jump-label: initialize jump-label subsystem much earlier
[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_add_return(1, &key->enabled) == 1)
70                 jump_label_update(key, JUMP_LABEL_ENABLE);
71         jump_label_unlock();
72 }
73
74 void jump_label_dec(struct jump_label_key *key)
75 {
76         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
77                 return;
78
79         jump_label_update(key, JUMP_LABEL_DISABLE);
80         jump_label_unlock();
81 }
82
83 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
84 {
85         if (entry->code <= (unsigned long)end &&
86                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
87                 return 1;
88
89         return 0;
90 }
91
92 static int __jump_label_text_reserved(struct jump_entry *iter_start,
93                 struct jump_entry *iter_stop, void *start, void *end)
94 {
95         struct jump_entry *iter;
96
97         iter = iter_start;
98         while (iter < iter_stop) {
99                 if (addr_conflict(iter, start, end))
100                         return 1;
101                 iter++;
102         }
103
104         return 0;
105 }
106
107 /* 
108  * Update code which is definitely not currently executing.
109  * Architectures which need heavyweight synchronization to modify
110  * running code can override this to make the non-live update case
111  * cheaper.
112  */
113 void __weak arch_jump_label_transform_static(struct jump_entry *entry,
114                                             enum jump_label_type type)
115 {
116         arch_jump_label_transform(entry, type); 
117 }
118
119 static void __jump_label_update(struct jump_label_key *key,
120                                 struct jump_entry *entry,
121                                 struct jump_entry *stop, int enable)
122 {
123         for (; (entry < stop) &&
124               (entry->key == (jump_label_t)(unsigned long)key);
125               entry++) {
126                 /*
127                  * entry->code set to 0 invalidates module init text sections
128                  * kernel_text_address() verifies we are not in core kernel
129                  * init code, see jump_label_invalidate_module_init().
130                  */
131                 if (entry->code && kernel_text_address(entry->code))
132                         arch_jump_label_transform(entry, enable);
133         }
134 }
135
136 void __init jump_label_init(void)
137 {
138         struct jump_entry *iter_start = __start___jump_table;
139         struct jump_entry *iter_stop = __stop___jump_table;
140         struct jump_label_key *key = NULL;
141         struct jump_entry *iter;
142
143         jump_label_lock();
144         jump_label_sort_entries(iter_start, iter_stop);
145
146         for (iter = iter_start; iter < iter_stop; iter++) {
147                 struct jump_label_key *iterk;
148
149                 iterk = (struct jump_label_key *)(unsigned long)iter->key;
150                 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
151                                                  JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
152                 if (iterk == key)
153                         continue;
154
155                 key = iterk;
156                 key->entries = iter;
157 #ifdef CONFIG_MODULES
158                 key->next = NULL;
159 #endif
160         }
161         jump_label_unlock();
162 }
163
164 #ifdef CONFIG_MODULES
165
166 struct jump_label_mod {
167         struct jump_label_mod *next;
168         struct jump_entry *entries;
169         struct module *mod;
170 };
171
172 static int __jump_label_mod_text_reserved(void *start, void *end)
173 {
174         struct module *mod;
175
176         mod = __module_text_address((unsigned long)start);
177         if (!mod)
178                 return 0;
179
180         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
181
182         return __jump_label_text_reserved(mod->jump_entries,
183                                 mod->jump_entries + mod->num_jump_entries,
184                                 start, end);
185 }
186
187 static void __jump_label_mod_update(struct jump_label_key *key, int enable)
188 {
189         struct jump_label_mod *mod = key->next;
190
191         while (mod) {
192                 struct module *m = mod->mod;
193
194                 __jump_label_update(key, mod->entries,
195                                     m->jump_entries + m->num_jump_entries,
196                                     enable);
197                 mod = mod->next;
198         }
199 }
200
201 /***
202  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
203  * @mod: module to patch
204  *
205  * Allow for run-time selection of the optimal nops. Before the module
206  * loads patch these with arch_get_jump_label_nop(), which is specified by
207  * the arch specific jump label code.
208  */
209 void jump_label_apply_nops(struct module *mod)
210 {
211         struct jump_entry *iter_start = mod->jump_entries;
212         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
213         struct jump_entry *iter;
214
215         /* if the module doesn't have jump label entries, just return */
216         if (iter_start == iter_stop)
217                 return;
218
219         for (iter = iter_start; iter < iter_stop; iter++)
220                 arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
221 }
222
223 static int jump_label_add_module(struct module *mod)
224 {
225         struct jump_entry *iter_start = mod->jump_entries;
226         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
227         struct jump_entry *iter;
228         struct jump_label_key *key = NULL;
229         struct jump_label_mod *jlm;
230
231         /* if the module doesn't have jump label entries, just return */
232         if (iter_start == iter_stop)
233                 return 0;
234
235         jump_label_sort_entries(iter_start, iter_stop);
236
237         for (iter = iter_start; iter < iter_stop; iter++) {
238                 if (iter->key == (jump_label_t)(unsigned long)key)
239                         continue;
240
241                 key = (struct jump_label_key *)(unsigned long)iter->key;
242
243                 if (__module_address(iter->key) == mod) {
244                         atomic_set(&key->enabled, 0);
245                         key->entries = iter;
246                         key->next = NULL;
247                         continue;
248                 }
249
250                 jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
251                 if (!jlm)
252                         return -ENOMEM;
253
254                 jlm->mod = mod;
255                 jlm->entries = iter;
256                 jlm->next = key->next;
257                 key->next = jlm;
258
259                 if (jump_label_enabled(key))
260                         __jump_label_update(key, iter, iter_stop,
261                                             JUMP_LABEL_ENABLE);
262         }
263
264         return 0;
265 }
266
267 static void jump_label_del_module(struct module *mod)
268 {
269         struct jump_entry *iter_start = mod->jump_entries;
270         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
271         struct jump_entry *iter;
272         struct jump_label_key *key = NULL;
273         struct jump_label_mod *jlm, **prev;
274
275         for (iter = iter_start; iter < iter_stop; iter++) {
276                 if (iter->key == (jump_label_t)(unsigned long)key)
277                         continue;
278
279                 key = (struct jump_label_key *)(unsigned long)iter->key;
280
281                 if (__module_address(iter->key) == mod)
282                         continue;
283
284                 prev = &key->next;
285                 jlm = key->next;
286
287                 while (jlm && jlm->mod != mod) {
288                         prev = &jlm->next;
289                         jlm = jlm->next;
290                 }
291
292                 if (jlm) {
293                         *prev = jlm->next;
294                         kfree(jlm);
295                 }
296         }
297 }
298
299 static void jump_label_invalidate_module_init(struct module *mod)
300 {
301         struct jump_entry *iter_start = mod->jump_entries;
302         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
303         struct jump_entry *iter;
304
305         for (iter = iter_start; iter < iter_stop; iter++) {
306                 if (within_module_init(iter->code, mod))
307                         iter->code = 0;
308         }
309 }
310
311 static int
312 jump_label_module_notify(struct notifier_block *self, unsigned long val,
313                          void *data)
314 {
315         struct module *mod = data;
316         int ret = 0;
317
318         switch (val) {
319         case MODULE_STATE_COMING:
320                 jump_label_lock();
321                 ret = jump_label_add_module(mod);
322                 if (ret)
323                         jump_label_del_module(mod);
324                 jump_label_unlock();
325                 break;
326         case MODULE_STATE_GOING:
327                 jump_label_lock();
328                 jump_label_del_module(mod);
329                 jump_label_unlock();
330                 break;
331         case MODULE_STATE_LIVE:
332                 jump_label_lock();
333                 jump_label_invalidate_module_init(mod);
334                 jump_label_unlock();
335                 break;
336         }
337
338         return notifier_from_errno(ret);
339 }
340
341 struct notifier_block jump_label_module_nb = {
342         .notifier_call = jump_label_module_notify,
343         .priority = 1, /* higher than tracepoints */
344 };
345
346 static __init int jump_label_init_module(void)
347 {
348         return register_module_notifier(&jump_label_module_nb);
349 }
350 early_initcall(jump_label_init_module);
351
352 #endif /* CONFIG_MODULES */
353
354 /***
355  * jump_label_text_reserved - check if addr range is reserved
356  * @start: start text addr
357  * @end: end text addr
358  *
359  * checks if the text addr located between @start and @end
360  * overlaps with any of the jump label patch addresses. Code
361  * that wants to modify kernel text should first verify that
362  * it does not overlap with any of the jump label addresses.
363  * Caller must hold jump_label_mutex.
364  *
365  * returns 1 if there is an overlap, 0 otherwise
366  */
367 int jump_label_text_reserved(void *start, void *end)
368 {
369         int ret = __jump_label_text_reserved(__start___jump_table,
370                         __stop___jump_table, start, end);
371
372         if (ret)
373                 return ret;
374
375 #ifdef CONFIG_MODULES
376         ret = __jump_label_mod_text_reserved(start, end);
377 #endif
378         return ret;
379 }
380
381 static void jump_label_update(struct jump_label_key *key, int enable)
382 {
383         struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
384
385 #ifdef CONFIG_MODULES
386         struct module *mod = __module_address((jump_label_t)key);
387
388         __jump_label_mod_update(key, enable);
389
390         if (mod)
391                 stop = mod->jump_entries + mod->num_jump_entries;
392 #endif
393         /* if there are no users, entry can be NULL */
394         if (entry)
395                 __jump_label_update(key, entry, stop, enable);
396 }
397
398 #endif