xref: /openbmc/linux/kernel/trace/trace_stat.c (revision a90bb65a) 
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  */
26 struct stat_node {
27 	struct rb_node		node;
28 	void			*stat;
29 };
30 
31 /* A stat session is the stats output in one file */
32 struct 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 */
41 static LIST_HEAD(all_stat_sessions);
42 static DEFINE_MUTEX(all_stat_sessions_mutex);
43 
44 /* The root directory for all stat files */
45 static struct dentry		*stat_dir;
46 
47 static 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 
60 static 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 
67 static 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 
75 static 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  */
113 static 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  */
123 static 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 
160 exit:
161 	mutex_unlock(&session->stat_mutex);
162 	return ret;
163 
164 exit_free_rbtree:
165 	__reset_stat_session(session);
166 	mutex_unlock(&session->stat_mutex);
167 	return ret;
168 }
169 
170 
171 static 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 
195 static 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 
208 static 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 
214 static 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 
225 static 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 */
233 static 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  */
261 static 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 
270 static 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 
277 static 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 
293 static 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 
308 int 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 
351 void 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