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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Infrastructure for statistic tracing (histogram output).
4 *
5 * Copyright (C) 2008-2009 Frederic Weisbecker <[email protected]>
6 *
7 * Based on the code from trace_branch.c which is
8 * Copyright (C) 2008 Steven Rostedt <[email protected]>
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_obj(*data);
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_obj(*session);
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}