1 files changed, 520 insertions, 0 deletions
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
new file mode 100644
index 000000000..3490407dc
--- /dev/null
+++ b/kernel/tracepoint.c
@@ -0,0 +1,520 @@
+/*
+ * 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
+ * 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;
+
+#ifdef CONFIG_MODULES
+/*
+ * Tracepoint module list mutex protects the local module list.
+ */
+static DEFINE_MUTEX(tracepoint_module_list_mutex);
+
+/* Local list of struct tp_module */
+static LIST_HEAD(tracepoint_module_list);
+#endif /* CONFIG_MODULES */
+
+/*
+ * tracepoints_mutex protects the builtin and module tracepoints.
+ * tracepoints_mutex nests inside tracepoint_module_list_mutex.
+ */
+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.
+ */
+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_func *funcs)
+{
+	int i;
+
+	if (!tracepoint_debug || !funcs)
+		return;
+
+	for (i = 0; funcs[i].func; i++)
+		printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
+}
+
+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(!tp_func->func))
+		return ERR_PTR(-EINVAL);
+
+	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 == tp_func->func &&
+			    old[nr_probes].data == tp_func->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] = *tp_func;
+	new[nr_probes + 1].func = NULL;
+	*funcs = new;
+	debug_print_probes(*funcs);
+	return old;
+}
+
+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 = *funcs;
+
+	if (!old)
+		return ERR_PTR(-ENOENT);
+
+	debug_print_probes(*funcs);
+	/* (N -> M), (N > 1, M >= 0) probes */
+	if (tp_func->func) {
+		for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+			if (old[nr_probes].func == tp_func->func &&
+			     old[nr_probes].data == tp_func->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) */
+		*funcs = NULL;
+		debug_print_probes(*funcs);
+		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 != tp_func->func
+					|| old[i].data != tp_func->data)
+				new[j++] = old[i];
+		new[nr_probes - nr_del].func = NULL;
+		*funcs = new;
+	}
+	debug_print_probes(*funcs);
+	return old;
+}
+
+/*
+ * Add the probe function to a tracepoint.
+ */
+static int tracepoint_add_func(struct tracepoint *tp,
+		struct tracepoint_func *func)
+{
+	struct tracepoint_func *old, *tp_funcs;
+
+	if (tp->regfunc && !static_key_enabled(&tp->key))
+		tp->regfunc();
+
+	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);
+	}
+
+	/*
+	 * 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(tp->funcs, tp_funcs);
+	if (!static_key_enabled(&tp->key))
+		static_key_slow_inc(&tp->key);
+	release_probes(old);
+	return 0;
+}
+
+/*
+ * 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 int tracepoint_remove_func(struct tracepoint *tp,
+		struct tracepoint_func *func)
+{
+	struct tracepoint_func *old, *tp_funcs;
+
+	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);
+	}
+
+	if (!tp_funcs) {
+		/* Removed last function */
+		if (tp->unregfunc && static_key_enabled(&tp->key))
+			tp->unregfunc();
+
+		if (static_key_enabled(&tp->key))
+			static_key_slow_dec(&tp->key);
+	}
+	rcu_assign_pointer(tp->funcs, tp_funcs);
+	release_probes(old);
+	return 0;
+}
+
+/**
+ * tracepoint_probe_register -  Connect a probe to a tracepoint
+ * @tp: tracepoint
+ * @probe: probe handler
+ * @data: tracepoint data
+ *
+ * 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(struct tracepoint *tp, void *probe, void *data)
+{
+	struct tracepoint_func tp_func;
+	int ret;
+
+	mutex_lock(&tracepoints_mutex);
+	tp_func.func = probe;
+	tp_func.data = data;
+	ret = tracepoint_add_func(tp, &tp_func);
+	mutex_unlock(&tracepoints_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_register);
+
+/**
+ * tracepoint_probe_unregister -  Disconnect a probe from a tracepoint
+ * @tp: tracepoint
+ * @probe: probe function pointer
+ * @data: tracepoint data
+ *
+ * Returns 0 if ok, error value on error.
+ */
+int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
+{
+	struct tracepoint_func tp_func;
+	int ret;
+
+	mutex_lock(&tracepoints_mutex);
+	tp_func.func = probe;
+	tp_func.data = data;
+	ret = tracepoint_remove_func(tp, &tp_func);
+	mutex_unlock(&tracepoints_mutex);
+	return ret;
+}
+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 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;
+	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(&tracepoint_module_list_mutex);
+	tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
+	if (!tp_mod) {
+		ret = -ENOMEM;
+		goto end;
+	}
+	tp_mod->mod = mod;
+	list_add_tail(&tp_mod->list, &tracepoint_module_list);
+	blocking_notifier_call_chain(&tracepoint_notify_list,
+			MODULE_STATE_COMING, tp_mod);
+end:
+	mutex_unlock(&tracepoint_module_list_mutex);
+	return ret;
+}
+
+static void tracepoint_module_going(struct module *mod)
+{
+	struct tp_module *tp_mod;
+
+	if (!mod->num_tracepoints)
+		return;
+
+	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;
+		}
+	}
+	/*
+	 * 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(&tracepoint_module_list_mutex);
+}
+
+static 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:
+		tracepoint_module_going(mod);
+		break;
+	case MODULE_STATE_UNFORMED:
+		break;
+	}
+	return ret;
+}
+
+static struct notifier_block tracepoint_module_nb = {
+	.notifier_call = tracepoint_module_notify,
+	.priority = 0,
+};
+
+static __init int init_tracepoints(void)
+{
+	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 */
+static int sys_tracepoint_refcount;
+
+void syscall_regfunc(void)
+{
+	struct task_struct *p, *t;
+
+	if (!sys_tracepoint_refcount) {
+		read_lock(&tasklist_lock);
+		for_each_process_thread(p, t) {
+			set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
+		}
+		read_unlock(&tasklist_lock);
+	}
+	sys_tracepoint_refcount++;
+}
+
+void syscall_unregfunc(void)
+{
+	struct task_struct *p, *t;
+
+	sys_tracepoint_refcount--;
+	if (!sys_tracepoint_refcount) {
+		read_lock(&tasklist_lock);
+		for_each_process_thread(p, t) {
+			clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
+		}
+		read_unlock(&tasklist_lock);
+	}
+}
+#endif