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tracing/events: Show real number in array fields

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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: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2010-11-12 22:32:11 -05:00 committed by Steven Rostedt
parent 45677454dd
commit 0429578016
4 changed files with 30 additions and 8 deletions
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4
include/linux/ftrace_event.h
View file

@ -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,

14
include/trace/ftrace.h
View file

@ -296,13 +296,19 @@ static struct trace_event_functions ftrace_event_type_funcs_##call = { \
#undef __array
#define __array(type, item, len) \
BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \
ret = trace_define_field(event_call, #type "[" #len "]", #item, \
do { \
mutex_lock(&event_storage_mutex); \
BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \
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); \
if (ret) \
return ret;
mutex_unlock(&event_storage_mutex); \
if (ret) \
return ret; \
} while (0);
#undef __dynamic_array
#define __dynamic_array(type, item, len) \

6
kernel/trace/trace_events.c
View file

@ -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);

14
kernel/trace/trace_export.c
View file

@ -83,13 +83,19 @@ static void __always_unused ____ftrace_check_##name(void) \
#undef __array
#define __array(type, item, len) \
BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \
ret = trace_define_field(event_call, #type "[" #len "]", #item, \
do { \
BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \
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); \
if (ret) \
return ret;
mutex_unlock(&event_storage_mutex); \
if (ret) \
return ret; \
} while (0);
#undef __array_desc
#define __array_desc(type, container, item, len) \