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