trace_stat.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Infrastructure for statistic tracing (histogram output).
  4 *
  5 * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
  6 *
  7 * Based on the code from trace_branch.c which is
  8 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
  9 *
 10 */
 11
 12#include <linux/security.h>
 13#include <linux/list.h>
 14#include <linux/slab.h>
 15#include <linux/rbtree.h>
 16#include <linux/tracefs.h>
 17#include "trace_stat.h"
 18#include "trace.h"
 19
 20
 21/*
 22 * List of stat red-black nodes from a tracer
 23 * We use a such tree to sort quickly the stat
 24 * entries from the tracer.
 25 */
 26struct stat_node {
 27	struct rb_node		node;
 28	void			*stat;
 29};
 30
 31/* A stat session is the stats output in one file */
 32struct stat_session {
 33	struct list_head	session_list;
 34	struct tracer_stat	*ts;
 35	struct rb_root		stat_root;
 36	struct mutex		stat_mutex;
 37	struct dentry		*file;
 38};
 39
 40/* All of the sessions currently in use. Each stat file embed one session */
 41static LIST_HEAD(all_stat_sessions);
 42static DEFINE_MUTEX(all_stat_sessions_mutex);
 43
 44/* The root directory for all stat files */
 45static struct dentry		*stat_dir;
 46
 47static void __reset_stat_session(struct stat_session *session)
 48{
 49	struct stat_node *snode, *n;
 50
 51	rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
 52		if (session->ts->stat_release)
 53			session->ts->stat_release(snode->stat);
 54		kfree(snode);
 55	}
 56
 57	session->stat_root = RB_ROOT;
 58}
 59
 60static void reset_stat_session(struct stat_session *session)
 61{
 62	mutex_lock(&session->stat_mutex);
 63	__reset_stat_session(session);
 64	mutex_unlock(&session->stat_mutex);
 65}
 66
 67static void destroy_session(struct stat_session *session)
 68{
 69	tracefs_remove(session->file);
 70	__reset_stat_session(session);
 71	mutex_destroy(&session->stat_mutex);
 72	kfree(session);
 73}
 74
 75static int insert_stat(struct rb_root *root, void *stat, cmp_func_t cmp)
 76{
 77	struct rb_node **new = &(root->rb_node), *parent = NULL;
 78	struct stat_node *data;
 79
 80	data = kzalloc(sizeof(*data), GFP_KERNEL);
 81	if (!data)
 82		return -ENOMEM;
 83	data->stat = stat;
 84
 85	/*
 86	 * Figure out where to put new node
 87	 * This is a descendent sorting
 88	 */
 89	while (*new) {
 90		struct stat_node *this;
 91		int result;
 92
 93		this = container_of(*new, struct stat_node, node);
 94		result = cmp(data->stat, this->stat);
 95
 96		parent = *new;
 97		if (result >= 0)
 98			new = &((*new)->rb_left);
 99		else
100			new = &((*new)->rb_right);
101	}
102
103	rb_link_node(&data->node, parent, new);
104	rb_insert_color(&data->node, root);
105	return 0;
106}
107
108/*
109 * For tracers that don't provide a stat_cmp callback.
110 * This one will force an insertion as right-most node
111 * in the rbtree.
112 */
113static int dummy_cmp(const void *p1, const void *p2)
114{
115	return -1;
116}
117
118/*
119 * Initialize the stat rbtree at each trace_stat file opening.
120 * All of these copies and sorting are required on all opening
121 * since the stats could have changed between two file sessions.
122 */
123static int stat_seq_init(struct stat_session *session)
124{
125	struct tracer_stat *ts = session->ts;
126	struct rb_root *root = &session->stat_root;
127	void *stat;
128	int ret = 0;
129	int i;
130
131	guard(mutex)(&session->stat_mutex);
132	__reset_stat_session(session);
133
134	if (!ts->stat_cmp)
135		ts->stat_cmp = dummy_cmp;
136
137	stat = ts->stat_start(ts);
138	if (!stat)
139		return 0;
140
141	ret = insert_stat(root, stat, ts->stat_cmp);
142	if (ret)
143		return ret;
144
145	/*
146	 * Iterate over the tracer stat entries and store them in an rbtree.
147	 */
148	for (i = 1; ; i++) {
149		stat = ts->stat_next(stat, i);
150
151		/* End of insertion */
152		if (!stat)
153			break;
154
155		ret = insert_stat(root, stat, ts->stat_cmp);
156		if (ret)
157			goto exit_free_rbtree;
158	}
159
160	return ret;
161
162exit_free_rbtree:
163	__reset_stat_session(session);
164	return ret;
165}
166
167
168static void *stat_seq_start(struct seq_file *s, loff_t *pos)
169{
170	struct stat_session *session = s->private;
171	struct rb_node *node;
172	int n = *pos;
173	int i;
174
175	/* Prevent from tracer switch or rbtree modification */
176	mutex_lock(&session->stat_mutex);
177
178	/* If we are in the beginning of the file, print the headers */
179	if (session->ts->stat_headers) {
180		if (n == 0)
181			return SEQ_START_TOKEN;
182		n--;
183	}
184
185	node = rb_first(&session->stat_root);
186	for (i = 0; node && i < n; i++)
187		node = rb_next(node);
188
189	return node;
190}
191
192static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
193{
194	struct stat_session *session = s->private;
195	struct rb_node *node = p;
196
197	(*pos)++;
198
199	if (p == SEQ_START_TOKEN)
200		return rb_first(&session->stat_root);
201
202	return rb_next(node);
203}
204
205static void stat_seq_stop(struct seq_file *s, void *p)
206{
207	struct stat_session *session = s->private;
208	mutex_unlock(&session->stat_mutex);
209}
210
211static int stat_seq_show(struct seq_file *s, void *v)
212{
213	struct stat_session *session = s->private;
214	struct stat_node *l = container_of(v, struct stat_node, node);
215
216	if (v == SEQ_START_TOKEN)
217		return session->ts->stat_headers(s);
218
219	return session->ts->stat_show(s, l->stat);
220}
221
222static const struct seq_operations trace_stat_seq_ops = {
223	.start		= stat_seq_start,
224	.next		= stat_seq_next,
225	.stop		= stat_seq_stop,
226	.show		= stat_seq_show
227};
228
229/* The session stat is refilled and resorted at each stat file opening */
230static int tracing_stat_open(struct inode *inode, struct file *file)
231{
232	int ret;
233	struct seq_file *m;
234	struct stat_session *session = inode->i_private;
235
236	ret = security_locked_down(LOCKDOWN_TRACEFS);
237	if (ret)
238		return ret;
239
240	ret = stat_seq_init(session);
241	if (ret)
242		return ret;
243
244	ret = seq_open(file, &trace_stat_seq_ops);
245	if (ret) {
246		reset_stat_session(session);
247		return ret;
248	}
249
250	m = file->private_data;
251	m->private = session;
252	return ret;
253}
254
255/*
256 * Avoid consuming memory with our now useless rbtree.
257 */
258static int tracing_stat_release(struct inode *i, struct file *f)
259{
260	struct stat_session *session = i->i_private;
261
262	reset_stat_session(session);
263
264	return seq_release(i, f);
265}
266
267static const struct file_operations tracing_stat_fops = {
268	.open		= tracing_stat_open,
269	.read		= seq_read,
270	.llseek		= seq_lseek,
271	.release	= tracing_stat_release
272};
273
274static int tracing_stat_init(void)
275{
276	int ret;
277
278	ret = tracing_init_dentry();
279	if (ret)
280		return -ENODEV;
281
282	stat_dir = tracefs_create_dir("trace_stat", NULL);
283	if (!stat_dir) {
284		pr_warn("Could not create tracefs 'trace_stat' entry\n");
285		return -ENOMEM;
286	}
287	return 0;
288}
289
290static int init_stat_file(struct stat_session *session)
291{
292	int ret;
293
294	if (!stat_dir && (ret = tracing_stat_init()))
295		return ret;
296
297	session->file = tracefs_create_file(session->ts->name, TRACE_MODE_WRITE,
298					    stat_dir, session,
299					    &tracing_stat_fops);
300	if (!session->file)
301		return -ENOMEM;
302	return 0;
303}
304
305int register_stat_tracer(struct tracer_stat *trace)
306{
307	struct stat_session *session, *node;
308	int ret;
309
310	if (!trace)
311		return -EINVAL;
312
313	if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
314		return -EINVAL;
315
316	guard(mutex)(&all_stat_sessions_mutex);
317
318	/* Already registered? */
319	list_for_each_entry(node, &all_stat_sessions, session_list) {
320		if (node->ts == trace)
321			return -EINVAL;
322	}
323
324	/* Init the session */
325	session = kzalloc(sizeof(*session), GFP_KERNEL);
326	if (!session)
327		return -ENOMEM;
328
329	session->ts = trace;
330	INIT_LIST_HEAD(&session->session_list);
331	mutex_init(&session->stat_mutex);
332
333	ret = init_stat_file(session);
334	if (ret) {
335		destroy_session(session);
336		return ret;
337	}
338
339	/* Register */
340	list_add_tail(&session->session_list, &all_stat_sessions);
341
342	return 0;
343}
344
345void unregister_stat_tracer(struct tracer_stat *trace)
346{
347	struct stat_session *node, *tmp;
348
349	mutex_lock(&all_stat_sessions_mutex);
350	list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
351		if (node->ts == trace) {
352			list_del(&node->session_list);
353			destroy_session(node);
354			break;
355		}
356	}
357	mutex_unlock(&all_stat_sessions_mutex);
358}