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20591cf7 MD |
1 | /* |
2 | * lttng-tracepoint.c | |
3 | * | |
4 | * LTTng adaptation layer for Linux kernel 3.15+ tracepoints. | |
5 | * | |
6 | * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * | |
8 | * This library is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License as published by the Free Software Foundation; only | |
11 | * version 2.1 of the License. | |
12 | * | |
13 | * This library is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * Lesser General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU Lesser General Public | |
19 | * License along with this library; if not, write to the Free Software | |
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
21 | */ | |
22 | ||
20591cf7 MD |
23 | #include <linux/mutex.h> |
24 | #include <linux/err.h> | |
25 | #include <linux/notifier.h> | |
26 | #include <linux/tracepoint.h> | |
27 | #include <linux/slab.h> | |
28 | #include <linux/jhash.h> | |
29 | #include <linux/module.h> | |
30 | ||
241ae9a8 MD |
31 | #include <lttng-tracepoint.h> |
32 | #include <wrapper/list.h> | |
20591cf7 MD |
33 | |
34 | /* | |
35 | * Protect the tracepoint table. lttng_tracepoint_mutex nests within | |
36 | * kernel/tracepoint.c tp_modlist_mutex. kernel/tracepoint.c | |
37 | * tracepoint_mutex nests within lttng_tracepoint_mutex. | |
38 | */ | |
39 | static | |
40 | DEFINE_MUTEX(lttng_tracepoint_mutex); | |
41 | ||
42 | #define TRACEPOINT_HASH_BITS 6 | |
43 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) | |
44 | static | |
45 | struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; | |
46 | ||
47 | /* | |
48 | * The tracepoint entry is the node contained within the hash table. It | |
49 | * is a mapping from the "string" key to the struct tracepoint pointer. | |
50 | */ | |
51 | struct tracepoint_entry { | |
52 | struct hlist_node hlist; | |
53 | struct tracepoint *tp; | |
54 | int refcount; | |
55 | struct list_head probes; | |
56 | char name[0]; | |
57 | }; | |
58 | ||
59 | struct lttng_tp_probe { | |
60 | struct tracepoint_func tp_func; | |
61 | struct list_head list; | |
62 | }; | |
63 | ||
64 | static | |
65 | int add_probe(struct tracepoint_entry *e, void *probe, void *data) | |
66 | { | |
67 | struct lttng_tp_probe *p; | |
68 | int found = 0; | |
69 | ||
70 | list_for_each_entry(p, &e->probes, list) { | |
71 | if (p->tp_func.func == probe && p->tp_func.data == data) { | |
72 | found = 1; | |
73 | break; | |
74 | } | |
75 | } | |
76 | if (found) | |
77 | return -EEXIST; | |
78 | p = kmalloc(sizeof(struct lttng_tp_probe), GFP_KERNEL); | |
79 | if (!p) | |
80 | return -ENOMEM; | |
81 | p->tp_func.func = probe; | |
82 | p->tp_func.data = data; | |
83 | list_add(&p->list, &e->probes); | |
84 | return 0; | |
85 | } | |
86 | ||
87 | static | |
88 | int remove_probe(struct tracepoint_entry *e, void *probe, void *data) | |
89 | { | |
90 | struct lttng_tp_probe *p; | |
91 | int found = 0; | |
92 | ||
93 | list_for_each_entry(p, &e->probes, list) { | |
94 | if (p->tp_func.func == probe && p->tp_func.data == data) { | |
95 | found = 1; | |
96 | break; | |
97 | } | |
98 | } | |
99 | if (found) { | |
100 | list_del(&p->list); | |
101 | kfree(p); | |
102 | return 0; | |
103 | } else { | |
104 | WARN_ON(1); | |
105 | return -ENOENT; | |
106 | } | |
107 | } | |
108 | ||
109 | /* | |
110 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. | |
111 | * Must be called with lttng_tracepoint_mutex held. | |
112 | * Returns NULL if not present. | |
113 | */ | |
114 | static | |
115 | struct tracepoint_entry *get_tracepoint(const char *name) | |
116 | { | |
117 | struct hlist_head *head; | |
118 | struct tracepoint_entry *e; | |
119 | u32 hash = jhash(name, strlen(name), 0); | |
120 | ||
121 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; | |
f934e302 | 122 | lttng_hlist_for_each_entry(e, head, hlist) { |
20591cf7 MD |
123 | if (!strcmp(name, e->name)) |
124 | return e; | |
125 | } | |
126 | return NULL; | |
127 | } | |
128 | ||
129 | /* | |
130 | * Add the tracepoint to the tracepoint hash table. Must be called with | |
131 | * lttng_tracepoint_mutex held. | |
132 | */ | |
133 | static | |
134 | struct tracepoint_entry *add_tracepoint(const char *name) | |
135 | { | |
136 | struct hlist_head *head; | |
137 | struct tracepoint_entry *e; | |
138 | size_t name_len = strlen(name) + 1; | |
139 | u32 hash = jhash(name, name_len - 1, 0); | |
140 | ||
141 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; | |
f934e302 | 142 | lttng_hlist_for_each_entry(e, head, hlist) { |
20591cf7 MD |
143 | if (!strcmp(name, e->name)) { |
144 | printk(KERN_NOTICE | |
145 | "tracepoint %s busy\n", name); | |
146 | return ERR_PTR(-EEXIST); /* Already there */ | |
147 | } | |
148 | } | |
149 | /* | |
150 | * Using kmalloc here to allocate a variable length element. Could | |
151 | * cause some memory fragmentation if overused. | |
152 | */ | |
153 | e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL); | |
154 | if (!e) | |
155 | return ERR_PTR(-ENOMEM); | |
156 | memcpy(&e->name[0], name, name_len); | |
157 | e->tp = NULL; | |
158 | e->refcount = 0; | |
159 | INIT_LIST_HEAD(&e->probes); | |
160 | hlist_add_head(&e->hlist, head); | |
161 | return e; | |
162 | } | |
163 | ||
164 | /* | |
165 | * Remove the tracepoint from the tracepoint hash table. Must be called | |
166 | * with lttng_tracepoint_mutex held. | |
167 | */ | |
168 | static | |
169 | void remove_tracepoint(struct tracepoint_entry *e) | |
170 | { | |
171 | hlist_del(&e->hlist); | |
172 | kfree(e); | |
173 | } | |
174 | ||
175 | int lttng_tracepoint_probe_register(const char *name, void *probe, void *data) | |
176 | { | |
177 | struct tracepoint_entry *e; | |
178 | int ret = 0; | |
179 | ||
180 | mutex_lock(<tng_tracepoint_mutex); | |
181 | e = get_tracepoint(name); | |
182 | if (!e) { | |
183 | e = add_tracepoint(name); | |
184 | if (IS_ERR(e)) { | |
185 | ret = PTR_ERR(e); | |
186 | goto end; | |
187 | } | |
188 | } | |
189 | /* add (probe, data) to entry */ | |
190 | ret = add_probe(e, probe, data); | |
191 | if (ret) | |
192 | goto end; | |
193 | e->refcount++; | |
194 | if (e->tp) { | |
195 | ret = tracepoint_probe_register(e->tp, probe, data); | |
196 | WARN_ON_ONCE(ret); | |
197 | ret = 0; | |
198 | } | |
199 | end: | |
200 | mutex_unlock(<tng_tracepoint_mutex); | |
201 | return ret; | |
202 | } | |
203 | ||
204 | int lttng_tracepoint_probe_unregister(const char *name, void *probe, void *data) | |
205 | { | |
206 | struct tracepoint_entry *e; | |
207 | int ret = 0; | |
208 | ||
209 | mutex_lock(<tng_tracepoint_mutex); | |
210 | e = get_tracepoint(name); | |
211 | if (!e) { | |
212 | ret = -ENOENT; | |
213 | goto end; | |
214 | } | |
215 | /* remove (probe, data) from entry */ | |
216 | ret = remove_probe(e, probe, data); | |
217 | if (ret) | |
218 | goto end; | |
219 | if (e->tp) { | |
220 | ret = tracepoint_probe_unregister(e->tp, probe, data); | |
221 | WARN_ON_ONCE(ret); | |
222 | ret = 0; | |
223 | } | |
224 | if (!--e->refcount) | |
225 | remove_tracepoint(e); | |
226 | end: | |
227 | mutex_unlock(<tng_tracepoint_mutex); | |
228 | return ret; | |
229 | } | |
230 | ||
231 | #ifdef CONFIG_MODULES | |
232 | ||
233 | static | |
234 | int lttng_tracepoint_coming(struct tp_module *tp_mod) | |
235 | { | |
236 | int i; | |
237 | ||
238 | mutex_lock(<tng_tracepoint_mutex); | |
239 | for (i = 0; i < tp_mod->mod->num_tracepoints; i++) { | |
240 | struct tracepoint *tp; | |
241 | struct tracepoint_entry *e; | |
242 | struct lttng_tp_probe *p; | |
243 | ||
244 | tp = tp_mod->mod->tracepoints_ptrs[i]; | |
245 | e = get_tracepoint(tp->name); | |
246 | if (!e) { | |
247 | e = add_tracepoint(tp->name); | |
248 | if (IS_ERR(e)) { | |
249 | pr_warn("LTTng: error (%ld) adding tracepoint\n", | |
250 | PTR_ERR(e)); | |
251 | continue; | |
252 | } | |
253 | } | |
254 | /* If already enabled, just check consistency */ | |
255 | if (e->tp) { | |
256 | WARN_ON(e->tp != tp); | |
257 | continue; | |
258 | } | |
259 | e->tp = tp; | |
260 | e->refcount++; | |
261 | /* register each (probe, data) */ | |
262 | list_for_each_entry(p, &e->probes, list) { | |
263 | int ret; | |
264 | ||
265 | ret = tracepoint_probe_register(e->tp, | |
266 | p->tp_func.func, p->tp_func.data); | |
267 | WARN_ON_ONCE(ret); | |
268 | } | |
269 | } | |
270 | mutex_unlock(<tng_tracepoint_mutex); | |
271 | return 0; | |
272 | } | |
273 | ||
274 | static | |
275 | int lttng_tracepoint_going(struct tp_module *tp_mod) | |
276 | { | |
277 | int i; | |
278 | ||
279 | mutex_lock(<tng_tracepoint_mutex); | |
280 | for (i = 0; i < tp_mod->mod->num_tracepoints; i++) { | |
281 | struct tracepoint *tp; | |
282 | struct tracepoint_entry *e; | |
283 | struct lttng_tp_probe *p; | |
284 | ||
285 | tp = tp_mod->mod->tracepoints_ptrs[i]; | |
286 | e = get_tracepoint(tp->name); | |
287 | if (!e || !e->tp) | |
288 | continue; | |
289 | /* unregister each (probe, data) */ | |
290 | list_for_each_entry(p, &e->probes, list) { | |
291 | int ret; | |
292 | ||
293 | ret = tracepoint_probe_unregister(e->tp, | |
294 | p->tp_func.func, p->tp_func.data); | |
295 | WARN_ON_ONCE(ret); | |
296 | } | |
297 | e->tp = NULL; | |
298 | if (!--e->refcount) | |
299 | remove_tracepoint(e); | |
300 | } | |
301 | mutex_unlock(<tng_tracepoint_mutex); | |
302 | return 0; | |
303 | } | |
304 | ||
305 | static | |
306 | int lttng_tracepoint_notify(struct notifier_block *self, | |
307 | unsigned long val, void *data) | |
308 | { | |
309 | struct tp_module *tp_mod = data; | |
310 | int ret = 0; | |
311 | ||
312 | switch (val) { | |
313 | case MODULE_STATE_COMING: | |
314 | ret = lttng_tracepoint_coming(tp_mod); | |
315 | break; | |
316 | case MODULE_STATE_GOING: | |
317 | ret = lttng_tracepoint_going(tp_mod); | |
318 | break; | |
319 | default: | |
320 | break; | |
321 | } | |
322 | return ret; | |
323 | } | |
324 | ||
325 | static | |
326 | struct notifier_block lttng_tracepoint_notifier = { | |
327 | .notifier_call = lttng_tracepoint_notify, | |
328 | .priority = 0, | |
329 | }; | |
330 | ||
331 | static | |
332 | int lttng_tracepoint_module_init(void) | |
333 | { | |
334 | return register_tracepoint_module_notifier(<tng_tracepoint_notifier); | |
335 | } | |
336 | ||
337 | static | |
338 | void lttng_tracepoint_module_exit(void) | |
339 | { | |
340 | WARN_ON(unregister_tracepoint_module_notifier(<tng_tracepoint_notifier)); | |
341 | } | |
342 | ||
343 | #else /* #ifdef CONFIG_MODULES */ | |
344 | ||
345 | static | |
346 | int lttng_tracepoint_module_init(void) | |
347 | { | |
348 | return 0; | |
349 | } | |
350 | ||
351 | static | |
352 | void lttng_tracepoint_module_exit(void) | |
353 | { | |
354 | } | |
355 | ||
356 | #endif /* #else #ifdef CONFIG_MODULES */ | |
357 | ||
358 | static | |
359 | void lttng_kernel_tracepoint_add(struct tracepoint *tp, void *priv) | |
360 | { | |
361 | struct tracepoint_entry *e; | |
362 | struct lttng_tp_probe *p; | |
363 | int *ret = priv; | |
364 | ||
365 | mutex_lock(<tng_tracepoint_mutex); | |
366 | e = get_tracepoint(tp->name); | |
367 | if (!e) { | |
368 | e = add_tracepoint(tp->name); | |
369 | if (IS_ERR(e)) { | |
370 | pr_warn("LTTng: error (%ld) adding tracepoint\n", | |
371 | PTR_ERR(e)); | |
372 | *ret = (int) PTR_ERR(e); | |
373 | goto end; | |
374 | } | |
375 | } | |
376 | /* If already enabled, just check consistency */ | |
377 | if (e->tp) { | |
378 | WARN_ON(e->tp != tp); | |
379 | goto end; | |
380 | } | |
381 | e->tp = tp; | |
382 | e->refcount++; | |
383 | /* register each (probe, data) */ | |
384 | list_for_each_entry(p, &e->probes, list) { | |
385 | int ret; | |
386 | ||
387 | ret = tracepoint_probe_register(e->tp, | |
388 | p->tp_func.func, p->tp_func.data); | |
389 | WARN_ON_ONCE(ret); | |
390 | } | |
391 | end: | |
392 | mutex_unlock(<tng_tracepoint_mutex); | |
393 | } | |
394 | ||
395 | static | |
396 | void lttng_kernel_tracepoint_remove(struct tracepoint *tp, void *priv) | |
397 | { | |
398 | struct tracepoint_entry *e; | |
399 | int *ret = priv; | |
400 | ||
401 | mutex_lock(<tng_tracepoint_mutex); | |
402 | e = get_tracepoint(tp->name); | |
403 | if (!e || e->refcount != 1 || !list_empty(&e->probes)) { | |
404 | *ret = -EINVAL; | |
405 | goto end; | |
406 | } | |
407 | remove_tracepoint(e); | |
408 | end: | |
409 | mutex_unlock(<tng_tracepoint_mutex); | |
410 | } | |
411 | ||
412 | int __init lttng_tracepoint_init(void) | |
413 | { | |
414 | int ret = 0; | |
415 | ||
416 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_add, &ret); | |
417 | if (ret) | |
418 | goto error; | |
419 | ret = lttng_tracepoint_module_init(); | |
420 | if (ret) | |
421 | goto error_module; | |
422 | return 0; | |
423 | ||
424 | error_module: | |
425 | { | |
426 | int error_ret = 0; | |
427 | ||
428 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, | |
429 | &error_ret); | |
430 | WARN_ON(error_ret); | |
431 | } | |
432 | error: | |
433 | return ret; | |
434 | } | |
435 | ||
436 | void lttng_tracepoint_exit(void) | |
437 | { | |
438 | int i, ret = 0; | |
439 | ||
440 | lttng_tracepoint_module_exit(); | |
441 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, &ret); | |
442 | WARN_ON(ret); | |
443 | mutex_lock(<tng_tracepoint_mutex); | |
444 | for (i = 0; i < TRACEPOINT_TABLE_SIZE; i++) { | |
445 | struct hlist_head *head = &tracepoint_table[i]; | |
446 | ||
447 | /* All tracepoints should be removed */ | |
448 | WARN_ON(!hlist_empty(head)); | |
449 | } | |
450 | mutex_unlock(<tng_tracepoint_mutex); | |
451 | } |