4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5 * Copyright (C) 2011 Peter Zijlstra
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>
16 #include <linux/jump_label_ratelimit.h>
18 #ifdef HAVE_JUMP_LABEL
20 /* mutex to protect coming/going of the the jump_label table */
21 static DEFINE_MUTEX(jump_label_mutex);
23 void jump_label_lock(void)
25 mutex_lock(&jump_label_mutex);
28 void jump_label_unlock(void)
30 mutex_unlock(&jump_label_mutex);
33 static int jump_label_cmp(const void *a, const void *b)
35 const struct jump_entry *jea = a;
36 const struct jump_entry *jeb = b;
38 if (jea->key < jeb->key)
41 if (jea->key > jeb->key)
48 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
52 size = (((unsigned long)stop - (unsigned long)start)
53 / sizeof(struct jump_entry));
54 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
57 static void jump_label_update(struct static_key *key);
59 void static_key_slow_inc(struct static_key *key)
61 STATIC_KEY_CHECK_USE();
62 if (atomic_inc_not_zero(&key->enabled))
66 if (atomic_inc_return(&key->enabled) == 1)
67 jump_label_update(key);
70 EXPORT_SYMBOL_GPL(static_key_slow_inc);
72 static void __static_key_slow_dec(struct static_key *key,
73 unsigned long rate_limit, struct delayed_work *work)
75 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
76 WARN(atomic_read(&key->enabled) < 0,
77 "jump label: negative count!\n");
82 atomic_inc(&key->enabled);
83 schedule_delayed_work(work, rate_limit);
85 jump_label_update(key);
90 static void jump_label_update_timeout(struct work_struct *work)
92 struct static_key_deferred *key =
93 container_of(work, struct static_key_deferred, work.work);
94 __static_key_slow_dec(&key->key, 0, NULL);
97 void static_key_slow_dec(struct static_key *key)
99 STATIC_KEY_CHECK_USE();
100 __static_key_slow_dec(key, 0, NULL);
102 EXPORT_SYMBOL_GPL(static_key_slow_dec);
104 void static_key_slow_dec_deferred(struct static_key_deferred *key)
106 STATIC_KEY_CHECK_USE();
107 __static_key_slow_dec(&key->key, key->timeout, &key->work);
109 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
111 void jump_label_rate_limit(struct static_key_deferred *key,
114 STATIC_KEY_CHECK_USE();
116 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
118 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
120 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
122 if (entry->code <= (unsigned long)end &&
123 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
129 static int __jump_label_text_reserved(struct jump_entry *iter_start,
130 struct jump_entry *iter_stop, void *start, void *end)
132 struct jump_entry *iter;
135 while (iter < iter_stop) {
136 if (addr_conflict(iter, start, end))
145 * Update code which is definitely not currently executing.
146 * Architectures which need heavyweight synchronization to modify
147 * running code can override this to make the non-live update case
150 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
151 enum jump_label_type type)
153 arch_jump_label_transform(entry, type);
156 static inline struct jump_entry *static_key_entries(struct static_key *key)
158 return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
161 static inline bool static_key_type(struct static_key *key)
163 return (unsigned long)key->entries & JUMP_TYPE_MASK;
166 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
168 return (struct static_key *)((unsigned long)entry->key & ~1UL);
171 static bool jump_entry_branch(struct jump_entry *entry)
173 return (unsigned long)entry->key & 1UL;
176 static enum jump_label_type jump_label_type(struct jump_entry *entry)
178 struct static_key *key = jump_entry_key(entry);
179 bool enabled = static_key_enabled(key);
180 bool branch = jump_entry_branch(entry);
182 /* See the comment in linux/jump_label.h */
183 return enabled ^ branch;
186 static void __jump_label_update(struct static_key *key,
187 struct jump_entry *entry,
188 struct jump_entry *stop)
190 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
192 * entry->code set to 0 invalidates module init text sections
193 * kernel_text_address() verifies we are not in core kernel
194 * init code, see jump_label_invalidate_module_init().
196 if (entry->code && kernel_text_address(entry->code))
197 arch_jump_label_transform(entry, jump_label_type(entry));
201 void __init jump_label_init(void)
203 struct jump_entry *iter_start = __start___jump_table;
204 struct jump_entry *iter_stop = __stop___jump_table;
205 struct static_key *key = NULL;
206 struct jump_entry *iter;
209 jump_label_sort_entries(iter_start, iter_stop);
211 for (iter = iter_start; iter < iter_stop; iter++) {
212 struct static_key *iterk;
215 if (jump_label_type(iter) == JUMP_LABEL_NOP)
216 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
218 iterk = jump_entry_key(iter);
224 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
226 *((unsigned long *)&key->entries) += (unsigned long)iter;
227 #ifdef CONFIG_MODULES
231 static_key_initialized = true;
235 #ifdef CONFIG_MODULES
237 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
239 struct static_key *key = jump_entry_key(entry);
240 bool type = static_key_type(key);
241 bool branch = jump_entry_branch(entry);
243 /* See the comment in linux/jump_label.h */
244 return type ^ branch;
247 struct static_key_mod {
248 struct static_key_mod *next;
249 struct jump_entry *entries;
253 static int __jump_label_mod_text_reserved(void *start, void *end)
257 mod = __module_text_address((unsigned long)start);
261 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
263 return __jump_label_text_reserved(mod->jump_entries,
264 mod->jump_entries + mod->num_jump_entries,
268 static void __jump_label_mod_update(struct static_key *key)
270 struct static_key_mod *mod;
272 for (mod = key->next; mod; mod = mod->next) {
273 struct module *m = mod->mod;
275 __jump_label_update(key, mod->entries,
276 m->jump_entries + m->num_jump_entries);
281 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
282 * @mod: module to patch
284 * Allow for run-time selection of the optimal nops. Before the module
285 * loads patch these with arch_get_jump_label_nop(), which is specified by
286 * the arch specific jump label code.
288 void jump_label_apply_nops(struct module *mod)
290 struct jump_entry *iter_start = mod->jump_entries;
291 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
292 struct jump_entry *iter;
294 /* if the module doesn't have jump label entries, just return */
295 if (iter_start == iter_stop)
298 for (iter = iter_start; iter < iter_stop; iter++) {
299 /* Only write NOPs for arch_branch_static(). */
300 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
301 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
305 static int jump_label_add_module(struct module *mod)
307 struct jump_entry *iter_start = mod->jump_entries;
308 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
309 struct jump_entry *iter;
310 struct static_key *key = NULL;
311 struct static_key_mod *jlm;
313 /* if the module doesn't have jump label entries, just return */
314 if (iter_start == iter_stop)
317 jump_label_sort_entries(iter_start, iter_stop);
319 for (iter = iter_start; iter < iter_stop; iter++) {
320 struct static_key *iterk;
322 iterk = jump_entry_key(iter);
327 if (within_module(iter->key, mod)) {
329 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
331 *((unsigned long *)&key->entries) += (unsigned long)iter;
335 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
340 jlm->next = key->next;
343 /* Only update if we've changed from our initial state */
344 if (jump_label_type(iter) != jump_label_init_type(iter))
345 __jump_label_update(key, iter, iter_stop);
351 static void jump_label_del_module(struct module *mod)
353 struct jump_entry *iter_start = mod->jump_entries;
354 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
355 struct jump_entry *iter;
356 struct static_key *key = NULL;
357 struct static_key_mod *jlm, **prev;
359 for (iter = iter_start; iter < iter_stop; iter++) {
360 if (jump_entry_key(iter) == key)
363 key = jump_entry_key(iter);
365 if (within_module(iter->key, mod))
371 while (jlm && jlm->mod != mod) {
383 static void jump_label_invalidate_module_init(struct module *mod)
385 struct jump_entry *iter_start = mod->jump_entries;
386 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
387 struct jump_entry *iter;
389 for (iter = iter_start; iter < iter_stop; iter++) {
390 if (within_module_init(iter->code, mod))
396 jump_label_module_notify(struct notifier_block *self, unsigned long val,
399 struct module *mod = data;
403 case MODULE_STATE_COMING:
405 ret = jump_label_add_module(mod);
407 jump_label_del_module(mod);
410 case MODULE_STATE_GOING:
412 jump_label_del_module(mod);
415 case MODULE_STATE_LIVE:
417 jump_label_invalidate_module_init(mod);
422 return notifier_from_errno(ret);
425 struct notifier_block jump_label_module_nb = {
426 .notifier_call = jump_label_module_notify,
427 .priority = 1, /* higher than tracepoints */
430 static __init int jump_label_init_module(void)
432 return register_module_notifier(&jump_label_module_nb);
434 early_initcall(jump_label_init_module);
436 #endif /* CONFIG_MODULES */
439 * jump_label_text_reserved - check if addr range is reserved
440 * @start: start text addr
441 * @end: end text addr
443 * checks if the text addr located between @start and @end
444 * overlaps with any of the jump label patch addresses. Code
445 * that wants to modify kernel text should first verify that
446 * it does not overlap with any of the jump label addresses.
447 * Caller must hold jump_label_mutex.
449 * returns 1 if there is an overlap, 0 otherwise
451 int jump_label_text_reserved(void *start, void *end)
453 int ret = __jump_label_text_reserved(__start___jump_table,
454 __stop___jump_table, start, end);
459 #ifdef CONFIG_MODULES
460 ret = __jump_label_mod_text_reserved(start, end);
465 static void jump_label_update(struct static_key *key)
467 struct jump_entry *stop = __stop___jump_table;
468 struct jump_entry *entry = static_key_entries(key);
469 #ifdef CONFIG_MODULES
472 __jump_label_mod_update(key);
475 mod = __module_address((unsigned long)key);
477 stop = mod->jump_entries + mod->num_jump_entries;
480 /* if there are no users, entry can be NULL */
482 __jump_label_update(key, entry, stop);
485 #ifdef CONFIG_STATIC_KEYS_SELFTEST
486 static DEFINE_STATIC_KEY_TRUE(sk_true);
487 static DEFINE_STATIC_KEY_FALSE(sk_false);
489 static __init int jump_label_test(void)
493 for (i = 0; i < 2; i++) {
494 WARN_ON(static_key_enabled(&sk_true.key) != true);
495 WARN_ON(static_key_enabled(&sk_false.key) != false);
497 WARN_ON(!static_branch_likely(&sk_true));
498 WARN_ON(!static_branch_unlikely(&sk_true));
499 WARN_ON(static_branch_likely(&sk_false));
500 WARN_ON(static_branch_unlikely(&sk_false));
502 static_branch_disable(&sk_true);
503 static_branch_enable(&sk_false);
505 WARN_ON(static_key_enabled(&sk_true.key) == true);
506 WARN_ON(static_key_enabled(&sk_false.key) == false);
508 WARN_ON(static_branch_likely(&sk_true));
509 WARN_ON(static_branch_unlikely(&sk_true));
510 WARN_ON(!static_branch_likely(&sk_false));
511 WARN_ON(!static_branch_unlikely(&sk_false));
513 static_branch_enable(&sk_true);
514 static_branch_disable(&sk_false);
519 late_initcall(jump_label_test);
520 #endif /* STATIC_KEYS_SELFTEST */
522 #endif /* HAVE_JUMP_LABEL */