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1 | // SPDX-License-Identifier: GPL-2.0 |
2 | #include <linux/init.h> | |
3 | #include <linux/static_call.h> | |
4 | #include <linux/bug.h> | |
5 | #include <linux/smp.h> | |
6 | #include <linux/sort.h> | |
7 | #include <linux/slab.h> | |
8 | #include <linux/module.h> | |
9 | #include <linux/cpu.h> | |
10 | #include <linux/processor.h> | |
11 | #include <asm/sections.h> | |
12 | ||
13 | extern struct static_call_site __start_static_call_sites[], | |
14 | __stop_static_call_sites[]; | |
15 | extern struct static_call_tramp_key __start_static_call_tramp_key[], | |
16 | __stop_static_call_tramp_key[]; | |
17 | ||
18 | static bool static_call_initialized; | |
19 | ||
20 | /* mutex to protect key modules/sites */ | |
21 | static DEFINE_MUTEX(static_call_mutex); | |
22 | ||
23 | static void static_call_lock(void) | |
24 | { | |
25 | mutex_lock(&static_call_mutex); | |
26 | } | |
27 | ||
28 | static void static_call_unlock(void) | |
29 | { | |
30 | mutex_unlock(&static_call_mutex); | |
31 | } | |
32 | ||
33 | static inline void *static_call_addr(struct static_call_site *site) | |
34 | { | |
35 | return (void *)((long)site->addr + (long)&site->addr); | |
36 | } | |
37 | ||
38 | static inline unsigned long __static_call_key(const struct static_call_site *site) | |
39 | { | |
40 | return (long)site->key + (long)&site->key; | |
41 | } | |
42 | ||
43 | static inline struct static_call_key *static_call_key(const struct static_call_site *site) | |
44 | { | |
45 | return (void *)(__static_call_key(site) & ~STATIC_CALL_SITE_FLAGS); | |
46 | } | |
47 | ||
48 | /* These assume the key is word-aligned. */ | |
49 | static inline bool static_call_is_init(struct static_call_site *site) | |
50 | { | |
51 | return __static_call_key(site) & STATIC_CALL_SITE_INIT; | |
52 | } | |
53 | ||
54 | static inline bool static_call_is_tail(struct static_call_site *site) | |
55 | { | |
56 | return __static_call_key(site) & STATIC_CALL_SITE_TAIL; | |
57 | } | |
58 | ||
59 | static inline void static_call_set_init(struct static_call_site *site) | |
60 | { | |
61 | site->key = (__static_call_key(site) | STATIC_CALL_SITE_INIT) - | |
62 | (long)&site->key; | |
63 | } | |
64 | ||
65 | static int static_call_site_cmp(const void *_a, const void *_b) | |
66 | { | |
67 | const struct static_call_site *a = _a; | |
68 | const struct static_call_site *b = _b; | |
69 | const struct static_call_key *key_a = static_call_key(a); | |
70 | const struct static_call_key *key_b = static_call_key(b); | |
71 | ||
72 | if (key_a < key_b) | |
73 | return -1; | |
74 | ||
75 | if (key_a > key_b) | |
76 | return 1; | |
77 | ||
78 | return 0; | |
79 | } | |
80 | ||
81 | static void static_call_site_swap(void *_a, void *_b, int size) | |
82 | { | |
83 | long delta = (unsigned long)_a - (unsigned long)_b; | |
84 | struct static_call_site *a = _a; | |
85 | struct static_call_site *b = _b; | |
86 | struct static_call_site tmp = *a; | |
87 | ||
88 | a->addr = b->addr - delta; | |
89 | a->key = b->key - delta; | |
90 | ||
91 | b->addr = tmp.addr + delta; | |
92 | b->key = tmp.key + delta; | |
93 | } | |
94 | ||
95 | static inline void static_call_sort_entries(struct static_call_site *start, | |
96 | struct static_call_site *stop) | |
97 | { | |
98 | sort(start, stop - start, sizeof(struct static_call_site), | |
99 | static_call_site_cmp, static_call_site_swap); | |
100 | } | |
101 | ||
102 | static inline bool static_call_key_has_mods(struct static_call_key *key) | |
103 | { | |
104 | return !(key->type & 1); | |
105 | } | |
106 | ||
107 | static inline struct static_call_mod *static_call_key_next(struct static_call_key *key) | |
108 | { | |
109 | if (!static_call_key_has_mods(key)) | |
110 | return NULL; | |
111 | ||
112 | return key->mods; | |
113 | } | |
114 | ||
115 | static inline struct static_call_site *static_call_key_sites(struct static_call_key *key) | |
116 | { | |
117 | if (static_call_key_has_mods(key)) | |
118 | return NULL; | |
119 | ||
120 | return (struct static_call_site *)(key->type & ~1); | |
121 | } | |
122 | ||
123 | void __static_call_update(struct static_call_key *key, void *tramp, void *func) | |
124 | { | |
125 | struct static_call_site *site, *stop; | |
126 | struct static_call_mod *site_mod, first; | |
127 | ||
128 | cpus_read_lock(); | |
129 | static_call_lock(); | |
130 | ||
131 | if (key->func == func) | |
132 | goto done; | |
133 | ||
134 | key->func = func; | |
135 | ||
136 | arch_static_call_transform(NULL, tramp, func, false); | |
137 | ||
138 | /* | |
139 | * If uninitialized, we'll not update the callsites, but they still | |
140 | * point to the trampoline and we just patched that. | |
141 | */ | |
142 | if (WARN_ON_ONCE(!static_call_initialized)) | |
143 | goto done; | |
144 | ||
145 | first = (struct static_call_mod){ | |
146 | .next = static_call_key_next(key), | |
147 | .mod = NULL, | |
148 | .sites = static_call_key_sites(key), | |
149 | }; | |
150 | ||
151 | for (site_mod = &first; site_mod; site_mod = site_mod->next) { | |
152 | bool init = system_state < SYSTEM_RUNNING; | |
153 | struct module *mod = site_mod->mod; | |
154 | ||
155 | if (!site_mod->sites) { | |
156 | /* | |
157 | * This can happen if the static call key is defined in | |
158 | * a module which doesn't use it. | |
159 | * | |
160 | * It also happens in the has_mods case, where the | |
161 | * 'first' entry has no sites associated with it. | |
162 | */ | |
163 | continue; | |
164 | } | |
165 | ||
166 | stop = __stop_static_call_sites; | |
167 | ||
168 | if (mod) { | |
169 | #ifdef CONFIG_MODULES | |
170 | stop = mod->static_call_sites + | |
171 | mod->num_static_call_sites; | |
172 | init = mod->state == MODULE_STATE_COMING; | |
173 | #endif | |
174 | } | |
175 | ||
176 | for (site = site_mod->sites; | |
177 | site < stop && static_call_key(site) == key; site++) { | |
178 | void *site_addr = static_call_addr(site); | |
179 | ||
180 | if (!init && static_call_is_init(site)) | |
181 | continue; | |
182 | ||
183 | if (!kernel_text_address((unsigned long)site_addr)) { | |
184 | /* | |
185 | * This skips patching built-in __exit, which | |
186 | * is part of init_section_contains() but is | |
187 | * not part of kernel_text_address(). | |
188 | * | |
189 | * Skipping built-in __exit is fine since it | |
190 | * will never be executed. | |
191 | */ | |
192 | WARN_ONCE(!static_call_is_init(site), | |
193 | "can't patch static call site at %pS", | |
194 | site_addr); | |
195 | continue; | |
196 | } | |
197 | ||
198 | arch_static_call_transform(site_addr, NULL, func, | |
199 | static_call_is_tail(site)); | |
200 | } | |
201 | } | |
202 | ||
203 | done: | |
204 | static_call_unlock(); | |
205 | cpus_read_unlock(); | |
206 | } | |
207 | EXPORT_SYMBOL_GPL(__static_call_update); | |
208 | ||
209 | static int __static_call_init(struct module *mod, | |
210 | struct static_call_site *start, | |
211 | struct static_call_site *stop) | |
212 | { | |
213 | struct static_call_site *site; | |
214 | struct static_call_key *key, *prev_key = NULL; | |
215 | struct static_call_mod *site_mod; | |
216 | ||
217 | if (start == stop) | |
218 | return 0; | |
219 | ||
220 | static_call_sort_entries(start, stop); | |
221 | ||
222 | for (site = start; site < stop; site++) { | |
223 | void *site_addr = static_call_addr(site); | |
224 | ||
225 | if ((mod && within_module_init((unsigned long)site_addr, mod)) || | |
226 | (!mod && init_section_contains(site_addr, 1))) | |
227 | static_call_set_init(site); | |
228 | ||
229 | key = static_call_key(site); | |
230 | if (key != prev_key) { | |
231 | prev_key = key; | |
232 | ||
233 | /* | |
234 | * For vmlinux (!mod) avoid the allocation by storing | |
235 | * the sites pointer in the key itself. Also see | |
236 | * __static_call_update()'s @first. | |
237 | * | |
238 | * This allows architectures (eg. x86) to call | |
239 | * static_call_init() before memory allocation works. | |
240 | */ | |
241 | if (!mod) { | |
242 | key->sites = site; | |
243 | key->type |= 1; | |
244 | goto do_transform; | |
245 | } | |
246 | ||
247 | site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL); | |
248 | if (!site_mod) | |
249 | return -ENOMEM; | |
250 | ||
251 | /* | |
252 | * When the key has a direct sites pointer, extract | |
253 | * that into an explicit struct static_call_mod, so we | |
254 | * can have a list of modules. | |
255 | */ | |
256 | if (static_call_key_sites(key)) { | |
257 | site_mod->mod = NULL; | |
258 | site_mod->next = NULL; | |
259 | site_mod->sites = static_call_key_sites(key); | |
260 | ||
261 | key->mods = site_mod; | |
262 | ||
263 | site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL); | |
264 | if (!site_mod) | |
265 | return -ENOMEM; | |
266 | } | |
267 | ||
268 | site_mod->mod = mod; | |
269 | site_mod->sites = site; | |
270 | site_mod->next = static_call_key_next(key); | |
271 | key->mods = site_mod; | |
272 | } | |
273 | ||
274 | do_transform: | |
275 | arch_static_call_transform(site_addr, NULL, key->func, | |
276 | static_call_is_tail(site)); | |
277 | } | |
278 | ||
279 | return 0; | |
280 | } | |
281 | ||
282 | static int addr_conflict(struct static_call_site *site, void *start, void *end) | |
283 | { | |
284 | unsigned long addr = (unsigned long)static_call_addr(site); | |
285 | ||
286 | if (addr <= (unsigned long)end && | |
287 | addr + CALL_INSN_SIZE > (unsigned long)start) | |
288 | return 1; | |
289 | ||
290 | return 0; | |
291 | } | |
292 | ||
293 | static int __static_call_text_reserved(struct static_call_site *iter_start, | |
294 | struct static_call_site *iter_stop, | |
295 | void *start, void *end, bool init) | |
296 | { | |
297 | struct static_call_site *iter = iter_start; | |
298 | ||
299 | while (iter < iter_stop) { | |
300 | if (init || !static_call_is_init(iter)) { | |
301 | if (addr_conflict(iter, start, end)) | |
302 | return 1; | |
303 | } | |
304 | iter++; | |
305 | } | |
306 | ||
307 | return 0; | |
308 | } | |
309 | ||
310 | #ifdef CONFIG_MODULES | |
311 | ||
312 | static int __static_call_mod_text_reserved(void *start, void *end) | |
313 | { | |
314 | struct module *mod; | |
315 | int ret; | |
316 | ||
317 | preempt_disable(); | |
318 | mod = __module_text_address((unsigned long)start); | |
319 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); | |
320 | if (!try_module_get(mod)) | |
321 | mod = NULL; | |
322 | preempt_enable(); | |
323 | ||
324 | if (!mod) | |
325 | return 0; | |
326 | ||
327 | ret = __static_call_text_reserved(mod->static_call_sites, | |
328 | mod->static_call_sites + mod->num_static_call_sites, | |
329 | start, end, mod->state == MODULE_STATE_COMING); | |
330 | ||
331 | module_put(mod); | |
332 | ||
333 | return ret; | |
334 | } | |
335 | ||
336 | static unsigned long tramp_key_lookup(unsigned long addr) | |
337 | { | |
338 | struct static_call_tramp_key *start = __start_static_call_tramp_key; | |
339 | struct static_call_tramp_key *stop = __stop_static_call_tramp_key; | |
340 | struct static_call_tramp_key *tramp_key; | |
341 | ||
342 | for (tramp_key = start; tramp_key != stop; tramp_key++) { | |
343 | unsigned long tramp; | |
344 | ||
345 | tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp; | |
346 | if (tramp == addr) | |
347 | return (long)tramp_key->key + (long)&tramp_key->key; | |
348 | } | |
349 | ||
350 | return 0; | |
351 | } | |
352 | ||
353 | static int static_call_add_module(struct module *mod) | |
354 | { | |
355 | struct static_call_site *start = mod->static_call_sites; | |
356 | struct static_call_site *stop = start + mod->num_static_call_sites; | |
357 | struct static_call_site *site; | |
358 | ||
359 | for (site = start; site != stop; site++) { | |
360 | unsigned long s_key = __static_call_key(site); | |
361 | unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS; | |
362 | unsigned long key; | |
363 | ||
364 | /* | |
365 | * Is the key is exported, 'addr' points to the key, which | |
366 | * means modules are allowed to call static_call_update() on | |
367 | * it. | |
368 | * | |
369 | * Otherwise, the key isn't exported, and 'addr' points to the | |
370 | * trampoline so we need to lookup the key. | |
371 | * | |
372 | * We go through this dance to prevent crazy modules from | |
373 | * abusing sensitive static calls. | |
374 | */ | |
375 | if (!kernel_text_address(addr)) | |
376 | continue; | |
377 | ||
378 | key = tramp_key_lookup(addr); | |
379 | if (!key) { | |
380 | pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n", | |
381 | static_call_addr(site)); | |
382 | return -EINVAL; | |
383 | } | |
384 | ||
385 | key |= s_key & STATIC_CALL_SITE_FLAGS; | |
386 | site->key = key - (long)&site->key; | |
387 | } | |
388 | ||
389 | return __static_call_init(mod, start, stop); | |
390 | } | |
391 | ||
392 | static void static_call_del_module(struct module *mod) | |
393 | { | |
394 | struct static_call_site *start = mod->static_call_sites; | |
395 | struct static_call_site *stop = mod->static_call_sites + | |
396 | mod->num_static_call_sites; | |
397 | struct static_call_key *key, *prev_key = NULL; | |
398 | struct static_call_mod *site_mod, **prev; | |
399 | struct static_call_site *site; | |
400 | ||
401 | for (site = start; site < stop; site++) { | |
402 | key = static_call_key(site); | |
403 | if (key == prev_key) | |
404 | continue; | |
405 | ||
406 | prev_key = key; | |
407 | ||
408 | for (prev = &key->mods, site_mod = key->mods; | |
409 | site_mod && site_mod->mod != mod; | |
410 | prev = &site_mod->next, site_mod = site_mod->next) | |
411 | ; | |
412 | ||
413 | if (!site_mod) | |
414 | continue; | |
415 | ||
416 | *prev = site_mod->next; | |
417 | kfree(site_mod); | |
418 | } | |
419 | } | |
420 | ||
421 | static int static_call_module_notify(struct notifier_block *nb, | |
422 | unsigned long val, void *data) | |
423 | { | |
424 | struct module *mod = data; | |
425 | int ret = 0; | |
426 | ||
427 | cpus_read_lock(); | |
428 | static_call_lock(); | |
429 | ||
430 | switch (val) { | |
431 | case MODULE_STATE_COMING: | |
432 | ret = static_call_add_module(mod); | |
433 | if (ret) { | |
434 | WARN(1, "Failed to allocate memory for static calls"); | |
435 | static_call_del_module(mod); | |
436 | } | |
437 | break; | |
438 | case MODULE_STATE_GOING: | |
439 | static_call_del_module(mod); | |
440 | break; | |
441 | } | |
442 | ||
443 | static_call_unlock(); | |
444 | cpus_read_unlock(); | |
445 | ||
446 | return notifier_from_errno(ret); | |
447 | } | |
448 | ||
449 | static struct notifier_block static_call_module_nb = { | |
450 | .notifier_call = static_call_module_notify, | |
451 | }; | |
452 | ||
453 | #else | |
454 | ||
455 | static inline int __static_call_mod_text_reserved(void *start, void *end) | |
456 | { | |
457 | return 0; | |
458 | } | |
459 | ||
460 | #endif /* CONFIG_MODULES */ | |
461 | ||
462 | int static_call_text_reserved(void *start, void *end) | |
463 | { | |
464 | bool init = system_state < SYSTEM_RUNNING; | |
465 | int ret = __static_call_text_reserved(__start_static_call_sites, | |
466 | __stop_static_call_sites, start, end, init); | |
467 | ||
468 | if (ret) | |
469 | return ret; | |
470 | ||
471 | return __static_call_mod_text_reserved(start, end); | |
472 | } | |
473 | ||
474 | int __init static_call_init(void) | |
475 | { | |
476 | int ret; | |
477 | ||
478 | if (static_call_initialized) | |
479 | return 0; | |
480 | ||
481 | cpus_read_lock(); | |
482 | static_call_lock(); | |
483 | ret = __static_call_init(NULL, __start_static_call_sites, | |
484 | __stop_static_call_sites); | |
485 | static_call_unlock(); | |
486 | cpus_read_unlock(); | |
487 | ||
488 | if (ret) { | |
489 | pr_err("Failed to allocate memory for static_call!\n"); | |
490 | BUG(); | |
491 | } | |
492 | ||
493 | static_call_initialized = true; | |
494 | ||
495 | #ifdef CONFIG_MODULES | |
496 | register_module_notifier(&static_call_module_nb); | |
497 | #endif | |
498 | return 0; | |
499 | } | |
500 | early_initcall(static_call_init); | |
501 | ||
502 | #ifdef CONFIG_STATIC_CALL_SELFTEST | |
503 | ||
504 | static int func_a(int x) | |
505 | { | |
506 | return x+1; | |
507 | } | |
508 | ||
509 | static int func_b(int x) | |
510 | { | |
511 | return x+2; | |
512 | } | |
513 | ||
514 | DEFINE_STATIC_CALL(sc_selftest, func_a); | |
515 | ||
516 | static struct static_call_data { | |
517 | int (*func)(int); | |
518 | int val; | |
519 | int expect; | |
520 | } static_call_data [] __initdata = { | |
521 | { NULL, 2, 3 }, | |
522 | { func_b, 2, 4 }, | |
523 | { func_a, 2, 3 } | |
524 | }; | |
525 | ||
526 | static int __init test_static_call_init(void) | |
527 | { | |
528 | int i; | |
529 | ||
530 | for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) { | |
531 | struct static_call_data *scd = &static_call_data[i]; | |
532 | ||
533 | if (scd->func) | |
534 | static_call_update(sc_selftest, scd->func); | |
535 | ||
536 | WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect); | |
537 | } | |
538 | ||
539 | return 0; | |
540 | } | |
541 | early_initcall(test_static_call_init); | |
542 | ||
543 | #endif /* CONFIG_STATIC_CALL_SELFTEST */ |