linux/kernel/tracepoint.c
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   1/*
   2 * Copyright (C) 2008 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
  30extern struct tracepoint * const __start___tracepoints_ptrs[];
  31extern struct tracepoint * const __stop___tracepoints_ptrs[];
  32
  33/* Set to 1 to enable tracepoint debug output */
  34static const int tracepoint_debug;
  35
  36/*
  37 * Tracepoints mutex protects the builtin and module tracepoints and the hash
  38 * table, as well as the local module list.
  39 */
  40static DEFINE_MUTEX(tracepoints_mutex);
  41
  42#ifdef CONFIG_MODULES
  43/* Local list of struct module */
  44static LIST_HEAD(tracepoint_module_list);
  45#endif /* CONFIG_MODULES */
  46
  47/*
  48 * Tracepoint hash table, containing the active tracepoints.
  49 * Protected by tracepoints_mutex.
  50 */
  51#define TRACEPOINT_HASH_BITS 6
  52#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
  53static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
  54
  55/*
  56 * Note about RCU :
  57 * It is used to delay the free of multiple probes array until a quiescent
  58 * state is reached.
  59 * Tracepoint entries modifications are protected by the tracepoints_mutex.
  60 */
  61struct tracepoint_entry {
  62        struct hlist_node hlist;
  63        struct tracepoint_func *funcs;
  64        int refcount;   /* Number of times armed. 0 if disarmed. */
  65        char name[0];
  66};
  67
  68struct tp_probes {
  69        union {
  70                struct rcu_head rcu;
  71                struct list_head list;
  72        } u;
  73        struct tracepoint_func probes[0];
  74};
  75
  76static inline void *allocate_probes(int count)
  77{
  78        struct tp_probes *p  = kmalloc(count * sizeof(struct tracepoint_func)
  79                        + sizeof(struct tp_probes), GFP_KERNEL);
  80        return p == NULL ? NULL : p->probes;
  81}
  82
  83static void rcu_free_old_probes(struct rcu_head *head)
  84{
  85        kfree(container_of(head, struct tp_probes, u.rcu));
  86}
  87
  88static inline void release_probes(struct tracepoint_func *old)
  89{
  90        if (old) {
  91                struct tp_probes *tp_probes = container_of(old,
  92                        struct tp_probes, probes[0]);
  93                call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
  94        }
  95}
  96
  97static void debug_print_probes(struct tracepoint_entry *entry)
  98{
  99        int i;
 100
 101        if (!tracepoint_debug || !entry->funcs)
 102                return;
 103
 104        for (i = 0; entry->funcs[i].func; i++)
 105                printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
 106}
 107
 108static struct tracepoint_func *
 109tracepoint_entry_add_probe(struct tracepoint_entry *entry,
 110                           void *probe, void *data)
 111{
 112        int nr_probes = 0;
 113        struct tracepoint_func *old, *new;
 114
 115        WARN_ON(!probe);
 116
 117        debug_print_probes(entry);
 118        old = entry->funcs;
 119        if (old) {
 120                /* (N -> N+1), (N != 0, 1) probes */
 121                for (nr_probes = 0; old[nr_probes].func; nr_probes++)
 122                        if (old[nr_probes].func == probe &&
 123                            old[nr_probes].data == data)
 124                                return ERR_PTR(-EEXIST);
 125        }
 126        /* + 2 : one for new probe, one for NULL func */
 127        new = allocate_probes(nr_probes + 2);
 128        if (new == NULL)
 129                return ERR_PTR(-ENOMEM);
 130        if (old)
 131                memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
 132        new[nr_probes].func = probe;
 133        new[nr_probes].data = data;
 134        new[nr_probes + 1].func = NULL;
 135        entry->refcount = nr_probes + 1;
 136        entry->funcs = new;
 137        debug_print_probes(entry);
 138        return old;
 139}
 140
 141static void *
 142tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
 143                              void *probe, void *data)
 144{
 145        int nr_probes = 0, nr_del = 0, i;
 146        struct tracepoint_func *old, *new;
 147
 148        old = entry->funcs;
 149
 150        if (!old)
 151                return ERR_PTR(-ENOENT);
 152
 153        debug_print_probes(entry);
 154        /* (N -> M), (N > 1, M >= 0) probes */
 155        for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
 156                if (!probe ||
 157                    (old[nr_probes].func == probe &&
 158                     old[nr_probes].data == data))
 159                        nr_del++;
 160        }
 161
 162        if (nr_probes - nr_del == 0) {
 163                /* N -> 0, (N > 1) */
 164                entry->funcs = NULL;
 165                entry->refcount = 0;
 166                debug_print_probes(entry);
 167                return old;
 168        } else {
 169                int j = 0;
 170                /* N -> M, (N > 1, M > 0) */
 171                /* + 1 for NULL */
 172                new = allocate_probes(nr_probes - nr_del + 1);
 173                if (new == NULL)
 174                        return ERR_PTR(-ENOMEM);
 175                for (i = 0; old[i].func; i++)
 176                        if (probe &&
 177                            (old[i].func != probe || old[i].data != data))
 178                                new[j++] = old[i];
 179                new[nr_probes - nr_del].func = NULL;
 180                entry->refcount = nr_probes - nr_del;
 181                entry->funcs = new;
 182        }
 183        debug_print_probes(entry);
 184        return old;
 185}
 186
 187/*
 188 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
 189 * Must be called with tracepoints_mutex held.
 190 * Returns NULL if not present.
 191 */
 192static struct tracepoint_entry *get_tracepoint(const char *name)
 193{
 194        struct hlist_head *head;
 195        struct tracepoint_entry *e;
 196        u32 hash = jhash(name, strlen(name), 0);
 197
 198        head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
 199        hlist_for_each_entry(e, head, hlist) {
 200                if (!strcmp(name, e->name))
 201                        return e;
 202        }
 203        return NULL;
 204}
 205
 206/*
 207 * Add the tracepoint to the tracepoint hash table. Must be called with
 208 * tracepoints_mutex held.
 209 */
 210static struct tracepoint_entry *add_tracepoint(const char *name)
 211{
 212        struct hlist_head *head;
 213        struct tracepoint_entry *e;
 214        size_t name_len = strlen(name) + 1;
 215        u32 hash = jhash(name, name_len-1, 0);
 216
 217        head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
 218        hlist_for_each_entry(e, head, hlist) {
 219                if (!strcmp(name, e->name)) {
 220                        printk(KERN_NOTICE
 221                                "tracepoint %s busy\n", name);
 222                        return ERR_PTR(-EEXIST);        /* Already there */
 223                }
 224        }
 225        /*
 226         * Using kmalloc here to allocate a variable length element. Could
 227         * cause some memory fragmentation if overused.
 228         */
 229        e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
 230        if (!e)
 231                return ERR_PTR(-ENOMEM);
 232        memcpy(&e->name[0], name, name_len);
 233        e->funcs = NULL;
 234        e->refcount = 0;
 235        hlist_add_head(&e->hlist, head);
 236        return e;
 237}
 238
 239/*
 240 * Remove the tracepoint from the tracepoint hash table. Must be called with
 241 * mutex_lock held.
 242 */
 243static inline void remove_tracepoint(struct tracepoint_entry *e)
 244{
 245        hlist_del(&e->hlist);
 246        kfree(e);
 247}
 248
 249/*
 250 * Sets the probe callback corresponding to one tracepoint.
 251 */
 252static void set_tracepoint(struct tracepoint_entry **entry,
 253        struct tracepoint *elem, int active)
 254{
 255        WARN_ON(strcmp((*entry)->name, elem->name) != 0);
 256
 257        if (elem->regfunc && !static_key_enabled(&elem->key) && active)
 258                elem->regfunc();
 259        else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
 260                elem->unregfunc();
 261
 262        /*
 263         * rcu_assign_pointer has a smp_wmb() which makes sure that the new
 264         * probe callbacks array is consistent before setting a pointer to it.
 265         * This array is referenced by __DO_TRACE from
 266         * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
 267         * is used.
 268         */
 269        rcu_assign_pointer(elem->funcs, (*entry)->funcs);
 270        if (active && !static_key_enabled(&elem->key))
 271                static_key_slow_inc(&elem->key);
 272        else if (!active && static_key_enabled(&elem->key))
 273                static_key_slow_dec(&elem->key);
 274}
 275
 276/*
 277 * Disable a tracepoint and its probe callback.
 278 * Note: only waiting an RCU period after setting elem->call to the empty
 279 * function insures that the original callback is not used anymore. This insured
 280 * by preempt_disable around the call site.
 281 */
 282static void disable_tracepoint(struct tracepoint *elem)
 283{
 284        if (elem->unregfunc && static_key_enabled(&elem->key))
 285                elem->unregfunc();
 286
 287        if (static_key_enabled(&elem->key))
 288                static_key_slow_dec(&elem->key);
 289        rcu_assign_pointer(elem->funcs, NULL);
 290}
 291
 292/**
 293 * tracepoint_update_probe_range - Update a probe range
 294 * @begin: beginning of the range
 295 * @end: end of the range
 296 *
 297 * Updates the probe callback corresponding to a range of tracepoints.
 298 * Called with tracepoints_mutex held.
 299 */
 300static void tracepoint_update_probe_range(struct tracepoint * const *begin,
 301                                          struct tracepoint * const *end)
 302{
 303        struct tracepoint * const *iter;
 304        struct tracepoint_entry *mark_entry;
 305
 306        if (!begin)
 307                return;
 308
 309        for (iter = begin; iter < end; iter++) {
 310                mark_entry = get_tracepoint((*iter)->name);
 311                if (mark_entry) {
 312                        set_tracepoint(&mark_entry, *iter,
 313                                        !!mark_entry->refcount);
 314                } else {
 315                        disable_tracepoint(*iter);
 316                }
 317        }
 318}
 319
 320#ifdef CONFIG_MODULES
 321void module_update_tracepoints(void)
 322{
 323        struct tp_module *tp_mod;
 324
 325        list_for_each_entry(tp_mod, &tracepoint_module_list, list)
 326                tracepoint_update_probe_range(tp_mod->tracepoints_ptrs,
 327                        tp_mod->tracepoints_ptrs + tp_mod->num_tracepoints);
 328}
 329#else /* CONFIG_MODULES */
 330void module_update_tracepoints(void)
 331{
 332}
 333#endif /* CONFIG_MODULES */
 334
 335
 336/*
 337 * Update probes, removing the faulty probes.
 338 * Called with tracepoints_mutex held.
 339 */
 340static void tracepoint_update_probes(void)
 341{
 342        /* Core kernel tracepoints */
 343        tracepoint_update_probe_range(__start___tracepoints_ptrs,
 344                __stop___tracepoints_ptrs);
 345        /* tracepoints in modules. */
 346        module_update_tracepoints();
 347}
 348
 349static struct tracepoint_func *
 350tracepoint_add_probe(const char *name, void *probe, void *data)
 351{
 352        struct tracepoint_entry *entry;
 353        struct tracepoint_func *old;
 354
 355        entry = get_tracepoint(name);
 356        if (!entry) {
 357                entry = add_tracepoint(name);
 358                if (IS_ERR(entry))
 359                        return (struct tracepoint_func *)entry;
 360        }
 361        old = tracepoint_entry_add_probe(entry, probe, data);
 362        if (IS_ERR(old) && !entry->refcount)
 363                remove_tracepoint(entry);
 364        return old;
 365}
 366
 367/**
 368 * tracepoint_probe_register -  Connect a probe to a tracepoint
 369 * @name: tracepoint name
 370 * @probe: probe handler
 371 *
 372 * Returns 0 if ok, error value on error.
 373 * The probe address must at least be aligned on the architecture pointer size.
 374 */
 375int tracepoint_probe_register(const char *name, void *probe, void *data)
 376{
 377        struct tracepoint_func *old;
 378
 379        mutex_lock(&tracepoints_mutex);
 380        old = tracepoint_add_probe(name, probe, data);
 381        if (IS_ERR(old)) {
 382                mutex_unlock(&tracepoints_mutex);
 383                return PTR_ERR(old);
 384        }
 385        tracepoint_update_probes();             /* may update entry */
 386        mutex_unlock(&tracepoints_mutex);
 387        release_probes(old);
 388        return 0;
 389}
 390EXPORT_SYMBOL_GPL(tracepoint_probe_register);
 391
 392static struct tracepoint_func *
 393tracepoint_remove_probe(const char *name, void *probe, void *data)
 394{
 395        struct tracepoint_entry *entry;
 396        struct tracepoint_func *old;
 397
 398        entry = get_tracepoint(name);
 399        if (!entry)
 400                return ERR_PTR(-ENOENT);
 401        old = tracepoint_entry_remove_probe(entry, probe, data);
 402        if (IS_ERR(old))
 403                return old;
 404        if (!entry->refcount)
 405                remove_tracepoint(entry);
 406        return old;
 407}
 408
 409/**
 410 * tracepoint_probe_unregister -  Disconnect a probe from a tracepoint
 411 * @name: tracepoint name
 412 * @probe: probe function pointer
 413 *
 414 * We do not need to call a synchronize_sched to make sure the probes have
 415 * finished running before doing a module unload, because the module unload
 416 * itself uses stop_machine(), which insures that every preempt disabled section
 417 * have finished.
 418 */
 419int tracepoint_probe_unregister(const char *name, void *probe, void *data)
 420{
 421        struct tracepoint_func *old;
 422
 423        mutex_lock(&tracepoints_mutex);
 424        old = tracepoint_remove_probe(name, probe, data);
 425        if (IS_ERR(old)) {
 426                mutex_unlock(&tracepoints_mutex);
 427                return PTR_ERR(old);
 428        }
 429        tracepoint_update_probes();             /* may update entry */
 430        mutex_unlock(&tracepoints_mutex);
 431        release_probes(old);
 432        return 0;
 433}
 434EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
 435
 436static LIST_HEAD(old_probes);
 437static int need_update;
 438
 439static void tracepoint_add_old_probes(void *old)
 440{
 441        need_update = 1;
 442        if (old) {
 443                struct tp_probes *tp_probes = container_of(old,
 444                        struct tp_probes, probes[0]);
 445                list_add(&tp_probes->u.list, &old_probes);
 446        }
 447}
 448
 449/**
 450 * tracepoint_probe_register_noupdate -  register a probe but not connect
 451 * @name: tracepoint name
 452 * @probe: probe handler
 453 *
 454 * caller must call tracepoint_probe_update_all()
 455 */
 456int tracepoint_probe_register_noupdate(const char *name, void *probe,
 457                                       void *data)
 458{
 459        struct tracepoint_func *old;
 460
 461        mutex_lock(&tracepoints_mutex);
 462        old = tracepoint_add_probe(name, probe, data);
 463        if (IS_ERR(old)) {
 464                mutex_unlock(&tracepoints_mutex);
 465                return PTR_ERR(old);
 466        }
 467        tracepoint_add_old_probes(old);
 468        mutex_unlock(&tracepoints_mutex);
 469        return 0;
 470}
 471EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
 472
 473/**
 474 * tracepoint_probe_unregister_noupdate -  remove a probe but not disconnect
 475 * @name: tracepoint name
 476 * @probe: probe function pointer
 477 *
 478 * caller must call tracepoint_probe_update_all()
 479 */
 480int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
 481                                         void *data)
 482{
 483        struct tracepoint_func *old;
 484
 485        mutex_lock(&tracepoints_mutex);
 486        old = tracepoint_remove_probe(name, probe, data);
 487        if (IS_ERR(old)) {
 488                mutex_unlock(&tracepoints_mutex);
 489                return PTR_ERR(old);
 490        }
 491        tracepoint_add_old_probes(old);
 492        mutex_unlock(&tracepoints_mutex);
 493        return 0;
 494}
 495EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
 496
 497/**
 498 * tracepoint_probe_update_all -  update tracepoints
 499 */
 500void tracepoint_probe_update_all(void)
 501{
 502        LIST_HEAD(release_probes);
 503        struct tp_probes *pos, *next;
 504
 505        mutex_lock(&tracepoints_mutex);
 506        if (!need_update) {
 507                mutex_unlock(&tracepoints_mutex);
 508                return;
 509        }
 510        if (!list_empty(&old_probes))
 511                list_replace_init(&old_probes, &release_probes);
 512        need_update = 0;
 513        tracepoint_update_probes();
 514        mutex_unlock(&tracepoints_mutex);
 515        list_for_each_entry_safe(pos, next, &release_probes, u.list) {
 516                list_del(&pos->u.list);
 517                call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
 518        }
 519}
 520EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
 521
 522/**
 523 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
 524 * @tracepoint: current tracepoints (in), next tracepoint (out)
 525 * @begin: beginning of the range
 526 * @end: end of the range
 527 *
 528 * Returns whether a next tracepoint has been found (1) or not (0).
 529 * Will return the first tracepoint in the range if the input tracepoint is
 530 * NULL.
 531 */
 532static int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
 533        struct tracepoint * const *begin, struct tracepoint * const *end)
 534{
 535        if (!*tracepoint && begin != end) {
 536                *tracepoint = begin;
 537                return 1;
 538        }
 539        if (*tracepoint >= begin && *tracepoint < end)
 540                return 1;
 541        return 0;
 542}
 543
 544#ifdef CONFIG_MODULES
 545static void tracepoint_get_iter(struct tracepoint_iter *iter)
 546{
 547        int found = 0;
 548        struct tp_module *iter_mod;
 549
 550        /* Core kernel tracepoints */
 551        if (!iter->module) {
 552                found = tracepoint_get_iter_range(&iter->tracepoint,
 553                                __start___tracepoints_ptrs,
 554                                __stop___tracepoints_ptrs);
 555                if (found)
 556                        goto end;
 557        }
 558        /* Tracepoints in modules */
 559        mutex_lock(&tracepoints_mutex);
 560        list_for_each_entry(iter_mod, &tracepoint_module_list, list) {
 561                /*
 562                 * Sorted module list
 563                 */
 564                if (iter_mod < iter->module)
 565                        continue;
 566                else if (iter_mod > iter->module)
 567                        iter->tracepoint = NULL;
 568                found = tracepoint_get_iter_range(&iter->tracepoint,
 569                        iter_mod->tracepoints_ptrs,
 570                        iter_mod->tracepoints_ptrs
 571                                + iter_mod->num_tracepoints);
 572                if (found) {
 573                        iter->module = iter_mod;
 574                        break;
 575                }
 576        }
 577        mutex_unlock(&tracepoints_mutex);
 578end:
 579        if (!found)
 580                tracepoint_iter_reset(iter);
 581}
 582#else /* CONFIG_MODULES */
 583static void tracepoint_get_iter(struct tracepoint_iter *iter)
 584{
 585        int found = 0;
 586
 587        /* Core kernel tracepoints */
 588        found = tracepoint_get_iter_range(&iter->tracepoint,
 589                        __start___tracepoints_ptrs,
 590                        __stop___tracepoints_ptrs);
 591        if (!found)
 592                tracepoint_iter_reset(iter);
 593}
 594#endif /* CONFIG_MODULES */
 595
 596void tracepoint_iter_start(struct tracepoint_iter *iter)
 597{
 598        tracepoint_get_iter(iter);
 599}
 600EXPORT_SYMBOL_GPL(tracepoint_iter_start);
 601
 602void tracepoint_iter_next(struct tracepoint_iter *iter)
 603{
 604        iter->tracepoint++;
 605        /*
 606         * iter->tracepoint may be invalid because we blindly incremented it.
 607         * Make sure it is valid by marshalling on the tracepoints, getting the
 608         * tracepoints from following modules if necessary.
 609         */
 610        tracepoint_get_iter(iter);
 611}
 612EXPORT_SYMBOL_GPL(tracepoint_iter_next);
 613
 614void tracepoint_iter_stop(struct tracepoint_iter *iter)
 615{
 616}
 617EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
 618
 619void tracepoint_iter_reset(struct tracepoint_iter *iter)
 620{
 621#ifdef CONFIG_MODULES
 622        iter->module = NULL;
 623#endif /* CONFIG_MODULES */
 624        iter->tracepoint = NULL;
 625}
 626EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
 627
 628#ifdef CONFIG_MODULES
 629static int tracepoint_module_coming(struct module *mod)
 630{
 631        struct tp_module *tp_mod, *iter;
 632        int ret = 0;
 633
 634        /*
 635         * We skip modules that taint the kernel, especially those with different
 636         * module headers (for forced load), to make sure we don't cause a crash.
 637         * Staging and out-of-tree GPL modules are fine.
 638         */
 639        if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)))
 640                return 0;
 641        mutex_lock(&tracepoints_mutex);
 642        tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
 643        if (!tp_mod) {
 644                ret = -ENOMEM;
 645                goto end;
 646        }
 647        tp_mod->num_tracepoints = mod->num_tracepoints;
 648        tp_mod->tracepoints_ptrs = mod->tracepoints_ptrs;
 649
 650        /*
 651         * tracepoint_module_list is kept sorted by struct module pointer
 652         * address for iteration on tracepoints from a seq_file that can release
 653         * the mutex between calls.
 654         */
 655        list_for_each_entry_reverse(iter, &tracepoint_module_list, list) {
 656                BUG_ON(iter == tp_mod); /* Should never be in the list twice */
 657                if (iter < tp_mod) {
 658                        /* We belong to the location right after iter. */
 659                        list_add(&tp_mod->list, &iter->list);
 660                        goto module_added;
 661                }
 662        }
 663        /* We belong to the beginning of the list */
 664        list_add(&tp_mod->list, &tracepoint_module_list);
 665module_added:
 666        tracepoint_update_probe_range(mod->tracepoints_ptrs,
 667                mod->tracepoints_ptrs + mod->num_tracepoints);
 668end:
 669        mutex_unlock(&tracepoints_mutex);
 670        return ret;
 671}
 672
 673static int tracepoint_module_going(struct module *mod)
 674{
 675        struct tp_module *pos;
 676
 677        mutex_lock(&tracepoints_mutex);
 678        tracepoint_update_probe_range(mod->tracepoints_ptrs,
 679                mod->tracepoints_ptrs + mod->num_tracepoints);
 680        list_for_each_entry(pos, &tracepoint_module_list, list) {
 681                if (pos->tracepoints_ptrs == mod->tracepoints_ptrs) {
 682                        list_del(&pos->list);
 683                        kfree(pos);
 684                        break;
 685                }
 686        }
 687        /*
 688         * In the case of modules that were tainted at "coming", we'll simply
 689         * walk through the list without finding it. We cannot use the "tainted"
 690         * flag on "going", in case a module taints the kernel only after being
 691         * loaded.
 692         */
 693        mutex_unlock(&tracepoints_mutex);
 694        return 0;
 695}
 696
 697int tracepoint_module_notify(struct notifier_block *self,
 698                             unsigned long val, void *data)
 699{
 700        struct module *mod = data;
 701        int ret = 0;
 702
 703        switch (val) {
 704        case MODULE_STATE_COMING:
 705                ret = tracepoint_module_coming(mod);
 706                break;
 707        case MODULE_STATE_LIVE:
 708                break;
 709        case MODULE_STATE_GOING:
 710                ret = tracepoint_module_going(mod);
 711                break;
 712        }
 713        return ret;
 714}
 715
 716struct notifier_block tracepoint_module_nb = {
 717        .notifier_call = tracepoint_module_notify,
 718        .priority = 0,
 719};
 720
 721static int init_tracepoints(void)
 722{
 723        return register_module_notifier(&tracepoint_module_nb);
 724}
 725__initcall(init_tracepoints);
 726#endif /* CONFIG_MODULES */
 727
 728#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 729
 730/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 731static int sys_tracepoint_refcount;
 732
 733void syscall_regfunc(void)
 734{
 735        unsigned long flags;
 736        struct task_struct *g, *t;
 737
 738        if (!sys_tracepoint_refcount) {
 739                read_lock_irqsave(&tasklist_lock, flags);
 740                do_each_thread(g, t) {
 741                        /* Skip kernel threads. */
 742                        if (t->mm)
 743                                set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 744                } while_each_thread(g, t);
 745                read_unlock_irqrestore(&tasklist_lock, flags);
 746        }
 747        sys_tracepoint_refcount++;
 748}
 749
 750void syscall_unregfunc(void)
 751{
 752        unsigned long flags;
 753        struct task_struct *g, *t;
 754
 755        sys_tracepoint_refcount--;
 756        if (!sys_tracepoint_refcount) {
 757                read_lock_irqsave(&tasklist_lock, flags);
 758                do_each_thread(g, t) {
 759                        clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 760                } while_each_thread(g, t);
 761                read_unlock_irqrestore(&tasklist_lock, flags);
 762        }
 763}
 764#endif
 765
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