| 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 | #include <stdio.h> |
| 27 | |
| 28 | #include <urcu/arch.h> |
| 29 | #include <urcu-bp.h> |
| 30 | #include <urcu/hlist.h> |
| 31 | #include <urcu/uatomic.h> |
| 32 | #include <urcu/compiler.h> |
| 33 | #include <urcu/system.h> |
| 34 | |
| 35 | #include <lttng/tracepoint.h> |
| 36 | #include <lttng/ust-abi.h> /* for LTTNG_UST_SYM_NAME_LEN */ |
| 37 | |
| 38 | #include <usterr-signal-safe.h> |
| 39 | #include <helper.h> |
| 40 | |
| 41 | #include "tracepoint-internal.h" |
| 42 | #include "lttng-tracer-core.h" |
| 43 | #include "jhash.h" |
| 44 | #include "error.h" |
| 45 | |
| 46 | /* Test compiler support for weak symbols with hidden visibility. */ |
| 47 | int __tracepoint_test_symbol1 __attribute__((weak, visibility("hidden"))); |
| 48 | void *__tracepoint_test_symbol2 __attribute__((weak, visibility("hidden"))); |
| 49 | struct { |
| 50 | char a[24]; |
| 51 | } __tracepoint_test_symbol3 __attribute__((weak, visibility("hidden"))); |
| 52 | |
| 53 | /* Set to 1 to enable tracepoint debug output */ |
| 54 | static const int tracepoint_debug; |
| 55 | static int initialized; |
| 56 | static void (*new_tracepoint_cb)(struct lttng_ust_tracepoint *); |
| 57 | |
| 58 | /* |
| 59 | * tracepoint_mutex nests inside UST mutex. |
| 60 | * |
| 61 | * Note about interaction with fork/clone: UST does not hold the |
| 62 | * tracepoint mutex across fork/clone because it is either: |
| 63 | * - nested within UST mutex, in which case holding the UST mutex across |
| 64 | * fork/clone suffice, |
| 65 | * - taken by a library constructor, which should never race with a |
| 66 | * fork/clone if the application is expected to continue running with |
| 67 | * the same memory layout (no following exec()). |
| 68 | */ |
| 69 | static pthread_mutex_t tracepoint_mutex = PTHREAD_MUTEX_INITIALIZER; |
| 70 | |
| 71 | /* |
| 72 | * libraries that contain tracepoints (struct tracepoint_lib). |
| 73 | * Protected by tracepoint mutex. |
| 74 | */ |
| 75 | static CDS_LIST_HEAD(libs); |
| 76 | |
| 77 | /* |
| 78 | * The tracepoint mutex protects the library tracepoints, the hash table, and |
| 79 | * the library list. |
| 80 | * All calls to the tracepoint API must be protected by the tracepoint mutex, |
| 81 | * excepts calls to tracepoint_register_lib and |
| 82 | * tracepoint_unregister_lib, which take the tracepoint mutex themselves. |
| 83 | */ |
| 84 | |
| 85 | /* |
| 86 | * Tracepoint hash table, containing the active tracepoints. |
| 87 | * Protected by tracepoint mutex. |
| 88 | */ |
| 89 | #define TRACEPOINT_HASH_BITS 12 |
| 90 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) |
| 91 | static struct cds_hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; |
| 92 | |
| 93 | static CDS_LIST_HEAD(old_probes); |
| 94 | static int need_update; |
| 95 | |
| 96 | static CDS_LIST_HEAD(release_queue); |
| 97 | static int release_queue_need_update; |
| 98 | |
| 99 | /* |
| 100 | * Note about RCU : |
| 101 | * It is used to to delay the free of multiple probes array until a quiescent |
| 102 | * state is reached. |
| 103 | * Tracepoint entries modifications are protected by the tracepoint mutex. |
| 104 | */ |
| 105 | struct tracepoint_entry { |
| 106 | struct cds_hlist_node hlist; |
| 107 | struct lttng_ust_tracepoint_probe *probes; |
| 108 | int refcount; /* Number of times armed. 0 if disarmed. */ |
| 109 | int callsite_refcount; /* how many libs use this tracepoint */ |
| 110 | const char *signature; |
| 111 | char name[0]; |
| 112 | }; |
| 113 | |
| 114 | struct tp_probes { |
| 115 | union { |
| 116 | struct cds_list_head list; |
| 117 | /* Field below only used for call_rcu scheme */ |
| 118 | /* struct rcu_head head; */ |
| 119 | } u; |
| 120 | struct lttng_ust_tracepoint_probe probes[0]; |
| 121 | }; |
| 122 | |
| 123 | /* |
| 124 | * Callsite hash table, containing the tracepoint call sites. |
| 125 | * Protected by tracepoint mutex. |
| 126 | */ |
| 127 | #define CALLSITE_HASH_BITS 12 |
| 128 | #define CALLSITE_TABLE_SIZE (1 << CALLSITE_HASH_BITS) |
| 129 | static struct cds_hlist_head callsite_table[CALLSITE_TABLE_SIZE]; |
| 130 | |
| 131 | struct callsite_entry { |
| 132 | struct cds_hlist_node hlist; /* hash table node */ |
| 133 | struct cds_list_head node; /* lib list of callsites node */ |
| 134 | struct lttng_ust_tracepoint *tp; |
| 135 | }; |
| 136 | |
| 137 | /* coverity[+alloc] */ |
| 138 | static void *allocate_probes(int count) |
| 139 | { |
| 140 | struct tp_probes *p = |
| 141 | zmalloc(count * sizeof(struct lttng_ust_tracepoint_probe) |
| 142 | + sizeof(struct tp_probes)); |
| 143 | return p == NULL ? NULL : p->probes; |
| 144 | } |
| 145 | |
| 146 | /* coverity[+free : arg-0] */ |
| 147 | static void release_probes(void *old) |
| 148 | { |
| 149 | if (old) { |
| 150 | struct tp_probes *tp_probes = caa_container_of(old, |
| 151 | struct tp_probes, probes[0]); |
| 152 | synchronize_rcu(); |
| 153 | free(tp_probes); |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | static void debug_print_probes(struct tracepoint_entry *entry) |
| 158 | { |
| 159 | int i; |
| 160 | |
| 161 | if (!tracepoint_debug || !entry->probes) |
| 162 | return; |
| 163 | |
| 164 | for (i = 0; entry->probes[i].func; i++) |
| 165 | DBG("Probe %d : %p", i, entry->probes[i].func); |
| 166 | } |
| 167 | |
| 168 | static void * |
| 169 | tracepoint_entry_add_probe(struct tracepoint_entry *entry, |
| 170 | void (*probe)(void), void *data) |
| 171 | { |
| 172 | int nr_probes = 0; |
| 173 | struct lttng_ust_tracepoint_probe *old, *new; |
| 174 | |
| 175 | if (!probe) { |
| 176 | WARN_ON(1); |
| 177 | return ERR_PTR(-EINVAL); |
| 178 | } |
| 179 | debug_print_probes(entry); |
| 180 | old = entry->probes; |
| 181 | if (old) { |
| 182 | /* (N -> N+1), (N != 0, 1) probes */ |
| 183 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) |
| 184 | if (old[nr_probes].func == probe && |
| 185 | old[nr_probes].data == data) |
| 186 | return ERR_PTR(-EEXIST); |
| 187 | } |
| 188 | /* + 2 : one for new probe, one for NULL func */ |
| 189 | new = allocate_probes(nr_probes + 2); |
| 190 | if (new == NULL) |
| 191 | return ERR_PTR(-ENOMEM); |
| 192 | if (old) |
| 193 | memcpy(new, old, |
| 194 | nr_probes * sizeof(struct lttng_ust_tracepoint_probe)); |
| 195 | new[nr_probes].func = probe; |
| 196 | new[nr_probes].data = data; |
| 197 | new[nr_probes + 1].func = NULL; |
| 198 | entry->refcount = nr_probes + 1; |
| 199 | entry->probes = new; |
| 200 | debug_print_probes(entry); |
| 201 | return old; |
| 202 | } |
| 203 | |
| 204 | static void * |
| 205 | tracepoint_entry_remove_probe(struct tracepoint_entry *entry, |
| 206 | void (*probe)(void), void *data) |
| 207 | { |
| 208 | int nr_probes = 0, nr_del = 0, i; |
| 209 | struct lttng_ust_tracepoint_probe *old, *new; |
| 210 | |
| 211 | old = entry->probes; |
| 212 | |
| 213 | if (!old) |
| 214 | return ERR_PTR(-ENOENT); |
| 215 | |
| 216 | debug_print_probes(entry); |
| 217 | /* (N -> M), (N > 1, M >= 0) probes */ |
| 218 | if (probe) { |
| 219 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
| 220 | if (old[nr_probes].func == probe && |
| 221 | old[nr_probes].data == data) |
| 222 | nr_del++; |
| 223 | } |
| 224 | } |
| 225 | |
| 226 | if (nr_probes - nr_del == 0) { |
| 227 | /* N -> 0, (N > 1) */ |
| 228 | entry->probes = NULL; |
| 229 | entry->refcount = 0; |
| 230 | debug_print_probes(entry); |
| 231 | return old; |
| 232 | } else { |
| 233 | int j = 0; |
| 234 | /* N -> M, (N > 1, M > 0) */ |
| 235 | /* + 1 for NULL */ |
| 236 | new = allocate_probes(nr_probes - nr_del + 1); |
| 237 | if (new == NULL) |
| 238 | return ERR_PTR(-ENOMEM); |
| 239 | for (i = 0; old[i].func; i++) |
| 240 | if (old[i].func != probe || old[i].data != data) |
| 241 | new[j++] = old[i]; |
| 242 | new[nr_probes - nr_del].func = NULL; |
| 243 | entry->refcount = nr_probes - nr_del; |
| 244 | entry->probes = new; |
| 245 | } |
| 246 | debug_print_probes(entry); |
| 247 | return old; |
| 248 | } |
| 249 | |
| 250 | /* |
| 251 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. |
| 252 | * Must be called with tracepoint mutex held. |
| 253 | * Returns NULL if not present. |
| 254 | */ |
| 255 | static struct tracepoint_entry *get_tracepoint(const char *name) |
| 256 | { |
| 257 | struct cds_hlist_head *head; |
| 258 | struct cds_hlist_node *node; |
| 259 | struct tracepoint_entry *e; |
| 260 | size_t name_len = strlen(name); |
| 261 | uint32_t hash; |
| 262 | |
| 263 | if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) { |
| 264 | WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); |
| 265 | name_len = LTTNG_UST_SYM_NAME_LEN - 1; |
| 266 | } |
| 267 | hash = jhash(name, name_len, 0); |
| 268 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 269 | cds_hlist_for_each_entry(e, node, head, hlist) { |
| 270 | if (!strncmp(name, e->name, LTTNG_UST_SYM_NAME_LEN - 1)) |
| 271 | return e; |
| 272 | } |
| 273 | return NULL; |
| 274 | } |
| 275 | |
| 276 | /* |
| 277 | * Add the tracepoint to the tracepoint hash table. Must be called with |
| 278 | * tracepoint mutex held. |
| 279 | */ |
| 280 | static struct tracepoint_entry *add_tracepoint(const char *name, |
| 281 | const char *signature) |
| 282 | { |
| 283 | struct cds_hlist_head *head; |
| 284 | struct cds_hlist_node *node; |
| 285 | struct tracepoint_entry *e; |
| 286 | size_t name_len = strlen(name); |
| 287 | uint32_t hash; |
| 288 | |
| 289 | if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) { |
| 290 | WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); |
| 291 | name_len = LTTNG_UST_SYM_NAME_LEN - 1; |
| 292 | } |
| 293 | hash = jhash(name, name_len, 0); |
| 294 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 295 | cds_hlist_for_each_entry(e, node, head, hlist) { |
| 296 | if (!strncmp(name, e->name, LTTNG_UST_SYM_NAME_LEN - 1)) { |
| 297 | DBG("tracepoint %s busy", name); |
| 298 | return ERR_PTR(-EEXIST); /* Already there */ |
| 299 | } |
| 300 | } |
| 301 | /* |
| 302 | * Using zmalloc here to allocate a variable length element. Could |
| 303 | * cause some memory fragmentation if overused. |
| 304 | */ |
| 305 | e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1); |
| 306 | if (!e) |
| 307 | return ERR_PTR(-ENOMEM); |
| 308 | memcpy(&e->name[0], name, name_len + 1); |
| 309 | e->name[name_len] = '\0'; |
| 310 | e->probes = NULL; |
| 311 | e->refcount = 0; |
| 312 | e->callsite_refcount = 0; |
| 313 | e->signature = signature; |
| 314 | cds_hlist_add_head(&e->hlist, head); |
| 315 | return e; |
| 316 | } |
| 317 | |
| 318 | /* |
| 319 | * Remove the tracepoint from the tracepoint hash table. Must be called with |
| 320 | * tracepoint mutex held. |
| 321 | */ |
| 322 | static void remove_tracepoint(struct tracepoint_entry *e) |
| 323 | { |
| 324 | cds_hlist_del(&e->hlist); |
| 325 | free(e); |
| 326 | } |
| 327 | |
| 328 | /* |
| 329 | * Sets the probe callback corresponding to one tracepoint. |
| 330 | */ |
| 331 | static void set_tracepoint(struct tracepoint_entry **entry, |
| 332 | struct lttng_ust_tracepoint *elem, int active) |
| 333 | { |
| 334 | WARN_ON(strncmp((*entry)->name, elem->name, LTTNG_UST_SYM_NAME_LEN - 1) != 0); |
| 335 | /* |
| 336 | * Check that signatures match before connecting a probe to a |
| 337 | * tracepoint. Warn the user if they don't. |
| 338 | */ |
| 339 | if (strcmp(elem->signature, (*entry)->signature) != 0) { |
| 340 | static int warned = 0; |
| 341 | |
| 342 | /* Only print once, don't flood console. */ |
| 343 | if (!warned) { |
| 344 | WARN("Tracepoint signature mismatch, not enabling one or more tracepoints. Ensure that the tracepoint probes prototypes match the application."); |
| 345 | WARN("Tracepoint \"%s\" signatures: call: \"%s\" vs probe: \"%s\".", |
| 346 | elem->name, elem->signature, (*entry)->signature); |
| 347 | warned = 1; |
| 348 | } |
| 349 | /* Don't accept connecting non-matching signatures. */ |
| 350 | return; |
| 351 | } |
| 352 | |
| 353 | /* |
| 354 | * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new |
| 355 | * probe callbacks array is consistent before setting a pointer to it. |
| 356 | * This array is referenced by __DO_TRACE from |
| 357 | * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends() |
| 358 | * is used. |
| 359 | */ |
| 360 | rcu_assign_pointer(elem->probes, (*entry)->probes); |
| 361 | CMM_STORE_SHARED(elem->state, active); |
| 362 | } |
| 363 | |
| 364 | /* |
| 365 | * Disable a tracepoint and its probe callback. |
| 366 | * Note: only waiting an RCU period after setting elem->call to the empty |
| 367 | * function insures that the original callback is not used anymore. This insured |
| 368 | * by preempt_disable around the call site. |
| 369 | */ |
| 370 | static void disable_tracepoint(struct lttng_ust_tracepoint *elem) |
| 371 | { |
| 372 | CMM_STORE_SHARED(elem->state, 0); |
| 373 | rcu_assign_pointer(elem->probes, NULL); |
| 374 | } |
| 375 | |
| 376 | /* |
| 377 | * Add the callsite to the callsite hash table. Must be called with |
| 378 | * tracepoint mutex held. |
| 379 | */ |
| 380 | static void add_callsite(struct tracepoint_lib * lib, struct lttng_ust_tracepoint *tp) |
| 381 | { |
| 382 | struct cds_hlist_head *head; |
| 383 | struct callsite_entry *e; |
| 384 | const char *name = tp->name; |
| 385 | size_t name_len = strlen(name); |
| 386 | uint32_t hash; |
| 387 | struct tracepoint_entry *tp_entry; |
| 388 | |
| 389 | if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) { |
| 390 | WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); |
| 391 | name_len = LTTNG_UST_SYM_NAME_LEN - 1; |
| 392 | } |
| 393 | hash = jhash(name, name_len, 0); |
| 394 | head = &callsite_table[hash & (CALLSITE_TABLE_SIZE - 1)]; |
| 395 | e = zmalloc(sizeof(struct callsite_entry)); |
| 396 | if (!e) { |
| 397 | PERROR("Unable to add callsite for tracepoint \"%s\"", name); |
| 398 | return; |
| 399 | } |
| 400 | cds_hlist_add_head(&e->hlist, head); |
| 401 | e->tp = tp; |
| 402 | cds_list_add(&e->node, &lib->callsites); |
| 403 | |
| 404 | tp_entry = get_tracepoint(name); |
| 405 | if (!tp_entry) |
| 406 | return; |
| 407 | tp_entry->callsite_refcount++; |
| 408 | } |
| 409 | |
| 410 | /* |
| 411 | * Remove the callsite from the callsite hash table and from lib |
| 412 | * callsite list. Must be called with tracepoint mutex held. |
| 413 | */ |
| 414 | static void remove_callsite(struct callsite_entry *e) |
| 415 | { |
| 416 | struct tracepoint_entry *tp_entry; |
| 417 | |
| 418 | tp_entry = get_tracepoint(e->tp->name); |
| 419 | if (tp_entry) { |
| 420 | tp_entry->callsite_refcount--; |
| 421 | if (tp_entry->callsite_refcount == 0) |
| 422 | disable_tracepoint(e->tp); |
| 423 | } |
| 424 | cds_hlist_del(&e->hlist); |
| 425 | cds_list_del(&e->node); |
| 426 | free(e); |
| 427 | } |
| 428 | |
| 429 | /* |
| 430 | * Enable/disable all callsites based on the state of a specific |
| 431 | * tracepoint entry. |
| 432 | * Must be called with tracepoint mutex held. |
| 433 | */ |
| 434 | static void tracepoint_sync_callsites(const char *name) |
| 435 | { |
| 436 | struct cds_hlist_head *head; |
| 437 | struct cds_hlist_node *node; |
| 438 | struct callsite_entry *e; |
| 439 | size_t name_len = strlen(name); |
| 440 | uint32_t hash; |
| 441 | struct tracepoint_entry *tp_entry; |
| 442 | |
| 443 | tp_entry = get_tracepoint(name); |
| 444 | if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) { |
| 445 | WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); |
| 446 | name_len = LTTNG_UST_SYM_NAME_LEN - 1; |
| 447 | } |
| 448 | hash = jhash(name, name_len, 0); |
| 449 | head = &callsite_table[hash & (CALLSITE_TABLE_SIZE - 1)]; |
| 450 | cds_hlist_for_each_entry(e, node, head, hlist) { |
| 451 | struct lttng_ust_tracepoint *tp = e->tp; |
| 452 | |
| 453 | if (strncmp(name, tp->name, LTTNG_UST_SYM_NAME_LEN - 1)) |
| 454 | continue; |
| 455 | if (tp_entry) { |
| 456 | set_tracepoint(&tp_entry, tp, |
| 457 | !!tp_entry->refcount); |
| 458 | } else { |
| 459 | disable_tracepoint(tp); |
| 460 | } |
| 461 | } |
| 462 | } |
| 463 | |
| 464 | /** |
| 465 | * tracepoint_update_probe_range - Update a probe range |
| 466 | * @begin: beginning of the range |
| 467 | * @end: end of the range |
| 468 | * |
| 469 | * Updates the probe callback corresponding to a range of tracepoints. |
| 470 | */ |
| 471 | static |
| 472 | void tracepoint_update_probe_range(struct lttng_ust_tracepoint * const *begin, |
| 473 | struct lttng_ust_tracepoint * const *end) |
| 474 | { |
| 475 | struct lttng_ust_tracepoint * const *iter; |
| 476 | struct tracepoint_entry *mark_entry; |
| 477 | |
| 478 | for (iter = begin; iter < end; iter++) { |
| 479 | if (!*iter) |
| 480 | continue; /* skip dummy */ |
| 481 | if (!(*iter)->name) { |
| 482 | disable_tracepoint(*iter); |
| 483 | continue; |
| 484 | } |
| 485 | mark_entry = get_tracepoint((*iter)->name); |
| 486 | if (mark_entry) { |
| 487 | set_tracepoint(&mark_entry, *iter, |
| 488 | !!mark_entry->refcount); |
| 489 | } else { |
| 490 | disable_tracepoint(*iter); |
| 491 | } |
| 492 | } |
| 493 | } |
| 494 | |
| 495 | static void lib_update_tracepoints(struct tracepoint_lib *lib) |
| 496 | { |
| 497 | tracepoint_update_probe_range(lib->tracepoints_start, |
| 498 | lib->tracepoints_start + lib->tracepoints_count); |
| 499 | } |
| 500 | |
| 501 | static void lib_register_callsites(struct tracepoint_lib *lib) |
| 502 | { |
| 503 | struct lttng_ust_tracepoint * const *begin; |
| 504 | struct lttng_ust_tracepoint * const *end; |
| 505 | struct lttng_ust_tracepoint * const *iter; |
| 506 | |
| 507 | begin = lib->tracepoints_start; |
| 508 | end = lib->tracepoints_start + lib->tracepoints_count; |
| 509 | |
| 510 | for (iter = begin; iter < end; iter++) { |
| 511 | if (!*iter) |
| 512 | continue; /* skip dummy */ |
| 513 | if (!(*iter)->name) { |
| 514 | continue; |
| 515 | } |
| 516 | add_callsite(lib, *iter); |
| 517 | } |
| 518 | } |
| 519 | |
| 520 | static void lib_unregister_callsites(struct tracepoint_lib *lib) |
| 521 | { |
| 522 | struct callsite_entry *callsite, *tmp; |
| 523 | |
| 524 | cds_list_for_each_entry_safe(callsite, tmp, &lib->callsites, node) |
| 525 | remove_callsite(callsite); |
| 526 | } |
| 527 | |
| 528 | /* |
| 529 | * Update probes, removing the faulty probes. |
| 530 | */ |
| 531 | static void tracepoint_update_probes(void) |
| 532 | { |
| 533 | struct tracepoint_lib *lib; |
| 534 | |
| 535 | /* tracepoints registered from libraries and executable. */ |
| 536 | cds_list_for_each_entry(lib, &libs, list) |
| 537 | lib_update_tracepoints(lib); |
| 538 | } |
| 539 | |
| 540 | static struct lttng_ust_tracepoint_probe * |
| 541 | tracepoint_add_probe(const char *name, void (*probe)(void), void *data, |
| 542 | const char *signature) |
| 543 | { |
| 544 | struct tracepoint_entry *entry; |
| 545 | struct lttng_ust_tracepoint_probe *old; |
| 546 | |
| 547 | entry = get_tracepoint(name); |
| 548 | if (!entry) { |
| 549 | entry = add_tracepoint(name, signature); |
| 550 | if (IS_ERR(entry)) |
| 551 | return (struct lttng_ust_tracepoint_probe *)entry; |
| 552 | } |
| 553 | old = tracepoint_entry_add_probe(entry, probe, data); |
| 554 | if (IS_ERR(old) && !entry->refcount) |
| 555 | remove_tracepoint(entry); |
| 556 | return old; |
| 557 | } |
| 558 | |
| 559 | static void tracepoint_release_queue_add_old_probes(void *old) |
| 560 | { |
| 561 | release_queue_need_update = 1; |
| 562 | if (old) { |
| 563 | struct tp_probes *tp_probes = caa_container_of(old, |
| 564 | struct tp_probes, probes[0]); |
| 565 | cds_list_add(&tp_probes->u.list, &release_queue); |
| 566 | } |
| 567 | } |
| 568 | |
| 569 | /** |
| 570 | * __tracepoint_probe_register - Connect a probe to a tracepoint |
| 571 | * @name: tracepoint name |
| 572 | * @probe: probe handler |
| 573 | * |
| 574 | * Returns 0 if ok, error value on error. |
| 575 | * The probe address must at least be aligned on the architecture pointer size. |
| 576 | * Called with the tracepoint mutex held. |
| 577 | */ |
| 578 | int __tracepoint_probe_register(const char *name, void (*probe)(void), |
| 579 | void *data, const char *signature) |
| 580 | { |
| 581 | void *old; |
| 582 | int ret = 0; |
| 583 | |
| 584 | DBG("Registering probe to tracepoint %s", name); |
| 585 | |
| 586 | pthread_mutex_lock(&tracepoint_mutex); |
| 587 | old = tracepoint_add_probe(name, probe, data, signature); |
| 588 | if (IS_ERR(old)) { |
| 589 | ret = PTR_ERR(old); |
| 590 | goto end; |
| 591 | } |
| 592 | |
| 593 | tracepoint_sync_callsites(name); |
| 594 | release_probes(old); |
| 595 | end: |
| 596 | pthread_mutex_unlock(&tracepoint_mutex); |
| 597 | return ret; |
| 598 | } |
| 599 | |
| 600 | /* |
| 601 | * Caller needs to invoke __tracepoint_probe_release_queue() after |
| 602 | * calling __tracepoint_probe_register_queue_release() one or multiple |
| 603 | * times to ensure it does not leak memory. |
| 604 | */ |
| 605 | int __tracepoint_probe_register_queue_release(const char *name, |
| 606 | void (*probe)(void), void *data, const char *signature) |
| 607 | { |
| 608 | void *old; |
| 609 | int ret = 0; |
| 610 | |
| 611 | DBG("Registering probe to tracepoint %s. Queuing release.", name); |
| 612 | |
| 613 | pthread_mutex_lock(&tracepoint_mutex); |
| 614 | old = tracepoint_add_probe(name, probe, data, signature); |
| 615 | if (IS_ERR(old)) { |
| 616 | ret = PTR_ERR(old); |
| 617 | goto end; |
| 618 | } |
| 619 | |
| 620 | tracepoint_sync_callsites(name); |
| 621 | tracepoint_release_queue_add_old_probes(old); |
| 622 | end: |
| 623 | pthread_mutex_unlock(&tracepoint_mutex); |
| 624 | return ret; |
| 625 | } |
| 626 | |
| 627 | static void *tracepoint_remove_probe(const char *name, void (*probe)(void), |
| 628 | void *data) |
| 629 | { |
| 630 | struct tracepoint_entry *entry; |
| 631 | void *old; |
| 632 | |
| 633 | entry = get_tracepoint(name); |
| 634 | if (!entry) |
| 635 | return ERR_PTR(-ENOENT); |
| 636 | old = tracepoint_entry_remove_probe(entry, probe, data); |
| 637 | if (IS_ERR(old)) |
| 638 | return old; |
| 639 | if (!entry->refcount) |
| 640 | remove_tracepoint(entry); |
| 641 | return old; |
| 642 | } |
| 643 | |
| 644 | /** |
| 645 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint |
| 646 | * @name: tracepoint name |
| 647 | * @probe: probe function pointer |
| 648 | * @probe: probe data pointer |
| 649 | */ |
| 650 | int __tracepoint_probe_unregister(const char *name, void (*probe)(void), |
| 651 | void *data) |
| 652 | { |
| 653 | void *old; |
| 654 | int ret = 0; |
| 655 | |
| 656 | DBG("Un-registering probe from tracepoint %s", name); |
| 657 | |
| 658 | pthread_mutex_lock(&tracepoint_mutex); |
| 659 | old = tracepoint_remove_probe(name, probe, data); |
| 660 | if (IS_ERR(old)) { |
| 661 | ret = PTR_ERR(old); |
| 662 | goto end; |
| 663 | } |
| 664 | tracepoint_sync_callsites(name); |
| 665 | release_probes(old); |
| 666 | end: |
| 667 | pthread_mutex_unlock(&tracepoint_mutex); |
| 668 | return ret; |
| 669 | } |
| 670 | |
| 671 | /* |
| 672 | * Caller needs to invoke __tracepoint_probe_release_queue() after |
| 673 | * calling __tracepoint_probe_unregister_queue_release() one or multiple |
| 674 | * times to ensure it does not leak memory. |
| 675 | */ |
| 676 | int __tracepoint_probe_unregister_queue_release(const char *name, |
| 677 | void (*probe)(void), void *data) |
| 678 | { |
| 679 | void *old; |
| 680 | int ret = 0; |
| 681 | |
| 682 | DBG("Un-registering probe from tracepoint %s. Queuing release.", name); |
| 683 | |
| 684 | pthread_mutex_lock(&tracepoint_mutex); |
| 685 | old = tracepoint_remove_probe(name, probe, data); |
| 686 | if (IS_ERR(old)) { |
| 687 | ret = PTR_ERR(old); |
| 688 | goto end; |
| 689 | } |
| 690 | tracepoint_sync_callsites(name); |
| 691 | tracepoint_release_queue_add_old_probes(old); |
| 692 | end: |
| 693 | pthread_mutex_unlock(&tracepoint_mutex); |
| 694 | return ret; |
| 695 | } |
| 696 | |
| 697 | void __tracepoint_probe_prune_release_queue(void) |
| 698 | { |
| 699 | CDS_LIST_HEAD(release_probes); |
| 700 | struct tp_probes *pos, *next; |
| 701 | |
| 702 | DBG("Release queue of unregistered tracepoint probes."); |
| 703 | |
| 704 | pthread_mutex_lock(&tracepoint_mutex); |
| 705 | if (!release_queue_need_update) |
| 706 | goto end; |
| 707 | if (!cds_list_empty(&release_queue)) |
| 708 | cds_list_replace_init(&release_queue, &release_probes); |
| 709 | release_queue_need_update = 0; |
| 710 | |
| 711 | /* Wait for grace period between all sync_callsites and free. */ |
| 712 | synchronize_rcu(); |
| 713 | |
| 714 | cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) { |
| 715 | cds_list_del(&pos->u.list); |
| 716 | free(pos); |
| 717 | } |
| 718 | end: |
| 719 | pthread_mutex_unlock(&tracepoint_mutex); |
| 720 | } |
| 721 | |
| 722 | static void tracepoint_add_old_probes(void *old) |
| 723 | { |
| 724 | need_update = 1; |
| 725 | if (old) { |
| 726 | struct tp_probes *tp_probes = caa_container_of(old, |
| 727 | struct tp_probes, probes[0]); |
| 728 | cds_list_add(&tp_probes->u.list, &old_probes); |
| 729 | } |
| 730 | } |
| 731 | |
| 732 | /** |
| 733 | * tracepoint_probe_register_noupdate - register a probe but not connect |
| 734 | * @name: tracepoint name |
| 735 | * @probe: probe handler |
| 736 | * |
| 737 | * caller must call tracepoint_probe_update_all() |
| 738 | */ |
| 739 | int tracepoint_probe_register_noupdate(const char *name, void (*probe)(void), |
| 740 | void *data, const char *signature) |
| 741 | { |
| 742 | void *old; |
| 743 | int ret = 0; |
| 744 | |
| 745 | pthread_mutex_lock(&tracepoint_mutex); |
| 746 | old = tracepoint_add_probe(name, probe, data, signature); |
| 747 | if (IS_ERR(old)) { |
| 748 | ret = PTR_ERR(old); |
| 749 | goto end; |
| 750 | } |
| 751 | tracepoint_add_old_probes(old); |
| 752 | end: |
| 753 | pthread_mutex_unlock(&tracepoint_mutex); |
| 754 | return ret; |
| 755 | } |
| 756 | |
| 757 | /** |
| 758 | * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect |
| 759 | * @name: tracepoint name |
| 760 | * @probe: probe function pointer |
| 761 | * |
| 762 | * caller must call tracepoint_probe_update_all() |
| 763 | * Called with the tracepoint mutex held. |
| 764 | */ |
| 765 | int tracepoint_probe_unregister_noupdate(const char *name, void (*probe)(void), |
| 766 | void *data) |
| 767 | { |
| 768 | void *old; |
| 769 | int ret = 0; |
| 770 | |
| 771 | DBG("Un-registering probe from tracepoint %s", name); |
| 772 | |
| 773 | pthread_mutex_lock(&tracepoint_mutex); |
| 774 | old = tracepoint_remove_probe(name, probe, data); |
| 775 | if (IS_ERR(old)) { |
| 776 | ret = PTR_ERR(old); |
| 777 | goto end; |
| 778 | } |
| 779 | tracepoint_add_old_probes(old); |
| 780 | end: |
| 781 | pthread_mutex_unlock(&tracepoint_mutex); |
| 782 | return ret; |
| 783 | } |
| 784 | |
| 785 | /** |
| 786 | * tracepoint_probe_update_all - update tracepoints |
| 787 | */ |
| 788 | void tracepoint_probe_update_all(void) |
| 789 | { |
| 790 | CDS_LIST_HEAD(release_probes); |
| 791 | struct tp_probes *pos, *next; |
| 792 | |
| 793 | pthread_mutex_lock(&tracepoint_mutex); |
| 794 | if (!need_update) { |
| 795 | goto end; |
| 796 | } |
| 797 | if (!cds_list_empty(&old_probes)) |
| 798 | cds_list_replace_init(&old_probes, &release_probes); |
| 799 | need_update = 0; |
| 800 | |
| 801 | tracepoint_update_probes(); |
| 802 | /* Wait for grace period between update_probes and free. */ |
| 803 | synchronize_rcu(); |
| 804 | cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) { |
| 805 | cds_list_del(&pos->u.list); |
| 806 | free(pos); |
| 807 | } |
| 808 | end: |
| 809 | pthread_mutex_unlock(&tracepoint_mutex); |
| 810 | } |
| 811 | |
| 812 | void tracepoint_set_new_tracepoint_cb(void (*cb)(struct lttng_ust_tracepoint *)) |
| 813 | { |
| 814 | new_tracepoint_cb = cb; |
| 815 | } |
| 816 | |
| 817 | static void new_tracepoints(struct lttng_ust_tracepoint * const *start, |
| 818 | struct lttng_ust_tracepoint * const *end) |
| 819 | { |
| 820 | if (new_tracepoint_cb) { |
| 821 | struct lttng_ust_tracepoint * const *t; |
| 822 | |
| 823 | for (t = start; t < end; t++) { |
| 824 | if (*t) |
| 825 | new_tracepoint_cb(*t); |
| 826 | } |
| 827 | } |
| 828 | } |
| 829 | |
| 830 | int tracepoint_register_lib(struct lttng_ust_tracepoint * const *tracepoints_start, |
| 831 | int tracepoints_count) |
| 832 | { |
| 833 | struct tracepoint_lib *pl, *iter; |
| 834 | |
| 835 | init_tracepoint(); |
| 836 | |
| 837 | pl = (struct tracepoint_lib *) zmalloc(sizeof(struct tracepoint_lib)); |
| 838 | if (!pl) { |
| 839 | PERROR("Unable to register tracepoint lib"); |
| 840 | return -1; |
| 841 | } |
| 842 | pl->tracepoints_start = tracepoints_start; |
| 843 | pl->tracepoints_count = tracepoints_count; |
| 844 | CDS_INIT_LIST_HEAD(&pl->callsites); |
| 845 | |
| 846 | pthread_mutex_lock(&tracepoint_mutex); |
| 847 | /* |
| 848 | * We sort the libs by struct lib pointer address. |
| 849 | */ |
| 850 | cds_list_for_each_entry_reverse(iter, &libs, list) { |
| 851 | BUG_ON(iter == pl); /* Should never be in the list twice */ |
| 852 | if (iter < pl) { |
| 853 | /* We belong to the location right after iter. */ |
| 854 | cds_list_add(&pl->list, &iter->list); |
| 855 | goto lib_added; |
| 856 | } |
| 857 | } |
| 858 | /* We should be added at the head of the list */ |
| 859 | cds_list_add(&pl->list, &libs); |
| 860 | lib_added: |
| 861 | new_tracepoints(tracepoints_start, tracepoints_start + tracepoints_count); |
| 862 | lib_register_callsites(pl); |
| 863 | lib_update_tracepoints(pl); |
| 864 | pthread_mutex_unlock(&tracepoint_mutex); |
| 865 | |
| 866 | DBG("just registered a tracepoints section from %p and having %d tracepoints", |
| 867 | tracepoints_start, tracepoints_count); |
| 868 | if (ust_debug()) { |
| 869 | int i; |
| 870 | |
| 871 | for (i = 0; i < tracepoints_count; i++) { |
| 872 | DBG("registered tracepoint: %s", tracepoints_start[i]->name); |
| 873 | } |
| 874 | } |
| 875 | |
| 876 | return 0; |
| 877 | } |
| 878 | |
| 879 | int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_start) |
| 880 | { |
| 881 | struct tracepoint_lib *lib; |
| 882 | |
| 883 | pthread_mutex_lock(&tracepoint_mutex); |
| 884 | cds_list_for_each_entry(lib, &libs, list) { |
| 885 | if (lib->tracepoints_start != tracepoints_start) |
| 886 | continue; |
| 887 | |
| 888 | cds_list_del(&lib->list); |
| 889 | /* |
| 890 | * Unregistering a callsite also decreases the |
| 891 | * callsite reference count of the corresponding |
| 892 | * tracepoint, and disables the tracepoint if |
| 893 | * the reference count drops to zero. |
| 894 | */ |
| 895 | lib_unregister_callsites(lib); |
| 896 | DBG("just unregistered a tracepoints section from %p", |
| 897 | lib->tracepoints_start); |
| 898 | free(lib); |
| 899 | break; |
| 900 | } |
| 901 | pthread_mutex_unlock(&tracepoint_mutex); |
| 902 | return 0; |
| 903 | } |
| 904 | |
| 905 | /* |
| 906 | * Report in debug message whether the compiler correctly supports weak |
| 907 | * hidden symbols. This test checks that the address associated with two |
| 908 | * weak symbols with hidden visibility is the same when declared within |
| 909 | * two compile units part of the same module. |
| 910 | */ |
| 911 | static void check_weak_hidden(void) |
| 912 | { |
| 913 | DBG("Your compiler treats weak symbols with hidden visibility for integer objects as %s between compile units part of the same module.", |
| 914 | &__tracepoint_test_symbol1 == lttng_ust_tp_check_weak_hidden1() ? |
| 915 | "SAME address" : |
| 916 | "DIFFERENT addresses"); |
| 917 | DBG("Your compiler treats weak symbols with hidden visibility for pointer objects as %s between compile units part of the same module.", |
| 918 | &__tracepoint_test_symbol2 == lttng_ust_tp_check_weak_hidden2() ? |
| 919 | "SAME address" : |
| 920 | "DIFFERENT addresses"); |
| 921 | DBG("Your compiler treats weak symbols with hidden visibility for 24-byte structure objects as %s between compile units part of the same module.", |
| 922 | &__tracepoint_test_symbol3 == lttng_ust_tp_check_weak_hidden3() ? |
| 923 | "SAME address" : |
| 924 | "DIFFERENT addresses"); |
| 925 | } |
| 926 | |
| 927 | void init_tracepoint(void) |
| 928 | { |
| 929 | if (uatomic_xchg(&initialized, 1) == 1) |
| 930 | return; |
| 931 | init_usterr(); |
| 932 | check_weak_hidden(); |
| 933 | } |
| 934 | |
| 935 | void exit_tracepoint(void) |
| 936 | { |
| 937 | initialized = 0; |
| 938 | } |
| 939 | |
| 940 | /* |
| 941 | * Create the wrapper symbols. |
| 942 | */ |
| 943 | #undef tp_rcu_read_lock_bp |
| 944 | #undef tp_rcu_read_unlock_bp |
| 945 | #undef tp_rcu_dereference_bp |
| 946 | |
| 947 | void tp_rcu_read_lock_bp(void) |
| 948 | { |
| 949 | rcu_read_lock_bp(); |
| 950 | } |
| 951 | |
| 952 | void tp_rcu_read_unlock_bp(void) |
| 953 | { |
| 954 | rcu_read_unlock_bp(); |
| 955 | } |
| 956 | |
| 957 | void *tp_rcu_dereference_sym_bp(void *p) |
| 958 | { |
| 959 | return rcu_dereference_bp(p); |
| 960 | } |