Merge branch 'cpuidle' of https://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux...
[firefly-linux-kernel-4.4.55.git] / kernel / jump_label.c
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 */
21 static DEFINE_MUTEX(jump_label_mutex);
22
23 void jump_label_lock(void)
24 {
25         mutex_lock(&jump_label_mutex);
26 }
27
28 void jump_label_unlock(void)
29 {
30         mutex_unlock(&jump_label_mutex);
31 }
32
33 static 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
47 static void
48 jump_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
57 static void jump_label_update(struct static_key *key);
58
59 void 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_inc_return(&key->enabled) == 1)
67                 jump_label_update(key);
68         jump_label_unlock();
69 }
70 EXPORT_SYMBOL_GPL(static_key_slow_inc);
71
72 static void __static_key_slow_dec(struct static_key *key,
73                 unsigned long rate_limit, struct delayed_work *work)
74 {
75         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
76                 WARN(atomic_read(&key->enabled) < 0,
77                      "jump label: negative count!\n");
78                 return;
79         }
80
81         if (rate_limit) {
82                 atomic_inc(&key->enabled);
83                 schedule_delayed_work(work, rate_limit);
84         } else {
85                 jump_label_update(key);
86         }
87         jump_label_unlock();
88 }
89
90 static void jump_label_update_timeout(struct work_struct *work)
91 {
92         struct static_key_deferred *key =
93                 container_of(work, struct static_key_deferred, work.work);
94         __static_key_slow_dec(&key->key, 0, NULL);
95 }
96
97 void static_key_slow_dec(struct static_key *key)
98 {
99         STATIC_KEY_CHECK_USE();
100         __static_key_slow_dec(key, 0, NULL);
101 }
102 EXPORT_SYMBOL_GPL(static_key_slow_dec);
103
104 void static_key_slow_dec_deferred(struct static_key_deferred *key)
105 {
106         STATIC_KEY_CHECK_USE();
107         __static_key_slow_dec(&key->key, key->timeout, &key->work);
108 }
109 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
110
111 void jump_label_rate_limit(struct static_key_deferred *key,
112                 unsigned long rl)
113 {
114         STATIC_KEY_CHECK_USE();
115         key->timeout = rl;
116         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
117 }
118 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
119
120 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
121 {
122         if (entry->code <= (unsigned long)end &&
123                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
124                 return 1;
125
126         return 0;
127 }
128
129 static int __jump_label_text_reserved(struct jump_entry *iter_start,
130                 struct jump_entry *iter_stop, void *start, void *end)
131 {
132         struct jump_entry *iter;
133
134         iter = iter_start;
135         while (iter < iter_stop) {
136                 if (addr_conflict(iter, start, end))
137                         return 1;
138                 iter++;
139         }
140
141         return 0;
142 }
143
144 /*
145  * Update code which is definitely not currently executing.
146  * Architectures which need heavyweight synchronization to modify
147  * running code can override this to make the non-live update case
148  * cheaper.
149  */
150 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
151                                             enum jump_label_type type)
152 {
153         arch_jump_label_transform(entry, type);
154 }
155
156 static inline struct jump_entry *static_key_entries(struct static_key *key)
157 {
158         return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
159 }
160
161 static inline bool static_key_type(struct static_key *key)
162 {
163         return (unsigned long)key->entries & JUMP_TYPE_MASK;
164 }
165
166 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
167 {
168         return (struct static_key *)((unsigned long)entry->key & ~1UL);
169 }
170
171 static bool jump_entry_branch(struct jump_entry *entry)
172 {
173         return (unsigned long)entry->key & 1UL;
174 }
175
176 static enum jump_label_type jump_label_type(struct jump_entry *entry)
177 {
178         struct static_key *key = jump_entry_key(entry);
179         bool enabled = static_key_enabled(key);
180         bool branch = jump_entry_branch(entry);
181
182         /* See the comment in linux/jump_label.h */
183         return enabled ^ branch;
184 }
185
186 static void __jump_label_update(struct static_key *key,
187                                 struct jump_entry *entry,
188                                 struct jump_entry *stop)
189 {
190         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
191                 /*
192                  * entry->code set to 0 invalidates module init text sections
193                  * kernel_text_address() verifies we are not in core kernel
194                  * init code, see jump_label_invalidate_module_init().
195                  */
196                 if (entry->code && kernel_text_address(entry->code))
197                         arch_jump_label_transform(entry, jump_label_type(entry));
198         }
199 }
200
201 void __init jump_label_init(void)
202 {
203         struct jump_entry *iter_start = __start___jump_table;
204         struct jump_entry *iter_stop = __stop___jump_table;
205         struct static_key *key = NULL;
206         struct jump_entry *iter;
207
208         jump_label_lock();
209         jump_label_sort_entries(iter_start, iter_stop);
210
211         for (iter = iter_start; iter < iter_stop; iter++) {
212                 struct static_key *iterk;
213
214                 /* rewrite NOPs */
215                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
216                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
217
218                 iterk = jump_entry_key(iter);
219                 if (iterk == key)
220                         continue;
221
222                 key = iterk;
223                 /*
224                  * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
225                  */
226                 *((unsigned long *)&key->entries) += (unsigned long)iter;
227 #ifdef CONFIG_MODULES
228                 key->next = NULL;
229 #endif
230         }
231         static_key_initialized = true;
232         jump_label_unlock();
233 }
234
235 #ifdef CONFIG_MODULES
236
237 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
238 {
239         struct static_key *key = jump_entry_key(entry);
240         bool type = static_key_type(key);
241         bool branch = jump_entry_branch(entry);
242
243         /* See the comment in linux/jump_label.h */
244         return type ^ branch;
245 }
246
247 struct static_key_mod {
248         struct static_key_mod *next;
249         struct jump_entry *entries;
250         struct module *mod;
251 };
252
253 static int __jump_label_mod_text_reserved(void *start, void *end)
254 {
255         struct module *mod;
256
257         mod = __module_text_address((unsigned long)start);
258         if (!mod)
259                 return 0;
260
261         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
262
263         return __jump_label_text_reserved(mod->jump_entries,
264                                 mod->jump_entries + mod->num_jump_entries,
265                                 start, end);
266 }
267
268 static void __jump_label_mod_update(struct static_key *key)
269 {
270         struct static_key_mod *mod;
271
272         for (mod = key->next; mod; mod = mod->next) {
273                 struct module *m = mod->mod;
274
275                 __jump_label_update(key, mod->entries,
276                                     m->jump_entries + m->num_jump_entries);
277         }
278 }
279
280 /***
281  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
282  * @mod: module to patch
283  *
284  * Allow for run-time selection of the optimal nops. Before the module
285  * loads patch these with arch_get_jump_label_nop(), which is specified by
286  * the arch specific jump label code.
287  */
288 void jump_label_apply_nops(struct module *mod)
289 {
290         struct jump_entry *iter_start = mod->jump_entries;
291         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
292         struct jump_entry *iter;
293
294         /* if the module doesn't have jump label entries, just return */
295         if (iter_start == iter_stop)
296                 return;
297
298         for (iter = iter_start; iter < iter_stop; iter++) {
299                 /* Only write NOPs for arch_branch_static(). */
300                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
301                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
302         }
303 }
304
305 static int jump_label_add_module(struct module *mod)
306 {
307         struct jump_entry *iter_start = mod->jump_entries;
308         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
309         struct jump_entry *iter;
310         struct static_key *key = NULL;
311         struct static_key_mod *jlm;
312
313         /* if the module doesn't have jump label entries, just return */
314         if (iter_start == iter_stop)
315                 return 0;
316
317         jump_label_sort_entries(iter_start, iter_stop);
318
319         for (iter = iter_start; iter < iter_stop; iter++) {
320                 struct static_key *iterk;
321
322                 iterk = jump_entry_key(iter);
323                 if (iterk == key)
324                         continue;
325
326                 key = iterk;
327                 if (within_module(iter->key, mod)) {
328                         /*
329                          * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
330                          */
331                         *((unsigned long *)&key->entries) += (unsigned long)iter;
332                         key->next = NULL;
333                         continue;
334                 }
335                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
336                 if (!jlm)
337                         return -ENOMEM;
338                 jlm->mod = mod;
339                 jlm->entries = iter;
340                 jlm->next = key->next;
341                 key->next = jlm;
342
343                 /* Only update if we've changed from our initial state */
344                 if (jump_label_type(iter) != jump_label_init_type(iter))
345                         __jump_label_update(key, iter, iter_stop);
346         }
347
348         return 0;
349 }
350
351 static void jump_label_del_module(struct module *mod)
352 {
353         struct jump_entry *iter_start = mod->jump_entries;
354         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
355         struct jump_entry *iter;
356         struct static_key *key = NULL;
357         struct static_key_mod *jlm, **prev;
358
359         for (iter = iter_start; iter < iter_stop; iter++) {
360                 if (jump_entry_key(iter) == key)
361                         continue;
362
363                 key = jump_entry_key(iter);
364
365                 if (within_module(iter->key, mod))
366                         continue;
367
368                 prev = &key->next;
369                 jlm = key->next;
370
371                 while (jlm && jlm->mod != mod) {
372                         prev = &jlm->next;
373                         jlm = jlm->next;
374                 }
375
376                 if (jlm) {
377                         *prev = jlm->next;
378                         kfree(jlm);
379                 }
380         }
381 }
382
383 static void jump_label_invalidate_module_init(struct module *mod)
384 {
385         struct jump_entry *iter_start = mod->jump_entries;
386         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
387         struct jump_entry *iter;
388
389         for (iter = iter_start; iter < iter_stop; iter++) {
390                 if (within_module_init(iter->code, mod))
391                         iter->code = 0;
392         }
393 }
394
395 static int
396 jump_label_module_notify(struct notifier_block *self, unsigned long val,
397                          void *data)
398 {
399         struct module *mod = data;
400         int ret = 0;
401
402         switch (val) {
403         case MODULE_STATE_COMING:
404                 jump_label_lock();
405                 ret = jump_label_add_module(mod);
406                 if (ret)
407                         jump_label_del_module(mod);
408                 jump_label_unlock();
409                 break;
410         case MODULE_STATE_GOING:
411                 jump_label_lock();
412                 jump_label_del_module(mod);
413                 jump_label_unlock();
414                 break;
415         case MODULE_STATE_LIVE:
416                 jump_label_lock();
417                 jump_label_invalidate_module_init(mod);
418                 jump_label_unlock();
419                 break;
420         }
421
422         return notifier_from_errno(ret);
423 }
424
425 struct notifier_block jump_label_module_nb = {
426         .notifier_call = jump_label_module_notify,
427         .priority = 1, /* higher than tracepoints */
428 };
429
430 static __init int jump_label_init_module(void)
431 {
432         return register_module_notifier(&jump_label_module_nb);
433 }
434 early_initcall(jump_label_init_module);
435
436 #endif /* CONFIG_MODULES */
437
438 /***
439  * jump_label_text_reserved - check if addr range is reserved
440  * @start: start text addr
441  * @end: end text addr
442  *
443  * checks if the text addr located between @start and @end
444  * overlaps with any of the jump label patch addresses. Code
445  * that wants to modify kernel text should first verify that
446  * it does not overlap with any of the jump label addresses.
447  * Caller must hold jump_label_mutex.
448  *
449  * returns 1 if there is an overlap, 0 otherwise
450  */
451 int jump_label_text_reserved(void *start, void *end)
452 {
453         int ret = __jump_label_text_reserved(__start___jump_table,
454                         __stop___jump_table, start, end);
455
456         if (ret)
457                 return ret;
458
459 #ifdef CONFIG_MODULES
460         ret = __jump_label_mod_text_reserved(start, end);
461 #endif
462         return ret;
463 }
464
465 static void jump_label_update(struct static_key *key)
466 {
467         struct jump_entry *stop = __stop___jump_table;
468         struct jump_entry *entry = static_key_entries(key);
469 #ifdef CONFIG_MODULES
470         struct module *mod;
471
472         __jump_label_mod_update(key);
473
474         preempt_disable();
475         mod = __module_address((unsigned long)key);
476         if (mod)
477                 stop = mod->jump_entries + mod->num_jump_entries;
478         preempt_enable();
479 #endif
480         /* if there are no users, entry can be NULL */
481         if (entry)
482                 __jump_label_update(key, entry, stop);
483 }
484
485 #ifdef CONFIG_STATIC_KEYS_SELFTEST
486 static DEFINE_STATIC_KEY_TRUE(sk_true);
487 static DEFINE_STATIC_KEY_FALSE(sk_false);
488
489 static __init int jump_label_test(void)
490 {
491         int i;
492
493         for (i = 0; i < 2; i++) {
494                 WARN_ON(static_key_enabled(&sk_true.key) != true);
495                 WARN_ON(static_key_enabled(&sk_false.key) != false);
496
497                 WARN_ON(!static_branch_likely(&sk_true));
498                 WARN_ON(!static_branch_unlikely(&sk_true));
499                 WARN_ON(static_branch_likely(&sk_false));
500                 WARN_ON(static_branch_unlikely(&sk_false));
501
502                 static_branch_disable(&sk_true);
503                 static_branch_enable(&sk_false);
504
505                 WARN_ON(static_key_enabled(&sk_true.key) == true);
506                 WARN_ON(static_key_enabled(&sk_false.key) == false);
507
508                 WARN_ON(static_branch_likely(&sk_true));
509                 WARN_ON(static_branch_unlikely(&sk_true));
510                 WARN_ON(!static_branch_likely(&sk_false));
511                 WARN_ON(!static_branch_unlikely(&sk_false));
512
513                 static_branch_enable(&sk_true);
514                 static_branch_disable(&sk_false);
515         }
516
517         return 0;
518 }
519 late_initcall(jump_label_test);
520 #endif /* STATIC_KEYS_SELFTEST */
521
522 #endif /* HAVE_JUMP_LABEL */