+/*
+ * Copyright (C) 2008 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
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/jhash.h>
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+#include <linux/tracepoint.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/immediate.h>
+
+extern struct tracepoint __start___tracepoints[];
+extern struct tracepoint __stop___tracepoints[];
+
+/* Set to 1 to enable tracepoint debug output */
+static const int tracepoint_debug;
+
+/*
+ * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
+ * builtin and module tracepoints and the hash table.
+ */
+static DEFINE_MUTEX(tracepoints_mutex);
+
+/*
+ * Tracepoint hash table, containing the active tracepoints.
+ * Protected by tracepoints_mutex.
+ */
+#define TRACEPOINT_HASH_BITS 6
+#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
+static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+
+/*
+ * Note about RCU :
+ * It is used to 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;
+ void **funcs;
+ int refcount; /* Number of times armed. 0 if disarmed. */
+ char name[0];
+};
+
+struct tp_probes {
+ union {
+ struct rcu_head rcu;
+ struct list_head list;
+ } u;
+ void *probes[0];
+};
+
+static inline void *allocate_probes(int count)
+{
+ struct tp_probes *p = kmalloc(count * sizeof(void *)
+ + sizeof(struct tp_probes), GFP_KERNEL);
+ return p == NULL ? NULL : p->probes;
+}
+
+static void rcu_free_old_probes(struct rcu_head *head)
+{
+ kfree(container_of(head, struct tp_probes, u.rcu));
+}
+
+static inline void release_probes(void *old)
+{
+ if (old) {
+ struct tp_probes *tp_probes = container_of(old,
+ struct tp_probes, probes[0]);
+ call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
+ }
+}
+
+static void debug_print_probes(struct tracepoint_entry *entry)
+{
+ int i;
+
+ if (!tracepoint_debug || !entry->funcs)
+ return;
+
+ for (i = 0; entry->funcs[i]; i++)
+ printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i]);
+}
+
+static void *
+tracepoint_entry_add_probe(struct tracepoint_entry *entry, void *probe)
+{
+ int nr_probes = 0;
+ void **old, **new;
+
+ WARN_ON(!probe);
+
+ debug_print_probes(entry);
+ old = entry->funcs;
+ if (old) {
+ /* (N -> N+1), (N != 0, 1) probes */
+ for (nr_probes = 0; old[nr_probes]; nr_probes++)
+ if (old[nr_probes] == probe)
+ return ERR_PTR(-EEXIST);
+ }
+ /* + 2 : one for new probe, one for NULL func */
+ new = allocate_probes(nr_probes + 2);
+ if (new == NULL)
+ return ERR_PTR(-ENOMEM);
+ if (old)
+ memcpy(new, old, nr_probes * sizeof(void *));
+ new[nr_probes] = probe;
+ new[nr_probes + 1] = NULL;
+ entry->refcount = nr_probes + 1;
+ entry->funcs = new;
+ debug_print_probes(entry);
+ return old;
+}
+
+static void *
+tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe)
+{
+ int nr_probes = 0, nr_del = 0, i;
+ void **old, **new;
+
+ old = entry->funcs;
+
+ if (!old)
+ return ERR_PTR(-ENOENT);
+
+ debug_print_probes(entry);
+ /* (N -> M), (N > 1, M >= 0) probes */
+ for (nr_probes = 0; old[nr_probes]; nr_probes++) {
+ if ((!probe || old[nr_probes] == probe))
+ nr_del++;
+ }
+
+ if (nr_probes - nr_del == 0) {
+ /* N -> 0, (N > 1) */
+ entry->funcs = NULL;
+ entry->refcount = 0;
+ debug_print_probes(entry);
+ return old;
+ } else {
+ int j = 0;
+ /* N -> M, (N > 1, M > 0) */
+ /* + 1 for NULL */
+ new = allocate_probes(nr_probes - nr_del + 1);
+ if (new == NULL)
+ return ERR_PTR(-ENOMEM);
+ for (i = 0; old[i]; i++)
+ if ((probe && old[i] != probe))
+ new[j++] = old[i];
+ new[nr_probes - nr_del] = NULL;
+ entry->refcount = nr_probes - nr_del;
+ entry->funcs = new;
+ }
+ debug_print_probes(entry);
+ 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.
+ */
+static struct tracepoint_entry *get_tracepoint(const char *name)
+{
+ struct hlist_head *head;
+ struct hlist_node *node;
+ struct tracepoint_entry *e;
+ u32 hash = jhash(name, strlen(name), 0);
+
+ head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
+ hlist_for_each_entry(e, node, head, hlist) {
+ if (!strcmp(name, e->name))
+ return e;
+ }
+ return NULL;
+}
+
+/*
+ * 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 hlist_node *node;
+ 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, node, 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;
+ hlist_add_head(&e->hlist, head);
+ return e;
+}
+
+/*
+ * 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);
+
+ /*
+ * rcu_assign_pointer has a smp_wmb() which makes sure that the new
+ * probe callbacks array is consistent before setting a pointer to it.
+ * This array is referenced by __DO_TRACE from
+ * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
+ * is used.
+ */
+ rcu_assign_pointer(elem->funcs, (*entry)->funcs);
+ elem->state__imv = active;
+}
+
+/*
+ * Disable a tracepoint and its probe callback.
+ * 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)
+{
+ elem->state__imv = 0;
+ rcu_assign_pointer(elem->funcs, NULL);
+}
+
+/**
+ * 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.
+ */
+void tracepoint_update_probe_range(struct tracepoint *begin,
+ struct tracepoint *end)
+{
+ struct tracepoint *iter;
+ struct tracepoint_entry *mark_entry;
+
+ mutex_lock(&tracepoints_mutex);
+ for (iter = begin; iter < end; iter++) {
+ mark_entry = get_tracepoint(iter->name);
+ if (mark_entry) {
+ set_tracepoint(&mark_entry, iter,
+ !!mark_entry->refcount);
+ } else {
+ disable_tracepoint(iter);
+ }
+ }
+ mutex_unlock(&tracepoints_mutex);
+}
+
+/*
+ * Update probes, removing the faulty probes.
+ */
+static void tracepoint_update_probes(void)
+{
+ /* Core kernel tracepoints */
+ tracepoint_update_probe_range(__start___tracepoints,
+ __stop___tracepoints);
+ /* tracepoints in modules. */
+ module_update_tracepoints();
+ /* Update immediate values */
+ core_imv_update();
+ module_imv_update();
+}
+
+static void *tracepoint_add_probe(const char *name, void *probe)
+{
+ struct tracepoint_entry *entry;
+ void *old;
+
+ entry = get_tracepoint(name);
+ if (!entry) {
+ entry = add_tracepoint(name);
+ if (IS_ERR(entry))
+ return entry;
+ }
+ old = tracepoint_entry_add_probe(entry, probe);
+ if (IS_ERR(old) && !entry->refcount)
+ remove_tracepoint(entry);
+ return old;
+}
+
+/**
+ * tracepoint_probe_register - Connect a probe to a tracepoint
+ * @name: tracepoint name
+ * @probe: probe handler
+ *
+ * Returns 0 if ok, error value on error.
+ * The probe address must at least be aligned on the architecture pointer size.
+ */
+int tracepoint_probe_register(const char *name, void *probe)
+{
+ void *old;
+
+ mutex_lock(&tracepoints_mutex);
+ old = tracepoint_add_probe(name, probe);
+ mutex_unlock(&tracepoints_mutex);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+
+ tracepoint_update_probes(); /* may update entry */
+ release_probes(old);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_register);
+
+static void *tracepoint_remove_probe(const char *name, void *probe)
+{
+ struct tracepoint_entry *entry;
+ void *old;
+
+ entry = get_tracepoint(name);
+ if (!entry)
+ return ERR_PTR(-ENOENT);
+ old = tracepoint_entry_remove_probe(entry, probe);
+ 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
+ * @probe: probe function pointer
+ *
+ * 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.
+ */
+int tracepoint_probe_unregister(const char *name, void *probe)
+{
+ void *old;
+
+ mutex_lock(&tracepoints_mutex);
+ old = tracepoint_remove_probe(name, probe);
+ mutex_unlock(&tracepoints_mutex);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+
+ tracepoint_update_probes(); /* may update entry */
+ release_probes(old);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
+
+static LIST_HEAD(old_probes);
+static int need_update;
+
+static void tracepoint_add_old_probes(void *old)
+{
+ need_update = 1;
+ if (old) {
+ struct tp_probes *tp_probes = container_of(old,
+ struct tp_probes, probes[0]);
+ list_add(&tp_probes->u.list, &old_probes);
+ }
+}
+
+/**
+ * tracepoint_probe_register_noupdate - register a probe but not connect
+ * @name: tracepoint name
+ * @probe: probe handler
+ *
+ * caller must call tracepoint_probe_update_all()
+ */
+int tracepoint_probe_register_noupdate(const char *name, void *probe)
+{
+ void *old;
+
+ mutex_lock(&tracepoints_mutex);
+ old = tracepoint_add_probe(name, probe);
+ if (IS_ERR(old)) {
+ mutex_unlock(&tracepoints_mutex);
+ return PTR_ERR(old);
+ }
+ tracepoint_add_old_probes(old);
+ mutex_unlock(&tracepoints_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
+
+/**
+ * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
+ * @name: tracepoint name
+ * @probe: probe function pointer
+ *
+ * caller must call tracepoint_probe_update_all()
+ */
+int tracepoint_probe_unregister_noupdate(const char *name, void *probe)
+{
+ void *old;
+
+ mutex_lock(&tracepoints_mutex);
+ old = tracepoint_remove_probe(name, probe);
+ if (IS_ERR(old)) {
+ mutex_unlock(&tracepoints_mutex);
+ return PTR_ERR(old);
+ }
+ tracepoint_add_old_probes(old);
+ mutex_unlock(&tracepoints_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
+
+/**
+ * tracepoint_probe_update_all - update tracepoints
+ */
+void tracepoint_probe_update_all(void)
+{
+ LIST_HEAD(release_probes);
+ struct tp_probes *pos, *next;
+
+ mutex_lock(&tracepoints_mutex);
+ if (!need_update) {
+ mutex_unlock(&tracepoints_mutex);
+ return;
+ }
+ if (!list_empty(&old_probes))
+ list_replace_init(&old_probes, &release_probes);
+ need_update = 0;
+ mutex_unlock(&tracepoints_mutex);
+
+ tracepoint_update_probes();
+ list_for_each_entry_safe(pos, next, &release_probes, u.list) {
+ list_del(&pos->u.list);
+ call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
+ }
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
+
+/**
+ * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
+ * @tracepoint: current tracepoints (in), next tracepoint (out)
+ * @begin: beginning of the range
+ * @end: end of the range
+ *
+ * Returns whether a next tracepoint has been found (1) or not (0).
+ * Will return the first tracepoint in the range if the input tracepoint is
+ * NULL.
+ */
+int tracepoint_get_iter_range(struct tracepoint **tracepoint,
+ struct tracepoint *begin, struct tracepoint *end)
+{
+ if (!*tracepoint && begin != end) {
+ *tracepoint = begin;
+ return 1;
+ }
+ if (*tracepoint >= begin && *tracepoint < end)
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
+
+static void tracepoint_get_iter(struct tracepoint_iter *iter)
+{
+ int found = 0;
+
+ /* Core kernel tracepoints */
+ if (!iter->module) {
+ found = tracepoint_get_iter_range(&iter->tracepoint,
+ __start___tracepoints, __stop___tracepoints);
+ if (found)
+ goto end;
+ }
+ /* tracepoints in modules. */
+ found = module_get_iter_tracepoints(iter);
+end:
+ if (!found)
+ tracepoint_iter_reset(iter);
+}
+
+void tracepoint_iter_start(struct tracepoint_iter *iter)
+{
+ tracepoint_get_iter(iter);
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_start);
+
+void tracepoint_iter_next(struct tracepoint_iter *iter)
+{
+ iter->tracepoint++;
+ /*
+ * iter->tracepoint may be invalid because we blindly incremented it.
+ * Make sure it is valid by marshalling on the tracepoints, getting the
+ * tracepoints from following modules if necessary.
+ */
+ tracepoint_get_iter(iter);
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_next);
+
+void tracepoint_iter_stop(struct tracepoint_iter *iter)
+{
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
+
+void tracepoint_iter_reset(struct tracepoint_iter *iter)
+{
+ iter->module = NULL;
+ iter->tracepoint = NULL;
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
+
+#ifdef CONFIG_MODULES
+
+int tracepoint_module_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct module *mod = data;
+
+ switch (val) {
+ case MODULE_STATE_COMING:
+ tracepoint_update_probe_range(mod->tracepoints,
+ mod->tracepoints + mod->num_tracepoints);
+ break;
+ case MODULE_STATE_GOING:
+ tracepoint_update_probe_range(mod->tracepoints,
+ mod->tracepoints + mod->num_tracepoints);
+ break;
+ }
+ return 0;
+}
+
+struct notifier_block tracepoint_module_nb = {
+ .notifier_call = tracepoint_module_notify,
+ .priority = 0,
+};
+
+static int init_tracepoints(void)
+{
+ return register_module_notifier(&tracepoint_module_nb);
+}
+__initcall(init_tracepoints);
+
+#endif /* CONFIG_MODULES */
projects / lttng-ust.git / commitdiff
