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