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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>
a871bd33 27#include <linux/sched.h>
c5905afb 28#include <linux/static_key.h>
97e1c18e 29
65498646
MD
30extern struct tracepoint * const __start___tracepoints_ptrs[];
31extern struct tracepoint * const __stop___tracepoints_ptrs[];
97e1c18e
MD
32
33/* Set to 1 to enable tracepoint debug output */
34static const int tracepoint_debug;
35
de7b2973 36#ifdef CONFIG_MODULES
97e1c18e 37/*
de7b2973 38 * Tracepoint module list mutex protects the local module list.
97e1c18e 39 */
de7b2973 40static DEFINE_MUTEX(tracepoint_module_list_mutex);
97e1c18e 41
de7b2973 42/* Local list of struct tp_module */
b75ef8b4
MD
43static LIST_HEAD(tracepoint_module_list);
44#endif /* CONFIG_MODULES */
45
97e1c18e 46/*
de7b2973
MD
47 * tracepoints_mutex protects the builtin and module tracepoints.
48 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
97e1c18e 49 */
de7b2973 50static DEFINE_MUTEX(tracepoints_mutex);
97e1c18e
MD
51
52/*
53 * Note about RCU :
fd589a8f 54 * It is used to delay the free of multiple probes array until a quiescent
97e1c18e 55 * state is reached.
97e1c18e 56 */
19dba33c 57struct tp_probes {
0dea6d52 58 struct rcu_head rcu;
38516ab5 59 struct tracepoint_func probes[0];
19dba33c 60};
97e1c18e 61
19dba33c 62static inline void *allocate_probes(int count)
97e1c18e 63{
38516ab5 64 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
19dba33c
LJ
65 + sizeof(struct tp_probes), GFP_KERNEL);
66 return p == NULL ? NULL : p->probes;
97e1c18e
MD
67}
68
19dba33c 69static void rcu_free_old_probes(struct rcu_head *head)
97e1c18e 70{
0dea6d52 71 kfree(container_of(head, struct tp_probes, rcu));
19dba33c
LJ
72}
73
38516ab5 74static inline void release_probes(struct tracepoint_func *old)
19dba33c
LJ
75{
76 if (old) {
77 struct tp_probes *tp_probes = container_of(old,
78 struct tp_probes, probes[0]);
0dea6d52 79 call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
19dba33c 80 }
97e1c18e
MD
81}
82
de7b2973 83static void debug_print_probes(struct tracepoint_func *funcs)
97e1c18e
MD
84{
85 int i;
86
de7b2973 87 if (!tracepoint_debug || !funcs)
97e1c18e
MD
88 return;
89
de7b2973
MD
90 for (i = 0; funcs[i].func; i++)
91 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
97e1c18e
MD
92}
93
de7b2973
MD
94static struct tracepoint_func *func_add(struct tracepoint_func **funcs,
95 struct tracepoint_func *tp_func)
97e1c18e
MD
96{
97 int nr_probes = 0;
38516ab5 98 struct tracepoint_func *old, *new;
97e1c18e 99
de7b2973 100 if (WARN_ON(!tp_func->func))
4c69e6ea 101 return ERR_PTR(-EINVAL);
97e1c18e 102
de7b2973
MD
103 debug_print_probes(*funcs);
104 old = *funcs;
97e1c18e
MD
105 if (old) {
106 /* (N -> N+1), (N != 0, 1) probes */
38516ab5 107 for (nr_probes = 0; old[nr_probes].func; nr_probes++)
de7b2973
MD
108 if (old[nr_probes].func == tp_func->func &&
109 old[nr_probes].data == tp_func->data)
97e1c18e
MD
110 return ERR_PTR(-EEXIST);
111 }
112 /* + 2 : one for new probe, one for NULL func */
19dba33c 113 new = allocate_probes(nr_probes + 2);
97e1c18e
MD
114 if (new == NULL)
115 return ERR_PTR(-ENOMEM);
116 if (old)
38516ab5 117 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
de7b2973 118 new[nr_probes] = *tp_func;
38516ab5 119 new[nr_probes + 1].func = NULL;
de7b2973
MD
120 *funcs = new;
121 debug_print_probes(*funcs);
97e1c18e
MD
122 return old;
123}
124
de7b2973
MD
125static void *func_remove(struct tracepoint_func **funcs,
126 struct tracepoint_func *tp_func)
97e1c18e
MD
127{
128 int nr_probes = 0, nr_del = 0, i;
38516ab5 129 struct tracepoint_func *old, *new;
97e1c18e 130
de7b2973 131 old = *funcs;
97e1c18e 132
f66af459 133 if (!old)
19dba33c 134 return ERR_PTR(-ENOENT);
f66af459 135
de7b2973 136 debug_print_probes(*funcs);
97e1c18e 137 /* (N -> M), (N > 1, M >= 0) probes */
de7b2973 138 if (tp_func->func) {
4c69e6ea 139 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
de7b2973
MD
140 if (old[nr_probes].func == tp_func->func &&
141 old[nr_probes].data == tp_func->data)
4c69e6ea
S
142 nr_del++;
143 }
97e1c18e
MD
144 }
145
4c69e6ea
S
146 /*
147 * If probe is NULL, then nr_probes = nr_del = 0, and then the
148 * entire entry will be removed.
149 */
97e1c18e
MD
150 if (nr_probes - nr_del == 0) {
151 /* N -> 0, (N > 1) */
de7b2973
MD
152 *funcs = NULL;
153 debug_print_probes(*funcs);
97e1c18e
MD
154 return old;
155 } else {
156 int j = 0;
157 /* N -> M, (N > 1, M > 0) */
158 /* + 1 for NULL */
19dba33c 159 new = allocate_probes(nr_probes - nr_del + 1);
97e1c18e
MD
160 if (new == NULL)
161 return ERR_PTR(-ENOMEM);
38516ab5 162 for (i = 0; old[i].func; i++)
de7b2973
MD
163 if (old[i].func != tp_func->func
164 || old[i].data != tp_func->data)
97e1c18e 165 new[j++] = old[i];
38516ab5 166 new[nr_probes - nr_del].func = NULL;
de7b2973 167 *funcs = new;
97e1c18e 168 }
de7b2973 169 debug_print_probes(*funcs);
97e1c18e
MD
170 return old;
171}
172
173/*
de7b2973 174 * Add the probe function to a tracepoint.
97e1c18e 175 */
de7b2973
MD
176static int tracepoint_add_func(struct tracepoint *tp,
177 struct tracepoint_func *func)
97e1c18e 178{
de7b2973 179 struct tracepoint_func *old, *tp_funcs;
97e1c18e 180
de7b2973
MD
181 if (tp->regfunc && !static_key_enabled(&tp->key))
182 tp->regfunc();
97e1c18e 183
b725dfea
MD
184 tp_funcs = rcu_dereference_protected(tp->funcs,
185 lockdep_is_held(&tracepoints_mutex));
de7b2973
MD
186 old = func_add(&tp_funcs, func);
187 if (IS_ERR(old)) {
188 WARN_ON_ONCE(1);
189 return PTR_ERR(old);
190 }
97419875 191
97e1c18e
MD
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 */
de7b2973
MD
199 rcu_assign_pointer(tp->funcs, tp_funcs);
200 if (!static_key_enabled(&tp->key))
201 static_key_slow_inc(&tp->key);
8058bd0f 202 release_probes(old);
de7b2973 203 return 0;
97e1c18e
MD
204}
205
206/*
de7b2973 207 * Remove a probe function from a tracepoint.
97e1c18e
MD
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 */
de7b2973
MD
212static int tracepoint_remove_func(struct tracepoint *tp,
213 struct tracepoint_func *func)
97e1c18e 214{
de7b2973 215 struct tracepoint_func *old, *tp_funcs;
97e1c18e 216
b725dfea
MD
217 tp_funcs = rcu_dereference_protected(tp->funcs,
218 lockdep_is_held(&tracepoints_mutex));
de7b2973
MD
219 old = func_remove(&tp_funcs, func);
220 if (IS_ERR(old)) {
221 WARN_ON_ONCE(1);
222 return PTR_ERR(old);
97e1c18e 223 }
b75ef8b4 224
de7b2973
MD
225 if (!tp_funcs) {
226 /* Removed last function */
227 if (tp->unregfunc && static_key_enabled(&tp->key))
228 tp->unregfunc();
b75ef8b4 229
de7b2973
MD
230 if (static_key_enabled(&tp->key))
231 static_key_slow_dec(&tp->key);
127cafbb 232 }
de7b2973 233 rcu_assign_pointer(tp->funcs, tp_funcs);
8058bd0f 234 release_probes(old);
de7b2973 235 return 0;
127cafbb
LJ
236}
237
97e1c18e
MD
238/**
239 * tracepoint_probe_register - Connect a probe to a tracepoint
de7b2973 240 * @tp: tracepoint
97e1c18e 241 * @probe: probe handler
cac92ba7 242 * @data: tracepoint data
97e1c18e 243 *
de7b2973
MD
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.
97e1c18e 249 */
de7b2973 250int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
97e1c18e 251{
de7b2973
MD
252 struct tracepoint_func tp_func;
253 int ret;
97e1c18e
MD
254
255 mutex_lock(&tracepoints_mutex);
de7b2973
MD
256 tp_func.func = probe;
257 tp_func.data = data;
258 ret = tracepoint_add_func(tp, &tp_func);
b75ef8b4 259 mutex_unlock(&tracepoints_mutex);
b196e2b9 260 return ret;
97e1c18e
MD
261}
262EXPORT_SYMBOL_GPL(tracepoint_probe_register);
263
264/**
265 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
de7b2973 266 * @tp: tracepoint
97e1c18e 267 * @probe: probe function pointer
cac92ba7 268 * @data: tracepoint data
97e1c18e 269 *
de7b2973 270 * Returns 0 if ok, error value on error.
97e1c18e 271 */
de7b2973 272int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
97e1c18e 273{
de7b2973
MD
274 struct tracepoint_func tp_func;
275 int ret;
97e1c18e
MD
276
277 mutex_lock(&tracepoints_mutex);
de7b2973
MD
278 tp_func.func = probe;
279 tp_func.data = data;
280 ret = tracepoint_remove_func(tp, &tp_func);
b75ef8b4 281 mutex_unlock(&tracepoints_mutex);
de7b2973 282 return ret;
97e1c18e
MD
283}
284EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
285
227a8375 286#ifdef CONFIG_MODULES
45ab2813
SRRH
287bool trace_module_has_bad_taint(struct module *mod)
288{
66cc69e3
MD
289 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
290 (1 << TAINT_UNSIGNED_MODULE));
45ab2813
SRRH
291}
292
de7b2973
MD
293static 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 */
304int 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);
315end:
316 mutex_unlock(&tracepoint_module_list_mutex);
317 return ret;
318}
319EXPORT_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 */
328int 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);
339end:
340 mutex_unlock(&tracepoint_module_list_mutex);
341 return ret;
342
343}
344EXPORT_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 */
350static 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
b75ef8b4
MD
361static int tracepoint_module_coming(struct module *mod)
362{
0dea6d52 363 struct tp_module *tp_mod;
b75ef8b4
MD
364 int ret = 0;
365
7dec935a
SRRH
366 if (!mod->num_tracepoints)
367 return 0;
368
b75ef8b4 369 /*
c10076c4
SR
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.
66cc69e3 372 * Staging, out-of-tree, and unsigned GPL modules are fine.
b75ef8b4 373 */
45ab2813 374 if (trace_module_has_bad_taint(mod))
b75ef8b4 375 return 0;
de7b2973 376 mutex_lock(&tracepoint_module_list_mutex);
b75ef8b4
MD
377 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
378 if (!tp_mod) {
379 ret = -ENOMEM;
380 goto end;
381 }
eb7d035c 382 tp_mod->mod = mod;
0dea6d52 383 list_add_tail(&tp_mod->list, &tracepoint_module_list);
de7b2973
MD
384 blocking_notifier_call_chain(&tracepoint_notify_list,
385 MODULE_STATE_COMING, tp_mod);
b75ef8b4 386end:
de7b2973 387 mutex_unlock(&tracepoint_module_list_mutex);
b75ef8b4
MD
388 return ret;
389}
390
de7b2973 391static void tracepoint_module_going(struct module *mod)
b75ef8b4 392{
de7b2973 393 struct tp_module *tp_mod;
b75ef8b4 394
7dec935a 395 if (!mod->num_tracepoints)
de7b2973 396 return;
7dec935a 397
de7b2973
MD
398 mutex_lock(&tracepoint_module_list_mutex);
399 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
eb7d035c 400 if (tp_mod->mod == mod) {
de7b2973
MD
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);
b75ef8b4
MD
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 */
de7b2973 420 mutex_unlock(&tracepoint_module_list_mutex);
b75ef8b4 421}
227a8375 422
de7b2973
MD
423static int tracepoint_module_notify(struct notifier_block *self,
424 unsigned long val, void *data)
32f85742
MD
425{
426 struct module *mod = data;
b75ef8b4 427 int ret = 0;
32f85742
MD
428
429 switch (val) {
430 case MODULE_STATE_COMING:
b75ef8b4
MD
431 ret = tracepoint_module_coming(mod);
432 break;
433 case MODULE_STATE_LIVE:
434 break;
32f85742 435 case MODULE_STATE_GOING:
de7b2973
MD
436 tracepoint_module_going(mod);
437 break;
438 case MODULE_STATE_UNFORMED:
32f85742
MD
439 break;
440 }
b75ef8b4 441 return ret;
32f85742
MD
442}
443
de7b2973 444static struct notifier_block tracepoint_module_nb = {
32f85742
MD
445 .notifier_call = tracepoint_module_notify,
446 .priority = 0,
447};
448
de7b2973 449static __init int init_tracepoints(void)
32f85742 450{
de7b2973
MD
451 int ret;
452
453 ret = register_module_notifier(&tracepoint_module_nb);
eb7d035c 454 if (ret)
de7b2973 455 pr_warning("Failed to register tracepoint module enter notifier\n");
eb7d035c 456
de7b2973 457 return ret;
32f85742
MD
458}
459__initcall(init_tracepoints);
227a8375 460#endif /* CONFIG_MODULES */
a871bd33 461
de7b2973
MD
462static 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 */
480void 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}
486EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
487
3d27d8cb 488#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
60d970c2 489
97419875 490/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
a871bd33
JB
491static int sys_tracepoint_refcount;
492
493void syscall_regfunc(void)
494{
8063e41d 495 struct task_struct *p, *t;
a871bd33 496
a871bd33 497 if (!sys_tracepoint_refcount) {
8063e41d
ON
498 read_lock(&tasklist_lock);
499 for_each_process_thread(p, t) {
ea73c79e 500 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
8063e41d
ON
501 }
502 read_unlock(&tasklist_lock);
a871bd33
JB
503 }
504 sys_tracepoint_refcount++;
a871bd33
JB
505}
506
507void syscall_unregfunc(void)
508{
8063e41d 509 struct task_struct *p, *t;
a871bd33 510
a871bd33
JB
511 sys_tracepoint_refcount--;
512 if (!sys_tracepoint_refcount) {
8063e41d
ON
513 read_lock(&tasklist_lock);
514 for_each_process_thread(p, t) {
66700001 515 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
8063e41d
ON
516 }
517 read_unlock(&tasklist_lock);
a871bd33 518 }
a871bd33 519}
60d970c2 520#endif