initial_commit

1 files changed, 640 insertions, 0 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
new file mode 100644
index 00000000..b219f144
--- /dev/null
+++ b/kernel/tracepoint.c
@@ -0,0 +1,640 @@
+/*
+ * 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/jump_label.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 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 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. */
+	char name[0];
+};
+
+struct tp_probes {
+	union {
+		struct rcu_head rcu;
+		struct list_head list;
+	} u;
+	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, u.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->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].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;
+
+	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].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 */
+	for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+		if (!probe ||
+		    (old[nr_probes].func == probe &&
+		     old[nr_probes].data == data))
+			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].func; i++)
+			if (probe &&
+			    (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 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);
+
+	if (elem->regfunc && !jump_label_enabled(&elem->key) && active)
+		elem->regfunc();
+	else if (elem->unregfunc && jump_label_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 && !jump_label_enabled(&elem->key))
+		jump_label_inc(&elem->key);
+	else if (!active && jump_label_enabled(&elem->key))
+		jump_label_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 && jump_label_enabled(&elem->key))
+		elem->unregfunc();
+
+	if (jump_label_enabled(&elem->key))
+		jump_label_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.
+ */
+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;
+
+	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_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
+ *
+ * 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 *data)
+{
+	struct tracepoint_func *old;
+
+	mutex_lock(&tracepoints_mutex);
+	old = tracepoint_add_probe(name, probe, data);
+	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 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
+ *
+ * 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);
+	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 *data)
+{
+	struct tracepoint_func *old;
+
+	mutex_lock(&tracepoints_mutex);
+	old = tracepoint_add_probe(name, probe, data);
+	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 *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_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 * const **tracepoint,
+	struct tracepoint * const *begin, struct tracepoint * const *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_ptrs,
+				__stop___tracepoints_ptrs);
+		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:
+	case MODULE_STATE_GOING:
+		tracepoint_update_probe_range(mod->tracepoints_ptrs,
+			mod->tracepoints_ptrs + 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 */
+
+#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