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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, | |
108 | struct jump_entry *entry, int enable) | |
109 | { | |
110 | for (; entry->key == (jump_label_t)(unsigned long)key; entry++) { | |
111 | /* | |
112 | * entry->code set to 0 invalidates module init text sections | |
113 | * kernel_text_address() verifies we are not in core kernel | |
114 | * init code, see jump_label_invalidate_module_init(). | |
115 | */ | |
116 | if (entry->code && kernel_text_address(entry->code)) | |
117 | arch_jump_label_transform(entry, enable); | |
118 | } | |
4c3ef6d7 JB |
119 | } |
120 | ||
95bcd683 SR |
121 | /* |
122 | * Not all archs need this. | |
123 | */ | |
124 | void __weak arch_jump_label_text_poke_early(jump_label_t addr) | |
125 | { | |
126 | } | |
127 | ||
d430d3d7 | 128 | static __init int jump_label_init(void) |
bf5438fc | 129 | { |
bf5438fc JB |
130 | struct jump_entry *iter_start = __start___jump_table; |
131 | struct jump_entry *iter_stop = __stop___jump_table; | |
d430d3d7 | 132 | struct jump_label_key *key = NULL; |
bf5438fc JB |
133 | struct jump_entry *iter; |
134 | ||
91bad2f8 | 135 | jump_label_lock(); |
d430d3d7 JB |
136 | jump_label_sort_entries(iter_start, iter_stop); |
137 | ||
138 | for (iter = iter_start; iter < iter_stop; iter++) { | |
bf5438fc | 139 | arch_jump_label_text_poke_early(iter->code); |
d430d3d7 JB |
140 | if (iter->key == (jump_label_t)(unsigned long)key) |
141 | continue; | |
142 | ||
143 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
144 | atomic_set(&key->enabled, 0); | |
145 | key->entries = iter; | |
146 | #ifdef CONFIG_MODULES | |
147 | key->next = NULL; | |
148 | #endif | |
bf5438fc | 149 | } |
91bad2f8 | 150 | jump_label_unlock(); |
d430d3d7 JB |
151 | |
152 | return 0; | |
bf5438fc | 153 | } |
d430d3d7 | 154 | early_initcall(jump_label_init); |
bf5438fc JB |
155 | |
156 | #ifdef CONFIG_MODULES | |
157 | ||
d430d3d7 JB |
158 | struct jump_label_mod { |
159 | struct jump_label_mod *next; | |
160 | struct jump_entry *entries; | |
161 | struct module *mod; | |
162 | }; | |
163 | ||
164 | static int __jump_label_mod_text_reserved(void *start, void *end) | |
165 | { | |
166 | struct module *mod; | |
167 | ||
168 | mod = __module_text_address((unsigned long)start); | |
169 | if (!mod) | |
170 | return 0; | |
171 | ||
172 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); | |
173 | ||
174 | return __jump_label_text_reserved(mod->jump_entries, | |
175 | mod->jump_entries + mod->num_jump_entries, | |
176 | start, end); | |
177 | } | |
178 | ||
179 | static void __jump_label_mod_update(struct jump_label_key *key, int enable) | |
180 | { | |
181 | struct jump_label_mod *mod = key->next; | |
182 | ||
183 | while (mod) { | |
184 | __jump_label_update(key, mod->entries, enable); | |
185 | mod = mod->next; | |
186 | } | |
187 | } | |
188 | ||
189 | /*** | |
190 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() | |
191 | * @mod: module to patch | |
192 | * | |
193 | * Allow for run-time selection of the optimal nops. Before the module | |
194 | * loads patch these with arch_get_jump_label_nop(), which is specified by | |
195 | * the arch specific jump label code. | |
196 | */ | |
197 | void jump_label_apply_nops(struct module *mod) | |
bf5438fc | 198 | { |
d430d3d7 JB |
199 | struct jump_entry *iter_start = mod->jump_entries; |
200 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
201 | struct jump_entry *iter; | |
202 | ||
203 | /* if the module doesn't have jump label entries, just return */ | |
204 | if (iter_start == iter_stop) | |
205 | return; | |
206 | ||
207 | for (iter = iter_start; iter < iter_stop; iter++) | |
208 | arch_jump_label_text_poke_early(iter->code); | |
bf5438fc JB |
209 | } |
210 | ||
d430d3d7 | 211 | static int jump_label_add_module(struct module *mod) |
bf5438fc | 212 | { |
d430d3d7 JB |
213 | struct jump_entry *iter_start = mod->jump_entries; |
214 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
215 | struct jump_entry *iter; | |
216 | struct jump_label_key *key = NULL; | |
217 | struct jump_label_mod *jlm; | |
bf5438fc JB |
218 | |
219 | /* if the module doesn't have jump label entries, just return */ | |
d430d3d7 | 220 | if (iter_start == iter_stop) |
bf5438fc JB |
221 | return 0; |
222 | ||
d430d3d7 JB |
223 | jump_label_sort_entries(iter_start, iter_stop); |
224 | ||
225 | for (iter = iter_start; iter < iter_stop; iter++) { | |
226 | if (iter->key == (jump_label_t)(unsigned long)key) | |
227 | continue; | |
228 | ||
229 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
230 | ||
231 | if (__module_address(iter->key) == mod) { | |
232 | atomic_set(&key->enabled, 0); | |
233 | key->entries = iter; | |
234 | key->next = NULL; | |
235 | continue; | |
bf5438fc | 236 | } |
d430d3d7 JB |
237 | |
238 | jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL); | |
239 | if (!jlm) | |
240 | return -ENOMEM; | |
241 | ||
242 | jlm->mod = mod; | |
243 | jlm->entries = iter; | |
244 | jlm->next = key->next; | |
245 | key->next = jlm; | |
246 | ||
247 | if (jump_label_enabled(key)) | |
248 | __jump_label_update(key, iter, JUMP_LABEL_ENABLE); | |
bf5438fc | 249 | } |
d430d3d7 | 250 | |
bf5438fc JB |
251 | return 0; |
252 | } | |
253 | ||
d430d3d7 | 254 | static void jump_label_del_module(struct module *mod) |
bf5438fc | 255 | { |
d430d3d7 JB |
256 | struct jump_entry *iter_start = mod->jump_entries; |
257 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
258 | struct jump_entry *iter; | |
259 | struct jump_label_key *key = NULL; | |
260 | struct jump_label_mod *jlm, **prev; | |
bf5438fc | 261 | |
d430d3d7 JB |
262 | for (iter = iter_start; iter < iter_stop; iter++) { |
263 | if (iter->key == (jump_label_t)(unsigned long)key) | |
264 | continue; | |
265 | ||
266 | key = (struct jump_label_key *)(unsigned long)iter->key; | |
267 | ||
268 | if (__module_address(iter->key) == mod) | |
269 | continue; | |
270 | ||
271 | prev = &key->next; | |
272 | jlm = key->next; | |
bf5438fc | 273 | |
d430d3d7 JB |
274 | while (jlm && jlm->mod != mod) { |
275 | prev = &jlm->next; | |
276 | jlm = jlm->next; | |
277 | } | |
278 | ||
279 | if (jlm) { | |
280 | *prev = jlm->next; | |
281 | kfree(jlm); | |
bf5438fc JB |
282 | } |
283 | } | |
284 | } | |
285 | ||
d430d3d7 | 286 | static void jump_label_invalidate_module_init(struct module *mod) |
b842f8fa | 287 | { |
d430d3d7 JB |
288 | struct jump_entry *iter_start = mod->jump_entries; |
289 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; | |
b842f8fa | 290 | struct jump_entry *iter; |
b842f8fa | 291 | |
d430d3d7 JB |
292 | for (iter = iter_start; iter < iter_stop; iter++) { |
293 | if (within_module_init(iter->code, mod)) | |
294 | iter->code = 0; | |
b842f8fa JB |
295 | } |
296 | } | |
297 | ||
bf5438fc JB |
298 | static int |
299 | jump_label_module_notify(struct notifier_block *self, unsigned long val, | |
300 | void *data) | |
301 | { | |
302 | struct module *mod = data; | |
303 | int ret = 0; | |
304 | ||
305 | switch (val) { | |
306 | case MODULE_STATE_COMING: | |
91bad2f8 | 307 | jump_label_lock(); |
d430d3d7 | 308 | ret = jump_label_add_module(mod); |
bf5438fc | 309 | if (ret) |
d430d3d7 | 310 | jump_label_del_module(mod); |
91bad2f8 | 311 | jump_label_unlock(); |
bf5438fc JB |
312 | break; |
313 | case MODULE_STATE_GOING: | |
91bad2f8 | 314 | jump_label_lock(); |
d430d3d7 | 315 | jump_label_del_module(mod); |
91bad2f8 | 316 | jump_label_unlock(); |
bf5438fc | 317 | break; |
b842f8fa | 318 | case MODULE_STATE_LIVE: |
91bad2f8 | 319 | jump_label_lock(); |
d430d3d7 | 320 | jump_label_invalidate_module_init(mod); |
91bad2f8 | 321 | jump_label_unlock(); |
b842f8fa | 322 | break; |
bf5438fc | 323 | } |
bf5438fc | 324 | |
d430d3d7 | 325 | return notifier_from_errno(ret); |
bf5438fc JB |
326 | } |
327 | ||
328 | struct notifier_block jump_label_module_nb = { | |
329 | .notifier_call = jump_label_module_notify, | |
d430d3d7 | 330 | .priority = 1, /* higher than tracepoints */ |
bf5438fc JB |
331 | }; |
332 | ||
d430d3d7 | 333 | static __init int jump_label_init_module(void) |
bf5438fc JB |
334 | { |
335 | return register_module_notifier(&jump_label_module_nb); | |
336 | } | |
d430d3d7 | 337 | early_initcall(jump_label_init_module); |
bf5438fc JB |
338 | |
339 | #endif /* CONFIG_MODULES */ | |
340 | ||
d430d3d7 JB |
341 | /*** |
342 | * jump_label_text_reserved - check if addr range is reserved | |
343 | * @start: start text addr | |
344 | * @end: end text addr | |
345 | * | |
346 | * checks if the text addr located between @start and @end | |
347 | * overlaps with any of the jump label patch addresses. Code | |
348 | * that wants to modify kernel text should first verify that | |
349 | * it does not overlap with any of the jump label addresses. | |
350 | * Caller must hold jump_label_mutex. | |
351 | * | |
352 | * returns 1 if there is an overlap, 0 otherwise | |
353 | */ | |
354 | int jump_label_text_reserved(void *start, void *end) | |
355 | { | |
356 | int ret = __jump_label_text_reserved(__start___jump_table, | |
357 | __stop___jump_table, start, end); | |
358 | ||
359 | if (ret) | |
360 | return ret; | |
361 | ||
362 | #ifdef CONFIG_MODULES | |
363 | ret = __jump_label_mod_text_reserved(start, end); | |
364 | #endif | |
365 | return ret; | |
366 | } | |
367 | ||
368 | static void jump_label_update(struct jump_label_key *key, int enable) | |
369 | { | |
370 | struct jump_entry *entry = key->entries; | |
371 | ||
372 | /* if there are no users, entry can be NULL */ | |
373 | if (entry) | |
374 | __jump_label_update(key, entry, enable); | |
375 | ||
376 | #ifdef CONFIG_MODULES | |
377 | __jump_label_mod_update(key, enable); | |
378 | #endif | |
379 | } | |
380 | ||
bf5438fc | 381 | #endif |