4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5 * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
8 #include <linux/memory.h>
9 #include <linux/uaccess.h>
10 #include <linux/module.h>
11 #include <linux/list.h>
12 #include <linux/slab.h>
13 #include <linux/sort.h>
14 #include <linux/err.h>
15 #include <linux/static_key.h>
17 #ifdef HAVE_JUMP_LABEL
19 /* mutex to protect coming/going of the the jump_label table */
20 static DEFINE_MUTEX(jump_label_mutex);
22 void jump_label_lock(void)
24 mutex_lock(&jump_label_mutex);
27 void jump_label_unlock(void)
29 mutex_unlock(&jump_label_mutex);
32 static int jump_label_cmp(const void *a, const void *b)
34 const struct jump_entry *jea = a;
35 const struct jump_entry *jeb = b;
37 if (jea->key < jeb->key)
40 if (jea->key > jeb->key)
47 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
51 size = (((unsigned long)stop - (unsigned long)start)
52 / sizeof(struct jump_entry));
53 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
56 static void jump_label_update(struct static_key *key, int enable);
58 void static_key_slow_inc(struct static_key *key)
60 if (atomic_inc_not_zero(&key->enabled))
64 if (atomic_read(&key->enabled) == 0) {
65 if (!jump_label_get_branch_default(key))
66 jump_label_update(key, JUMP_LABEL_ENABLE);
68 jump_label_update(key, JUMP_LABEL_DISABLE);
70 atomic_inc(&key->enabled);
73 EXPORT_SYMBOL_GPL(static_key_slow_inc);
75 static void __static_key_slow_dec(struct static_key *key,
76 unsigned long rate_limit, struct delayed_work *work)
78 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
79 WARN(atomic_read(&key->enabled) < 0,
80 "jump label: negative count!\n");
85 atomic_inc(&key->enabled);
86 schedule_delayed_work(work, rate_limit);
88 if (!jump_label_get_branch_default(key))
89 jump_label_update(key, JUMP_LABEL_DISABLE);
91 jump_label_update(key, JUMP_LABEL_ENABLE);
96 static void jump_label_update_timeout(struct work_struct *work)
98 struct static_key_deferred *key =
99 container_of(work, struct static_key_deferred, work.work);
100 __static_key_slow_dec(&key->key, 0, NULL);
103 void static_key_slow_dec(struct static_key *key)
105 __static_key_slow_dec(key, 0, NULL);
107 EXPORT_SYMBOL_GPL(static_key_slow_dec);
109 void static_key_slow_dec_deferred(struct static_key_deferred *key)
111 __static_key_slow_dec(&key->key, key->timeout, &key->work);
113 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
115 void jump_label_rate_limit(struct static_key_deferred *key,
119 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
121 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
123 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
125 if (entry->code <= (unsigned long)end &&
126 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
132 static int __jump_label_text_reserved(struct jump_entry *iter_start,
133 struct jump_entry *iter_stop, void *start, void *end)
135 struct jump_entry *iter;
138 while (iter < iter_stop) {
139 if (addr_conflict(iter, start, end))
148 * Update code which is definitely not currently executing.
149 * Architectures which need heavyweight synchronization to modify
150 * running code can override this to make the non-live update case
153 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
154 enum jump_label_type type)
156 arch_jump_label_transform(entry, type);
159 static void __jump_label_update(struct static_key *key,
160 struct jump_entry *entry,
161 struct jump_entry *stop, int enable)
163 for (; (entry < stop) &&
164 (entry->key == (jump_label_t)(unsigned long)key);
167 * entry->code set to 0 invalidates module init text sections
168 * kernel_text_address() verifies we are not in core kernel
169 * init code, see jump_label_invalidate_module_init().
171 if (entry->code && kernel_text_address(entry->code))
172 arch_jump_label_transform(entry, enable);
176 static enum jump_label_type jump_label_type(struct static_key *key)
178 bool true_branch = jump_label_get_branch_default(key);
179 bool state = static_key_enabled(key);
181 if ((!true_branch && state) || (true_branch && !state))
182 return JUMP_LABEL_ENABLE;
184 return JUMP_LABEL_DISABLE;
187 void __init jump_label_init(void)
189 struct jump_entry *iter_start = __start___jump_table;
190 struct jump_entry *iter_stop = __stop___jump_table;
191 struct static_key *key = NULL;
192 struct jump_entry *iter;
195 jump_label_sort_entries(iter_start, iter_stop);
197 for (iter = iter_start; iter < iter_stop; iter++) {
198 struct static_key *iterk;
200 iterk = (struct static_key *)(unsigned long)iter->key;
201 arch_jump_label_transform_static(iter, jump_label_type(iterk));
207 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
209 *((unsigned long *)&key->entries) += (unsigned long)iter;
210 #ifdef CONFIG_MODULES
217 #ifdef CONFIG_MODULES
219 struct static_key_mod {
220 struct static_key_mod *next;
221 struct jump_entry *entries;
225 static int __jump_label_mod_text_reserved(void *start, void *end)
229 mod = __module_text_address((unsigned long)start);
233 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
235 return __jump_label_text_reserved(mod->jump_entries,
236 mod->jump_entries + mod->num_jump_entries,
240 static void __jump_label_mod_update(struct static_key *key, int enable)
242 struct static_key_mod *mod = key->next;
245 struct module *m = mod->mod;
247 __jump_label_update(key, mod->entries,
248 m->jump_entries + m->num_jump_entries,
255 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
256 * @mod: module to patch
258 * Allow for run-time selection of the optimal nops. Before the module
259 * loads patch these with arch_get_jump_label_nop(), which is specified by
260 * the arch specific jump label code.
262 void jump_label_apply_nops(struct module *mod)
264 struct jump_entry *iter_start = mod->jump_entries;
265 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
266 struct jump_entry *iter;
268 /* if the module doesn't have jump label entries, just return */
269 if (iter_start == iter_stop)
272 for (iter = iter_start; iter < iter_stop; iter++) {
273 arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
277 static int jump_label_add_module(struct module *mod)
279 struct jump_entry *iter_start = mod->jump_entries;
280 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
281 struct jump_entry *iter;
282 struct static_key *key = NULL;
283 struct static_key_mod *jlm;
285 /* if the module doesn't have jump label entries, just return */
286 if (iter_start == iter_stop)
289 jump_label_sort_entries(iter_start, iter_stop);
291 for (iter = iter_start; iter < iter_stop; iter++) {
292 struct static_key *iterk;
294 iterk = (struct static_key *)(unsigned long)iter->key;
299 if (__module_address(iter->key) == mod) {
301 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
303 *((unsigned long *)&key->entries) += (unsigned long)iter;
307 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
312 jlm->next = key->next;
315 if (jump_label_type(key) == JUMP_LABEL_ENABLE)
316 __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE);
322 static void jump_label_del_module(struct module *mod)
324 struct jump_entry *iter_start = mod->jump_entries;
325 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
326 struct jump_entry *iter;
327 struct static_key *key = NULL;
328 struct static_key_mod *jlm, **prev;
330 for (iter = iter_start; iter < iter_stop; iter++) {
331 if (iter->key == (jump_label_t)(unsigned long)key)
334 key = (struct static_key *)(unsigned long)iter->key;
336 if (__module_address(iter->key) == mod)
342 while (jlm && jlm->mod != mod) {
354 static void jump_label_invalidate_module_init(struct module *mod)
356 struct jump_entry *iter_start = mod->jump_entries;
357 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
358 struct jump_entry *iter;
360 for (iter = iter_start; iter < iter_stop; iter++) {
361 if (within_module_init(iter->code, mod))
367 jump_label_module_notify(struct notifier_block *self, unsigned long val,
370 struct module *mod = data;
374 case MODULE_STATE_COMING:
376 ret = jump_label_add_module(mod);
378 jump_label_del_module(mod);
381 case MODULE_STATE_GOING:
383 jump_label_del_module(mod);
386 case MODULE_STATE_LIVE:
388 jump_label_invalidate_module_init(mod);
393 return notifier_from_errno(ret);
396 struct notifier_block jump_label_module_nb = {
397 .notifier_call = jump_label_module_notify,
398 .priority = 1, /* higher than tracepoints */
401 static __init int jump_label_init_module(void)
403 return register_module_notifier(&jump_label_module_nb);
405 early_initcall(jump_label_init_module);
407 #endif /* CONFIG_MODULES */
410 * jump_label_text_reserved - check if addr range is reserved
411 * @start: start text addr
412 * @end: end text addr
414 * checks if the text addr located between @start and @end
415 * overlaps with any of the jump label patch addresses. Code
416 * that wants to modify kernel text should first verify that
417 * it does not overlap with any of the jump label addresses.
418 * Caller must hold jump_label_mutex.
420 * returns 1 if there is an overlap, 0 otherwise
422 int jump_label_text_reserved(void *start, void *end)
424 int ret = __jump_label_text_reserved(__start___jump_table,
425 __stop___jump_table, start, end);
430 #ifdef CONFIG_MODULES
431 ret = __jump_label_mod_text_reserved(start, end);
436 static void jump_label_update(struct static_key *key, int enable)
438 struct jump_entry *stop = __stop___jump_table;
439 struct jump_entry *entry = jump_label_get_entries(key);
441 #ifdef CONFIG_MODULES
442 struct module *mod = __module_address((unsigned long)key);
444 __jump_label_mod_update(key, enable);
447 stop = mod->jump_entries + mod->num_jump_entries;
449 /* if there are no users, entry can be NULL */
451 __jump_label_update(key, entry, stop, enable);