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	mutex_lock(&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		goto exit;
140
141	ret = insert_stat(root, stat, ts->stat_cmp);
142	if (ret)
143		goto exit;
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
160exit:
161	mutex_unlock(&session->stat_mutex);
162	return ret;
163
164exit_free_rbtree:
165	__reset_stat_session(session);
166	mutex_unlock(&session->stat_mutex);
167	return ret;
168}
169
170
171static void *stat_seq_start(struct seq_file *s, loff_t *pos)
172{
173	struct stat_session *session = s->private;
174	struct rb_node *node;
175	int n = *pos;
176	int i;
177
178	/* Prevent from tracer switch or rbtree modification */
179	mutex_lock(&session->stat_mutex);
180
181	/* If we are in the beginning of the file, print the headers */
182	if (session->ts->stat_headers) {
183		if (n == 0)
184			return SEQ_START_TOKEN;
185		n--;
186	}
187
188	node = rb_first(&session->stat_root);
189	for (i = 0; node && i < n; i++)
190		node = rb_next(node);
191
192	return node;
193}
194
195static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
196{
197	struct stat_session *session = s->private;
198	struct rb_node *node = p;
199
200	(*pos)++;
201
202	if (p == SEQ_START_TOKEN)
203		return rb_first(&session->stat_root);
204
205	return rb_next(node);
206}
207
208static void stat_seq_stop(struct seq_file *s, void *p)
209{
210	struct stat_session *session = s->private;
211	mutex_unlock(&session->stat_mutex);
212}
213
214static int stat_seq_show(struct seq_file *s, void *v)
215{
216	struct stat_session *session = s->private;
217	struct stat_node *l = container_of(v, struct stat_node, node);
218
219	if (v == SEQ_START_TOKEN)
220		return session->ts->stat_headers(s);
221
222	return session->ts->stat_show(s, l->stat);
223}
224
225static const struct seq_operations trace_stat_seq_ops = {
226	.start		= stat_seq_start,
227	.next		= stat_seq_next,
228	.stop		= stat_seq_stop,
229	.show		= stat_seq_show
230};
231
232/* The session stat is refilled and resorted at each stat file opening */
233static int tracing_stat_open(struct inode *inode, struct file *file)
234{
235	int ret;
236	struct seq_file *m;
237	struct stat_session *session = inode->i_private;
238
239	ret = security_locked_down(LOCKDOWN_TRACEFS);
240	if (ret)
241		return ret;
242
243	ret = stat_seq_init(session);
244	if (ret)
245		return ret;
246
247	ret = seq_open(file, &trace_stat_seq_ops);
248	if (ret) {
249		reset_stat_session(session);
250		return ret;
251	}
252
253	m = file->private_data;
254	m->private = session;
255	return ret;
256}
257
258/*
259 * Avoid consuming memory with our now useless rbtree.
260 */
261static int tracing_stat_release(struct inode *i, struct file *f)
262{
263	struct stat_session *session = i->i_private;
264
265	reset_stat_session(session);
266
267	return seq_release(i, f);
268}
269
270static const struct file_operations tracing_stat_fops = {
271	.open		= tracing_stat_open,
272	.read		= seq_read,
273	.llseek		= seq_lseek,
274	.release	= tracing_stat_release
275};
276
277static int tracing_stat_init(void)
278{
279	int ret;
280
281	ret = tracing_init_dentry();
282	if (ret)
283		return -ENODEV;
284
285	stat_dir = tracefs_create_dir("trace_stat", NULL);
286	if (!stat_dir) {
287		pr_warn("Could not create tracefs 'trace_stat' entry\n");
288		return -ENOMEM;
289	}
290	return 0;
291}
292
293static int init_stat_file(struct stat_session *session)
294{
295	int ret;
296
297	if (!stat_dir && (ret = tracing_stat_init()))
298		return ret;
299
300	session->file = tracefs_create_file(session->ts->name, TRACE_MODE_WRITE,
301					    stat_dir, session,
302					    &tracing_stat_fops);
303	if (!session->file)
304		return -ENOMEM;
305	return 0;
306}
307
308int register_stat_tracer(struct tracer_stat *trace)
309{
310	struct stat_session *session, *node;
311	int ret = -EINVAL;
312
313	if (!trace)
314		return -EINVAL;
315
316	if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
317		return -EINVAL;
318
319	/* Already registered? */
320	mutex_lock(&all_stat_sessions_mutex);
321	list_for_each_entry(node, &all_stat_sessions, session_list) {
322		if (node->ts == trace)
323			goto out;
324	}
325
326	ret = -ENOMEM;
327	/* Init the session */
328	session = kzalloc(sizeof(*session), GFP_KERNEL);
329	if (!session)
330		goto out;
331
332	session->ts = trace;
333	INIT_LIST_HEAD(&session->session_list);
334	mutex_init(&session->stat_mutex);
335
336	ret = init_stat_file(session);
337	if (ret) {
338		destroy_session(session);
339		goto out;
340	}
341
342	ret = 0;
343	/* Register */
344	list_add_tail(&session->session_list, &all_stat_sessions);
345 out:
346	mutex_unlock(&all_stat_sessions_mutex);
347
348	return ret;
349}
350
351void unregister_stat_tracer(struct tracer_stat *trace)
352{
353	struct stat_session *node, *tmp;
354
355	mutex_lock(&all_stat_sessions_mutex);
356	list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
357		if (node->ts == trace) {
358			list_del(&node->session_list);
359			destroy_session(node);
360			break;
361		}
362	}
363	mutex_unlock(&all_stat_sessions_mutex);
364}
365