hung_task: fix false positive during vfork
[linux-2.6.git] / kernel / jump_label.c
index 460fd40..e6f1f24 100644 (file)
@@ -2,42 +2,37 @@
  * jump label support
  *
  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
+ * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
  *
  */
-#include <linux/jump_label.h>
 #include <linux/memory.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/list.h>
-#include <linux/jhash.h>
 #include <linux/slab.h>
 #include <linux/sort.h>
 #include <linux/err.h>
+#include <linux/jump_label.h>
 
 #ifdef HAVE_JUMP_LABEL
 
-#define JUMP_LABEL_HASH_BITS 6
-#define JUMP_LABEL_TABLE_SIZE (1 << JUMP_LABEL_HASH_BITS)
-static struct hlist_head jump_label_table[JUMP_LABEL_TABLE_SIZE];
-
 /* mutex to protect coming/going of the the jump_label table */
 static DEFINE_MUTEX(jump_label_mutex);
 
-struct jump_label_entry {
-       struct hlist_node hlist;
-       struct jump_entry *table;
-       int nr_entries;
-       /* hang modules off here */
-       struct hlist_head modules;
-       unsigned long key;
-};
+void jump_label_lock(void)
+{
+       mutex_lock(&jump_label_mutex);
+}
 
-struct jump_label_module_entry {
-       struct hlist_node hlist;
-       struct jump_entry *table;
-       int nr_entries;
-       struct module *mod;
-};
+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)
 {
@@ -54,7 +49,7 @@ static int jump_label_cmp(const void *a, const void *b)
 }
 
 static void
-sort_jump_label_entries(struct jump_entry *start, struct jump_entry *stop)
+jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
 {
        unsigned long size;
 
@@ -63,226 +58,252 @@ sort_jump_label_entries(struct jump_entry *start, struct jump_entry *stop)
        sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
 }
 
-static struct jump_label_entry *get_jump_label_entry(jump_label_t key)
+static void jump_label_update(struct jump_label_key *key, int enable);
+
+void jump_label_inc(struct jump_label_key *key)
 {
-       struct hlist_head *head;
-       struct hlist_node *node;
-       struct jump_label_entry *e;
-       u32 hash = jhash((void *)&key, sizeof(jump_label_t), 0);
-
-       head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
-       hlist_for_each_entry(e, node, head, hlist) {
-               if (key == e->key)
-                       return e;
-       }
-       return NULL;
+       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();
 }
 
-static struct jump_label_entry *
-add_jump_label_entry(jump_label_t key, int nr_entries, struct jump_entry *table)
+void jump_label_dec(struct jump_label_key *key)
 {
-       struct hlist_head *head;
-       struct jump_label_entry *e;
-       u32 hash;
-
-       e = get_jump_label_entry(key);
-       if (e)
-               return ERR_PTR(-EEXIST);
-
-       e = kmalloc(sizeof(struct jump_label_entry), GFP_KERNEL);
-       if (!e)
-               return ERR_PTR(-ENOMEM);
-
-       hash = jhash((void *)&key, sizeof(jump_label_t), 0);
-       head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
-       e->key = key;
-       e->table = table;
-       e->nr_entries = nr_entries;
-       INIT_HLIST_HEAD(&(e->modules));
-       hlist_add_head(&e->hlist, head);
-       return e;
+       if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
+               return;
+
+       jump_label_update(key, JUMP_LABEL_DISABLE);
+       jump_label_unlock();
 }
 
-static int
-build_jump_label_hashtable(struct jump_entry *start, struct jump_entry *stop)
+static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 {
-       struct jump_entry *iter, *iter_begin;
-       struct jump_label_entry *entry;
-       int count;
-
-       sort_jump_label_entries(start, stop);
-       iter = start;
-       while (iter < stop) {
-               entry = get_jump_label_entry(iter->key);
-               if (!entry) {
-                       iter_begin = iter;
-                       count = 0;
-                       while ((iter < stop) &&
-                               (iter->key == iter_begin->key)) {
-                               iter++;
-                               count++;
-                       }
-                       entry = add_jump_label_entry(iter_begin->key,
-                                                       count, iter_begin);
-                       if (IS_ERR(entry))
-                               return PTR_ERR(entry);
-                } else {
-                       WARN_ONCE(1, KERN_ERR "build_jump_hashtable: unexpected entry!\n");
-                       return -1;
-               }
-       }
+       if (entry->code <= (unsigned long)end &&
+               entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
+               return 1;
+
        return 0;
 }
 
-/***
- * jump_label_update - update jump label text
- * @key -  key value associated with a a jump label
- * @type - enum set to JUMP_LABEL_ENABLE or JUMP_LABEL_DISABLE
- *
- * Will enable/disable the jump for jump label @key, depending on the
- * value of @type.
- *
- */
-
-void jump_label_update(unsigned long key, enum jump_label_type type)
+static int __jump_label_text_reserved(struct jump_entry *iter_start,
+               struct jump_entry *iter_stop, void *start, void *end)
 {
        struct jump_entry *iter;
-       struct jump_label_entry *entry;
-       struct hlist_node *module_node;
-       struct jump_label_module_entry *e_module;
-       int count;
 
-       mutex_lock(&jump_label_mutex);
-       entry = get_jump_label_entry((jump_label_t)key);
-       if (entry) {
-               count = entry->nr_entries;
-               iter = entry->table;
-               while (count--) {
-                       if (kernel_text_address(iter->code))
-                               arch_jump_label_transform(iter, type);
-                       iter++;
-               }
-               /* eanble/disable jump labels in modules */
-               hlist_for_each_entry(e_module, module_node, &(entry->modules),
-                                                       hlist) {
-                       count = e_module->nr_entries;
-                       iter = e_module->table;
-                       while (count--) {
-                               if (kernel_text_address(iter->code))
-                                       arch_jump_label_transform(iter, type);
-                               iter++;
-                       }
-               }
+       iter = iter_start;
+       while (iter < iter_stop) {
+               if (addr_conflict(iter, start, end))
+                       return 1;
+               iter++;
        }
-       mutex_unlock(&jump_label_mutex);
+
+       return 0;
 }
 
-static __init int init_jump_label(void)
+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)
 {
-       int ret;
        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;
 
-       mutex_lock(&jump_label_mutex);
-       ret = build_jump_label_hashtable(__start___jump_table,
-                                        __stop___jump_table);
-       iter = iter_start;
-       while (iter < iter_stop) {
+       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);
-               iter++;
+               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
        }
-       mutex_unlock(&jump_label_mutex);
-       return ret;
+       jump_label_unlock();
+
+       return 0;
 }
-early_initcall(init_jump_label);
+early_initcall(jump_label_init);
 
 #ifdef CONFIG_MODULES
 
-static struct jump_label_module_entry *
-add_jump_label_module_entry(struct jump_label_entry *entry,
-                           struct jump_entry *iter_begin,
-                           int count, struct module *mod)
+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 jump_label_module_entry *e;
-
-       e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
-       if (!e)
-               return ERR_PTR(-ENOMEM);
-       e->mod = mod;
-       e->nr_entries = count;
-       e->table = iter_begin;
-       hlist_add_head(&e->hlist, &entry->modules);
-       return e;
+       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 int add_jump_label_module(struct module *mod)
+static void __jump_label_mod_update(struct jump_label_key *key, int enable)
 {
-       struct jump_entry *iter, *iter_begin;
-       struct jump_label_entry *entry;
-       struct jump_label_module_entry *module_entry;
-       int count;
+       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 (!mod->num_jump_entries)
+       if (iter_start == iter_stop)
                return 0;
 
-       sort_jump_label_entries(mod->jump_entries,
-                               mod->jump_entries + mod->num_jump_entries);
-       iter = mod->jump_entries;
-       while (iter < mod->jump_entries + mod->num_jump_entries) {
-               entry = get_jump_label_entry(iter->key);
-               iter_begin = iter;
-               count = 0;
-               while ((iter < mod->jump_entries + mod->num_jump_entries) &&
-                       (iter->key == iter_begin->key)) {
-                               iter++;
-                               count++;
-               }
-               if (!entry) {
-                       entry = add_jump_label_entry(iter_begin->key, 0, NULL);
-                       if (IS_ERR(entry))
-                               return PTR_ERR(entry);
+       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;
                }
-               module_entry = add_jump_label_module_entry(entry, iter_begin,
-                                                          count, mod);
-               if (IS_ERR(module_entry))
-                       return PTR_ERR(module_entry);
+
+               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 remove_jump_label_module(struct module *mod)
+static void jump_label_del_module(struct module *mod)
 {
-       struct hlist_head *head;
-       struct hlist_node *node, *node_next, *module_node, *module_node_next;
-       struct jump_label_entry *e;
-       struct jump_label_module_entry *e_module;
-       int i;
+       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;
 
-       /* if the module doesn't have jump label entries, just return */
-       if (!mod->num_jump_entries)
-               return;
+       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;
 
-       for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
-               head = &jump_label_table[i];
-               hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
-                       hlist_for_each_entry_safe(e_module, module_node,
-                                                 module_node_next,
-                                                 &(e->modules), hlist) {
-                               if (e_module->mod == mod) {
-                                       hlist_del(&e_module->hlist);
-                                       kfree(e_module);
-                               }
-                       }
-                       if (hlist_empty(&e->modules) && (e->nr_entries == 0)) {
-                               hlist_del(&e->hlist);
-                               kfree(e);
-                       }
+               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)
@@ -292,55 +313,82 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val,
 
        switch (val) {
        case MODULE_STATE_COMING:
-               mutex_lock(&jump_label_mutex);
-               ret = add_jump_label_module(mod);
+               jump_label_lock();
+               ret = jump_label_add_module(mod);
                if (ret)
-                       remove_jump_label_module(mod);
-               mutex_unlock(&jump_label_mutex);
+                       jump_label_del_module(mod);
+               jump_label_unlock();
                break;
        case MODULE_STATE_GOING:
-               mutex_lock(&jump_label_mutex);
-               remove_jump_label_module(mod);
-               mutex_unlock(&jump_label_mutex);
+               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 ret;
-}
-
-/***
- * 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;
-
-       /* if the module doesn't have jump label entries, just return */
-       if (!mod->num_jump_entries)
-               return;
 
-       iter = mod->jump_entries;
-       while (iter < mod->jump_entries + mod->num_jump_entries) {
-               arch_jump_label_text_poke_early(iter->code);
-               iter++;
-       }
+       return notifier_from_errno(ret);
 }
 
 struct notifier_block jump_label_module_nb = {
        .notifier_call = jump_label_module_notify,
-       .priority = 0,
+       .priority = 1, /* higher than tracepoints */
 };
 
-static __init int init_jump_label_module(void)
+static __init int jump_label_init_module(void)
 {
        return register_module_notifier(&jump_label_module_nb);
 }
-early_initcall(init_jump_label_module);
+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