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bf5438fc JB |
1 | /* |
2 | * jump label support | |
3 | * | |
4 | * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> | |
d430d3d7 | 5 | * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com> |
bf5438fc JB |
6 | * |
7 | */ | |
bf5438fc JB |
8 | #include <linux/memory.h> |
9 | #include <linux/uaccess.h> | |
10 | #include <linux/module.h> | |
11 | #include <linux/list.h> | |
bf5438fc JB |
12 | #include <linux/slab.h> |
13 | #include <linux/sort.h> | |
14 | #include <linux/err.h> | |
d430d3d7 | 15 | #include <linux/jump_label.h> |
bf5438fc JB |
16 | |
17 | #ifdef HAVE_JUMP_LABEL | |
18 | ||
bf5438fc JB |
19 | /* mutex to protect coming/going of the the jump_label table */ |
20 | static DEFINE_MUTEX(jump_label_mutex); | |
21 | ||
91bad2f8 JB |
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 | ||
d430d3d7 JB |
32 | bool jump_label_enabled(struct jump_label_key *key) |
33 | { | |
34 | return !!atomic_read(&key->enabled); | |
35 | } | |
36 | ||
bf5438fc JB |
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 | |
d430d3d7 | 52 | jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) |
bf5438fc JB |
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 | ||
d430d3d7 | 61 | static void jump_label_update(struct jump_label_key *key, int enable); |
bf5438fc | 62 | |
d430d3d7 | 63 | void jump_label_inc(struct jump_label_key *key) |
bf5438fc | 64 | { |
d430d3d7 JB |
65 | if (atomic_inc_not_zero(&key->enabled)) |
66 | return; | |
bf5438fc | 67 | |
d430d3d7 | 68 | jump_label_lock(); |
c8452afb | 69 | if (atomic_read(&key->enabled) == 0) |
d430d3d7 | 70 | jump_label_update(key, JUMP_LABEL_ENABLE); |
c8452afb | 71 | atomic_inc(&key->enabled); |
d430d3d7 | 72 | jump_label_unlock(); |
bf5438fc JB |
73 | } |
74 | ||
b2029520 GN |
75 | static void __jump_label_dec(struct jump_label_key *key, |
76 | unsigned long rate_limit, struct delayed_work *work) | |
bf5438fc | 77 | { |
d430d3d7 JB |
78 | if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) |
79 | return; | |
bf5438fc | 80 | |
b2029520 GN |
81 | if (rate_limit) { |
82 | atomic_inc(&key->enabled); | |
83 | schedule_delayed_work(work, rate_limit); | |
84 | } else | |
85 | jump_label_update(key, JUMP_LABEL_DISABLE); | |
86 | ||
91bad2f8 | 87 | jump_label_unlock(); |
bf5438fc JB |
88 | } |
89 | ||
b2029520 GN |
90 | static void jump_label_update_timeout(struct work_struct *work) |
91 | { | |
92 | struct jump_label_key_deferred *key = | |
93 | container_of(work, struct jump_label_key_deferred, work.work); | |
94 | __jump_label_dec(&key->key, 0, NULL); | |
95 | } | |
96 | ||
97 | void jump_label_dec(struct jump_label_key *key) | |
98 | { | |
99 | __jump_label_dec(key, 0, NULL); | |
100 | } | |
101 | ||
102 | void jump_label_dec_deferred(struct jump_label_key_deferred *key) | |
103 | { | |
104 | __jump_label_dec(&key->key, key->timeout, &key->work); | |
105 | } | |
106 | ||
107 | ||
108 | void jump_label_rate_limit(struct jump_label_key_deferred *key, | |
109 | unsigned long rl) | |
110 | { | |
111 | key->timeout = rl; | |
112 | INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); | |
113 | } | |
114 | ||
4c3ef6d7 JB |
115 | static int addr_conflict(struct jump_entry *entry, void *start, void *end) |
116 | { | |
117 | if (entry->code <= (unsigned long)end && | |
118 | entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start) | |
119 | return 1; | |
120 | ||
121 | return 0; | |
122 | } | |
123 | ||
d430d3d7 JB |
124 | static int __jump_label_text_reserved(struct jump_entry *iter_start, |
125 | struct jump_entry *iter_stop, void *start, void *end) | |
4c3ef6d7 | 126 | { |
4c3ef6d7 | 127 | struct jump_entry *iter; |
4c3ef6d7 | 128 | |
4c3ef6d7 JB |
129 | iter = iter_start; |
130 | while (iter < iter_stop) { | |
d430d3d7 JB |
131 | if (addr_conflict(iter, start, end)) |
132 | return 1; | |
4c3ef6d7 JB |
133 | iter++; |
134 | } | |
135 | ||
d430d3d7 JB |
136 | return 0; |
137 | } | |
138 | ||
20284aa7 JF |
139 | /* |
140 | * Update code which is definitely not currently executing. | |
141 | * Architectures which need heavyweight synchronization to modify | |
142 | * running code can override this to make the non-live update case | |
143 | * cheaper. | |
144 | */ | |
145 | void __weak arch_jump_label_transform_static(struct jump_entry *entry, | |
146 | enum jump_label_type type) | |
147 | { | |
148 | arch_jump_label_transform(entry, type); | |
149 | } | |
150 | ||
d430d3d7 | 151 | static void __jump_label_update(struct jump_label_key *key, |
7cbc5b8d JO |
152 | struct jump_entry *entry, |
153 | struct jump_entry *stop, int enable) | |
d430d3d7 | 154 | { |
7cbc5b8d JO |
155 | for (; (entry < stop) && |
156 | (entry->key == (jump_label_t)(unsigned long)key); | |
157 | entry++) { | |
d430d3d7 JB |
158 | /* |
159 | * entry->code set to 0 invalidates module init text sections | |
160 | * kernel_text_address() verifies we are not in core kernel | |
161 | * init code, see jump_label_invalidate_module_init(). | |
162 | */ | |
163 | if (entry->code && kernel_text_address(entry->code)) | |
164 | arch_jump_label_transform(entry, enable); | |
165 | } | |
4c3ef6d7 JB |
166 | } |
167 | ||
97ce2c88 | 168 | void __init jump_label_init(void) |
bf5438fc | 169 | { |
bf5438fc JB |
170 | struct jump_entry *iter_start = __start___jump_table; |
171 | struct jump_entry *iter_stop = __stop___jump_table; | |
d430d3d7 | 172 | struct jump_label_key *key = NULL; |
bf5438fc JB |
173 | struct jump_entry *iter; |
174 | ||
91bad2f8 | 175 | jump_label_lock(); |
d430d3d7 JB |
176 | jump_label_sort_entries(iter_start, iter_stop); |
177 | ||
178 | for (iter = iter_start; iter < iter_stop; iter++) { | |
37348804 JF |
179 | struct jump_label_key *iterk; |
180 | ||
181 | iterk = (struct jump_label_key *)(unsigned long)iter->key; | |
20284aa7 JF |
182 | arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ? |
183 | JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE); | |
37348804 | 184 | if (iterk == key) |
d430d3d7 JB |
185 | continue; |
186 | ||
37348804 | 187 | key = iterk; |
d430d3d7 JB |
188 | key->entries = iter; |
189 | #ifdef CONFIG_MODULES | |
190 | key->next = NULL; | |
191 | #endif | |
bf5438fc | 192 | } |
91bad2f8 | 193 | jump_label_unlock(); |
bf5438fc | 194 | } |
bf5438fc JB |
195 | |
196 | #ifdef CONFIG_MODULES | |
197 | ||
d430d3d7 JB |
198 | struct jump_label_mod { |
199 | struct jump_label_mod *next; | |
200 | struct jump_entry *entries; | |
201 | struct module *mod; | |
202 | }; | |
203 | ||
204 | static int __jump_label_mod_text_reserved(void *start, void *end) | |
205 | { | |
206 | struct module *mod; | |
207 | ||
208 | mod = __module_text_address((unsigned long)start); | |
209 | if (!mod) | |
210 | return 0; | |
211 | ||
212 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); | |
213 | ||
214 | return __jump_label_text_reserved(mod->jump_entries, | |
215 | mod->jump_entries + mod->num_jump_entries, | |
216 | start, end); | |
217 | } | |
218 | ||
219 | static void __jump_label_mod_update(struct jump_label_key *key, int enable) | |
220 | { | |
221 | struct jump_label_mod *mod = key->next; | |
222 | ||
223 | while (mod) { | |
7cbc5b8d JO |
224 | struct module *m = mod->mod; |
225 | ||
226 | __jump_label_update(key, mod->entries, | |
227 | m->jump_entries + m->num_jump_entries, | |
228 | enable); | |
d430d3d7 JB |
229 | mod = mod->next; |
230 | } | |
231 | } | |
232 | ||
233 | /*** | |
234 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() | |
235 | * @mod: module to patch | |
236 | * | |
237 | * Allow for run-time selection of the optimal nops. Before the module | |
238 | * loads patch these with arch_get_jump_label_nop(), which is specified by | |
239 | * the arch specific jump label code. | |
240 | */ | |
241 | void jump_label_apply_nops(struct module *mod) | |
bf5438fc | 242 | { |
d430d3d7 JB |
243 | struct jump_entry *iter_start = mod->jump_entries; |
244 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
245 | struct jump_entry *iter; | |
246 | ||
247 | /* if the module doesn't have jump label entries, just return */ | |
248 | if (iter_start == iter_stop) | |
249 | return; | |
250 | ||
251 | for (iter = iter_start; iter < iter_stop; iter++) | |
20284aa7 | 252 | arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE); |
bf5438fc JB |
253 | } |
254 | ||
d430d3d7 | 255 | static int jump_label_add_module(struct module *mod) |
bf5438fc | 256 | { |
d430d3d7 JB |
257 | struct jump_entry *iter_start = mod->jump_entries; |
258 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
259 | struct jump_entry *iter; | |
260 | struct jump_label_key *key = NULL; | |
261 | struct jump_label_mod *jlm; | |
bf5438fc JB |
262 | |
263 | /* if the module doesn't have jump label entries, just return */ | |
d430d3d7 | 264 | if (iter_start == iter_stop) |
bf5438fc JB |
265 | return 0; |
266 | ||
d430d3d7 JB |
267 | jump_label_sort_entries(iter_start, iter_stop); |
268 | ||
269 | for (iter = iter_start; iter < iter_stop; iter++) { | |
270 | if (iter->key == (jump_label_t)(unsigned long)key) | |
271 | continue; | |
272 | ||
273 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
274 | ||
275 | if (__module_address(iter->key) == mod) { | |
276 | atomic_set(&key->enabled, 0); | |
277 | key->entries = iter; | |
278 | key->next = NULL; | |
279 | continue; | |
bf5438fc | 280 | } |
d430d3d7 JB |
281 | |
282 | jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL); | |
283 | if (!jlm) | |
284 | return -ENOMEM; | |
285 | ||
286 | jlm->mod = mod; | |
287 | jlm->entries = iter; | |
288 | jlm->next = key->next; | |
289 | key->next = jlm; | |
290 | ||
291 | if (jump_label_enabled(key)) | |
7cbc5b8d JO |
292 | __jump_label_update(key, iter, iter_stop, |
293 | JUMP_LABEL_ENABLE); | |
bf5438fc | 294 | } |
d430d3d7 | 295 | |
bf5438fc JB |
296 | return 0; |
297 | } | |
298 | ||
d430d3d7 | 299 | static void jump_label_del_module(struct module *mod) |
bf5438fc | 300 | { |
d430d3d7 JB |
301 | struct jump_entry *iter_start = mod->jump_entries; |
302 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
303 | struct jump_entry *iter; | |
304 | struct jump_label_key *key = NULL; | |
305 | struct jump_label_mod *jlm, **prev; | |
bf5438fc | 306 | |
d430d3d7 JB |
307 | for (iter = iter_start; iter < iter_stop; iter++) { |
308 | if (iter->key == (jump_label_t)(unsigned long)key) | |
309 | continue; | |
310 | ||
311 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
312 | ||
313 | if (__module_address(iter->key) == mod) | |
314 | continue; | |
315 | ||
316 | prev = &key->next; | |
317 | jlm = key->next; | |
bf5438fc | 318 | |
d430d3d7 JB |
319 | while (jlm && jlm->mod != mod) { |
320 | prev = &jlm->next; | |
321 | jlm = jlm->next; | |
322 | } | |
323 | ||
324 | if (jlm) { | |
325 | *prev = jlm->next; | |
326 | kfree(jlm); | |
bf5438fc JB |
327 | } |
328 | } | |
329 | } | |
330 | ||
d430d3d7 | 331 | static void jump_label_invalidate_module_init(struct module *mod) |
b842f8fa | 332 | { |
d430d3d7 JB |
333 | struct jump_entry *iter_start = mod->jump_entries; |
334 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
b842f8fa | 335 | struct jump_entry *iter; |
b842f8fa | 336 | |
d430d3d7 JB |
337 | for (iter = iter_start; iter < iter_stop; iter++) { |
338 | if (within_module_init(iter->code, mod)) | |
339 | iter->code = 0; | |
b842f8fa JB |
340 | } |
341 | } | |
342 | ||
bf5438fc JB |
343 | static int |
344 | jump_label_module_notify(struct notifier_block *self, unsigned long val, | |
345 | void *data) | |
346 | { | |
347 | struct module *mod = data; | |
348 | int ret = 0; | |
349 | ||
350 | switch (val) { | |
351 | case MODULE_STATE_COMING: | |
91bad2f8 | 352 | jump_label_lock(); |
d430d3d7 | 353 | ret = jump_label_add_module(mod); |
bf5438fc | 354 | if (ret) |
d430d3d7 | 355 | jump_label_del_module(mod); |
91bad2f8 | 356 | jump_label_unlock(); |
bf5438fc JB |
357 | break; |
358 | case MODULE_STATE_GOING: | |
91bad2f8 | 359 | jump_label_lock(); |
d430d3d7 | 360 | jump_label_del_module(mod); |
91bad2f8 | 361 | jump_label_unlock(); |
bf5438fc | 362 | break; |
b842f8fa | 363 | case MODULE_STATE_LIVE: |
91bad2f8 | 364 | jump_label_lock(); |
d430d3d7 | 365 | jump_label_invalidate_module_init(mod); |
91bad2f8 | 366 | jump_label_unlock(); |
b842f8fa | 367 | break; |
bf5438fc | 368 | } |
bf5438fc | 369 | |
d430d3d7 | 370 | return notifier_from_errno(ret); |
bf5438fc JB |
371 | } |
372 | ||
373 | struct notifier_block jump_label_module_nb = { | |
374 | .notifier_call = jump_label_module_notify, | |
d430d3d7 | 375 | .priority = 1, /* higher than tracepoints */ |
bf5438fc JB |
376 | }; |
377 | ||
d430d3d7 | 378 | static __init int jump_label_init_module(void) |
bf5438fc JB |
379 | { |
380 | return register_module_notifier(&jump_label_module_nb); | |
381 | } | |
d430d3d7 | 382 | early_initcall(jump_label_init_module); |
bf5438fc JB |
383 | |
384 | #endif /* CONFIG_MODULES */ | |
385 | ||
d430d3d7 JB |
386 | /*** |
387 | * jump_label_text_reserved - check if addr range is reserved | |
388 | * @start: start text addr | |
389 | * @end: end text addr | |
390 | * | |
391 | * checks if the text addr located between @start and @end | |
392 | * overlaps with any of the jump label patch addresses. Code | |
393 | * that wants to modify kernel text should first verify that | |
394 | * it does not overlap with any of the jump label addresses. | |
395 | * Caller must hold jump_label_mutex. | |
396 | * | |
397 | * returns 1 if there is an overlap, 0 otherwise | |
398 | */ | |
399 | int jump_label_text_reserved(void *start, void *end) | |
400 | { | |
401 | int ret = __jump_label_text_reserved(__start___jump_table, | |
402 | __stop___jump_table, start, end); | |
403 | ||
404 | if (ret) | |
405 | return ret; | |
406 | ||
407 | #ifdef CONFIG_MODULES | |
408 | ret = __jump_label_mod_text_reserved(start, end); | |
409 | #endif | |
410 | return ret; | |
411 | } | |
412 | ||
413 | static void jump_label_update(struct jump_label_key *key, int enable) | |
414 | { | |
140fe3b1 | 415 | struct jump_entry *entry = key->entries, *stop = __stop___jump_table; |
d430d3d7 JB |
416 | |
417 | #ifdef CONFIG_MODULES | |
140fe3b1 XG |
418 | struct module *mod = __module_address((jump_label_t)key); |
419 | ||
d430d3d7 | 420 | __jump_label_mod_update(key, enable); |
140fe3b1 XG |
421 | |
422 | if (mod) | |
423 | stop = mod->jump_entries + mod->num_jump_entries; | |
d430d3d7 | 424 | #endif |
140fe3b1 XG |
425 | /* if there are no users, entry can be NULL */ |
426 | if (entry) | |
427 | __jump_label_update(key, entry, stop, enable); | |
d430d3d7 JB |
428 | } |
429 | ||
bf5438fc | 430 | #endif |