[PATCH 28/32] tracing: Add hist trigger support for variable reference aliases

Tom Zanussi
2017-06-26T22:51:32Z

Add support for alias=$somevar where alias can be used as
onmatch($alias).

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
kernel/trace/trace_events_hist.c | 46 +++++++++++++++++++++++++++++++++++++---
1 file changed, 43 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 904a635..799b95e 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -225,6 +225,7 @@ enum hist_field_flags {
HIST_FIELD_FL_EXPR = 16384,
HIST_FIELD_FL_VAR_REF = 32768,
HIST_FIELD_FL_CPU = 65536,
+ HIST_FIELD_FL_ALIAS = 131072,
};

struct hist_trigger_attrs {
@@ -1414,7 +1415,8 @@ static const char *hist_field_name(struct hist_field *field,

if (field->field)
field_name = field->field->name;
- else if (field->flags & HIST_FIELD_FL_LOG2)
+ else if (field->flags & HIST_FIELD_FL_LOG2 ||
+ field->flags & HIST_FIELD_FL_ALIAS)
field_name = hist_field_name(field->operands[0], ++level);
else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
field_name = "$common_timestamp";
@@ -1819,7 +1821,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,

hist_field->hist_data = hist_data;

- if (flags & HIST_FIELD_FL_EXPR)
+ if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS)
goto out; /* caller will populate */

if (flags & HIST_FIELD_FL_VAR_REF) {
@@ -2013,6 +2015,34 @@ static struct hist_field *parse_var_ref(char *system, char *event_name,
return field;
}

+static struct hist_field *create_alias(struct hist_trigger_data *hist_data,
+ struct hist_field *var_ref,
+ char *var_name)
+{
+ struct hist_field *alias = NULL;
+ unsigned long flags = HIST_FIELD_FL_ALIAS | HIST_FIELD_FL_VAR |
+ HIST_FIELD_FL_VAR_ONLY;
+
+ alias = create_hist_field(hist_data, NULL, flags, var_name);
+ if (!alias)
+ return NULL;
+
+ alias->fn = var_ref->fn;
+ alias->operands[0] = var_ref;
+ alias->var.idx = var_ref->var.idx;
+ alias->var.hist_data = var_ref->hist_data;
+ alias->size = var_ref->size;
+ alias->is_signed = var_ref->is_signed;
+ alias->type = kstrdup(var_ref->type, GFP_KERNEL);
+ if (!alias->type) {
+ kfree(alias->type);
+ destroy_hist_field(alias, 0);
+ return NULL;
+ }
+
+ return alias;
+}
+
struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
struct trace_event_file *file, char *str,
unsigned long *flags, char *var_name)
@@ -2036,6 +2066,13 @@ struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
if (hist_field) {
hist_data->var_refs[hist_data->n_var_refs] = hist_field;
hist_field->var_ref_idx = hist_data->n_var_refs++;
+ if (var_name) {
+ hist_field = create_alias(hist_data, hist_field, var_name);
+ if (!hist_field) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
return hist_field;
}

@@ -4152,8 +4189,11 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
seq_puts(m, "$common_timestamp");
else if (hist_field->flags & HIST_FIELD_FL_CPU)
seq_puts(m, "cpu");
- else if (field_name)
+ else if (field_name) {
+ if (hist_field->flags & HIST_FIELD_FL_ALIAS)
+ seq_putc(m, '$');
seq_printf(m, "%s", field_name);
+ }

if (hist_field->flags) {
const char *flags_str = get_hist_field_flags(hist_field);
--
1.9.3