Commit 754bda98 authored by Jiri Slaby's avatar Jiri Slaby Committed by Greg Kroah-Hartman
Browse files

vc: extract detecting control characters from do_con_write 



Move the control characters detection to a separate function dubbed
vc_is_control. It makes the 14 subexpressions a "bit" more readable. And
also simplifies next patches.

It moves also CTRL_ACTION and CTRL_ALWAYS to this new function, as they
are used exclusively here. While at it, these are converted to static
const variables.

And we use "& BIT()" instead of ">>" and "& 1".

Checked using symbolic execution (klee), that the old and new
behaviors are the same.

Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200615074910.19267-18-jslaby@suse.cz


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 917ae1a9

drivers/tty/vt/vt.c

+45 −26
Original line number Diff line number Diff line
@@ -127,14 +127,6 @@ struct con_driver { 
static struct con_driver registered_con_driver[MAX_NR_CON_DRIVER];

const struct consw *conswitchp;



/* A bitmap for codes <32. A bit of 1 indicates that the code

 * corresponding to that bit number invokes some special action

 * (such as cursor movement) and should not be displayed as a

 * glyph unless the disp_ctrl mode is explicitly enabled.

 */

#define CTRL_ACTION 0x0d00ff81

#define CTRL_ALWAYS 0x0800f501	/* Cannot be overridden by disp_ctrl */



/*

 * Here is the default bell parameters: 750HZ, 1/8th of a second

 */
@@ -2691,13 +2683,56 @@ static inline unsigned char vc_invert_attr(const struct vc_data *vc) 
		((vc->vc_attr & 0x07) << 4);

}



static bool vc_is_control(struct vc_data *vc, int tc, int c)

{

	/*

	 * A bitmap for codes <32. A bit of 1 indicates that the code

	 * corresponding to that bit number invokes some special action (such

	 * 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;

	/* Cannot be overridden by disp_ctrl */

	static const u32 CTRL_ALWAYS = 0x0800f501;



	if (vc->vc_state != ESnormal)

		return true;



	if (!tc)

		return true;



	/*

	 * If the original code was a control character we only allow a glyph

	 * to be displayed if the code is not normally used (such as for cursor

	 * movement) or if the disp_ctrl mode has been explicitly enabled.

	 * Certain characters (as given by the CTRL_ALWAYS bitmap) are always

	 * displayed as control characters, as the console would be pretty

	 * useless without them; to display an arbitrary font position use the

	 * direct-to-font zone in UTF-8 mode.

	 */

	if (c < 32) {

		if (vc->vc_disp_ctrl)

			return CTRL_ALWAYS & BIT(c);

		else

			return vc->vc_utf || (CTRL_ACTION & BIT(c));

	}



	if (c == 127 && !vc->vc_disp_ctrl)

		return true;



	if (c == 128 + 27)

		return true;



	return false;

}



/* acquires console_lock */

static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int count)

{

	struct vc_draw_region draw = {

		.x = -1,

	};

	int c, next_c, tc, ok, n = 0;

	int c, next_c, tc, n = 0;

	unsigned int currcons;

	struct vc_data *vc;

	unsigned char vc_attr;
@@ -2755,23 +2790,7 @@ rescan_last_byte: 
					&param) == NOTIFY_STOP)

			continue;



                /* If the original code was a control character we

                 * only allow a glyph to be displayed if the code is

                 * not normally used (such as for cursor movement) or

                 * if the disp_ctrl mode has been explicitly enabled.

                 * Certain characters (as given by the CTRL_ALWAYS

                 * bitmap) are always displayed as control characters,

                 * as the console would be pretty useless without

                 * them; to display an arbitrary font position use the

                 * direct-to-font zone in UTF-8 mode.

                 */

                ok = tc && (c >= 32 ||

			    !(vc->vc_disp_ctrl ? (CTRL_ALWAYS >> c) & 1 :

				  vc->vc_utf || ((CTRL_ACTION >> c) & 1)))

			&& (c != 127 || vc->vc_disp_ctrl)

			&& (c != 128+27);



		if (vc->vc_state == ESnormal && ok) {

		if (!vc_is_control(vc, tc, c)) {

			if (vc->vc_utf && !vc->vc_disp_ctrl) {

				if (is_double_width(c))

					width = 2;

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