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