jump label: Make arch_jump_label_text_poke_early() optional
[linux-2.6.git] / kernel / jump_label.c
1 /*
2  * jump label support
3  *
4  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5  *
6  */
7 #include <linux/jump_label.h>
8 #include <linux/memory.h>
9 #include <linux/uaccess.h>
10 #include <linux/module.h>
11 #include <linux/list.h>
12 #include <linux/jhash.h>
13 #include <linux/slab.h>
14 #include <linux/sort.h>
15 #include <linux/err.h>
16
17 #ifdef HAVE_JUMP_LABEL
18
19 #define JUMP_LABEL_HASH_BITS 6
20 #define JUMP_LABEL_TABLE_SIZE (1 << JUMP_LABEL_HASH_BITS)
21 static struct hlist_head jump_label_table[JUMP_LABEL_TABLE_SIZE];
22
23 /* mutex to protect coming/going of the the jump_label table */
24 static DEFINE_MUTEX(jump_label_mutex);
25
26 struct jump_label_entry {
27         struct hlist_node hlist;
28         struct jump_entry *table;
29         int nr_entries;
30         /* hang modules off here */
31         struct hlist_head modules;
32         unsigned long key;
33 };
34
35 struct jump_label_module_entry {
36         struct hlist_node hlist;
37         struct jump_entry *table;
38         int nr_entries;
39         struct module *mod;
40 };
41
42 void jump_label_lock(void)
43 {
44         mutex_lock(&jump_label_mutex);
45 }
46
47 void jump_label_unlock(void)
48 {
49         mutex_unlock(&jump_label_mutex);
50 }
51
52 static int jump_label_cmp(const void *a, const void *b)
53 {
54         const struct jump_entry *jea = a;
55         const struct jump_entry *jeb = b;
56
57         if (jea->key < jeb->key)
58                 return -1;
59
60         if (jea->key > jeb->key)
61                 return 1;
62
63         return 0;
64 }
65
66 static void
67 sort_jump_label_entries(struct jump_entry *start, struct jump_entry *stop)
68 {
69         unsigned long size;
70
71         size = (((unsigned long)stop - (unsigned long)start)
72                                         / sizeof(struct jump_entry));
73         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
74 }
75
76 static struct jump_label_entry *get_jump_label_entry(jump_label_t key)
77 {
78         struct hlist_head *head;
79         struct hlist_node *node;
80         struct jump_label_entry *e;
81         u32 hash = jhash((void *)&key, sizeof(jump_label_t), 0);
82
83         head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
84         hlist_for_each_entry(e, node, head, hlist) {
85                 if (key == e->key)
86                         return e;
87         }
88         return NULL;
89 }
90
91 static struct jump_label_entry *
92 add_jump_label_entry(jump_label_t key, int nr_entries, struct jump_entry *table)
93 {
94         struct hlist_head *head;
95         struct jump_label_entry *e;
96         u32 hash;
97
98         e = get_jump_label_entry(key);
99         if (e)
100                 return ERR_PTR(-EEXIST);
101
102         e = kmalloc(sizeof(struct jump_label_entry), GFP_KERNEL);
103         if (!e)
104                 return ERR_PTR(-ENOMEM);
105
106         hash = jhash((void *)&key, sizeof(jump_label_t), 0);
107         head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
108         e->key = key;
109         e->table = table;
110         e->nr_entries = nr_entries;
111         INIT_HLIST_HEAD(&(e->modules));
112         hlist_add_head(&e->hlist, head);
113         return e;
114 }
115
116 static int
117 build_jump_label_hashtable(struct jump_entry *start, struct jump_entry *stop)
118 {
119         struct jump_entry *iter, *iter_begin;
120         struct jump_label_entry *entry;
121         int count;
122
123         sort_jump_label_entries(start, stop);
124         iter = start;
125         while (iter < stop) {
126                 entry = get_jump_label_entry(iter->key);
127                 if (!entry) {
128                         iter_begin = iter;
129                         count = 0;
130                         while ((iter < stop) &&
131                                 (iter->key == iter_begin->key)) {
132                                 iter++;
133                                 count++;
134                         }
135                         entry = add_jump_label_entry(iter_begin->key,
136                                                         count, iter_begin);
137                         if (IS_ERR(entry))
138                                 return PTR_ERR(entry);
139                  } else {
140                         WARN_ONCE(1, KERN_ERR "build_jump_hashtable: unexpected entry!\n");
141                         return -1;
142                 }
143         }
144         return 0;
145 }
146
147 /***
148  * jump_label_update - update jump label text
149  * @key -  key value associated with a a jump label
150  * @type - enum set to JUMP_LABEL_ENABLE or JUMP_LABEL_DISABLE
151  *
152  * Will enable/disable the jump for jump label @key, depending on the
153  * value of @type.
154  *
155  */
156
157 void jump_label_update(unsigned long key, enum jump_label_type type)
158 {
159         struct jump_entry *iter;
160         struct jump_label_entry *entry;
161         struct hlist_node *module_node;
162         struct jump_label_module_entry *e_module;
163         int count;
164
165         jump_label_lock();
166         entry = get_jump_label_entry((jump_label_t)key);
167         if (entry) {
168                 count = entry->nr_entries;
169                 iter = entry->table;
170                 while (count--) {
171                         if (kernel_text_address(iter->code))
172                                 arch_jump_label_transform(iter, type);
173                         iter++;
174                 }
175                 /* eanble/disable jump labels in modules */
176                 hlist_for_each_entry(e_module, module_node, &(entry->modules),
177                                                         hlist) {
178                         count = e_module->nr_entries;
179                         iter = e_module->table;
180                         while (count--) {
181                                 if (iter->key &&
182                                                 kernel_text_address(iter->code))
183                                         arch_jump_label_transform(iter, type);
184                                 iter++;
185                         }
186                 }
187         }
188         jump_label_unlock();
189 }
190
191 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
192 {
193         if (entry->code <= (unsigned long)end &&
194                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
195                 return 1;
196
197         return 0;
198 }
199
200 #ifdef CONFIG_MODULES
201
202 static int module_conflict(void *start, void *end)
203 {
204         struct hlist_head *head;
205         struct hlist_node *node, *node_next, *module_node, *module_node_next;
206         struct jump_label_entry *e;
207         struct jump_label_module_entry *e_module;
208         struct jump_entry *iter;
209         int i, count;
210         int conflict = 0;
211
212         for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
213                 head = &jump_label_table[i];
214                 hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
215                         hlist_for_each_entry_safe(e_module, module_node,
216                                                         module_node_next,
217                                                         &(e->modules), hlist) {
218                                 count = e_module->nr_entries;
219                                 iter = e_module->table;
220                                 while (count--) {
221                                         if (addr_conflict(iter, start, end)) {
222                                                 conflict = 1;
223                                                 goto out;
224                                         }
225                                         iter++;
226                                 }
227                         }
228                 }
229         }
230 out:
231         return conflict;
232 }
233
234 #endif
235
236 /***
237  * jump_label_text_reserved - check if addr range is reserved
238  * @start: start text addr
239  * @end: end text addr
240  *
241  * checks if the text addr located between @start and @end
242  * overlaps with any of the jump label patch addresses. Code
243  * that wants to modify kernel text should first verify that
244  * it does not overlap with any of the jump label addresses.
245  * Caller must hold jump_label_mutex.
246  *
247  * returns 1 if there is an overlap, 0 otherwise
248  */
249 int jump_label_text_reserved(void *start, void *end)
250 {
251         struct jump_entry *iter;
252         struct jump_entry *iter_start = __start___jump_table;
253         struct jump_entry *iter_stop = __start___jump_table;
254         int conflict = 0;
255
256         iter = iter_start;
257         while (iter < iter_stop) {
258                 if (addr_conflict(iter, start, end)) {
259                         conflict = 1;
260                         goto out;
261                 }
262                 iter++;
263         }
264
265         /* now check modules */
266 #ifdef CONFIG_MODULES
267         conflict = module_conflict(start, end);
268 #endif
269 out:
270         return conflict;
271 }
272
273 /*
274  * Not all archs need this.
275  */
276 void __weak arch_jump_label_text_poke_early(jump_label_t addr)
277 {
278 }
279
280 static __init int init_jump_label(void)
281 {
282         int ret;
283         struct jump_entry *iter_start = __start___jump_table;
284         struct jump_entry *iter_stop = __stop___jump_table;
285         struct jump_entry *iter;
286
287         jump_label_lock();
288         ret = build_jump_label_hashtable(__start___jump_table,
289                                          __stop___jump_table);
290         iter = iter_start;
291         while (iter < iter_stop) {
292                 arch_jump_label_text_poke_early(iter->code);
293                 iter++;
294         }
295         jump_label_unlock();
296         return ret;
297 }
298 early_initcall(init_jump_label);
299
300 #ifdef CONFIG_MODULES
301
302 static struct jump_label_module_entry *
303 add_jump_label_module_entry(struct jump_label_entry *entry,
304                             struct jump_entry *iter_begin,
305                             int count, struct module *mod)
306 {
307         struct jump_label_module_entry *e;
308
309         e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
310         if (!e)
311                 return ERR_PTR(-ENOMEM);
312         e->mod = mod;
313         e->nr_entries = count;
314         e->table = iter_begin;
315         hlist_add_head(&e->hlist, &entry->modules);
316         return e;
317 }
318
319 static int add_jump_label_module(struct module *mod)
320 {
321         struct jump_entry *iter, *iter_begin;
322         struct jump_label_entry *entry;
323         struct jump_label_module_entry *module_entry;
324         int count;
325
326         /* if the module doesn't have jump label entries, just return */
327         if (!mod->num_jump_entries)
328                 return 0;
329
330         sort_jump_label_entries(mod->jump_entries,
331                                 mod->jump_entries + mod->num_jump_entries);
332         iter = mod->jump_entries;
333         while (iter < mod->jump_entries + mod->num_jump_entries) {
334                 entry = get_jump_label_entry(iter->key);
335                 iter_begin = iter;
336                 count = 0;
337                 while ((iter < mod->jump_entries + mod->num_jump_entries) &&
338                         (iter->key == iter_begin->key)) {
339                                 iter++;
340                                 count++;
341                 }
342                 if (!entry) {
343                         entry = add_jump_label_entry(iter_begin->key, 0, NULL);
344                         if (IS_ERR(entry))
345                                 return PTR_ERR(entry);
346                 }
347                 module_entry = add_jump_label_module_entry(entry, iter_begin,
348                                                            count, mod);
349                 if (IS_ERR(module_entry))
350                         return PTR_ERR(module_entry);
351         }
352         return 0;
353 }
354
355 static void remove_jump_label_module(struct module *mod)
356 {
357         struct hlist_head *head;
358         struct hlist_node *node, *node_next, *module_node, *module_node_next;
359         struct jump_label_entry *e;
360         struct jump_label_module_entry *e_module;
361         int i;
362
363         /* if the module doesn't have jump label entries, just return */
364         if (!mod->num_jump_entries)
365                 return;
366
367         for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
368                 head = &jump_label_table[i];
369                 hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
370                         hlist_for_each_entry_safe(e_module, module_node,
371                                                   module_node_next,
372                                                   &(e->modules), hlist) {
373                                 if (e_module->mod == mod) {
374                                         hlist_del(&e_module->hlist);
375                                         kfree(e_module);
376                                 }
377                         }
378                         if (hlist_empty(&e->modules) && (e->nr_entries == 0)) {
379                                 hlist_del(&e->hlist);
380                                 kfree(e);
381                         }
382                 }
383         }
384 }
385
386 static void remove_jump_label_module_init(struct module *mod)
387 {
388         struct hlist_head *head;
389         struct hlist_node *node, *node_next, *module_node, *module_node_next;
390         struct jump_label_entry *e;
391         struct jump_label_module_entry *e_module;
392         struct jump_entry *iter;
393         int i, count;
394
395         /* if the module doesn't have jump label entries, just return */
396         if (!mod->num_jump_entries)
397                 return;
398
399         for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
400                 head = &jump_label_table[i];
401                 hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
402                         hlist_for_each_entry_safe(e_module, module_node,
403                                                   module_node_next,
404                                                   &(e->modules), hlist) {
405                                 if (e_module->mod != mod)
406                                         continue;
407                                 count = e_module->nr_entries;
408                                 iter = e_module->table;
409                                 while (count--) {
410                                         if (within_module_init(iter->code, mod))
411                                                 iter->key = 0;
412                                         iter++;
413                                 }
414                         }
415                 }
416         }
417 }
418
419 static int
420 jump_label_module_notify(struct notifier_block *self, unsigned long val,
421                          void *data)
422 {
423         struct module *mod = data;
424         int ret = 0;
425
426         switch (val) {
427         case MODULE_STATE_COMING:
428                 jump_label_lock();
429                 ret = add_jump_label_module(mod);
430                 if (ret)
431                         remove_jump_label_module(mod);
432                 jump_label_unlock();
433                 break;
434         case MODULE_STATE_GOING:
435                 jump_label_lock();
436                 remove_jump_label_module(mod);
437                 jump_label_unlock();
438                 break;
439         case MODULE_STATE_LIVE:
440                 jump_label_lock();
441                 remove_jump_label_module_init(mod);
442                 jump_label_unlock();
443                 break;
444         }
445         return ret;
446 }
447
448 /***
449  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
450  * @mod: module to patch
451  *
452  * Allow for run-time selection of the optimal nops. Before the module
453  * loads patch these with arch_get_jump_label_nop(), which is specified by
454  * the arch specific jump label code.
455  */
456 void jump_label_apply_nops(struct module *mod)
457 {
458         struct jump_entry *iter;
459
460         /* if the module doesn't have jump label entries, just return */
461         if (!mod->num_jump_entries)
462                 return;
463
464         iter = mod->jump_entries;
465         while (iter < mod->jump_entries + mod->num_jump_entries) {
466                 arch_jump_label_text_poke_early(iter->code);
467                 iter++;
468         }
469 }
470
471 struct notifier_block jump_label_module_nb = {
472         .notifier_call = jump_label_module_notify,
473         .priority = 0,
474 };
475
476 static __init int init_jump_label_module(void)
477 {
478         return register_module_notifier(&jump_label_module_nb);
479 }
480 early_initcall(init_jump_label_module);
481
482 #endif /* CONFIG_MODULES */
483
484 #endif