tty: provide tty_name() even without CONFIG_TTY

commit 188e3c5c upstream.

The audit subsystem just started printing the name of the tty,
but that causes a build failure when CONFIG_TTY is disabled:

kernel/built-in.o: In function `audit_log_task_info':
memremap.c:(.text+0x5e34c): undefined reference to `tty_name'
kernel/built-in.o: In function `audit_set_loginuid':
memremap.c:(.text+0x63b34): undefined reference to `tty_name'

This adds tty_name() to the list of functions that are provided
as trivial stubs in that configuration.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: db0a6fb5 ("audit: add tty field to LOGIN event")
Signed-off-by: Paul Moore <paul@paul-moore.com>
[natechancellor: tty_paranoia_check still exists]
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/tty.h

@@ -372,6 +372,7 @@ extern void proc_clear_tty(struct task_struct *p);
 extern struct tty_struct *get_current_tty(void);
 /* tty_io.c */
 extern int __init tty_init(void);
+extern const char *tty_name(const struct tty_struct *tty);
 #else
 static inline void console_init(void)
 { }
@@ -392,6 +393,8 @@ static inline struct tty_struct *get_current_tty(void)
 /* tty_io.c */
 static inline int __init tty_init(void)
 { return 0; }
+static inline const char *tty_name(const struct tty_struct *tty)
+{ return "(none)"; }
 #endif
 
 extern void tty_write_flush(struct tty_struct *);
@@ -420,7 +423,6 @@ static inline struct tty_struct *tty_kref_get(struct tty_struct *tty)
 
 extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
 			      const char *routine);
-extern const char *tty_name(const struct tty_struct *tty);
 extern void tty_wait_until_sent(struct tty_struct *tty, long timeout);
 extern int __tty_check_change(struct tty_struct *tty, int sig);
 extern int tty_check_change(struct tty_struct *tty);