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bf5438fc JB |
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 | ||
91bad2f8 JB |
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 | ||
bf5438fc JB |
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 | ||
91bad2f8 | 165 | jump_label_lock(); |
bf5438fc JB |
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--) { | |
b842f8fa JB |
181 | if (iter->key && |
182 | kernel_text_address(iter->code)) | |
bf5438fc JB |
183 | arch_jump_label_transform(iter, type); |
184 | iter++; | |
185 | } | |
186 | } | |
187 | } | |
91bad2f8 | 188 | jump_label_unlock(); |
bf5438fc JB |
189 | } |
190 | ||
4c3ef6d7 JB |
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. | |
91bad2f8 | 245 | * Caller must hold jump_label_mutex. |
4c3ef6d7 JB |
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 | ||
4c3ef6d7 JB |
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: | |
4c3ef6d7 JB |
270 | return conflict; |
271 | } | |
272 | ||
bf5438fc JB |
273 | static __init int init_jump_label(void) |
274 | { | |
275 | int ret; | |
276 | struct jump_entry *iter_start = __start___jump_table; | |
277 | struct jump_entry *iter_stop = __stop___jump_table; | |
278 | struct jump_entry *iter; | |
279 | ||
91bad2f8 | 280 | jump_label_lock(); |
bf5438fc JB |
281 | ret = build_jump_label_hashtable(__start___jump_table, |
282 | __stop___jump_table); | |
283 | iter = iter_start; | |
284 | while (iter < iter_stop) { | |
285 | arch_jump_label_text_poke_early(iter->code); | |
286 | iter++; | |
287 | } | |
91bad2f8 | 288 | jump_label_unlock(); |
bf5438fc JB |
289 | return ret; |
290 | } | |
291 | early_initcall(init_jump_label); | |
292 | ||
293 | #ifdef CONFIG_MODULES | |
294 | ||
295 | static struct jump_label_module_entry * | |
296 | add_jump_label_module_entry(struct jump_label_entry *entry, | |
297 | struct jump_entry *iter_begin, | |
298 | int count, struct module *mod) | |
299 | { | |
300 | struct jump_label_module_entry *e; | |
301 | ||
302 | e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL); | |
303 | if (!e) | |
304 | return ERR_PTR(-ENOMEM); | |
305 | e->mod = mod; | |
306 | e->nr_entries = count; | |
307 | e->table = iter_begin; | |
308 | hlist_add_head(&e->hlist, &entry->modules); | |
309 | return e; | |
310 | } | |
311 | ||
312 | static int add_jump_label_module(struct module *mod) | |
313 | { | |
314 | struct jump_entry *iter, *iter_begin; | |
315 | struct jump_label_entry *entry; | |
316 | struct jump_label_module_entry *module_entry; | |
317 | int count; | |
318 | ||
319 | /* if the module doesn't have jump label entries, just return */ | |
320 | if (!mod->num_jump_entries) | |
321 | return 0; | |
322 | ||
323 | sort_jump_label_entries(mod->jump_entries, | |
324 | mod->jump_entries + mod->num_jump_entries); | |
325 | iter = mod->jump_entries; | |
326 | while (iter < mod->jump_entries + mod->num_jump_entries) { | |
327 | entry = get_jump_label_entry(iter->key); | |
328 | iter_begin = iter; | |
329 | count = 0; | |
330 | while ((iter < mod->jump_entries + mod->num_jump_entries) && | |
331 | (iter->key == iter_begin->key)) { | |
332 | iter++; | |
333 | count++; | |
334 | } | |
335 | if (!entry) { | |
336 | entry = add_jump_label_entry(iter_begin->key, 0, NULL); | |
337 | if (IS_ERR(entry)) | |
338 | return PTR_ERR(entry); | |
339 | } | |
340 | module_entry = add_jump_label_module_entry(entry, iter_begin, | |
341 | count, mod); | |
342 | if (IS_ERR(module_entry)) | |
343 | return PTR_ERR(module_entry); | |
344 | } | |
345 | return 0; | |
346 | } | |
347 | ||
348 | static void remove_jump_label_module(struct module *mod) | |
349 | { | |
350 | struct hlist_head *head; | |
351 | struct hlist_node *node, *node_next, *module_node, *module_node_next; | |
352 | struct jump_label_entry *e; | |
353 | struct jump_label_module_entry *e_module; | |
354 | int i; | |
355 | ||
356 | /* if the module doesn't have jump label entries, just return */ | |
357 | if (!mod->num_jump_entries) | |
358 | return; | |
359 | ||
360 | for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) { | |
361 | head = &jump_label_table[i]; | |
362 | hlist_for_each_entry_safe(e, node, node_next, head, hlist) { | |
363 | hlist_for_each_entry_safe(e_module, module_node, | |
364 | module_node_next, | |
365 | &(e->modules), hlist) { | |
366 | if (e_module->mod == mod) { | |
367 | hlist_del(&e_module->hlist); | |
368 | kfree(e_module); | |
369 | } | |
370 | } | |
371 | if (hlist_empty(&e->modules) && (e->nr_entries == 0)) { | |
372 | hlist_del(&e->hlist); | |
373 | kfree(e); | |
374 | } | |
375 | } | |
376 | } | |
377 | } | |
378 | ||
b842f8fa JB |
379 | static void remove_jump_label_module_init(struct module *mod) |
380 | { | |
381 | struct hlist_head *head; | |
382 | struct hlist_node *node, *node_next, *module_node, *module_node_next; | |
383 | struct jump_label_entry *e; | |
384 | struct jump_label_module_entry *e_module; | |
385 | struct jump_entry *iter; | |
386 | int i, count; | |
387 | ||
388 | /* if the module doesn't have jump label entries, just return */ | |
389 | if (!mod->num_jump_entries) | |
390 | return; | |
391 | ||
392 | for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) { | |
393 | head = &jump_label_table[i]; | |
394 | hlist_for_each_entry_safe(e, node, node_next, head, hlist) { | |
395 | hlist_for_each_entry_safe(e_module, module_node, | |
396 | module_node_next, | |
397 | &(e->modules), hlist) { | |
398 | if (e_module->mod != mod) | |
399 | continue; | |
400 | count = e_module->nr_entries; | |
401 | iter = e_module->table; | |
402 | while (count--) { | |
403 | if (within_module_init(iter->code, mod)) | |
404 | iter->key = 0; | |
405 | iter++; | |
406 | } | |
407 | } | |
408 | } | |
409 | } | |
410 | } | |
411 | ||
bf5438fc JB |
412 | static int |
413 | jump_label_module_notify(struct notifier_block *self, unsigned long val, | |
414 | void *data) | |
415 | { | |
416 | struct module *mod = data; | |
417 | int ret = 0; | |
418 | ||
419 | switch (val) { | |
420 | case MODULE_STATE_COMING: | |
91bad2f8 | 421 | jump_label_lock(); |
bf5438fc JB |
422 | ret = add_jump_label_module(mod); |
423 | if (ret) | |
424 | remove_jump_label_module(mod); | |
91bad2f8 | 425 | jump_label_unlock(); |
bf5438fc JB |
426 | break; |
427 | case MODULE_STATE_GOING: | |
91bad2f8 | 428 | jump_label_lock(); |
bf5438fc | 429 | remove_jump_label_module(mod); |
91bad2f8 | 430 | jump_label_unlock(); |
bf5438fc | 431 | break; |
b842f8fa | 432 | case MODULE_STATE_LIVE: |
91bad2f8 | 433 | jump_label_lock(); |
b842f8fa | 434 | remove_jump_label_module_init(mod); |
91bad2f8 | 435 | jump_label_unlock(); |
b842f8fa | 436 | break; |
bf5438fc JB |
437 | } |
438 | return ret; | |
439 | } | |
440 | ||
441 | /*** | |
442 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() | |
443 | * @mod: module to patch | |
444 | * | |
445 | * Allow for run-time selection of the optimal nops. Before the module | |
446 | * loads patch these with arch_get_jump_label_nop(), which is specified by | |
447 | * the arch specific jump label code. | |
448 | */ | |
449 | void jump_label_apply_nops(struct module *mod) | |
450 | { | |
451 | struct jump_entry *iter; | |
452 | ||
453 | /* if the module doesn't have jump label entries, just return */ | |
454 | if (!mod->num_jump_entries) | |
455 | return; | |
456 | ||
457 | iter = mod->jump_entries; | |
458 | while (iter < mod->jump_entries + mod->num_jump_entries) { | |
459 | arch_jump_label_text_poke_early(iter->code); | |
460 | iter++; | |
461 | } | |
462 | } | |
463 | ||
464 | struct notifier_block jump_label_module_nb = { | |
465 | .notifier_call = jump_label_module_notify, | |
466 | .priority = 0, | |
467 | }; | |
468 | ||
469 | static __init int init_jump_label_module(void) | |
470 | { | |
471 | return register_module_notifier(&jump_label_module_nb); | |
472 | } | |
473 | early_initcall(init_jump_label_module); | |
474 | ||
475 | #endif /* CONFIG_MODULES */ | |
476 | ||
477 | #endif |