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