Merge remote-tracking branch 'tip/perf/core' into kvm-updates/3.3
[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 EXPORT_SYMBOL_GPL(jump_label_inc);
75
76 static void __jump_label_dec(struct jump_label_key *key,
77                 unsigned long rate_limit, struct delayed_work *work)
78 {
79         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
80                 return;
81
82         if (rate_limit) {
83                 atomic_inc(&key->enabled);
84                 schedule_delayed_work(work, rate_limit);
85         } else
86                 jump_label_update(key, JUMP_LABEL_DISABLE);
87
88         jump_label_unlock();
89 }
90 EXPORT_SYMBOL_GPL(jump_label_dec);
91
92 static void jump_label_update_timeout(struct work_struct *work)
93 {
94         struct jump_label_key_deferred *key =
95                 container_of(work, struct jump_label_key_deferred, work.work);
96         __jump_label_dec(&key->key, 0, NULL);
97 }
98
99 void jump_label_dec(struct jump_label_key *key)
100 {
101         __jump_label_dec(key, 0, NULL);
102 }
103
104 void jump_label_dec_deferred(struct jump_label_key_deferred *key)
105 {
106         __jump_label_dec(&key->key, key->timeout, &key->work);
107 }
108
109
110 void jump_label_rate_limit(struct jump_label_key_deferred *key,
111                 unsigned long rl)
112 {
113         key->timeout = rl;
114         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
115 }
116
117 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
118 {
119         if (entry->code <= (unsigned long)end &&
120                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
121                 return 1;
122
123         return 0;
124 }
125
126 static int __jump_label_text_reserved(struct jump_entry *iter_start,
127                 struct jump_entry *iter_stop, void *start, void *end)
128 {
129         struct jump_entry *iter;
130
131         iter = iter_start;
132         while (iter < iter_stop) {
133                 if (addr_conflict(iter, start, end))
134                         return 1;
135                 iter++;
136         }
137
138         return 0;
139 }
140
141 /* 
142  * Update code which is definitely not currently executing.
143  * Architectures which need heavyweight synchronization to modify
144  * running code can override this to make the non-live update case
145  * cheaper.
146  */
147 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
148                                             enum jump_label_type type)
149 {
150         arch_jump_label_transform(entry, type); 
151 }
152
153 static void __jump_label_update(struct jump_label_key *key,
154                                 struct jump_entry *entry,
155                                 struct jump_entry *stop, int enable)
156 {
157         for (; (entry < stop) &&
158               (entry->key == (jump_label_t)(unsigned long)key);
159               entry++) {
160                 /*
161                  * entry->code set to 0 invalidates module init text sections
162                  * kernel_text_address() verifies we are not in core kernel
163                  * init code, see jump_label_invalidate_module_init().
164                  */
165                 if (entry->code && kernel_text_address(entry->code))
166                         arch_jump_label_transform(entry, enable);
167         }
168 }
169
170 void __init jump_label_init(void)
171 {
172         struct jump_entry *iter_start = __start___jump_table;
173         struct jump_entry *iter_stop = __stop___jump_table;
174         struct jump_label_key *key = NULL;
175         struct jump_entry *iter;
176
177         jump_label_lock();
178         jump_label_sort_entries(iter_start, iter_stop);
179
180         for (iter = iter_start; iter < iter_stop; iter++) {
181                 struct jump_label_key *iterk;
182
183                 iterk = (struct jump_label_key *)(unsigned long)iter->key;
184                 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
185                                                  JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
186                 if (iterk == key)
187                         continue;
188
189                 key = iterk;
190                 key->entries = iter;
191 #ifdef CONFIG_MODULES
192                 key->next = NULL;
193 #endif
194         }
195         jump_label_unlock();
196 }
197
198 #ifdef CONFIG_MODULES
199
200 struct jump_label_mod {
201         struct jump_label_mod *next;
202         struct jump_entry *entries;
203         struct module *mod;
204 };
205
206 static int __jump_label_mod_text_reserved(void *start, void *end)
207 {
208         struct module *mod;
209
210         mod = __module_text_address((unsigned long)start);
211         if (!mod)
212                 return 0;
213
214         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
215
216         return __jump_label_text_reserved(mod->jump_entries,
217                                 mod->jump_entries + mod->num_jump_entries,
218                                 start, end);
219 }
220
221 static void __jump_label_mod_update(struct jump_label_key *key, int enable)
222 {
223         struct jump_label_mod *mod = key->next;
224
225         while (mod) {
226                 struct module *m = mod->mod;
227
228                 __jump_label_update(key, mod->entries,
229                                     m->jump_entries + m->num_jump_entries,
230                                     enable);
231                 mod = mod->next;
232         }
233 }
234
235 /***
236  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
237  * @mod: module to patch
238  *
239  * Allow for run-time selection of the optimal nops. Before the module
240  * loads patch these with arch_get_jump_label_nop(), which is specified by
241  * the arch specific jump label code.
242  */
243 void jump_label_apply_nops(struct module *mod)
244 {
245         struct jump_entry *iter_start = mod->jump_entries;
246         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
247         struct jump_entry *iter;
248
249         /* if the module doesn't have jump label entries, just return */
250         if (iter_start == iter_stop)
251                 return;
252
253         for (iter = iter_start; iter < iter_stop; iter++) {
254                 struct jump_label_key *iterk;
255
256                 iterk = (struct jump_label_key *)(unsigned long)iter->key;
257                 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
258                                 JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
259         }
260 }
261
262 static int jump_label_add_module(struct module *mod)
263 {
264         struct jump_entry *iter_start = mod->jump_entries;
265         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
266         struct jump_entry *iter;
267         struct jump_label_key *key = NULL;
268         struct jump_label_mod *jlm;
269
270         /* if the module doesn't have jump label entries, just return */
271         if (iter_start == iter_stop)
272                 return 0;
273
274         jump_label_sort_entries(iter_start, iter_stop);
275
276         for (iter = iter_start; iter < iter_stop; iter++) {
277                 if (iter->key == (jump_label_t)(unsigned long)key)
278                         continue;
279
280                 key = (struct jump_label_key *)(unsigned long)iter->key;
281
282                 if (__module_address(iter->key) == mod) {
283                         atomic_set(&key->enabled, 0);
284                         key->entries = iter;
285                         key->next = NULL;
286                         continue;
287                 }
288
289                 jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
290                 if (!jlm)
291                         return -ENOMEM;
292
293                 jlm->mod = mod;
294                 jlm->entries = iter;
295                 jlm->next = key->next;
296                 key->next = jlm;
297
298                 if (jump_label_enabled(key))
299                         __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE);
300         }
301
302         return 0;
303 }
304
305 static void jump_label_del_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 jump_label_key *key = NULL;
311         struct jump_label_mod *jlm, **prev;
312
313         for (iter = iter_start; iter < iter_stop; iter++) {
314                 if (iter->key == (jump_label_t)(unsigned long)key)
315                         continue;
316
317                 key = (struct jump_label_key *)(unsigned long)iter->key;
318
319                 if (__module_address(iter->key) == mod)
320                         continue;
321
322                 prev = &key->next;
323                 jlm = key->next;
324
325                 while (jlm && jlm->mod != mod) {
326                         prev = &jlm->next;
327                         jlm = jlm->next;
328                 }
329
330                 if (jlm) {
331                         *prev = jlm->next;
332                         kfree(jlm);
333                 }
334         }
335 }
336
337 static void jump_label_invalidate_module_init(struct module *mod)
338 {
339         struct jump_entry *iter_start = mod->jump_entries;
340         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
341         struct jump_entry *iter;
342
343         for (iter = iter_start; iter < iter_stop; iter++) {
344                 if (within_module_init(iter->code, mod))
345                         iter->code = 0;
346         }
347 }
348
349 static int
350 jump_label_module_notify(struct notifier_block *self, unsigned long val,
351                          void *data)
352 {
353         struct module *mod = data;
354         int ret = 0;
355
356         switch (val) {
357         case MODULE_STATE_COMING:
358                 jump_label_lock();
359                 ret = jump_label_add_module(mod);
360                 if (ret)
361                         jump_label_del_module(mod);
362                 jump_label_unlock();
363                 break;
364         case MODULE_STATE_GOING:
365                 jump_label_lock();
366                 jump_label_del_module(mod);
367                 jump_label_unlock();
368                 break;
369         case MODULE_STATE_LIVE:
370                 jump_label_lock();
371                 jump_label_invalidate_module_init(mod);
372                 jump_label_unlock();
373                 break;
374         }
375
376         return notifier_from_errno(ret);
377 }
378
379 struct notifier_block jump_label_module_nb = {
380         .notifier_call = jump_label_module_notify,
381         .priority = 1, /* higher than tracepoints */
382 };
383
384 static __init int jump_label_init_module(void)
385 {
386         return register_module_notifier(&jump_label_module_nb);
387 }
388 early_initcall(jump_label_init_module);
389
390 #endif /* CONFIG_MODULES */
391
392 /***
393  * jump_label_text_reserved - check if addr range is reserved
394  * @start: start text addr
395  * @end: end text addr
396  *
397  * checks if the text addr located between @start and @end
398  * overlaps with any of the jump label patch addresses. Code
399  * that wants to modify kernel text should first verify that
400  * it does not overlap with any of the jump label addresses.
401  * Caller must hold jump_label_mutex.
402  *
403  * returns 1 if there is an overlap, 0 otherwise
404  */
405 int jump_label_text_reserved(void *start, void *end)
406 {
407         int ret = __jump_label_text_reserved(__start___jump_table,
408                         __stop___jump_table, start, end);
409
410         if (ret)
411                 return ret;
412
413 #ifdef CONFIG_MODULES
414         ret = __jump_label_mod_text_reserved(start, end);
415 #endif
416         return ret;
417 }
418
419 static void jump_label_update(struct jump_label_key *key, int enable)
420 {
421         struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
422
423 #ifdef CONFIG_MODULES
424         struct module *mod = __module_address((jump_label_t)key);
425
426         __jump_label_mod_update(key, enable);
427
428         if (mod)
429                 stop = mod->jump_entries + mod->num_jump_entries;
430 #endif
431         /* if there are no users, entry can be NULL */
432         if (entry)
433                 __jump_label_update(key, entry, stop, enable);
434 }
435
436 #endif