rows;
  54                         start = (unsigned short *)vc->vc_origin;
  55 @@ -1516,13 +1521,7 @@ static void csi_J(struct vc_data *vc, in
  56                         return;
  57         }
  58         scr_memsetw(start, vc->vc_video_erase_char, 2 * count);
  59 -       if (vpar == 3) {
  60 -               set_origin(vc);
  61 -               flush_scrollback(vc);
  62 -               if (con_is_visible(vc))
  63 -                       update_screen(vc);
  64 -       } else if (con_should_update(vc))
  65 -               do_update_region(vc, (unsigned long) start, count);
  66 +       update_region(vc, (unsigned long) start, count);
  67         vc->vc_need_wrap = 0;
  68  }
  69