kernel/tracepoint.c - kernel/msm-4.9 - Gitiles

 /*
  * 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/sched.h>
 #include <linux/static_key.h>

 extern struct tracepoint * const __start___tracepoints_ptrs[];
 extern struct tracepoint * const __stop___tracepoints_ptrs[];

 /* Set to 1 to enable tracepoint debug output */
 static const int tracepoint_debug;

 /*
  * Tracepoints mutex protects the builtin and module tracepoints and the hash
  * table, as well as the local module list.
  */
 static DEFINE_MUTEX(tracepoints_mutex);

 #ifdef CONFIG_MODULES
 /* Local list of struct module */
 static LIST_HEAD(tracepoint_module_list);
 #endif /* CONFIG_MODULES */

 /*
  * 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 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];
 };

 static inline void *allocate_probes(int count)
 {
 	struct tp_probes *p  = kmalloc(count * sizeof(struct tracepoint_func)
 			+ 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, rcu));
 }

 static inline void release_probes(struct tracepoint_func *old)
 {
 	if (old) {
 		struct tp_probes *tp_probes = container_of(old,
 			struct tp_probes, probes[0]);
 		call_rcu_sched(&tp_probes->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].func; i++)
 		printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
 }

 static struct tracepoint_func *
 tracepoint_entry_add_probe(struct tracepoint_entry *entry,
 			   void *probe, void *data)
 {
 	int nr_probes = 0;
 	struct tracepoint_func *old, *new;

 	if (WARN_ON(!probe))
 		return ERR_PTR(-EINVAL);

 	debug_print_probes(entry);
 	old = entry->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)
 				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(struct tracepoint_func));
 	new[nr_probes].func = probe;
 	new[nr_probes].data = data;
 	new[nr_probes + 1].func = 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, void *data)
 {
 	int nr_probes = 0, nr_del = 0, i;
 	struct tracepoint_func *old, *new;

 	old = entry->funcs;

 	if (!old)
 		return ERR_PTR(-ENOENT);

 	debug_print_probes(entry);
 	/* (N -> M), (N > 1, M >= 0) probes */
 	if (probe) {
 		for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
 			if (old[nr_probes].func == probe &&
 			     old[nr_probes].data == data)
 				nr_del++;
 		}
 	}

 	/*
 	 * If probe is NULL, then nr_probes = nr_del = 0, and then the
 	 * entire entry will be removed.
 	 */
 	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].func; i++)
 			if (old[i].func != probe || old[i].data != data)
 				new[j++] = old[i];
 		new[nr_probes - nr_del].func = 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 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;
 }

 /*
  * 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;
 }

 /*
  * 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();

 	/*
 	 * 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);
 	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);
 }

 /*
  * 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)
 {
 	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);
 }

 /**
  * 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);
 		}
 	}
 }

 #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 */


 /*
  * 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;
 	}
 	old = tracepoint_entry_add_probe(entry, probe, data);
 	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
  * @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.
  */
 int tracepoint_probe_register(const char *name, void *probe, void *data)
 {
 	struct tracepoint_func *old;
 	struct tracepoint_entry *entry;
 	int ret = 0;

 	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;
 	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
  * @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.
  */
 int tracepoint_probe_unregister(const char *name, void *probe, void *data)
 {
 	struct tracepoint_func *old;

 	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 */
 	mutex_unlock(&tracepoints_mutex);
 	release_probes(old);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);


 #ifdef CONFIG_MODULES
 bool trace_module_has_bad_taint(struct module *mod)
 {
 	return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
 			       (1 << TAINT_UNSIGNED_MODULE));
 }

 static int tracepoint_module_coming(struct module *mod)
 {
 	struct tp_module *tp_mod;
 	int ret = 0;

 	if (!mod->num_tracepoints)
 		return 0;

 	/*
 	 * We skip modules that taint the kernel, especially those with different
 	 * module headers (for forced load), to make sure we don't cause a crash.
 	 * Staging, out-of-tree, and unsigned GPL modules are fine.
 	 */
 	if (trace_module_has_bad_taint(mod))
 		return 0;
 	mutex_lock(&tracepoints_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;
 	list_add_tail(&tp_mod->list, &tracepoint_module_list);
 	tracepoint_update_probe_range(mod->tracepoints_ptrs,
 		mod->tracepoints_ptrs + mod->num_tracepoints);
 end:
 	mutex_unlock(&tracepoints_mutex);
 	return ret;
 }

 static int tracepoint_module_going(struct module *mod)
 {
 	struct tp_module *pos;

 	if (!mod->num_tracepoints)
 		return 0;

 	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);
 			break;
 		}
 	}
 	/*
 	 * In the case of modules that were tainted at "coming", we'll simply
 	 * walk through the list without finding it. We cannot use the "tainted"
 	 * flag on "going", in case a module taints the kernel only after being
 	 * loaded.
 	 */
 	mutex_unlock(&tracepoints_mutex);
 	return 0;
 }

 int tracepoint_module_notify(struct notifier_block *self,
 			     unsigned long val, void *data)
 {
 	struct module *mod = data;
 	int ret = 0;

 	switch (val) {
 	case MODULE_STATE_COMING:
 		ret = tracepoint_module_coming(mod);
 		break;
 	case MODULE_STATE_LIVE:
 		break;
 	case MODULE_STATE_GOING:
 		ret = tracepoint_module_going(mod);
 		break;
 	}
 	return ret;
 }

 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 */

 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS

 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 static int sys_tracepoint_refcount;

 void syscall_regfunc(void)
 {
 	unsigned long flags;
 	struct task_struct *g, *t;

 	if (!sys_tracepoint_refcount) {
 		read_lock_irqsave(&tasklist_lock, flags);
 		do_each_thread(g, t) {
 			/* Skip kernel threads. */
 			if (t->mm)
 				set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 		} while_each_thread(g, t);
 		read_unlock_irqrestore(&tasklist_lock, flags);
 	}
 	sys_tracepoint_refcount++;
 }

 void syscall_unregfunc(void)
 {
 	unsigned long flags;
 	struct task_struct *g, *t;

 	sys_tracepoint_refcount--;
 	if (!sys_tracepoint_refcount) {
 		read_lock_irqsave(&tasklist_lock, flags);
 		do_each_thread(g, t) {
 			clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 		} while_each_thread(g, t);
 		read_unlock_irqrestore(&tasklist_lock, flags);
 	}
 }
 #endif
	/*
	* 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/sched.h>
	#include <linux/static_key.h>

	extern struct tracepoint * const __start___tracepoints_ptrs[];
	extern struct tracepoint * const __stop___tracepoints_ptrs[];

	/* Set to 1 to enable tracepoint debug output */
	static const int tracepoint_debug;

	/*
	* Tracepoints mutex protects the builtin and module tracepoints and the hash
	* table, as well as the local module list.
	*/
	static DEFINE_MUTEX(tracepoints_mutex);

	#ifdef CONFIG_MODULES
	/* Local list of struct module */
	static LIST_HEAD(tracepoint_module_list);
	#endif /* CONFIG_MODULES */

	/*
	* 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 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];
	};

	static inline void *allocate_probes(int count)
	{
	struct tp_probes p = kmalloc(count sizeof(struct tracepoint_func)
	+ 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, rcu));
	}

	static inline void release_probes(struct tracepoint_func *old)
	{
	if (old) {
	struct tp_probes *tp_probes = container_of(old,
	struct tp_probes, probes[0]);
	call_rcu_sched(&tp_probes->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].func; i++)
	printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
	}

	static struct tracepoint_func *
	tracepoint_entry_add_probe(struct tracepoint_entry *entry,
	void probe, void data)
	{
	int nr_probes = 0;
	struct tracepoint_func old, new;

	if (WARN_ON(!probe))
	return ERR_PTR(-EINVAL);

	debug_print_probes(entry);
	old = entry->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)
	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(struct tracepoint_func));
	new[nr_probes].func = probe;
	new[nr_probes].data = data;
	new[nr_probes + 1].func = 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, void data)
	{
	int nr_probes = 0, nr_del = 0, i;
	struct tracepoint_func old, new;

	old = entry->funcs;

	if (!old)
	return ERR_PTR(-ENOENT);

	debug_print_probes(entry);
	/* (N -> M), (N > 1, M >= 0) probes */
	if (probe) {
	for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
	if (old[nr_probes].func == probe &&
	old[nr_probes].data == data)
	nr_del++;
	}
	}

	/*
	* If probe is NULL, then nr_probes = nr_del = 0, and then the
	* entire entry will be removed.
	*/
	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].func; i++)
	if (old[i].func != probe \|\| old[i].data != data)
	new[j++] = old[i];
	new[nr_probes - nr_del].func = 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 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;
	}

	/*
	* 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;
	}

	/*
	* 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();

	/*
	* 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);
	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);
	}

	/*
	* 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)
	{
	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);
	}

	/**
	* 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);
	}
	}
	}

	#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 */


	/*
	* 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;
	}
	old = tracepoint_entry_add_probe(entry, probe, data);
	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
	* @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.
	*/
	int tracepoint_probe_register(const char name, void probe, void *data)
	{
	struct tracepoint_func *old;
	struct tracepoint_entry *entry;
	int ret = 0;

	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;
	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
	* @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.
	*/
	int tracepoint_probe_unregister(const char name, void probe, void *data)
	{
	struct tracepoint_func *old;

	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 */
	mutex_unlock(&tracepoints_mutex);
	release_probes(old);
	return 0;
	}
	EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);


	#ifdef CONFIG_MODULES
	bool trace_module_has_bad_taint(struct module *mod)
	{
	return mod->taints & ~((1 << TAINT_OOT_MODULE) \| (1 << TAINT_CRAP) \|
	(1 << TAINT_UNSIGNED_MODULE));
	}

	static int tracepoint_module_coming(struct module *mod)
	{
	struct tp_module *tp_mod;
	int ret = 0;

	if (!mod->num_tracepoints)
	return 0;

	/*
	* We skip modules that taint the kernel, especially those with different
	* module headers (for forced load), to make sure we don't cause a crash.
	* Staging, out-of-tree, and unsigned GPL modules are fine.
	*/
	if (trace_module_has_bad_taint(mod))
	return 0;
	mutex_lock(&tracepoints_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;
	list_add_tail(&tp_mod->list, &tracepoint_module_list);
	tracepoint_update_probe_range(mod->tracepoints_ptrs,
	mod->tracepoints_ptrs + mod->num_tracepoints);
	end:
	mutex_unlock(&tracepoints_mutex);
	return ret;
	}

	static int tracepoint_module_going(struct module *mod)
	{
	struct tp_module *pos;

	if (!mod->num_tracepoints)
	return 0;

	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);
	break;
	}
	}
	/*
	* In the case of modules that were tainted at "coming", we'll simply
	* walk through the list without finding it. We cannot use the "tainted"
	* flag on "going", in case a module taints the kernel only after being
	* loaded.
	*/
	mutex_unlock(&tracepoints_mutex);
	return 0;
	}

	int tracepoint_module_notify(struct notifier_block *self,
	unsigned long val, void *data)
	{
	struct module *mod = data;
	int ret = 0;

	switch (val) {
	case MODULE_STATE_COMING:
	ret = tracepoint_module_coming(mod);
	break;
	case MODULE_STATE_LIVE:
	break;
	case MODULE_STATE_GOING:
	ret = tracepoint_module_going(mod);
	break;
	}
	return ret;
	}

	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 */

	#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS

	/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
	static int sys_tracepoint_refcount;

	void syscall_regfunc(void)
	{
	unsigned long flags;
	struct task_struct g, t;

	if (!sys_tracepoint_refcount) {
	read_lock_irqsave(&tasklist_lock, flags);
	do_each_thread(g, t) {
	/* Skip kernel threads. */
	if (t->mm)
	set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
	} while_each_thread(g, t);
	read_unlock_irqrestore(&tasklist_lock, flags);
	}
	sys_tracepoint_refcount++;
	}

	void syscall_unregfunc(void)
	{
	unsigned long flags;
	struct task_struct g, t;

	sys_tracepoint_refcount--;
	if (!sys_tracepoint_refcount) {
	read_lock_irqsave(&tasklist_lock, flags);
	do_each_thread(g, t) {
	clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
	} while_each_thread(g, t);
	read_unlock_irqrestore(&tasklist_lock, flags);
	}
	}
	#endif