| 1 | /* |
| 2 | * Copyright (C) 2008-2011 Mathieu Desnoyers |
| 3 | * Copyright (C) 2009 Pierre-Marc Fournier |
| 4 | * |
| 5 | * This library is free software; you can redistribute it and/or |
| 6 | * modify it under the terms of the GNU Lesser General Public |
| 7 | * License as published by the Free Software Foundation; |
| 8 | * version 2.1 of the License. |
| 9 | * |
| 10 | * This library is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | * Lesser General Public License for more details. |
| 14 | * |
| 15 | * You should have received a copy of the GNU Lesser General Public |
| 16 | * License along with this library; if not, write to the Free Software |
| 17 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 18 | * |
| 19 | * Ported to userspace by Pierre-Marc Fournier. |
| 20 | */ |
| 21 | |
| 22 | #define _LGPL_SOURCE |
| 23 | #include <errno.h> |
| 24 | #include <stdint.h> |
| 25 | #include <stddef.h> |
| 26 | |
| 27 | #include <urcu/arch.h> |
| 28 | #include <urcu-bp.h> |
| 29 | #include <urcu/hlist.h> |
| 30 | #include <urcu/uatomic.h> |
| 31 | #include <urcu/compiler.h> |
| 32 | |
| 33 | #include <lttng/tracepoint.h> |
| 34 | |
| 35 | #include <usterr-signal-safe.h> |
| 36 | #include <helper.h> |
| 37 | |
| 38 | #include "tracepoint-internal.h" |
| 39 | #include "ltt-tracer-core.h" |
| 40 | #include "jhash.h" |
| 41 | #include "error.h" |
| 42 | |
| 43 | /* Set to 1 to enable tracepoint debug output */ |
| 44 | static const int tracepoint_debug; |
| 45 | static int initialized; |
| 46 | static void (*new_tracepoint_cb)(struct tracepoint *); |
| 47 | |
| 48 | /* |
| 49 | * libraries that contain tracepoints (struct tracepoint_lib). |
| 50 | * Protected by UST lock. |
| 51 | */ |
| 52 | static CDS_LIST_HEAD(libs); |
| 53 | |
| 54 | /* |
| 55 | * The UST lock protects the library tracepoints, the hash table, and |
| 56 | * the library list. |
| 57 | * All calls to the tracepoint API must be protected by the UST lock, |
| 58 | * excepts calls to tracepoint_register_lib and |
| 59 | * tracepoint_unregister_lib, which take the UST lock themselves. |
| 60 | */ |
| 61 | |
| 62 | /* |
| 63 | * Tracepoint hash table, containing the active tracepoints. |
| 64 | * Protected by ust lock. |
| 65 | */ |
| 66 | #define TRACEPOINT_HASH_BITS 6 |
| 67 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) |
| 68 | static struct cds_hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; |
| 69 | |
| 70 | static CDS_LIST_HEAD(old_probes); |
| 71 | static int need_update; |
| 72 | |
| 73 | /* |
| 74 | * Note about RCU : |
| 75 | * It is used to to delay the free of multiple probes array until a quiescent |
| 76 | * state is reached. |
| 77 | * Tracepoint entries modifications are protected by the ust lock. |
| 78 | */ |
| 79 | struct tracepoint_entry { |
| 80 | struct cds_hlist_node hlist; |
| 81 | struct tracepoint_probe *probes; |
| 82 | int refcount; /* Number of times armed. 0 if disarmed. */ |
| 83 | char name[0]; |
| 84 | }; |
| 85 | |
| 86 | struct tp_probes { |
| 87 | union { |
| 88 | struct cds_list_head list; |
| 89 | } u; |
| 90 | struct tracepoint_probe probes[0]; |
| 91 | }; |
| 92 | |
| 93 | static void *allocate_probes(int count) |
| 94 | { |
| 95 | struct tp_probes *p = zmalloc(count * sizeof(struct tracepoint_probe) |
| 96 | + sizeof(struct tp_probes)); |
| 97 | return p == NULL ? NULL : p->probes; |
| 98 | } |
| 99 | |
| 100 | static void release_probes(void *old) |
| 101 | { |
| 102 | if (old) { |
| 103 | struct tp_probes *tp_probes = caa_container_of(old, |
| 104 | struct tp_probes, probes[0]); |
| 105 | synchronize_rcu(); |
| 106 | free(tp_probes); |
| 107 | } |
| 108 | } |
| 109 | |
| 110 | static void debug_print_probes(struct tracepoint_entry *entry) |
| 111 | { |
| 112 | int i; |
| 113 | |
| 114 | if (!tracepoint_debug || !entry->probes) |
| 115 | return; |
| 116 | |
| 117 | for (i = 0; entry->probes[i].func; i++) |
| 118 | DBG("Probe %d : %p", i, entry->probes[i].func); |
| 119 | } |
| 120 | |
| 121 | static void * |
| 122 | tracepoint_entry_add_probe(struct tracepoint_entry *entry, |
| 123 | void *probe, void *data) |
| 124 | { |
| 125 | int nr_probes = 0; |
| 126 | struct tracepoint_probe *old, *new; |
| 127 | |
| 128 | WARN_ON(!probe); |
| 129 | |
| 130 | debug_print_probes(entry); |
| 131 | old = entry->probes; |
| 132 | if (old) { |
| 133 | /* (N -> N+1), (N != 0, 1) probes */ |
| 134 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) |
| 135 | if (old[nr_probes].func == probe && |
| 136 | old[nr_probes].data == data) |
| 137 | return ERR_PTR(-EEXIST); |
| 138 | } |
| 139 | /* + 2 : one for new probe, one for NULL func */ |
| 140 | new = allocate_probes(nr_probes + 2); |
| 141 | if (new == NULL) |
| 142 | return ERR_PTR(-ENOMEM); |
| 143 | if (old) |
| 144 | memcpy(new, old, nr_probes * sizeof(struct tracepoint_probe)); |
| 145 | new[nr_probes].func = probe; |
| 146 | new[nr_probes].data = data; |
| 147 | new[nr_probes + 1].func = NULL; |
| 148 | entry->refcount = nr_probes + 1; |
| 149 | entry->probes = new; |
| 150 | debug_print_probes(entry); |
| 151 | return old; |
| 152 | } |
| 153 | |
| 154 | static void * |
| 155 | tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe, |
| 156 | void *data) |
| 157 | { |
| 158 | int nr_probes = 0, nr_del = 0, i; |
| 159 | struct tracepoint_probe *old, *new; |
| 160 | |
| 161 | old = entry->probes; |
| 162 | |
| 163 | if (!old) |
| 164 | return ERR_PTR(-ENOENT); |
| 165 | |
| 166 | debug_print_probes(entry); |
| 167 | /* (N -> M), (N > 1, M >= 0) probes */ |
| 168 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
| 169 | if (!probe || |
| 170 | (old[nr_probes].func == probe && |
| 171 | old[nr_probes].data == data)) |
| 172 | nr_del++; |
| 173 | } |
| 174 | |
| 175 | if (nr_probes - nr_del == 0) { |
| 176 | /* N -> 0, (N > 1) */ |
| 177 | entry->probes = NULL; |
| 178 | entry->refcount = 0; |
| 179 | debug_print_probes(entry); |
| 180 | return old; |
| 181 | } else { |
| 182 | int j = 0; |
| 183 | /* N -> M, (N > 1, M > 0) */ |
| 184 | /* + 1 for NULL */ |
| 185 | new = allocate_probes(nr_probes - nr_del + 1); |
| 186 | if (new == NULL) |
| 187 | return ERR_PTR(-ENOMEM); |
| 188 | for (i = 0; old[i].func; i++) |
| 189 | if (probe && |
| 190 | (old[i].func != probe || old[i].data != data)) |
| 191 | new[j++] = old[i]; |
| 192 | new[nr_probes - nr_del].func = NULL; |
| 193 | entry->refcount = nr_probes - nr_del; |
| 194 | entry->probes = new; |
| 195 | } |
| 196 | debug_print_probes(entry); |
| 197 | return old; |
| 198 | } |
| 199 | |
| 200 | /* |
| 201 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. |
| 202 | * Must be called with ust lock held. |
| 203 | * Returns NULL if not present. |
| 204 | */ |
| 205 | static struct tracepoint_entry *get_tracepoint(const char *name) |
| 206 | { |
| 207 | struct cds_hlist_head *head; |
| 208 | struct cds_hlist_node *node; |
| 209 | struct tracepoint_entry *e; |
| 210 | uint32_t hash = jhash(name, strlen(name), 0); |
| 211 | |
| 212 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 213 | cds_hlist_for_each_entry(e, node, head, hlist) { |
| 214 | if (!strcmp(name, e->name)) |
| 215 | return e; |
| 216 | } |
| 217 | return NULL; |
| 218 | } |
| 219 | |
| 220 | /* |
| 221 | * Add the tracepoint to the tracepoint hash table. Must be called with |
| 222 | * ust lock held. |
| 223 | */ |
| 224 | static struct tracepoint_entry *add_tracepoint(const char *name) |
| 225 | { |
| 226 | struct cds_hlist_head *head; |
| 227 | struct cds_hlist_node *node; |
| 228 | struct tracepoint_entry *e; |
| 229 | size_t name_len = strlen(name) + 1; |
| 230 | uint32_t hash = jhash(name, name_len-1, 0); |
| 231 | |
| 232 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 233 | cds_hlist_for_each_entry(e, node, head, hlist) { |
| 234 | if (!strcmp(name, e->name)) { |
| 235 | DBG("tracepoint %s busy", name); |
| 236 | return ERR_PTR(-EEXIST); /* Already there */ |
| 237 | } |
| 238 | } |
| 239 | /* |
| 240 | * Using zmalloc here to allocate a variable length element. Could |
| 241 | * cause some memory fragmentation if overused. |
| 242 | */ |
| 243 | e = zmalloc(sizeof(struct tracepoint_entry) + name_len); |
| 244 | if (!e) |
| 245 | return ERR_PTR(-ENOMEM); |
| 246 | memcpy(&e->name[0], name, name_len); |
| 247 | e->probes = NULL; |
| 248 | e->refcount = 0; |
| 249 | cds_hlist_add_head(&e->hlist, head); |
| 250 | return e; |
| 251 | } |
| 252 | |
| 253 | /* |
| 254 | * Remove the tracepoint from the tracepoint hash table. Must be called with |
| 255 | * ust_lock held. |
| 256 | */ |
| 257 | static void remove_tracepoint(struct tracepoint_entry *e) |
| 258 | { |
| 259 | cds_hlist_del(&e->hlist); |
| 260 | free(e); |
| 261 | } |
| 262 | |
| 263 | /* |
| 264 | * Sets the probe callback corresponding to one tracepoint. |
| 265 | */ |
| 266 | static void set_tracepoint(struct tracepoint_entry **entry, |
| 267 | struct tracepoint *elem, int active) |
| 268 | { |
| 269 | WARN_ON(strcmp((*entry)->name, elem->name) != 0); |
| 270 | |
| 271 | /* |
| 272 | * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new |
| 273 | * probe callbacks array is consistent before setting a pointer to it. |
| 274 | * This array is referenced by __DO_TRACE from |
| 275 | * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends() |
| 276 | * is used. |
| 277 | */ |
| 278 | rcu_assign_pointer(elem->probes, (*entry)->probes); |
| 279 | elem->state = active; |
| 280 | } |
| 281 | |
| 282 | /* |
| 283 | * Disable a tracepoint and its probe callback. |
| 284 | * Note: only waiting an RCU period after setting elem->call to the empty |
| 285 | * function insures that the original callback is not used anymore. This insured |
| 286 | * by preempt_disable around the call site. |
| 287 | */ |
| 288 | static void disable_tracepoint(struct tracepoint *elem) |
| 289 | { |
| 290 | elem->state = 0; |
| 291 | rcu_assign_pointer(elem->probes, NULL); |
| 292 | } |
| 293 | |
| 294 | /** |
| 295 | * tracepoint_update_probe_range - Update a probe range |
| 296 | * @begin: beginning of the range |
| 297 | * @end: end of the range |
| 298 | * |
| 299 | * Updates the probe callback corresponding to a range of tracepoints. |
| 300 | */ |
| 301 | static |
| 302 | void tracepoint_update_probe_range(struct tracepoint * const *begin, |
| 303 | struct tracepoint * const *end) |
| 304 | { |
| 305 | struct tracepoint * const *iter; |
| 306 | struct tracepoint_entry *mark_entry; |
| 307 | |
| 308 | for (iter = begin; iter < end; iter++) { |
| 309 | if (!*iter) |
| 310 | continue; /* skip dummy */ |
| 311 | if (!(*iter)->name) { |
| 312 | disable_tracepoint(*iter); |
| 313 | continue; |
| 314 | } |
| 315 | mark_entry = get_tracepoint((*iter)->name); |
| 316 | if (mark_entry) { |
| 317 | set_tracepoint(&mark_entry, *iter, |
| 318 | !!mark_entry->refcount); |
| 319 | } else { |
| 320 | disable_tracepoint(*iter); |
| 321 | } |
| 322 | } |
| 323 | } |
| 324 | |
| 325 | static void lib_update_tracepoints(void) |
| 326 | { |
| 327 | struct tracepoint_lib *lib; |
| 328 | |
| 329 | cds_list_for_each_entry(lib, &libs, list) { |
| 330 | tracepoint_update_probe_range(lib->tracepoints_start, |
| 331 | lib->tracepoints_start + lib->tracepoints_count); |
| 332 | } |
| 333 | } |
| 334 | |
| 335 | /* |
| 336 | * Update probes, removing the faulty probes. |
| 337 | */ |
| 338 | static void tracepoint_update_probes(void) |
| 339 | { |
| 340 | /* tracepoints registered from libraries and executable. */ |
| 341 | lib_update_tracepoints(); |
| 342 | } |
| 343 | |
| 344 | static struct tracepoint_probe * |
| 345 | tracepoint_add_probe(const char *name, void *probe, void *data) |
| 346 | { |
| 347 | struct tracepoint_entry *entry; |
| 348 | struct tracepoint_probe *old; |
| 349 | |
| 350 | entry = get_tracepoint(name); |
| 351 | if (!entry) { |
| 352 | entry = add_tracepoint(name); |
| 353 | if (IS_ERR(entry)) |
| 354 | return (struct tracepoint_probe *)entry; |
| 355 | } |
| 356 | old = tracepoint_entry_add_probe(entry, probe, data); |
| 357 | if (IS_ERR(old) && !entry->refcount) |
| 358 | remove_tracepoint(entry); |
| 359 | return old; |
| 360 | } |
| 361 | |
| 362 | /** |
| 363 | * __tracepoint_probe_register - Connect a probe to a tracepoint |
| 364 | * @name: tracepoint name |
| 365 | * @probe: probe handler |
| 366 | * |
| 367 | * Returns 0 if ok, error value on error. |
| 368 | * The probe address must at least be aligned on the architecture pointer size. |
| 369 | * Called with the UST lock held. |
| 370 | */ |
| 371 | int __tracepoint_probe_register(const char *name, void *probe, void *data) |
| 372 | { |
| 373 | void *old; |
| 374 | |
| 375 | old = tracepoint_add_probe(name, probe, data); |
| 376 | if (IS_ERR(old)) |
| 377 | return PTR_ERR(old); |
| 378 | |
| 379 | tracepoint_update_probes(); /* may update entry */ |
| 380 | release_probes(old); |
| 381 | return 0; |
| 382 | } |
| 383 | |
| 384 | static void *tracepoint_remove_probe(const char *name, void *probe, void *data) |
| 385 | { |
| 386 | struct tracepoint_entry *entry; |
| 387 | void *old; |
| 388 | |
| 389 | entry = get_tracepoint(name); |
| 390 | if (!entry) |
| 391 | return ERR_PTR(-ENOENT); |
| 392 | old = tracepoint_entry_remove_probe(entry, probe, data); |
| 393 | if (IS_ERR(old)) |
| 394 | return old; |
| 395 | if (!entry->refcount) |
| 396 | remove_tracepoint(entry); |
| 397 | return old; |
| 398 | } |
| 399 | |
| 400 | /** |
| 401 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint |
| 402 | * @name: tracepoint name |
| 403 | * @probe: probe function pointer |
| 404 | * @probe: probe data pointer |
| 405 | * |
| 406 | * Called with the UST lock held. |
| 407 | */ |
| 408 | int __tracepoint_probe_unregister(const char *name, void *probe, void *data) |
| 409 | { |
| 410 | void *old; |
| 411 | |
| 412 | old = tracepoint_remove_probe(name, probe, data); |
| 413 | if (IS_ERR(old)) |
| 414 | return PTR_ERR(old); |
| 415 | |
| 416 | tracepoint_update_probes(); /* may update entry */ |
| 417 | release_probes(old); |
| 418 | return 0; |
| 419 | } |
| 420 | |
| 421 | static void tracepoint_add_old_probes(void *old) |
| 422 | { |
| 423 | need_update = 1; |
| 424 | if (old) { |
| 425 | struct tp_probes *tp_probes = caa_container_of(old, |
| 426 | struct tp_probes, probes[0]); |
| 427 | cds_list_add(&tp_probes->u.list, &old_probes); |
| 428 | } |
| 429 | } |
| 430 | |
| 431 | /** |
| 432 | * tracepoint_probe_register_noupdate - register a probe but not connect |
| 433 | * @name: tracepoint name |
| 434 | * @probe: probe handler |
| 435 | * |
| 436 | * caller must call tracepoint_probe_update_all() |
| 437 | * Called with the UST lock held. |
| 438 | */ |
| 439 | int tracepoint_probe_register_noupdate(const char *name, void *probe, |
| 440 | void *data) |
| 441 | { |
| 442 | void *old; |
| 443 | |
| 444 | old = tracepoint_add_probe(name, probe, data); |
| 445 | if (IS_ERR(old)) { |
| 446 | return PTR_ERR(old); |
| 447 | } |
| 448 | tracepoint_add_old_probes(old); |
| 449 | return 0; |
| 450 | } |
| 451 | |
| 452 | /** |
| 453 | * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect |
| 454 | * @name: tracepoint name |
| 455 | * @probe: probe function pointer |
| 456 | * |
| 457 | * caller must call tracepoint_probe_update_all() |
| 458 | * Called with the UST lock held. |
| 459 | */ |
| 460 | int tracepoint_probe_unregister_noupdate(const char *name, void *probe, |
| 461 | void *data) |
| 462 | { |
| 463 | void *old; |
| 464 | |
| 465 | old = tracepoint_remove_probe(name, probe, data); |
| 466 | if (IS_ERR(old)) { |
| 467 | return PTR_ERR(old); |
| 468 | } |
| 469 | tracepoint_add_old_probes(old); |
| 470 | return 0; |
| 471 | } |
| 472 | |
| 473 | /** |
| 474 | * tracepoint_probe_update_all - update tracepoints |
| 475 | * Called with the UST lock held. |
| 476 | */ |
| 477 | void tracepoint_probe_update_all(void) |
| 478 | { |
| 479 | CDS_LIST_HEAD(release_probes); |
| 480 | struct tp_probes *pos, *next; |
| 481 | |
| 482 | if (!need_update) { |
| 483 | return; |
| 484 | } |
| 485 | if (!cds_list_empty(&old_probes)) |
| 486 | cds_list_replace_init(&old_probes, &release_probes); |
| 487 | need_update = 0; |
| 488 | |
| 489 | tracepoint_update_probes(); |
| 490 | cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) { |
| 491 | cds_list_del(&pos->u.list); |
| 492 | synchronize_rcu(); |
| 493 | free(pos); |
| 494 | } |
| 495 | } |
| 496 | |
| 497 | void tracepoint_set_new_tracepoint_cb(void (*cb)(struct tracepoint *)) |
| 498 | { |
| 499 | new_tracepoint_cb = cb; |
| 500 | } |
| 501 | |
| 502 | static void new_tracepoints(struct tracepoint * const *start, struct tracepoint * const *end) |
| 503 | { |
| 504 | if (new_tracepoint_cb) { |
| 505 | struct tracepoint * const *t; |
| 506 | |
| 507 | for (t = start; t < end; t++) { |
| 508 | if (*t) |
| 509 | new_tracepoint_cb(*t); |
| 510 | } |
| 511 | } |
| 512 | } |
| 513 | |
| 514 | int tracepoint_register_lib(struct tracepoint * const *tracepoints_start, |
| 515 | int tracepoints_count) |
| 516 | { |
| 517 | struct tracepoint_lib *pl, *iter; |
| 518 | |
| 519 | init_tracepoint(); |
| 520 | |
| 521 | pl = (struct tracepoint_lib *) zmalloc(sizeof(struct tracepoint_lib)); |
| 522 | |
| 523 | pl->tracepoints_start = tracepoints_start; |
| 524 | pl->tracepoints_count = tracepoints_count; |
| 525 | |
| 526 | ust_lock(); |
| 527 | /* |
| 528 | * We sort the libs by struct lib pointer address. |
| 529 | */ |
| 530 | cds_list_for_each_entry_reverse(iter, &libs, list) { |
| 531 | BUG_ON(iter == pl); /* Should never be in the list twice */ |
| 532 | if (iter < pl) { |
| 533 | /* We belong to the location right after iter. */ |
| 534 | cds_list_add(&pl->list, &iter->list); |
| 535 | goto lib_added; |
| 536 | } |
| 537 | } |
| 538 | /* We should be added at the head of the list */ |
| 539 | cds_list_add(&pl->list, &libs); |
| 540 | lib_added: |
| 541 | new_tracepoints(tracepoints_start, tracepoints_start + tracepoints_count); |
| 542 | |
| 543 | /* TODO: update just the loaded lib */ |
| 544 | lib_update_tracepoints(); |
| 545 | ust_unlock(); |
| 546 | |
| 547 | DBG("just registered a tracepoints section from %p and having %d tracepoints", |
| 548 | tracepoints_start, tracepoints_count); |
| 549 | |
| 550 | return 0; |
| 551 | } |
| 552 | |
| 553 | int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start) |
| 554 | { |
| 555 | struct tracepoint_lib *lib; |
| 556 | |
| 557 | ust_lock(); |
| 558 | cds_list_for_each_entry(lib, &libs, list) { |
| 559 | if (lib->tracepoints_start == tracepoints_start) { |
| 560 | struct tracepoint_lib *lib2free = lib; |
| 561 | cds_list_del(&lib->list); |
| 562 | free(lib2free); |
| 563 | break; |
| 564 | } |
| 565 | } |
| 566 | ust_unlock(); |
| 567 | |
| 568 | return 0; |
| 569 | } |
| 570 | |
| 571 | void init_tracepoint(void) |
| 572 | { |
| 573 | if (uatomic_xchg(&initialized, 1) == 1) |
| 574 | return; |
| 575 | init_usterr(); |
| 576 | } |
| 577 | |
| 578 | void exit_tracepoint(void) |
| 579 | { |
| 580 | initialized = 0; |
| 581 | } |
| 582 | |
| 583 | /* |
| 584 | * Create the wrapper symbols. |
| 585 | */ |
| 586 | #undef tp_rcu_read_lock_bp |
| 587 | #undef tp_rcu_read_unlock_bp |
| 588 | #undef tp_rcu_dereference_bp |
| 589 | |
| 590 | void tp_rcu_read_lock_bp(void) |
| 591 | { |
| 592 | rcu_read_lock_bp(); |
| 593 | } |
| 594 | |
| 595 | void tp_rcu_read_unlock_bp(void) |
| 596 | { |
| 597 | rcu_read_unlock_bp(); |
| 598 | } |
| 599 | |
| 600 | void *tp_rcu_dereference_sym_bp(void *p) |
| 601 | { |
| 602 | return rcu_dereference_bp(p); |
| 603 | } |