vt: bracketed paste support

This is comprised of 3 aspects:

- Take note of when applications advertise bracketed paste support via
"\e[?2004h" and "\e[?2004l".

- Insert bracketed paste markers ("\e[200~" and "\e[201~") around pasted
content in paste_selection() when bracketed paste is active.

- Add TIOCL_GETBRACKETEDPASTE to return bracketed paste status so user
space daemons implementing cut-and-paste functionality (e.g. gpm,
BRLTTY) may know when to insert bracketed paste markers.

Link: https://en.wikipedia.org/wiki/Bracketed-paste

Signed-off-by: Nicolas Pitre <[e-mail]>
Reviewed-by: Jiri Slaby <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/vt/selection.c

···
 	DECLARE_WAITQUEUE(wait, current);
 	int ret = 0;
 
+	bool bp = vc->vc_bracketed_paste;
+	static const char bracketed_paste_start[] = "\033[200~";
+	static const char bracketed_paste_end[]   = "\033[201~";
+	const char *bps = bp ? bracketed_paste_start : NULL;
+	const char *bpe = bp ? bracketed_paste_end : NULL;
+
 	console_lock();
 	poke_blanked_console();
 	console_unlock();
···
 
 	add_wait_queue(&vc->paste_wait, &wait);
 	mutex_lock(&vc_sel.lock);
-	while (vc_sel.buffer && vc_sel.buf_len > pasted) {
+	while (vc_sel.buffer && (vc_sel.buf_len > pasted || bpe)) {
 		set_current_state(TASK_INTERRUPTIBLE);
 		if (signal_pending(current)) {
 			ret = -EINTR;
···
 			continue;
 		}
 		__set_current_state(TASK_RUNNING);
+
+		if (bps) {
+			bps += tty_ldisc_receive_buf(ld, bps, NULL, strlen(bps));
+			if (*bps != '\0')
+				continue;
+			bps = NULL;
+		}
+
 		count = vc_sel.buf_len - pasted;
-		count = tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted, NULL,
-					      count);
-		pasted += count;
+		if (count) {
+			pasted += tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted,
+							NULL, count);
+			if (vc_sel.buf_len > pasted)
+				continue;
+		}
+
+		if (bpe) {
+			bpe += tty_ldisc_receive_buf(ld, bpe, NULL, strlen(bpe));
+			if (*bpe == '\0')
+				bpe = NULL;
+		}
 	}
 	mutex_unlock(&vc_sel.lock);
 	remove_wait_queue(&vc->paste_wait, &wait);

drivers/tty/vt/vt.c

···
 	return vc_cons[fg_console].d->vc_report_mouse;
 }
 
+/* invoked via ioctl(TIOCLINUX) */
+static int get_bracketed_paste(struct tty_struct *tty)
+{
+	struct vc_data *vc = tty->driver_data;
+
+	return vc->vc_bracketed_paste;
+}
+
 enum {
 	CSI_DEC_hl_CURSOR_KEYS	= 1,	/* CKM: cursor keys send ^[Ox/^[[x */
 	CSI_DEC_hl_132_COLUMNS	= 3,	/* COLM: 80/132 mode switch */
···
 	CSI_DEC_hl_MOUSE_X10	= 9,
 	CSI_DEC_hl_SHOW_CURSOR	= 25,	/* TCEM */
 	CSI_DEC_hl_MOUSE_VT200	= 1000,
+	CSI_DEC_hl_BRACKETED_PASTE = 2004,
 };
 
 /* console_lock is held */
···
 			break;
 		case CSI_DEC_hl_MOUSE_VT200:
 			vc->vc_report_mouse = on_off ? 2 : 0;
+			break;
+		case CSI_DEC_hl_BRACKETED_PASTE:
+			vc->vc_bracketed_paste = on_off;
 			break;
 		}
 }
···
 	vc->state.charset	= 0;
 	vc->vc_need_wrap	= 0;
 	vc->vc_report_mouse	= 0;
+	vc->vc_bracketed_paste	= 0;
 	vc->vc_utf              = default_utf8;
 	vc->vc_utf_count	= 0;
 
···
 		break;
 	case TIOCL_BLANKEDSCREEN:
 		return console_blanked;
+	case TIOCL_GETBRACKETEDPASTE:
+		return get_bracketed_paste(tty);
 	default:
 		return -EINVAL;
 	}

include/linux/console_struct.h

···
 	unsigned int	vc_need_wrap	: 1;
 	unsigned int	vc_can_do_color	: 1;
 	unsigned int	vc_report_mouse : 2;
+	unsigned int	vc_bracketed_paste : 1;
 	unsigned char	vc_utf		: 1;	/* Unicode UTF-8 encoding */
 	unsigned char	vc_utf_count;
 		 int	vc_utf_char;

include/uapi/linux/tiocl.h

···
 #define TIOCL_BLANKSCREEN	14	/* keep screen blank even if a key is pressed */
 #define TIOCL_BLANKEDSCREEN	15	/* return which vt was blanked */
 #define TIOCL_GETKMSGREDIRECT	17	/* get the vt the kernel messages are restricted to */
+#define TIOCL_GETBRACKETEDPASTE	18	/* get whether paste may be bracketed */
 
 #endif /* _LINUX_TIOCL_H */