| 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 | * @data: tracepoint data |
| 243 | * |
| 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. |
| 249 | */ |
| 250 | int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data) |
| 251 | { |
| 252 | struct tracepoint_func tp_func; |
| 253 | int ret; |
| 254 | |
| 255 | mutex_lock(&tracepoints_mutex); |
| 256 | tp_func.func = probe; |
| 257 | tp_func.data = data; |
| 258 | ret = tracepoint_add_func(tp, &tp_func); |
| 259 | mutex_unlock(&tracepoints_mutex); |
| 260 | return ret; |
| 261 | } |
| 262 | EXPORT_SYMBOL_GPL(tracepoint_probe_register); |
| 263 | |
| 264 | /** |
| 265 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint |
| 266 | * @tp: tracepoint |
| 267 | * @probe: probe function pointer |
| 268 | * @data: tracepoint data |
| 269 | * |
| 270 | * Returns 0 if ok, error value on error. |
| 271 | */ |
| 272 | int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data) |
| 273 | { |
| 274 | struct tracepoint_func tp_func; |
| 275 | int ret; |
| 276 | |
| 277 | mutex_lock(&tracepoints_mutex); |
| 278 | tp_func.func = probe; |
| 279 | tp_func.data = data; |
| 280 | ret = tracepoint_remove_func(tp, &tp_func); |
| 281 | mutex_unlock(&tracepoints_mutex); |
| 282 | return ret; |
| 283 | } |
| 284 | EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); |
| 285 | |
| 286 | #ifdef CONFIG_MODULES |
| 287 | bool trace_module_has_bad_taint(struct module *mod) |
| 288 | { |
| 289 | return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) | |
| 290 | (1 << TAINT_UNSIGNED_MODULE)); |
| 291 | } |
| 292 | |
| 293 | static 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 | */ |
| 304 | int 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); |
| 315 | end: |
| 316 | mutex_unlock(&tracepoint_module_list_mutex); |
| 317 | return ret; |
| 318 | } |
| 319 | EXPORT_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 | */ |
| 328 | int 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); |
| 339 | end: |
| 340 | mutex_unlock(&tracepoint_module_list_mutex); |
| 341 | return ret; |
| 342 | |
| 343 | } |
| 344 | EXPORT_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 | */ |
| 350 | static 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 | |
| 361 | static int tracepoint_module_coming(struct module *mod) |
| 362 | { |
| 363 | struct tp_module *tp_mod; |
| 364 | int ret = 0; |
| 365 | |
| 366 | if (!mod->num_tracepoints) |
| 367 | return 0; |
| 368 | |
| 369 | /* |
| 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. |
| 372 | * Staging, out-of-tree, and unsigned GPL modules are fine. |
| 373 | */ |
| 374 | if (trace_module_has_bad_taint(mod)) |
| 375 | return 0; |
| 376 | mutex_lock(&tracepoint_module_list_mutex); |
| 377 | tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL); |
| 378 | if (!tp_mod) { |
| 379 | ret = -ENOMEM; |
| 380 | goto end; |
| 381 | } |
| 382 | tp_mod->mod = mod; |
| 383 | list_add_tail(&tp_mod->list, &tracepoint_module_list); |
| 384 | blocking_notifier_call_chain(&tracepoint_notify_list, |
| 385 | MODULE_STATE_COMING, tp_mod); |
| 386 | end: |
| 387 | mutex_unlock(&tracepoint_module_list_mutex); |
| 388 | return ret; |
| 389 | } |
| 390 | |
| 391 | static void tracepoint_module_going(struct module *mod) |
| 392 | { |
| 393 | struct tp_module *tp_mod; |
| 394 | |
| 395 | if (!mod->num_tracepoints) |
| 396 | return; |
| 397 | |
| 398 | mutex_lock(&tracepoint_module_list_mutex); |
| 399 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) { |
| 400 | if (tp_mod->mod == mod) { |
| 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); |
| 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 | */ |
| 420 | mutex_unlock(&tracepoint_module_list_mutex); |
| 421 | } |
| 422 | |
| 423 | static int tracepoint_module_notify(struct notifier_block *self, |
| 424 | unsigned long val, void *data) |
| 425 | { |
| 426 | struct module *mod = data; |
| 427 | int ret = 0; |
| 428 | |
| 429 | switch (val) { |
| 430 | case MODULE_STATE_COMING: |
| 431 | ret = tracepoint_module_coming(mod); |
| 432 | break; |
| 433 | case MODULE_STATE_LIVE: |
| 434 | break; |
| 435 | case MODULE_STATE_GOING: |
| 436 | tracepoint_module_going(mod); |
| 437 | break; |
| 438 | case MODULE_STATE_UNFORMED: |
| 439 | break; |
| 440 | } |
| 441 | return ret; |
| 442 | } |
| 443 | |
| 444 | static struct notifier_block tracepoint_module_nb = { |
| 445 | .notifier_call = tracepoint_module_notify, |
| 446 | .priority = 0, |
| 447 | }; |
| 448 | |
| 449 | static __init int init_tracepoints(void) |
| 450 | { |
| 451 | int ret; |
| 452 | |
| 453 | ret = register_module_notifier(&tracepoint_module_nb); |
| 454 | if (ret) |
| 455 | pr_warning("Failed to register tracepoint module enter notifier\n"); |
| 456 | |
| 457 | return ret; |
| 458 | } |
| 459 | __initcall(init_tracepoints); |
| 460 | #endif /* CONFIG_MODULES */ |
| 461 | |
| 462 | static 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 | */ |
| 480 | void 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 | } |
| 486 | EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint); |
| 487 | |
| 488 | #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS |
| 489 | |
| 490 | /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ |
| 491 | static int sys_tracepoint_refcount; |
| 492 | |
| 493 | void syscall_regfunc(void) |
| 494 | { |
| 495 | struct task_struct *p, *t; |
| 496 | |
| 497 | if (!sys_tracepoint_refcount) { |
| 498 | read_lock(&tasklist_lock); |
| 499 | for_each_process_thread(p, t) { |
| 500 | set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
| 501 | } |
| 502 | read_unlock(&tasklist_lock); |
| 503 | } |
| 504 | sys_tracepoint_refcount++; |
| 505 | } |
| 506 | |
| 507 | void syscall_unregfunc(void) |
| 508 | { |
| 509 | struct task_struct *p, *t; |
| 510 | |
| 511 | sys_tracepoint_refcount--; |
| 512 | if (!sys_tracepoint_refcount) { |
| 513 | read_lock(&tasklist_lock); |
| 514 | for_each_process_thread(p, t) { |
| 515 | clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
| 516 | } |
| 517 | read_unlock(&tasklist_lock); |
| 518 | } |
| 519 | } |
| 520 | #endif |