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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/dec() down the slow path, and it is non-zero
135 * so it counts as "enabled" in jump_label_update().
136 *
137 * The INT_MAX overflow condition is either used by the networking
138 * code to reset or detected in the slow path of
139 * static_key_slow_inc_cpuslocked().
140 */
141 v = atomic_read(&key->enabled);
142 do {
143 if (v <= 0 || v == INT_MAX)
144 return false;
145 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
146
147 return true;
148}
149EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
150
151bool static_key_slow_inc_cpuslocked(struct static_key *key)
152{
153 lockdep_assert_cpus_held();
154
155 /*
156 * Careful if we get concurrent static_key_slow_inc/dec() calls;
157 * later calls must wait for the first one to _finish_ the
158 * jump_label_update() process. At the same time, however,
159 * the jump_label_update() call below wants to see
160 * static_key_enabled(&key) for jumps to be updated properly.
161 */
162 if (static_key_fast_inc_not_disabled(key))
163 return true;
164
165 guard(mutex)(&jump_label_mutex);
166 /* Try to mark it as 'enabling in progress. */
167 if (!atomic_cmpxchg(&key->enabled, 0, -1)) {
168 jump_label_update(key);
169 /*
170 * Ensure that when static_key_fast_inc_not_disabled() or
171 * static_key_dec_not_one() observe the positive value,
172 * they must also observe all the text changes.
173 */
174 atomic_set_release(&key->enabled, 1);
175 } else {
176 /*
177 * While holding the mutex this should never observe
178 * anything else than a value >= 1 and succeed
179 */
180 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key)))
181 return false;
182 }
183 return true;
184}
185
186bool static_key_slow_inc(struct static_key *key)
187{
188 bool ret;
189
190 cpus_read_lock();
191 ret = static_key_slow_inc_cpuslocked(key);
192 cpus_read_unlock();
193 return ret;
194}
195EXPORT_SYMBOL_GPL(static_key_slow_inc);
196
197void static_key_enable_cpuslocked(struct static_key *key)
198{
199 STATIC_KEY_CHECK_USE(key);
200 lockdep_assert_cpus_held();
201
202 if (atomic_read(&key->enabled) > 0) {
203 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
204 return;
205 }
206
207 jump_label_lock();
208 if (atomic_read(&key->enabled) == 0) {
209 atomic_set(&key->enabled, -1);
210 jump_label_update(key);
211 /*
212 * See static_key_slow_inc().
213 */
214 atomic_set_release(&key->enabled, 1);
215 }
216 jump_label_unlock();
217}
218EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
219
220void static_key_enable(struct static_key *key)
221{
222 cpus_read_lock();
223 static_key_enable_cpuslocked(key);
224 cpus_read_unlock();
225}
226EXPORT_SYMBOL_GPL(static_key_enable);
227
228void static_key_disable_cpuslocked(struct static_key *key)
229{
230 STATIC_KEY_CHECK_USE(key);
231 lockdep_assert_cpus_held();
232
233 if (atomic_read(&key->enabled) != 1) {
234 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
235 return;
236 }
237
238 jump_label_lock();
239 if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
240 jump_label_update(key);
241 jump_label_unlock();
242}
243EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
244
245void static_key_disable(struct static_key *key)
246{
247 cpus_read_lock();
248 static_key_disable_cpuslocked(key);
249 cpus_read_unlock();
250}
251EXPORT_SYMBOL_GPL(static_key_disable);
252
253static bool static_key_dec_not_one(struct static_key *key)
254{
255 int v;
256
257 /*
258 * Go into the slow path if key::enabled is less than or equal than
259 * one. One is valid to shut down the key, anything less than one
260 * is an imbalance, which is handled at the call site.
261 *
262 * That includes the special case of '-1' which is set in
263 * static_key_slow_inc_cpuslocked(), but that's harmless as it is
264 * fully serialized in the slow path below. By the time this task
265 * acquires the jump label lock the value is back to one and the
266 * retry under the lock must succeed.
267 */
268 v = atomic_read(&key->enabled);
269 do {
270 /*
271 * Warn about the '-1' case though; since that means a
272 * decrement is concurrent with a first (0->1) increment. IOW
273 * people are trying to disable something that wasn't yet fully
274 * enabled. This suggests an ordering problem on the user side.
275 */
276 WARN_ON_ONCE(v < 0);
277
278 /*
279 * Warn about underflow, and lie about success in an attempt to
280 * not make things worse.
281 */
282 if (WARN_ON_ONCE(v == 0))
283 return true;
284
285 if (v <= 1)
286 return false;
287 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v - 1)));
288
289 return true;
290}
291
292static void __static_key_slow_dec_cpuslocked(struct static_key *key)
293{
294 lockdep_assert_cpus_held();
295 int val;
296
297 if (static_key_dec_not_one(key))
298 return;
299
300 guard(mutex)(&jump_label_mutex);
301 val = atomic_read(&key->enabled);
302 /*
303 * It should be impossible to observe -1 with jump_label_mutex held,
304 * see static_key_slow_inc_cpuslocked().
305 */
306 if (WARN_ON_ONCE(val == -1))
307 return;
308 /*
309 * Cannot already be 0, something went sideways.
310 */
311 if (WARN_ON_ONCE(val == 0))
312 return;
313
314 if (atomic_dec_and_test(&key->enabled))
315 jump_label_update(key);
316}
317
318static void __static_key_slow_dec(struct static_key *key)
319{
320 cpus_read_lock();
321 __static_key_slow_dec_cpuslocked(key);
322 cpus_read_unlock();
323}
324
325void jump_label_update_timeout(struct work_struct *work)
326{
327 struct static_key_deferred *key =
328 container_of(work, struct static_key_deferred, work.work);
329 __static_key_slow_dec(&key->key);
330}
331EXPORT_SYMBOL_GPL(jump_label_update_timeout);
332
333void static_key_slow_dec(struct static_key *key)
334{
335 STATIC_KEY_CHECK_USE(key);
336 __static_key_slow_dec(key);
337}
338EXPORT_SYMBOL_GPL(static_key_slow_dec);
339
340void static_key_slow_dec_cpuslocked(struct static_key *key)
341{
342 STATIC_KEY_CHECK_USE(key);
343 __static_key_slow_dec_cpuslocked(key);
344}
345
346void __static_key_slow_dec_deferred(struct static_key *key,
347 struct delayed_work *work,
348 unsigned long timeout)
349{
350 STATIC_KEY_CHECK_USE(key);
351
352 if (static_key_dec_not_one(key))
353 return;
354
355 schedule_delayed_work(work, timeout);
356}
357EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
358
359void __static_key_deferred_flush(void *key, struct delayed_work *work)
360{
361 STATIC_KEY_CHECK_USE(key);
362 flush_delayed_work(work);
363}
364EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
365
366void jump_label_rate_limit(struct static_key_deferred *key,
367 unsigned long rl)
368{
369 STATIC_KEY_CHECK_USE(key);
370 key->timeout = rl;
371 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
372}
373EXPORT_SYMBOL_GPL(jump_label_rate_limit);
374
375static int addr_conflict(struct jump_entry *entry, void *start, void *end)
376{
377 if (jump_entry_code(entry) <= (unsigned long)end &&
378 jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
379 return 1;
380
381 return 0;
382}
383
384static int __jump_label_text_reserved(struct jump_entry *iter_start,
385 struct jump_entry *iter_stop, void *start, void *end, bool init)
386{
387 struct jump_entry *iter;
388
389 iter = iter_start;
390 while (iter < iter_stop) {
391 if (init || !jump_entry_is_init(iter)) {
392 if (addr_conflict(iter, start, end))
393 return 1;
394 }
395 iter++;
396 }
397
398 return 0;
399}
400
401#ifndef arch_jump_label_transform_static
402static void arch_jump_label_transform_static(struct jump_entry *entry,
403 enum jump_label_type type)
404{
405 /* nothing to do on most architectures */
406}
407#endif
408
409static inline struct jump_entry *static_key_entries(struct static_key *key)
410{
411 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
412 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
413}
414
415static inline bool static_key_type(struct static_key *key)
416{
417 return key->type & JUMP_TYPE_TRUE;
418}
419
420static inline bool static_key_linked(struct static_key *key)
421{
422 return key->type & JUMP_TYPE_LINKED;
423}
424
425static inline void static_key_clear_linked(struct static_key *key)
426{
427 key->type &= ~JUMP_TYPE_LINKED;
428}
429
430static inline void static_key_set_linked(struct static_key *key)
431{
432 key->type |= JUMP_TYPE_LINKED;
433}
434
435/***
436 * A 'struct static_key' uses a union such that it either points directly
437 * to a table of 'struct jump_entry' or to a linked list of modules which in
438 * turn point to 'struct jump_entry' tables.
439 *
440 * The two lower bits of the pointer are used to keep track of which pointer
441 * type is in use and to store the initial branch direction, we use an access
442 * function which preserves these bits.
443 */
444static void static_key_set_entries(struct static_key *key,
445 struct jump_entry *entries)
446{
447 unsigned long type;
448
449 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
450 type = key->type & JUMP_TYPE_MASK;
451 key->entries = entries;
452 key->type |= type;
453}
454
455static enum jump_label_type jump_label_type(struct jump_entry *entry)
456{
457 struct static_key *key = jump_entry_key(entry);
458 bool enabled = static_key_enabled(key);
459 bool branch = jump_entry_is_branch(entry);
460
461 /* See the comment in linux/jump_label.h */
462 return enabled ^ branch;
463}
464
465static bool jump_label_can_update(struct jump_entry *entry, bool init)
466{
467 /*
468 * Cannot update code that was in an init text area.
469 */
470 if (!init && jump_entry_is_init(entry))
471 return false;
472
473 if (!kernel_text_address(jump_entry_code(entry))) {
474 /*
475 * This skips patching built-in __exit, which
476 * is part of init_section_contains() but is
477 * not part of kernel_text_address().
478 *
479 * Skipping built-in __exit is fine since it
480 * will never be executed.
481 */
482 WARN_ONCE(!jump_entry_is_init(entry),
483 "can't patch jump_label at %pS",
484 (void *)jump_entry_code(entry));
485 return false;
486 }
487
488 return true;
489}
490
491#ifndef HAVE_JUMP_LABEL_BATCH
492static void __jump_label_update(struct static_key *key,
493 struct jump_entry *entry,
494 struct jump_entry *stop,
495 bool init)
496{
497 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
498 if (jump_label_can_update(entry, init))
499 arch_jump_label_transform(entry, jump_label_type(entry));
500 }
501}
502#else
503static void __jump_label_update(struct static_key *key,
504 struct jump_entry *entry,
505 struct jump_entry *stop,
506 bool init)
507{
508 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
509
510 if (!jump_label_can_update(entry, init))
511 continue;
512
513 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
514 /*
515 * Queue is full: Apply the current queue and try again.
516 */
517 arch_jump_label_transform_apply();
518 BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
519 }
520 }
521 arch_jump_label_transform_apply();
522}
523#endif
524
525void __init jump_label_init(void)
526{
527 struct jump_entry *iter_start = __start___jump_table;
528 struct jump_entry *iter_stop = __stop___jump_table;
529 struct static_key *key = NULL;
530 struct jump_entry *iter;
531
532 /*
533 * Since we are initializing the static_key.enabled field with
534 * with the 'raw' int values (to avoid pulling in atomic.h) in
535 * jump_label.h, let's make sure that is safe. There are only two
536 * cases to check since we initialize to 0 or 1.
537 */
538 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
539 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
540
541 if (static_key_initialized)
542 return;
543
544 cpus_read_lock();
545 jump_label_lock();
546 jump_label_sort_entries(iter_start, iter_stop);
547
548 for (iter = iter_start; iter < iter_stop; iter++) {
549 struct static_key *iterk;
550 bool in_init;
551
552 /* rewrite NOPs */
553 if (jump_label_type(iter) == JUMP_LABEL_NOP)
554 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
555
556 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
557 jump_entry_set_init(iter, in_init);
558
559 iterk = jump_entry_key(iter);
560 if (iterk == key)
561 continue;
562
563 key = iterk;
564 static_key_set_entries(key, iter);
565 }
566 static_key_initialized = true;
567 jump_label_unlock();
568 cpus_read_unlock();
569}
570
571static inline bool static_key_sealed(struct static_key *key)
572{
573 return (key->type & JUMP_TYPE_LINKED) && !(key->type & ~JUMP_TYPE_MASK);
574}
575
576static inline void static_key_seal(struct static_key *key)
577{
578 unsigned long type = key->type & JUMP_TYPE_TRUE;
579 key->type = JUMP_TYPE_LINKED | type;
580}
581
582void jump_label_init_ro(void)
583{
584 struct jump_entry *iter_start = __start___jump_table;
585 struct jump_entry *iter_stop = __stop___jump_table;
586 struct jump_entry *iter;
587
588 if (WARN_ON_ONCE(!static_key_initialized))
589 return;
590
591 cpus_read_lock();
592 jump_label_lock();
593
594 for (iter = iter_start; iter < iter_stop; iter++) {
595 struct static_key *iterk = jump_entry_key(iter);
596
597 if (!is_kernel_ro_after_init((unsigned long)iterk))
598 continue;
599
600 if (static_key_sealed(iterk))
601 continue;
602
603 static_key_seal(iterk);
604 }
605
606 jump_label_unlock();
607 cpus_read_unlock();
608}
609
610#ifdef CONFIG_MODULES
611
612enum jump_label_type jump_label_init_type(struct jump_entry *entry)
613{
614 struct static_key *key = jump_entry_key(entry);
615 bool type = static_key_type(key);
616 bool branch = jump_entry_is_branch(entry);
617
618 /* See the comment in linux/jump_label.h */
619 return type ^ branch;
620}
621
622struct static_key_mod {
623 struct static_key_mod *next;
624 struct jump_entry *entries;
625 struct module *mod;
626};
627
628static inline struct static_key_mod *static_key_mod(struct static_key *key)
629{
630 WARN_ON_ONCE(!static_key_linked(key));
631 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
632}
633
634/***
635 * key->type and key->next are the same via union.
636 * This sets key->next and preserves the type bits.
637 *
638 * See additional comments above static_key_set_entries().
639 */
640static void static_key_set_mod(struct static_key *key,
641 struct static_key_mod *mod)
642{
643 unsigned long type;
644
645 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
646 type = key->type & JUMP_TYPE_MASK;
647 key->next = mod;
648 key->type |= type;
649}
650
651static int __jump_label_mod_text_reserved(void *start, void *end)
652{
653 struct module *mod;
654 int ret;
655
656 preempt_disable();
657 mod = __module_text_address((unsigned long)start);
658 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
659 if (!try_module_get(mod))
660 mod = NULL;
661 preempt_enable();
662
663 if (!mod)
664 return 0;
665
666 ret = __jump_label_text_reserved(mod->jump_entries,
667 mod->jump_entries + mod->num_jump_entries,
668 start, end, mod->state == MODULE_STATE_COMING);
669
670 module_put(mod);
671
672 return ret;
673}
674
675static void __jump_label_mod_update(struct static_key *key)
676{
677 struct static_key_mod *mod;
678
679 for (mod = static_key_mod(key); mod; mod = mod->next) {
680 struct jump_entry *stop;
681 struct module *m;
682
683 /*
684 * NULL if the static_key is defined in a module
685 * that does not use it
686 */
687 if (!mod->entries)
688 continue;
689
690 m = mod->mod;
691 if (!m)
692 stop = __stop___jump_table;
693 else
694 stop = m->jump_entries + m->num_jump_entries;
695 __jump_label_update(key, mod->entries, stop,
696 m && m->state == MODULE_STATE_COMING);
697 }
698}
699
700static int jump_label_add_module(struct module *mod)
701{
702 struct jump_entry *iter_start = mod->jump_entries;
703 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
704 struct jump_entry *iter;
705 struct static_key *key = NULL;
706 struct static_key_mod *jlm, *jlm2;
707
708 /* if the module doesn't have jump label entries, just return */
709 if (iter_start == iter_stop)
710 return 0;
711
712 jump_label_sort_entries(iter_start, iter_stop);
713
714 for (iter = iter_start; iter < iter_stop; iter++) {
715 struct static_key *iterk;
716 bool in_init;
717
718 in_init = within_module_init(jump_entry_code(iter), mod);
719 jump_entry_set_init(iter, in_init);
720
721 iterk = jump_entry_key(iter);
722 if (iterk == key)
723 continue;
724
725 key = iterk;
726 if (within_module((unsigned long)key, mod)) {
727 static_key_set_entries(key, iter);
728 continue;
729 }
730
731 /*
732 * If the key was sealed at init, then there's no need to keep a
733 * reference to its module entries - just patch them now and be
734 * done with it.
735 */
736 if (static_key_sealed(key))
737 goto do_poke;
738
739 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
740 if (!jlm)
741 return -ENOMEM;
742 if (!static_key_linked(key)) {
743 jlm2 = kzalloc(sizeof(struct static_key_mod),
744 GFP_KERNEL);
745 if (!jlm2) {
746 kfree(jlm);
747 return -ENOMEM;
748 }
749 preempt_disable();
750 jlm2->mod = __module_address((unsigned long)key);
751 preempt_enable();
752 jlm2->entries = static_key_entries(key);
753 jlm2->next = NULL;
754 static_key_set_mod(key, jlm2);
755 static_key_set_linked(key);
756 }
757 jlm->mod = mod;
758 jlm->entries = iter;
759 jlm->next = static_key_mod(key);
760 static_key_set_mod(key, jlm);
761 static_key_set_linked(key);
762
763 /* Only update if we've changed from our initial state */
764do_poke:
765 if (jump_label_type(iter) != jump_label_init_type(iter))
766 __jump_label_update(key, iter, iter_stop, true);
767 }
768
769 return 0;
770}
771
772static void jump_label_del_module(struct module *mod)
773{
774 struct jump_entry *iter_start = mod->jump_entries;
775 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
776 struct jump_entry *iter;
777 struct static_key *key = NULL;
778 struct static_key_mod *jlm, **prev;
779
780 for (iter = iter_start; iter < iter_stop; iter++) {
781 if (jump_entry_key(iter) == key)
782 continue;
783
784 key = jump_entry_key(iter);
785
786 if (within_module((unsigned long)key, mod))
787 continue;
788
789 /* No @jlm allocated because key was sealed at init. */
790 if (static_key_sealed(key))
791 continue;
792
793 /* No memory during module load */
794 if (WARN_ON(!static_key_linked(key)))
795 continue;
796
797 prev = &key->next;
798 jlm = static_key_mod(key);
799
800 while (jlm && jlm->mod != mod) {
801 prev = &jlm->next;
802 jlm = jlm->next;
803 }
804
805 /* No memory during module load */
806 if (WARN_ON(!jlm))
807 continue;
808
809 if (prev == &key->next)
810 static_key_set_mod(key, jlm->next);
811 else
812 *prev = jlm->next;
813
814 kfree(jlm);
815
816 jlm = static_key_mod(key);
817 /* if only one etry is left, fold it back into the static_key */
818 if (jlm->next == NULL) {
819 static_key_set_entries(key, jlm->entries);
820 static_key_clear_linked(key);
821 kfree(jlm);
822 }
823 }
824}
825
826static int
827jump_label_module_notify(struct notifier_block *self, unsigned long val,
828 void *data)
829{
830 struct module *mod = data;
831 int ret = 0;
832
833 cpus_read_lock();
834 jump_label_lock();
835
836 switch (val) {
837 case MODULE_STATE_COMING:
838 ret = jump_label_add_module(mod);
839 if (ret) {
840 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
841 jump_label_del_module(mod);
842 }
843 break;
844 case MODULE_STATE_GOING:
845 jump_label_del_module(mod);
846 break;
847 }
848
849 jump_label_unlock();
850 cpus_read_unlock();
851
852 return notifier_from_errno(ret);
853}
854
855static struct notifier_block jump_label_module_nb = {
856 .notifier_call = jump_label_module_notify,
857 .priority = 1, /* higher than tracepoints */
858};
859
860static __init int jump_label_init_module(void)
861{
862 return register_module_notifier(&jump_label_module_nb);
863}
864early_initcall(jump_label_init_module);
865
866#endif /* CONFIG_MODULES */
867
868/***
869 * jump_label_text_reserved - check if addr range is reserved
870 * @start: start text addr
871 * @end: end text addr
872 *
873 * checks if the text addr located between @start and @end
874 * overlaps with any of the jump label patch addresses. Code
875 * that wants to modify kernel text should first verify that
876 * it does not overlap with any of the jump label addresses.
877 * Caller must hold jump_label_mutex.
878 *
879 * returns 1 if there is an overlap, 0 otherwise
880 */
881int jump_label_text_reserved(void *start, void *end)
882{
883 bool init = system_state < SYSTEM_RUNNING;
884 int ret = __jump_label_text_reserved(__start___jump_table,
885 __stop___jump_table, start, end, init);
886
887 if (ret)
888 return ret;
889
890#ifdef CONFIG_MODULES
891 ret = __jump_label_mod_text_reserved(start, end);
892#endif
893 return ret;
894}
895
896static void jump_label_update(struct static_key *key)
897{
898 struct jump_entry *stop = __stop___jump_table;
899 bool init = system_state < SYSTEM_RUNNING;
900 struct jump_entry *entry;
901#ifdef CONFIG_MODULES
902 struct module *mod;
903
904 if (static_key_linked(key)) {
905 __jump_label_mod_update(key);
906 return;
907 }
908
909 preempt_disable();
910 mod = __module_address((unsigned long)key);
911 if (mod) {
912 stop = mod->jump_entries + mod->num_jump_entries;
913 init = mod->state == MODULE_STATE_COMING;
914 }
915 preempt_enable();
916#endif
917 entry = static_key_entries(key);
918 /* if there are no users, entry can be NULL */
919 if (entry)
920 __jump_label_update(key, entry, stop, init);
921}
922
923#ifdef CONFIG_STATIC_KEYS_SELFTEST
924static DEFINE_STATIC_KEY_TRUE(sk_true);
925static DEFINE_STATIC_KEY_FALSE(sk_false);
926
927static __init int jump_label_test(void)
928{
929 int i;
930
931 for (i = 0; i < 2; i++) {
932 WARN_ON(static_key_enabled(&sk_true.key) != true);
933 WARN_ON(static_key_enabled(&sk_false.key) != false);
934
935 WARN_ON(!static_branch_likely(&sk_true));
936 WARN_ON(!static_branch_unlikely(&sk_true));
937 WARN_ON(static_branch_likely(&sk_false));
938 WARN_ON(static_branch_unlikely(&sk_false));
939
940 static_branch_disable(&sk_true);
941 static_branch_enable(&sk_false);
942
943 WARN_ON(static_key_enabled(&sk_true.key) == true);
944 WARN_ON(static_key_enabled(&sk_false.key) == false);
945
946 WARN_ON(static_branch_likely(&sk_true));
947 WARN_ON(static_branch_unlikely(&sk_true));
948 WARN_ON(!static_branch_likely(&sk_false));
949 WARN_ON(!static_branch_unlikely(&sk_false));
950
951 static_branch_enable(&sk_true);
952 static_branch_disable(&sk_false);
953 }
954
955 return 0;
956}
957early_initcall(jump_label_test);
958#endif /* STATIC_KEYS_SELFTEST */