blob: c8e7cc0e6ff6e1999e5bec415f979bde991da2ff
1 | /* |
2 | * Copyright (C) 2008-2014 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 | #include <linux/sched.h> |
28 | #include <linux/static_key.h> |
29 | |
30 | extern struct tracepoint * const __start___tracepoints_ptrs[]; |
31 | extern struct tracepoint * const __stop___tracepoints_ptrs[]; |
32 | |
33 | /* Set to 1 to enable tracepoint debug output */ |
34 | static const int tracepoint_debug; |
35 | |
36 | #ifdef CONFIG_MODULES |
37 | /* |
38 | * Tracepoint module list mutex protects the local module list. |
39 | */ |
40 | static DEFINE_MUTEX(tracepoint_module_list_mutex); |
41 | |
42 | /* Local list of struct tp_module */ |
43 | static LIST_HEAD(tracepoint_module_list); |
44 | #endif /* CONFIG_MODULES */ |
45 | |
46 | /* |
47 | * tracepoints_mutex protects the builtin and module tracepoints. |
48 | * tracepoints_mutex nests inside tracepoint_module_list_mutex. |
49 | */ |
50 | static DEFINE_MUTEX(tracepoints_mutex); |
51 | |
52 | /* |
53 | * Note about RCU : |
54 | * It is used to delay the free of multiple probes array until a quiescent |
55 | * state is reached. |
56 | */ |
57 | struct tp_probes { |
58 | struct rcu_head rcu; |
59 | struct tracepoint_func probes[0]; |
60 | }; |
61 | |
62 | static inline void *allocate_probes(int count) |
63 | { |
64 | struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func) |
65 | + sizeof(struct tp_probes), GFP_KERNEL); |
66 | return p == NULL ? NULL : p->probes; |
67 | } |
68 | |
69 | static void rcu_free_old_probes(struct rcu_head *head) |
70 | { |
71 | kfree(container_of(head, struct tp_probes, rcu)); |
72 | } |
73 | |
74 | static inline void release_probes(struct tracepoint_func *old) |
75 | { |
76 | if (old) { |
77 | struct tp_probes *tp_probes = container_of(old, |
78 | struct tp_probes, probes[0]); |
79 | call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes); |
80 | } |
81 | } |
82 | |
83 | static void debug_print_probes(struct tracepoint_func *funcs) |
84 | { |
85 | int i; |
86 | |
87 | if (!tracepoint_debug || !funcs) |
88 | return; |
89 | |
90 | for (i = 0; funcs[i].func; i++) |
91 | printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func); |
92 | } |
93 | |
94 | static struct tracepoint_func * |
95 | func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func, |
96 | int prio) |
97 | { |
98 | struct tracepoint_func *old, *new; |
99 | int nr_probes = 0; |
100 | int pos = -1; |
101 | |
102 | if (WARN_ON(!tp_func->func)) |
103 | return ERR_PTR(-EINVAL); |
104 | |
105 | debug_print_probes(*funcs); |
106 | old = *funcs; |
107 | if (old) { |
108 | /* (N -> N+1), (N != 0, 1) probes */ |
109 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
110 | /* Insert before probes of lower priority */ |
111 | if (pos < 0 && old[nr_probes].prio < prio) |
112 | pos = nr_probes; |
113 | if (old[nr_probes].func == tp_func->func && |
114 | old[nr_probes].data == tp_func->data) |
115 | return ERR_PTR(-EEXIST); |
116 | } |
117 | } |
118 | /* + 2 : one for new probe, one for NULL func */ |
119 | new = allocate_probes(nr_probes + 2); |
120 | if (new == NULL) |
121 | return ERR_PTR(-ENOMEM); |
122 | if (old) { |
123 | if (pos < 0) { |
124 | pos = nr_probes; |
125 | memcpy(new, old, nr_probes * sizeof(struct tracepoint_func)); |
126 | } else { |
127 | /* Copy higher priority probes ahead of the new probe */ |
128 | memcpy(new, old, pos * sizeof(struct tracepoint_func)); |
129 | /* Copy the rest after it. */ |
130 | memcpy(new + pos + 1, old + pos, |
131 | (nr_probes - pos) * sizeof(struct tracepoint_func)); |
132 | } |
133 | } else |
134 | pos = 0; |
135 | new[pos] = *tp_func; |
136 | new[nr_probes + 1].func = NULL; |
137 | *funcs = new; |
138 | debug_print_probes(*funcs); |
139 | return old; |
140 | } |
141 | |
142 | static void *func_remove(struct tracepoint_func **funcs, |
143 | struct tracepoint_func *tp_func) |
144 | { |
145 | int nr_probes = 0, nr_del = 0, i; |
146 | struct tracepoint_func *old, *new; |
147 | |
148 | old = *funcs; |
149 | |
150 | if (!old) |
151 | return ERR_PTR(-ENOENT); |
152 | |
153 | debug_print_probes(*funcs); |
154 | /* (N -> M), (N > 1, M >= 0) probes */ |
155 | if (tp_func->func) { |
156 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
157 | if (old[nr_probes].func == tp_func->func && |
158 | old[nr_probes].data == tp_func->data) |
159 | nr_del++; |
160 | } |
161 | } |
162 | |
163 | /* |
164 | * If probe is NULL, then nr_probes = nr_del = 0, and then the |
165 | * entire entry will be removed. |
166 | */ |
167 | if (nr_probes - nr_del == 0) { |
168 | /* N -> 0, (N > 1) */ |
169 | *funcs = NULL; |
170 | debug_print_probes(*funcs); |
171 | return old; |
172 | } else { |
173 | int j = 0; |
174 | /* N -> M, (N > 1, M > 0) */ |
175 | /* + 1 for NULL */ |
176 | new = allocate_probes(nr_probes - nr_del + 1); |
177 | if (new == NULL) |
178 | return ERR_PTR(-ENOMEM); |
179 | for (i = 0; old[i].func; i++) |
180 | if (old[i].func != tp_func->func |
181 | || old[i].data != tp_func->data) |
182 | new[j++] = old[i]; |
183 | new[nr_probes - nr_del].func = NULL; |
184 | *funcs = new; |
185 | } |
186 | debug_print_probes(*funcs); |
187 | return old; |
188 | } |
189 | |
190 | /* |
191 | * Add the probe function to a tracepoint. |
192 | */ |
193 | static int tracepoint_add_func(struct tracepoint *tp, |
194 | struct tracepoint_func *func, int prio) |
195 | { |
196 | struct tracepoint_func *old, *tp_funcs; |
197 | |
198 | if (tp->regfunc && !static_key_enabled(&tp->key)) |
199 | tp->regfunc(); |
200 | |
201 | tp_funcs = rcu_dereference_protected(tp->funcs, |
202 | lockdep_is_held(&tracepoints_mutex)); |
203 | old = func_add(&tp_funcs, func, prio); |
204 | if (IS_ERR(old)) { |
205 | WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM); |
206 | return PTR_ERR(old); |
207 | } |
208 | |
209 | /* |
210 | * rcu_assign_pointer has a smp_wmb() which makes sure that the new |
211 | * probe callbacks array is consistent before setting a pointer to it. |
212 | * This array is referenced by __DO_TRACE from |
213 | * include/linux/tracepoints.h. A matching smp_read_barrier_depends() |
214 | * is used. |
215 | */ |
216 | rcu_assign_pointer(tp->funcs, tp_funcs); |
217 | if (!static_key_enabled(&tp->key)) |
218 | static_key_slow_inc(&tp->key); |
219 | release_probes(old); |
220 | return 0; |
221 | } |
222 | |
223 | /* |
224 | * Remove a probe function from a tracepoint. |
225 | * Note: only waiting an RCU period after setting elem->call to the empty |
226 | * function insures that the original callback is not used anymore. This insured |
227 | * by preempt_disable around the call site. |
228 | */ |
229 | static int tracepoint_remove_func(struct tracepoint *tp, |
230 | struct tracepoint_func *func) |
231 | { |
232 | struct tracepoint_func *old, *tp_funcs; |
233 | |
234 | tp_funcs = rcu_dereference_protected(tp->funcs, |
235 | lockdep_is_held(&tracepoints_mutex)); |
236 | old = func_remove(&tp_funcs, func); |
237 | if (IS_ERR(old)) { |
238 | WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM); |
239 | return PTR_ERR(old); |
240 | } |
241 | |
242 | if (!tp_funcs) { |
243 | /* Removed last function */ |
244 | if (tp->unregfunc && static_key_enabled(&tp->key)) |
245 | tp->unregfunc(); |
246 | |
247 | if (static_key_enabled(&tp->key)) |
248 | static_key_slow_dec(&tp->key); |
249 | } |
250 | rcu_assign_pointer(tp->funcs, tp_funcs); |
251 | release_probes(old); |
252 | return 0; |
253 | } |
254 | |
255 | /** |
256 | * tracepoint_probe_register - Connect a probe to a tracepoint |
257 | * @tp: tracepoint |
258 | * @probe: probe handler |
259 | * @data: tracepoint data |
260 | * @prio: priority of this function over other registered functions |
261 | * |
262 | * Returns 0 if ok, error value on error. |
263 | * Note: if @tp is within a module, the caller is responsible for |
264 | * unregistering the probe before the module is gone. This can be |
265 | * performed either with a tracepoint module going notifier, or from |
266 | * within module exit functions. |
267 | */ |
268 | int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, |
269 | void *data, int prio) |
270 | { |
271 | struct tracepoint_func tp_func; |
272 | int ret; |
273 | |
274 | mutex_lock(&tracepoints_mutex); |
275 | tp_func.func = probe; |
276 | tp_func.data = data; |
277 | tp_func.prio = prio; |
278 | ret = tracepoint_add_func(tp, &tp_func, prio); |
279 | mutex_unlock(&tracepoints_mutex); |
280 | return ret; |
281 | } |
282 | EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio); |
283 | |
284 | /** |
285 | * tracepoint_probe_register - Connect a probe to a tracepoint |
286 | * @tp: tracepoint |
287 | * @probe: probe handler |
288 | * @data: tracepoint data |
289 | * @prio: priority of this function over other registered functions |
290 | * |
291 | * Returns 0 if ok, error value on error. |
292 | * Note: if @tp is within a module, the caller is responsible for |
293 | * unregistering the probe before the module is gone. This can be |
294 | * performed either with a tracepoint module going notifier, or from |
295 | * within module exit functions. |
296 | */ |
297 | int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data) |
298 | { |
299 | return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO); |
300 | } |
301 | EXPORT_SYMBOL_GPL(tracepoint_probe_register); |
302 | |
303 | /** |
304 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint |
305 | * @tp: tracepoint |
306 | * @probe: probe function pointer |
307 | * @data: tracepoint data |
308 | * |
309 | * Returns 0 if ok, error value on error. |
310 | */ |
311 | int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data) |
312 | { |
313 | struct tracepoint_func tp_func; |
314 | int ret; |
315 | |
316 | mutex_lock(&tracepoints_mutex); |
317 | tp_func.func = probe; |
318 | tp_func.data = data; |
319 | ret = tracepoint_remove_func(tp, &tp_func); |
320 | mutex_unlock(&tracepoints_mutex); |
321 | return ret; |
322 | } |
323 | EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); |
324 | |
325 | #ifdef CONFIG_MODULES |
326 | bool trace_module_has_bad_taint(struct module *mod) |
327 | { |
328 | return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) | |
329 | (1 << TAINT_UNSIGNED_MODULE)); |
330 | } |
331 | |
332 | static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list); |
333 | |
334 | /** |
335 | * register_tracepoint_notifier - register tracepoint coming/going notifier |
336 | * @nb: notifier block |
337 | * |
338 | * Notifiers registered with this function are called on module |
339 | * coming/going with the tracepoint_module_list_mutex held. |
340 | * The notifier block callback should expect a "struct tp_module" data |
341 | * pointer. |
342 | */ |
343 | int register_tracepoint_module_notifier(struct notifier_block *nb) |
344 | { |
345 | struct tp_module *tp_mod; |
346 | int ret; |
347 | |
348 | mutex_lock(&tracepoint_module_list_mutex); |
349 | ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb); |
350 | if (ret) |
351 | goto end; |
352 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) |
353 | (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod); |
354 | end: |
355 | mutex_unlock(&tracepoint_module_list_mutex); |
356 | return ret; |
357 | } |
358 | EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier); |
359 | |
360 | /** |
361 | * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier |
362 | * @nb: notifier block |
363 | * |
364 | * The notifier block callback should expect a "struct tp_module" data |
365 | * pointer. |
366 | */ |
367 | int unregister_tracepoint_module_notifier(struct notifier_block *nb) |
368 | { |
369 | struct tp_module *tp_mod; |
370 | int ret; |
371 | |
372 | mutex_lock(&tracepoint_module_list_mutex); |
373 | ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb); |
374 | if (ret) |
375 | goto end; |
376 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) |
377 | (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod); |
378 | end: |
379 | mutex_unlock(&tracepoint_module_list_mutex); |
380 | return ret; |
381 | |
382 | } |
383 | EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier); |
384 | |
385 | /* |
386 | * Ensure the tracer unregistered the module's probes before the module |
387 | * teardown is performed. Prevents leaks of probe and data pointers. |
388 | */ |
389 | static void tp_module_going_check_quiescent(struct tracepoint * const *begin, |
390 | struct tracepoint * const *end) |
391 | { |
392 | struct tracepoint * const *iter; |
393 | |
394 | if (!begin) |
395 | return; |
396 | for (iter = begin; iter < end; iter++) |
397 | WARN_ON_ONCE((*iter)->funcs); |
398 | } |
399 | |
400 | static int tracepoint_module_coming(struct module *mod) |
401 | { |
402 | struct tp_module *tp_mod; |
403 | int ret = 0; |
404 | |
405 | if (!mod->num_tracepoints) |
406 | return 0; |
407 | |
408 | /* |
409 | * We skip modules that taint the kernel, especially those with different |
410 | * module headers (for forced load), to make sure we don't cause a crash. |
411 | * Staging, out-of-tree, and unsigned GPL modules are fine. |
412 | */ |
413 | if (trace_module_has_bad_taint(mod)) |
414 | return 0; |
415 | mutex_lock(&tracepoint_module_list_mutex); |
416 | tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL); |
417 | if (!tp_mod) { |
418 | ret = -ENOMEM; |
419 | goto end; |
420 | } |
421 | tp_mod->mod = mod; |
422 | list_add_tail(&tp_mod->list, &tracepoint_module_list); |
423 | blocking_notifier_call_chain(&tracepoint_notify_list, |
424 | MODULE_STATE_COMING, tp_mod); |
425 | end: |
426 | mutex_unlock(&tracepoint_module_list_mutex); |
427 | return ret; |
428 | } |
429 | |
430 | static void tracepoint_module_going(struct module *mod) |
431 | { |
432 | struct tp_module *tp_mod; |
433 | |
434 | if (!mod->num_tracepoints) |
435 | return; |
436 | |
437 | mutex_lock(&tracepoint_module_list_mutex); |
438 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) { |
439 | if (tp_mod->mod == mod) { |
440 | blocking_notifier_call_chain(&tracepoint_notify_list, |
441 | MODULE_STATE_GOING, tp_mod); |
442 | list_del(&tp_mod->list); |
443 | kfree(tp_mod); |
444 | /* |
445 | * Called the going notifier before checking for |
446 | * quiescence. |
447 | */ |
448 | tp_module_going_check_quiescent(mod->tracepoints_ptrs, |
449 | mod->tracepoints_ptrs + mod->num_tracepoints); |
450 | break; |
451 | } |
452 | } |
453 | /* |
454 | * In the case of modules that were tainted at "coming", we'll simply |
455 | * walk through the list without finding it. We cannot use the "tainted" |
456 | * flag on "going", in case a module taints the kernel only after being |
457 | * loaded. |
458 | */ |
459 | mutex_unlock(&tracepoint_module_list_mutex); |
460 | } |
461 | |
462 | static int tracepoint_module_notify(struct notifier_block *self, |
463 | unsigned long val, void *data) |
464 | { |
465 | struct module *mod = data; |
466 | int ret = 0; |
467 | |
468 | switch (val) { |
469 | case MODULE_STATE_COMING: |
470 | ret = tracepoint_module_coming(mod); |
471 | break; |
472 | case MODULE_STATE_LIVE: |
473 | break; |
474 | case MODULE_STATE_GOING: |
475 | tracepoint_module_going(mod); |
476 | break; |
477 | case MODULE_STATE_UNFORMED: |
478 | break; |
479 | } |
480 | return ret; |
481 | } |
482 | |
483 | static struct notifier_block tracepoint_module_nb = { |
484 | .notifier_call = tracepoint_module_notify, |
485 | .priority = 0, |
486 | }; |
487 | |
488 | static __init int init_tracepoints(void) |
489 | { |
490 | int ret; |
491 | |
492 | ret = register_module_notifier(&tracepoint_module_nb); |
493 | if (ret) |
494 | pr_warn("Failed to register tracepoint module enter notifier\n"); |
495 | |
496 | return ret; |
497 | } |
498 | __initcall(init_tracepoints); |
499 | #endif /* CONFIG_MODULES */ |
500 | |
501 | static void for_each_tracepoint_range(struct tracepoint * const *begin, |
502 | struct tracepoint * const *end, |
503 | void (*fct)(struct tracepoint *tp, void *priv), |
504 | void *priv) |
505 | { |
506 | struct tracepoint * const *iter; |
507 | |
508 | if (!begin) |
509 | return; |
510 | for (iter = begin; iter < end; iter++) |
511 | fct(*iter, priv); |
512 | } |
513 | |
514 | /** |
515 | * for_each_kernel_tracepoint - iteration on all kernel tracepoints |
516 | * @fct: callback |
517 | * @priv: private data |
518 | */ |
519 | void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv), |
520 | void *priv) |
521 | { |
522 | for_each_tracepoint_range(__start___tracepoints_ptrs, |
523 | __stop___tracepoints_ptrs, fct, priv); |
524 | } |
525 | EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint); |
526 | |
527 | #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS |
528 | |
529 | /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ |
530 | static int sys_tracepoint_refcount; |
531 | |
532 | void syscall_regfunc(void) |
533 | { |
534 | struct task_struct *p, *t; |
535 | |
536 | if (!sys_tracepoint_refcount) { |
537 | read_lock(&tasklist_lock); |
538 | for_each_process_thread(p, t) { |
539 | set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
540 | } |
541 | read_unlock(&tasklist_lock); |
542 | } |
543 | sys_tracepoint_refcount++; |
544 | } |
545 | |
546 | void syscall_unregfunc(void) |
547 | { |
548 | struct task_struct *p, *t; |
549 | |
550 | sys_tracepoint_refcount--; |
551 | if (!sys_tracepoint_refcount) { |
552 | read_lock(&tasklist_lock); |
553 | for_each_process_thread(p, t) { |
554 | clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
555 | } |
556 | read_unlock(&tasklist_lock); |
557 | } |
558 | } |
559 | #endif |
560 |