Commit 6609cff6 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Greg Kroah-Hartman
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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: default avatarNicolas Pitre <nico@linaro.org>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent fc01d8c6

drivers/tty/vt/vt.c

+15 −32
Original line number Diff line number Diff line
@@ -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--;

			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) {

		if (vc->vc_x == vc->vc_cols - 1) {

			vc->vc_need_wrap = 1;

			continue;

		}

		} else {

			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--;

			vc->vc_need_wrap = 1;

			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);