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>

3 files changed, 67 insertions, 32 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);
diff --git a/drivers/video/console/newport_con.c b/drivers/video/console/newport_con.c
index 42d02a206059..6897bd0fc00e 100644
--- a/drivers/video/console/newport_con.c
+++ b/drivers/video/console/newport_con.c
@@ -673,14 +673,14 @@ static bool newport_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
 	return true;
 }
 
-static int newport_dummy(struct vc_data *c)
+static int newport_set_origin(struct vc_data *vc)
 {
 	return 0;
 }
 
-#define DUMMY (void *) newport_dummy
+static void newport_save_screen(struct vc_data *vc) { }
 
-const struct consw newport_con = {
+static const struct consw newport_con = {
 	.owner		  = THIS_MODULE,
 	.con_startup	  = newport_startup,
 	.con_init	  = newport_init,
@@ -694,8 +694,8 @@ const struct consw newport_con = {
 	.con_blank	  = newport_blank,
 	.con_font_set	  = newport_font_set,
 	.con_font_default = newport_font_default,
-	.con_set_origin	  = DUMMY,
-	.con_save_screen  = DUMMY
+	.con_set_origin	  = newport_set_origin,
+	.con_save_screen  = newport_save_screen
 };
 
 static int newport_probe(struct gio_device *dev,
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index a17ba1465815..f09e17b60e45 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1272,7 +1272,8 @@ static int vgacon_adjust_height(struct vc_data *vc, unsigned fontheight)
 	return 0;
 }
 
-static int vgacon_font_set(struct vc_data *c, struct console_font *font, unsigned flags)
+static int vgacon_font_set(struct vc_data *c, struct console_font *font,
+			   unsigned int flags)
 {
 	unsigned charcount = font->charcount;
 	int rc;
@@ -1407,21 +1408,20 @@ static bool vgacon_scroll(struct vc_data *c, unsigned int t, unsigned int b,
  *  The console `switch' structure for the VGA based console
  */
 
-static int vgacon_dummy(struct vc_data *c)
-{
-	return 0;
-}
-
-#define DUMMY (void *) vgacon_dummy
+static void vgacon_clear(struct vc_data *vc, int sy, int sx, int height,
+			 int width) { }
+static void vgacon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
+static void vgacon_putcs(struct vc_data *vc, const unsigned short *s,
+			 int count, int ypos, int xpos) { }
 
 const struct consw vga_con = {
 	.owner = THIS_MODULE,
 	.con_startup = vgacon_startup,
 	.con_init = vgacon_init,
 	.con_deinit = vgacon_deinit,
-	.con_clear = DUMMY,
-	.con_putc = DUMMY,
-	.con_putcs = DUMMY,
+	.con_clear = vgacon_clear,
+	.con_putc = vgacon_putc,
+	.con_putcs = vgacon_putcs,
 	.con_cursor = vgacon_cursor,
 	.con_scroll = vgacon_scroll,
 	.con_switch = vgacon_switch,