[RFC][PATCH 04/10] tracing: Add trace event accessor functions

[Tom Zanussi]

This adds a set of accessor functions for integer and string trace
event fields.  When a trace event field is defined, the appropriate
accessor function for that field is chosen and set; clients can access
it via the ftrace_event_field's 'accessor' field.

This code is moved directly from the hist triggers code and the hist
triggers fixed up to make use of it.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace_events.c      | 111 +++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace_events_hist.c | 103 ++++--------------------------------
 2 files changed, 121 insertions(+), 93 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 8b54f21..47cb12c 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -70,6 +70,115 @@ static int system_refcount_dec(struct event_subsystem *system)
 #define while_for_each_event_file()		\
 	}
 
+static u64 ftrace_event_field_fn_none(struct ftrace_event_field *field,
+				      void *event)
+{
+	return 0;
+}
+
+static u64 ftrace_event_field_fn_string(struct ftrace_event_field *field,
+					void *event)
+{
+	char *addr = (char *)(event + field->offset);
+
+	return (u64)(unsigned long)addr;
+}
+
+static u64 ftrace_event_field_fn_dynstring(struct ftrace_event_field *field,
+					   void *event)
+{
+	u32 str_item = *(u32 *)(event + field->offset);
+	int str_loc = str_item & 0xffff;
+	char *addr = (char *)(event + str_loc);
+
+	return (u64)(unsigned long)addr;
+}
+
+static u64 ftrace_event_field_fn_pstring(struct ftrace_event_field *field,
+					 void *event)
+{
+	char **addr = (char **)(event + field->offset);
+
+	return (u64)(unsigned long)*addr;
+}
+
+#define DEFINE_FTRACE_EVENT_FIELD_FN(type)			\
+static u64							\
+ftrace_event_field_fn_##type(struct ftrace_event_field *field,	\
+			     void *event)			\
+{								\
+	type *addr = (type *)(event + field->offset);		\
+								\
+	return (u64)*addr;					\
+}
+
+DEFINE_FTRACE_EVENT_FIELD_FN(s64);
+DEFINE_FTRACE_EVENT_FIELD_FN(u64);
+DEFINE_FTRACE_EVENT_FIELD_FN(s32);
+DEFINE_FTRACE_EVENT_FIELD_FN(u32);
+DEFINE_FTRACE_EVENT_FIELD_FN(s16);
+DEFINE_FTRACE_EVENT_FIELD_FN(u16);
+DEFINE_FTRACE_EVENT_FIELD_FN(s8);
+DEFINE_FTRACE_EVENT_FIELD_FN(u8);
+
+static ftrace_event_field_fn_t select_integer_accessor_fn(int field_size,
+							  int field_is_signed)
+{
+	ftrace_event_field_fn_t fn = NULL;
+
+	switch (field_size) {
+	case 8:
+		if (field_is_signed)
+			fn = ftrace_event_field_fn_s64;
+		else
+			fn = ftrace_event_field_fn_u64;
+		break;
+	case 4:
+		if (field_is_signed)
+			fn = ftrace_event_field_fn_s32;
+		else
+			fn = ftrace_event_field_fn_u32;
+		break;
+	case 2:
+		if (field_is_signed)
+			fn = ftrace_event_field_fn_s16;
+		else
+			fn = ftrace_event_field_fn_u16;
+		break;
+	case 1:
+		if (field_is_signed)
+			fn = ftrace_event_field_fn_s8;
+		else
+			fn = ftrace_event_field_fn_u8;
+		break;
+	}
+
+	return fn;
+}
+
+static void set_field_accessor(struct ftrace_event_field *field)
+{
+	field->accessor = ftrace_event_field_fn_none;
+
+	if (field && is_function_field(field))
+		return;
+
+	if (is_string_field(field)) {
+		if (field->filter_type == FILTER_STATIC_STRING)
+			field->accessor = ftrace_event_field_fn_string;
+		else if (field->filter_type == FILTER_DYN_STRING)
+			field->accessor = ftrace_event_field_fn_dynstring;
+		else
+			field->accessor = ftrace_event_field_fn_pstring;
+	} else {
+		ftrace_event_field_fn_t fn;
+
+		fn = select_integer_accessor_fn(field->size, field->is_signed);
+		if (fn)
+			field->accessor = fn;
+	}
+}
+
 static struct list_head *
 trace_get_fields(struct trace_event_call *event_call)
 {
@@ -131,6 +240,8 @@ static int __trace_define_field(struct list_head *head, const char *type,
 	field->size = size;
 	field->is_signed = is_signed;
 
+	set_field_accessor(field);
+
 	list_add(&field->link, head);
 
 	return 0;
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 6e12388..66ca35e 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -30,7 +30,7 @@ typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event);
 struct hist_field {
 	struct ftrace_event_field	*field;
 	unsigned long			flags;
-	hist_field_fn_t			fn;
+	hist_field_fn_t                 fn;
 	unsigned int			size;
 	unsigned int			offset;
 };
@@ -45,29 +45,6 @@ static u64 hist_field_counter(struct hist_field *field, void *event)
 	return 1;
 }
 
-static u64 hist_field_string(struct hist_field *hist_field, void *event)
-{
-	char *addr = (char *)(event + hist_field->field->offset);
-
-	return (u64)(unsigned long)addr;
-}
-
-static u64 hist_field_dynstring(struct hist_field *hist_field, void *event)
-{
-	u32 str_item = *(u32 *)(event + hist_field->field->offset);
-	int str_loc = str_item & 0xffff;
-	char *addr = (char *)(event + str_loc);
-
-	return (u64)(unsigned long)addr;
-}
-
-static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
-{
-	char **addr = (char **)(event + hist_field->field->offset);
-
-	return (u64)(unsigned long)*addr;
-}
-
 static u64 hist_field_log2(struct hist_field *hist_field, void *event)
 {
 	u64 val = *(u64 *)(event + hist_field->field->offset);
@@ -75,23 +52,6 @@ static u64 hist_field_log2(struct hist_field *hist_field, void *event)
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
-#define DEFINE_HIST_FIELD_FN(type)					\
-static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
-{									\
-	type *addr = (type *)(event + hist_field->field->offset);	\
-									\
-	return (u64)*addr;						\
-}
-
-DEFINE_HIST_FIELD_FN(s64);
-DEFINE_HIST_FIELD_FN(u64);
-DEFINE_HIST_FIELD_FN(s32);
-DEFINE_HIST_FIELD_FN(u32);
-DEFINE_HIST_FIELD_FN(s16);
-DEFINE_HIST_FIELD_FN(u16);
-DEFINE_HIST_FIELD_FN(s8);
-DEFINE_HIST_FIELD_FN(u8);
-
 #define for_each_hist_field(i, hist_data)	\
 	for (i = 0; i < hist_data->n_fields; i++)
 
@@ -146,40 +106,6 @@ struct hist_trigger_data {
 	struct tracing_map		*map;
 };
 
-static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
-{
-	hist_field_fn_t fn = NULL;
-
-	switch (field_size) {
-	case 8:
-		if (field_is_signed)
-			fn = hist_field_s64;
-		else
-			fn = hist_field_u64;
-		break;
-	case 4:
-		if (field_is_signed)
-			fn = hist_field_s32;
-		else
-			fn = hist_field_u32;
-		break;
-	case 2:
-		if (field_is_signed)
-			fn = hist_field_s16;
-		else
-			fn = hist_field_u16;
-		break;
-	case 1:
-		if (field_is_signed)
-			fn = hist_field_s8;
-		else
-			fn = hist_field_u8;
-		break;
-	}
-
-	return fn;
-}
-
 static int parse_map_size(char *str)
 {
 	unsigned long size, map_bits;
@@ -372,23 +298,8 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 		goto out;
 	}
 
-	if (is_string_field(field)) {
+	if (is_string_field(field))
 		flags |= HIST_FIELD_STRING;
-
-		if (field->filter_type == FILTER_STATIC_STRING)
-			hist_field->fn = hist_field_string;
-		else if (field->filter_type == FILTER_DYN_STRING)
-			hist_field->fn = hist_field_dynstring;
-		else
-			hist_field->fn = hist_field_pstring;
-	} else {
-		hist_field->fn = select_value_fn(field->size,
-						 field->is_signed);
-		if (!hist_field->fn) {
-			destroy_hist_field(hist_field);
-			return NULL;
-		}
-	}
  out:
 	hist_field->field = field;
 	hist_field->flags = flags;
@@ -828,7 +739,10 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 
 	for_each_hist_val_field(i, hist_data) {
 		hist_field = hist_data->fields[i];
-		hist_val = hist_field->fn(hist_field, rec);
+		if (hist_field->fn)
+			hist_val = hist_field->fn(hist_field, rec);
+		else
+			hist_val = hist_field->field->accessor(hist_field->field, rec);
 		tracing_map_update_sum(elt, i, hist_val);
 	}
 }
@@ -886,7 +800,10 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
 
 			key = entries;
 		} else {
-			field_contents = key_field->fn(key_field, rec);
+			if (key_field->fn)
+				field_contents = key_field->fn(key_field, rec);
+			else
+				field_contents = key_field->field->accessor(key_field->field, rec);
 			if (key_field->flags & HIST_FIELD_STRING) {
 				key = (void *)(unsigned long)field_contents;
 				use_compound_key = true;
-- 
1.9.3