Commit bfd8d8fe authored Jan 10, 2019 by Nicolas Pitre Committed by Greg Kroah-Hartman Jan 18, 2019

vgacon: unconfuse vc_origin when using soft scrollback



When CONFIG_VGACON_SOFT_SCROLLBACK is selected, the VGA display memory
index and vc_visible_origin don't change when scrollback is activated.
The actual screen content is saved away and the scrollbackdata is copied
over it. However the vt code, and /dev/vcs devices in particular, still
expect vc_origin to always point at the actual screen content not the
displayed scrollback content.

So adjust vc_origin to point at the saved screen content when scrollback
is active and set it back to vc_visible_origin when restoring the screen.

This fixes /dev/vcsa<n> that return scrollback content when they
shouldn't (onli /dev/vcsa without a number should), and also fixes
/dev/vcsu that should return scrollback content when scrollback is
active but currently doesn't.

An unnecessary call to vga_set_mem_top() is also removed.

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

parent 0c9b1965

drivers/video/console/vgacon.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -271,6 +271,7 @@ static void vgacon_scrollback_update(struct vc_data *c, int t, int count)

		static void vgacon_restore_screen(struct vc_data *c)
		{
		c->vc_origin = c->vc_visible_origin;
		vgacon_scrollback_cur->save = 0;

		if (!vga_is_gfx && !vgacon_scrollback_cur->restore) {
		@@ -287,8 +288,7 @@ static void vgacon_scrolldelta(struct vc_data *c, int lines)
		int start, end, count, soff;

		if (!lines) {
		c->vc_visible_origin = c->vc_origin;
		vga_set_mem_top(c);
		vgacon_restore_screen(c);
		return;
		}

		@@ -298,6 +298,7 @@ static void vgacon_scrolldelta(struct vc_data *c, int lines)
		if (!vgacon_scrollback_cur->save) {
		vgacon_cursor(c, CM_ERASE);
		vgacon_save_screen(c);
		c->vc_origin = (unsigned long)c->vc_screenbuf;
		vgacon_scrollback_cur->save = 1;
		}

		@@ -335,7 +336,7 @@ static void vgacon_scrolldelta(struct vc_data *c, int lines)
		int copysize;

		int diff = c->vc_rows - count;
		void d = (void ) c->vc_origin;
		void d = (void ) c->vc_visible_origin;
		void s = (void ) c->vc_screenbuf;

		count *= c->vc_size_row;

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