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1/*
2 * jump label support
3 *
4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5 * Copyright (C) 2011 Peter Zijlstra
6 *
7 */
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>
17#include <linux/bug.h>
18
19#ifdef HAVE_JUMP_LABEL
20
21/* mutex to protect coming/going of the the jump_label table */
22static DEFINE_MUTEX(jump_label_mutex);
23
24void jump_label_lock(void)
25{
26 mutex_lock(&jump_label_mutex);
27}
28
29void jump_label_unlock(void)
30{
31 mutex_unlock(&jump_label_mutex);
32}
33
34static int jump_label_cmp(const void *a, const void *b)
35{
36 const struct jump_entry *jea = a;
37 const struct jump_entry *jeb = b;
38
39 if (jea->key < jeb->key)
40 return -1;
41
42 if (jea->key > jeb->key)
43 return 1;
44
45 return 0;
46}
47
48static void
49jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
50{
51 unsigned long size;
52
53 size = (((unsigned long)stop - (unsigned long)start)
54 / sizeof(struct jump_entry));
55 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
56}
57
58static void jump_label_update(struct static_key *key);
59
60/*
61 * There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h.
62 * The use of 'atomic_read()' requires atomic.h and its problematic for some
63 * kernel headers such as kernel.h and others. Since static_key_count() is not
64 * used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok
65 * to have it be a function here. Similarly, for 'static_key_enable()' and
66 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
67 * to be included from most/all places for HAVE_JUMP_LABEL.
68 */
69int static_key_count(struct static_key *key)
70{
71 /*
72 * -1 means the first static_key_slow_inc() is in progress.
73 * static_key_enabled() must return true, so return 1 here.
74 */
75 int n = atomic_read(&key->enabled);
76
77 return n >= 0 ? n : 1;
78}
79EXPORT_SYMBOL_GPL(static_key_count);
80
81void static_key_enable(struct static_key *key)
82{
83 int count = static_key_count(key);
84
85 WARN_ON_ONCE(count < 0 || count > 1);
86
87 if (!count)
88 static_key_slow_inc(key);
89}
90EXPORT_SYMBOL_GPL(static_key_enable);
91
92void static_key_disable(struct static_key *key)
93{
94 int count = static_key_count(key);
95
96 WARN_ON_ONCE(count < 0 || count > 1);
97
98 if (count)
99 static_key_slow_dec(key);
100}
101EXPORT_SYMBOL_GPL(static_key_disable);
102
103void static_key_slow_inc(struct static_key *key)
104{
105 int v, v1;
106
107 STATIC_KEY_CHECK_USE();
108
109 /*
110 * Careful if we get concurrent static_key_slow_inc() calls;
111 * later calls must wait for the first one to _finish_ the
112 * jump_label_update() process. At the same time, however,
113 * the jump_label_update() call below wants to see
114 * static_key_enabled(&key) for jumps to be updated properly.
115 *
116 * So give a special meaning to negative key->enabled: it sends
117 * static_key_slow_inc() down the slow path, and it is non-zero
118 * so it counts as "enabled" in jump_label_update(). Note that
119 * atomic_inc_unless_negative() checks >= 0, so roll our own.
120 */
121 for (v = atomic_read(&key->enabled); v > 0; v = v1) {
122 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
123 if (likely(v1 == v))
124 return;
125 }
126
127 jump_label_lock();
128 if (atomic_read(&key->enabled) == 0) {
129 atomic_set(&key->enabled, -1);
130 jump_label_update(key);
131 atomic_set(&key->enabled, 1);
132 } else {
133 atomic_inc(&key->enabled);
134 }
135 jump_label_unlock();
136}
137EXPORT_SYMBOL_GPL(static_key_slow_inc);
138
139static void __static_key_slow_dec(struct static_key *key,
140 unsigned long rate_limit, struct delayed_work *work)
141{
142 /*
143 * The negative count check is valid even when a negative
144 * key->enabled is in use by static_key_slow_inc(); a
145 * __static_key_slow_dec() before the first static_key_slow_inc()
146 * returns is unbalanced, because all other static_key_slow_inc()
147 * instances block while the update is in progress.
148 */
149 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
150 WARN(atomic_read(&key->enabled) < 0,
151 "jump label: negative count!\n");
152 return;
153 }
154
155 if (rate_limit) {
156 atomic_inc(&key->enabled);
157 schedule_delayed_work(work, rate_limit);
158 } else {
159 jump_label_update(key);
160 }
161 jump_label_unlock();
162}
163
164static void jump_label_update_timeout(struct work_struct *work)
165{
166 struct static_key_deferred *key =
167 container_of(work, struct static_key_deferred, work.work);
168 __static_key_slow_dec(&key->key, 0, NULL);
169}
170
171void static_key_slow_dec(struct static_key *key)
172{
173 STATIC_KEY_CHECK_USE();
174 __static_key_slow_dec(key, 0, NULL);
175}
176EXPORT_SYMBOL_GPL(static_key_slow_dec);
177
178void static_key_slow_dec_deferred(struct static_key_deferred *key)
179{
180 STATIC_KEY_CHECK_USE();
181 __static_key_slow_dec(&key->key, key->timeout, &key->work);
182}
183EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
184
185void static_key_deferred_flush(struct static_key_deferred *key)
186{
187 STATIC_KEY_CHECK_USE();
188 flush_delayed_work(&key->work);
189}
190EXPORT_SYMBOL_GPL(static_key_deferred_flush);
191
192void jump_label_rate_limit(struct static_key_deferred *key,
193 unsigned long rl)
194{
195 STATIC_KEY_CHECK_USE();
196 key->timeout = rl;
197 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
198}
199EXPORT_SYMBOL_GPL(jump_label_rate_limit);
200
201static int addr_conflict(struct jump_entry *entry, void *start, void *end)
202{
203 if (entry->code <= (unsigned long)end &&
204 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
205 return 1;
206
207 return 0;
208}
209
210static int __jump_label_text_reserved(struct jump_entry *iter_start,
211 struct jump_entry *iter_stop, void *start, void *end)
212{
213 struct jump_entry *iter;
214
215 iter = iter_start;
216 while (iter < iter_stop) {
217 if (addr_conflict(iter, start, end))
218 return 1;
219 iter++;
220 }
221
222 return 0;
223}
224
225/*
226 * Update code which is definitely not currently executing.
227 * Architectures which need heavyweight synchronization to modify
228 * running code can override this to make the non-live update case
229 * cheaper.
230 */
231void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
232 enum jump_label_type type)
233{
234 arch_jump_label_transform(entry, type);
235}
236
237static inline struct jump_entry *static_key_entries(struct static_key *key)
238{
239 return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
240}
241
242static inline bool static_key_type(struct static_key *key)
243{
244 return (unsigned long)key->entries & JUMP_TYPE_MASK;
245}
246
247static inline struct static_key *jump_entry_key(struct jump_entry *entry)
248{
249 return (struct static_key *)((unsigned long)entry->key & ~1UL);
250}
251
252static bool jump_entry_branch(struct jump_entry *entry)
253{
254 return (unsigned long)entry->key & 1UL;
255}
256
257static enum jump_label_type jump_label_type(struct jump_entry *entry)
258{
259 struct static_key *key = jump_entry_key(entry);
260 bool enabled = static_key_enabled(key);
261 bool branch = jump_entry_branch(entry);
262
263 /* See the comment in linux/jump_label.h */
264 return enabled ^ branch;
265}
266
267static void __jump_label_update(struct static_key *key,
268 struct jump_entry *entry,
269 struct jump_entry *stop)
270{
271 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
272 /*
273 * entry->code set to 0 invalidates module init text sections
274 * kernel_text_address() verifies we are not in core kernel
275 * init code, see jump_label_invalidate_module_init().
276 */
277 if (entry->code && kernel_text_address(entry->code))
278 arch_jump_label_transform(entry, jump_label_type(entry));
279 }
280}
281
282void __init jump_label_init(void)
283{
284 struct jump_entry *iter_start = __start___jump_table;
285 struct jump_entry *iter_stop = __stop___jump_table;
286 struct static_key *key = NULL;
287 struct jump_entry *iter;
288
289 /*
290 * Since we are initializing the static_key.enabled field with
291 * with the 'raw' int values (to avoid pulling in atomic.h) in
292 * jump_label.h, let's make sure that is safe. There are only two
293 * cases to check since we initialize to 0 or 1.
294 */
295 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
296 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
297
298 if (static_key_initialized)
299 return;
300
301 jump_label_lock();
302 jump_label_sort_entries(iter_start, iter_stop);
303
304 for (iter = iter_start; iter < iter_stop; iter++) {
305 struct static_key *iterk;
306
307 /* rewrite NOPs */
308 if (jump_label_type(iter) == JUMP_LABEL_NOP)
309 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
310
311 iterk = jump_entry_key(iter);
312 if (iterk == key)
313 continue;
314
315 key = iterk;
316 /*
317 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
318 */
319 *((unsigned long *)&key->entries) += (unsigned long)iter;
320#ifdef CONFIG_MODULES
321 key->next = NULL;
322#endif
323 }
324 static_key_initialized = true;
325 jump_label_unlock();
326}
327
328#ifdef CONFIG_MODULES
329
330static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
331{
332 struct static_key *key = jump_entry_key(entry);
333 bool type = static_key_type(key);
334 bool branch = jump_entry_branch(entry);
335
336 /* See the comment in linux/jump_label.h */
337 return type ^ branch;
338}
339
340struct static_key_mod {
341 struct static_key_mod *next;
342 struct jump_entry *entries;
343 struct module *mod;
344};
345
346static int __jump_label_mod_text_reserved(void *start, void *end)
347{
348 struct module *mod;
349
350 preempt_disable();
351 mod = __module_text_address((unsigned long)start);
352 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
353 preempt_enable();
354
355 if (!mod)
356 return 0;
357
358
359 return __jump_label_text_reserved(mod->jump_entries,
360 mod->jump_entries + mod->num_jump_entries,
361 start, end);
362}
363
364static void __jump_label_mod_update(struct static_key *key)
365{
366 struct static_key_mod *mod;
367
368 for (mod = key->next; mod; mod = mod->next) {
369 struct module *m = mod->mod;
370
371 __jump_label_update(key, mod->entries,
372 m->jump_entries + m->num_jump_entries);
373 }
374}
375
376/***
377 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
378 * @mod: module to patch
379 *
380 * Allow for run-time selection of the optimal nops. Before the module
381 * loads patch these with arch_get_jump_label_nop(), which is specified by
382 * the arch specific jump label code.
383 */
384void jump_label_apply_nops(struct module *mod)
385{
386 struct jump_entry *iter_start = mod->jump_entries;
387 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
388 struct jump_entry *iter;
389
390 /* if the module doesn't have jump label entries, just return */
391 if (iter_start == iter_stop)
392 return;
393
394 for (iter = iter_start; iter < iter_stop; iter++) {
395 /* Only write NOPs for arch_branch_static(). */
396 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
397 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
398 }
399}
400
401static int jump_label_add_module(struct module *mod)
402{
403 struct jump_entry *iter_start = mod->jump_entries;
404 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
405 struct jump_entry *iter;
406 struct static_key *key = NULL;
407 struct static_key_mod *jlm;
408
409 /* if the module doesn't have jump label entries, just return */
410 if (iter_start == iter_stop)
411 return 0;
412
413 jump_label_sort_entries(iter_start, iter_stop);
414
415 for (iter = iter_start; iter < iter_stop; iter++) {
416 struct static_key *iterk;
417
418 iterk = jump_entry_key(iter);
419 if (iterk == key)
420 continue;
421
422 key = iterk;
423 if (within_module(iter->key, mod)) {
424 /*
425 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
426 */
427 *((unsigned long *)&key->entries) += (unsigned long)iter;
428 key->next = NULL;
429 continue;
430 }
431 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
432 if (!jlm)
433 return -ENOMEM;
434 jlm->mod = mod;
435 jlm->entries = iter;
436 jlm->next = key->next;
437 key->next = jlm;
438
439 /* Only update if we've changed from our initial state */
440 if (jump_label_type(iter) != jump_label_init_type(iter))
441 __jump_label_update(key, iter, iter_stop);
442 }
443
444 return 0;
445}
446
447static void jump_label_del_module(struct module *mod)
448{
449 struct jump_entry *iter_start = mod->jump_entries;
450 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
451 struct jump_entry *iter;
452 struct static_key *key = NULL;
453 struct static_key_mod *jlm, **prev;
454
455 for (iter = iter_start; iter < iter_stop; iter++) {
456 if (jump_entry_key(iter) == key)
457 continue;
458
459 key = jump_entry_key(iter);
460
461 if (within_module(iter->key, mod))
462 continue;
463
464 prev = &key->next;
465 jlm = key->next;
466
467 while (jlm && jlm->mod != mod) {
468 prev = &jlm->next;
469 jlm = jlm->next;
470 }
471
472 if (jlm) {
473 *prev = jlm->next;
474 kfree(jlm);
475 }
476 }
477}
478
479static void jump_label_invalidate_module_init(struct module *mod)
480{
481 struct jump_entry *iter_start = mod->jump_entries;
482 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
483 struct jump_entry *iter;
484
485 for (iter = iter_start; iter < iter_stop; iter++) {
486 if (within_module_init(iter->code, mod))
487 iter->code = 0;
488 }
489}
490
491static int
492jump_label_module_notify(struct notifier_block *self, unsigned long val,
493 void *data)
494{
495 struct module *mod = data;
496 int ret = 0;
497
498 switch (val) {
499 case MODULE_STATE_COMING:
500 jump_label_lock();
501 ret = jump_label_add_module(mod);
502 if (ret)
503 jump_label_del_module(mod);
504 jump_label_unlock();
505 break;
506 case MODULE_STATE_GOING:
507 jump_label_lock();
508 jump_label_del_module(mod);
509 jump_label_unlock();
510 break;
511 case MODULE_STATE_LIVE:
512 jump_label_lock();
513 jump_label_invalidate_module_init(mod);
514 jump_label_unlock();
515 break;
516 }
517
518 return notifier_from_errno(ret);
519}
520
521static struct notifier_block jump_label_module_nb = {
522 .notifier_call = jump_label_module_notify,
523 .priority = 1, /* higher than tracepoints */
524};
525
526static __init int jump_label_init_module(void)
527{
528 return register_module_notifier(&jump_label_module_nb);
529}
530early_initcall(jump_label_init_module);
531
532#endif /* CONFIG_MODULES */
533
534/***
535 * jump_label_text_reserved - check if addr range is reserved
536 * @start: start text addr
537 * @end: end text addr
538 *
539 * checks if the text addr located between @start and @end
540 * overlaps with any of the jump label patch addresses. Code
541 * that wants to modify kernel text should first verify that
542 * it does not overlap with any of the jump label addresses.
543 * Caller must hold jump_label_mutex.
544 *
545 * returns 1 if there is an overlap, 0 otherwise
546 */
547int jump_label_text_reserved(void *start, void *end)
548{
549 int ret = __jump_label_text_reserved(__start___jump_table,
550 __stop___jump_table, start, end);
551
552 if (ret)
553 return ret;
554
555#ifdef CONFIG_MODULES
556 ret = __jump_label_mod_text_reserved(start, end);
557#endif
558 return ret;
559}
560
561static void jump_label_update(struct static_key *key)
562{
563 struct jump_entry *stop = __stop___jump_table;
564 struct jump_entry *entry = static_key_entries(key);
565#ifdef CONFIG_MODULES
566 struct module *mod;
567
568 __jump_label_mod_update(key);
569
570 preempt_disable();
571 mod = __module_address((unsigned long)key);
572 if (mod)
573 stop = mod->jump_entries + mod->num_jump_entries;
574 preempt_enable();
575#endif
576 /* if there are no users, entry can be NULL */
577 if (entry)
578 __jump_label_update(key, entry, stop);
579}
580
581#ifdef CONFIG_STATIC_KEYS_SELFTEST
582static DEFINE_STATIC_KEY_TRUE(sk_true);
583static DEFINE_STATIC_KEY_FALSE(sk_false);
584
585static __init int jump_label_test(void)
586{
587 int i;
588
589 for (i = 0; i < 2; i++) {
590 WARN_ON(static_key_enabled(&sk_true.key) != true);
591 WARN_ON(static_key_enabled(&sk_false.key) != false);
592
593 WARN_ON(!static_branch_likely(&sk_true));
594 WARN_ON(!static_branch_unlikely(&sk_true));
595 WARN_ON(static_branch_likely(&sk_false));
596 WARN_ON(static_branch_unlikely(&sk_false));
597
598 static_branch_disable(&sk_true);
599 static_branch_enable(&sk_false);
600
601 WARN_ON(static_key_enabled(&sk_true.key) == true);
602 WARN_ON(static_key_enabled(&sk_false.key) == false);
603
604 WARN_ON(static_branch_likely(&sk_true));
605 WARN_ON(static_branch_unlikely(&sk_true));
606 WARN_ON(!static_branch_likely(&sk_false));
607 WARN_ON(!static_branch_unlikely(&sk_false));
608
609 static_branch_enable(&sk_true);
610 static_branch_disable(&sk_false);
611 }
612
613 return 0;
614}
615late_initcall(jump_label_test);
616#endif /* STATIC_KEYS_SELFTEST */
617
618#endif /* HAVE_JUMP_LABEL */
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * jump label support
4 *
5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
6 * Copyright (C) 2011 Peter Zijlstra
7 *
8 */
9#include <linux/memory.h>
10#include <linux/uaccess.h>
11#include <linux/module.h>
12#include <linux/list.h>
13#include <linux/slab.h>
14#include <linux/sort.h>
15#include <linux/err.h>
16#include <linux/static_key.h>
17#include <linux/jump_label_ratelimit.h>
18#include <linux/bug.h>
19#include <linux/cpu.h>
20#include <asm/sections.h>
21
22/* mutex to protect coming/going of the jump_label table */
23static DEFINE_MUTEX(jump_label_mutex);
24
25void jump_label_lock(void)
26{
27 mutex_lock(&jump_label_mutex);
28}
29
30void jump_label_unlock(void)
31{
32 mutex_unlock(&jump_label_mutex);
33}
34
35static int jump_label_cmp(const void *a, const void *b)
36{
37 const struct jump_entry *jea = a;
38 const struct jump_entry *jeb = b;
39
40 /*
41 * Entrires are sorted by key.
42 */
43 if (jump_entry_key(jea) < jump_entry_key(jeb))
44 return -1;
45
46 if (jump_entry_key(jea) > jump_entry_key(jeb))
47 return 1;
48
49 /*
50 * In the batching mode, entries should also be sorted by the code
51 * inside the already sorted list of entries, enabling a bsearch in
52 * the vector.
53 */
54 if (jump_entry_code(jea) < jump_entry_code(jeb))
55 return -1;
56
57 if (jump_entry_code(jea) > jump_entry_code(jeb))
58 return 1;
59
60 return 0;
61}
62
63static void jump_label_swap(void *a, void *b, int size)
64{
65 long delta = (unsigned long)a - (unsigned long)b;
66 struct jump_entry *jea = a;
67 struct jump_entry *jeb = b;
68 struct jump_entry tmp = *jea;
69
70 jea->code = jeb->code - delta;
71 jea->target = jeb->target - delta;
72 jea->key = jeb->key - delta;
73
74 jeb->code = tmp.code + delta;
75 jeb->target = tmp.target + delta;
76 jeb->key = tmp.key + delta;
77}
78
79static void
80jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
81{
82 unsigned long size;
83 void *swapfn = NULL;
84
85 if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
86 swapfn = jump_label_swap;
87
88 size = (((unsigned long)stop - (unsigned long)start)
89 / sizeof(struct jump_entry));
90 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
91}
92
93static void jump_label_update(struct static_key *key);
94
95/*
96 * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
97 * The use of 'atomic_read()' requires atomic.h and its problematic for some
98 * kernel headers such as kernel.h and others. Since static_key_count() is not
99 * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
100 * to have it be a function here. Similarly, for 'static_key_enable()' and
101 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
102 * to be included from most/all places for CONFIG_JUMP_LABEL.
103 */
104int static_key_count(struct static_key *key)
105{
106 /*
107 * -1 means the first static_key_slow_inc() is in progress.
108 * static_key_enabled() must return true, so return 1 here.
109 */
110 int n = atomic_read(&key->enabled);
111
112 return n >= 0 ? n : 1;
113}
114EXPORT_SYMBOL_GPL(static_key_count);
115
116/*
117 * static_key_fast_inc_not_disabled - adds a user for a static key
118 * @key: static key that must be already enabled
119 *
120 * The caller must make sure that the static key can't get disabled while
121 * in this function. It doesn't patch jump labels, only adds a user to
122 * an already enabled static key.
123 *
124 * Returns true if the increment was done. Unlike refcount_t the ref counter
125 * is not saturated, but will fail to increment on overflow.
126 */
127bool static_key_fast_inc_not_disabled(struct static_key *key)
128{
129 int v;
130
131 STATIC_KEY_CHECK_USE(key);
132 /*
133 * Negative key->enabled has a special meaning: it sends
134 * static_key_slow_inc() down the slow path, and it is non-zero
135 * so it counts as "enabled" in jump_label_update(). Note that
136 * atomic_inc_unless_negative() checks >= 0, so roll our own.
137 */
138 v = atomic_read(&key->enabled);
139 do {
140 if (v <= 0 || (v + 1) < 0)
141 return false;
142 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
143
144 return true;
145}
146EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
147
148bool static_key_slow_inc_cpuslocked(struct static_key *key)
149{
150 lockdep_assert_cpus_held();
151
152 /*
153 * Careful if we get concurrent static_key_slow_inc() calls;
154 * later calls must wait for the first one to _finish_ the
155 * jump_label_update() process. At the same time, however,
156 * the jump_label_update() call below wants to see
157 * static_key_enabled(&key) for jumps to be updated properly.
158 */
159 if (static_key_fast_inc_not_disabled(key))
160 return true;
161
162 jump_label_lock();
163 if (atomic_read(&key->enabled) == 0) {
164 atomic_set(&key->enabled, -1);
165 jump_label_update(key);
166 /*
167 * Ensure that if the above cmpxchg loop observes our positive
168 * value, it must also observe all the text changes.
169 */
170 atomic_set_release(&key->enabled, 1);
171 } else {
172 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key))) {
173 jump_label_unlock();
174 return false;
175 }
176 }
177 jump_label_unlock();
178 return true;
179}
180
181bool static_key_slow_inc(struct static_key *key)
182{
183 bool ret;
184
185 cpus_read_lock();
186 ret = static_key_slow_inc_cpuslocked(key);
187 cpus_read_unlock();
188 return ret;
189}
190EXPORT_SYMBOL_GPL(static_key_slow_inc);
191
192void static_key_enable_cpuslocked(struct static_key *key)
193{
194 STATIC_KEY_CHECK_USE(key);
195 lockdep_assert_cpus_held();
196
197 if (atomic_read(&key->enabled) > 0) {
198 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
199 return;
200 }
201
202 jump_label_lock();
203 if (atomic_read(&key->enabled) == 0) {
204 atomic_set(&key->enabled, -1);
205 jump_label_update(key);
206 /*
207 * See static_key_slow_inc().
208 */
209 atomic_set_release(&key->enabled, 1);
210 }
211 jump_label_unlock();
212}
213EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
214
215void static_key_enable(struct static_key *key)
216{
217 cpus_read_lock();
218 static_key_enable_cpuslocked(key);
219 cpus_read_unlock();
220}
221EXPORT_SYMBOL_GPL(static_key_enable);
222
223void static_key_disable_cpuslocked(struct static_key *key)
224{
225 STATIC_KEY_CHECK_USE(key);
226 lockdep_assert_cpus_held();
227
228 if (atomic_read(&key->enabled) != 1) {
229 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
230 return;
231 }
232
233 jump_label_lock();
234 if (atomic_cmpxchg(&key->enabled, 1, 0))
235 jump_label_update(key);
236 jump_label_unlock();
237}
238EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
239
240void static_key_disable(struct static_key *key)
241{
242 cpus_read_lock();
243 static_key_disable_cpuslocked(key);
244 cpus_read_unlock();
245}
246EXPORT_SYMBOL_GPL(static_key_disable);
247
248static bool static_key_slow_try_dec(struct static_key *key)
249{
250 int val;
251
252 val = atomic_fetch_add_unless(&key->enabled, -1, 1);
253 if (val == 1)
254 return false;
255
256 /*
257 * The negative count check is valid even when a negative
258 * key->enabled is in use by static_key_slow_inc(); a
259 * __static_key_slow_dec() before the first static_key_slow_inc()
260 * returns is unbalanced, because all other static_key_slow_inc()
261 * instances block while the update is in progress.
262 */
263 WARN(val < 0, "jump label: negative count!\n");
264 return true;
265}
266
267static void __static_key_slow_dec_cpuslocked(struct static_key *key)
268{
269 lockdep_assert_cpus_held();
270
271 if (static_key_slow_try_dec(key))
272 return;
273
274 jump_label_lock();
275 if (atomic_dec_and_test(&key->enabled))
276 jump_label_update(key);
277 jump_label_unlock();
278}
279
280static void __static_key_slow_dec(struct static_key *key)
281{
282 cpus_read_lock();
283 __static_key_slow_dec_cpuslocked(key);
284 cpus_read_unlock();
285}
286
287void jump_label_update_timeout(struct work_struct *work)
288{
289 struct static_key_deferred *key =
290 container_of(work, struct static_key_deferred, work.work);
291 __static_key_slow_dec(&key->key);
292}
293EXPORT_SYMBOL_GPL(jump_label_update_timeout);
294
295void static_key_slow_dec(struct static_key *key)
296{
297 STATIC_KEY_CHECK_USE(key);
298 __static_key_slow_dec(key);
299}
300EXPORT_SYMBOL_GPL(static_key_slow_dec);
301
302void static_key_slow_dec_cpuslocked(struct static_key *key)
303{
304 STATIC_KEY_CHECK_USE(key);
305 __static_key_slow_dec_cpuslocked(key);
306}
307
308void __static_key_slow_dec_deferred(struct static_key *key,
309 struct delayed_work *work,
310 unsigned long timeout)
311{
312 STATIC_KEY_CHECK_USE(key);
313
314 if (static_key_slow_try_dec(key))
315 return;
316
317 schedule_delayed_work(work, timeout);
318}
319EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
320
321void __static_key_deferred_flush(void *key, struct delayed_work *work)
322{
323 STATIC_KEY_CHECK_USE(key);
324 flush_delayed_work(work);
325}
326EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
327
328void jump_label_rate_limit(struct static_key_deferred *key,
329 unsigned long rl)
330{
331 STATIC_KEY_CHECK_USE(key);
332 key->timeout = rl;
333 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
334}
335EXPORT_SYMBOL_GPL(jump_label_rate_limit);
336
337static int addr_conflict(struct jump_entry *entry, void *start, void *end)
338{
339 if (jump_entry_code(entry) <= (unsigned long)end &&
340 jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
341 return 1;
342
343 return 0;
344}
345
346static int __jump_label_text_reserved(struct jump_entry *iter_start,
347 struct jump_entry *iter_stop, void *start, void *end, bool init)
348{
349 struct jump_entry *iter;
350
351 iter = iter_start;
352 while (iter < iter_stop) {
353 if (init || !jump_entry_is_init(iter)) {
354 if (addr_conflict(iter, start, end))
355 return 1;
356 }
357 iter++;
358 }
359
360 return 0;
361}
362
363#ifndef arch_jump_label_transform_static
364static void arch_jump_label_transform_static(struct jump_entry *entry,
365 enum jump_label_type type)
366{
367 /* nothing to do on most architectures */
368}
369#endif
370
371static inline struct jump_entry *static_key_entries(struct static_key *key)
372{
373 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
374 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
375}
376
377static inline bool static_key_type(struct static_key *key)
378{
379 return key->type & JUMP_TYPE_TRUE;
380}
381
382static inline bool static_key_linked(struct static_key *key)
383{
384 return key->type & JUMP_TYPE_LINKED;
385}
386
387static inline void static_key_clear_linked(struct static_key *key)
388{
389 key->type &= ~JUMP_TYPE_LINKED;
390}
391
392static inline void static_key_set_linked(struct static_key *key)
393{
394 key->type |= JUMP_TYPE_LINKED;
395}
396
397/***
398 * A 'struct static_key' uses a union such that it either points directly
399 * to a table of 'struct jump_entry' or to a linked list of modules which in
400 * turn point to 'struct jump_entry' tables.
401 *
402 * The two lower bits of the pointer are used to keep track of which pointer
403 * type is in use and to store the initial branch direction, we use an access
404 * function which preserves these bits.
405 */
406static void static_key_set_entries(struct static_key *key,
407 struct jump_entry *entries)
408{
409 unsigned long type;
410
411 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
412 type = key->type & JUMP_TYPE_MASK;
413 key->entries = entries;
414 key->type |= type;
415}
416
417static enum jump_label_type jump_label_type(struct jump_entry *entry)
418{
419 struct static_key *key = jump_entry_key(entry);
420 bool enabled = static_key_enabled(key);
421 bool branch = jump_entry_is_branch(entry);
422
423 /* See the comment in linux/jump_label.h */
424 return enabled ^ branch;
425}
426
427static bool jump_label_can_update(struct jump_entry *entry, bool init)
428{
429 /*
430 * Cannot update code that was in an init text area.
431 */
432 if (!init && jump_entry_is_init(entry))
433 return false;
434
435 if (!kernel_text_address(jump_entry_code(entry))) {
436 /*
437 * This skips patching built-in __exit, which
438 * is part of init_section_contains() but is
439 * not part of kernel_text_address().
440 *
441 * Skipping built-in __exit is fine since it
442 * will never be executed.
443 */
444 WARN_ONCE(!jump_entry_is_init(entry),
445 "can't patch jump_label at %pS",
446 (void *)jump_entry_code(entry));
447 return false;
448 }
449
450 return true;
451}
452
453#ifndef HAVE_JUMP_LABEL_BATCH
454static void __jump_label_update(struct static_key *key,
455 struct jump_entry *entry,
456 struct jump_entry *stop,
457 bool init)
458{
459 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
460 if (jump_label_can_update(entry, init))
461 arch_jump_label_transform(entry, jump_label_type(entry));
462 }
463}
464#else
465static void __jump_label_update(struct static_key *key,
466 struct jump_entry *entry,
467 struct jump_entry *stop,
468 bool init)
469{
470 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
471
472 if (!jump_label_can_update(entry, init))
473 continue;
474
475 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
476 /*
477 * Queue is full: Apply the current queue and try again.
478 */
479 arch_jump_label_transform_apply();
480 BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
481 }
482 }
483 arch_jump_label_transform_apply();
484}
485#endif
486
487void __init jump_label_init(void)
488{
489 struct jump_entry *iter_start = __start___jump_table;
490 struct jump_entry *iter_stop = __stop___jump_table;
491 struct static_key *key = NULL;
492 struct jump_entry *iter;
493
494 /*
495 * Since we are initializing the static_key.enabled field with
496 * with the 'raw' int values (to avoid pulling in atomic.h) in
497 * jump_label.h, let's make sure that is safe. There are only two
498 * cases to check since we initialize to 0 or 1.
499 */
500 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
501 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
502
503 if (static_key_initialized)
504 return;
505
506 cpus_read_lock();
507 jump_label_lock();
508 jump_label_sort_entries(iter_start, iter_stop);
509
510 for (iter = iter_start; iter < iter_stop; iter++) {
511 struct static_key *iterk;
512 bool in_init;
513
514 /* rewrite NOPs */
515 if (jump_label_type(iter) == JUMP_LABEL_NOP)
516 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
517
518 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
519 jump_entry_set_init(iter, in_init);
520
521 iterk = jump_entry_key(iter);
522 if (iterk == key)
523 continue;
524
525 key = iterk;
526 static_key_set_entries(key, iter);
527 }
528 static_key_initialized = true;
529 jump_label_unlock();
530 cpus_read_unlock();
531}
532
533#ifdef CONFIG_MODULES
534
535enum jump_label_type jump_label_init_type(struct jump_entry *entry)
536{
537 struct static_key *key = jump_entry_key(entry);
538 bool type = static_key_type(key);
539 bool branch = jump_entry_is_branch(entry);
540
541 /* See the comment in linux/jump_label.h */
542 return type ^ branch;
543}
544
545struct static_key_mod {
546 struct static_key_mod *next;
547 struct jump_entry *entries;
548 struct module *mod;
549};
550
551static inline struct static_key_mod *static_key_mod(struct static_key *key)
552{
553 WARN_ON_ONCE(!static_key_linked(key));
554 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
555}
556
557/***
558 * key->type and key->next are the same via union.
559 * This sets key->next and preserves the type bits.
560 *
561 * See additional comments above static_key_set_entries().
562 */
563static void static_key_set_mod(struct static_key *key,
564 struct static_key_mod *mod)
565{
566 unsigned long type;
567
568 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
569 type = key->type & JUMP_TYPE_MASK;
570 key->next = mod;
571 key->type |= type;
572}
573
574static int __jump_label_mod_text_reserved(void *start, void *end)
575{
576 struct module *mod;
577 int ret;
578
579 preempt_disable();
580 mod = __module_text_address((unsigned long)start);
581 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
582 if (!try_module_get(mod))
583 mod = NULL;
584 preempt_enable();
585
586 if (!mod)
587 return 0;
588
589 ret = __jump_label_text_reserved(mod->jump_entries,
590 mod->jump_entries + mod->num_jump_entries,
591 start, end, mod->state == MODULE_STATE_COMING);
592
593 module_put(mod);
594
595 return ret;
596}
597
598static void __jump_label_mod_update(struct static_key *key)
599{
600 struct static_key_mod *mod;
601
602 for (mod = static_key_mod(key); mod; mod = mod->next) {
603 struct jump_entry *stop;
604 struct module *m;
605
606 /*
607 * NULL if the static_key is defined in a module
608 * that does not use it
609 */
610 if (!mod->entries)
611 continue;
612
613 m = mod->mod;
614 if (!m)
615 stop = __stop___jump_table;
616 else
617 stop = m->jump_entries + m->num_jump_entries;
618 __jump_label_update(key, mod->entries, stop,
619 m && m->state == MODULE_STATE_COMING);
620 }
621}
622
623static int jump_label_add_module(struct module *mod)
624{
625 struct jump_entry *iter_start = mod->jump_entries;
626 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
627 struct jump_entry *iter;
628 struct static_key *key = NULL;
629 struct static_key_mod *jlm, *jlm2;
630
631 /* if the module doesn't have jump label entries, just return */
632 if (iter_start == iter_stop)
633 return 0;
634
635 jump_label_sort_entries(iter_start, iter_stop);
636
637 for (iter = iter_start; iter < iter_stop; iter++) {
638 struct static_key *iterk;
639 bool in_init;
640
641 in_init = within_module_init(jump_entry_code(iter), mod);
642 jump_entry_set_init(iter, in_init);
643
644 iterk = jump_entry_key(iter);
645 if (iterk == key)
646 continue;
647
648 key = iterk;
649 if (within_module((unsigned long)key, mod)) {
650 static_key_set_entries(key, iter);
651 continue;
652 }
653 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
654 if (!jlm)
655 return -ENOMEM;
656 if (!static_key_linked(key)) {
657 jlm2 = kzalloc(sizeof(struct static_key_mod),
658 GFP_KERNEL);
659 if (!jlm2) {
660 kfree(jlm);
661 return -ENOMEM;
662 }
663 preempt_disable();
664 jlm2->mod = __module_address((unsigned long)key);
665 preempt_enable();
666 jlm2->entries = static_key_entries(key);
667 jlm2->next = NULL;
668 static_key_set_mod(key, jlm2);
669 static_key_set_linked(key);
670 }
671 jlm->mod = mod;
672 jlm->entries = iter;
673 jlm->next = static_key_mod(key);
674 static_key_set_mod(key, jlm);
675 static_key_set_linked(key);
676
677 /* Only update if we've changed from our initial state */
678 if (jump_label_type(iter) != jump_label_init_type(iter))
679 __jump_label_update(key, iter, iter_stop, true);
680 }
681
682 return 0;
683}
684
685static void jump_label_del_module(struct module *mod)
686{
687 struct jump_entry *iter_start = mod->jump_entries;
688 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
689 struct jump_entry *iter;
690 struct static_key *key = NULL;
691 struct static_key_mod *jlm, **prev;
692
693 for (iter = iter_start; iter < iter_stop; iter++) {
694 if (jump_entry_key(iter) == key)
695 continue;
696
697 key = jump_entry_key(iter);
698
699 if (within_module((unsigned long)key, mod))
700 continue;
701
702 /* No memory during module load */
703 if (WARN_ON(!static_key_linked(key)))
704 continue;
705
706 prev = &key->next;
707 jlm = static_key_mod(key);
708
709 while (jlm && jlm->mod != mod) {
710 prev = &jlm->next;
711 jlm = jlm->next;
712 }
713
714 /* No memory during module load */
715 if (WARN_ON(!jlm))
716 continue;
717
718 if (prev == &key->next)
719 static_key_set_mod(key, jlm->next);
720 else
721 *prev = jlm->next;
722
723 kfree(jlm);
724
725 jlm = static_key_mod(key);
726 /* if only one etry is left, fold it back into the static_key */
727 if (jlm->next == NULL) {
728 static_key_set_entries(key, jlm->entries);
729 static_key_clear_linked(key);
730 kfree(jlm);
731 }
732 }
733}
734
735static int
736jump_label_module_notify(struct notifier_block *self, unsigned long val,
737 void *data)
738{
739 struct module *mod = data;
740 int ret = 0;
741
742 cpus_read_lock();
743 jump_label_lock();
744
745 switch (val) {
746 case MODULE_STATE_COMING:
747 ret = jump_label_add_module(mod);
748 if (ret) {
749 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
750 jump_label_del_module(mod);
751 }
752 break;
753 case MODULE_STATE_GOING:
754 jump_label_del_module(mod);
755 break;
756 }
757
758 jump_label_unlock();
759 cpus_read_unlock();
760
761 return notifier_from_errno(ret);
762}
763
764static struct notifier_block jump_label_module_nb = {
765 .notifier_call = jump_label_module_notify,
766 .priority = 1, /* higher than tracepoints */
767};
768
769static __init int jump_label_init_module(void)
770{
771 return register_module_notifier(&jump_label_module_nb);
772}
773early_initcall(jump_label_init_module);
774
775#endif /* CONFIG_MODULES */
776
777/***
778 * jump_label_text_reserved - check if addr range is reserved
779 * @start: start text addr
780 * @end: end text addr
781 *
782 * checks if the text addr located between @start and @end
783 * overlaps with any of the jump label patch addresses. Code
784 * that wants to modify kernel text should first verify that
785 * it does not overlap with any of the jump label addresses.
786 * Caller must hold jump_label_mutex.
787 *
788 * returns 1 if there is an overlap, 0 otherwise
789 */
790int jump_label_text_reserved(void *start, void *end)
791{
792 bool init = system_state < SYSTEM_RUNNING;
793 int ret = __jump_label_text_reserved(__start___jump_table,
794 __stop___jump_table, start, end, init);
795
796 if (ret)
797 return ret;
798
799#ifdef CONFIG_MODULES
800 ret = __jump_label_mod_text_reserved(start, end);
801#endif
802 return ret;
803}
804
805static void jump_label_update(struct static_key *key)
806{
807 struct jump_entry *stop = __stop___jump_table;
808 bool init = system_state < SYSTEM_RUNNING;
809 struct jump_entry *entry;
810#ifdef CONFIG_MODULES
811 struct module *mod;
812
813 if (static_key_linked(key)) {
814 __jump_label_mod_update(key);
815 return;
816 }
817
818 preempt_disable();
819 mod = __module_address((unsigned long)key);
820 if (mod) {
821 stop = mod->jump_entries + mod->num_jump_entries;
822 init = mod->state == MODULE_STATE_COMING;
823 }
824 preempt_enable();
825#endif
826 entry = static_key_entries(key);
827 /* if there are no users, entry can be NULL */
828 if (entry)
829 __jump_label_update(key, entry, stop, init);
830}
831
832#ifdef CONFIG_STATIC_KEYS_SELFTEST
833static DEFINE_STATIC_KEY_TRUE(sk_true);
834static DEFINE_STATIC_KEY_FALSE(sk_false);
835
836static __init int jump_label_test(void)
837{
838 int i;
839
840 for (i = 0; i < 2; i++) {
841 WARN_ON(static_key_enabled(&sk_true.key) != true);
842 WARN_ON(static_key_enabled(&sk_false.key) != false);
843
844 WARN_ON(!static_branch_likely(&sk_true));
845 WARN_ON(!static_branch_unlikely(&sk_true));
846 WARN_ON(static_branch_likely(&sk_false));
847 WARN_ON(static_branch_unlikely(&sk_false));
848
849 static_branch_disable(&sk_true);
850 static_branch_enable(&sk_false);
851
852 WARN_ON(static_key_enabled(&sk_true.key) == true);
853 WARN_ON(static_key_enabled(&sk_false.key) == false);
854
855 WARN_ON(static_branch_likely(&sk_true));
856 WARN_ON(static_branch_unlikely(&sk_true));
857 WARN_ON(!static_branch_likely(&sk_false));
858 WARN_ON(!static_branch_unlikely(&sk_false));
859
860 static_branch_enable(&sk_true);
861 static_branch_disable(&sk_false);
862 }
863
864 return 0;
865}
866early_initcall(jump_label_test);
867#endif /* STATIC_KEYS_SELFTEST */