jump label: Base patch for jump label
[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 __init int init_jump_label(void)
181 {
182         int ret;
183         struct jump_entry *iter_start = __start___jump_table;
184         struct jump_entry *iter_stop = __stop___jump_table;
185         struct jump_entry *iter;
186
187         mutex_lock(&jump_label_mutex);
188         ret = build_jump_label_hashtable(__start___jump_table,
189                                          __stop___jump_table);
190         iter = iter_start;
191         while (iter < iter_stop) {
192                 arch_jump_label_text_poke_early(iter->code);
193                 iter++;
194         }
195         mutex_unlock(&jump_label_mutex);
196         return ret;
197 }
198 early_initcall(init_jump_label);
199
200 #ifdef CONFIG_MODULES
201
202 static struct jump_label_module_entry *
203 add_jump_label_module_entry(struct jump_label_entry *entry,
204                             struct jump_entry *iter_begin,
205                             int count, struct module *mod)
206 {
207         struct jump_label_module_entry *e;
208
209         e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
210         if (!e)
211                 return ERR_PTR(-ENOMEM);
212         e->mod = mod;
213         e->nr_entries = count;
214         e->table = iter_begin;
215         hlist_add_head(&e->hlist, &entry->modules);
216         return e;
217 }
218
219 static int add_jump_label_module(struct module *mod)
220 {
221         struct jump_entry *iter, *iter_begin;
222         struct jump_label_entry *entry;
223         struct jump_label_module_entry *module_entry;
224         int count;
225
226         /* if the module doesn't have jump label entries, just return */
227         if (!mod->num_jump_entries)
228                 return 0;
229
230         sort_jump_label_entries(mod->jump_entries,
231                                 mod->jump_entries + mod->num_jump_entries);
232         iter = mod->jump_entries;
233         while (iter < mod->jump_entries + mod->num_jump_entries) {
234                 entry = get_jump_label_entry(iter->key);
235                 iter_begin = iter;
236                 count = 0;
237                 while ((iter < mod->jump_entries + mod->num_jump_entries) &&
238                         (iter->key == iter_begin->key)) {
239                                 iter++;
240                                 count++;
241                 }
242                 if (!entry) {
243                         entry = add_jump_label_entry(iter_begin->key, 0, NULL);
244                         if (IS_ERR(entry))
245                                 return PTR_ERR(entry);
246                 }
247                 module_entry = add_jump_label_module_entry(entry, iter_begin,
248                                                            count, mod);
249                 if (IS_ERR(module_entry))
250                         return PTR_ERR(module_entry);
251         }
252         return 0;
253 }
254
255 static void remove_jump_label_module(struct module *mod)
256 {
257         struct hlist_head *head;
258         struct hlist_node *node, *node_next, *module_node, *module_node_next;
259         struct jump_label_entry *e;
260         struct jump_label_module_entry *e_module;
261         int i;
262
263         /* if the module doesn't have jump label entries, just return */
264         if (!mod->num_jump_entries)
265                 return;
266
267         for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
268                 head = &jump_label_table[i];
269                 hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
270                         hlist_for_each_entry_safe(e_module, module_node,
271                                                   module_node_next,
272                                                   &(e->modules), hlist) {
273                                 if (e_module->mod == mod) {
274                                         hlist_del(&e_module->hlist);
275                                         kfree(e_module);
276                                 }
277                         }
278                         if (hlist_empty(&e->modules) && (e->nr_entries == 0)) {
279                                 hlist_del(&e->hlist);
280                                 kfree(e);
281                         }
282                 }
283         }
284 }
285
286 static int
287 jump_label_module_notify(struct notifier_block *self, unsigned long val,
288                          void *data)
289 {
290         struct module *mod = data;
291         int ret = 0;
292
293         switch (val) {
294         case MODULE_STATE_COMING:
295                 mutex_lock(&jump_label_mutex);
296                 ret = add_jump_label_module(mod);
297                 if (ret)
298                         remove_jump_label_module(mod);
299                 mutex_unlock(&jump_label_mutex);
300                 break;
301         case MODULE_STATE_GOING:
302                 mutex_lock(&jump_label_mutex);
303                 remove_jump_label_module(mod);
304                 mutex_unlock(&jump_label_mutex);
305                 break;
306         }
307         return ret;
308 }
309
310 /***
311  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
312  * @mod: module to patch
313  *
314  * Allow for run-time selection of the optimal nops. Before the module
315  * loads patch these with arch_get_jump_label_nop(), which is specified by
316  * the arch specific jump label code.
317  */
318 void jump_label_apply_nops(struct module *mod)
319 {
320         struct jump_entry *iter;
321
322         /* if the module doesn't have jump label entries, just return */
323         if (!mod->num_jump_entries)
324                 return;
325
326         iter = mod->jump_entries;
327         while (iter < mod->jump_entries + mod->num_jump_entries) {
328                 arch_jump_label_text_poke_early(iter->code);
329                 iter++;
330         }
331 }
332
333 struct notifier_block jump_label_module_nb = {
334         .notifier_call = jump_label_module_notify,
335         .priority = 0,
336 };
337
338 static __init int init_jump_label_module(void)
339 {
340         return register_module_notifier(&jump_label_module_nb);
341 }
342 early_initcall(init_jump_label_module);
343
344 #endif /* CONFIG_MODULES */
345
346 #endif