| 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 | #include <wrapper/tracepoint.h> |
| 21 | |
| 22 | /* |
| 23 | * Protect the tracepoint table. lttng_tracepoint_mutex nests within |
| 24 | * kernel/tracepoint.c tp_modlist_mutex. kernel/tracepoint.c |
| 25 | * tracepoint_mutex nests within lttng_tracepoint_mutex. |
| 26 | */ |
| 27 | static |
| 28 | DEFINE_MUTEX(lttng_tracepoint_mutex); |
| 29 | |
| 30 | #define TRACEPOINT_HASH_BITS 6 |
| 31 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) |
| 32 | static |
| 33 | struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; |
| 34 | |
| 35 | /* |
| 36 | * The tracepoint entry is the node contained within the hash table. It |
| 37 | * is a mapping from the "string" key to the struct tracepoint pointer. |
| 38 | */ |
| 39 | struct tracepoint_entry { |
| 40 | struct hlist_node hlist; |
| 41 | struct tracepoint *tp; |
| 42 | int refcount; |
| 43 | struct list_head probes; |
| 44 | char name[0]; |
| 45 | }; |
| 46 | |
| 47 | struct lttng_tp_probe { |
| 48 | struct tracepoint_func tp_func; |
| 49 | struct list_head list; |
| 50 | }; |
| 51 | |
| 52 | static |
| 53 | int add_probe(struct tracepoint_entry *e, void *probe, void *data) |
| 54 | { |
| 55 | struct lttng_tp_probe *p; |
| 56 | int found = 0; |
| 57 | |
| 58 | list_for_each_entry(p, &e->probes, list) { |
| 59 | if (p->tp_func.func == probe && p->tp_func.data == data) { |
| 60 | found = 1; |
| 61 | break; |
| 62 | } |
| 63 | } |
| 64 | if (found) |
| 65 | return -EEXIST; |
| 66 | p = kmalloc(sizeof(struct lttng_tp_probe), GFP_KERNEL); |
| 67 | if (!p) |
| 68 | return -ENOMEM; |
| 69 | p->tp_func.func = probe; |
| 70 | p->tp_func.data = data; |
| 71 | list_add(&p->list, &e->probes); |
| 72 | return 0; |
| 73 | } |
| 74 | |
| 75 | static |
| 76 | int remove_probe(struct tracepoint_entry *e, void *probe, void *data) |
| 77 | { |
| 78 | struct lttng_tp_probe *p; |
| 79 | int found = 0; |
| 80 | |
| 81 | list_for_each_entry(p, &e->probes, list) { |
| 82 | if (p->tp_func.func == probe && p->tp_func.data == data) { |
| 83 | found = 1; |
| 84 | break; |
| 85 | } |
| 86 | } |
| 87 | if (found) { |
| 88 | list_del(&p->list); |
| 89 | kfree(p); |
| 90 | return 0; |
| 91 | } else { |
| 92 | WARN_ON(1); |
| 93 | return -ENOENT; |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | /* |
| 98 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. |
| 99 | * Must be called with lttng_tracepoint_mutex held. |
| 100 | * Returns NULL if not present. |
| 101 | */ |
| 102 | static |
| 103 | struct tracepoint_entry *get_tracepoint(const char *name) |
| 104 | { |
| 105 | struct hlist_head *head; |
| 106 | struct tracepoint_entry *e; |
| 107 | u32 hash = jhash(name, strlen(name), 0); |
| 108 | |
| 109 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 110 | lttng_hlist_for_each_entry(e, head, hlist) { |
| 111 | if (!strcmp(name, e->name)) |
| 112 | return e; |
| 113 | } |
| 114 | return NULL; |
| 115 | } |
| 116 | |
| 117 | /* |
| 118 | * Add the tracepoint to the tracepoint hash table. Must be called with |
| 119 | * lttng_tracepoint_mutex held. |
| 120 | */ |
| 121 | static |
| 122 | struct tracepoint_entry *add_tracepoint(const char *name) |
| 123 | { |
| 124 | struct hlist_head *head; |
| 125 | struct tracepoint_entry *e; |
| 126 | size_t name_len = strlen(name) + 1; |
| 127 | u32 hash = jhash(name, name_len - 1, 0); |
| 128 | |
| 129 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; |
| 130 | lttng_hlist_for_each_entry(e, head, hlist) { |
| 131 | if (!strcmp(name, e->name)) { |
| 132 | printk(KERN_NOTICE |
| 133 | "tracepoint %s busy\n", name); |
| 134 | return ERR_PTR(-EEXIST); /* Already there */ |
| 135 | } |
| 136 | } |
| 137 | /* |
| 138 | * Using kmalloc here to allocate a variable length element. Could |
| 139 | * cause some memory fragmentation if overused. |
| 140 | */ |
| 141 | e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL); |
| 142 | if (!e) |
| 143 | return ERR_PTR(-ENOMEM); |
| 144 | memcpy(&e->name[0], name, name_len); |
| 145 | e->tp = NULL; |
| 146 | e->refcount = 0; |
| 147 | INIT_LIST_HEAD(&e->probes); |
| 148 | hlist_add_head(&e->hlist, head); |
| 149 | return e; |
| 150 | } |
| 151 | |
| 152 | /* |
| 153 | * Remove the tracepoint from the tracepoint hash table. Must be called |
| 154 | * with lttng_tracepoint_mutex held. |
| 155 | */ |
| 156 | static |
| 157 | void remove_tracepoint(struct tracepoint_entry *e) |
| 158 | { |
| 159 | hlist_del(&e->hlist); |
| 160 | kfree(e); |
| 161 | } |
| 162 | |
| 163 | int lttng_tracepoint_probe_register(const char *name, void *probe, void *data) |
| 164 | { |
| 165 | struct tracepoint_entry *e; |
| 166 | int ret = 0; |
| 167 | |
| 168 | mutex_lock(<tng_tracepoint_mutex); |
| 169 | e = get_tracepoint(name); |
| 170 | if (!e) { |
| 171 | e = add_tracepoint(name); |
| 172 | if (IS_ERR(e)) { |
| 173 | ret = PTR_ERR(e); |
| 174 | goto end; |
| 175 | } |
| 176 | } |
| 177 | /* add (probe, data) to entry */ |
| 178 | ret = add_probe(e, probe, data); |
| 179 | if (ret) |
| 180 | goto end; |
| 181 | e->refcount++; |
| 182 | if (e->tp) { |
| 183 | ret = tracepoint_probe_register(e->tp, probe, data); |
| 184 | WARN_ON_ONCE(ret); |
| 185 | ret = 0; |
| 186 | } |
| 187 | end: |
| 188 | mutex_unlock(<tng_tracepoint_mutex); |
| 189 | return ret; |
| 190 | } |
| 191 | |
| 192 | int lttng_tracepoint_probe_unregister(const char *name, void *probe, void *data) |
| 193 | { |
| 194 | struct tracepoint_entry *e; |
| 195 | int ret = 0; |
| 196 | |
| 197 | mutex_lock(<tng_tracepoint_mutex); |
| 198 | e = get_tracepoint(name); |
| 199 | if (!e) { |
| 200 | ret = -ENOENT; |
| 201 | goto end; |
| 202 | } |
| 203 | /* remove (probe, data) from entry */ |
| 204 | ret = remove_probe(e, probe, data); |
| 205 | if (ret) |
| 206 | goto end; |
| 207 | if (e->tp) { |
| 208 | ret = tracepoint_probe_unregister(e->tp, probe, data); |
| 209 | WARN_ON_ONCE(ret); |
| 210 | ret = 0; |
| 211 | } |
| 212 | if (!--e->refcount) |
| 213 | remove_tracepoint(e); |
| 214 | end: |
| 215 | mutex_unlock(<tng_tracepoint_mutex); |
| 216 | return ret; |
| 217 | } |
| 218 | |
| 219 | #ifdef CONFIG_MODULES |
| 220 | |
| 221 | static |
| 222 | int lttng_tracepoint_coming(struct tp_module *tp_mod) |
| 223 | { |
| 224 | int i; |
| 225 | |
| 226 | mutex_lock(<tng_tracepoint_mutex); |
| 227 | for (i = 0; i < tp_mod->mod->num_tracepoints; i++) { |
| 228 | struct tracepoint *tp; |
| 229 | struct tracepoint_entry *e; |
| 230 | struct lttng_tp_probe *p; |
| 231 | |
| 232 | tp = lttng_tracepoint_ptr_deref(&tp_mod->mod->tracepoints_ptrs[i]); |
| 233 | e = get_tracepoint(tp->name); |
| 234 | if (!e) { |
| 235 | e = add_tracepoint(tp->name); |
| 236 | if (IS_ERR(e)) { |
| 237 | pr_warn("LTTng: error (%ld) adding tracepoint\n", |
| 238 | PTR_ERR(e)); |
| 239 | continue; |
| 240 | } |
| 241 | } |
| 242 | /* If already enabled, just check consistency */ |
| 243 | if (e->tp) { |
| 244 | WARN_ON(e->tp != tp); |
| 245 | continue; |
| 246 | } |
| 247 | e->tp = tp; |
| 248 | e->refcount++; |
| 249 | /* register each (probe, data) */ |
| 250 | list_for_each_entry(p, &e->probes, list) { |
| 251 | int ret; |
| 252 | |
| 253 | ret = tracepoint_probe_register(e->tp, |
| 254 | p->tp_func.func, p->tp_func.data); |
| 255 | WARN_ON_ONCE(ret); |
| 256 | } |
| 257 | } |
| 258 | mutex_unlock(<tng_tracepoint_mutex); |
| 259 | return NOTIFY_OK; |
| 260 | } |
| 261 | |
| 262 | static |
| 263 | int lttng_tracepoint_going(struct tp_module *tp_mod) |
| 264 | { |
| 265 | int i; |
| 266 | |
| 267 | mutex_lock(<tng_tracepoint_mutex); |
| 268 | for (i = 0; i < tp_mod->mod->num_tracepoints; i++) { |
| 269 | struct tracepoint *tp; |
| 270 | struct tracepoint_entry *e; |
| 271 | struct lttng_tp_probe *p; |
| 272 | |
| 273 | tp = lttng_tracepoint_ptr_deref(&tp_mod->mod->tracepoints_ptrs[i]); |
| 274 | e = get_tracepoint(tp->name); |
| 275 | if (!e || !e->tp) |
| 276 | continue; |
| 277 | /* unregister each (probe, data) */ |
| 278 | list_for_each_entry(p, &e->probes, list) { |
| 279 | int ret; |
| 280 | |
| 281 | ret = tracepoint_probe_unregister(e->tp, |
| 282 | p->tp_func.func, p->tp_func.data); |
| 283 | WARN_ON_ONCE(ret); |
| 284 | } |
| 285 | e->tp = NULL; |
| 286 | if (!--e->refcount) |
| 287 | remove_tracepoint(e); |
| 288 | } |
| 289 | mutex_unlock(<tng_tracepoint_mutex); |
| 290 | return 0; |
| 291 | } |
| 292 | |
| 293 | static |
| 294 | int lttng_tracepoint_notify(struct notifier_block *self, |
| 295 | unsigned long val, void *data) |
| 296 | { |
| 297 | struct tp_module *tp_mod = data; |
| 298 | int ret = 0; |
| 299 | |
| 300 | switch (val) { |
| 301 | case MODULE_STATE_COMING: |
| 302 | ret = lttng_tracepoint_coming(tp_mod); |
| 303 | break; |
| 304 | case MODULE_STATE_GOING: |
| 305 | ret = lttng_tracepoint_going(tp_mod); |
| 306 | break; |
| 307 | default: |
| 308 | break; |
| 309 | } |
| 310 | return ret; |
| 311 | } |
| 312 | |
| 313 | static |
| 314 | struct notifier_block lttng_tracepoint_notifier = { |
| 315 | .notifier_call = lttng_tracepoint_notify, |
| 316 | .priority = 0, |
| 317 | }; |
| 318 | |
| 319 | static |
| 320 | int lttng_tracepoint_module_init(void) |
| 321 | { |
| 322 | return register_tracepoint_module_notifier(<tng_tracepoint_notifier); |
| 323 | } |
| 324 | |
| 325 | static |
| 326 | void lttng_tracepoint_module_exit(void) |
| 327 | { |
| 328 | WARN_ON(unregister_tracepoint_module_notifier(<tng_tracepoint_notifier)); |
| 329 | } |
| 330 | |
| 331 | #else /* #ifdef CONFIG_MODULES */ |
| 332 | |
| 333 | static |
| 334 | int lttng_tracepoint_module_init(void) |
| 335 | { |
| 336 | return 0; |
| 337 | } |
| 338 | |
| 339 | static |
| 340 | void lttng_tracepoint_module_exit(void) |
| 341 | { |
| 342 | } |
| 343 | |
| 344 | #endif /* #else #ifdef CONFIG_MODULES */ |
| 345 | |
| 346 | static |
| 347 | void lttng_kernel_tracepoint_add(struct tracepoint *tp, void *priv) |
| 348 | { |
| 349 | struct tracepoint_entry *e; |
| 350 | struct lttng_tp_probe *p; |
| 351 | int *ret = priv; |
| 352 | |
| 353 | mutex_lock(<tng_tracepoint_mutex); |
| 354 | e = get_tracepoint(tp->name); |
| 355 | if (!e) { |
| 356 | e = add_tracepoint(tp->name); |
| 357 | if (IS_ERR(e)) { |
| 358 | pr_warn("LTTng: error (%ld) adding tracepoint\n", |
| 359 | PTR_ERR(e)); |
| 360 | *ret = (int) PTR_ERR(e); |
| 361 | goto end; |
| 362 | } |
| 363 | } |
| 364 | /* If already enabled, just check consistency */ |
| 365 | if (e->tp) { |
| 366 | WARN_ON(e->tp != tp); |
| 367 | goto end; |
| 368 | } |
| 369 | e->tp = tp; |
| 370 | e->refcount++; |
| 371 | /* register each (probe, data) */ |
| 372 | list_for_each_entry(p, &e->probes, list) { |
| 373 | int ret; |
| 374 | |
| 375 | ret = tracepoint_probe_register(e->tp, |
| 376 | p->tp_func.func, p->tp_func.data); |
| 377 | WARN_ON_ONCE(ret); |
| 378 | } |
| 379 | end: |
| 380 | mutex_unlock(<tng_tracepoint_mutex); |
| 381 | } |
| 382 | |
| 383 | static |
| 384 | void lttng_kernel_tracepoint_remove(struct tracepoint *tp, void *priv) |
| 385 | { |
| 386 | struct tracepoint_entry *e; |
| 387 | int *ret = priv; |
| 388 | |
| 389 | mutex_lock(<tng_tracepoint_mutex); |
| 390 | e = get_tracepoint(tp->name); |
| 391 | if (!e || e->refcount != 1 || !list_empty(&e->probes)) { |
| 392 | *ret = -EINVAL; |
| 393 | goto end; |
| 394 | } |
| 395 | remove_tracepoint(e); |
| 396 | end: |
| 397 | mutex_unlock(<tng_tracepoint_mutex); |
| 398 | } |
| 399 | |
| 400 | int __init lttng_tracepoint_init(void) |
| 401 | { |
| 402 | int ret = 0; |
| 403 | |
| 404 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_add, &ret); |
| 405 | if (ret) |
| 406 | goto error; |
| 407 | ret = lttng_tracepoint_module_init(); |
| 408 | if (ret) |
| 409 | goto error_module; |
| 410 | return 0; |
| 411 | |
| 412 | error_module: |
| 413 | { |
| 414 | int error_ret = 0; |
| 415 | |
| 416 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, |
| 417 | &error_ret); |
| 418 | WARN_ON(error_ret); |
| 419 | } |
| 420 | error: |
| 421 | return ret; |
| 422 | } |
| 423 | |
| 424 | void lttng_tracepoint_exit(void) |
| 425 | { |
| 426 | int i, ret = 0; |
| 427 | |
| 428 | lttng_tracepoint_module_exit(); |
| 429 | for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, &ret); |
| 430 | WARN_ON(ret); |
| 431 | mutex_lock(<tng_tracepoint_mutex); |
| 432 | for (i = 0; i < TRACEPOINT_TABLE_SIZE; i++) { |
| 433 | struct hlist_head *head = &tracepoint_table[i]; |
| 434 | |
| 435 | /* All tracepoints should be removed */ |
| 436 | WARN_ON(!hlist_empty(head)); |
| 437 | } |
| 438 | mutex_unlock(<tng_tracepoint_mutex); |
| 439 | } |