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Subject[PATCH 7/7] ftrace, perf: Add filter support for function trace event
Date
Adding support to filter function trace event via perf
interface. It is now possible to use filter interface
in the perf tool like:

perf record -e ftrace:function --filter="(ip == mm_*)" ls

The filter syntax is restricted to the the 'ip' field only,
and following operators are accepted '==' '!=' '||', ending
up with the filter strings like:

"ip == f1 f2 ..." || "ip != f3 f4 ..." ...

The '==' operator adds trace filter with same effect as would
be added via set_ftrace_filter file.

The '!=' operator adds trace filter with same effect as would
be added via set_ftrace_notrace file.

The right side of the '!=', '==' operators is list of functions
or regexp. to be added to filter separated by space. Same syntax
is supported/required as for the set_ftrace_filter and
set_ftrace_notrace files.

The '||' operator is used for connecting multiple filter definitions
together. It is possible to have more than one '==' and '!='
operators within one filter string.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
---
kernel/trace/trace.h | 2 -
kernel/trace/trace_events_filter.c | 113 +++++++++++++++++++++++++++++++++---
2 files changed, 105 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index e88e58a..4ec6d18 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -770,9 +770,7 @@ struct filter_pred {
u64 val;
struct regex regex;
unsigned short *ops;
-#ifdef CONFIG_FTRACE_STARTUP_TEST
struct ftrace_event_field *field;
-#endif
int offset;
int not;
int op;
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 66b74ab..600bb1e 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -54,6 +54,13 @@ struct filter_op {
int precedence;
};

+static struct filter_op filter_ftrace_ops[] = {
+ { OP_OR, "||", 1 },
+ { OP_NE, "!=", 2 },
+ { OP_EQ, "==", 2 },
+ { OP_NONE, "OP_NONE", 0 },
+};
+
static struct filter_op filter_ops[] = {
{ OP_OR, "||", 1 },
{ OP_AND, "&&", 2 },
@@ -81,6 +88,7 @@ enum {
FILT_ERR_TOO_MANY_PREDS,
FILT_ERR_MISSING_FIELD,
FILT_ERR_INVALID_FILTER,
+ FILT_ERR_IP_FIELD_ONLY,
};

static char *err_text[] = {
@@ -96,6 +104,7 @@ static char *err_text[] = {
"Too many terms in predicate expression",
"Missing field name and/or value",
"Meaningless filter expression",
+ "Only 'ip' field is supported for function trace",
};

struct opstack_op {
@@ -992,7 +1001,12 @@ static int init_pred(struct filter_parse_state *ps,
fn = filter_pred_strloc;
else
fn = filter_pred_pchar;
- } else if (!is_function_field(field)) {
+ } else if (is_function_field(field)) {
+ if (strcmp(field->name, "ip")) {
+ parse_error(ps, FILT_ERR_IP_FIELD_ONLY, 0);
+ return -EINVAL;
+ }
+ } else {
if (field->is_signed)
ret = strict_strtoll(pred->regex.pattern, 0, &val);
else
@@ -1339,10 +1353,8 @@ static struct filter_pred *create_pred(struct filter_parse_state *ps,

strcpy(pred.regex.pattern, operand2);
pred.regex.len = strlen(pred.regex.pattern);
-
-#ifdef CONFIG_FTRACE_STARTUP_TEST
pred.field = field;
-#endif
+
return init_pred(ps, field, &pred) ? NULL : &pred;
}

@@ -1894,6 +1906,83 @@ void ftrace_profile_free_filter(struct perf_event *event)
__free_filter(filter);
}

+struct function_filter_data {
+ struct ftrace_ops *ops;
+ int first_filter;
+ int first_notrace;
+};
+
+static int __ftrace_function_set_filter(int filter, char *buf, int len,
+ struct function_filter_data *data)
+{
+ int *reset, ret;
+
+ reset = filter ? &data->first_filter : &data->first_notrace;
+
+ if (filter)
+ ret = ftrace_set_filter(data->ops, buf, len, *reset);
+ else
+ ret = ftrace_set_notrace(data->ops, buf, len, *reset);
+
+ if (*reset)
+ *reset = 0;
+
+ return ret;
+}
+
+static int ftrace_function_check_pred(struct filter_pred *pred)
+{
+ struct ftrace_event_field *field = pred->field;
+
+ /*
+ Check the predicate for function trace, verify:
+ - only '==' and '!=' is used
+ - the 'ip' field is used
+ */
+ if (WARN((pred->op != OP_EQ) && (pred->op != OP_NE),
+ "wrong operator for function filter: %d\n", pred->op))
+ return -EINVAL;
+
+ if (strcmp(field->name, "ip"))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int ftrace_function_set_filter_cb(enum move_type move,
+ struct filter_pred *pred,
+ int *err, void *data)
+{
+ if ((move != MOVE_DOWN) ||
+ (pred->left != FILTER_PRED_INVALID))
+ return WALK_PRED_DEFAULT;
+
+ /* Double checking the predicate is valid for function trace. */
+ *err = ftrace_function_check_pred(pred);
+ if (*err)
+ return WALK_PRED_ABORT;
+
+ *err = __ftrace_function_set_filter(pred->op == OP_EQ,
+ pred->regex.pattern,
+ pred->regex.len,
+ data);
+
+ return (*err) ? WALK_PRED_ABORT : WALK_PRED_DEFAULT;
+}
+
+static int ftrace_function_set_filter(struct perf_event *event,
+ struct event_filter *filter)
+{
+ struct function_filter_data data = {
+ .first_filter = 1,
+ .first_notrace = 1,
+ .ops = &event->ftrace_ops,
+ };
+
+ return walk_pred_tree(filter->preds, filter->root,
+ ftrace_function_set_filter_cb, &data);
+}
+
int ftrace_profile_set_filter(struct perf_event *event, int event_id,
char *filter_str)
{
@@ -1901,6 +1990,7 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
struct event_filter *filter;
struct filter_parse_state *ps;
struct ftrace_event_call *call;
+ struct filter_op *fops = filter_ops;

mutex_lock(&event_mutex);

@@ -1925,14 +2015,21 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
if (!ps)
goto free_filter;

- parse_init(ps, filter_ops, filter_str);
+ if (ftrace_event_is_function(call))
+ fops = filter_ftrace_ops;
+
+ parse_init(ps, fops, filter_str);
err = filter_parse(ps);
if (err)
goto free_ps;

err = replace_preds(call, filter, ps, filter_str, false);
- if (!err)
- event->filter = filter;
+ if (!err) {
+ if (ftrace_event_is_function(call))
+ err = ftrace_function_set_filter(event, filter);
+ else
+ event->filter = filter;
+ }

free_ps:
filter_opstack_clear(ps);
@@ -1940,7 +2037,7 @@ free_ps:
kfree(ps);

free_filter:
- if (err)
+ if (err || ftrace_event_is_function(call))
__free_filter(filter);

out_unlock:
--
1.7.1


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