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