4.20-stable review patch. If anyone has any objections, please let me know.
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From: Nicolas Pitre nicolas.pitre@linaro.org
commit bfd8d8fe98b8792f362cd210a7873969f8d2fc04 upstream.
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
--- drivers/video/console/vgacon.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/drivers/video/console/vgacon.c +++ b/drivers/video/console/vgacon.c @@ -271,6 +271,7 @@ static void vgacon_scrollback_update(str
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 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 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 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;