Merge branch 'evm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/kasatkin...
[linux-2.6.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 void jump_label_dec(struct jump_label_key *key)
76 {
77         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
78                 return;
79
80         jump_label_update(key, JUMP_LABEL_DISABLE);
81         jump_label_unlock();
82 }
83
84 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
85 {
86         if (entry->code <= (unsigned long)end &&
87                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
88                 return 1;
89
90         return 0;
91 }
92
93 static int __jump_label_text_reserved(struct jump_entry *iter_start,
94                 struct jump_entry *iter_stop, void *start, void *end)
95 {
96         struct jump_entry *iter;
97
98         iter = iter_start;
99         while (iter < iter_stop) {
100                 if (addr_conflict(iter, start, end))
101                         return 1;
102                 iter++;
103         }
104
105         return 0;
106 }
107
108 /* 
109  * Update code which is definitely not currently executing.
110  * Architectures which need heavyweight synchronization to modify
111  * running code can override this to make the non-live update case
112  * cheaper.
113  */
114 void __weak arch_jump_label_transform_static(struct jump_entry *entry,
115                                             enum jump_label_type type)
116 {
117         arch_jump_label_transform(entry, type); 
118 }
119
120 static void __jump_label_update(struct jump_label_key *key,
121                                 struct jump_entry *entry,
122                                 struct jump_entry *stop, int enable)
123 {
124         for (; (entry < stop) &&
125               (entry->key == (jump_label_t)(unsigned long)key);
126               entry++) {
127                 /*
128                  * entry->code set to 0 invalidates module init text sections
129                  * kernel_text_address() verifies we are not in core kernel
130                  * init code, see jump_label_invalidate_module_init().
131                  */
132                 if (entry->code && kernel_text_address(entry->code))
133                         arch_jump_label_transform(entry, enable);
134         }
135 }
136
137 void __init jump_label_init(void)
138 {
139         struct jump_entry *iter_start = __start___jump_table;
140         struct jump_entry *iter_stop = __stop___jump_table;
141         struct jump_label_key *key = NULL;
142         struct jump_entry *iter;
143
144         jump_label_lock();
145         jump_label_sort_entries(iter_start, iter_stop);
146
147         for (iter = iter_start; iter < iter_stop; iter++) {
148                 struct jump_label_key *iterk;
149
150                 iterk = (struct jump_label_key *)(unsigned long)iter->key;
151                 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
152                                                  JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
153                 if (iterk == key)
154                         continue;
155
156                 key = iterk;
157                 key->entries = iter;
158 #ifdef CONFIG_MODULES
159                 key->next = NULL;
160 #endif
161         }
162         jump_label_unlock();
163 }
164
165 #ifdef CONFIG_MODULES
166
167 struct jump_label_mod {
168         struct jump_label_mod *next;
169         struct jump_entry *entries;
170         struct module *mod;
171 };
172
173 static int __jump_label_mod_text_reserved(void *start, void *end)
174 {
175         struct module *mod;
176
177         mod = __module_text_address((unsigned long)start);
178         if (!mod)
179                 return 0;
180
181         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
182
183         return __jump_label_text_reserved(mod->jump_entries,
184                                 mod->jump_entries + mod->num_jump_entries,
185                                 start, end);
186 }
187
188 static void __jump_label_mod_update(struct jump_label_key *key, int enable)
189 {
190         struct jump_label_mod *mod = key->next;
191
192         while (mod) {
193                 struct module *m = mod->mod;
194
195                 __jump_label_update(key, mod->entries,
196                                     m->jump_entries + m->num_jump_entries,
197                                     enable);
198                 mod = mod->next;
199         }
200 }
201
202 /***
203  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
204  * @mod: module to patch
205  *
206  * Allow for run-time selection of the optimal nops. Before the module
207  * loads patch these with arch_get_jump_label_nop(), which is specified by
208  * the arch specific jump label code.
209  */
210 void jump_label_apply_nops(struct module *mod)
211 {
212         struct jump_entry *iter_start = mod->jump_entries;
213         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
214         struct jump_entry *iter;
215
216         /* if the module doesn't have jump label entries, just return */
217         if (iter_start == iter_stop)
218                 return;
219
220         for (iter = iter_start; iter < iter_stop; iter++)
221                 arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
222 }
223
224 static int jump_label_add_module(struct module *mod)
225 {
226         struct jump_entry *iter_start = mod->jump_entries;
227         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
228         struct jump_entry *iter;
229         struct jump_label_key *key = NULL;
230         struct jump_label_mod *jlm;
231
232         /* if the module doesn't have jump label entries, just return */
233         if (iter_start == iter_stop)
234                 return 0;
235
236         jump_label_sort_entries(iter_start, iter_stop);
237
238         for (iter = iter_start; iter < iter_stop; iter++) {
239                 if (iter->key == (jump_label_t)(unsigned long)key)
240                         continue;
241
242                 key = (struct jump_label_key *)(unsigned long)iter->key;
243
244                 if (__module_address(iter->key) == mod) {
245                         atomic_set(&key->enabled, 0);
246                         key->entries = iter;
247                         key->next = NULL;
248                         continue;
249                 }
250
251                 jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
252                 if (!jlm)
253                         return -ENOMEM;
254
255                 jlm->mod = mod;
256                 jlm->entries = iter;
257                 jlm->next = key->next;
258                 key->next = jlm;
259
260                 if (jump_label_enabled(key))
261                         __jump_label_update(key, iter, iter_stop,
262                                             JUMP_LABEL_ENABLE);
263         }
264
265         return 0;
266 }
267
268 static void jump_label_del_module(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         struct jump_label_key *key = NULL;
274         struct jump_label_mod *jlm, **prev;
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                         continue;
284
285                 prev = &key->next;
286                 jlm = key->next;
287
288                 while (jlm && jlm->mod != mod) {
289                         prev = &jlm->next;
290                         jlm = jlm->next;
291                 }
292
293                 if (jlm) {
294                         *prev = jlm->next;
295                         kfree(jlm);
296                 }
297         }
298 }
299
300 static void jump_label_invalidate_module_init(struct module *mod)
301 {
302         struct jump_entry *iter_start = mod->jump_entries;
303         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
304         struct jump_entry *iter;
305
306         for (iter = iter_start; iter < iter_stop; iter++) {
307                 if (within_module_init(iter->code, mod))
308                         iter->code = 0;
309         }
310 }
311
312 static int
313 jump_label_module_notify(struct notifier_block *self, unsigned long val,
314                          void *data)
315 {
316         struct module *mod = data;
317         int ret = 0;
318
319         switch (val) {
320         case MODULE_STATE_COMING:
321                 jump_label_lock();
322                 ret = jump_label_add_module(mod);
323                 if (ret)
324                         jump_label_del_module(mod);
325                 jump_label_unlock();
326                 break;
327         case MODULE_STATE_GOING:
328                 jump_label_lock();
329                 jump_label_del_module(mod);
330                 jump_label_unlock();
331                 break;
332         case MODULE_STATE_LIVE:
333                 jump_label_lock();
334                 jump_label_invalidate_module_init(mod);
335                 jump_label_unlock();
336                 break;
337         }
338
339         return notifier_from_errno(ret);
340 }
341
342 struct notifier_block jump_label_module_nb = {
343         .notifier_call = jump_label_module_notify,
344         .priority = 1, /* higher than tracepoints */
345 };
346
347 static __init int jump_label_init_module(void)
348 {
349         return register_module_notifier(&jump_label_module_nb);
350 }
351 early_initcall(jump_label_init_module);
352
353 #endif /* CONFIG_MODULES */
354
355 /***
356  * jump_label_text_reserved - check if addr range is reserved
357  * @start: start text addr
358  * @end: end text addr
359  *
360  * checks if the text addr located between @start and @end
361  * overlaps with any of the jump label patch addresses. Code
362  * that wants to modify kernel text should first verify that
363  * it does not overlap with any of the jump label addresses.
364  * Caller must hold jump_label_mutex.
365  *
366  * returns 1 if there is an overlap, 0 otherwise
367  */
368 int jump_label_text_reserved(void *start, void *end)
369 {
370         int ret = __jump_label_text_reserved(__start___jump_table,
371                         __stop___jump_table, start, end);
372
373         if (ret)
374                 return ret;
375
376 #ifdef CONFIG_MODULES
377         ret = __jump_label_mod_text_reserved(start, end);
378 #endif
379         return ret;
380 }
381
382 static void jump_label_update(struct jump_label_key *key, int enable)
383 {
384         struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
385
386 #ifdef CONFIG_MODULES
387         struct module *mod = __module_address((jump_label_t)key);
388
389         __jump_label_mod_update(key, enable);
390
391         if (mod)
392                 stop = mod->jump_entries + mod->num_jump_entries;
393 #endif
394         /* if there are no users, entry can be NULL */
395         if (entry)
396                 __jump_label_update(key, entry, stop, enable);
397 }
398
399 #endif