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97e1c18e 1/*
de7b2973 2 * Copyright (C) 2008-2014 Mathieu Desnoyers
97e1c18e
MD
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>
3f07c014 27#include <linux/sched/signal.h>
29930025 28#include <linux/sched/task.h>
c5905afb 29#include <linux/static_key.h>
97e1c18e 30
65498646
MD
31extern struct tracepoint * const __start___tracepoints_ptrs[];
32extern struct tracepoint * const __stop___tracepoints_ptrs[];
97e1c18e
MD
33
34/* Set to 1 to enable tracepoint debug output */
35static const int tracepoint_debug;
36
de7b2973 37#ifdef CONFIG_MODULES
97e1c18e 38/*
de7b2973 39 * Tracepoint module list mutex protects the local module list.
97e1c18e 40 */
de7b2973 41static DEFINE_MUTEX(tracepoint_module_list_mutex);
97e1c18e 42
de7b2973 43/* Local list of struct tp_module */
b75ef8b4
MD
44static LIST_HEAD(tracepoint_module_list);
45#endif /* CONFIG_MODULES */
46
97e1c18e 47/*
de7b2973
MD
48 * tracepoints_mutex protects the builtin and module tracepoints.
49 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
97e1c18e 50 */
de7b2973 51static DEFINE_MUTEX(tracepoints_mutex);
97e1c18e
MD
52
53/*
54 * Note about RCU :
fd589a8f 55 * It is used to delay the free of multiple probes array until a quiescent
97e1c18e 56 * state is reached.
97e1c18e 57 */
19dba33c 58struct tp_probes {
0dea6d52 59 struct rcu_head rcu;
38516ab5 60 struct tracepoint_func probes[0];
19dba33c 61};
97e1c18e 62
19dba33c 63static inline void *allocate_probes(int count)
97e1c18e 64{
38516ab5 65 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
19dba33c
LJ
66 + sizeof(struct tp_probes), GFP_KERNEL);
67 return p == NULL ? NULL : p->probes;
97e1c18e
MD
68}
69
19dba33c 70static void rcu_free_old_probes(struct rcu_head *head)
97e1c18e 71{
0dea6d52 72 kfree(container_of(head, struct tp_probes, rcu));
19dba33c
LJ
73}
74
38516ab5 75static inline void release_probes(struct tracepoint_func *old)
19dba33c
LJ
76{
77 if (old) {
78 struct tp_probes *tp_probes = container_of(old,
79 struct tp_probes, probes[0]);
0dea6d52 80 call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
19dba33c 81 }
97e1c18e
MD
82}
83
de7b2973 84static void debug_print_probes(struct tracepoint_func *funcs)
97e1c18e
MD
85{
86 int i;
87
de7b2973 88 if (!tracepoint_debug || !funcs)
97e1c18e
MD
89 return;
90
de7b2973
MD
91 for (i = 0; funcs[i].func; i++)
92 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
97e1c18e
MD
93}
94
7904b5c4
SRRH
95static struct tracepoint_func *
96func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
97 int prio)
97e1c18e 98{
38516ab5 99 struct tracepoint_func *old, *new;
7904b5c4
SRRH
100 int nr_probes = 0;
101 int pos = -1;
97e1c18e 102
de7b2973 103 if (WARN_ON(!tp_func->func))
4c69e6ea 104 return ERR_PTR(-EINVAL);
97e1c18e 105
de7b2973
MD
106 debug_print_probes(*funcs);
107 old = *funcs;
97e1c18e
MD
108 if (old) {
109 /* (N -> N+1), (N != 0, 1) probes */
7904b5c4
SRRH
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;
de7b2973
MD
114 if (old[nr_probes].func == tp_func->func &&
115 old[nr_probes].data == tp_func->data)
97e1c18e 116 return ERR_PTR(-EEXIST);
7904b5c4 117 }
97e1c18e
MD
118 }
119 /* + 2 : one for new probe, one for NULL func */
19dba33c 120 new = allocate_probes(nr_probes + 2);
97e1c18e
MD
121 if (new == NULL)
122 return ERR_PTR(-ENOMEM);
7904b5c4
SRRH
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;
38516ab5 137 new[nr_probes + 1].func = NULL;
de7b2973
MD
138 *funcs = new;
139 debug_print_probes(*funcs);
97e1c18e
MD
140 return old;
141}
142
de7b2973
MD
143static void *func_remove(struct tracepoint_func **funcs,
144 struct tracepoint_func *tp_func)
97e1c18e
MD
145{
146 int nr_probes = 0, nr_del = 0, i;
38516ab5 147 struct tracepoint_func *old, *new;
97e1c18e 148
de7b2973 149 old = *funcs;
97e1c18e 150
f66af459 151 if (!old)
19dba33c 152 return ERR_PTR(-ENOENT);
f66af459 153
de7b2973 154 debug_print_probes(*funcs);
97e1c18e 155 /* (N -> M), (N > 1, M >= 0) probes */
de7b2973 156 if (tp_func->func) {
4c69e6ea 157 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
de7b2973
MD
158 if (old[nr_probes].func == tp_func->func &&
159 old[nr_probes].data == tp_func->data)
4c69e6ea
S
160 nr_del++;
161 }
97e1c18e
MD
162 }
163
4c69e6ea
S
164 /*
165 * If probe is NULL, then nr_probes = nr_del = 0, and then the
166 * entire entry will be removed.
167 */
97e1c18e
MD
168 if (nr_probes - nr_del == 0) {
169 /* N -> 0, (N > 1) */
de7b2973
MD
170 *funcs = NULL;
171 debug_print_probes(*funcs);
97e1c18e
MD
172 return old;
173 } else {
174 int j = 0;
175 /* N -> M, (N > 1, M > 0) */
176 /* + 1 for NULL */
19dba33c 177 new = allocate_probes(nr_probes - nr_del + 1);
97e1c18e
MD
178 if (new == NULL)
179 return ERR_PTR(-ENOMEM);
38516ab5 180 for (i = 0; old[i].func; i++)
de7b2973
MD
181 if (old[i].func != tp_func->func
182 || old[i].data != tp_func->data)
97e1c18e 183 new[j++] = old[i];
38516ab5 184 new[nr_probes - nr_del].func = NULL;
de7b2973 185 *funcs = new;
97e1c18e 186 }
de7b2973 187 debug_print_probes(*funcs);
97e1c18e
MD
188 return old;
189}
190
191/*
de7b2973 192 * Add the probe function to a tracepoint.
97e1c18e 193 */
de7b2973 194static int tracepoint_add_func(struct tracepoint *tp,
7904b5c4 195 struct tracepoint_func *func, int prio)
97e1c18e 196{
de7b2973 197 struct tracepoint_func *old, *tp_funcs;
8cf868af 198 int ret;
97e1c18e 199
8cf868af
SRRH
200 if (tp->regfunc && !static_key_enabled(&tp->key)) {
201 ret = tp->regfunc();
202 if (ret < 0)
203 return ret;
204 }
97e1c18e 205
b725dfea
MD
206 tp_funcs = rcu_dereference_protected(tp->funcs,
207 lockdep_is_held(&tracepoints_mutex));
7904b5c4 208 old = func_add(&tp_funcs, func, prio);
de7b2973
MD
209 if (IS_ERR(old)) {
210 WARN_ON_ONCE(1);
211 return PTR_ERR(old);
212 }
97419875 213
97e1c18e
MD
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 */
de7b2973
MD
221 rcu_assign_pointer(tp->funcs, tp_funcs);
222 if (!static_key_enabled(&tp->key))
223 static_key_slow_inc(&tp->key);
8058bd0f 224 release_probes(old);
de7b2973 225 return 0;
97e1c18e
MD
226}
227
228/*
de7b2973 229 * Remove a probe function from a tracepoint.
97e1c18e
MD
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 */
de7b2973
MD
234static int tracepoint_remove_func(struct tracepoint *tp,
235 struct tracepoint_func *func)
97e1c18e 236{
de7b2973 237 struct tracepoint_func *old, *tp_funcs;
97e1c18e 238
b725dfea
MD
239 tp_funcs = rcu_dereference_protected(tp->funcs,
240 lockdep_is_held(&tracepoints_mutex));
de7b2973
MD
241 old = func_remove(&tp_funcs, func);
242 if (IS_ERR(old)) {
243 WARN_ON_ONCE(1);
244 return PTR_ERR(old);
97e1c18e 245 }
b75ef8b4 246
de7b2973
MD
247 if (!tp_funcs) {
248 /* Removed last function */
249 if (tp->unregfunc && static_key_enabled(&tp->key))
250 tp->unregfunc();
b75ef8b4 251
de7b2973
MD
252 if (static_key_enabled(&tp->key))
253 static_key_slow_dec(&tp->key);
127cafbb 254 }
de7b2973 255 rcu_assign_pointer(tp->funcs, tp_funcs);
8058bd0f 256 release_probes(old);
de7b2973 257 return 0;
127cafbb
LJ
258}
259
97e1c18e
MD
260/**
261 * tracepoint_probe_register - Connect a probe to a tracepoint
de7b2973 262 * @tp: tracepoint
97e1c18e 263 * @probe: probe handler
cac92ba7 264 * @data: tracepoint data
7904b5c4 265 * @prio: priority of this function over other registered functions
97e1c18e 266 *
de7b2973
MD
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.
97e1c18e 272 */
7904b5c4
SRRH
273int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
274 void *data, int prio)
97e1c18e 275{
de7b2973
MD
276 struct tracepoint_func tp_func;
277 int ret;
97e1c18e
MD
278
279 mutex_lock(&tracepoints_mutex);
de7b2973
MD
280 tp_func.func = probe;
281 tp_func.data = data;
7904b5c4
SRRH
282 tp_func.prio = prio;
283 ret = tracepoint_add_func(tp, &tp_func, prio);
b75ef8b4 284 mutex_unlock(&tracepoints_mutex);
b196e2b9 285 return ret;
97e1c18e 286}
7904b5c4
SRRH
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}
97e1c18e
MD
306EXPORT_SYMBOL_GPL(tracepoint_probe_register);
307
308/**
309 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
de7b2973 310 * @tp: tracepoint
97e1c18e 311 * @probe: probe function pointer
cac92ba7 312 * @data: tracepoint data
97e1c18e 313 *
de7b2973 314 * Returns 0 if ok, error value on error.
97e1c18e 315 */
de7b2973 316int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
97e1c18e 317{
de7b2973
MD
318 struct tracepoint_func tp_func;
319 int ret;
97e1c18e
MD
320
321 mutex_lock(&tracepoints_mutex);
de7b2973
MD
322 tp_func.func = probe;
323 tp_func.data = data;
324 ret = tracepoint_remove_func(tp, &tp_func);
b75ef8b4 325 mutex_unlock(&tracepoints_mutex);
de7b2973 326 return ret;
97e1c18e
MD
327}
328EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
329
227a8375 330#ifdef CONFIG_MODULES
45ab2813
SRRH
331bool trace_module_has_bad_taint(struct module *mod)
332{
66cc69e3
MD
333 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
334 (1 << TAINT_UNSIGNED_MODULE));
45ab2813
SRRH
335}
336
de7b2973
MD
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
b75ef8b4
MD
405static int tracepoint_module_coming(struct module *mod)
406{
0dea6d52 407 struct tp_module *tp_mod;
b75ef8b4
MD
408 int ret = 0;
409
7dec935a
SRRH
410 if (!mod->num_tracepoints)
411 return 0;
412
b75ef8b4 413 /*
c10076c4
SR
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.
66cc69e3 416 * Staging, out-of-tree, and unsigned GPL modules are fine.
b75ef8b4 417 */
45ab2813 418 if (trace_module_has_bad_taint(mod))
b75ef8b4 419 return 0;
de7b2973 420 mutex_lock(&tracepoint_module_list_mutex);
b75ef8b4
MD
421 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
422 if (!tp_mod) {
423 ret = -ENOMEM;
424 goto end;
425 }
eb7d035c 426 tp_mod->mod = mod;
0dea6d52 427 list_add_tail(&tp_mod->list, &tracepoint_module_list);
de7b2973
MD
428 blocking_notifier_call_chain(&tracepoint_notify_list,
429 MODULE_STATE_COMING, tp_mod);
b75ef8b4 430end:
de7b2973 431 mutex_unlock(&tracepoint_module_list_mutex);
b75ef8b4
MD
432 return ret;
433}
434
de7b2973 435static void tracepoint_module_going(struct module *mod)
b75ef8b4 436{
de7b2973 437 struct tp_module *tp_mod;
b75ef8b4 438
7dec935a 439 if (!mod->num_tracepoints)
de7b2973 440 return;
7dec935a 441
de7b2973
MD
442 mutex_lock(&tracepoint_module_list_mutex);
443 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
eb7d035c 444 if (tp_mod->mod == mod) {
de7b2973
MD
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);
b75ef8b4
MD
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 */
de7b2973 464 mutex_unlock(&tracepoint_module_list_mutex);
b75ef8b4 465}
227a8375 466
de7b2973
MD
467static int tracepoint_module_notify(struct notifier_block *self,
468 unsigned long val, void *data)
32f85742
MD
469{
470 struct module *mod = data;
b75ef8b4 471 int ret = 0;
32f85742
MD
472
473 switch (val) {
474 case MODULE_STATE_COMING:
b75ef8b4
MD
475 ret = tracepoint_module_coming(mod);
476 break;
477 case MODULE_STATE_LIVE:
478 break;
32f85742 479 case MODULE_STATE_GOING:
de7b2973
MD
480 tracepoint_module_going(mod);
481 break;
482 case MODULE_STATE_UNFORMED:
32f85742
MD
483 break;
484 }
b75ef8b4 485 return ret;
32f85742
MD
486}
487
de7b2973 488static struct notifier_block tracepoint_module_nb = {
32f85742
MD
489 .notifier_call = tracepoint_module_notify,
490 .priority = 0,
491};
492
de7b2973 493static __init int init_tracepoints(void)
32f85742 494{
de7b2973
MD
495 int ret;
496
497 ret = register_module_notifier(&tracepoint_module_nb);
eb7d035c 498 if (ret)
a395d6a7 499 pr_warn("Failed to register tracepoint module enter notifier\n");
eb7d035c 500
de7b2973 501 return ret;
32f85742
MD
502}
503__initcall(init_tracepoints);
227a8375 504#endif /* CONFIG_MODULES */
a871bd33 505
de7b2973
MD
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
3d27d8cb 532#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
60d970c2 533
97419875 534/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
a871bd33
JB
535static int sys_tracepoint_refcount;
536
8cf868af 537int syscall_regfunc(void)
a871bd33 538{
8063e41d 539 struct task_struct *p, *t;
a871bd33 540
a871bd33 541 if (!sys_tracepoint_refcount) {
8063e41d
ON
542 read_lock(&tasklist_lock);
543 for_each_process_thread(p, t) {
ea73c79e 544 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
8063e41d
ON
545 }
546 read_unlock(&tasklist_lock);
a871bd33
JB
547 }
548 sys_tracepoint_refcount++;
8cf868af
SRRH
549
550 return 0;
a871bd33
JB
551}
552
553void syscall_unregfunc(void)
554{
8063e41d 555 struct task_struct *p, *t;
a871bd33 556
a871bd33
JB
557 sys_tracepoint_refcount--;
558 if (!sys_tracepoint_refcount) {
8063e41d
ON
559 read_lock(&tasklist_lock);
560 for_each_process_thread(p, t) {
66700001 561 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
8063e41d
ON
562 }
563 read_unlock(&tasklist_lock);
a871bd33 564 }
a871bd33 565}
60d970c2 566#endif