projects/linux·blob v3.7 · refs

454 lines · 10.8 KiB

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