projects/linux·blob v4.6 · refs

559 lines · 14.5 KiB

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
30extern struct tracepoint * const __start___tracepoints_ptrs[];
31extern struct tracepoint * const __stop___tracepoints_ptrs[];
32
33/* Set to 1 to enable tracepoint debug output */
34static const int tracepoint_debug;
35
36#ifdef CONFIG_MODULES
37/*
38 * Tracepoint module list mutex protects the local module list.
39 */
40static DEFINE_MUTEX(tracepoint_module_list_mutex);
41
42/* Local list of struct tp_module */
43static 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 */
50static 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 */
57struct tp_probes {
58 struct rcu_head rcu;
59 struct tracepoint_func probes[0];
60};
61
62static 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
69static void rcu_free_old_probes(struct rcu_head *head)
70{
71 kfree(container_of(head, struct tp_probes, rcu));
72}
73
74static 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
83static 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
94static struct tracepoint_func *
95func_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
142static 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 */
193static 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(1);
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 */
229static 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(1);
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 */
268int 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}
282EXPORT_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 */
297int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
298{
299 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
300}
301EXPORT_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 */
311int 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}
323EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
324
325#ifdef CONFIG_MODULES
326bool 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
332static 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 */
343int 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);
354end:
355 mutex_unlock(&tracepoint_module_list_mutex);
356 return ret;
357}
358EXPORT_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 */
367int 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);
378end:
379 mutex_unlock(&tracepoint_module_list_mutex);
380 return ret;
381
382}
383EXPORT_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 */
389static 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
400static 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);
425end:
426 mutex_unlock(&tracepoint_module_list_mutex);
427 return ret;
428}
429
430static 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
462static 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
483static struct notifier_block tracepoint_module_nb = {
484 .notifier_call = tracepoint_module_notify,
485 .priority = 0,
486};
487
488static __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
501static 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 */
519void 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}
525EXPORT_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 */
530static int sys_tracepoint_refcount;
531
532void 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
546void 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