]> git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - kernel/tracepoint.c
Input: atmel_mxt_ts - add additional bootloader addresses
[mirror_ubuntu-artful-kernel.git] / kernel / tracepoint.c
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 *
243 * Returns 0 if ok, error value on error.
244 * Note: if @tp is within a module, the caller is responsible for
245 * unregistering the probe before the module is gone. This can be
246 * performed either with a tracepoint module going notifier, or from
247 * within module exit functions.
248 */
249 int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
250 {
251 struct tracepoint_func tp_func;
252 int ret;
253
254 mutex_lock(&tracepoints_mutex);
255 tp_func.func = probe;
256 tp_func.data = data;
257 ret = tracepoint_add_func(tp, &tp_func);
258 mutex_unlock(&tracepoints_mutex);
259 return ret;
260 }
261 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
262
263 /**
264 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
265 * @tp: tracepoint
266 * @probe: probe function pointer
267 *
268 * Returns 0 if ok, error value on error.
269 */
270 int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
271 {
272 struct tracepoint_func tp_func;
273 int ret;
274
275 mutex_lock(&tracepoints_mutex);
276 tp_func.func = probe;
277 tp_func.data = data;
278 ret = tracepoint_remove_func(tp, &tp_func);
279 mutex_unlock(&tracepoints_mutex);
280 return ret;
281 }
282 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
283
284 #ifdef CONFIG_MODULES
285 bool trace_module_has_bad_taint(struct module *mod)
286 {
287 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
288 (1 << TAINT_UNSIGNED_MODULE));
289 }
290
291 static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
292
293 /**
294 * register_tracepoint_notifier - register tracepoint coming/going notifier
295 * @nb: notifier block
296 *
297 * Notifiers registered with this function are called on module
298 * coming/going with the tracepoint_module_list_mutex held.
299 * The notifier block callback should expect a "struct tp_module" data
300 * pointer.
301 */
302 int register_tracepoint_module_notifier(struct notifier_block *nb)
303 {
304 struct tp_module *tp_mod;
305 int ret;
306
307 mutex_lock(&tracepoint_module_list_mutex);
308 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
309 if (ret)
310 goto end;
311 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
312 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
313 end:
314 mutex_unlock(&tracepoint_module_list_mutex);
315 return ret;
316 }
317 EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
318
319 /**
320 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
321 * @nb: notifier block
322 *
323 * The notifier block callback should expect a "struct tp_module" data
324 * pointer.
325 */
326 int unregister_tracepoint_module_notifier(struct notifier_block *nb)
327 {
328 struct tp_module *tp_mod;
329 int ret;
330
331 mutex_lock(&tracepoint_module_list_mutex);
332 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
333 if (ret)
334 goto end;
335 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
336 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
337 end:
338 mutex_unlock(&tracepoint_module_list_mutex);
339 return ret;
340
341 }
342 EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
343
344 /*
345 * Ensure the tracer unregistered the module's probes before the module
346 * teardown is performed. Prevents leaks of probe and data pointers.
347 */
348 static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
349 struct tracepoint * const *end)
350 {
351 struct tracepoint * const *iter;
352
353 if (!begin)
354 return;
355 for (iter = begin; iter < end; iter++)
356 WARN_ON_ONCE((*iter)->funcs);
357 }
358
359 static int tracepoint_module_coming(struct module *mod)
360 {
361 struct tp_module *tp_mod;
362 int ret = 0;
363
364 if (!mod->num_tracepoints)
365 return 0;
366
367 /*
368 * We skip modules that taint the kernel, especially those with different
369 * module headers (for forced load), to make sure we don't cause a crash.
370 * Staging, out-of-tree, and unsigned GPL modules are fine.
371 */
372 if (trace_module_has_bad_taint(mod))
373 return 0;
374 mutex_lock(&tracepoint_module_list_mutex);
375 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
376 if (!tp_mod) {
377 ret = -ENOMEM;
378 goto end;
379 }
380 tp_mod->mod = mod;
381 list_add_tail(&tp_mod->list, &tracepoint_module_list);
382 blocking_notifier_call_chain(&tracepoint_notify_list,
383 MODULE_STATE_COMING, tp_mod);
384 end:
385 mutex_unlock(&tracepoint_module_list_mutex);
386 return ret;
387 }
388
389 static void tracepoint_module_going(struct module *mod)
390 {
391 struct tp_module *tp_mod;
392
393 if (!mod->num_tracepoints)
394 return;
395
396 mutex_lock(&tracepoint_module_list_mutex);
397 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
398 if (tp_mod->mod == mod) {
399 blocking_notifier_call_chain(&tracepoint_notify_list,
400 MODULE_STATE_GOING, tp_mod);
401 list_del(&tp_mod->list);
402 kfree(tp_mod);
403 /*
404 * Called the going notifier before checking for
405 * quiescence.
406 */
407 tp_module_going_check_quiescent(mod->tracepoints_ptrs,
408 mod->tracepoints_ptrs + mod->num_tracepoints);
409 break;
410 }
411 }
412 /*
413 * In the case of modules that were tainted at "coming", we'll simply
414 * walk through the list without finding it. We cannot use the "tainted"
415 * flag on "going", in case a module taints the kernel only after being
416 * loaded.
417 */
418 mutex_unlock(&tracepoint_module_list_mutex);
419 }
420
421 static int tracepoint_module_notify(struct notifier_block *self,
422 unsigned long val, void *data)
423 {
424 struct module *mod = data;
425 int ret = 0;
426
427 switch (val) {
428 case MODULE_STATE_COMING:
429 ret = tracepoint_module_coming(mod);
430 break;
431 case MODULE_STATE_LIVE:
432 break;
433 case MODULE_STATE_GOING:
434 tracepoint_module_going(mod);
435 break;
436 case MODULE_STATE_UNFORMED:
437 break;
438 }
439 return ret;
440 }
441
442 static struct notifier_block tracepoint_module_nb = {
443 .notifier_call = tracepoint_module_notify,
444 .priority = 0,
445 };
446
447 static __init int init_tracepoints(void)
448 {
449 int ret;
450
451 ret = register_module_notifier(&tracepoint_module_nb);
452 if (ret)
453 pr_warning("Failed to register tracepoint module enter notifier\n");
454
455 return ret;
456 }
457 __initcall(init_tracepoints);
458 #endif /* CONFIG_MODULES */
459
460 static void for_each_tracepoint_range(struct tracepoint * const *begin,
461 struct tracepoint * const *end,
462 void (*fct)(struct tracepoint *tp, void *priv),
463 void *priv)
464 {
465 struct tracepoint * const *iter;
466
467 if (!begin)
468 return;
469 for (iter = begin; iter < end; iter++)
470 fct(*iter, priv);
471 }
472
473 /**
474 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
475 * @fct: callback
476 * @priv: private data
477 */
478 void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
479 void *priv)
480 {
481 for_each_tracepoint_range(__start___tracepoints_ptrs,
482 __stop___tracepoints_ptrs, fct, priv);
483 }
484 EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
485
486 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
487
488 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
489 static int sys_tracepoint_refcount;
490
491 void syscall_regfunc(void)
492 {
493 unsigned long flags;
494 struct task_struct *g, *t;
495
496 if (!sys_tracepoint_refcount) {
497 read_lock_irqsave(&tasklist_lock, flags);
498 do_each_thread(g, t) {
499 /* Skip kernel threads. */
500 if (t->mm)
501 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
502 } while_each_thread(g, t);
503 read_unlock_irqrestore(&tasklist_lock, flags);
504 }
505 sys_tracepoint_refcount++;
506 }
507
508 void syscall_unregfunc(void)
509 {
510 unsigned long flags;
511 struct task_struct *g, *t;
512
513 sys_tracepoint_refcount--;
514 if (!sys_tracepoint_refcount) {
515 read_lock_irqsave(&tasklist_lock, flags);
516 do_each_thread(g, t) {
517 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
518 } while_each_thread(g, t);
519 read_unlock_irqrestore(&tasklist_lock, flags);
520 }
521 }
522 #endif