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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 JB |
68 | jump_label_lock(); |
69 | if (atomic_add_return(1, &key->enabled) == 1) | |
70 | jump_label_update(key, JUMP_LABEL_ENABLE); | |
71 | jump_label_unlock(); | |
bf5438fc JB |
72 | } |
73 | ||
d430d3d7 | 74 | void jump_label_dec(struct jump_label_key *key) |
bf5438fc | 75 | { |
d430d3d7 JB |
76 | if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) |
77 | return; | |
bf5438fc | 78 | |
d430d3d7 | 79 | jump_label_update(key, JUMP_LABEL_DISABLE); |
91bad2f8 | 80 | jump_label_unlock(); |
bf5438fc JB |
81 | } |
82 | ||
4c3ef6d7 JB |
83 | static 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 | ||
d430d3d7 JB |
92 | static int __jump_label_text_reserved(struct jump_entry *iter_start, |
93 | struct jump_entry *iter_stop, void *start, void *end) | |
4c3ef6d7 | 94 | { |
4c3ef6d7 | 95 | struct jump_entry *iter; |
4c3ef6d7 | 96 | |
4c3ef6d7 JB |
97 | iter = iter_start; |
98 | while (iter < iter_stop) { | |
d430d3d7 JB |
99 | if (addr_conflict(iter, start, end)) |
100 | return 1; | |
4c3ef6d7 JB |
101 | iter++; |
102 | } | |
103 | ||
d430d3d7 JB |
104 | return 0; |
105 | } | |
106 | ||
107 | static void __jump_label_update(struct jump_label_key *key, | |
7cbc5b8d JO |
108 | struct jump_entry *entry, |
109 | struct jump_entry *stop, int enable) | |
d430d3d7 | 110 | { |
7cbc5b8d JO |
111 | for (; (entry < stop) && |
112 | (entry->key == (jump_label_t)(unsigned long)key); | |
113 | entry++) { | |
d430d3d7 JB |
114 | /* |
115 | * entry->code set to 0 invalidates module init text sections | |
116 | * kernel_text_address() verifies we are not in core kernel | |
117 | * init code, see jump_label_invalidate_module_init(). | |
118 | */ | |
119 | if (entry->code && kernel_text_address(entry->code)) | |
120 | arch_jump_label_transform(entry, enable); | |
121 | } | |
4c3ef6d7 JB |
122 | } |
123 | ||
d430d3d7 | 124 | static __init int jump_label_init(void) |
bf5438fc | 125 | { |
bf5438fc JB |
126 | struct jump_entry *iter_start = __start___jump_table; |
127 | struct jump_entry *iter_stop = __stop___jump_table; | |
d430d3d7 | 128 | struct jump_label_key *key = NULL; |
bf5438fc JB |
129 | struct jump_entry *iter; |
130 | ||
91bad2f8 | 131 | jump_label_lock(); |
d430d3d7 JB |
132 | jump_label_sort_entries(iter_start, iter_stop); |
133 | ||
134 | for (iter = iter_start; iter < iter_stop; iter++) { | |
37348804 JF |
135 | struct jump_label_key *iterk; |
136 | ||
137 | iterk = (struct jump_label_key *)(unsigned long)iter->key; | |
138 | arch_jump_label_transform(iter, jump_label_enabled(iterk) ? | |
139 | JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE); | |
140 | if (iterk == key) | |
d430d3d7 JB |
141 | continue; |
142 | ||
37348804 | 143 | key = iterk; |
d430d3d7 JB |
144 | key->entries = iter; |
145 | #ifdef CONFIG_MODULES | |
146 | key->next = NULL; | |
147 | #endif | |
bf5438fc | 148 | } |
91bad2f8 | 149 | jump_label_unlock(); |
d430d3d7 JB |
150 | |
151 | return 0; | |
bf5438fc | 152 | } |
d430d3d7 | 153 | early_initcall(jump_label_init); |
bf5438fc JB |
154 | |
155 | #ifdef CONFIG_MODULES | |
156 | ||
d430d3d7 JB |
157 | struct jump_label_mod { |
158 | struct jump_label_mod *next; | |
159 | struct jump_entry *entries; | |
160 | struct module *mod; | |
161 | }; | |
162 | ||
163 | static int __jump_label_mod_text_reserved(void *start, void *end) | |
164 | { | |
165 | struct module *mod; | |
166 | ||
167 | mod = __module_text_address((unsigned long)start); | |
168 | if (!mod) | |
169 | return 0; | |
170 | ||
171 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); | |
172 | ||
173 | return __jump_label_text_reserved(mod->jump_entries, | |
174 | mod->jump_entries + mod->num_jump_entries, | |
175 | start, end); | |
176 | } | |
177 | ||
178 | static void __jump_label_mod_update(struct jump_label_key *key, int enable) | |
179 | { | |
180 | struct jump_label_mod *mod = key->next; | |
181 | ||
182 | while (mod) { | |
7cbc5b8d JO |
183 | struct module *m = mod->mod; |
184 | ||
185 | __jump_label_update(key, mod->entries, | |
186 | m->jump_entries + m->num_jump_entries, | |
187 | enable); | |
d430d3d7 JB |
188 | mod = mod->next; |
189 | } | |
190 | } | |
191 | ||
192 | /*** | |
193 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() | |
194 | * @mod: module to patch | |
195 | * | |
196 | * Allow for run-time selection of the optimal nops. Before the module | |
197 | * loads patch these with arch_get_jump_label_nop(), which is specified by | |
198 | * the arch specific jump label code. | |
199 | */ | |
200 | void jump_label_apply_nops(struct module *mod) | |
bf5438fc | 201 | { |
d430d3d7 JB |
202 | struct jump_entry *iter_start = mod->jump_entries; |
203 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
204 | struct jump_entry *iter; | |
205 | ||
206 | /* if the module doesn't have jump label entries, just return */ | |
207 | if (iter_start == iter_stop) | |
208 | return; | |
209 | ||
210 | for (iter = iter_start; iter < iter_stop; iter++) | |
37348804 | 211 | arch_jump_label_transform(iter, JUMP_LABEL_DISABLE); |
bf5438fc JB |
212 | } |
213 | ||
d430d3d7 | 214 | static int jump_label_add_module(struct module *mod) |
bf5438fc | 215 | { |
d430d3d7 JB |
216 | struct jump_entry *iter_start = mod->jump_entries; |
217 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
218 | struct jump_entry *iter; | |
219 | struct jump_label_key *key = NULL; | |
220 | struct jump_label_mod *jlm; | |
bf5438fc JB |
221 | |
222 | /* if the module doesn't have jump label entries, just return */ | |
d430d3d7 | 223 | if (iter_start == iter_stop) |
bf5438fc JB |
224 | return 0; |
225 | ||
d430d3d7 JB |
226 | jump_label_sort_entries(iter_start, iter_stop); |
227 | ||
228 | for (iter = iter_start; iter < iter_stop; iter++) { | |
229 | if (iter->key == (jump_label_t)(unsigned long)key) | |
230 | continue; | |
231 | ||
232 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
233 | ||
234 | if (__module_address(iter->key) == mod) { | |
235 | atomic_set(&key->enabled, 0); | |
236 | key->entries = iter; | |
237 | key->next = NULL; | |
238 | continue; | |
bf5438fc | 239 | } |
d430d3d7 JB |
240 | |
241 | jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL); | |
242 | if (!jlm) | |
243 | return -ENOMEM; | |
244 | ||
245 | jlm->mod = mod; | |
246 | jlm->entries = iter; | |
247 | jlm->next = key->next; | |
248 | key->next = jlm; | |
249 | ||
250 | if (jump_label_enabled(key)) | |
7cbc5b8d JO |
251 | __jump_label_update(key, iter, iter_stop, |
252 | JUMP_LABEL_ENABLE); | |
bf5438fc | 253 | } |
d430d3d7 | 254 | |
bf5438fc JB |
255 | return 0; |
256 | } | |
257 | ||
d430d3d7 | 258 | static void jump_label_del_module(struct module *mod) |
bf5438fc | 259 | { |
d430d3d7 JB |
260 | struct jump_entry *iter_start = mod->jump_entries; |
261 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
262 | struct jump_entry *iter; | |
263 | struct jump_label_key *key = NULL; | |
264 | struct jump_label_mod *jlm, **prev; | |
bf5438fc | 265 | |
d430d3d7 JB |
266 | for (iter = iter_start; iter < iter_stop; iter++) { |
267 | if (iter->key == (jump_label_t)(unsigned long)key) | |
268 | continue; | |
269 | ||
270 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
271 | ||
272 | if (__module_address(iter->key) == mod) | |
273 | continue; | |
274 | ||
275 | prev = &key->next; | |
276 | jlm = key->next; | |
bf5438fc | 277 | |
d430d3d7 JB |
278 | while (jlm && jlm->mod != mod) { |
279 | prev = &jlm->next; | |
280 | jlm = jlm->next; | |
281 | } | |
282 | ||
283 | if (jlm) { | |
284 | *prev = jlm->next; | |
285 | kfree(jlm); | |
bf5438fc JB |
286 | } |
287 | } | |
288 | } | |
289 | ||
d430d3d7 | 290 | static void jump_label_invalidate_module_init(struct module *mod) |
b842f8fa | 291 | { |
d430d3d7 JB |
292 | struct jump_entry *iter_start = mod->jump_entries; |
293 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
b842f8fa | 294 | struct jump_entry *iter; |
b842f8fa | 295 | |
d430d3d7 JB |
296 | for (iter = iter_start; iter < iter_stop; iter++) { |
297 | if (within_module_init(iter->code, mod)) | |
298 | iter->code = 0; | |
b842f8fa JB |
299 | } |
300 | } | |
301 | ||
bf5438fc JB |
302 | static int |
303 | jump_label_module_notify(struct notifier_block *self, unsigned long val, | |
304 | void *data) | |
305 | { | |
306 | struct module *mod = data; | |
307 | int ret = 0; | |
308 | ||
309 | switch (val) { | |
310 | case MODULE_STATE_COMING: | |
91bad2f8 | 311 | jump_label_lock(); |
d430d3d7 | 312 | ret = jump_label_add_module(mod); |
bf5438fc | 313 | if (ret) |
d430d3d7 | 314 | jump_label_del_module(mod); |
91bad2f8 | 315 | jump_label_unlock(); |
bf5438fc JB |
316 | break; |
317 | case MODULE_STATE_GOING: | |
91bad2f8 | 318 | jump_label_lock(); |
d430d3d7 | 319 | jump_label_del_module(mod); |
91bad2f8 | 320 | jump_label_unlock(); |
bf5438fc | 321 | break; |
b842f8fa | 322 | case MODULE_STATE_LIVE: |
91bad2f8 | 323 | jump_label_lock(); |
d430d3d7 | 324 | jump_label_invalidate_module_init(mod); |
91bad2f8 | 325 | jump_label_unlock(); |
b842f8fa | 326 | break; |
bf5438fc | 327 | } |
bf5438fc | 328 | |
d430d3d7 | 329 | return notifier_from_errno(ret); |
bf5438fc JB |
330 | } |
331 | ||
332 | struct notifier_block jump_label_module_nb = { | |
333 | .notifier_call = jump_label_module_notify, | |
d430d3d7 | 334 | .priority = 1, /* higher than tracepoints */ |
bf5438fc JB |
335 | }; |
336 | ||
d430d3d7 | 337 | static __init int jump_label_init_module(void) |
bf5438fc JB |
338 | { |
339 | return register_module_notifier(&jump_label_module_nb); | |
340 | } | |
d430d3d7 | 341 | early_initcall(jump_label_init_module); |
bf5438fc JB |
342 | |
343 | #endif /* CONFIG_MODULES */ | |
344 | ||
d430d3d7 JB |
345 | /*** |
346 | * jump_label_text_reserved - check if addr range is reserved | |
347 | * @start: start text addr | |
348 | * @end: end text addr | |
349 | * | |
350 | * checks if the text addr located between @start and @end | |
351 | * overlaps with any of the jump label patch addresses. Code | |
352 | * that wants to modify kernel text should first verify that | |
353 | * it does not overlap with any of the jump label addresses. | |
354 | * Caller must hold jump_label_mutex. | |
355 | * | |
356 | * returns 1 if there is an overlap, 0 otherwise | |
357 | */ | |
358 | int jump_label_text_reserved(void *start, void *end) | |
359 | { | |
360 | int ret = __jump_label_text_reserved(__start___jump_table, | |
361 | __stop___jump_table, start, end); | |
362 | ||
363 | if (ret) | |
364 | return ret; | |
365 | ||
366 | #ifdef CONFIG_MODULES | |
367 | ret = __jump_label_mod_text_reserved(start, end); | |
368 | #endif | |
369 | return ret; | |
370 | } | |
371 | ||
372 | static void jump_label_update(struct jump_label_key *key, int enable) | |
373 | { | |
140fe3b1 | 374 | struct jump_entry *entry = key->entries, *stop = __stop___jump_table; |
d430d3d7 JB |
375 | |
376 | #ifdef CONFIG_MODULES | |
140fe3b1 XG |
377 | struct module *mod = __module_address((jump_label_t)key); |
378 | ||
d430d3d7 | 379 | __jump_label_mod_update(key, enable); |
140fe3b1 XG |
380 | |
381 | if (mod) | |
382 | stop = mod->jump_entries + mod->num_jump_entries; | |
d430d3d7 | 383 | #endif |
140fe3b1 XG |
384 | /* if there are no users, entry can be NULL */ |
385 | if (entry) | |
386 | __jump_label_update(key, entry, stop, enable); | |
d430d3d7 JB |
387 | } |
388 | ||
bf5438fc | 389 | #endif |