Commit 2d19bd79 authored by Tom Zanussi's avatar Tom Zanussi Committed by Steven Rostedt (VMware)
Browse files

tracing: Add hist_debug trace event files for histogram debugging 

Add a new "hist_debug" file for each trace event, which when read will
dump out a bunch of internal details about the hist triggers defined
on that event.

This is normally off but can be enabled by saying 'y' to the new
CONFIG_HIST_TRIGGERS_DEBUG config option.

This is in support of the new Documentation file describing histogram
internals, Documentation/trace/histogram-design.rst, which was
requested by developers trying to understand the internals when
extending or making use of the hist triggers for higher-level tools.

The histogram-design.rst documentation refers to the hist_debug files
and demonstrates their use with output in the test examples.

Link: http://lkml.kernel.org/r/77914c22b0ba493d9783c53bbfbc6087d6a7e1b1.1585941485.git.zanussi@kernel.org



Signed-off-by: default avatarTom Zanussi <zanussi@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 16b585fe

kernel/trace/Kconfig

+23 −0
Original line number Diff line number Diff line
@@ -847,6 +847,29 @@ config KPROBE_EVENT_GEN_TEST 


	  If unsure, say N.



config HIST_TRIGGERS_DEBUG

	bool "Hist trigger debug support"

	depends on HIST_TRIGGERS

	help

          Add "hist_debug" file for each event, which when read will

          dump out a bunch of internal details about the hist triggers

          defined on that event.



          The hist_debug file serves a couple of purposes:



            - Helps developers verify that nothing is broken.



            - Provides educational information to support the details

              of the hist trigger internals as described by

              Documentation/trace/histogram-design.rst.



          The hist_debug output only covers the data structures

          related to the histogram definitions themselves and doesn't

          display the internals of map buckets or variable values of

          running histograms.



          If unsure, say N.



endif # FTRACE



endif # TRACING_SUPPORT

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -1661,6 +1661,7 @@ extern struct list_head ftrace_events; 


extern const struct file_operations event_trigger_fops;

extern const struct file_operations event_hist_fops;

extern const struct file_operations event_hist_debug_fops;

extern const struct file_operations event_inject_fops;



#ifdef CONFIG_HIST_TRIGGERS

kernel/trace/trace_events.c

+4 −0
Original line number Diff line number Diff line
@@ -2208,6 +2208,10 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file) 
#ifdef CONFIG_HIST_TRIGGERS

	trace_create_file("hist", 0444, file->dir, file,

			  &event_hist_fops);

#endif

#ifdef CONFIG_HIST_TRIGGERS_DEBUG

	trace_create_file("hist_debug", 0444, file->dir, file,

			  &event_hist_debug_fops);

#endif

	trace_create_file("format", 0444, file->dir, call,

			  &ftrace_event_format_fops);

kernel/trace/trace_events_hist.c

+273 −0
Original line number Diff line number Diff line
@@ -6478,6 +6478,279 @@ const struct file_operations event_hist_fops = { 
	.release = single_release,

};



#ifdef CONFIG_HIST_TRIGGERS_DEBUG

static void hist_field_debug_show_flags(struct seq_file *m,

					unsigned long flags)

{

	seq_puts(m, "      flags:\n");



	if (flags & HIST_FIELD_FL_KEY)

		seq_puts(m, "        HIST_FIELD_FL_KEY\n");

	else if (flags & HIST_FIELD_FL_HITCOUNT)

		seq_puts(m, "        VAL: HIST_FIELD_FL_HITCOUNT\n");

	else if (flags & HIST_FIELD_FL_VAR)

		seq_puts(m, "        HIST_FIELD_FL_VAR\n");

	else if (flags & HIST_FIELD_FL_VAR_REF)

		seq_puts(m, "        HIST_FIELD_FL_VAR_REF\n");

	else

		seq_puts(m, "        VAL: normal u64 value\n");



	if (flags & HIST_FIELD_FL_ALIAS)

		seq_puts(m, "        HIST_FIELD_FL_ALIAS\n");

}



static int hist_field_debug_show(struct seq_file *m,

				 struct hist_field *field, unsigned long flags)

{

	if ((field->flags & flags) != flags) {

		seq_printf(m, "ERROR: bad flags - %lx\n", flags);

		return -EINVAL;

	}



	hist_field_debug_show_flags(m, field->flags);

	if (field->field)

		seq_printf(m, "      ftrace_event_field name: %s\n",

			   field->field->name);



	if (field->flags & HIST_FIELD_FL_VAR) {

		seq_printf(m, "      var.name: %s\n", field->var.name);

		seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",

			   field->var.idx);

	}



	if (field->flags & HIST_FIELD_FL_ALIAS)

		seq_printf(m, "      var_ref_idx (into hist_data->var_refs[]): %u\n",

			   field->var_ref_idx);



	if (field->flags & HIST_FIELD_FL_VAR_REF) {

		seq_printf(m, "      name: %s\n", field->name);

		seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",

			   field->var.idx);

		seq_printf(m, "      var.hist_data: %p\n", field->var.hist_data);

		seq_printf(m, "      var_ref_idx (into hist_data->var_refs[]): %u\n",

			   field->var_ref_idx);

		if (field->system)

			seq_printf(m, "      system: %s\n", field->system);

		if (field->event_name)

			seq_printf(m, "      event_name: %s\n", field->event_name);

	}



	seq_printf(m, "      type: %s\n", field->type);

	seq_printf(m, "      size: %u\n", field->size);

	seq_printf(m, "      is_signed: %u\n", field->is_signed);



	return 0;

}



static int field_var_debug_show(struct seq_file *m,

				struct field_var *field_var, unsigned int i,

				bool save_vars)

{

	const char *vars_name = save_vars ? "save_vars" : "field_vars";

	struct hist_field *field;

	int ret = 0;



	seq_printf(m, "\n    hist_data->%s[%d]:\n", vars_name, i);



	field = field_var->var;



	seq_printf(m, "\n      %s[%d].var:\n", vars_name, i);



	hist_field_debug_show_flags(m, field->flags);

	seq_printf(m, "      var.name: %s\n", field->var.name);

	seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",

		   field->var.idx);



	field = field_var->val;



	seq_printf(m, "\n      %s[%d].val:\n", vars_name, i);

	if (field->field)

		seq_printf(m, "      ftrace_event_field name: %s\n",

			   field->field->name);

	else {

		ret = -EINVAL;

		goto out;

	}



	seq_printf(m, "      type: %s\n", field->type);

	seq_printf(m, "      size: %u\n", field->size);

	seq_printf(m, "      is_signed: %u\n", field->is_signed);

out:

	return ret;

}



static int hist_action_debug_show(struct seq_file *m,

				  struct action_data *data, int i)

{

	int ret = 0;



	if (data->handler == HANDLER_ONMAX ||

	    data->handler == HANDLER_ONCHANGE) {

		seq_printf(m, "\n    hist_data->actions[%d].track_data.var_ref:\n", i);

		ret = hist_field_debug_show(m, data->track_data.var_ref,

					    HIST_FIELD_FL_VAR_REF);

		if (ret)

			goto out;



		seq_printf(m, "\n    hist_data->actions[%d].track_data.track_var:\n", i);

		ret = hist_field_debug_show(m, data->track_data.track_var,

					    HIST_FIELD_FL_VAR);

		if (ret)

			goto out;

	}



	if (data->handler == HANDLER_ONMATCH) {

		seq_printf(m, "\n    hist_data->actions[%d].match_data.event_system: %s\n",

			   i, data->match_data.event_system);

		seq_printf(m, "    hist_data->actions[%d].match_data.event: %s\n",

			   i, data->match_data.event);

	}

out:

	return ret;

}



static int hist_actions_debug_show(struct seq_file *m,

				   struct hist_trigger_data *hist_data)

{

	int i, ret = 0;



	if (hist_data->n_actions)

		seq_puts(m, "\n  action tracking variables (for onmax()/onchange()/onmatch()):\n");



	for (i = 0; i < hist_data->n_actions; i++) {

		struct action_data *action = hist_data->actions[i];



		ret = hist_action_debug_show(m, action, i);

		if (ret)

			goto out;

	}



	if (hist_data->n_save_vars)

		seq_puts(m, "\n  save action variables (save() params):\n");



	for (i = 0; i < hist_data->n_save_vars; i++) {

		ret = field_var_debug_show(m, hist_data->save_vars[i], i, true);

		if (ret)

			goto out;

	}

out:

	return ret;

}



static void hist_trigger_debug_show(struct seq_file *m,

				    struct event_trigger_data *data, int n)

{

	struct hist_trigger_data *hist_data;

	int i, ret;



	if (n > 0)

		seq_puts(m, "\n\n");



	seq_puts(m, "# event histogram\n#\n# trigger info: ");

	data->ops->print(m, data->ops, data);

	seq_puts(m, "#\n\n");



	hist_data = data->private_data;



	seq_printf(m, "hist_data: %p\n\n", hist_data);

	seq_printf(m, "  n_vals: %u\n", hist_data->n_vals);

	seq_printf(m, "  n_keys: %u\n", hist_data->n_keys);

	seq_printf(m, "  n_fields: %u\n", hist_data->n_fields);



	seq_puts(m, "\n  val fields:\n\n");



	seq_puts(m, "    hist_data->fields[0]:\n");

	ret = hist_field_debug_show(m, hist_data->fields[0],

				    HIST_FIELD_FL_HITCOUNT);

	if (ret)

		return;



	for (i = 1; i < hist_data->n_vals; i++) {

		seq_printf(m, "\n    hist_data->fields[%d]:\n", i);

		ret = hist_field_debug_show(m, hist_data->fields[i], 0);

		if (ret)

			return;

	}



	seq_puts(m, "\n  key fields:\n");



	for (i = hist_data->n_vals; i < hist_data->n_fields; i++) {

		seq_printf(m, "\n    hist_data->fields[%d]:\n", i);

		ret = hist_field_debug_show(m, hist_data->fields[i],

					    HIST_FIELD_FL_KEY);

		if (ret)

			return;

	}



	if (hist_data->n_var_refs)

		seq_puts(m, "\n  variable reference fields:\n");



	for (i = 0; i < hist_data->n_var_refs; i++) {

		seq_printf(m, "\n    hist_data->var_refs[%d]:\n", i);

		ret = hist_field_debug_show(m, hist_data->var_refs[i],

					    HIST_FIELD_FL_VAR_REF);

		if (ret)

			return;

	}



	if (hist_data->n_field_vars)

		seq_puts(m, "\n  field variables:\n");



	for (i = 0; i < hist_data->n_field_vars; i++) {

		ret = field_var_debug_show(m, hist_data->field_vars[i], i, false);

		if (ret)

			return;

	}



	ret = hist_actions_debug_show(m, hist_data);

	if (ret)

		return;

}



static int hist_debug_show(struct seq_file *m, void *v)

{

	struct event_trigger_data *data;

	struct trace_event_file *event_file;

	int n = 0, ret = 0;



	mutex_lock(&event_mutex);



	event_file = event_file_data(m->private);

	if (unlikely(!event_file)) {

		ret = -ENODEV;

		goto out_unlock;

	}



	list_for_each_entry(data, &event_file->triggers, list) {

		if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)

			hist_trigger_debug_show(m, data, n++);

	}



 out_unlock:

	mutex_unlock(&event_mutex);



	return ret;

}



static int event_hist_debug_open(struct inode *inode, struct file *file)

{

	int ret;



	ret = security_locked_down(LOCKDOWN_TRACEFS);

	if (ret)

		return ret;



	return single_open(file, hist_debug_show, file);

}



const struct file_operations event_hist_debug_fops = {

	.open = event_hist_debug_open,

	.read = seq_read,

	.llseek = seq_lseek,

	.release = single_release,

};

#endif



static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)

{

	const char *field_name = hist_field_name(hist_field, 0);

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