console: Expand dummy functions for CFI

This expands the no-op dummy functions into full prototypes to avoid
indirect call mismatches when running under Control Flow Integrity
checking, like with Clang's -fsanitize=cfi.

Co-Developed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 52 insertions, 17 deletions

diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c
index b90ef96e43d6..f2eafe2ed980 100644
--- a/drivers/video/console/dummycon.c
+++ b/drivers/video/console/dummycon.c
@@ -41,12 +41,47 @@ static void dummycon_init(struct vc_data *vc, int init)
 	vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS);
 }
 
-static int dummycon_dummy(void)
+static void dummycon_deinit(struct vc_data *vc) { }
+static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
+			   int width) { }
+static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
+static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
+			   int count, int ypos, int xpos) { }
+static void dummycon_cursor(struct vc_data *vc, int mode) { }
+
+static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
+			    unsigned int bottom, enum con_scroll dir,
+			    unsigned int lines)
+{
+	return false;
+}
+
+static int dummycon_switch(struct vc_data *vc)
 {
-    return 0;
+	return 0;
 }
 
-#define DUMMY	(void *)dummycon_dummy
+static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
+{
+	return 0;
+}
+
+static int dummycon_font_set(struct vc_data *vc, struct console_font *font,
+			     unsigned int flags)
+{
+	return 0;
+}
+
+static int dummycon_font_default(struct vc_data *vc,
+				 struct console_font *font, char *name)
+{
+	return 0;
+}
+
+static int dummycon_font_copy(struct vc_data *vc, int con)
+{
+	return 0;
+}
 
 /*
  *  The console `switch' structure for the dummy console
@@ -55,19 +90,19 @@ static int dummycon_dummy(void)
  */
 
 const struct consw dummy_con = {
-    .owner =		THIS_MODULE,
-    .con_startup =	dummycon_startup,
-    .con_init =		dummycon_init,
-    .con_deinit =	DUMMY,
-    .con_clear =	DUMMY,
-    .con_putc =		DUMMY,
-    .con_putcs =	DUMMY,
-    .con_cursor =	DUMMY,
-    .con_scroll =	DUMMY,
-    .con_switch =	DUMMY,
-    .con_blank =	DUMMY,
-    .con_font_set =	DUMMY,
-    .con_font_default =	DUMMY,
-    .con_font_copy =	DUMMY,
+	.owner =		THIS_MODULE,
+	.con_startup =	dummycon_startup,
+	.con_init =		dummycon_init,
+	.con_deinit =	dummycon_deinit,
+	.con_clear =	dummycon_clear,
+	.con_putc =		dummycon_putc,
+	.con_putcs =	dummycon_putcs,
+	.con_cursor =	dummycon_cursor,
+	.con_scroll =	dummycon_scroll,
+	.con_switch =	dummycon_switch,
+	.con_blank =	dummycon_blank,
+	.con_font_set =	dummycon_font_set,
+	.con_font_default =	dummycon_font_default,
+	.con_font_copy =	dummycon_font_copy,
 };
 EXPORT_SYMBOL_GPL(dummy_con);