[PATCH v13 15/29] tracing: Add hist trigger 'hex' modifier for displaying numeric fields

From: Tom Zanussi
Date: Thu Dec 10 2015 - 14:01:55 EST


Allow users to have numeric fields displayed as hex values in the
output by appending '.hex' to field names:

# echo hist:keys=aaa,bbb.hex:vals=ccc.hex ... \
[ if filter] > event/trigger

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Reviewed-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
kernel/trace/trace.c | 5 +++-
kernel/trace/trace_events_hist.c | 61 ++++++++++++++++++++++++++++++++++++----
2 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 037f6374..15eda83 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3843,7 +3843,10 @@ static const char readme_msg[] =
"\t used to specify more or fewer than the default 2048 entries\n"
"\t for the hashtable size.\n\n"
"\t Reading the 'hist' file for the event will dump the hash\n"
- "\t table in its entirety to stdout.\n\n"
+ "\t table in its entirety to stdout. The default format used to\n"
+ "\t display a given field can be modified by appending any of the\n"
+ "\t following modifiers to the field name, as applicable:\n\n"
+ "\t .hex display a number as a hex value\n\n"
"\t The 'pause' parameter can be used to pause an existing hist\n"
"\t trigger or to start a hist trigger but not log any events\n"
"\t until told to do so. 'continue' can be used to start or\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 2995849..5ced452 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -81,6 +81,7 @@ enum hist_field_flags {
HIST_FIELD_HITCOUNT = 1,
HIST_FIELD_KEY = 2,
HIST_FIELD_STRING = 4,
+ HIST_FIELD_HEX = 8,
};

struct hist_trigger_attrs {
@@ -299,9 +300,20 @@ static int create_val_field(struct hist_trigger_data *hist_data,
{
struct ftrace_event_field *field = NULL;
unsigned long flags = 0;
+ char *field_name;
int ret = 0;

- field = trace_find_event_field(file->event_call, field_str);
+ field_name = strsep(&field_str, ".");
+ if (field_str) {
+ if (!strcmp(field_str, "hex"))
+ flags |= HIST_FIELD_HEX;
+ else {
+ ret = -EINVAL;
+ goto out;
+ }
+ }
+
+ field = trace_find_event_field(file->event_call, field_name);
if (!field) {
ret = -EINVAL;
goto out;
@@ -364,11 +376,22 @@ static int create_key_field(struct hist_trigger_data *hist_data,
struct ftrace_event_field *field = NULL;
unsigned long flags = 0;
unsigned int key_size;
+ char *field_name;
int ret = 0;

flags |= HIST_FIELD_KEY;

- field = trace_find_event_field(file->event_call, field_str);
+ field_name = strsep(&field_str, ".");
+ if (field_str) {
+ if (!strcmp(field_str, "hex"))
+ flags |= HIST_FIELD_HEX;
+ else {
+ ret = -EINVAL;
+ goto out;
+ }
+ }
+
+ field = trace_find_event_field(file->event_call, field_name);
if (!field) {
ret = -EINVAL;
goto out;
@@ -698,7 +721,11 @@ hist_trigger_entry_print(struct seq_file *m,
if (i > hist_data->n_vals)
seq_puts(m, ", ");

- if (key_field->flags & HIST_FIELD_STRING) {
+ if (key_field->flags & HIST_FIELD_HEX) {
+ uval = *(u64 *)(key + key_field->offset);
+ seq_printf(m, "%s: %llx",
+ key_field->field->name, uval);
+ } else if (key_field->flags & HIST_FIELD_STRING) {
seq_printf(m, "%s: %-50s", key_field->field->name,
(char *)(key + key_field->offset));
} else {
@@ -714,9 +741,15 @@ hist_trigger_entry_print(struct seq_file *m,
tracing_map_read_sum(elt, HITCOUNT_IDX));

for (i = 1; i < hist_data->n_vals; i++) {
- seq_printf(m, " %s: %10llu",
- hist_data->fields[i]->field->name,
- tracing_map_read_sum(elt, i));
+ if (hist_data->fields[i]->flags & HIST_FIELD_HEX) {
+ seq_printf(m, " %s: %10llx",
+ hist_data->fields[i]->field->name,
+ tracing_map_read_sum(elt, i));
+ } else {
+ seq_printf(m, " %s: %10llu",
+ hist_data->fields[i]->field->name,
+ tracing_map_read_sum(elt, i));
+ }
}

seq_puts(m, "\n");
@@ -801,9 +834,25 @@ const struct file_operations event_hist_fops = {
.release = single_release,
};

+static const char *get_hist_field_flags(struct hist_field *hist_field)
+{
+ const char *flags_str = NULL;
+
+ if (hist_field->flags & HIST_FIELD_HEX)
+ flags_str = "hex";
+
+ return flags_str;
+}
+
static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
{
seq_printf(m, "%s", hist_field->field->name);
+ if (hist_field->flags) {
+ const char *flags_str = get_hist_field_flags(hist_field);
+
+ if (flags_str)
+ seq_printf(m, ".%s", flags_str);
+ }
}

static int event_hist_trigger_print(struct seq_file *m,
--
1.9.3

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