vt: make vt_console_print() compatible with the unicode screen buffer

When kernel messages are printed to the console, they appear blank on
the unicode screen. This is because vt_console_print() is lacking a call
to vc_uniscr_putc(). However the later function assumes vc->vc_x is
always up to date when called, which is not the case here as
vt_console_print() uses it to mark the beginning of the display update.

This patch reworks (and simplifies) vt_console_print() so that vc->vc_x
is always valid and keeps the start of display update in a local variable
instead, which finally allows for adding the missing vc_uniscr_putc()
call.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 41ec8e5010f30a544b82ca439cc5a481fe499b19..b9004bd08772010fc46ddb726ba358f31885e3f5 100644 (file)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2884,8 +2884,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
        unsigned char c;
        static DEFINE_SPINLOCK(printing_lock);
        const ushort *start;
-       ushort cnt = 0;
-       ushort myx;
+       ushort start_x, cnt;
        int kmsg_console;
 
        /* console busy or not yet initialized */
@@ -2898,10 +2897,6 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
        if (kmsg_console && vc_cons_allocated(kmsg_console - 1))
                vc = vc_cons[kmsg_console - 1].d;
 
-       /* read `x' only after setting currcons properly (otherwise
-          the `x' macro will read the x of the foreground console). */
-       myx = vc->vc_x;
-
        if (!vc_cons_allocated(fg_console)) {
                /* impossible */
                /* printk("vt_console_print: tty %d not allocated ??\n", currcons+1); */
@@ -2916,53 +2911,41 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
                hide_cursor(vc);
 
        start = (ushort *)vc->vc_pos;
-
-       /* Contrived structure to try to emulate original need_wrap behaviour
-        * Problems caused when we have need_wrap set on '\n' character */
+       start_x = vc->vc_x;
+       cnt = 0;
        while (count--) {
                c = *b++;
                if (c == 10 || c == 13 || c == 8 || vc->vc_need_wrap) {
-                       if (cnt > 0) {
-                               if (con_is_visible(vc))
-                                       vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, vc->vc_x);
-                               vc->vc_x += cnt;
-                               if (vc->vc_need_wrap)
-                                       vc->vc_x--;
-                               cnt = 0;
-                       }
+                       if (cnt && con_is_visible(vc))
+                               vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, start_x);
+                       cnt = 0;
                        if (c == 8) {           /* backspace */
                                bs(vc);
                                start = (ushort *)vc->vc_pos;
-                               myx = vc->vc_x;
+                               start_x = vc->vc_x;
                                continue;
                        }
                        if (c != 13)
                                lf(vc);
                        cr(vc);
                        start = (ushort *)vc->vc_pos;
-                       myx = vc->vc_x;
+                       start_x = vc->vc_x;
                        if (c == 10 || c == 13)
                                continue;
                }
+               vc_uniscr_putc(vc, c);
                scr_writew((vc->vc_attr << 8) + c, (unsigned short *)vc->vc_pos);
                notify_write(vc, c);
                cnt++;
-               if (myx == vc->vc_cols - 1) {
-                       vc->vc_need_wrap = 1;
-                       continue;
-               }
-               vc->vc_pos += 2;
-               myx++;
-       }
-       if (cnt > 0) {
-               if (con_is_visible(vc))
-                       vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, vc->vc_x);
-               vc->vc_x += cnt;
-               if (vc->vc_x == vc->vc_cols) {
-                       vc->vc_x--;
+               if (vc->vc_x == vc->vc_cols - 1) {
                        vc->vc_need_wrap = 1;
+               } else {
+                       vc->vc_pos += 2;
+                       vc->vc_x++;
                }
        }
+       if (cnt && con_is_visible(vc))
+               vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, start_x);
        set_cursor(vc);
        notify_update(vc);