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1 | /* | |
2 | * jump label support | |
3 | * | |
4 | * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> | |
5 | * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com> | |
6 | * | |
7 | */ | |
8 | #include <linux/memory.h> | |
9 | #include <linux/uaccess.h> | |
10 | #include <linux/module.h> | |
11 | #include <linux/list.h> | |
12 | #include <linux/slab.h> | |
13 | #include <linux/sort.h> | |
14 | #include <linux/err.h> | |
15 | #include <linux/static_key.h> | |
16 | #include <linux/jump_label_ratelimit.h> | |
17 | ||
18 | #ifdef HAVE_JUMP_LABEL | |
19 | ||
20 | /* mutex to protect coming/going of the the jump_label table */ | |
21 | static DEFINE_MUTEX(jump_label_mutex); | |
22 | ||
23 | void jump_label_lock(void) | |
24 | { | |
25 | mutex_lock(&jump_label_mutex); | |
26 | } | |
27 | ||
28 | void jump_label_unlock(void) | |
29 | { | |
30 | mutex_unlock(&jump_label_mutex); | |
31 | } | |
32 | ||
33 | static int jump_label_cmp(const void *a, const void *b) | |
34 | { | |
35 | const struct jump_entry *jea = a; | |
36 | const struct jump_entry *jeb = b; | |
37 | ||
38 | if (jea->key < jeb->key) | |
39 | return -1; | |
40 | ||
41 | if (jea->key > jeb->key) | |
42 | return 1; | |
43 | ||
44 | return 0; | |
45 | } | |
46 | ||
47 | static void | |
48 | jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) | |
49 | { | |
50 | unsigned long size; | |
51 | ||
52 | size = (((unsigned long)stop - (unsigned long)start) | |
53 | / sizeof(struct jump_entry)); | |
54 | sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL); | |
55 | } | |
56 | ||
57 | static void jump_label_update(struct static_key *key, int enable); | |
58 | ||
59 | void static_key_slow_inc(struct static_key *key) | |
60 | { | |
61 | STATIC_KEY_CHECK_USE(); | |
62 | if (atomic_inc_not_zero(&key->enabled)) | |
63 | return; | |
64 | ||
65 | jump_label_lock(); | |
66 | if (atomic_read(&key->enabled) == 0) { | |
67 | if (!jump_label_get_branch_default(key)) | |
68 | jump_label_update(key, JUMP_LABEL_ENABLE); | |
69 | else | |
70 | jump_label_update(key, JUMP_LABEL_DISABLE); | |
71 | } | |
72 | atomic_inc(&key->enabled); | |
73 | jump_label_unlock(); | |
74 | } | |
75 | EXPORT_SYMBOL_GPL(static_key_slow_inc); | |
76 | ||
77 | static void __static_key_slow_dec(struct static_key *key, | |
78 | unsigned long rate_limit, struct delayed_work *work) | |
79 | { | |
80 | if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) { | |
81 | WARN(atomic_read(&key->enabled) < 0, | |
82 | "jump label: negative count!\n"); | |
83 | return; | |
84 | } | |
85 | ||
86 | if (rate_limit) { | |
87 | atomic_inc(&key->enabled); | |
88 | schedule_delayed_work(work, rate_limit); | |
89 | } else { | |
90 | if (!jump_label_get_branch_default(key)) | |
91 | jump_label_update(key, JUMP_LABEL_DISABLE); | |
92 | else | |
93 | jump_label_update(key, JUMP_LABEL_ENABLE); | |
94 | } | |
95 | jump_label_unlock(); | |
96 | } | |
97 | ||
98 | static void jump_label_update_timeout(struct work_struct *work) | |
99 | { | |
100 | struct static_key_deferred *key = | |
101 | container_of(work, struct static_key_deferred, work.work); | |
102 | __static_key_slow_dec(&key->key, 0, NULL); | |
103 | } | |
104 | ||
105 | void static_key_slow_dec(struct static_key *key) | |
106 | { | |
107 | STATIC_KEY_CHECK_USE(); | |
108 | __static_key_slow_dec(key, 0, NULL); | |
109 | } | |
110 | EXPORT_SYMBOL_GPL(static_key_slow_dec); | |
111 | ||
112 | void static_key_slow_dec_deferred(struct static_key_deferred *key) | |
113 | { | |
114 | STATIC_KEY_CHECK_USE(); | |
115 | __static_key_slow_dec(&key->key, key->timeout, &key->work); | |
116 | } | |
117 | EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred); | |
118 | ||
119 | void jump_label_rate_limit(struct static_key_deferred *key, | |
120 | unsigned long rl) | |
121 | { | |
122 | STATIC_KEY_CHECK_USE(); | |
123 | key->timeout = rl; | |
124 | INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); | |
125 | } | |
126 | EXPORT_SYMBOL_GPL(jump_label_rate_limit); | |
127 | ||
128 | static int addr_conflict(struct jump_entry *entry, void *start, void *end) | |
129 | { | |
130 | if (entry->code <= (unsigned long)end && | |
131 | entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start) | |
132 | return 1; | |
133 | ||
134 | return 0; | |
135 | } | |
136 | ||
137 | static int __jump_label_text_reserved(struct jump_entry *iter_start, | |
138 | struct jump_entry *iter_stop, void *start, void *end) | |
139 | { | |
140 | struct jump_entry *iter; | |
141 | ||
142 | iter = iter_start; | |
143 | while (iter < iter_stop) { | |
144 | if (addr_conflict(iter, start, end)) | |
145 | return 1; | |
146 | iter++; | |
147 | } | |
148 | ||
149 | return 0; | |
150 | } | |
151 | ||
152 | /* | |
153 | * Update code which is definitely not currently executing. | |
154 | * Architectures which need heavyweight synchronization to modify | |
155 | * running code can override this to make the non-live update case | |
156 | * cheaper. | |
157 | */ | |
158 | void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, | |
159 | enum jump_label_type type) | |
160 | { | |
161 | arch_jump_label_transform(entry, type); | |
162 | } | |
163 | ||
164 | static void __jump_label_update(struct static_key *key, | |
165 | struct jump_entry *entry, | |
166 | struct jump_entry *stop, int enable) | |
167 | { | |
168 | for (; (entry < stop) && | |
169 | (entry->key == (jump_label_t)(unsigned long)key); | |
170 | entry++) { | |
171 | /* | |
172 | * entry->code set to 0 invalidates module init text sections | |
173 | * kernel_text_address() verifies we are not in core kernel | |
174 | * init code, see jump_label_invalidate_module_init(). | |
175 | */ | |
176 | if (entry->code && kernel_text_address(entry->code)) | |
177 | arch_jump_label_transform(entry, enable); | |
178 | } | |
179 | } | |
180 | ||
181 | static enum jump_label_type jump_label_type(struct static_key *key) | |
182 | { | |
183 | bool true_branch = jump_label_get_branch_default(key); | |
184 | bool state = static_key_enabled(key); | |
185 | ||
186 | if ((!true_branch && state) || (true_branch && !state)) | |
187 | return JUMP_LABEL_ENABLE; | |
188 | ||
189 | return JUMP_LABEL_DISABLE; | |
190 | } | |
191 | ||
192 | void __init jump_label_init(void) | |
193 | { | |
194 | struct jump_entry *iter_start = __start___jump_table; | |
195 | struct jump_entry *iter_stop = __stop___jump_table; | |
196 | struct static_key *key = NULL; | |
197 | struct jump_entry *iter; | |
198 | ||
199 | jump_label_lock(); | |
200 | jump_label_sort_entries(iter_start, iter_stop); | |
201 | ||
202 | for (iter = iter_start; iter < iter_stop; iter++) { | |
203 | struct static_key *iterk; | |
204 | ||
205 | iterk = (struct static_key *)(unsigned long)iter->key; | |
206 | arch_jump_label_transform_static(iter, jump_label_type(iterk)); | |
207 | if (iterk == key) | |
208 | continue; | |
209 | ||
210 | key = iterk; | |
211 | /* | |
212 | * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. | |
213 | */ | |
214 | *((unsigned long *)&key->entries) += (unsigned long)iter; | |
215 | #ifdef CONFIG_MODULES | |
216 | key->next = NULL; | |
217 | #endif | |
218 | } | |
219 | static_key_initialized = true; | |
220 | jump_label_unlock(); | |
221 | } | |
222 | ||
223 | #ifdef CONFIG_MODULES | |
224 | ||
225 | struct static_key_mod { | |
226 | struct static_key_mod *next; | |
227 | struct jump_entry *entries; | |
228 | struct module *mod; | |
229 | }; | |
230 | ||
231 | static int __jump_label_mod_text_reserved(void *start, void *end) | |
232 | { | |
233 | struct module *mod; | |
234 | ||
235 | mod = __module_text_address((unsigned long)start); | |
236 | if (!mod) | |
237 | return 0; | |
238 | ||
239 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); | |
240 | ||
241 | return __jump_label_text_reserved(mod->jump_entries, | |
242 | mod->jump_entries + mod->num_jump_entries, | |
243 | start, end); | |
244 | } | |
245 | ||
246 | static void __jump_label_mod_update(struct static_key *key, int enable) | |
247 | { | |
248 | struct static_key_mod *mod = key->next; | |
249 | ||
250 | while (mod) { | |
251 | struct module *m = mod->mod; | |
252 | ||
253 | __jump_label_update(key, mod->entries, | |
254 | m->jump_entries + m->num_jump_entries, | |
255 | enable); | |
256 | mod = mod->next; | |
257 | } | |
258 | } | |
259 | ||
260 | /*** | |
261 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() | |
262 | * @mod: module to patch | |
263 | * | |
264 | * Allow for run-time selection of the optimal nops. Before the module | |
265 | * loads patch these with arch_get_jump_label_nop(), which is specified by | |
266 | * the arch specific jump label code. | |
267 | */ | |
268 | void jump_label_apply_nops(struct module *mod) | |
269 | { | |
270 | struct jump_entry *iter_start = mod->jump_entries; | |
271 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
272 | struct jump_entry *iter; | |
273 | ||
274 | /* if the module doesn't have jump label entries, just return */ | |
275 | if (iter_start == iter_stop) | |
276 | return; | |
277 | ||
278 | for (iter = iter_start; iter < iter_stop; iter++) { | |
279 | arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE); | |
280 | } | |
281 | } | |
282 | ||
283 | static int jump_label_add_module(struct module *mod) | |
284 | { | |
285 | struct jump_entry *iter_start = mod->jump_entries; | |
286 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
287 | struct jump_entry *iter; | |
288 | struct static_key *key = NULL; | |
289 | struct static_key_mod *jlm; | |
290 | ||
291 | /* if the module doesn't have jump label entries, just return */ | |
292 | if (iter_start == iter_stop) | |
293 | return 0; | |
294 | ||
295 | jump_label_sort_entries(iter_start, iter_stop); | |
296 | ||
297 | for (iter = iter_start; iter < iter_stop; iter++) { | |
298 | struct static_key *iterk; | |
299 | ||
300 | iterk = (struct static_key *)(unsigned long)iter->key; | |
301 | if (iterk == key) | |
302 | continue; | |
303 | ||
304 | key = iterk; | |
305 | if (__module_address(iter->key) == mod) { | |
306 | /* | |
307 | * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. | |
308 | */ | |
309 | *((unsigned long *)&key->entries) += (unsigned long)iter; | |
310 | key->next = NULL; | |
311 | continue; | |
312 | } | |
313 | jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); | |
314 | if (!jlm) | |
315 | return -ENOMEM; | |
316 | jlm->mod = mod; | |
317 | jlm->entries = iter; | |
318 | jlm->next = key->next; | |
319 | key->next = jlm; | |
320 | ||
321 | if (jump_label_type(key) == JUMP_LABEL_ENABLE) | |
322 | __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE); | |
323 | } | |
324 | ||
325 | return 0; | |
326 | } | |
327 | ||
328 | static void jump_label_del_module(struct module *mod) | |
329 | { | |
330 | struct jump_entry *iter_start = mod->jump_entries; | |
331 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
332 | struct jump_entry *iter; | |
333 | struct static_key *key = NULL; | |
334 | struct static_key_mod *jlm, **prev; | |
335 | ||
336 | for (iter = iter_start; iter < iter_stop; iter++) { | |
337 | if (iter->key == (jump_label_t)(unsigned long)key) | |
338 | continue; | |
339 | ||
340 | key = (struct static_key *)(unsigned long)iter->key; | |
341 | ||
342 | if (__module_address(iter->key) == mod) | |
343 | continue; | |
344 | ||
345 | prev = &key->next; | |
346 | jlm = key->next; | |
347 | ||
348 | while (jlm && jlm->mod != mod) { | |
349 | prev = &jlm->next; | |
350 | jlm = jlm->next; | |
351 | } | |
352 | ||
353 | if (jlm) { | |
354 | *prev = jlm->next; | |
355 | kfree(jlm); | |
356 | } | |
357 | } | |
358 | } | |
359 | ||
360 | static void jump_label_invalidate_module_init(struct module *mod) | |
361 | { | |
362 | struct jump_entry *iter_start = mod->jump_entries; | |
363 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
364 | struct jump_entry *iter; | |
365 | ||
366 | for (iter = iter_start; iter < iter_stop; iter++) { | |
367 | if (within_module_init(iter->code, mod)) | |
368 | iter->code = 0; | |
369 | } | |
370 | } | |
371 | ||
372 | static int | |
373 | jump_label_module_notify(struct notifier_block *self, unsigned long val, | |
374 | void *data) | |
375 | { | |
376 | struct module *mod = data; | |
377 | int ret = 0; | |
378 | ||
379 | switch (val) { | |
380 | case MODULE_STATE_COMING: | |
381 | jump_label_lock(); | |
382 | ret = jump_label_add_module(mod); | |
383 | if (ret) | |
384 | jump_label_del_module(mod); | |
385 | jump_label_unlock(); | |
386 | break; | |
387 | case MODULE_STATE_GOING: | |
388 | jump_label_lock(); | |
389 | jump_label_del_module(mod); | |
390 | jump_label_unlock(); | |
391 | break; | |
392 | case MODULE_STATE_LIVE: | |
393 | jump_label_lock(); | |
394 | jump_label_invalidate_module_init(mod); | |
395 | jump_label_unlock(); | |
396 | break; | |
397 | } | |
398 | ||
399 | return notifier_from_errno(ret); | |
400 | } | |
401 | ||
402 | struct notifier_block jump_label_module_nb = { | |
403 | .notifier_call = jump_label_module_notify, | |
404 | .priority = 1, /* higher than tracepoints */ | |
405 | }; | |
406 | ||
407 | static __init int jump_label_init_module(void) | |
408 | { | |
409 | return register_module_notifier(&jump_label_module_nb); | |
410 | } | |
411 | early_initcall(jump_label_init_module); | |
412 | ||
413 | #endif /* CONFIG_MODULES */ | |
414 | ||
415 | /*** | |
416 | * jump_label_text_reserved - check if addr range is reserved | |
417 | * @start: start text addr | |
418 | * @end: end text addr | |
419 | * | |
420 | * checks if the text addr located between @start and @end | |
421 | * overlaps with any of the jump label patch addresses. Code | |
422 | * that wants to modify kernel text should first verify that | |
423 | * it does not overlap with any of the jump label addresses. | |
424 | * Caller must hold jump_label_mutex. | |
425 | * | |
426 | * returns 1 if there is an overlap, 0 otherwise | |
427 | */ | |
428 | int jump_label_text_reserved(void *start, void *end) | |
429 | { | |
430 | int ret = __jump_label_text_reserved(__start___jump_table, | |
431 | __stop___jump_table, start, end); | |
432 | ||
433 | if (ret) | |
434 | return ret; | |
435 | ||
436 | #ifdef CONFIG_MODULES | |
437 | ret = __jump_label_mod_text_reserved(start, end); | |
438 | #endif | |
439 | return ret; | |
440 | } | |
441 | ||
442 | static void jump_label_update(struct static_key *key, int enable) | |
443 | { | |
444 | struct jump_entry *stop = __stop___jump_table; | |
445 | struct jump_entry *entry = jump_label_get_entries(key); | |
446 | ||
447 | #ifdef CONFIG_MODULES | |
448 | struct module *mod = __module_address((unsigned long)key); | |
449 | ||
450 | __jump_label_mod_update(key, enable); | |
451 | ||
452 | if (mod) | |
453 | stop = mod->jump_entries + mod->num_jump_entries; | |
454 | #endif | |
455 | /* if there are no users, entry can be NULL */ | |
456 | if (entry) | |
457 | __jump_label_update(key, entry, stop, enable); | |
458 | } | |
459 | ||
460 | #endif |