vsprintf: Factor out %pO handler as kobject_string()

Move code from the long pointer() function. We are going to improve
error handling that will make it even more complicated.

This patch does not change the existing behavior.

Link: http://lkml.kernel.org/r/20190417115350.20479-7-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>

lib/vsprintf.c

@@ -1888,6 +1888,17 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
 	return widen_string(buf, buf - buf_start, end, spec);
 }
 
+static char *kobject_string(char *buf, char *end, void *ptr,
+			    struct printf_spec spec, const char *fmt)
+{
+	switch (fmt[1]) {
+	case 'F':
+		return device_node_string(buf, end, ptr, spec, fmt + 1);
+	}
+
+	return ptr_to_id(buf, end, ptr, spec);
+}
+
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
@@ -2082,11 +2093,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'G':
 		return flags_string(buf, end, ptr, fmt);
 	case 'O':
-		switch (fmt[1]) {
-		case 'F':
-			return device_node_string(buf, end, ptr, spec, fmt + 1);
-		}
-		break;
+		return kobject_string(buf, end, ptr, spec, fmt);
 	case 'x':
 		return pointer_string(buf, end, ptr, spec);
 	}