linux-kernel - [PATCH 22/22] tty: vt: decrypt magic constants in vc_is

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Date: Fri,  2 Feb 2024 07:56:08 +0100
From: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To: gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Subject: [PATCH 22/22] tty: vt: decrypt magic constants in vc_is_control()

0x0d00ff81 and 0x0800f501 are bitmasks of ASCII characters. Spell them
explicitly using BIT() + ASCII constants. GENMASK() is used for the
9-bit range in CTRL_ACTION.

This also modifies the 'if' checking if the masks should be applied.
>From a "random" ' ' to the actual size of the bitmasks' type.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
---
 drivers/tty/vt/vt.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index e35f7a31a7bd..463be4e48dc8 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2893,9 +2893,13 @@ static bool vc_is_control(struct vc_data *vc, int tc, int c)
 	 * as cursor movement) and should not be displayed as a glyph unless
 	 * the disp_ctrl mode is explicitly enabled.
 	 */
-	static const u32 CTRL_ACTION = 0x0d00ff81;
+	static const u32 CTRL_ACTION = BIT(ASCII_NULL) |
+		GENMASK(ASCII_SHIFTIN, ASCII_BELL) | BIT(ASCII_CANCEL) |
+		BIT(ASCII_SUBSTITUTE) | BIT(ASCII_ESCAPE);
 	/* Cannot be overridden by disp_ctrl */
-	static const u32 CTRL_ALWAYS = 0x0800f501;
+	static const u32 CTRL_ALWAYS = BIT(ASCII_NULL) | BIT(ASCII_BACKSPACE) |
+		BIT(ASCII_LINEFEED) | BIT(ASCII_SHIFTIN) | BIT(ASCII_SHIFTOUT) |
+		BIT(ASCII_CAR_RET) | BIT(ASCII_FORMFEED) | BIT(ASCII_ESCAPE);
 
 	if (vc->vc_state != ESnormal)
 		return true;
@@ -2912,7 +2916,7 @@ static bool vc_is_control(struct vc_data *vc, int tc, int c)
 	 * useless without them; to display an arbitrary font position use the
 	 * direct-to-font zone in UTF-8 mode.
 	 */
-	if (c < ' ') {
+	if (c < BITS_PER_TYPE(CTRL_ALWAYS)) {
 		if (vc->vc_disp_ctrl)
 			return CTRL_ALWAYS & BIT(c);
 		else
-- 
2.43.0