projects/linux·blob v4.13 · refs

566 lines · 14.6 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/signal.h>
28#include <linux/sched/task.h>
29#include <linux/static_key.h>
30
31extern struct tracepoint * const __start___tracepoints_ptrs[];
32extern struct tracepoint * const __stop___tracepoints_ptrs[];
33
34/* Set to 1 to enable tracepoint debug output */
35static const int tracepoint_debug;
36
37#ifdef CONFIG_MODULES
38/*
39 * Tracepoint module list mutex protects the local module list.
40 */
41static DEFINE_MUTEX(tracepoint_module_list_mutex);
42
43/* Local list of struct tp_module */
44static LIST_HEAD(tracepoint_module_list);
45#endif /* CONFIG_MODULES */
46
47/*
48 * tracepoints_mutex protects the builtin and module tracepoints.
49 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
50 */
51static DEFINE_MUTEX(tracepoints_mutex);
52
53/*
54 * Note about RCU :
55 * It is used to delay the free of multiple probes array until a quiescent
56 * state is reached.
57 */
58struct tp_probes {
59 struct rcu_head rcu;
60 struct tracepoint_func probes[0];
61};
62
63static inline void *allocate_probes(int count)
64{
65 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
66 + sizeof(struct tp_probes), GFP_KERNEL);
67 return p == NULL ? NULL : p->probes;
68}
69
70static void rcu_free_old_probes(struct rcu_head *head)
71{
72 kfree(container_of(head, struct tp_probes, rcu));
73}
74
75static inline void release_probes(struct tracepoint_func *old)
76{
77 if (old) {
78 struct tp_probes *tp_probes = container_of(old,
79 struct tp_probes, probes[0]);
80 call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
81 }
82}
83
84static void debug_print_probes(struct tracepoint_func *funcs)
85{
86 int i;
87
88 if (!tracepoint_debug || !funcs)
89 return;
90
91 for (i = 0; funcs[i].func; i++)
92 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
93}
94
95static struct tracepoint_func *
96func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
97 int prio)
98{
99 struct tracepoint_func *old, *new;
100 int nr_probes = 0;
101 int pos = -1;
102
103 if (WARN_ON(!tp_func->func))
104 return ERR_PTR(-EINVAL);
105
106 debug_print_probes(*funcs);
107 old = *funcs;
108 if (old) {
109 /* (N -> N+1), (N != 0, 1) probes */
110 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
111 /* Insert before probes of lower priority */
112 if (pos < 0 && old[nr_probes].prio < prio)
113 pos = nr_probes;
114 if (old[nr_probes].func == tp_func->func &&
115 old[nr_probes].data == tp_func->data)
116 return ERR_PTR(-EEXIST);
117 }
118 }
119 /* + 2 : one for new probe, one for NULL func */
120 new = allocate_probes(nr_probes + 2);
121 if (new == NULL)
122 return ERR_PTR(-ENOMEM);
123 if (old) {
124 if (pos < 0) {
125 pos = nr_probes;
126 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
127 } else {
128 /* Copy higher priority probes ahead of the new probe */
129 memcpy(new, old, pos * sizeof(struct tracepoint_func));
130 /* Copy the rest after it. */
131 memcpy(new + pos + 1, old + pos,
132 (nr_probes - pos) * sizeof(struct tracepoint_func));
133 }
134 } else
135 pos = 0;
136 new[pos] = *tp_func;
137 new[nr_probes + 1].func = NULL;
138 *funcs = new;
139 debug_print_probes(*funcs);
140 return old;
141}
142
143static void *func_remove(struct tracepoint_func **funcs,
144 struct tracepoint_func *tp_func)
145{
146 int nr_probes = 0, nr_del = 0, i;
147 struct tracepoint_func *old, *new;
148
149 old = *funcs;
150
151 if (!old)
152 return ERR_PTR(-ENOENT);
153
154 debug_print_probes(*funcs);
155 /* (N -> M), (N > 1, M >= 0) probes */
156 if (tp_func->func) {
157 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
158 if (old[nr_probes].func == tp_func->func &&
159 old[nr_probes].data == tp_func->data)
160 nr_del++;
161 }
162 }
163
164 /*
165 * If probe is NULL, then nr_probes = nr_del = 0, and then the
166 * entire entry will be removed.
167 */
168 if (nr_probes - nr_del == 0) {
169 /* N -> 0, (N > 1) */
170 *funcs = NULL;
171 debug_print_probes(*funcs);
172 return old;
173 } else {
174 int j = 0;
175 /* N -> M, (N > 1, M > 0) */
176 /* + 1 for NULL */
177 new = allocate_probes(nr_probes - nr_del + 1);
178 if (new == NULL)
179 return ERR_PTR(-ENOMEM);
180 for (i = 0; old[i].func; i++)
181 if (old[i].func != tp_func->func
182 || old[i].data != tp_func->data)
183 new[j++] = old[i];
184 new[nr_probes - nr_del].func = NULL;
185 *funcs = new;
186 }
187 debug_print_probes(*funcs);
188 return old;
189}
190
191/*
192 * Add the probe function to a tracepoint.
193 */
194static int tracepoint_add_func(struct tracepoint *tp,
195 struct tracepoint_func *func, int prio)
196{
197 struct tracepoint_func *old, *tp_funcs;
198 int ret;
199
200 if (tp->regfunc && !static_key_enabled(&tp->key)) {
201 ret = tp->regfunc();
202 if (ret < 0)
203 return ret;
204 }
205
206 tp_funcs = rcu_dereference_protected(tp->funcs,
207 lockdep_is_held(&tracepoints_mutex));
208 old = func_add(&tp_funcs, func, prio);
209 if (IS_ERR(old)) {
210 WARN_ON_ONCE(1);
211 return PTR_ERR(old);
212 }
213
214 /*
215 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
216 * probe callbacks array is consistent before setting a pointer to it.
217 * This array is referenced by __DO_TRACE from
218 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
219 * is used.
220 */
221 rcu_assign_pointer(tp->funcs, tp_funcs);
222 if (!static_key_enabled(&tp->key))
223 static_key_slow_inc(&tp->key);
224 release_probes(old);
225 return 0;
226}
227
228/*
229 * Remove a probe function from a tracepoint.
230 * Note: only waiting an RCU period after setting elem->call to the empty
231 * function insures that the original callback is not used anymore. This insured
232 * by preempt_disable around the call site.
233 */
234static int tracepoint_remove_func(struct tracepoint *tp,
235 struct tracepoint_func *func)
236{
237 struct tracepoint_func *old, *tp_funcs;
238
239 tp_funcs = rcu_dereference_protected(tp->funcs,
240 lockdep_is_held(&tracepoints_mutex));
241 old = func_remove(&tp_funcs, func);
242 if (IS_ERR(old)) {
243 WARN_ON_ONCE(1);
244 return PTR_ERR(old);
245 }
246
247 if (!tp_funcs) {
248 /* Removed last function */
249 if (tp->unregfunc && static_key_enabled(&tp->key))
250 tp->unregfunc();
251
252 if (static_key_enabled(&tp->key))
253 static_key_slow_dec(&tp->key);
254 }
255 rcu_assign_pointer(tp->funcs, tp_funcs);
256 release_probes(old);
257 return 0;
258}
259
260/**
261 * tracepoint_probe_register - Connect a probe to a tracepoint
262 * @tp: tracepoint
263 * @probe: probe handler
264 * @data: tracepoint data
265 * @prio: priority of this function over other registered functions
266 *
267 * Returns 0 if ok, error value on error.
268 * Note: if @tp is within a module, the caller is responsible for
269 * unregistering the probe before the module is gone. This can be
270 * performed either with a tracepoint module going notifier, or from
271 * within module exit functions.
272 */
273int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
274 void *data, int prio)
275{
276 struct tracepoint_func tp_func;
277 int ret;
278
279 mutex_lock(&tracepoints_mutex);
280 tp_func.func = probe;
281 tp_func.data = data;
282 tp_func.prio = prio;
283 ret = tracepoint_add_func(tp, &tp_func, prio);
284 mutex_unlock(&tracepoints_mutex);
285 return ret;
286}
287EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
288
289/**
290 * tracepoint_probe_register - Connect a probe to a tracepoint
291 * @tp: tracepoint
292 * @probe: probe handler
293 * @data: tracepoint data
294 * @prio: priority of this function over other registered functions
295 *
296 * Returns 0 if ok, error value on error.
297 * Note: if @tp is within a module, the caller is responsible for
298 * unregistering the probe before the module is gone. This can be
299 * performed either with a tracepoint module going notifier, or from
300 * within module exit functions.
301 */
302int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
303{
304 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
305}
306EXPORT_SYMBOL_GPL(tracepoint_probe_register);
307
308/**
309 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
310 * @tp: tracepoint
311 * @probe: probe function pointer
312 * @data: tracepoint data
313 *
314 * Returns 0 if ok, error value on error.
315 */
316int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
317{
318 struct tracepoint_func tp_func;
319 int ret;
320
321 mutex_lock(&tracepoints_mutex);
322 tp_func.func = probe;
323 tp_func.data = data;
324 ret = tracepoint_remove_func(tp, &tp_func);
325 mutex_unlock(&tracepoints_mutex);
326 return ret;
327}
328EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
329
330#ifdef CONFIG_MODULES
331bool trace_module_has_bad_taint(struct module *mod)
332{
333 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
334 (1 << TAINT_UNSIGNED_MODULE));
335}
336
337static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
338
339/**
340 * register_tracepoint_notifier - register tracepoint coming/going notifier
341 * @nb: notifier block
342 *
343 * Notifiers registered with this function are called on module
344 * coming/going with the tracepoint_module_list_mutex held.
345 * The notifier block callback should expect a "struct tp_module" data
346 * pointer.
347 */
348int register_tracepoint_module_notifier(struct notifier_block *nb)
349{
350 struct tp_module *tp_mod;
351 int ret;
352
353 mutex_lock(&tracepoint_module_list_mutex);
354 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
355 if (ret)
356 goto end;
357 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
358 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
359end:
360 mutex_unlock(&tracepoint_module_list_mutex);
361 return ret;
362}
363EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
364
365/**
366 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
367 * @nb: notifier block
368 *
369 * The notifier block callback should expect a "struct tp_module" data
370 * pointer.
371 */
372int unregister_tracepoint_module_notifier(struct notifier_block *nb)
373{
374 struct tp_module *tp_mod;
375 int ret;
376
377 mutex_lock(&tracepoint_module_list_mutex);
378 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
379 if (ret)
380 goto end;
381 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
382 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
383end:
384 mutex_unlock(&tracepoint_module_list_mutex);
385 return ret;
386
387}
388EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
389
390/*
391 * Ensure the tracer unregistered the module's probes before the module
392 * teardown is performed. Prevents leaks of probe and data pointers.
393 */
394static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
395 struct tracepoint * const *end)
396{
397 struct tracepoint * const *iter;
398
399 if (!begin)
400 return;
401 for (iter = begin; iter < end; iter++)
402 WARN_ON_ONCE((*iter)->funcs);
403}
404
405static int tracepoint_module_coming(struct module *mod)
406{
407 struct tp_module *tp_mod;
408 int ret = 0;
409
410 if (!mod->num_tracepoints)
411 return 0;
412
413 /*
414 * We skip modules that taint the kernel, especially those with different
415 * module headers (for forced load), to make sure we don't cause a crash.
416 * Staging, out-of-tree, and unsigned GPL modules are fine.
417 */
418 if (trace_module_has_bad_taint(mod))
419 return 0;
420 mutex_lock(&tracepoint_module_list_mutex);
421 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
422 if (!tp_mod) {
423 ret = -ENOMEM;
424 goto end;
425 }
426 tp_mod->mod = mod;
427 list_add_tail(&tp_mod->list, &tracepoint_module_list);
428 blocking_notifier_call_chain(&tracepoint_notify_list,
429 MODULE_STATE_COMING, tp_mod);
430end:
431 mutex_unlock(&tracepoint_module_list_mutex);
432 return ret;
433}
434
435static void tracepoint_module_going(struct module *mod)
436{
437 struct tp_module *tp_mod;
438
439 if (!mod->num_tracepoints)
440 return;
441
442 mutex_lock(&tracepoint_module_list_mutex);
443 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
444 if (tp_mod->mod == mod) {
445 blocking_notifier_call_chain(&tracepoint_notify_list,
446 MODULE_STATE_GOING, tp_mod);
447 list_del(&tp_mod->list);
448 kfree(tp_mod);
449 /*
450 * Called the going notifier before checking for
451 * quiescence.
452 */
453 tp_module_going_check_quiescent(mod->tracepoints_ptrs,
454 mod->tracepoints_ptrs + mod->num_tracepoints);
455 break;
456 }
457 }
458 /*
459 * In the case of modules that were tainted at "coming", we'll simply
460 * walk through the list without finding it. We cannot use the "tainted"
461 * flag on "going", in case a module taints the kernel only after being
462 * loaded.
463 */
464 mutex_unlock(&tracepoint_module_list_mutex);
465}
466
467static int tracepoint_module_notify(struct notifier_block *self,
468 unsigned long val, void *data)
469{
470 struct module *mod = data;
471 int ret = 0;
472
473 switch (val) {
474 case MODULE_STATE_COMING:
475 ret = tracepoint_module_coming(mod);
476 break;
477 case MODULE_STATE_LIVE:
478 break;
479 case MODULE_STATE_GOING:
480 tracepoint_module_going(mod);
481 break;
482 case MODULE_STATE_UNFORMED:
483 break;
484 }
485 return ret;
486}
487
488static struct notifier_block tracepoint_module_nb = {
489 .notifier_call = tracepoint_module_notify,
490 .priority = 0,
491};
492
493static __init int init_tracepoints(void)
494{
495 int ret;
496
497 ret = register_module_notifier(&tracepoint_module_nb);
498 if (ret)
499 pr_warn("Failed to register tracepoint module enter notifier\n");
500
501 return ret;
502}
503__initcall(init_tracepoints);
504#endif /* CONFIG_MODULES */
505
506static void for_each_tracepoint_range(struct tracepoint * const *begin,
507 struct tracepoint * const *end,
508 void (*fct)(struct tracepoint *tp, void *priv),
509 void *priv)
510{
511 struct tracepoint * const *iter;
512
513 if (!begin)
514 return;
515 for (iter = begin; iter < end; iter++)
516 fct(*iter, priv);
517}
518
519/**
520 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
521 * @fct: callback
522 * @priv: private data
523 */
524void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
525 void *priv)
526{
527 for_each_tracepoint_range(__start___tracepoints_ptrs,
528 __stop___tracepoints_ptrs, fct, priv);
529}
530EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
531
532#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
533
534/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
535static int sys_tracepoint_refcount;
536
537int syscall_regfunc(void)
538{
539 struct task_struct *p, *t;
540
541 if (!sys_tracepoint_refcount) {
542 read_lock(&tasklist_lock);
543 for_each_process_thread(p, t) {
544 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
545 }
546 read_unlock(&tasklist_lock);
547 }
548 sys_tracepoint_refcount++;
549
550 return 0;
551}
552
553void syscall_unregfunc(void)
554{
555 struct task_struct *p, *t;
556
557 sys_tracepoint_refcount--;
558 if (!sys_tracepoint_refcount) {
559 read_lock(&tasklist_lock);
560 for_each_process_thread(p, t) {
561 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
562 }
563 read_unlock(&tasklist_lock);
564 }
565}
566#endif