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tracing: Add synth_event_trace() and related functions

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Add an exported function named synth_event_trace(), allowing modules
or other kernel code to trace synthetic events.

Also added are several functions that allow the same functionality to
be broken out in a piecewise fashion, which are useful in situations
where tracing an event from a full array of values would be
cumbersome.  Those functions are synth_event_trace_start/end() and
synth_event_add_(next)_val().

Link: http://lkml.kernel.org/r/7a84de5f1854acf4144b57efe835ca645afa764f.1580323897.git.zanussi@kernel.org

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2020-01-29 12:59:27 -06:00 committed by Steven Rostedt (VMware)
parent 35ca5207c2
commit 8dcc53ad95
2 changed files with 489 additions and 0 deletions
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26
include/linux/trace_events.h
View File

@ -416,6 +416,32 @@ extern int synth_event_add_fields(struct dynevent_cmd *cmd,
#define synth_event_gen_cmd_end(cmd) \
dynevent_create(cmd)
struct synth_event;
struct synth_event_trace_state {
struct trace_event_buffer fbuffer;
struct synth_trace_event *entry;
struct trace_buffer *buffer;
struct synth_event *event;
unsigned int cur_field;
unsigned int n_u64;
bool enabled;
bool add_next;
bool add_name;
};
extern int synth_event_trace(struct trace_event_file *file,
unsigned int n_vals, ...);
extern int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
unsigned int n_vals);
extern int synth_event_trace_start(struct trace_event_file *file,
struct synth_event_trace_state *trace_state);
extern int synth_event_add_next_val(u64 val,
struct synth_event_trace_state *trace_state);
extern int synth_event_add_val(const char *field_name, u64 val,
struct synth_event_trace_state *trace_state);
extern int synth_event_trace_end(struct synth_event_trace_state *trace_state);
/*
* Event file flags:
* ENABLED - The event is enabled

463
kernel/trace/trace_events_hist.c
View File

@ -398,6 +398,7 @@ struct synth_field {
char *type;
char *name;
size_t size;
unsigned int offset;
bool is_signed;
bool is_string;
};
@ -668,6 +669,8 @@ static int synth_event_define_fields(struct trace_event_call *call)
if (ret)
break;
event->fields[i]->offset = n_u64;
if (event->fields[i]->is_string) {
offset += STR_VAR_LEN_MAX;
n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
@ -1791,6 +1794,466 @@ void synth_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
}
EXPORT_SYMBOL_GPL(synth_event_cmd_init);
/**
* synth_event_trace - Trace a synthetic event
* @file: The trace_event_file representing the synthetic event
* @n_vals: The number of values in vals
* @args: Variable number of args containing the event values
*
* Trace a synthetic event using the values passed in the variable
* argument list.
*
* The argument list should be a list 'n_vals' u64 values. The number
* of vals must match the number of field in the synthetic event, and
* must be in the same order as the synthetic event fields.
*
* All vals should be cast to u64, and string vals are just pointers
* to strings, cast to u64. Strings will be copied into space
* reserved in the event for the string, using these pointers.
*
* Return: 0 on success, err otherwise.
*/
int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
{
struct trace_event_buffer fbuffer;
struct synth_trace_event *entry;
struct trace_buffer *buffer;
struct synth_event *event;
unsigned int i, n_u64;
int fields_size = 0;
va_list args;
int ret = 0;
/*
* Normal event generation doesn't get called at all unless
* the ENABLED bit is set (which attaches the probe thus
* allowing this code to be called, etc). Because this is
* called directly by the user, we don't have that but we
* still need to honor not logging when disabled.
*/
if (!(file->flags & EVENT_FILE_FL_ENABLED))
return 0;
event = file->event_call->data;
if (n_vals != event->n_fields)
return -EINVAL;
if (trace_trigger_soft_disabled(file))
return -EINVAL;
fields_size = event->n_u64 * sizeof(u64);
/*
* Avoid ring buffer recursion detection, as this event
* is being performed within another event.
*/
buffer = file->tr->array_buffer.buffer;
ring_buffer_nest_start(buffer);
entry = trace_event_buffer_reserve(&fbuffer, file,
sizeof(*entry) + fields_size);
if (!entry) {
ret = -EINVAL;
goto out;
}
va_start(args, n_vals);
for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
u64 val;
val = va_arg(args, u64);
if (event->fields[i]->is_string) {
char *str_val = (char *)(long)val;
char *str_field = (char *)&entry->fields[n_u64];
strscpy(str_field, str_val, STR_VAR_LEN_MAX);
n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
} else {
entry->fields[n_u64] = val;
n_u64++;
}
}
va_end(args);
trace_event_buffer_commit(&fbuffer);
out:
ring_buffer_nest_end(buffer);
return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace);
/**
* synth_event_trace_array - Trace a synthetic event from an array
* @file: The trace_event_file representing the synthetic event
* @vals: Array of values
* @n_vals: The number of values in vals
*
* Trace a synthetic event using the values passed in as 'vals'.
*
* The 'vals' array is just an array of 'n_vals' u64. The number of
* vals must match the number of field in the synthetic event, and
* must be in the same order as the synthetic event fields.
*
* All vals should be cast to u64, and string vals are just pointers
* to strings, cast to u64. Strings will be copied into space
* reserved in the event for the string, using these pointers.
*
* Return: 0 on success, err otherwise.
*/
int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
unsigned int n_vals)
{
struct trace_event_buffer fbuffer;
struct synth_trace_event *entry;
struct trace_buffer *buffer;
struct synth_event *event;
unsigned int i, n_u64;
int fields_size = 0;
int ret = 0;
/*
* Normal event generation doesn't get called at all unless
* the ENABLED bit is set (which attaches the probe thus
* allowing this code to be called, etc). Because this is
* called directly by the user, we don't have that but we
* still need to honor not logging when disabled.
*/
if (!(file->flags & EVENT_FILE_FL_ENABLED))
return 0;
event = file->event_call->data;
if (n_vals != event->n_fields)
return -EINVAL;
if (trace_trigger_soft_disabled(file))
return -EINVAL;
fields_size = event->n_u64 * sizeof(u64);
/*
* Avoid ring buffer recursion detection, as this event
* is being performed within another event.
*/
buffer = file->tr->array_buffer.buffer;
ring_buffer_nest_start(buffer);
entry = trace_event_buffer_reserve(&fbuffer, file,
sizeof(*entry) + fields_size);
if (!entry) {
ret = -EINVAL;
goto out;
}
for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
if (event->fields[i]->is_string) {
char *str_val = (char *)(long)vals[i];
char *str_field = (char *)&entry->fields[n_u64];
strscpy(str_field, str_val, STR_VAR_LEN_MAX);
n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
} else {
entry->fields[n_u64] = vals[i];
n_u64++;
}
}
trace_event_buffer_commit(&fbuffer);
out:
ring_buffer_nest_end(buffer);
return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace_array);
/**
* synth_event_trace_start - Start piecewise synthetic event trace
* @file: The trace_event_file representing the synthetic event
* @trace_state: A pointer to object tracking the piecewise trace state
*
* Start the trace of a synthetic event field-by-field rather than all
* at once.
*
* This function 'opens' an event trace, which means space is reserved
* for the event in the trace buffer, after which the event's
* individual field values can be set through either
* synth_event_add_next_val() or synth_event_add_val().
*
* A pointer to a trace_state object is passed in, which will keep
* track of the current event trace state until the event trace is
* closed (and the event finally traced) using
* synth_event_trace_end().
*
* Note that synth_event_trace_end() must be called after all values
* have been added for each event trace, regardless of whether adding
* all field values succeeded or not.
*
* Note also that for a given event trace, all fields must be added
* using either synth_event_add_next_val() or synth_event_add_val()
* but not both together or interleaved.
*
* Return: 0 on success, err otherwise.
*/
int synth_event_trace_start(struct trace_event_file *file,
struct synth_event_trace_state *trace_state)
{
struct synth_trace_event *entry;
int fields_size = 0;
int ret = 0;
if (!trace_state) {
ret = -EINVAL;
goto out;
}
memset(trace_state, '\0', sizeof(*trace_state));
/*
* Normal event tracing doesn't get called at all unless the
* ENABLED bit is set (which attaches the probe thus allowing
* this code to be called, etc). Because this is called
* directly by the user, we don't have that but we still need
* to honor not logging when disabled. For the the iterated
* trace case, we save the enabed state upon start and just
* ignore the following data calls.
*/
if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
trace_state->enabled = false;
goto out;
}
trace_state->enabled = true;
trace_state->event = file->event_call->data;
if (trace_trigger_soft_disabled(file)) {
ret = -EINVAL;
goto out;
}
fields_size = trace_state->event->n_u64 * sizeof(u64);
/*
* Avoid ring buffer recursion detection, as this event
* is being performed within another event.
*/
trace_state->buffer = file->tr->array_buffer.buffer;
ring_buffer_nest_start(trace_state->buffer);
entry = trace_event_buffer_reserve(&trace_state->fbuffer, file,
sizeof(*entry) + fields_size);
if (!entry) {
ret = -EINVAL;
goto out;
}
trace_state->entry = entry;
out:
return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace_start);
static int save_synth_val(struct synth_field *field, u64 val,
struct synth_event_trace_state *trace_state)
{
struct synth_trace_event *entry = trace_state->entry;
if (field->is_string) {
char *str_val = (char *)(long)val;
char *str_field;
if (!str_val)
return -EINVAL;
str_field = (char *)&entry->fields[field->offset];
strscpy(str_field, str_val, STR_VAR_LEN_MAX);
} else
entry->fields[field->offset] = val;
return 0;
}
/**
* synth_event_add_next_val - Add the next field's value to an open synth trace
* @val: The value to set the next field to
* @trace_state: A pointer to object tracking the piecewise trace state
*
* Set the value of the next field in an event that's been opened by
* synth_event_trace_start().
*
* The val param should be the value cast to u64. If the value points
* to a string, the val param should be a char * cast to u64.
*
* This function assumes all the fields in an event are to be set one
* after another - successive calls to this function are made, one for
* each field, in the order of the fields in the event, until all
* fields have been set. If you'd rather set each field individually
* without regard to ordering, synth_event_add_val() can be used
* instead.
*
* Note however that synth_event_add_next_val() and
* synth_event_add_val() can't be intermixed for a given event trace -
* one or the other but not both can be used at the same time.
*
* Note also that synth_event_trace_end() must be called after all
* values have been added for each event trace, regardless of whether
* adding all field values succeeded or not.
*
* Return: 0 on success, err otherwise.
*/
int synth_event_add_next_val(u64 val,
struct synth_event_trace_state *trace_state)
{
struct synth_field *field;
struct synth_event *event;
int ret = 0;
if (!trace_state) {
ret = -EINVAL;
goto out;
}
/* can't mix add_next_synth_val() with add_synth_val() */
if (trace_state->add_name) {
ret = -EINVAL;
goto out;
}
trace_state->add_next = true;
if (!trace_state->enabled)
goto out;
event = trace_state->event;
if (trace_state->cur_field >= event->n_fields) {
ret = -EINVAL;
goto out;
}
field = event->fields[trace_state->cur_field++];
ret = save_synth_val(field, val, trace_state);
out:
return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_next_val);
static struct synth_field *find_synth_field(struct synth_event *event,
const char *field_name)
{
struct synth_field *field = NULL;
unsigned int i;
for (i = 0; i < event->n_fields; i++) {
field = event->fields[i];
if (strcmp(field->name, field_name) == 0)
return field;
}
return NULL;
}
/**
* synth_event_add_val - Add a named field's value to an open synth trace
* @field_name: The name of the synthetic event field value to set
* @val: The value to set the next field to
* @trace_state: A pointer to object tracking the piecewise trace state
*
* Set the value of the named field in an event that's been opened by
* synth_event_trace_start().
*
* The val param should be the value cast to u64. If the value points
* to a string, the val param should be a char * cast to u64.
*
* This function looks up the field name, and if found, sets the field
* to the specified value. This lookup makes this function more
* expensive than synth_event_add_next_val(), so use that or the
* none-piecewise synth_event_trace() instead if efficiency is more
* important.
*
* Note however that synth_event_add_next_val() and
* synth_event_add_val() can't be intermixed for a given event trace -
* one or the other but not both can be used at the same time.
*
* Note also that synth_event_trace_end() must be called after all
* values have been added for each event trace, regardless of whether
* adding all field values succeeded or not.
*
* Return: 0 on success, err otherwise.
*/
int synth_event_add_val(const char *field_name, u64 val,
struct synth_event_trace_state *trace_state)
{
struct synth_trace_event *entry;
struct synth_event *event;
struct synth_field *field;
int ret = 0;
if (!trace_state) {
ret = -EINVAL;
goto out;
}
/* can't mix add_next_synth_val() with add_synth_val() */
if (trace_state->add_next) {
ret = -EINVAL;
goto out;
}
trace_state->add_name = true;
if (!trace_state->enabled)
goto out;
event = trace_state->event;
entry = trace_state->entry;
field = find_synth_field(event, field_name);
if (!field) {
ret = -EINVAL;
goto out;
}
ret = save_synth_val(field, val, trace_state);
out:
return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_val);
/**
* synth_event_trace_end - End piecewise synthetic event trace
* @trace_state: A pointer to object tracking the piecewise trace state
*
* End the trace of a synthetic event opened by
* synth_event_trace__start().
*
* This function 'closes' an event trace, which basically means that
* it commits the reserved event and cleans up other loose ends.
*
* A pointer to a trace_state object is passed in, which will keep
* track of the current event trace state opened with
* synth_event_trace_start().
*
* Note that this function must be called after all values have been
* added for each event trace, regardless of whether adding all field
* values succeeded or not.
*
* Return: 0 on success, err otherwise.
*/
int synth_event_trace_end(struct synth_event_trace_state *trace_state)
{
if (!trace_state)
return -EINVAL;
trace_event_buffer_commit(&trace_state->fbuffer);
ring_buffer_nest_end(trace_state->buffer);
return 0;
}
EXPORT_SYMBOL_GPL(synth_event_trace_end);
static int create_synth_event(int argc, const char **argv)
{
const char *name = argv[0];