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Jason Baronbf5438fc2010-09-17 11:09:00 -04001/*
2 * jump label support
3 *
4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
Jason Barond430d3d2011-03-16 17:29:47 -04005 * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
Jason Baronbf5438fc2010-09-17 11:09:00 -04006 *
7 */
Jason Baronbf5438fc2010-09-17 11:09:00 -04008#include <linux/memory.h>
9#include <linux/uaccess.h>
10#include <linux/module.h>
11#include <linux/list.h>
Jason Baronbf5438fc2010-09-17 11:09:00 -040012#include <linux/slab.h>
13#include <linux/sort.h>
14#include <linux/err.h>
Jason Barond430d3d2011-03-16 17:29:47 -040015#include <linux/jump_label.h>
Jason Baronbf5438fc2010-09-17 11:09:00 -040016
17#ifdef HAVE_JUMP_LABEL
18
Jason Baronbf5438fc2010-09-17 11:09:00 -040019/* mutex to protect coming/going of the the jump_label table */
20static DEFINE_MUTEX(jump_label_mutex);
21
Jason Baron91bad2f2010-10-01 17:23:48 -040022void 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
Jason Barond430d3d2011-03-16 17:29:47 -040032bool jump_label_enabled(struct jump_label_key *key)
33{
34 return !!atomic_read(&key->enabled);
35}
36
Jason Baronbf5438fc2010-09-17 11:09:00 -040037static 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
51static void
Jason Barond430d3d2011-03-16 17:29:47 -040052jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
Jason Baronbf5438fc2010-09-17 11:09:00 -040053{
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
Jason Barond430d3d2011-03-16 17:29:47 -040061static void jump_label_update(struct jump_label_key *key, int enable);
62
63void jump_label_inc(struct jump_label_key *key)
Jason Baronbf5438fc2010-09-17 11:09:00 -040064{
Jason Barond430d3d2011-03-16 17:29:47 -040065 if (atomic_inc_not_zero(&key->enabled))
66 return;
Jason Baronbf5438fc2010-09-17 11:09:00 -040067
Jason Baron91bad2f2010-10-01 17:23:48 -040068 jump_label_lock();
Jason Barond430d3d2011-03-16 17:29:47 -040069 if (atomic_add_return(1, &key->enabled) == 1)
70 jump_label_update(key, JUMP_LABEL_ENABLE);
71 jump_label_unlock();
72}
73
74void jump_label_dec(struct jump_label_key *key)
75{
76 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
77 return;
78
79 jump_label_update(key, JUMP_LABEL_DISABLE);
Jason Baron91bad2f2010-10-01 17:23:48 -040080 jump_label_unlock();
Jason Baronbf5438fc2010-09-17 11:09:00 -040081}
82
Jason Baron4c3ef6d2010-09-17 11:09:08 -040083static int addr_conflict(struct jump_entry *entry, void *start, void *end)
84{
85 if (entry->code <= (unsigned long)end &&
86 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
87 return 1;
88
89 return 0;
90}
91
Jason Barond430d3d2011-03-16 17:29:47 -040092static int __jump_label_text_reserved(struct jump_entry *iter_start,
93 struct jump_entry *iter_stop, void *start, void *end)
Jason Baron4c3ef6d2010-09-17 11:09:08 -040094{
Jason Baron4c3ef6d2010-09-17 11:09:08 -040095 struct jump_entry *iter;
Jason Baron4c3ef6d2010-09-17 11:09:08 -040096
Jason Barond430d3d2011-03-16 17:29:47 -040097 iter = iter_start;
98 while (iter < iter_stop) {
99 if (addr_conflict(iter, start, end))
100 return 1;
101 iter++;
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400102 }
Jason Barond430d3d2011-03-16 17:29:47 -0400103
104 return 0;
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400105}
106
Jeremy Fitzhardinge20284aa2011-10-03 11:01:46 -0700107/*
108 * Update code which is definitely not currently executing.
109 * Architectures which need heavyweight synchronization to modify
110 * running code can override this to make the non-live update case
111 * cheaper.
112 */
113void __weak arch_jump_label_transform_static(struct jump_entry *entry,
114 enum jump_label_type type)
115{
116 arch_jump_label_transform(entry, type);
117}
118
Jason Barond430d3d2011-03-16 17:29:47 -0400119static void __jump_label_update(struct jump_label_key *key,
Jiri Olsa7cbc5b82011-05-10 12:43:46 +0200120 struct jump_entry *entry,
121 struct jump_entry *stop, int enable)
Jason Barond430d3d2011-03-16 17:29:47 -0400122{
Jiri Olsa7cbc5b82011-05-10 12:43:46 +0200123 for (; (entry < stop) &&
124 (entry->key == (jump_label_t)(unsigned long)key);
125 entry++) {
Jason Barond430d3d2011-03-16 17:29:47 -0400126 /*
127 * entry->code set to 0 invalidates module init text sections
128 * kernel_text_address() verifies we are not in core kernel
129 * init code, see jump_label_invalidate_module_init().
130 */
131 if (entry->code && kernel_text_address(entry->code))
132 arch_jump_label_transform(entry, enable);
133 }
134}
135
Jason Barond430d3d2011-03-16 17:29:47 -0400136static __init int jump_label_init(void)
137{
138 struct jump_entry *iter_start = __start___jump_table;
139 struct jump_entry *iter_stop = __stop___jump_table;
140 struct jump_label_key *key = NULL;
141 struct jump_entry *iter;
142
143 jump_label_lock();
144 jump_label_sort_entries(iter_start, iter_stop);
145
146 for (iter = iter_start; iter < iter_stop; iter++) {
Jeremy Fitzhardinge37348802011-09-29 11:10:05 -0700147 struct jump_label_key *iterk;
148
149 iterk = (struct jump_label_key *)(unsigned long)iter->key;
Jeremy Fitzhardinge20284aa2011-10-03 11:01:46 -0700150 arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
151 JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
Jeremy Fitzhardinge37348802011-09-29 11:10:05 -0700152 if (iterk == key)
Jason Barond430d3d2011-03-16 17:29:47 -0400153 continue;
154
Jeremy Fitzhardinge37348802011-09-29 11:10:05 -0700155 key = iterk;
Jason Barond430d3d2011-03-16 17:29:47 -0400156 key->entries = iter;
157#ifdef CONFIG_MODULES
158 key->next = NULL;
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400159#endif
Jason Barond430d3d2011-03-16 17:29:47 -0400160 }
161 jump_label_unlock();
162
163 return 0;
164}
165early_initcall(jump_label_init);
166
167#ifdef CONFIG_MODULES
168
169struct jump_label_mod {
170 struct jump_label_mod *next;
171 struct jump_entry *entries;
172 struct module *mod;
173};
174
175static int __jump_label_mod_text_reserved(void *start, void *end)
176{
177 struct module *mod;
178
179 mod = __module_text_address((unsigned long)start);
180 if (!mod)
181 return 0;
182
183 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
184
185 return __jump_label_text_reserved(mod->jump_entries,
186 mod->jump_entries + mod->num_jump_entries,
187 start, end);
188}
189
190static void __jump_label_mod_update(struct jump_label_key *key, int enable)
191{
192 struct jump_label_mod *mod = key->next;
193
194 while (mod) {
Jiri Olsa7cbc5b82011-05-10 12:43:46 +0200195 struct module *m = mod->mod;
196
197 __jump_label_update(key, mod->entries,
198 m->jump_entries + m->num_jump_entries,
199 enable);
Jason Barond430d3d2011-03-16 17:29:47 -0400200 mod = mod->next;
201 }
202}
203
204/***
205 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
206 * @mod: module to patch
207 *
208 * Allow for run-time selection of the optimal nops. Before the module
209 * loads patch these with arch_get_jump_label_nop(), which is specified by
210 * the arch specific jump label code.
211 */
212void jump_label_apply_nops(struct module *mod)
213{
214 struct jump_entry *iter_start = mod->jump_entries;
215 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
216 struct jump_entry *iter;
217
218 /* if the module doesn't have jump label entries, just return */
219 if (iter_start == iter_stop)
220 return;
221
222 for (iter = iter_start; iter < iter_stop; iter++)
Jeremy Fitzhardinge20284aa2011-10-03 11:01:46 -0700223 arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
Jason Barond430d3d2011-03-16 17:29:47 -0400224}
225
226static int jump_label_add_module(struct module *mod)
227{
228 struct jump_entry *iter_start = mod->jump_entries;
229 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
230 struct jump_entry *iter;
231 struct jump_label_key *key = NULL;
232 struct jump_label_mod *jlm;
233
234 /* if the module doesn't have jump label entries, just return */
235 if (iter_start == iter_stop)
236 return 0;
237
238 jump_label_sort_entries(iter_start, iter_stop);
239
240 for (iter = iter_start; iter < iter_stop; iter++) {
241 if (iter->key == (jump_label_t)(unsigned long)key)
242 continue;
243
244 key = (struct jump_label_key *)(unsigned long)iter->key;
245
246 if (__module_address(iter->key) == mod) {
247 atomic_set(&key->enabled, 0);
248 key->entries = iter;
249 key->next = NULL;
250 continue;
251 }
252
253 jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
254 if (!jlm)
255 return -ENOMEM;
256
257 jlm->mod = mod;
258 jlm->entries = iter;
259 jlm->next = key->next;
260 key->next = jlm;
261
262 if (jump_label_enabled(key))
Jiri Olsa7cbc5b82011-05-10 12:43:46 +0200263 __jump_label_update(key, iter, iter_stop,
264 JUMP_LABEL_ENABLE);
Jason Barond430d3d2011-03-16 17:29:47 -0400265 }
266
267 return 0;
268}
269
270static void jump_label_del_module(struct module *mod)
271{
272 struct jump_entry *iter_start = mod->jump_entries;
273 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
274 struct jump_entry *iter;
275 struct jump_label_key *key = NULL;
276 struct jump_label_mod *jlm, **prev;
277
278 for (iter = iter_start; iter < iter_stop; iter++) {
279 if (iter->key == (jump_label_t)(unsigned long)key)
280 continue;
281
282 key = (struct jump_label_key *)(unsigned long)iter->key;
283
284 if (__module_address(iter->key) == mod)
285 continue;
286
287 prev = &key->next;
288 jlm = key->next;
289
290 while (jlm && jlm->mod != mod) {
291 prev = &jlm->next;
292 jlm = jlm->next;
293 }
294
295 if (jlm) {
296 *prev = jlm->next;
297 kfree(jlm);
298 }
299 }
300}
301
302static void jump_label_invalidate_module_init(struct module *mod)
303{
304 struct jump_entry *iter_start = mod->jump_entries;
305 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
306 struct jump_entry *iter;
307
308 for (iter = iter_start; iter < iter_stop; iter++) {
309 if (within_module_init(iter->code, mod))
310 iter->code = 0;
311 }
312}
313
314static int
315jump_label_module_notify(struct notifier_block *self, unsigned long val,
316 void *data)
317{
318 struct module *mod = data;
319 int ret = 0;
320
321 switch (val) {
322 case MODULE_STATE_COMING:
323 jump_label_lock();
324 ret = jump_label_add_module(mod);
325 if (ret)
326 jump_label_del_module(mod);
327 jump_label_unlock();
328 break;
329 case MODULE_STATE_GOING:
330 jump_label_lock();
331 jump_label_del_module(mod);
332 jump_label_unlock();
333 break;
334 case MODULE_STATE_LIVE:
335 jump_label_lock();
336 jump_label_invalidate_module_init(mod);
337 jump_label_unlock();
338 break;
339 }
340
341 return notifier_from_errno(ret);
342}
343
344struct notifier_block jump_label_module_nb = {
345 .notifier_call = jump_label_module_notify,
346 .priority = 1, /* higher than tracepoints */
347};
348
349static __init int jump_label_init_module(void)
350{
351 return register_module_notifier(&jump_label_module_nb);
352}
353early_initcall(jump_label_init_module);
354
355#endif /* CONFIG_MODULES */
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400356
357/***
358 * jump_label_text_reserved - check if addr range is reserved
359 * @start: start text addr
360 * @end: end text addr
361 *
362 * checks if the text addr located between @start and @end
363 * overlaps with any of the jump label patch addresses. Code
364 * that wants to modify kernel text should first verify that
365 * it does not overlap with any of the jump label addresses.
Jason Baron91bad2f2010-10-01 17:23:48 -0400366 * Caller must hold jump_label_mutex.
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400367 *
368 * returns 1 if there is an overlap, 0 otherwise
369 */
370int jump_label_text_reserved(void *start, void *end)
371{
Jason Barond430d3d2011-03-16 17:29:47 -0400372 int ret = __jump_label_text_reserved(__start___jump_table,
373 __stop___jump_table, start, end);
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400374
Jason Barond430d3d2011-03-16 17:29:47 -0400375 if (ret)
376 return ret;
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400377
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400378#ifdef CONFIG_MODULES
Jason Barond430d3d2011-03-16 17:29:47 -0400379 ret = __jump_label_mod_text_reserved(start, end);
Jason Baron4c3ef6d2010-09-17 11:09:08 -0400380#endif
Jason Baronbf5438fc2010-09-17 11:09:00 -0400381 return ret;
382}
Jason Barond430d3d2011-03-16 17:29:47 -0400383
384static void jump_label_update(struct jump_label_key *key, int enable)
385{
Xiao Guangrong140fe3b2011-06-21 10:35:55 +0800386 struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
Jason Baronbf5438fc2010-09-17 11:09:00 -0400387
388#ifdef CONFIG_MODULES
Xiao Guangrong140fe3b2011-06-21 10:35:55 +0800389 struct module *mod = __module_address((jump_label_t)key);
390
Jason Barond430d3d2011-03-16 17:29:47 -0400391 __jump_label_mod_update(key, enable);
Xiao Guangrong140fe3b2011-06-21 10:35:55 +0800392
393 if (mod)
394 stop = mod->jump_entries + mod->num_jump_entries;
Jason Barond430d3d2011-03-16 17:29:47 -0400395#endif
Xiao Guangrong140fe3b2011-06-21 10:35:55 +0800396 /* if there are no users, entry can be NULL */
397 if (entry)
398 __jump_label_update(key, entry, stop, enable);
Jason Baronbf5438fc2010-09-17 11:09:00 -0400399}
400
Jason Baronbf5438fc2010-09-17 11:09:00 -0400401#endif