| /* |
| * 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> |
| |
| 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 = 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 = 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; |
| |
| if (!begin) |
| return; |
| |
| 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(); |
| } |
| |
| 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 */ |