| 1 | /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1) |
| 2 | * |
| 3 | * lttng-tracepoint.c |
| 4 | * |
| 5 | * LTTng adaptation layer for Linux kernel 3.15+ tracepoints. |
| 6 | * |
| 7 | * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 8 | */ |
| 9 | |
| 10 | #include <linux/mutex.h> |
| 11 | #include <linux/err.h> |
| 12 | #include <linux/notifier.h> |
| 13 | #include <linux/tracepoint.h> |
| 14 | #include <linux/slab.h> |
| 15 | #include <linux/jhash.h> |
| 16 | #include <linux/module.h> |
| 17 | |
| 18 | #include <lttng-tracepoint.h> |
| 19 | #include <wrapper/list.h> |
| 20 | |
| 21 | /* |
| 22 | * Protect the tracepoint table. lttng_tracepoint_mutex nests within |
| 23 | * kernel/tracepoint.c tp_modlist_mutex. kernel/tracepoint.c |
| 24 | * tracepoint_mutex nests within lttng_tracepoint_mutex. |
| 25 | */ |
| 26 | static |
| 27 | DEFINE_MUTEX(lttng_tracepoint_mutex); |
| 28 | |
| 29 | #define TRACEPOINT_HASH_BITS 6 |
| 30 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) |
| 31 | static |
| 32 | struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; |
| 33 | |
| 34 | /* |
| 35 | * The tracepoint entry is the node contained within the hash table. It |
| 36 | * is a mapping from the "string" key to the struct tracepoint pointer. |
| 37 | */ |
| 38 | struct tracepoint_entry { |
| 39 | struct hlist_node hlist; |
| 40 | struct tracepoint *tp; |
| 41 | int refcount; |
| 42 | struct list_head probes; |
| 43 | char name[0]; |
| 44 | }; |
| 45 | |
| 46 | struct lttng_tp_probe { |
| 47 | struct tracepoint_func tp_func; |
| 48 | struct list_head list; |
| 49 | }; |
| 50 | |
| 51 | static |
| 52 | int add_probe(struct tracepoint_entry *e, void *probe, void *data) |
| 53 | { |
| 54 | struct lttng_tp_probe *p; |
| 55 | int found = 0; |
| 56 | |
| 57 | list_for_each_entry(p, &e->probes, list) { |
| 58 | if (p->tp_func.func == probe && p->tp_func.data == data) { |
| 59 | found = 1; |
| 60 | break; |
| 61 | } |
| 62 | } |
| 63 | if (found) |
| 64 | return -EEXIST; |
| 65 | p = kmalloc(sizeof(struct lttng_tp_probe), GFP_KERNEL); |
| 66 | if (!p) |
| 67 | return -ENOMEM; |
| 68 | p->tp_func.func = probe; |
| 69 | p->tp_func.data = data; |
| 70 | list_add(&p->list, &e->probes); |
| 71 | return 0; |
| 72 | } |
| 73 | |
| 74 | static |
| 75 | int remove_probe(struct tracepoint_entry *e, void *probe, void *data) |
| 76 | { |
| 77 | struct lttng_tp_probe *p; |
| 78 | int found = 0; |
| 79 | |
| 80 | list_for_each_entry(p, &e->probes, list) { |
| 81 | if (p->tp_func.func == probe && p->tp_func.data == data) { |
| 82 | found = 1; |
| 83 | break; |
| 84 | } |
| 85 | } |
| 86 | if (found) { |
| 87 | list_del(&p->list); |
| 88 | kfree(p); |
| 89 | return 0; |
| 90 | } else { |
| 91 | WARN_ON(1); |
| 92 | return -ENOENT; |
| 93 | } |
| 94 | } |
| 95 | |
| 96 | /* |
| 97 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. |
| 98 | * Must be called with lttng_tracepoint_mutex held. |
| 99 | * Returns NULL if not present. |
| 100 | */ |
| 101 | static |
| 102 | struct tracepoint_entry *get_tracepoint(const char *name) |
| 103 | { |
| 104 | struct hlist_head *head; |
| 105 | struct tracepoint_entry *e; |
| 106 | u32 hash = jhash(name, strlen(name), 0); |
| 107 | |
| 108 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 109 | lttng_hlist_for_each_entry(e, head, hlist) { |
| 110 | if (!strcmp(name, e->name)) |
| 111 | return e; |
| 112 | } |
| 113 | return NULL; |
| 114 | } |
| 115 | |
| 116 | /* |
| 117 | * Add the tracepoint to the tracepoint hash table. Must be called with |
| 118 | * lttng_tracepoint_mutex held. |
| 119 | */ |
| 120 | static |
| 121 | struct tracepoint_entry *add_tracepoint(const char *name) |
| 122 | { |
| 123 | struct hlist_head *head; |
| 124 | struct tracepoint_entry *e; |
| 125 | size_t name_len = strlen(name) + 1; |
| 126 | u32 hash = jhash(name, name_len - 1, 0); |
| 127 | |
| 128 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 129 | lttng_hlist_for_each_entry(e, head, hlist) { |
| 130 | if (!strcmp(name, e->name)) { |
| 131 | printk(KERN_NOTICE |
| 132 | "tracepoint %s busy\n", name); |
| 133 | return ERR_PTR(-EEXIST); /* Already there */ |
| 134 | } |
| 135 | } |
| 136 | /* |
| 137 | * Using kmalloc here to allocate a variable length element. Could |
| 138 | * cause some memory fragmentation if overused. |
| 139 | */ |
| 140 | e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL); |
| 141 | if (!e) |
| 142 | return ERR_PTR(-ENOMEM); |
| 143 | memcpy(&e->name[0], name, name_len); |
| 144 | e->tp = NULL; |
| 145 | e->refcount = 0; |
| 146 | INIT_LIST_HEAD(&e->probes); |
| 147 | hlist_add_head(&e->hlist, head); |
| 148 | return e; |
| 149 | } |
| 150 | |
| 151 | /* |
| 152 | * Remove the tracepoint from the tracepoint hash table. Must be called |
| 153 | * with lttng_tracepoint_mutex held. |
| 154 | */ |
| 155 | static |
| 156 | void remove_tracepoint(struct tracepoint_entry *e) |
| 157 | { |
| 158 | hlist_del(&e->hlist); |
| 159 | kfree(e); |
| 160 | } |
| 161 | |
| 162 | int lttng_tracepoint_probe_register(const char *name, void *probe, void *data) |
| 163 | { |
| 164 | struct tracepoint_entry *e; |
| 165 | int ret = 0; |
| 166 | |
| 167 | mutex_lock(<tng_tracepoint_mutex); |
| 168 | e = get_tracepoint(name); |
| 169 | if (!e) { |
| 170 | e = add_tracepoint(name); |
| 171 | if (IS_ERR(e)) { |
| 172 | ret = PTR_ERR(e); |
| 173 | goto end; |
| 174 | } |
| 175 | } |
| 176 | /* add (probe, data) to entry */ |
| 177 | ret = add_probe(e, probe, data); |
| 178 | if (ret) |
| 179 | goto end; |
| 180 | e->refcount++; |
| 181 | if (e->tp) { |
| 182 | ret = tracepoint_probe_register(e->tp, probe, data); |
| 183 | WARN_ON_ONCE(ret); |
| 184 | ret = 0; |
| 185 | } |
| 186 | end: |
| 187 | mutex_unlock(<tng_tracepoint_mutex); |
| 188 | return ret; |
| 189 | } |
| 190 | |
| 191 | int lttng_tracepoint_probe_unregister(const char *name, void *probe, void *data) |
| 192 | { |
| 193 | struct tracepoint_entry *e; |
| 194 | int ret = 0; |
| 195 | |
| 196 | mutex_lock(<tng_tracepoint_mutex); |
| 197 | e = get_tracepoint(name); |
| 198 | if (!e) { |
| 199 | ret = -ENOENT; |
| 200 | goto end; |
| 201 | } |
| 202 | /* remove (probe, data) from entry */ |
| 203 | ret = remove_probe(e, probe, data); |
| 204 | if (ret) |
| 205 | goto end; |
| 206 | if (e->tp) { |
| 207 | ret = tracepoint_probe_unregister(e->tp, probe, data); |
| 208 | WARN_ON_ONCE(ret); |
| 209 | ret = 0; |
| 210 | } |
| 211 | if (!--e->refcount) |
| 212 | remove_tracepoint(e); |
| 213 | end: |
| 214 | mutex_unlock(<tng_tracepoint_mutex); |
| 215 | return ret; |
| 216 | } |
| 217 | |
| 218 | #ifdef CONFIG_MODULES |
| 219 | |
| 220 | static |
| 221 | int lttng_tracepoint_coming(struct tp_module *tp_mod) |
| 222 | { |
| 223 | int i; |
| 224 | |
| 225 | mutex_lock(<tng_tracepoint_mutex); |
| 226 | for (i = 0; i < tp_mod->mod->num_tracepoints; i++) { |
| 227 | struct tracepoint *tp; |
| 228 | struct tracepoint_entry *e; |
| 229 | struct lttng_tp_probe *p; |
| 230 | |
| 231 | tp = tp_mod->mod->tracepoints_ptrs[i]; |
| 232 | e = get_tracepoint(tp->name); |
| 233 | if (!e) { |
| 234 | e = add_tracepoint(tp->name); |
| 235 | if (IS_ERR(e)) { |
| 236 | pr_warn("LTTng: error (%ld) adding tracepoint\n", |
| 237 | PTR_ERR(e)); |
| 238 | continue; |
| 239 | } |
| 240 | } |
| 241 | /* If already enabled, just check consistency */ |
| 242 | if (e->tp) { |
| 243 | WARN_ON(e->tp != tp); |
| 244 | continue; |
| 245 | } |
| 246 | e->tp = tp; |
| 247 | e->refcount++; |
| 248 | /* register each (probe, data) */ |
| 249 | list_for_each_entry(p, &e->probes, list) { |
| 250 | int ret; |
| 251 | |
| 252 | ret = tracepoint_probe_register(e->tp, |
| 253 | p->tp_func.func, p->tp_func.data); |
| 254 | WARN_ON_ONCE(ret); |
| 255 | } |
| 256 | } |
| 257 | mutex_unlock(<tng_tracepoint_mutex); |
| 258 | return 0; |
| 259 | } |
| 260 | |
| 261 | static |
| 262 | int lttng_tracepoint_going(struct tp_module *tp_mod) |
| 263 | { |
| 264 | int i; |
| 265 | |
| 266 | mutex_lock(<tng_tracepoint_mutex); |
| 267 | for (i = 0; i < tp_mod->mod->num_tracepoints; i++) { |
| 268 | struct tracepoint *tp; |
| 269 | struct tracepoint_entry *e; |
| 270 | struct lttng_tp_probe *p; |
| 271 | |
| 272 | tp = tp_mod->mod->tracepoints_ptrs[i]; |
| 273 | e = get_tracepoint(tp->name); |
| 274 | if (!e || !e->tp) |
| 275 | continue; |
| 276 | /* unregister each (probe, data) */ |
| 277 | list_for_each_entry(p, &e->probes, list) { |
| 278 | int ret; |
| 279 | |
| 280 | ret = tracepoint_probe_unregister(e->tp, |
| 281 | p->tp_func.func, p->tp_func.data); |
| 282 | WARN_ON_ONCE(ret); |
| 283 | } |
| 284 | e->tp = NULL; |
| 285 | if (!--e->refcount) |
| 286 | remove_tracepoint(e); |
| 287 | } |
| 288 | mutex_unlock(<tng_tracepoint_mutex); |
| 289 | return 0; |
| 290 | } |
| 291 | |
| 292 | static |
| 293 | int lttng_tracepoint_notify(struct notifier_block *self, |
| 294 | unsigned long val, void *data) |
| 295 | { |
| 296 | struct tp_module *tp_mod = data; |
| 297 | int ret = 0; |
| 298 | |
| 299 | switch (val) { |
| 300 | case MODULE_STATE_COMING: |
| 301 | ret = lttng_tracepoint_coming(tp_mod); |
| 302 | break; |
| 303 | case MODULE_STATE_GOING: |
| 304 | ret = lttng_tracepoint_going(tp_mod); |
| 305 | break; |
| 306 | default: |
| 307 | break; |
| 308 | } |
| 309 | return ret; |
| 310 | } |
| 311 | |
| 312 | static |
| 313 | struct notifier_block lttng_tracepoint_notifier = { |
| 314 | .notifier_call = lttng_tracepoint_notify, |
| 315 | .priority = 0, |
| 316 | }; |
| 317 | |
| 318 | static |
| 319 | int lttng_tracepoint_module_init(void) |
| 320 | { |
| 321 | return register_tracepoint_module_notifier(<tng_tracepoint_notifier); |
| 322 | } |
| 323 | |
| 324 | static |
| 325 | void lttng_tracepoint_module_exit(void) |
| 326 | { |
| 327 | WARN_ON(unregister_tracepoint_module_notifier(<tng_tracepoint_notifier)); |
| 328 | } |
| 329 | |
| 330 | #else /* #ifdef CONFIG_MODULES */ |
| 331 | |
| 332 | static |
| 333 | int lttng_tracepoint_module_init(void) |
| 334 | { |
| 335 | return 0; |
| 336 | } |
| 337 | |
| 338 | static |
| 339 | void lttng_tracepoint_module_exit(void) |
| 340 | { |
| 341 | } |
| 342 | |
| 343 | #endif /* #else #ifdef CONFIG_MODULES */ |
| 344 | |
| 345 | static |
| 346 | void lttng_kernel_tracepoint_add(struct tracepoint *tp, void *priv) |
| 347 | { |
| 348 | struct tracepoint_entry *e; |
| 349 | struct lttng_tp_probe *p; |
| 350 | int *ret = priv; |
| 351 | |
| 352 | mutex_lock(<tng_tracepoint_mutex); |
| 353 | e = get_tracepoint(tp->name); |
| 354 | if (!e) { |
| 355 | e = add_tracepoint(tp->name); |
| 356 | if (IS_ERR(e)) { |
| 357 | pr_warn("LTTng: error (%ld) adding tracepoint\n", |
| 358 | PTR_ERR(e)); |
| 359 | *ret = (int) PTR_ERR(e); |
| 360 | goto end; |
| 361 | } |
| 362 | } |
| 363 | /* If already enabled, just check consistency */ |
| 364 | if (e->tp) { |
| 365 | WARN_ON(e->tp != tp); |
| 366 | goto end; |
| 367 | } |
| 368 | e->tp = tp; |
| 369 | e->refcount++; |
| 370 | /* register each (probe, data) */ |
| 371 | list_for_each_entry(p, &e->probes, list) { |
| 372 | int ret; |
| 373 | |
| 374 | ret = tracepoint_probe_register(e->tp, |
| 375 | p->tp_func.func, p->tp_func.data); |
| 376 | WARN_ON_ONCE(ret); |
| 377 | } |
| 378 | end: |
| 379 | mutex_unlock(<tng_tracepoint_mutex); |
| 380 | } |
| 381 | |
| 382 | static |
| 383 | void lttng_kernel_tracepoint_remove(struct tracepoint *tp, void *priv) |
| 384 | { |
| 385 | struct tracepoint_entry *e; |
| 386 | int *ret = priv; |
| 387 | |
| 388 | mutex_lock(<tng_tracepoint_mutex); |
| 389 | e = get_tracepoint(tp->name); |
| 390 | if (!e || e->refcount != 1 || !list_empty(&e->probes)) { |
| 391 | *ret = -EINVAL; |
| 392 | goto end; |
| 393 | } |
| 394 | remove_tracepoint(e); |
| 395 | end: |
| 396 | mutex_unlock(<tng_tracepoint_mutex); |
| 397 | } |
| 398 | |
| 399 | int __init lttng_tracepoint_init(void) |
| 400 | { |
| 401 | int ret = 0; |
| 402 | |
| 403 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_add, &ret); |
| 404 | if (ret) |
| 405 | goto error; |
| 406 | ret = lttng_tracepoint_module_init(); |
| 407 | if (ret) |
| 408 | goto error_module; |
| 409 | return 0; |
| 410 | |
| 411 | error_module: |
| 412 | { |
| 413 | int error_ret = 0; |
| 414 | |
| 415 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, |
| 416 | &error_ret); |
| 417 | WARN_ON(error_ret); |
| 418 | } |
| 419 | error: |
| 420 | return ret; |
| 421 | } |
| 422 | |
| 423 | void lttng_tracepoint_exit(void) |
| 424 | { |
| 425 | int i, ret = 0; |
| 426 | |
| 427 | lttng_tracepoint_module_exit(); |
| 428 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, &ret); |
| 429 | WARN_ON(ret); |
| 430 | mutex_lock(<tng_tracepoint_mutex); |
| 431 | for (i = 0; i < TRACEPOINT_TABLE_SIZE; i++) { |
| 432 | struct hlist_head *head = &tracepoint_table[i]; |
| 433 | |
| 434 | /* All tracepoints should be removed */ |
| 435 | WARN_ON(!hlist_empty(head)); |
| 436 | } |
| 437 | mutex_unlock(<tng_tracepoint_mutex); |
| 438 | } |