tracing/filters: distinguish between signed and unsigned fields

The new filter comparison ops need to be able to distinguish between
signed and unsigned field types, so add an is_signed flag/param to the
event field struct/trace_define_fields().  Also define a simple macro,
is_signed_type() to determine the signedness at compile time, used in the
trace macros.  If the is_signed_type() macro won't work with a specific
type, a new slightly modified version of TRACE_FIELD() called
TRACE_FIELD_SIGN(), allows the signedness to be set explicitly.

[ Impact: extend trace-filter code for new feature ]

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905893.6416.120.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/ftrace_event.h

@@ -122,8 +122,9 @@ extern int filter_current_check_discard(struct ftrace_event_call *call,
 					struct ring_buffer_event *event);
 
 extern int trace_define_field(struct ftrace_event_call *call, char *type,
-			      char *name, int offset, int size);
+			      char *name, int offset, int size, int is_signed);
 
+#define is_signed_type(type)	(((type)(-1)) < 0)
 
 /*
  * The double __builtin_constant_p is because gcc will give us an error
@@ -144,10 +145,10 @@ do {									\
 		__trace_printk(ip, fmt, ##args);			\
 } while (0)
 
-#define __common_field(type, item)					\
+#define __common_field(type, item, is_signed)				\
 	ret = trace_define_field(event_call, #type, "common_" #item,	\
 				 offsetof(typeof(field.ent), item),	\
-				 sizeof(field.ent.item));		\
+				 sizeof(field.ent.item), is_signed);	\
 	if (ret)							\
 		return ret;