1 files changed, 223 insertions, 293 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index fb0a38a26555..ac5b23cf7212 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008 Mathieu Desnoyers
+ * Copyright (C) 2008-2014 Mathieu Desnoyers
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -33,39 +33,27 @@ extern struct tracepoint * const __stop___tracepoints_ptrs[];
 /* Set to 1 to enable tracepoint debug output */
 static const int tracepoint_debug;
 
+#ifdef CONFIG_MODULES
 /*
- * Tracepoints mutex protects the builtin and module tracepoints and the hash
- * table, as well as the local module list.
+ * Tracepoint module list mutex protects the local module list.
  */
-static DEFINE_MUTEX(tracepoints_mutex);
+static DEFINE_MUTEX(tracepoint_module_list_mutex);
 
-#ifdef CONFIG_MODULES
-/* Local list of struct module */
+/* Local list of struct tp_module */
 static LIST_HEAD(tracepoint_module_list);
 #endif /* CONFIG_MODULES */
 
 /*
- * Tracepoint hash table, containing the active tracepoints.
- * Protected by tracepoints_mutex.
+ * tracepoints_mutex protects the builtin and module tracepoints.
+ * tracepoints_mutex nests inside tracepoint_module_list_mutex.
  */
-#define TRACEPOINT_HASH_BITS 6
-#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
-static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+static DEFINE_MUTEX(tracepoints_mutex);
 
 /*
  * Note about RCU :
  * It is used to delay the free of multiple probes array until a quiescent
  * state is reached.
- * Tracepoint entries modifications are protected by the tracepoints_mutex.
  */
-struct tracepoint_entry {
-        struct hlist_node hlist;
-        struct tracepoint_func *funcs;
-        int refcount;   /* Number of times armed. 0 if disarmed. */
-        int enabled;    /* Tracepoint enabled */
-        char name[0];
-};
-
 struct tp_probes {
         struct rcu_head rcu;
         struct tracepoint_func probes[0];
@@ -92,34 +80,33 @@ static inline void release_probes(struct tracepoint_func *old)
         }
 }
 
-static void debug_print_probes(struct tracepoint_entry *entry)
+static void debug_print_probes(struct tracepoint_func *funcs)
 {
         int i;
 
-        if (!tracepoint_debug || !entry->funcs)
+        if (!tracepoint_debug || !funcs)
                 return;
 
-        for (i = 0; entry->funcs[i].func; i++)
-                printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
+        for (i = 0; funcs[i].func; i++)
+                printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
 }
 
-static struct tracepoint_func *
-tracepoint_entry_add_probe(struct tracepoint_entry *entry,
-                           void *probe, void *data)
+static struct tracepoint_func *func_add(struct tracepoint_func **funcs,
+                struct tracepoint_func *tp_func)
 {
         int nr_probes = 0;
         struct tracepoint_func *old, *new;
 
-        if (WARN_ON(!probe))
+        if (WARN_ON(!tp_func->func))
                 return ERR_PTR(-EINVAL);
 
-        debug_print_probes(entry);
-        old = entry->funcs;
+        debug_print_probes(*funcs);
+        old = *funcs;
         if (old) {
                 /* (N -> N+1), (N != 0, 1) probes */
                 for (nr_probes = 0; old[nr_probes].func; nr_probes++)
-                        if (old[nr_probes].func == probe &&
-                            old[nr_probes].data == data)
+                        if (old[nr_probes].func == tp_func->func &&
+                            old[nr_probes].data == tp_func->data)
                                 return ERR_PTR(-EEXIST);
         }
         /* + 2 : one for new probe, one for NULL func */
@@ -128,33 +115,30 @@ tracepoint_entry_add_probe(struct tracepoint_entry *entry,
                 return ERR_PTR(-ENOMEM);
         if (old)
                 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
-        new[nr_probes].func = probe;
-        new[nr_probes].data = data;
+        new[nr_probes] = *tp_func;
         new[nr_probes + 1].func = NULL;
-        entry->refcount = nr_probes + 1;
-        entry->funcs = new;
-        debug_print_probes(entry);
+        *funcs = new;
+        debug_print_probes(*funcs);
         return old;
 }
 
-static void *
-tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
-                              void *probe, void *data)
+static void *func_remove(struct tracepoint_func **funcs,
+                struct tracepoint_func *tp_func)
 {
         int nr_probes = 0, nr_del = 0, i;
         struct tracepoint_func *old, *new;
 
-        old = entry->funcs;
+        old = *funcs;
 
         if (!old)
                 return ERR_PTR(-ENOENT);
 
-        debug_print_probes(entry);
+        debug_print_probes(*funcs);
         /* (N -> M), (N > 1, M >= 0) probes */
-        if (probe) {
+        if (tp_func->func) {
                 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
-                        if (old[nr_probes].func == probe &&
-                             old[nr_probes].data == data)
+                        if (old[nr_probes].func == tp_func->func &&
+                             old[nr_probes].data == tp_func->data)
                                 nr_del++;
                 }
         }
@@ -165,9 +149,8 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
          */
         if (nr_probes - nr_del == 0) {
                 /* N -> 0, (N > 1) */
-                entry->funcs = NULL;
-                entry->refcount = 0;
-                debug_print_probes(entry);
+                *funcs = NULL;
+                debug_print_probes(*funcs);
                 return old;
         } else {
                 int j = 0;
@@ -177,91 +160,35 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
                 if (new == NULL)
                         return ERR_PTR(-ENOMEM);
                 for (i = 0; old[i].func; i++)
-                        if (old[i].func != probe || old[i].data != data)
+                        if (old[i].func != tp_func->func
+                                        || old[i].data != tp_func->data)
                                 new[j++] = old[i];
                 new[nr_probes - nr_del].func = NULL;
-                entry->refcount = nr_probes - nr_del;
-                entry->funcs = new;
+                *funcs = new;
         }
-        debug_print_probes(entry);
+        debug_print_probes(*funcs);
         return old;
 }
 
 /*
- * Get tracepoint if the tracepoint is present in the tracepoint hash table.
- * Must be called with tracepoints_mutex held.
- * Returns NULL if not present.
+ * Add the probe function to a tracepoint.
  */
-static struct tracepoint_entry *get_tracepoint(const char *name)
+static int tracepoint_add_func(struct tracepoint *tp,
+                struct tracepoint_func *func)
 {
-        struct hlist_head *head;
-        struct tracepoint_entry *e;
-        u32 hash = jhash(name, strlen(name), 0);
-
-        head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
-        hlist_for_each_entry(e, head, hlist) {
-                if (!strcmp(name, e->name))
-                        return e;
-        }
-        return NULL;
-}
+        struct tracepoint_func *old, *tp_funcs;
 
-/*
- * Add the tracepoint to the tracepoint hash table. Must be called with
- * tracepoints_mutex held.
- */
-static struct tracepoint_entry *add_tracepoint(const char *name)
-{
-        struct hlist_head *head;
-        struct tracepoint_entry *e;
-        size_t name_len = strlen(name) + 1;
-        u32 hash = jhash(name, name_len-1, 0);
-
-        head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
-        hlist_for_each_entry(e, head, hlist) {
-                if (!strcmp(name, e->name)) {
-                        printk(KERN_NOTICE
-                                "tracepoint %s busy\n", name);
-                        return ERR_PTR(-EEXIST);        /* Already there */
-                }
-        }
-        /*
-         * Using kmalloc here to allocate a variable length element. Could
-         * cause some memory fragmentation if overused.
-         */
-        e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
-        if (!e)
-                return ERR_PTR(-ENOMEM);
-        memcpy(&e->name[0], name, name_len);
-        e->funcs = NULL;
-        e->refcount = 0;
-        e->enabled = 0;
-        hlist_add_head(&e->hlist, head);
-        return e;
-}
+        if (tp->regfunc && !static_key_enabled(&tp->key))
+                tp->regfunc();
 
-/*
- * Remove the tracepoint from the tracepoint hash table. Must be called with
- * mutex_lock held.
- */
-static inline void remove_tracepoint(struct tracepoint_entry *e)
-{
-        hlist_del(&e->hlist);
-        kfree(e);
-}
-
-/*
- * Sets the probe callback corresponding to one tracepoint.
- */
-static void set_tracepoint(struct tracepoint_entry **entry,
-        struct tracepoint *elem, int active)
-{
-        WARN_ON(strcmp((*entry)->name, elem->name) != 0);
-
-        if (elem->regfunc && !static_key_enabled(&elem->key) && active)
-                elem->regfunc();
-        else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
-                elem->unregfunc();
+        tp_funcs = rcu_dereference_protected(tp->funcs,
+                        lockdep_is_held(&tracepoints_mutex));
+        old = func_add(&tp_funcs, func);
+        if (IS_ERR(old)) {
+                WARN_ON_ONCE(1);
+                return PTR_ERR(old);
+        }
+        release_probes(old);
 
         /*
          * rcu_assign_pointer has a smp_wmb() which makes sure that the new
@@ -270,193 +197,90 @@ static void set_tracepoint(struct tracepoint_entry **entry,
          * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
          * is used.
          */
-        rcu_assign_pointer(elem->funcs, (*entry)->funcs);
-        if (active && !static_key_enabled(&elem->key))
-                static_key_slow_inc(&elem->key);
-        else if (!active && static_key_enabled(&elem->key))
-                static_key_slow_dec(&elem->key);
+        rcu_assign_pointer(tp->funcs, tp_funcs);
+        if (!static_key_enabled(&tp->key))
+                static_key_slow_inc(&tp->key);
+        return 0;
 }
 
 /*
- * Disable a tracepoint and its probe callback.
+ * Remove a probe function from a tracepoint.
  * Note: only waiting an RCU period after setting elem->call to the empty
  * function insures that the original callback is not used anymore. This insured
  * by preempt_disable around the call site.
  */
-static void disable_tracepoint(struct tracepoint *elem)
+static int tracepoint_remove_func(struct tracepoint *tp,
+                struct tracepoint_func *func)
 {
-        if (elem->unregfunc && static_key_enabled(&elem->key))
-                elem->unregfunc();
-
-        if (static_key_enabled(&elem->key))
-                static_key_slow_dec(&elem->key);
-        rcu_assign_pointer(elem->funcs, NULL);
-}
+        struct tracepoint_func *old, *tp_funcs;
 
-/**
- * tracepoint_update_probe_range - Update a probe range
- * @begin: beginning of the range
- * @end: end of the range
- *
- * Updates the probe callback corresponding to a range of tracepoints.
- * Called with tracepoints_mutex held.
- */
-static void tracepoint_update_probe_range(struct tracepoint * const *begin,
-                                          struct tracepoint * const *end)
-{
-        struct tracepoint * const *iter;
-        struct tracepoint_entry *mark_entry;
-
-        if (!begin)
-                return;
-
-        for (iter = begin; iter < end; iter++) {
-                mark_entry = get_tracepoint((*iter)->name);
-                if (mark_entry) {
-                        set_tracepoint(&mark_entry, *iter,
-                                        !!mark_entry->refcount);
-                        mark_entry->enabled = !!mark_entry->refcount;
-                } else {
-                        disable_tracepoint(*iter);
-                }
+        tp_funcs = rcu_dereference_protected(tp->funcs,
+                        lockdep_is_held(&tracepoints_mutex));
+        old = func_remove(&tp_funcs, func);
+        if (IS_ERR(old)) {
+                WARN_ON_ONCE(1);
+                return PTR_ERR(old);
         }
-}
-
-#ifdef CONFIG_MODULES
-void module_update_tracepoints(void)
-{
-        struct tp_module *tp_mod;
-
-        list_for_each_entry(tp_mod, &tracepoint_module_list, list)
-                tracepoint_update_probe_range(tp_mod->tracepoints_ptrs,
-                        tp_mod->tracepoints_ptrs + tp_mod->num_tracepoints);
-}
-#else /* CONFIG_MODULES */
-void module_update_tracepoints(void)
-{
-}
-#endif /* CONFIG_MODULES */
+        release_probes(old);
 
+        if (!tp_funcs) {
+                /* Removed last function */
+                if (tp->unregfunc && static_key_enabled(&tp->key))
+                        tp->unregfunc();
 
-/*
- * Update probes, removing the faulty probes.
- * Called with tracepoints_mutex held.
- */
-static void tracepoint_update_probes(void)
-{
-        /* Core kernel tracepoints */
-        tracepoint_update_probe_range(__start___tracepoints_ptrs,
-                __stop___tracepoints_ptrs);
-        /* tracepoints in modules. */
-        module_update_tracepoints();
-}
-
-static struct tracepoint_func *
-tracepoint_add_probe(const char *name, void *probe, void *data)
-{
-        struct tracepoint_entry *entry;
-        struct tracepoint_func *old;
-
-        entry = get_tracepoint(name);
-        if (!entry) {
-                entry = add_tracepoint(name);
-                if (IS_ERR(entry))
-                        return (struct tracepoint_func *)entry;
+                if (static_key_enabled(&tp->key))
+                        static_key_slow_dec(&tp->key);
         }
-        old = tracepoint_entry_add_probe(entry, probe, data);
-        if (IS_ERR(old) && !entry->refcount)
-                remove_tracepoint(entry);
-        return old;
+        rcu_assign_pointer(tp->funcs, tp_funcs);
+        return 0;
 }
 
 /**
  * tracepoint_probe_register -  Connect a probe to a tracepoint
- * @name: tracepoint name
+ * @tp: tracepoint
  * @probe: probe handler
- * @data: probe private data
- *
- * Returns:
- * - 0 if the probe was successfully registered, and tracepoint
- *   callsites are currently loaded for that probe,
- * - -ENODEV if the probe was successfully registered, but no tracepoint
- *   callsite is currently loaded for that probe,
- * - other negative error value on error.
- *
- * When tracepoint_probe_register() returns either 0 or -ENODEV,
- * parameters @name, @probe, and @data may be used by the tracepoint
- * infrastructure until the probe is unregistered.
  *
- * The probe address must at least be aligned on the architecture pointer size.
+ * Returns 0 if ok, error value on error.
+ * Note: if @tp is within a module, the caller is responsible for
+ * unregistering the probe before the module is gone. This can be
+ * performed either with a tracepoint module going notifier, or from
+ * within module exit functions.
  */
-int tracepoint_probe_register(const char *name, void *probe, void *data)
+int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
 {
-        struct tracepoint_func *old;
-        struct tracepoint_entry *entry;
-        int ret = 0;
+        struct tracepoint_func tp_func;
+        int ret;
 
         mutex_lock(&tracepoints_mutex);
-        old = tracepoint_add_probe(name, probe, data);
-        if (IS_ERR(old)) {
-                mutex_unlock(&tracepoints_mutex);
-                return PTR_ERR(old);
-        }
-        tracepoint_update_probes();             /* may update entry */
-        entry = get_tracepoint(name);
-        /* Make sure the entry was enabled */
-        if (!entry || !entry->enabled)
-                ret = -ENODEV;
+        tp_func.func = probe;
+        tp_func.data = data;
+        ret = tracepoint_add_func(tp, &tp_func);
         mutex_unlock(&tracepoints_mutex);
-        release_probes(old);
         return ret;
 }
 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
 
-static struct tracepoint_func *
-tracepoint_remove_probe(const char *name, void *probe, void *data)
-{
-        struct tracepoint_entry *entry;
-        struct tracepoint_func *old;
-
-        entry = get_tracepoint(name);
-        if (!entry)
-                return ERR_PTR(-ENOENT);
-        old = tracepoint_entry_remove_probe(entry, probe, data);
-        if (IS_ERR(old))
-                return old;
-        if (!entry->refcount)
-                remove_tracepoint(entry);
-        return old;
-}
-
 /**
  * tracepoint_probe_unregister -  Disconnect a probe from a tracepoint
- * @name: tracepoint name
+ * @tp: tracepoint
  * @probe: probe function pointer
- * @data: probe private data
  *
- * We do not need to call a synchronize_sched to make sure the probes have
- * finished running before doing a module unload, because the module unload
- * itself uses stop_machine(), which insures that every preempt disabled section
- * have finished.
+ * Returns 0 if ok, error value on error.
  */
-int tracepoint_probe_unregister(const char *name, void *probe, void *data)
+int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
 {
-        struct tracepoint_func *old;
+        struct tracepoint_func tp_func;
+        int ret;
 
         mutex_lock(&tracepoints_mutex);
-        old = tracepoint_remove_probe(name, probe, data);
-        if (IS_ERR(old)) {
-                mutex_unlock(&tracepoints_mutex);
-                return PTR_ERR(old);
-        }
-        tracepoint_update_probes();             /* may update entry */
+        tp_func.func = probe;
+        tp_func.data = data;
+        ret = tracepoint_remove_func(tp, &tp_func);
         mutex_unlock(&tracepoints_mutex);
-        release_probes(old);
-        return 0;
+        return ret;
 }
 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
 
-
 #ifdef CONFIG_MODULES
 bool trace_module_has_bad_taint(struct module *mod)
 {
@@ -464,6 +288,74 @@ bool trace_module_has_bad_taint(struct module *mod)
                                (1 << TAINT_UNSIGNED_MODULE));
 }
 
+static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
+
+/**
+ * register_tracepoint_notifier - register tracepoint coming/going notifier
+ * @nb: notifier block
+ *
+ * Notifiers registered with this function are called on module
+ * coming/going with the tracepoint_module_list_mutex held.
+ * The notifier block callback should expect a "struct tp_module" data
+ * pointer.
+ */
+int register_tracepoint_module_notifier(struct notifier_block *nb)
+{
+        struct tp_module *tp_mod;
+        int ret;
+
+        mutex_lock(&tracepoint_module_list_mutex);
+        ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
+        if (ret)
+                goto end;
+        list_for_each_entry(tp_mod, &tracepoint_module_list, list)
+                (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
+end:
+        mutex_unlock(&tracepoint_module_list_mutex);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
+
+/**
+ * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
+ * @nb: notifier block
+ *
+ * The notifier block callback should expect a "struct tp_module" data
+ * pointer.
+ */
+int unregister_tracepoint_module_notifier(struct notifier_block *nb)
+{
+        struct tp_module *tp_mod;
+        int ret;
+
+        mutex_lock(&tracepoint_module_list_mutex);
+        ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
+        if (ret)
+                goto end;
+        list_for_each_entry(tp_mod, &tracepoint_module_list, list)
+                (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
+end:
+        mutex_unlock(&tracepoint_module_list_mutex);
+        return ret;
+
+}
+EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
+
+/*
+ * Ensure the tracer unregistered the module's probes before the module
+ * teardown is performed. Prevents leaks of probe and data pointers.
+ */
+static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
+                struct tracepoint * const *end)
+{
+        struct tracepoint * const *iter;
+
+        if (!begin)
+                return;
+        for (iter = begin; iter < end; iter++)
+                WARN_ON_ONCE((*iter)->funcs);
+}
+
 static int tracepoint_module_coming(struct module *mod)
 {
         struct tp_module *tp_mod;
@@ -479,36 +371,41 @@ static int tracepoint_module_coming(struct module *mod)
          */
         if (trace_module_has_bad_taint(mod))
                 return 0;
-        mutex_lock(&tracepoints_mutex);
+        mutex_lock(&tracepoint_module_list_mutex);
         tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
         if (!tp_mod) {
                 ret = -ENOMEM;
                 goto end;
         }
-        tp_mod->num_tracepoints = mod->num_tracepoints;
-        tp_mod->tracepoints_ptrs = mod->tracepoints_ptrs;
+        tp_mod->mod = mod;
         list_add_tail(&tp_mod->list, &tracepoint_module_list);
-        tracepoint_update_probe_range(mod->tracepoints_ptrs,
-                mod->tracepoints_ptrs + mod->num_tracepoints);
+        blocking_notifier_call_chain(&tracepoint_notify_list,
+                        MODULE_STATE_COMING, tp_mod);
 end:
-        mutex_unlock(&tracepoints_mutex);
+        mutex_unlock(&tracepoint_module_list_mutex);
         return ret;
 }
 
-static int tracepoint_module_going(struct module *mod)
+static void tracepoint_module_going(struct module *mod)
 {
-        struct tp_module *pos;
+        struct tp_module *tp_mod;
 
         if (!mod->num_tracepoints)
-                return 0;
+                return;
 
-        mutex_lock(&tracepoints_mutex);
-        tracepoint_update_probe_range(mod->tracepoints_ptrs,
-                mod->tracepoints_ptrs + mod->num_tracepoints);
-        list_for_each_entry(pos, &tracepoint_module_list, list) {
-                if (pos->tracepoints_ptrs == mod->tracepoints_ptrs) {
-                        list_del(&pos->list);
-                        kfree(pos);
+        mutex_lock(&tracepoint_module_list_mutex);
+        list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
+                if (tp_mod->mod == mod) {
+                        blocking_notifier_call_chain(&tracepoint_notify_list,
+                                        MODULE_STATE_GOING, tp_mod);
+                        list_del(&tp_mod->list);
+                        kfree(tp_mod);
+                        /*
+                         * Called the going notifier before checking for
+                         * quiescence.
+                         */
+                        tp_module_going_check_quiescent(mod->tracepoints_ptrs,
+                                mod->tracepoints_ptrs + mod->num_tracepoints);
                         break;
                 }
         }
@@ -518,12 +415,11 @@ static int tracepoint_module_going(struct module *mod)
          * flag on "going", in case a module taints the kernel only after being
          * loaded.
          */
-        mutex_unlock(&tracepoints_mutex);
-        return 0;
+        mutex_unlock(&tracepoint_module_list_mutex);
 }
 
-int tracepoint_module_notify(struct notifier_block *self,
-                             unsigned long val, void *data)
+static int tracepoint_module_notify(struct notifier_block *self,
+                unsigned long val, void *data)
 {
         struct module *mod = data;
         int ret = 0;
@@ -535,24 +431,58 @@ int tracepoint_module_notify(struct notifier_block *self,
         case MODULE_STATE_LIVE:
                 break;
         case MODULE_STATE_GOING:
-                ret = tracepoint_module_going(mod);
+                tracepoint_module_going(mod);
+                break;
+        case MODULE_STATE_UNFORMED:
                 break;
         }
         return ret;
 }
 
-struct notifier_block tracepoint_module_nb = {
+static struct notifier_block tracepoint_module_nb = {
         .notifier_call = tracepoint_module_notify,
         .priority = 0,
 };
 
-static int init_tracepoints(void)
+static __init int init_tracepoints(void)
 {
-        return register_module_notifier(&tracepoint_module_nb);
+        int ret;
+
+        ret = register_module_notifier(&tracepoint_module_nb);
+        if (ret)
+                pr_warning("Failed to register tracepoint module enter notifier\n");
+
+        return ret;
 }
 __initcall(init_tracepoints);
 #endif /* CONFIG_MODULES */
 
+static void for_each_tracepoint_range(struct tracepoint * const *begin,
+                struct tracepoint * const *end,
+                void (*fct)(struct tracepoint *tp, void *priv),
+                void *priv)
+{
+        struct tracepoint * const *iter;
+
+        if (!begin)
+                return;
+        for (iter = begin; iter < end; iter++)
+                fct(*iter, priv);
+}
+
+/**
+ * for_each_kernel_tracepoint - iteration on all kernel tracepoints
+ * @fct: callback
+ * @priv: private data
+ */
+void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
+                void *priv)
+{
+        for_each_tracepoint_range(__start___tracepoints_ptrs,
+                __stop___tracepoints_ptrs, fct, priv);
+}
+EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
+
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 
 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */