signal: make get_signal() return bool

make get_signal() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-18-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/signal.h

@@ -265,7 +265,7 @@ extern void set_current_blocked(sigset_t *);
 extern void __set_current_blocked(const sigset_t *);
 extern int show_unhandled_signals;
 
-extern int get_signal(struct ksignal *ksig);
+extern bool get_signal(struct ksignal *ksig);
 extern void signal_setup_done(int failed, struct ksignal *ksig, int stepping);
 extern void exit_signals(struct task_struct *tsk);
 extern void kernel_sigaction(int, __sighandler_t);

kernel/signal.c

@@ -2287,7 +2287,7 @@ static int ptrace_signal(int signr, siginfo_t *info)
 	return signr;
 }
 
-int get_signal(struct ksignal *ksig)
+bool get_signal(struct ksignal *ksig)
 {
 	struct sighand_struct *sighand = current->sighand;
 	struct signal_struct *signal = current->signal;
@@ -2297,7 +2297,7 @@ int get_signal(struct ksignal *ksig)
 		task_work_run();
 
 	if (unlikely(uprobe_deny_signal()))
-		return 0;
+		return false;
 
 	/*
 	 * Do this once, we can't return to user-mode if freezing() == T.