Commit 9fc2b2d0 authored Aug 22, 2010 by Francisco Jerez Committed by Greg Kroah-Hartman Sep 03, 2010

vt: Fix console corruption on driver hand-over.



After 02f0777a "vc_origin" is no
longer reset to the screen buffer before calling the con_init() hook
of the new console driver.

If the old driver wasn't using a fixed scanout buffer (e.g. the case
of vgacon) "vc_origin" may be a pointer to a VRAM location, and its
contents aren't guaranteed to be preserved after calling con_deinit()
on the old driver and con_init() on the new driver, i.e. the
subsequent console resize may fill the framebuffer with garbage.

It can be reproduced in the transition from vgacon to the nouveau
framebuffer driver: in that case the legacy VGA aperture "vc_origin"
points to becomes unreadable after fbcon_init().

This patch reverts the mentioned commit. To avoid the problem it
intended to fix, stop using "vc_scr_end" in vc_do_resize() to
calculate how many rows we have to copy (actually the code looks
simpler this way without the help of "vc_scr_end").

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Cc: qiaochong <qiaochong@loongson.cn>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

parent 2bfc96a1

drivers/char/vt.c

+4 −11

Original line number	Diff line number	Diff line
		@@ -906,22 +906,16 @@ static int vc_do_resize(struct tty_struct tty, struct vc_data vc,
		* bottom of buffer
		*/
		old_origin += (old_rows - new_rows) * old_row_size;
		end = vc->vc_scr_end;
		} else {
		/*
		* Cursor is in no man's land, copy 1/2 screenful
		* from the top and bottom of cursor position
		*/
		old_origin += (vc->vc_y - new_rows/2) * old_row_size;
		end = old_origin + (old_row_size * new_rows);
		}
		} else
		/*
		* Cursor near the top, copy contents from the top of buffer
		*/
		end = (old_rows > new_rows) ? old_origin +
		(old_row_size * new_rows) :
		vc->vc_scr_end;
		}

		end = old_origin + old_row_size * min(old_rows, new_rows);

		update_attr(vc);

		@@ -3075,7 +3069,6 @@ static int bind_con_driver(const struct consw *csw, int first, int last,

		old_was_color = vc->vc_can_do_color;
		vc->vc_sw->con_deinit(vc);
		if (!vc->vc_origin)
		vc->vc_origin = (unsigned long)vc->vc_screenbuf;
		visual_init(vc, i, 0);
		set_origin(vc);

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