Commit 04295780 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

tracing/events: Show real number in array fields 



Currently we have in something like the sched_switch event:

  field:char prev_comm[TASK_COMM_LEN];	offset:12;	size:16;	signed:1;

When a userspace tool such as perf tries to parse this, the
TASK_COMM_LEN is meaningless. This is done because the TRACE_EVENT() macro
simply uses a #len to show the string of the length. When the length is
an enum, we get a string that means nothing for tools.

By adding a static buffer and a mutex to protect it, we can store the
string into that buffer with snprintf and show the actual number.
Now we get:

  field:char prev_comm[16];       offset:12;      size:16;        signed:1;

Something much more useful.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 45677454

include/linux/ftrace_event.h

+4 −0
Original line number Diff line number Diff line
@@ -225,6 +225,10 @@ enum { 
	FILTER_PTR_STRING,

};



#define EVENT_STORAGE_SIZE 128

extern struct mutex event_storage_mutex;

extern char event_storage[EVENT_STORAGE_SIZE];



extern int trace_event_raw_init(struct ftrace_event_call *call);

extern int trace_define_field(struct ftrace_event_call *call, const char *type,

			      const char *name, int offset, int size,

include/trace/ftrace.h

+10 −4
Original line number Diff line number Diff line
@@ -296,13 +296,19 @@ static struct trace_event_functions ftrace_event_type_funcs_##call = { \ 


#undef __array

#define __array(type, item, len)					\

	do {								\

		mutex_lock(&event_storage_mutex);			\

		BUILD_BUG_ON(len > MAX_FILTER_STR_VAL);			\

	ret = trace_define_field(event_call, #type "[" #len "]", #item,	\

		snprintf(event_storage, sizeof(event_storage),		\

			 "%s[%d]", #type, len);				\

		ret = trace_define_field(event_call, event_storage, #item, \

				 offsetof(typeof(field), item),		\

				 sizeof(field.item),			\

				 is_signed_type(type), FILTER_OTHER);	\

		mutex_unlock(&event_storage_mutex);			\

		if (ret)						\

		return ret;

			return ret;					\

	} while (0);



#undef __dynamic_array

#define __dynamic_array(type, item, len)				       \

kernel/trace/trace_events.c

+6 −0
Original line number Diff line number Diff line
@@ -27,6 +27,12 @@ 


DEFINE_MUTEX(event_mutex);



DEFINE_MUTEX(event_storage_mutex);

EXPORT_SYMBOL_GPL(event_storage_mutex);



char event_storage[EVENT_STORAGE_SIZE];

EXPORT_SYMBOL_GPL(event_storage);



LIST_HEAD(ftrace_events);

LIST_HEAD(ftrace_common_fields);

kernel/trace/trace_export.c

+10 −4
Original line number Diff line number Diff line
@@ -83,13 +83,19 @@ static void __always_unused ____ftrace_check_##name(void) \ 


#undef __array

#define __array(type, item, len)					\

	do {								\

		BUILD_BUG_ON(len > MAX_FILTER_STR_VAL);			\

	ret = trace_define_field(event_call, #type "[" #len "]", #item,	\

		mutex_lock(&event_storage_mutex);			\

		snprintf(event_storage, sizeof(event_storage),		\

			 "%s[%d]", #type, len);				\

		ret = trace_define_field(event_call, event_storage, #item, \

				 offsetof(typeof(field), item),		\

				 sizeof(field.item),			\

				 is_signed_type(type), FILTER_OTHER);	\

		mutex_unlock(&event_storage_mutex);			\

		if (ret)						\

		return ret;

			return ret;					\

	} while (0);



#undef __array_desc

#define __array_desc(type, container, item, len)			\

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