[PATCH 1/6] vt: make vt_console_print() compatible with the unicode screen buffer

Nicolas Pitre
2019-01-09T03:55:59Z

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+
---
drivers/tty/vt/vt.c | 47 +++++++++++++++------------------------------
1 file changed, 15 insertions(+), 32 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 41ec8e5010..b9004bd087 100644
--- 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);

--
2.20.1