linux/kernel/trace/trace_events_hist.c

/*
 * trace_events_hist - trace event hist triggers
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Copyright (C) 2015 Tom Zanussi <tom.zanussi@linux.intel.com>
 */

#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>

#include "tracing_map.h"
#include "trace.h"

struct hist_field;

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;
	unsigned int			size;
	unsigned int			offset;
};

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;
}

#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)++)

#define for_each_hist_val_field(i, hist_data)	\
	for ((i) = 0; (i) < (hist_data)->n_vals; (i)++)

#define for_each_hist_key_field(i, hist_data)	\
	for ((i) = (hist_data)->n_vals; (i) < (hist_data)->n_fields; (i)++)

#define HITCOUNT_IDX		0
#define HIST_KEY_SIZE_MAX	(MAX_FILTER_STR_VAL + sizeof(u64))

enum hist_field_flags {
	HIST_FIELD_FL_HITCOUNT	= 1,
	HIST_FIELD_FL_KEY	= 2,
	HIST_FIELD_FL_STRING	= 4,
};

struct hist_trigger_attrs {
	char		*keys_str;
	char		*vals_str;
	char		*sort_key_str;
	bool		pause;
	bool		cont;
	unsigned int	map_bits;
};

struct hist_trigger_data {
	struct hist_field               *fields[TRACING_MAP_FIELDS_MAX];
	unsigned int			n_vals;
	unsigned int			n_keys;
	unsigned int			n_fields;
	unsigned int			key_size;
	struct tracing_map_sort_key	sort_keys[TRACING_MAP_SORT_KEYS_MAX];
	unsigned int			n_sort_keys;
	struct trace_event_file		*event_file;
	struct hist_trigger_attrs	*attrs;
	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;
	int ret;

	strsep(&str, "=");
	if (!str) {
		ret = -EINVAL;
		goto out;
	}

	ret = kstrtoul(str, 0, &size);
	if (ret)
		goto out;

	map_bits = ilog2(roundup_pow_of_two(size));
	if (map_bits < TRACING_MAP_BITS_MIN ||
	    map_bits > TRACING_MAP_BITS_MAX)
		ret = -EINVAL;
	else
		ret = map_bits;
 out:
	return ret;
}

static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
{
	if (!attrs)
		return;

	kfree(attrs->sort_key_str);
	kfree(attrs->keys_str);
	kfree(attrs->vals_str);
	kfree(attrs);
}

static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
{
	struct hist_trigger_attrs *attrs;
	int ret = 0;

	attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
	if (!attrs)
		return ERR_PTR(-ENOMEM);

	while (trigger_str) {
		char *str = strsep(&trigger_str, ":");

		if ((strncmp(str, "key=", strlen("key=")) == 0) ||
		    (strncmp(str, "keys=", strlen("keys=")) == 0))
			attrs->keys_str = kstrdup(str, GFP_KERNEL);
		else if ((strncmp(str, "val=", strlen("val=")) == 0) ||
			 (strncmp(str, "vals=", strlen("vals=")) == 0) ||
			 (strncmp(str, "values=", strlen("values=")) == 0))
			attrs->vals_str = kstrdup(str, GFP_KERNEL);
		else if (strncmp(str, "sort=", strlen("sort=")) == 0)
			attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
		else if (strcmp(str, "pause") == 0)
			attrs->pause = true;
		else if ((strcmp(str, "cont") == 0) ||
			 (strcmp(str, "continue") == 0))
			attrs->cont = true;
		else if (strncmp(str, "size=", strlen("size=")) == 0) {
			int map_bits = parse_map_size(str);

			if (map_bits < 0) {
				ret = map_bits;
				goto free;
			}
			attrs->map_bits = map_bits;
		} else {
			ret = -EINVAL;
			goto free;
		}
	}

	if (!attrs->keys_str) {
		ret = -EINVAL;
		goto free;
	}

	return attrs;
 free:
	destroy_hist_trigger_attrs(attrs);

	return ERR_PTR(ret);
}

static void destroy_hist_field(struct hist_field *hist_field)
{
	kfree(hist_field);
}

static struct hist_field *create_hist_field(struct ftrace_event_field *field,
					    unsigned long flags)
{
	struct hist_field *hist_field;

	if (field && is_function_field(field))
		return NULL;

	hist_field = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
	if (!hist_field)
		return NULL;

	if (flags & HIST_FIELD_FL_HITCOUNT) {
		hist_field->fn = hist_field_counter;
		goto out;
	}

	if (is_string_field(field)) {
		flags |= HIST_FIELD_FL_STRING;
		hist_field->fn = hist_field_string;
	} 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;

	return hist_field;
}

static void destroy_hist_fields(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < TRACING_MAP_FIELDS_MAX; i++) {
		if (hist_data->fields[i]) {
			destroy_hist_field(hist_data->fields[i]);
			hist_data->fields[i] = NULL;
		}
	}
}

static int create_hitcount_val(struct hist_trigger_data *hist_data)
{
	hist_data->fields[HITCOUNT_IDX] =
		create_hist_field(NULL, HIST_FIELD_FL_HITCOUNT);
	if (!hist_data->fields[HITCOUNT_IDX])
		return -ENOMEM;

	hist_data->n_vals++;

	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
		return -EINVAL;

	return 0;
}

static int create_val_field(struct hist_trigger_data *hist_data,
			    unsigned int val_idx,
			    struct trace_event_file *file,
			    char *field_str)
{
	struct ftrace_event_field *field = NULL;
	unsigned long flags = 0;
	int ret = 0;

	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX))
		return -EINVAL;
	field = trace_find_event_field(file->event_call, field_str);
	if (!field) {
		ret = -EINVAL;
		goto out;
	}

	hist_data->fields[val_idx] = create_hist_field(field, flags);
	if (!hist_data->fields[val_idx]) {
		ret = -ENOMEM;
		goto out;
	}

	++hist_data->n_vals;

	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
		ret = -EINVAL;
 out:
	return ret;
}

static int create_val_fields(struct hist_trigger_data *hist_data,
			     struct trace_event_file *file)
{
	char *fields_str, *field_str;
	unsigned int i, j;
	int ret;

	ret = create_hitcount_val(hist_data);
	if (ret)
		goto out;

	fields_str = hist_data->attrs->vals_str;
	if (!fields_str)
		goto out;

	strsep(&fields_str, "=");
	if (!fields_str)
		goto out;

	for (i = 0, j = 1; i < TRACING_MAP_VALS_MAX &&
		     j < TRACING_MAP_VALS_MAX; i++) {
		field_str = strsep(&fields_str, ",");
		if (!field_str)
			break;
		if (strcmp(field_str, "hitcount") == 0)
			continue;
		ret = create_val_field(hist_data, j++, file, field_str);
		if (ret)
			goto out;
	}
	if (fields_str && (strcmp(fields_str, "hitcount") != 0))
		ret = -EINVAL;
 out:
	return ret;
}

static int create_key_field(struct hist_trigger_data *hist_data,
			    unsigned int key_idx,
			    unsigned int key_offset,
			    struct trace_event_file *file,
			    char *field_str)
{
	struct ftrace_event_field *field = NULL;
	unsigned long flags = 0;
	unsigned int key_size;
	int ret = 0;

	if (WARN_ON(key_idx >= TRACING_MAP_FIELDS_MAX))
		return -EINVAL;

	flags |= HIST_FIELD_FL_KEY;

	field = trace_find_event_field(file->event_call, field_str);
	if (!field) {
		ret = -EINVAL;
		goto out;
	}

	key_size = field->size;

	hist_data->fields[key_idx] = create_hist_field(field, flags);
	if (!hist_data->fields[key_idx]) {
		ret = -ENOMEM;
		goto out;
	}

	key_size = ALIGN(key_size, sizeof(u64));
	hist_data->fields[key_idx]->size = key_size;
	hist_data->fields[key_idx]->offset = key_offset;
	hist_data->key_size += key_size;
	if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
		ret = -EINVAL;
		goto out;
	}

	hist_data->n_keys++;

	if (WARN_ON(hist_data->n_keys > TRACING_MAP_KEYS_MAX))
		return -EINVAL;

	ret = key_size;
 out:
	return ret;
}

static int create_key_fields(struct hist_trigger_data *hist_data,
			     struct trace_event_file *file)
{
	unsigned int i, key_offset = 0, n_vals = hist_data->n_vals;
	char *fields_str, *field_str;
	int ret = -EINVAL;

	fields_str = hist_data->attrs->keys_str;
	if (!fields_str)
		goto out;

	strsep(&fields_str, "=");
	if (!fields_str)
		goto out;

	for (i = n_vals; i < n_vals + TRACING_MAP_KEYS_MAX; i++) {
		field_str = strsep(&fields_str, ",");
		if (!field_str)
			break;
		ret = create_key_field(hist_data, i, key_offset,
				       file, field_str);
		if (ret < 0)
			goto out;
		key_offset += ret;
	}
	if (fields_str) {
		ret = -EINVAL;
		goto out;
	}
	ret = 0;
 out:
	return ret;
}

static int create_hist_fields(struct hist_trigger_data *hist_data,
			      struct trace_event_file *file)
{
	int ret;

	ret = create_val_fields(hist_data, file);
	if (ret)
		goto out;

	ret = create_key_fields(hist_data, file);
	if (ret)
		goto out;

	hist_data->n_fields = hist_data->n_vals + hist_data->n_keys;
 out:
	return ret;
}

static int is_descending(const char *str)
{
	if (!str)
		return 0;

	if (strcmp(str, "descending") == 0)
		return 1;

	if (strcmp(str, "ascending") == 0)
		return 0;

	return -EINVAL;
}

static int create_sort_keys(struct hist_trigger_data *hist_data)
{
	char *fields_str = hist_data->attrs->sort_key_str;
	struct ftrace_event_field *field = NULL;
	struct tracing_map_sort_key *sort_key;
	int descending, ret = 0;
	unsigned int i, j;

	hist_data->n_sort_keys = 1; /* we always have at least one, hitcount */

	if (!fields_str)
		goto out;

	strsep(&fields_str, "=");
	if (!fields_str) {
		ret = -EINVAL;
		goto out;
	}

	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
		char *field_str, *field_name;

		sort_key = &hist_data->sort_keys[i];

		field_str = strsep(&fields_str, ",");
		if (!field_str) {
			if (i == 0)
				ret = -EINVAL;
			break;
		}

		if ((i == TRACING_MAP_SORT_KEYS_MAX - 1) && fields_str) {
			ret = -EINVAL;
			break;
		}

		field_name = strsep(&field_str, ".");
		if (!field_name) {
			ret = -EINVAL;
			break;
		}

		if (strcmp(field_name, "hitcount") == 0) {
			descending = is_descending(field_str);
			if (descending < 0) {
				ret = descending;
				break;
			}
			sort_key->descending = descending;
			continue;
		}

		for (j = 1; j < hist_data->n_fields; j++) {
			field = hist_data->fields[j]->field;
			if (field && (strcmp(field_name, field->name) == 0)) {
				sort_key->field_idx = j;
				descending = is_descending(field_str);
				if (descending < 0) {
					ret = descending;
					goto out;
				}
				sort_key->descending = descending;
				break;
			}
		}
		if (j == hist_data->n_fields) {
			ret = -EINVAL;
			break;
		}
	}
	hist_data->n_sort_keys = i;
 out:
	return ret;
}

static void destroy_hist_data(struct hist_trigger_data *hist_data)
{
	destroy_hist_trigger_attrs(hist_data->attrs);
	destroy_hist_fields(hist_data);
	tracing_map_destroy(hist_data->map);
	kfree(hist_data);
}

static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
{
	struct tracing_map *map = hist_data->map;
	struct ftrace_event_field *field;
	struct hist_field *hist_field;
	unsigned int i, idx;

	for_each_hist_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		if (hist_field->flags & HIST_FIELD_FL_KEY) {
			tracing_map_cmp_fn_t cmp_fn;

			field = hist_field->field;

			if (is_string_field(field))
				cmp_fn = tracing_map_cmp_string;
			else
				cmp_fn = tracing_map_cmp_num(field->size,
							     field->is_signed);
			idx = tracing_map_add_key_field(map,
							hist_field->offset,
							cmp_fn);

		} else
			idx = tracing_map_add_sum_field(map);

		if (idx < 0)
			return idx;
	}

	return 0;
}

static struct hist_trigger_data *
create_hist_data(unsigned int map_bits,
		 struct hist_trigger_attrs *attrs,
		 struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data;
	int ret = 0;

	hist_data = kzalloc(sizeof(*hist_data), GFP_KERNEL);
	if (!hist_data)
		return ERR_PTR(-ENOMEM);

	hist_data->attrs = attrs;

	ret = create_hist_fields(hist_data, file);
	if (ret)
		goto free;

	ret = create_sort_keys(hist_data);
	if (ret)
		goto free;

	hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
					    NULL, hist_data);
	if (IS_ERR(hist_data->map)) {
		ret = PTR_ERR(hist_data->map);
		hist_data->map = NULL;
		goto free;
	}

	ret = create_tracing_map_fields(hist_data);
	if (ret)
		goto free;

	ret = tracing_map_init(hist_data->map);
	if (ret)
		goto free;

	hist_data->event_file = file;
 out:
	return hist_data;
 free:
	hist_data->attrs = NULL;

	destroy_hist_data(hist_data);

	hist_data = ERR_PTR(ret);

	goto out;
}

static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
				    struct tracing_map_elt *elt,
				    void *rec)
{
	struct hist_field *hist_field;
	unsigned int i;
	u64 hist_val;

	for_each_hist_val_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		hist_val = hist_field->fn(hist_field, rec);
		tracing_map_update_sum(elt, i, hist_val);
	}
}

static void event_hist_trigger(struct event_trigger_data *data, void *rec)
{
	struct hist_trigger_data *hist_data = data->private_data;
	char compound_key[HIST_KEY_SIZE_MAX];
	struct hist_field *key_field;
	struct tracing_map_elt *elt;
	u64 field_contents;
	void *key = NULL;
	unsigned int i;

	if (hist_data->n_keys > 1)
		memset(compound_key, 0, hist_data->key_size);

	for_each_hist_key_field(i, hist_data) {
		key_field = hist_data->fields[i];

		field_contents = key_field->fn(key_field, rec);
		if (key_field->flags & HIST_FIELD_FL_STRING)
			key = (void *)(unsigned long)field_contents;
		else
			key = (void *)&field_contents;

		if (hist_data->n_keys > 1) {
			memcpy(compound_key + key_field->offset, key,
			       key_field->size);
		}
	}

	if (hist_data->n_keys > 1)
		key = compound_key;

	elt = tracing_map_insert(hist_data->map, key);
	if (elt)
		hist_trigger_elt_update(hist_data, elt, rec);
}

static void
hist_trigger_entry_print(struct seq_file *m,
			 struct hist_trigger_data *hist_data, void *key,
			 struct tracing_map_elt *elt)
{
	struct hist_field *key_field;
	unsigned int i;
	u64 uval;

	seq_puts(m, "{ ");

	for_each_hist_key_field(i, hist_data) {
		key_field = hist_data->fields[i];

		if (i > hist_data->n_vals)
			seq_puts(m, ", ");

		if (key_field->flags & HIST_FIELD_FL_STRING) {
			seq_printf(m, "%s: %-50s", key_field->field->name,
				   (char *)(key + key_field->offset));
		} else {
			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: %10llu", key_field->field->name,
				   uval);
		}
	}

	seq_puts(m, " }");

	seq_printf(m, " hitcount: %10llu",
		   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));
	}

	seq_puts(m, "\n");
}

static int print_entries(struct seq_file *m,
			 struct hist_trigger_data *hist_data)
{
	struct tracing_map_sort_entry **sort_entries = NULL;
	struct tracing_map *map = hist_data->map;
	unsigned int i, n_entries;

	n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
					     hist_data->n_sort_keys,
					     &sort_entries);
	if (n_entries < 0)
		return n_entries;

	for (i = 0; i < n_entries; i++)
		hist_trigger_entry_print(m, hist_data,
					 sort_entries[i]->key,
					 sort_entries[i]->elt);

	tracing_map_destroy_sort_entries(sort_entries, n_entries);

	return n_entries;
}

static int hist_show(struct seq_file *m, void *v)
{
	struct event_trigger_data *test, *data = NULL;
	struct trace_event_file *event_file;
	struct hist_trigger_data *hist_data;
	int n_entries, 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_rcu(test, &event_file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			data = test;
			break;
		}
	}
	if (!data)
		goto out_unlock;

	seq_puts(m, "# event histogram\n#\n# trigger info: ");
	data->ops->print(m, data->ops, data);
	seq_puts(m, "\n");

	hist_data = data->private_data;
	n_entries = print_entries(m, hist_data);
	if (n_entries < 0) {
		ret = n_entries;
		n_entries = 0;
	}

	seq_printf(m, "\nTotals:\n    Hits: %llu\n    Entries: %u\n    Dropped: %llu\n",
		   (u64)atomic64_read(&hist_data->map->hits),
		   n_entries, (u64)atomic64_read(&hist_data->map->drops));
 out_unlock:
	mutex_unlock(&event_mutex);

	return ret;
}

static int event_hist_open(struct inode *inode, struct file *file)
{
	return single_open(file, hist_show, file);
}

const struct file_operations event_hist_fops = {
	.open = event_hist_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
{
	seq_printf(m, "%s", hist_field->field->name);
}

static int event_hist_trigger_print(struct seq_file *m,
				    struct event_trigger_ops *ops,
				    struct event_trigger_data *data)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct hist_field *key_field;
	unsigned int i;

	seq_puts(m, "hist:keys=");

	for_each_hist_key_field(i, hist_data) {
		key_field = hist_data->fields[i];

		if (i > hist_data->n_vals)
			seq_puts(m, ",");

		hist_field_print(m, key_field);
	}

	seq_puts(m, ":vals=");

	for_each_hist_val_field(i, hist_data) {
		if (i == HITCOUNT_IDX)
			seq_puts(m, "hitcount");
		else {
			seq_puts(m, ",");
			hist_field_print(m, hist_data->fields[i]);
		}
	}

	seq_puts(m, ":sort=");

	for (i = 0; i < hist_data->n_sort_keys; i++) {
		struct tracing_map_sort_key *sort_key;

		sort_key = &hist_data->sort_keys[i];

		if (i > 0)
			seq_puts(m, ",");

		if (sort_key->field_idx == HITCOUNT_IDX)
			seq_puts(m, "hitcount");
		else {
			unsigned int idx = sort_key->field_idx;

			if (WARN_ON(idx >= TRACING_MAP_FIELDS_MAX))
				return -EINVAL;

			hist_field_print(m, hist_data->fields[idx]);
		}

		if (sort_key->descending)
			seq_puts(m, ".descending");
	}

	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));

	if (data->filter_str)
		seq_printf(m, " if %s", data->filter_str);

	if (data->paused)
		seq_puts(m, " [paused]");
	else
		seq_puts(m, " [active]");

	seq_putc(m, '\n');

	return 0;
}

static void event_hist_trigger_free(struct event_trigger_ops *ops,
				    struct event_trigger_data *data)
{
	struct hist_trigger_data *hist_data = data->private_data;

	if (WARN_ON_ONCE(data->ref <= 0))
		return;

	data->ref--;
	if (!data->ref) {
		trigger_data_free(data);
		destroy_hist_data(hist_data);
	}
}

static struct event_trigger_ops event_hist_trigger_ops = {
	.func			= event_hist_trigger,
	.print			= event_hist_trigger_print,
	.init			= event_trigger_init,
	.free			= event_hist_trigger_free,
};

static struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
							    char *param)
{
	return &event_hist_trigger_ops;
}

static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
				 struct event_trigger_data *data,
				 struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct event_trigger_data *test;
	int ret = 0;

	list_for_each_entry_rcu(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (hist_data->attrs->pause)
				test->paused = true;
			else if (hist_data->attrs->cont)
				test->paused = false;
			else
				ret = -EEXIST;
			goto out;
		}
	}

	if (hist_data->attrs->cont) {
		ret = -ENOENT;
		goto out;
	}

	if (hist_data->attrs->pause)
		data->paused = true;

	if (data->ops->init) {
		ret = data->ops->init(data->ops, data);
		if (ret < 0)
			goto out;
	}

	list_add_rcu(&data->list, &file->triggers);
	ret++;

	update_cond_flag(file);
	if (trace_event_trigger_enable_disable(file, 1) < 0) {
		list_del_rcu(&data->list);
		update_cond_flag(file);
		ret--;
	}
 out:
	return ret;
}

static int event_hist_trigger_func(struct event_command *cmd_ops,
				   struct trace_event_file *file,
				   char *glob, char *cmd, char *param)
{
	unsigned int hist_trigger_bits = TRACING_MAP_BITS_DEFAULT;
	struct event_trigger_data *trigger_data;
	struct hist_trigger_attrs *attrs;
	struct event_trigger_ops *trigger_ops;
	struct hist_trigger_data *hist_data;
	char *trigger;
	int ret = 0;

	if (!param)
		return -EINVAL;

	/* separate the trigger from the filter (k:v [if filter]) */
	trigger = strsep(&param, " \t");
	if (!trigger)
		return -EINVAL;

	attrs = parse_hist_trigger_attrs(trigger);
	if (IS_ERR(attrs))
		return PTR_ERR(attrs);

	if (attrs->map_bits)
		hist_trigger_bits = attrs->map_bits;

	hist_data = create_hist_data(hist_trigger_bits, attrs, file);
	if (IS_ERR(hist_data)) {
		destroy_hist_trigger_attrs(attrs);
		return PTR_ERR(hist_data);
	}

	trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);

	ret = -ENOMEM;
	trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
	if (!trigger_data)
		goto out_free;

	trigger_data->count = -1;
	trigger_data->ops = trigger_ops;
	trigger_data->cmd_ops = cmd_ops;

	INIT_LIST_HEAD(&trigger_data->list);
	RCU_INIT_POINTER(trigger_data->filter, NULL);

	trigger_data->private_data = hist_data;

	if (glob[0] == '!') {
		cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
		ret = 0;
		goto out_free;
	}

	if (!param) /* if param is non-empty, it's supposed to be a filter */
		goto out_reg;

	if (!cmd_ops->set_filter)
		goto out_reg;

	ret = cmd_ops->set_filter(param, trigger_data, file);
	if (ret < 0)
		goto out_free;
 out_reg:
	ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
	/*
	 * The above returns on success the # of triggers registered,
	 * but if it didn't register any it returns zero.  Consider no
	 * triggers registered a failure too.
	 */
	if (!ret) {
		if (!(attrs->pause || attrs->cont))
			ret = -ENOENT;
		goto out_free;
	} else if (ret < 0)
		goto out_free;
	/* Just return zero, not the number of registered triggers */
	ret = 0;
 out:
	return ret;
 out_free:
	if (cmd_ops->set_filter)
		cmd_ops->set_filter(NULL, trigger_data, NULL);

	kfree(trigger_data);

	destroy_hist_data(hist_data);
	goto out;
}

static struct event_command trigger_hist_cmd = {
	.name			= "hist",
	.trigger_type		= ETT_EVENT_HIST,
	.flags			= EVENT_CMD_FL_NEEDS_REC,
	.func			= event_hist_trigger_func,
	.reg			= hist_register_trigger,
	.unreg			= unregister_trigger,
	.get_trigger_ops	= event_hist_get_trigger_ops,
	.set_filter		= set_trigger_filter,
};

__init int register_trigger_hist_cmd(void)
{
	int ret;

	ret = register_event_command(&trigger_hist_cmd);
	WARN_ON(ret < 0);

	return ret;
}