[PATCH 6.18 066/212] vt: save/restore unicode screen buffer for alternate screen

Greg Kroah-Hartman
2026-03-23T14:04:18Z

From: Nicolas Pitre <npitre@baylibre.com>

commit 5eb608319bb56464674a71b4a66ea65c6c435d64 upstream.

The alternate screen support added by commit 23743ba64709 ("vt: add
support for smput/rmput escape codes") only saves and restores the
regular screen buffer (vc_origin), but completely ignores the corresponding
unicode screen buffer (vc_uni_lines) creating a messed-up display.

Add vc_saved_uni_lines to save the unicode screen buffer when entering
the alternate screen, and restore it when leaving. Also ensure proper
cleanup in reset_terminal() and vc_deallocate().

Fixes: 23743ba64709 ("vt: add support for smput/rmput escape codes")
Cc: stable <stable@kernel.org>
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Link: https://patch.msgid.link/5o2p6qp3-91pq-0p17-or02-1oors4417ns7@onlyvoer.pbz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/vt/vt.c | 8 ++++++++
include/linux/console_struct.h | 1 +
2 files changed, 9 insertions(+)

--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1345,6 +1345,8 @@ struct vc_data *vc_deallocate(unsigned i
kfree(vc->vc_saved_screen);
vc->vc_saved_screen = NULL;
}
+ vc_uniscr_free(vc->vc_saved_uni_lines);
+ vc->vc_saved_uni_lines = NULL;
}
return vc;
}
@@ -1890,6 +1892,8 @@ static void enter_alt_screen(struct vc_d
vc->vc_saved_screen = kmemdup((u16 *)vc->vc_origin, size, GFP_KERNEL);
if (vc->vc_saved_screen == NULL)
return;
+ vc->vc_saved_uni_lines = vc->vc_uni_lines;
+ vc->vc_uni_lines = NULL;
vc->vc_saved_rows = vc->vc_rows;
vc->vc_saved_cols = vc->vc_cols;
save_cur(vc);
@@ -1911,6 +1915,8 @@ static void leave_alt_screen(struct vc_d
dest = ((u16 *)vc->vc_origin) + r * vc->vc_cols;
memcpy(dest, src, 2 * cols);
}
+ vc_uniscr_set(vc, vc->vc_saved_uni_lines);
+ vc->vc_saved_uni_lines = NULL;
restore_cur(vc);
/* Update the entire screen */
if (con_should_update(vc))
@@ -2233,6 +2239,8 @@ static void reset_terminal(struct vc_dat
if (vc->vc_saved_screen != NULL) {
kfree(vc->vc_saved_screen);
vc->vc_saved_screen = NULL;
+ vc_uniscr_free(vc->vc_saved_uni_lines);
+ vc->vc_saved_uni_lines = NULL;
vc->vc_saved_rows = 0;
vc->vc_saved_cols = 0;
}
--- a/include/linux/console_struct.h
+++ b/include/linux/console_struct.h
@@ -160,6 +160,7 @@ struct vc_data {
struct uni_pagedict **uni_pagedict_loc; /* [!] Location of uni_pagedict variable for this console */
u32 **vc_uni_lines; /* unicode screen content */
u16 *vc_saved_screen;
+ u32 **vc_saved_uni_lines;
unsigned int vc_saved_cols;
unsigned int vc_saved_rows;
/* additional information is in vt_kern.h */