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Commit 7fcb7c47 authored by Li Zefan's avatar Li Zefan Committed by Steven Rostedt
Browse files

tracing/events: introduce __dynamic_array() 



__string() is limited:

  - it's a char array, but we may want to define array with other types
  - a source string should be available, but we may just know the string size

We introduce __dynamic_array() to break those limitations, and __string()
becomes a wrapper of it. As a side effect, now __get_str() can be used
in TP_fast_assign but not only TP_print.

Take XFS for example, we have the string length in the dirent, but the
string itself is not NULL-terminated, so __dynamic_array() can be used:

TRACE_EVENT(xfs_dir2,
	TP_PROTO(struct xfs_da_args *args),
	TP_ARGS(args),

	TP_STRUCT__entry(
		__field(int, namelen)
		__dynamic_array(char, name, args->namelen + 1)
		...
	),

	TP_fast_assign(
		char *name = __get_str(name);

		if (args->namelen)
			memcpy(name, args->name, args->namelen);
		name[args->namelen] = '\0';

		__entry->namelen = args->namelen;
	),

	TP_printk("name %.*s namelen %d",
		  __entry->namelen ? __get_str(name) : NULL
		  __entry->namelen)
);

[ Impact: allow defining dynamic size arrays ]

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2384D2.3080403@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent a9c1c3ab

include/trace/ftrace.h

+88 −34
Original line number Diff line number Diff line
@@ -18,14 +18,17 @@ 


#include <linux/ftrace_event.h>



#undef __field

#define __field(type, item)		type	item;



#undef __array

#define __array(type, item, len)	type	item[len];



#undef __field

#define __field(type, item)		type	item;

#undef __dynamic_array

#define __dynamic_array(type, item, len) unsigned short __data_loc_##item;



#undef __string

#define __string(item, src)		unsigned short	__str_loc_##item;

#define __string(item, src) __dynamic_array(char, item, -1)



#undef TP_STRUCT__entry

#define TP_STRUCT__entry(args...) args
@@ -35,7 +38,7 @@ 
	struct ftrace_raw_##name {				\

		struct trace_entry	ent;			\

		tstruct						\

		char			__str_data[0];		\

		char			__data[0];		\

	};							\

	static struct ftrace_event_call event_##name
@@ -47,30 +50,31 @@ 
 *

 * Include the following:

 *

 * struct ftrace_str_offsets_<call> {

 *	int				<str1>;

 *	int				<str2>;

 * struct ftrace_data_offsets_<call> {

 *	int				<item1>;

 *	int				<item2>;

 *	[...]

 * };

 *

 * The __string() macro will create each int <str>, this is to

 * keep the offset of each string from the beggining of the event

 * once we perform the strlen() of the src strings.

 *

 * The __dynamic_array() macro will create each int <item>, this is

 * to keep the offset of each array from the beginning of the event.

 */



#undef __field

#define __field(type, item);



#undef __array

#define __array(type, item, len)



#undef __field

#define __field(type, item);

#undef __dynamic_array

#define __dynamic_array(type, item, len)	int item;



#undef __string

#define __string(item, src)	int item;

#define __string(item, src) __dynamic_array(char, item, -1)



#undef TRACE_EVENT

#define TRACE_EVENT(call, proto, args, tstruct, assign, print)		\

	struct ftrace_str_offsets_##call {				\

	struct ftrace_data_offsets_##call {				\

		tstruct;						\

	};
@@ -119,8 +123,12 @@ 
#undef TP_printk

#define TP_printk(fmt, args...) fmt "\n", args



#undef __get_dynamic_array

#define __get_dynamic_array(field)	\

		((void *)__entry + __entry->__data_loc_##field)



#undef __get_str

#define __get_str(field)	((char *)__entry + __entry->__str_loc_##field)

#define __get_str(field) (char *)__get_dynamic_array(field)



#undef __print_flags

#define __print_flags(flag, delim, flag_array...)			\
@@ -207,16 +215,19 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ 
	if (!ret)							\

		return 0;



#undef __string

#define __string(item, src)						       \

	ret = trace_seq_printf(s, "\tfield:__str_loc " #item ";\t"	       \

#undef __dynamic_array

#define __dynamic_array(type, item, len)				       \

	ret = trace_seq_printf(s, "\tfield:__data_loc " #item ";\t"	       \

			       "offset:%u;\tsize:%u;\n",		       \

			       (unsigned int)offsetof(typeof(field),	       \

					__str_loc_##item),		       \

			       (unsigned int)sizeof(field.__str_loc_##item));  \

					__data_loc_##item),		       \

			       (unsigned int)sizeof(field.__data_loc_##item)); \

	if (!ret)							       \

		return 0;



#undef __string

#define __string(item, src) __dynamic_array(char, item, -1)



#undef __entry

#define __entry REC
@@ -260,11 +271,14 @@ ftrace_format_##call(struct trace_seq *s) \ 
	if (ret)							\

		return ret;



#undef __dynamic_array

#define __dynamic_array(type, item, len)				       \

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

				offsetof(typeof(field), __data_loc_##item),    \

				 sizeof(field.__data_loc_##item), 0);



#undef __string

#define __string(item, src)						       \

	ret = trace_define_field(event_call, "__str_loc", #item,	       \

				offsetof(typeof(field), __str_loc_##item),     \

				 sizeof(field.__str_loc_##item), 0);

#define __string(item, src) __dynamic_array(char, item, -1)



#undef TRACE_EVENT

#define TRACE_EVENT(call, proto, args, tstruct, func, print)		\
@@ -288,6 +302,43 @@ ftrace_define_fields_##call(void) \ 


#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)



/*

 * remember the offset of each array from the beginning of the event.

 */



#undef __entry

#define __entry entry



#undef __field

#define __field(type, item)



#undef __array

#define __array(type, item, len)



#undef __dynamic_array

#define __dynamic_array(type, item, len)				\

	__data_offsets->item = __data_size +				\

			       offsetof(typeof(*entry), __data);	\

	__data_size += (len) * sizeof(type);



#undef __string

#define __string(item, src) __dynamic_array(char, item, strlen(src) + 1)       \



#undef TRACE_EVENT

#define TRACE_EVENT(call, proto, args, tstruct, assign, print)		\

static inline int ftrace_get_offsets_##call(				\

	struct ftrace_data_offsets_##call *__data_offsets, proto)       \

{									\

	int __data_size = 0;						\

	struct ftrace_raw_##call __maybe_unused *entry;			\

									\

	tstruct;							\

									\

	return __data_size;						\

}



#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)



/*

 * Stage 4 of the trace events.

 *
@@ -432,15 +483,15 @@ static void ftrace_profile_disable_##call(struct ftrace_event_call *event_call)\ 
#undef __array

#define __array(type, item, len)



#undef __dynamic_array

#define __dynamic_array(type, item, len)				\

	__entry->__data_loc_##item = __data_offsets.item;



#undef __string

#define __string(item, src)						\

	__str_offsets.item = __str_size +				\

			     offsetof(typeof(*entry), __str_data);	\

	__str_size += strlen(src) + 1;

#define __string(item, src) __dynamic_array(char, item, -1)       	\



#undef __assign_str

#define __assign_str(dst, src)						\

	__entry->__str_loc_##dst = __str_offsets.dst;			\

	strcpy(__get_str(dst), src);



#undef TRACE_EVENT
@@ -451,26 +502,29 @@ static struct ftrace_event_call event_##call; \ 
									\

static void ftrace_raw_event_##call(proto)				\

{									\

	struct ftrace_str_offsets_##call __maybe_unused __str_offsets;	\

	struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\

	struct ftrace_event_call *event_call = &event_##call;		\

	struct ring_buffer_event *event;				\

	struct ftrace_raw_##call *entry;				\

	unsigned long irq_flags;					\

	int __str_size = 0;						\

	int __data_size;						\

	int pc;								\

									\

	local_save_flags(irq_flags);					\

	pc = preempt_count();						\

									\

	tstruct;							\

	__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \

									\

	event = trace_current_buffer_lock_reserve(event_##call.id,	\

				 sizeof(struct ftrace_raw_##call) + __str_size,\

				 sizeof(*entry) + __data_size,		\

				 irq_flags, pc);			\

	if (!event)							\

		return;							\

	entry	= ring_buffer_event_data(event);			\

									\

									\

	tstruct								\

									\

	{ assign; }							\

									\

	if (!filter_current_check_discard(event_call, entry, event))	\

kernel/trace/trace_events_filter.c

+3 −3
Original line number Diff line number Diff line
@@ -478,12 +478,12 @@ enum { 


static int is_string_field(const char *type)

{

	if (strstr(type, "__data_loc") && strstr(type, "char"))

		return FILTER_DYN_STRING;



	if (strchr(type, '[') && strstr(type, "char"))

		return FILTER_STATIC_STRING;



	if (!strcmp(type, "__str_loc"))

		return FILTER_DYN_STRING;



	return 0;

}