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
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