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 hlist_node *node;
 196        struct tracepoint_entry *e;
 197        u32 hash = jhash(name, strlen(name), 0);
 198
 199        head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
 200        hlist_for_each_entry(e, node, head, hlist) {
 201                if (!strcmp(name, e->name))
 202                        return e;
 203        }
 204        return NULL;
 205}
 206
 207/*
 208 * Add the tracepoint to the tracepoint hash table. Must be called with
 209 * tracepoints_mutex held.
 210 */
 211static struct tracepoint_entry *add_tracepoint(const char *name)
 212{
 213        struct hlist_head *head;
 214        struct hlist_node *node;
 215        struct tracepoint_entry *e;
 216        size_t name_len = strlen(name) + 1;
 217        u32 hash = jhash(name, name_len-1, 0);
 218
 219        head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
 220        hlist_for_each_entry(e, node, head, hlist) {
 221                if (!strcmp(name, e->name)) {
 222                        printk(KERN_NOTICE
 223                                "tracepoint %s busy\n", name);
 224                        return ERR_PTR(-EEXIST);        /* Already there */
 225                }
 226        }
 227        /*
 228         * Using kmalloc here to allocate a variable length element. Could
 229         * cause some memory fragmentation if overused.
 230         */
 231        e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
 232        if (!e)
 233                return ERR_PTR(-ENOMEM);
 234        memcpy(&e->name[0], name, name_len);
 235        e->funcs = NULL;
 236        e->refcount = 0;
 237        hlist_add_head(&e->hlist, head);
 238        return e;
 239}
 240
 241/*
 242 * Remove the tracepoint from the tracepoint hash table. Must be called with
 243 * mutex_lock held.
 244 */
 245static inline void remove_tracepoint(struct tracepoint_entry *e)
 246{
 247        hlist_del(&e->hlist);
 248        kfree(e);
 249}
 250
 251/*
 252 * Sets the probe callback corresponding to one tracepoint.
 253 */
 254static void set_tracepoint(struct tracepoint_entry **entry,
 255        struct tracepoint *elem, int active)
 256{
 257        WARN_ON(strcmp((*entry)->name, elem->name) != 0);
 258
 259        if (elem->regfunc && !static_key_enabled(&elem->key) && active)
 260                elem->regfunc();
 261        else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
 262                elem->unregfunc();
 263
 264        /*
 265         * rcu_assign_pointer has a smp_wmb() which makes sure that the new
 266         * probe callbacks array is consistent before setting a pointer to it.
 267         * This array is referenced by __DO_TRACE from
 268         * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
 269         * is used.
 270         */
 271        rcu_assign_pointer(elem->funcs, (*entry)->funcs);
 272        if (active && !static_key_enabled(&elem->key))
 273                static_key_slow_inc(&elem->key);
 274        else if (!active && static_key_enabled(&elem->key))
 275                static_key_slow_dec(&elem->key);
 276}
 277
 278/*
 279 * Disable a tracepoint and its probe callback.
 280 * Note: only waiting an RCU period after setting elem->call to the empty
 281 * function insures that the original callback is not used anymore. This insured
 282 * by preempt_disable around the call site.
 283 */
 284static void disable_tracepoint(struct tracepoint *elem)
 285{
 286        if (elem->unregfunc && static_key_enabled(&elem->key))
 287                elem->unregfunc();
 288
 289        if (static_key_enabled(&elem->key))
 290                static_key_slow_dec(&elem->key);
 291        rcu_assign_pointer(elem->funcs, 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 * Called with tracepoints_mutex held.
 301 */
 302static 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        if (!begin)
 309                return;
 310
 311        for (iter = begin; iter < end; iter++) {
 312                mark_entry = get_tracepoint((*iter)->name);
 313                if (mark_entry) {
 314                        set_tracepoint(&mark_entry, *iter,
 315                                        !!mark_entry->refcount);
 316                } else {
 317                        disable_tracepoint(*iter);
 318                }
 319        }
 320}
 321
 322#ifdef CONFIG_MODULES
 323void module_update_tracepoints(void)
 324{
 325        struct tp_module *tp_mod;
 326
 327        list_for_each_entry(tp_mod, &tracepoint_module_list, list)
 328                tracepoint_update_probe_range(tp_mod->tracepoints_ptrs,
 329                        tp_mod->tracepoints_ptrs + tp_mod->num_tracepoints);
 330}
 331#else /* CONFIG_MODULES */
 332void module_update_tracepoints(void)
 333{
 334}
 335#endif /* CONFIG_MODULES */
 336
 337
 338/*
 339 * Update probes, removing the faulty probes.
 340 * Called with tracepoints_mutex held.
 341 */
 342static void tracepoint_update_probes(void)
 343{
 344        /* Core kernel tracepoints */
 345        tracepoint_update_probe_range(__start___tracepoints_ptrs,
 346                __stop___tracepoints_ptrs);
 347        /* tracepoints in modules. */
 348        module_update_tracepoints();
 349}
 350
 351static struct tracepoint_func *
 352tracepoint_add_probe(const char *name, void *probe, void *data)
 353{
 354        struct tracepoint_entry *entry;
 355        struct tracepoint_func *old;
 356
 357        entry = get_tracepoint(name);
 358        if (!entry) {
 359                entry = add_tracepoint(name);
 360                if (IS_ERR(entry))
 361                        return (struct tracepoint_func *)entry;
 362        }
 363        old = tracepoint_entry_add_probe(entry, probe, data);
 364        if (IS_ERR(old) && !entry->refcount)
 365                remove_tracepoint(entry);
 366        return old;
 367}
 368
 369/**
 370 * tracepoint_probe_register -  Connect a probe to a tracepoint
 371 * @name: tracepoint name
 372 * @probe: probe handler
 373 *
 374 * Returns 0 if ok, error value on error.
 375 * The probe address must at least be aligned on the architecture pointer size.
 376 */
 377int tracepoint_probe_register(const char *name, void *probe, void *data)
 378{
 379        struct tracepoint_func *old;
 380
 381        mutex_lock(&tracepoints_mutex);
 382        old = tracepoint_add_probe(name, probe, data);
 383        if (IS_ERR(old)) {
 384                mutex_unlock(&tracepoints_mutex);
 385                return PTR_ERR(old);
 386        }
 387        tracepoint_update_probes();             /* may update entry */
 388        mutex_unlock(&tracepoints_mutex);
 389        release_probes(old);
 390        return 0;
 391}
 392EXPORT_SYMBOL_GPL(tracepoint_probe_register);
 393
 394static struct tracepoint_func *
 395tracepoint_remove_probe(const char *name, void *probe, void *data)
 396{
 397        struct tracepoint_entry *entry;
 398        struct tracepoint_func *old;
 399
 400        entry = get_tracepoint(name);
 401        if (!entry)
 402                return ERR_PTR(-ENOENT);
 403        old = tracepoint_entry_remove_probe(entry, probe, data);
 404        if (IS_ERR(old))
 405                return old;
 406        if (!entry->refcount)
 407                remove_tracepoint(entry);
 408        return old;
 409}
 410
 411/**
 412 * tracepoint_probe_unregister -  Disconnect a probe from a tracepoint
 413 * @name: tracepoint name
 414 * @probe: probe function pointer
 415 *
 416 * We do not need to call a synchronize_sched to make sure the probes have
 417 * finished running before doing a module unload, because the module unload
 418 * itself uses stop_machine(), which insures that every preempt disabled section
 419 * have finished.
 420 */
 421int tracepoint_probe_unregister(const char *name, void *probe, void *data)
 422{
 423        struct tracepoint_func *old;
 424
 425        mutex_lock(&tracepoints_mutex);
 426        old = tracepoint_remove_probe(name, probe, data);
 427        if (IS_ERR(old)) {
 428                mutex_unlock(&tracepoints_mutex);
 429                return PTR_ERR(old);
 430        }
 431        tracepoint_update_probes();             /* may update entry */
 432        mutex_unlock(&tracepoints_mutex);
 433        release_probes(old);
 434        return 0;
 435}
 436EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
 437
 438static LIST_HEAD(old_probes);
 439static int need_update;
 440
 441static void tracepoint_add_old_probes(void *old)
 442{
 443        need_update = 1;
 444        if (old) {
 445                struct tp_probes *tp_probes = container_of(old,
 446                        struct tp_probes, probes[0]);
 447                list_add(&tp_probes->u.list, &old_probes);
 448        }
 449}
 450
 451/**
 452 * tracepoint_probe_register_noupdate -  register a probe but not connect
 453 * @name: tracepoint name
 454 * @probe: probe handler
 455 *
 456 * caller must call tracepoint_probe_update_all()
 457 */
 458int tracepoint_probe_register_noupdate(const char *name, void *probe,
 459                                       void *data)
 460{
 461        struct tracepoint_func *old;
 462
 463        mutex_lock(&tracepoints_mutex);
 464        old = tracepoint_add_probe(name, probe, data);
 465        if (IS_ERR(old)) {
 466                mutex_unlock(&tracepoints_mutex);
 467                return PTR_ERR(old);
 468        }
 469        tracepoint_add_old_probes(old);
 470        mutex_unlock(&tracepoints_mutex);
 471        return 0;
 472}
 473EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
 474
 475/**
 476 * tracepoint_probe_unregister_noupdate -  remove a probe but not disconnect
 477 * @name: tracepoint name
 478 * @probe: probe function pointer
 479 *
 480 * caller must call tracepoint_probe_update_all()
 481 */
 482int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
 483                                         void *data)
 484{
 485        struct tracepoint_func *old;
 486
 487        mutex_lock(&tracepoints_mutex);
 488        old = tracepoint_remove_probe(name, probe, data);
 489        if (IS_ERR(old)) {
 490                mutex_unlock(&tracepoints_mutex);
 491                return PTR_ERR(old);
 492        }
 493        tracepoint_add_old_probes(old);
 494        mutex_unlock(&tracepoints_mutex);
 495        return 0;
 496}
 497EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
 498
 499/**
 500 * tracepoint_probe_update_all -  update tracepoints
 501 */
 502void tracepoint_probe_update_all(void)
 503{
 504        LIST_HEAD(release_probes);
 505        struct tp_probes *pos, *next;
 506
 507        mutex_lock(&tracepoints_mutex);
 508        if (!need_update) {
 509                mutex_unlock(&tracepoints_mutex);
 510                return;
 511        }
 512        if (!list_empty(&old_probes))
 513                list_replace_init(&old_probes, &release_probes);
 514        need_update = 0;
 515        tracepoint_update_probes();
 516        mutex_unlock(&tracepoints_mutex);
 517        list_for_each_entry_safe(pos, next, &release_probes, u.list) {
 518                list_del(&pos->u.list);
 519                call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
 520        }
 521}
 522EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
 523
 524/**
 525 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
 526 * @tracepoint: current tracepoints (in), next tracepoint (out)
 527 * @begin: beginning of the range
 528 * @end: end of the range
 529 *
 530 * Returns whether a next tracepoint has been found (1) or not (0).
 531 * Will return the first tracepoint in the range if the input tracepoint is
 532 * NULL.
 533 */
 534static int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
 535        struct tracepoint * const *begin, struct tracepoint * const *end)
 536{
 537        if (!*tracepoint && begin != end) {
 538                *tracepoint = begin;
 539                return 1;
 540        }
 541        if (*tracepoint >= begin && *tracepoint < end)
 542                return 1;
 543        return 0;
 544}
 545
 546#ifdef CONFIG_MODULES
 547static void tracepoint_get_iter(struct tracepoint_iter *iter)
 548{
 549        int found = 0;
 550        struct tp_module *iter_mod;
 551
 552        /* Core kernel tracepoints */
 553        if (!iter->module) {
 554                found = tracepoint_get_iter_range(&iter->tracepoint,
 555                                __start___tracepoints_ptrs,
 556                                __stop___tracepoints_ptrs);
 557                if (found)
 558                        goto end;
 559        }
 560        /* Tracepoints in modules */
 561        mutex_lock(&tracepoints_mutex);
 562        list_for_each_entry(iter_mod, &tracepoint_module_list, list) {
 563                /*
 564                 * Sorted module list
 565                 */
 566                if (iter_mod < iter->module)
 567                        continue;
 568                else if (iter_mod > iter->module)
 569                        iter->tracepoint = NULL;
 570                found = tracepoint_get_iter_range(&iter->tracepoint,
 571                        iter_mod->tracepoints_ptrs,
 572                        iter_mod->tracepoints_ptrs
 573                                + iter_mod->num_tracepoints);
 574                if (found) {
 575                        iter->module = iter_mod;
 576                        break;
 577                }
 578        }
 579        mutex_unlock(&tracepoints_mutex);
 580end:
 581        if (!found)
 582                tracepoint_iter_reset(iter);
 583}
 584#else /* CONFIG_MODULES */
 585static void tracepoint_get_iter(struct tracepoint_iter *iter)
 586{
 587        int found = 0;
 588
 589        /* Core kernel tracepoints */
 590        found = tracepoint_get_iter_range(&iter->tracepoint,
 591                        __start___tracepoints_ptrs,
 592                        __stop___tracepoints_ptrs);
 593        if (!found)
 594                tracepoint_iter_reset(iter);
 595}
 596#endif /* CONFIG_MODULES */
 597
 598void tracepoint_iter_start(struct tracepoint_iter *iter)
 599{
 600        tracepoint_get_iter(iter);
 601}
 602EXPORT_SYMBOL_GPL(tracepoint_iter_start);
 603
 604void tracepoint_iter_next(struct tracepoint_iter *iter)
 605{
 606        iter->tracepoint++;
 607        /*
 608         * iter->tracepoint may be invalid because we blindly incremented it.
 609         * Make sure it is valid by marshalling on the tracepoints, getting the
 610         * tracepoints from following modules if necessary.
 611         */
 612        tracepoint_get_iter(iter);
 613}
 614EXPORT_SYMBOL_GPL(tracepoint_iter_next);
 615
 616void tracepoint_iter_stop(struct tracepoint_iter *iter)
 617{
 618}
 619EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
 620
 621void tracepoint_iter_reset(struct tracepoint_iter *iter)
 622{
 623#ifdef CONFIG_MODULES
 624        iter->module = NULL;
 625#endif /* CONFIG_MODULES */
 626        iter->tracepoint = NULL;
 627}
 628EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
 629
 630#ifdef CONFIG_MODULES
 631static int tracepoint_module_coming(struct module *mod)
 632{
 633        struct tp_module *tp_mod, *iter;
 634        int ret = 0;
 635
 636        /*
 637         * We skip modules that taint the kernel, especially those with different
 638         * module headers (for forced load), to make sure we don't cause a crash.
 639         * Staging and out-of-tree GPL modules are fine.
 640         */
 641        if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)))
 642                return 0;
 643        mutex_lock(&tracepoints_mutex);
 644        tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
 645        if (!tp_mod) {
 646                ret = -ENOMEM;
 647                goto end;
 648        }
 649        tp_mod->num_tracepoints = mod->num_tracepoints;
 650        tp_mod->tracepoints_ptrs = mod->tracepoints_ptrs;
 651
 652        /*
 653         * tracepoint_module_list is kept sorted by struct module pointer
 654         * address for iteration on tracepoints from a seq_file that can release
 655         * the mutex between calls.
 656         */
 657        list_for_each_entry_reverse(iter, &tracepoint_module_list, list) {
 658                BUG_ON(iter == tp_mod); /* Should never be in the list twice */
 659                if (iter < tp_mod) {
 660                        /* We belong to the location right after iter. */
 661                        list_add(&tp_mod->list, &iter->list);
 662                        goto module_added;
 663                }
 664        }
 665        /* We belong to the beginning of the list */
 666        list_add(&tp_mod->list, &tracepoint_module_list);
 667module_added:
 668        tracepoint_update_probe_range(mod->tracepoints_ptrs,
 669                mod->tracepoints_ptrs + mod->num_tracepoints);
 670end:
 671        mutex_unlock(&tracepoints_mutex);
 672        return ret;
 673}
 674
 675static int tracepoint_module_going(struct module *mod)
 676{
 677        struct tp_module *pos;
 678
 679        mutex_lock(&tracepoints_mutex);
 680        tracepoint_update_probe_range(mod->tracepoints_ptrs,
 681                mod->tracepoints_ptrs + mod->num_tracepoints);
 682        list_for_each_entry(pos, &tracepoint_module_list, list) {
 683                if (pos->tracepoints_ptrs == mod->tracepoints_ptrs) {
 684                        list_del(&pos->list);
 685                        kfree(pos);
 686                        break;
 687                }
 688        }
 689        /*
 690         * In the case of modules that were tainted at "coming", we'll simply
 691         * walk through the list without finding it. We cannot use the "tainted"
 692         * flag on "going", in case a module taints the kernel only after being
 693         * loaded.
 694         */
 695        mutex_unlock(&tracepoints_mutex);
 696        return 0;
 697}
 698
 699int tracepoint_module_notify(struct notifier_block *self,
 700                             unsigned long val, void *data)
 701{
 702        struct module *mod = data;
 703        int ret = 0;
 704
 705        switch (val) {
 706        case MODULE_STATE_COMING:
 707                ret = tracepoint_module_coming(mod);
 708                break;
 709        case MODULE_STATE_LIVE:
 710                break;
 711        case MODULE_STATE_GOING:
 712                ret = tracepoint_module_going(mod);
 713                break;
 714        }
 715        return ret;
 716}
 717
 718struct notifier_block tracepoint_module_nb = {
 719        .notifier_call = tracepoint_module_notify,
 720        .priority = 0,
 721};
 722
 723static int init_tracepoints(void)
 724{
 725        return register_module_notifier(&tracepoint_module_nb);
 726}
 727__initcall(init_tracepoints);
 728#endif /* CONFIG_MODULES */
 729
 730#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 731
 732/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 733static int sys_tracepoint_refcount;
 734
 735void syscall_regfunc(void)
 736{
 737        unsigned long flags;
 738        struct task_struct *g, *t;
 739
 740        if (!sys_tracepoint_refcount) {
 741                read_lock_irqsave(&tasklist_lock, flags);
 742                do_each_thread(g, t) {
 743                        /* Skip kernel threads. */
 744                        if (t->mm)
 745                                set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 746                } while_each_thread(g, t);
 747                read_unlock_irqrestore(&tasklist_lock, flags);
 748        }
 749        sys_tracepoint_refcount++;
 750}
 751
 752void syscall_unregfunc(void)
 753{
 754        unsigned long flags;
 755        struct task_struct *g, *t;
 756
 757        sys_tracepoint_refcount--;
 758        if (!sys_tracepoint_refcount) {
 759                read_lock_irqsave(&tasklist_lock, flags);
 760                do_each_thread(g, t) {
 761                        clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 762                } while_each_thread(g, t);
 763                read_unlock_irqrestore(&tasklist_lock, flags);
 764        }
 765}
 766#endif
 767
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