1 files changed, 394 insertions, 0 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
new file mode 100644
index 00000000..e6f1f24a
--- /dev/null
+++ b/kernel/jump_label.c
@@ -0,0 +1,394 @@
+/*
+ * jump label support
+ *
+ * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
+ * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
+ *
+ */
+#include <linux/memory.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include <linux/err.h>
+#include <linux/jump_label.h>
+
+#ifdef HAVE_JUMP_LABEL
+
+/* mutex to protect coming/going of the the jump_label table */
+static DEFINE_MUTEX(jump_label_mutex);
+
+void jump_label_lock(void)
+{
+	mutex_lock(&jump_label_mutex);
+}
+
+void jump_label_unlock(void)
+{
+	mutex_unlock(&jump_label_mutex);
+}
+
+bool jump_label_enabled(struct jump_label_key *key)
+{
+	return !!atomic_read(&key->enabled);
+}
+
+static int jump_label_cmp(const void *a, const void *b)
+{
+	const struct jump_entry *jea = a;
+	const struct jump_entry *jeb = b;
+
+	if (jea->key < jeb->key)
+		return -1;
+
+	if (jea->key > jeb->key)
+		return 1;
+
+	return 0;
+}
+
+static void
+jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
+{
+	unsigned long size;
+
+	size = (((unsigned long)stop - (unsigned long)start)
+					/ sizeof(struct jump_entry));
+	sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
+}
+
+static void jump_label_update(struct jump_label_key *key, int enable);
+
+void jump_label_inc(struct jump_label_key *key)
+{
+	if (atomic_inc_not_zero(&key->enabled))
+		return;
+
+	jump_label_lock();
+	if (atomic_read(&key->enabled) == 0)
+		jump_label_update(key, JUMP_LABEL_ENABLE);
+	atomic_inc(&key->enabled);
+	jump_label_unlock();
+}
+
+void jump_label_dec(struct jump_label_key *key)
+{
+	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
+		return;
+
+	jump_label_update(key, JUMP_LABEL_DISABLE);
+	jump_label_unlock();
+}
+
+static int addr_conflict(struct jump_entry *entry, void *start, void *end)
+{
+	if (entry->code <= (unsigned long)end &&
+		entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
+		return 1;
+
+	return 0;
+}
+
+static int __jump_label_text_reserved(struct jump_entry *iter_start,
+		struct jump_entry *iter_stop, void *start, void *end)
+{
+	struct jump_entry *iter;
+
+	iter = iter_start;
+	while (iter < iter_stop) {
+		if (addr_conflict(iter, start, end))
+			return 1;
+		iter++;
+	}
+
+	return 0;
+}
+
+static void __jump_label_update(struct jump_label_key *key,
+				struct jump_entry *entry,
+				struct jump_entry *stop, int enable)
+{
+	for (; (entry < stop) &&
+	      (entry->key == (jump_label_t)(unsigned long)key);
+	      entry++) {
+		/*
+		 * entry->code set to 0 invalidates module init text sections
+		 * kernel_text_address() verifies we are not in core kernel
+		 * init code, see jump_label_invalidate_module_init().
+		 */
+		if (entry->code && kernel_text_address(entry->code))
+			arch_jump_label_transform(entry, enable);
+	}
+}
+
+/*
+ * Not all archs need this.
+ */
+void __weak arch_jump_label_text_poke_early(jump_label_t addr)
+{
+}
+
+static __init int jump_label_init(void)
+{
+	struct jump_entry *iter_start = __start___jump_table;
+	struct jump_entry *iter_stop = __stop___jump_table;
+	struct jump_label_key *key = NULL;
+	struct jump_entry *iter;
+
+	jump_label_lock();
+	jump_label_sort_entries(iter_start, iter_stop);
+
+	for (iter = iter_start; iter < iter_stop; iter++) {
+		arch_jump_label_text_poke_early(iter->code);
+		if (iter->key == (jump_label_t)(unsigned long)key)
+			continue;
+
+		key = (struct jump_label_key *)(unsigned long)iter->key;
+		atomic_set(&key->enabled, 0);
+		key->entries = iter;
+#ifdef CONFIG_MODULES
+		key->next = NULL;
+#endif
+	}
+	jump_label_unlock();
+
+	return 0;
+}
+early_initcall(jump_label_init);
+
+#ifdef CONFIG_MODULES
+
+struct jump_label_mod {
+	struct jump_label_mod *next;
+	struct jump_entry *entries;
+	struct module *mod;
+};
+
+static int __jump_label_mod_text_reserved(void *start, void *end)
+{
+	struct module *mod;
+
+	mod = __module_text_address((unsigned long)start);
+	if (!mod)
+		return 0;
+
+	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
+
+	return __jump_label_text_reserved(mod->jump_entries,
+				mod->jump_entries + mod->num_jump_entries,
+				start, end);
+}
+
+static void __jump_label_mod_update(struct jump_label_key *key, int enable)
+{
+	struct jump_label_mod *mod = key->next;
+
+	while (mod) {
+		struct module *m = mod->mod;
+
+		__jump_label_update(key, mod->entries,
+				    m->jump_entries + m->num_jump_entries,
+				    enable);
+		mod = mod->next;
+	}
+}
+
+/***
+ * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
+ * @mod: module to patch
+ *
+ * Allow for run-time selection of the optimal nops. Before the module
+ * loads patch these with arch_get_jump_label_nop(), which is specified by
+ * the arch specific jump label code.
+ */
+void jump_label_apply_nops(struct module *mod)
+{
+	struct jump_entry *iter_start = mod->jump_entries;
+	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
+	struct jump_entry *iter;
+
+	/* if the module doesn't have jump label entries, just return */
+	if (iter_start == iter_stop)
+		return;
+
+	for (iter = iter_start; iter < iter_stop; iter++)
+		arch_jump_label_text_poke_early(iter->code);
+}
+
+static int jump_label_add_module(struct module *mod)
+{
+	struct jump_entry *iter_start = mod->jump_entries;
+	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
+	struct jump_entry *iter;
+	struct jump_label_key *key = NULL;
+	struct jump_label_mod *jlm;
+
+	/* if the module doesn't have jump label entries, just return */
+	if (iter_start == iter_stop)
+		return 0;
+
+	jump_label_sort_entries(iter_start, iter_stop);
+
+	for (iter = iter_start; iter < iter_stop; iter++) {
+		if (iter->key == (jump_label_t)(unsigned long)key)
+			continue;
+
+		key = (struct jump_label_key *)(unsigned long)iter->key;
+
+		if (__module_address(iter->key) == mod) {
+			atomic_set(&key->enabled, 0);
+			key->entries = iter;
+			key->next = NULL;
+			continue;
+		}
+
+		jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
+		if (!jlm)
+			return -ENOMEM;
+
+		jlm->mod = mod;
+		jlm->entries = iter;
+		jlm->next = key->next;
+		key->next = jlm;
+
+		if (jump_label_enabled(key))
+			__jump_label_update(key, iter, iter_stop,
+					    JUMP_LABEL_ENABLE);
+	}
+
+	return 0;
+}
+
+static void jump_label_del_module(struct module *mod)
+{
+	struct jump_entry *iter_start = mod->jump_entries;
+	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
+	struct jump_entry *iter;
+	struct jump_label_key *key = NULL;
+	struct jump_label_mod *jlm, **prev;
+
+	for (iter = iter_start; iter < iter_stop; iter++) {
+		if (iter->key == (jump_label_t)(unsigned long)key)
+			continue;
+
+		key = (struct jump_label_key *)(unsigned long)iter->key;
+
+		if (__module_address(iter->key) == mod)
+			continue;
+
+		prev = &key->next;
+		jlm = key->next;
+
+		while (jlm && jlm->mod != mod) {
+			prev = &jlm->next;
+			jlm = jlm->next;
+		}
+
+		if (jlm) {
+			*prev = jlm->next;
+			kfree(jlm);
+		}
+	}
+}
+
+static void jump_label_invalidate_module_init(struct module *mod)
+{
+	struct jump_entry *iter_start = mod->jump_entries;
+	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
+	struct jump_entry *iter;
+
+	for (iter = iter_start; iter < iter_stop; iter++) {
+		if (within_module_init(iter->code, mod))
+			iter->code = 0;
+	}
+}
+
+static int
+jump_label_module_notify(struct notifier_block *self, unsigned long val,
+			 void *data)
+{
+	struct module *mod = data;
+	int ret = 0;
+
+	switch (val) {
+	case MODULE_STATE_COMING:
+		jump_label_lock();
+		ret = jump_label_add_module(mod);
+		if (ret)
+			jump_label_del_module(mod);
+		jump_label_unlock();
+		break;
+	case MODULE_STATE_GOING:
+		jump_label_lock();
+		jump_label_del_module(mod);
+		jump_label_unlock();
+		break;
+	case MODULE_STATE_LIVE:
+		jump_label_lock();
+		jump_label_invalidate_module_init(mod);
+		jump_label_unlock();
+		break;
+	}
+
+	return notifier_from_errno(ret);
+}
+
+struct notifier_block jump_label_module_nb = {
+	.notifier_call = jump_label_module_notify,
+	.priority = 1, /* higher than tracepoints */
+};
+
+static __init int jump_label_init_module(void)
+{
+	return register_module_notifier(&jump_label_module_nb);
+}
+early_initcall(jump_label_init_module);
+
+#endif /* CONFIG_MODULES */
+
+/***
+ * jump_label_text_reserved - check if addr range is reserved
+ * @start: start text addr
+ * @end: end text addr
+ *
+ * checks if the text addr located between @start and @end
+ * overlaps with any of the jump label patch addresses. Code
+ * that wants to modify kernel text should first verify that
+ * it does not overlap with any of the jump label addresses.
+ * Caller must hold jump_label_mutex.
+ *
+ * returns 1 if there is an overlap, 0 otherwise
+ */
+int jump_label_text_reserved(void *start, void *end)
+{
+	int ret = __jump_label_text_reserved(__start___jump_table,
+			__stop___jump_table, start, end);
+
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_MODULES
+	ret = __jump_label_mod_text_reserved(start, end);
+#endif
+	return ret;
+}
+
+static void jump_label_update(struct jump_label_key *key, int enable)
+{
+	struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
+
+#ifdef CONFIG_MODULES
+	struct module *mod = __module_address((jump_label_t)key);
+
+	__jump_label_mod_update(key, enable);
+
+	if (mod)
+		stop = mod->jump_entries + mod->num_jump_entries;
+#endif
+	/* if there are no users, entry can be NULL */
+	if (entry)
+		__jump_label_update(key, entry, stop, enable);
+}
+
+#endif