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