Merge branch 'tip/perf/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/roste...
[linux-3.10.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/jump_label.h>
16
17 #ifdef HAVE_JUMP_LABEL
18
19 /* mutex to protect coming/going of the the jump_label table */
20 static DEFINE_MUTEX(jump_label_mutex);
21
22 void jump_label_lock(void)
23 {
24         mutex_lock(&jump_label_mutex);
25 }
26
27 void jump_label_unlock(void)
28 {
29         mutex_unlock(&jump_label_mutex);
30 }
31
32 bool jump_label_enabled(struct jump_label_key *key)
33 {
34         return !!atomic_read(&key->enabled);
35 }
36
37 static int jump_label_cmp(const void *a, const void *b)
38 {
39         const struct jump_entry *jea = a;
40         const struct jump_entry *jeb = b;
41
42         if (jea->key < jeb->key)
43                 return -1;
44
45         if (jea->key > jeb->key)
46                 return 1;
47
48         return 0;
49 }
50
51 static void
52 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
53 {
54         unsigned long size;
55
56         size = (((unsigned long)stop - (unsigned long)start)
57                                         / sizeof(struct jump_entry));
58         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
59 }
60
61 static void jump_label_update(struct jump_label_key *key, int enable);
62
63 void jump_label_inc(struct jump_label_key *key)
64 {
65         if (atomic_inc_not_zero(&key->enabled))
66                 return;
67
68         jump_label_lock();
69         if (atomic_read(&key->enabled) == 0)
70                 jump_label_update(key, JUMP_LABEL_ENABLE);
71         atomic_inc(&key->enabled);
72         jump_label_unlock();
73 }
74
75 static void __jump_label_dec(struct jump_label_key *key,
76                 unsigned long rate_limit, struct delayed_work *work)
77 {
78         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
79                 return;
80
81         if (rate_limit) {
82                 atomic_inc(&key->enabled);
83                 schedule_delayed_work(work, rate_limit);
84         } else
85                 jump_label_update(key, JUMP_LABEL_DISABLE);
86
87         jump_label_unlock();
88 }
89
90 static void jump_label_update_timeout(struct work_struct *work)
91 {
92         struct jump_label_key_deferred *key =
93                 container_of(work, struct jump_label_key_deferred, work.work);
94         __jump_label_dec(&key->key, 0, NULL);
95 }
96
97 void jump_label_dec(struct jump_label_key *key)
98 {
99         __jump_label_dec(key, 0, NULL);
100 }
101
102 void jump_label_dec_deferred(struct jump_label_key_deferred *key)
103 {
104         __jump_label_dec(&key->key, key->timeout, &key->work);
105 }
106
107
108 void jump_label_rate_limit(struct jump_label_key_deferred *key,
109                 unsigned long rl)
110 {
111         key->timeout = rl;
112         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
113 }
114
115 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
116 {
117         if (entry->code <= (unsigned long)end &&
118                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
119                 return 1;
120
121         return 0;
122 }
123
124 static int __jump_label_text_reserved(struct jump_entry *iter_start,
125                 struct jump_entry *iter_stop, void *start, void *end)
126 {
127         struct jump_entry *iter;
128
129         iter = iter_start;
130         while (iter < iter_stop) {
131                 if (addr_conflict(iter, start, end))
132                         return 1;
133                 iter++;
134         }
135
136         return 0;
137 }
138
139 /* 
140  * Update code which is definitely not currently executing.
141  * Architectures which need heavyweight synchronization to modify
142  * running code can override this to make the non-live update case
143  * cheaper.
144  */
145 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
146                                             enum jump_label_type type)
147 {
148         arch_jump_label_transform(entry, type); 
149 }
150
151 static void __jump_label_update(struct jump_label_key *key,
152                                 struct jump_entry *entry,
153                                 struct jump_entry *stop, int enable)
154 {
155         for (; (entry < stop) &&
156               (entry->key == (jump_label_t)(unsigned long)key);
157               entry++) {
158                 /*
159                  * entry->code set to 0 invalidates module init text sections
160                  * kernel_text_address() verifies we are not in core kernel
161                  * init code, see jump_label_invalidate_module_init().
162                  */
163                 if (entry->code && kernel_text_address(entry->code))
164                         arch_jump_label_transform(entry, enable);
165         }
166 }
167
168 void __init jump_label_init(void)
169 {
170         struct jump_entry *iter_start = __start___jump_table;
171         struct jump_entry *iter_stop = __stop___jump_table;
172         struct jump_label_key *key = NULL;
173         struct jump_entry *iter;
174
175         jump_label_lock();
176         jump_label_sort_entries(iter_start, iter_stop);
177
178         for (iter = iter_start; iter < iter_stop; iter++) {
179                 struct jump_label_key *iterk;
180
181                 iterk = (struct jump_label_key *)(unsigned long)iter->key;
182                 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
183                                                  JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
184                 if (iterk == key)
185                         continue;
186
187                 key = iterk;
188                 key->entries = iter;
189 #ifdef CONFIG_MODULES
190                 key->next = NULL;
191 #endif
192         }
193         jump_label_unlock();
194 }
195
196 #ifdef CONFIG_MODULES
197
198 struct jump_label_mod {
199         struct jump_label_mod *next;
200         struct jump_entry *entries;
201         struct module *mod;
202 };
203
204 static int __jump_label_mod_text_reserved(void *start, void *end)
205 {
206         struct module *mod;
207
208         mod = __module_text_address((unsigned long)start);
209         if (!mod)
210                 return 0;
211
212         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
213
214         return __jump_label_text_reserved(mod->jump_entries,
215                                 mod->jump_entries + mod->num_jump_entries,
216                                 start, end);
217 }
218
219 static void __jump_label_mod_update(struct jump_label_key *key, int enable)
220 {
221         struct jump_label_mod *mod = key->next;
222
223         while (mod) {
224                 struct module *m = mod->mod;
225
226                 __jump_label_update(key, mod->entries,
227                                     m->jump_entries + m->num_jump_entries,
228                                     enable);
229                 mod = mod->next;
230         }
231 }
232
233 /***
234  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
235  * @mod: module to patch
236  *
237  * Allow for run-time selection of the optimal nops. Before the module
238  * loads patch these with arch_get_jump_label_nop(), which is specified by
239  * the arch specific jump label code.
240  */
241 void jump_label_apply_nops(struct module *mod)
242 {
243         struct jump_entry *iter_start = mod->jump_entries;
244         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
245         struct jump_entry *iter;
246
247         /* if the module doesn't have jump label entries, just return */
248         if (iter_start == iter_stop)
249                 return;
250
251         for (iter = iter_start; iter < iter_stop; iter++) {
252                 struct jump_label_key *iterk;
253
254                 iterk = (struct jump_label_key *)(unsigned long)iter->key;
255                 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
256                                 JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
257         }
258 }
259
260 static int jump_label_add_module(struct module *mod)
261 {
262         struct jump_entry *iter_start = mod->jump_entries;
263         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
264         struct jump_entry *iter;
265         struct jump_label_key *key = NULL;
266         struct jump_label_mod *jlm;
267
268         /* if the module doesn't have jump label entries, just return */
269         if (iter_start == iter_stop)
270                 return 0;
271
272         jump_label_sort_entries(iter_start, iter_stop);
273
274         for (iter = iter_start; iter < iter_stop; iter++) {
275                 if (iter->key == (jump_label_t)(unsigned long)key)
276                         continue;
277
278                 key = (struct jump_label_key *)(unsigned long)iter->key;
279
280                 if (__module_address(iter->key) == mod) {
281                         atomic_set(&key->enabled, 0);
282                         key->entries = iter;
283                         key->next = NULL;
284                         continue;
285                 }
286
287                 jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
288                 if (!jlm)
289                         return -ENOMEM;
290
291                 jlm->mod = mod;
292                 jlm->entries = iter;
293                 jlm->next = key->next;
294                 key->next = jlm;
295
296                 if (jump_label_enabled(key))
297                         __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE);
298         }
299
300         return 0;
301 }
302
303 static void jump_label_del_module(struct module *mod)
304 {
305         struct jump_entry *iter_start = mod->jump_entries;
306         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
307         struct jump_entry *iter;
308         struct jump_label_key *key = NULL;
309         struct jump_label_mod *jlm, **prev;
310
311         for (iter = iter_start; iter < iter_stop; iter++) {
312                 if (iter->key == (jump_label_t)(unsigned long)key)
313                         continue;
314
315                 key = (struct jump_label_key *)(unsigned long)iter->key;
316
317                 if (__module_address(iter->key) == mod)
318                         continue;
319
320                 prev = &key->next;
321                 jlm = key->next;
322
323                 while (jlm && jlm->mod != mod) {
324                         prev = &jlm->next;
325                         jlm = jlm->next;
326                 }
327
328                 if (jlm) {
329                         *prev = jlm->next;
330                         kfree(jlm);
331                 }
332         }
333 }
334
335 static void jump_label_invalidate_module_init(struct module *mod)
336 {
337         struct jump_entry *iter_start = mod->jump_entries;
338         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
339         struct jump_entry *iter;
340
341         for (iter = iter_start; iter < iter_stop; iter++) {
342                 if (within_module_init(iter->code, mod))
343                         iter->code = 0;
344         }
345 }
346
347 static int
348 jump_label_module_notify(struct notifier_block *self, unsigned long val,
349                          void *data)
350 {
351         struct module *mod = data;
352         int ret = 0;
353
354         switch (val) {
355         case MODULE_STATE_COMING:
356                 jump_label_lock();
357                 ret = jump_label_add_module(mod);
358                 if (ret)
359                         jump_label_del_module(mod);
360                 jump_label_unlock();
361                 break;
362         case MODULE_STATE_GOING:
363                 jump_label_lock();
364                 jump_label_del_module(mod);
365                 jump_label_unlock();
366                 break;
367         case MODULE_STATE_LIVE:
368                 jump_label_lock();
369                 jump_label_invalidate_module_init(mod);
370                 jump_label_unlock();
371                 break;
372         }
373
374         return notifier_from_errno(ret);
375 }
376
377 struct notifier_block jump_label_module_nb = {
378         .notifier_call = jump_label_module_notify,
379         .priority = 1, /* higher than tracepoints */
380 };
381
382 static __init int jump_label_init_module(void)
383 {
384         return register_module_notifier(&jump_label_module_nb);
385 }
386 early_initcall(jump_label_init_module);
387
388 #endif /* CONFIG_MODULES */
389
390 /***
391  * jump_label_text_reserved - check if addr range is reserved
392  * @start: start text addr
393  * @end: end text addr
394  *
395  * checks if the text addr located between @start and @end
396  * overlaps with any of the jump label patch addresses. Code
397  * that wants to modify kernel text should first verify that
398  * it does not overlap with any of the jump label addresses.
399  * Caller must hold jump_label_mutex.
400  *
401  * returns 1 if there is an overlap, 0 otherwise
402  */
403 int jump_label_text_reserved(void *start, void *end)
404 {
405         int ret = __jump_label_text_reserved(__start___jump_table,
406                         __stop___jump_table, start, end);
407
408         if (ret)
409                 return ret;
410
411 #ifdef CONFIG_MODULES
412         ret = __jump_label_mod_text_reserved(start, end);
413 #endif
414         return ret;
415 }
416
417 static void jump_label_update(struct jump_label_key *key, int enable)
418 {
419         struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
420
421 #ifdef CONFIG_MODULES
422         struct module *mod = __module_address((jump_label_t)key);
423
424         __jump_label_mod_update(key, enable);
425
426         if (mod)
427                 stop = mod->jump_entries + mod->num_jump_entries;
428 #endif
429         /* if there are no users, entry can be NULL */
430         if (entry)
431                 __jump_label_update(key, entry, stop, enable);
432 }
433
434 #endif