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97e1c18e MD |
1 | /* |
2 | * Copyright (C) 2008 Mathieu Desnoyers | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | */ | |
18 | #include <linux/module.h> | |
19 | #include <linux/mutex.h> | |
20 | #include <linux/types.h> | |
21 | #include <linux/jhash.h> | |
22 | #include <linux/list.h> | |
23 | #include <linux/rcupdate.h> | |
24 | #include <linux/tracepoint.h> | |
25 | #include <linux/err.h> | |
26 | #include <linux/slab.h> | |
27 | ||
28 | extern struct tracepoint __start___tracepoints[]; | |
29 | extern struct tracepoint __stop___tracepoints[]; | |
30 | ||
31 | /* Set to 1 to enable tracepoint debug output */ | |
32 | static const int tracepoint_debug; | |
33 | ||
34 | /* | |
35 | * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the | |
36 | * builtin and module tracepoints and the hash table. | |
37 | */ | |
38 | static DEFINE_MUTEX(tracepoints_mutex); | |
39 | ||
40 | /* | |
41 | * Tracepoint hash table, containing the active tracepoints. | |
42 | * Protected by tracepoints_mutex. | |
43 | */ | |
44 | #define TRACEPOINT_HASH_BITS 6 | |
45 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) | |
19dba33c | 46 | static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; |
97e1c18e MD |
47 | |
48 | /* | |
49 | * Note about RCU : | |
50 | * It is used to to delay the free of multiple probes array until a quiescent | |
51 | * state is reached. | |
52 | * Tracepoint entries modifications are protected by the tracepoints_mutex. | |
53 | */ | |
54 | struct tracepoint_entry { | |
55 | struct hlist_node hlist; | |
56 | void **funcs; | |
57 | int refcount; /* Number of times armed. 0 if disarmed. */ | |
97e1c18e MD |
58 | char name[0]; |
59 | }; | |
60 | ||
19dba33c LJ |
61 | struct tp_probes { |
62 | struct rcu_head rcu; | |
63 | void *probes[0]; | |
64 | }; | |
97e1c18e | 65 | |
19dba33c | 66 | static inline void *allocate_probes(int count) |
97e1c18e | 67 | { |
19dba33c LJ |
68 | struct tp_probes *p = kmalloc(count * sizeof(void *) |
69 | + sizeof(struct tp_probes), GFP_KERNEL); | |
70 | return p == NULL ? NULL : p->probes; | |
97e1c18e MD |
71 | } |
72 | ||
19dba33c | 73 | static void rcu_free_old_probes(struct rcu_head *head) |
97e1c18e | 74 | { |
19dba33c LJ |
75 | kfree(container_of(head, struct tp_probes, rcu)); |
76 | } | |
77 | ||
78 | static inline void release_probes(void *old) | |
79 | { | |
80 | if (old) { | |
81 | struct tp_probes *tp_probes = container_of(old, | |
82 | struct tp_probes, probes[0]); | |
83 | call_rcu(&tp_probes->rcu, rcu_free_old_probes); | |
84 | } | |
97e1c18e MD |
85 | } |
86 | ||
87 | static void debug_print_probes(struct tracepoint_entry *entry) | |
88 | { | |
89 | int i; | |
90 | ||
19dba33c | 91 | if (!tracepoint_debug || !entry->funcs) |
97e1c18e MD |
92 | return; |
93 | ||
94 | for (i = 0; entry->funcs[i]; i++) | |
95 | printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i]); | |
96 | } | |
97 | ||
98 | static void * | |
99 | tracepoint_entry_add_probe(struct tracepoint_entry *entry, void *probe) | |
100 | { | |
101 | int nr_probes = 0; | |
102 | void **old, **new; | |
103 | ||
104 | WARN_ON(!probe); | |
105 | ||
106 | debug_print_probes(entry); | |
107 | old = entry->funcs; | |
108 | if (old) { | |
109 | /* (N -> N+1), (N != 0, 1) probes */ | |
110 | for (nr_probes = 0; old[nr_probes]; nr_probes++) | |
111 | if (old[nr_probes] == probe) | |
112 | return ERR_PTR(-EEXIST); | |
113 | } | |
114 | /* + 2 : one for new probe, one for NULL func */ | |
19dba33c | 115 | new = allocate_probes(nr_probes + 2); |
97e1c18e MD |
116 | if (new == NULL) |
117 | return ERR_PTR(-ENOMEM); | |
118 | if (old) | |
119 | memcpy(new, old, nr_probes * sizeof(void *)); | |
120 | new[nr_probes] = probe; | |
19dba33c | 121 | new[nr_probes + 1] = NULL; |
97e1c18e MD |
122 | entry->refcount = nr_probes + 1; |
123 | entry->funcs = new; | |
124 | debug_print_probes(entry); | |
125 | return old; | |
126 | } | |
127 | ||
128 | static void * | |
129 | tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe) | |
130 | { | |
131 | int nr_probes = 0, nr_del = 0, i; | |
132 | void **old, **new; | |
133 | ||
134 | old = entry->funcs; | |
135 | ||
f66af459 | 136 | if (!old) |
19dba33c | 137 | return ERR_PTR(-ENOENT); |
f66af459 | 138 | |
97e1c18e MD |
139 | debug_print_probes(entry); |
140 | /* (N -> M), (N > 1, M >= 0) probes */ | |
141 | for (nr_probes = 0; old[nr_probes]; nr_probes++) { | |
142 | if ((!probe || old[nr_probes] == probe)) | |
143 | nr_del++; | |
144 | } | |
145 | ||
146 | if (nr_probes - nr_del == 0) { | |
147 | /* N -> 0, (N > 1) */ | |
148 | entry->funcs = NULL; | |
149 | entry->refcount = 0; | |
150 | debug_print_probes(entry); | |
151 | return old; | |
152 | } else { | |
153 | int j = 0; | |
154 | /* N -> M, (N > 1, M > 0) */ | |
155 | /* + 1 for NULL */ | |
19dba33c | 156 | new = allocate_probes(nr_probes - nr_del + 1); |
97e1c18e MD |
157 | if (new == NULL) |
158 | return ERR_PTR(-ENOMEM); | |
159 | for (i = 0; old[i]; i++) | |
160 | if ((probe && old[i] != probe)) | |
161 | new[j++] = old[i]; | |
19dba33c | 162 | new[nr_probes - nr_del] = NULL; |
97e1c18e MD |
163 | entry->refcount = nr_probes - nr_del; |
164 | entry->funcs = new; | |
165 | } | |
166 | debug_print_probes(entry); | |
167 | return old; | |
168 | } | |
169 | ||
170 | /* | |
171 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. | |
172 | * Must be called with tracepoints_mutex held. | |
173 | * Returns NULL if not present. | |
174 | */ | |
175 | static struct tracepoint_entry *get_tracepoint(const char *name) | |
176 | { | |
177 | struct hlist_head *head; | |
178 | struct hlist_node *node; | |
179 | struct tracepoint_entry *e; | |
180 | u32 hash = jhash(name, strlen(name), 0); | |
181 | ||
9795302a | 182 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
97e1c18e MD |
183 | hlist_for_each_entry(e, node, head, hlist) { |
184 | if (!strcmp(name, e->name)) | |
185 | return e; | |
186 | } | |
187 | return NULL; | |
188 | } | |
189 | ||
190 | /* | |
191 | * Add the tracepoint to the tracepoint hash table. Must be called with | |
192 | * tracepoints_mutex held. | |
193 | */ | |
194 | static struct tracepoint_entry *add_tracepoint(const char *name) | |
195 | { | |
196 | struct hlist_head *head; | |
197 | struct hlist_node *node; | |
198 | struct tracepoint_entry *e; | |
199 | size_t name_len = strlen(name) + 1; | |
200 | u32 hash = jhash(name, name_len-1, 0); | |
201 | ||
9795302a | 202 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
97e1c18e MD |
203 | hlist_for_each_entry(e, node, head, hlist) { |
204 | if (!strcmp(name, e->name)) { | |
205 | printk(KERN_NOTICE | |
206 | "tracepoint %s busy\n", name); | |
207 | return ERR_PTR(-EEXIST); /* Already there */ | |
208 | } | |
209 | } | |
210 | /* | |
211 | * Using kmalloc here to allocate a variable length element. Could | |
212 | * cause some memory fragmentation if overused. | |
213 | */ | |
214 | e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL); | |
215 | if (!e) | |
216 | return ERR_PTR(-ENOMEM); | |
217 | memcpy(&e->name[0], name, name_len); | |
218 | e->funcs = NULL; | |
219 | e->refcount = 0; | |
97e1c18e MD |
220 | hlist_add_head(&e->hlist, head); |
221 | return e; | |
222 | } | |
223 | ||
224 | /* | |
225 | * Remove the tracepoint from the tracepoint hash table. Must be called with | |
226 | * mutex_lock held. | |
227 | */ | |
19dba33c | 228 | static inline void remove_tracepoint(struct tracepoint_entry *e) |
97e1c18e | 229 | { |
97e1c18e | 230 | hlist_del(&e->hlist); |
97e1c18e | 231 | kfree(e); |
97e1c18e MD |
232 | } |
233 | ||
234 | /* | |
235 | * Sets the probe callback corresponding to one tracepoint. | |
236 | */ | |
237 | static void set_tracepoint(struct tracepoint_entry **entry, | |
238 | struct tracepoint *elem, int active) | |
239 | { | |
240 | WARN_ON(strcmp((*entry)->name, elem->name) != 0); | |
241 | ||
242 | /* | |
243 | * rcu_assign_pointer has a smp_wmb() which makes sure that the new | |
244 | * probe callbacks array is consistent before setting a pointer to it. | |
245 | * This array is referenced by __DO_TRACE from | |
246 | * include/linux/tracepoints.h. A matching smp_read_barrier_depends() | |
247 | * is used. | |
248 | */ | |
249 | rcu_assign_pointer(elem->funcs, (*entry)->funcs); | |
250 | elem->state = active; | |
251 | } | |
252 | ||
253 | /* | |
254 | * Disable a tracepoint and its probe callback. | |
255 | * Note: only waiting an RCU period after setting elem->call to the empty | |
256 | * function insures that the original callback is not used anymore. This insured | |
257 | * by preempt_disable around the call site. | |
258 | */ | |
259 | static void disable_tracepoint(struct tracepoint *elem) | |
260 | { | |
261 | elem->state = 0; | |
262 | } | |
263 | ||
264 | /** | |
265 | * tracepoint_update_probe_range - Update a probe range | |
266 | * @begin: beginning of the range | |
267 | * @end: end of the range | |
268 | * | |
269 | * Updates the probe callback corresponding to a range of tracepoints. | |
270 | */ | |
271 | void tracepoint_update_probe_range(struct tracepoint *begin, | |
272 | struct tracepoint *end) | |
273 | { | |
274 | struct tracepoint *iter; | |
275 | struct tracepoint_entry *mark_entry; | |
276 | ||
277 | mutex_lock(&tracepoints_mutex); | |
278 | for (iter = begin; iter < end; iter++) { | |
279 | mark_entry = get_tracepoint(iter->name); | |
280 | if (mark_entry) { | |
281 | set_tracepoint(&mark_entry, iter, | |
282 | !!mark_entry->refcount); | |
283 | } else { | |
284 | disable_tracepoint(iter); | |
285 | } | |
286 | } | |
287 | mutex_unlock(&tracepoints_mutex); | |
288 | } | |
289 | ||
290 | /* | |
291 | * Update probes, removing the faulty probes. | |
292 | */ | |
293 | static void tracepoint_update_probes(void) | |
294 | { | |
295 | /* Core kernel tracepoints */ | |
296 | tracepoint_update_probe_range(__start___tracepoints, | |
297 | __stop___tracepoints); | |
298 | /* tracepoints in modules. */ | |
299 | module_update_tracepoints(); | |
300 | } | |
301 | ||
302 | /** | |
303 | * tracepoint_probe_register - Connect a probe to a tracepoint | |
304 | * @name: tracepoint name | |
305 | * @probe: probe handler | |
306 | * | |
307 | * Returns 0 if ok, error value on error. | |
308 | * The probe address must at least be aligned on the architecture pointer size. | |
309 | */ | |
310 | int tracepoint_probe_register(const char *name, void *probe) | |
311 | { | |
312 | struct tracepoint_entry *entry; | |
313 | int ret = 0; | |
314 | void *old; | |
315 | ||
316 | mutex_lock(&tracepoints_mutex); | |
317 | entry = get_tracepoint(name); | |
318 | if (!entry) { | |
319 | entry = add_tracepoint(name); | |
320 | if (IS_ERR(entry)) { | |
321 | ret = PTR_ERR(entry); | |
322 | goto end; | |
323 | } | |
324 | } | |
97e1c18e MD |
325 | old = tracepoint_entry_add_probe(entry, probe); |
326 | if (IS_ERR(old)) { | |
19dba33c LJ |
327 | if (!entry->refcount) |
328 | remove_tracepoint(entry); | |
97e1c18e MD |
329 | ret = PTR_ERR(old); |
330 | goto end; | |
331 | } | |
332 | mutex_unlock(&tracepoints_mutex); | |
333 | tracepoint_update_probes(); /* may update entry */ | |
19dba33c LJ |
334 | release_probes(old); |
335 | return 0; | |
97e1c18e MD |
336 | end: |
337 | mutex_unlock(&tracepoints_mutex); | |
338 | return ret; | |
339 | } | |
340 | EXPORT_SYMBOL_GPL(tracepoint_probe_register); | |
341 | ||
342 | /** | |
343 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint | |
344 | * @name: tracepoint name | |
345 | * @probe: probe function pointer | |
346 | * | |
347 | * We do not need to call a synchronize_sched to make sure the probes have | |
348 | * finished running before doing a module unload, because the module unload | |
349 | * itself uses stop_machine(), which insures that every preempt disabled section | |
350 | * have finished. | |
351 | */ | |
352 | int tracepoint_probe_unregister(const char *name, void *probe) | |
353 | { | |
354 | struct tracepoint_entry *entry; | |
355 | void *old; | |
356 | int ret = -ENOENT; | |
357 | ||
358 | mutex_lock(&tracepoints_mutex); | |
359 | entry = get_tracepoint(name); | |
360 | if (!entry) | |
361 | goto end; | |
97e1c18e | 362 | old = tracepoint_entry_remove_probe(entry, probe); |
19dba33c LJ |
363 | if (IS_ERR(old)) { |
364 | ret = PTR_ERR(old); | |
f66af459 FW |
365 | goto end; |
366 | } | |
19dba33c LJ |
367 | if (!entry->refcount) |
368 | remove_tracepoint(entry); | |
97e1c18e MD |
369 | mutex_unlock(&tracepoints_mutex); |
370 | tracepoint_update_probes(); /* may update entry */ | |
19dba33c LJ |
371 | release_probes(old); |
372 | return 0; | |
97e1c18e MD |
373 | end: |
374 | mutex_unlock(&tracepoints_mutex); | |
375 | return ret; | |
376 | } | |
377 | EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); | |
378 | ||
379 | /** | |
380 | * tracepoint_get_iter_range - Get a next tracepoint iterator given a range. | |
381 | * @tracepoint: current tracepoints (in), next tracepoint (out) | |
382 | * @begin: beginning of the range | |
383 | * @end: end of the range | |
384 | * | |
385 | * Returns whether a next tracepoint has been found (1) or not (0). | |
386 | * Will return the first tracepoint in the range if the input tracepoint is | |
387 | * NULL. | |
388 | */ | |
389 | int tracepoint_get_iter_range(struct tracepoint **tracepoint, | |
390 | struct tracepoint *begin, struct tracepoint *end) | |
391 | { | |
392 | if (!*tracepoint && begin != end) { | |
393 | *tracepoint = begin; | |
394 | return 1; | |
395 | } | |
396 | if (*tracepoint >= begin && *tracepoint < end) | |
397 | return 1; | |
398 | return 0; | |
399 | } | |
400 | EXPORT_SYMBOL_GPL(tracepoint_get_iter_range); | |
401 | ||
402 | static void tracepoint_get_iter(struct tracepoint_iter *iter) | |
403 | { | |
404 | int found = 0; | |
405 | ||
406 | /* Core kernel tracepoints */ | |
407 | if (!iter->module) { | |
408 | found = tracepoint_get_iter_range(&iter->tracepoint, | |
409 | __start___tracepoints, __stop___tracepoints); | |
410 | if (found) | |
411 | goto end; | |
412 | } | |
413 | /* tracepoints in modules. */ | |
414 | found = module_get_iter_tracepoints(iter); | |
415 | end: | |
416 | if (!found) | |
417 | tracepoint_iter_reset(iter); | |
418 | } | |
419 | ||
420 | void tracepoint_iter_start(struct tracepoint_iter *iter) | |
421 | { | |
422 | tracepoint_get_iter(iter); | |
423 | } | |
424 | EXPORT_SYMBOL_GPL(tracepoint_iter_start); | |
425 | ||
426 | void tracepoint_iter_next(struct tracepoint_iter *iter) | |
427 | { | |
428 | iter->tracepoint++; | |
429 | /* | |
430 | * iter->tracepoint may be invalid because we blindly incremented it. | |
431 | * Make sure it is valid by marshalling on the tracepoints, getting the | |
432 | * tracepoints from following modules if necessary. | |
433 | */ | |
434 | tracepoint_get_iter(iter); | |
435 | } | |
436 | EXPORT_SYMBOL_GPL(tracepoint_iter_next); | |
437 | ||
438 | void tracepoint_iter_stop(struct tracepoint_iter *iter) | |
439 | { | |
440 | } | |
441 | EXPORT_SYMBOL_GPL(tracepoint_iter_stop); | |
442 | ||
443 | void tracepoint_iter_reset(struct tracepoint_iter *iter) | |
444 | { | |
445 | iter->module = NULL; | |
446 | iter->tracepoint = NULL; | |
447 | } | |
448 | EXPORT_SYMBOL_GPL(tracepoint_iter_reset); |