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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
13extern struct static_call_site __start_static_call_sites[],
14 __stop_static_call_sites[];
15extern struct static_call_tramp_key __start_static_call_tramp_key[],
16 __stop_static_call_tramp_key[];
17
18static bool static_call_initialized;
19
20/* mutex to protect key modules/sites */
21static DEFINE_MUTEX(static_call_mutex);
22
23static void static_call_lock(void)
24{
25 mutex_lock(&static_call_mutex);
26}
27
28static void static_call_unlock(void)
29{
30 mutex_unlock(&static_call_mutex);
31}
32
33static inline void *static_call_addr(struct static_call_site *site)
34{
35 return (void *)((long)site->addr + (long)&site->addr);
36}
37
38static inline unsigned long __static_call_key(const struct static_call_site *site)
39{
40 return (long)site->key + (long)&site->key;
41}
42
43static 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. */
49static inline bool static_call_is_init(struct static_call_site *site)
50{
51 return __static_call_key(site) & STATIC_CALL_SITE_INIT;
52}
53
54static inline bool static_call_is_tail(struct static_call_site *site)
55{
56 return __static_call_key(site) & STATIC_CALL_SITE_TAIL;
57}
58
59static 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
65static 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
81static 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
95static 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
102static inline bool static_call_key_has_mods(struct static_call_key *key)
103{
104 return !(key->type & 1);
105}
106
107static 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
115static 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
123void __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
203done:
204 static_call_unlock();
205 cpus_read_unlock();
206}
207EXPORT_SYMBOL_GPL(__static_call_update);
208
209static 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
274do_transform:
275 arch_static_call_transform(site_addr, NULL, key->func,
276 static_call_is_tail(site));
277 }
278
279 return 0;
280}
281
282static 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
293static 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
312static 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
336static 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
353static 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
392static 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
421static 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
449static struct notifier_block static_call_module_nb = {
450 .notifier_call = static_call_module_notify,
451};
452
453#else
454
455static inline int __static_call_mod_text_reserved(void *start, void *end)
456{
457 return 0;
458}
459
460#endif /* CONFIG_MODULES */
461
462int 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
474int __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}
500early_initcall(static_call_init);
501
502long __static_call_return0(void)
503{
504 return 0;
505}
506
507#ifdef CONFIG_STATIC_CALL_SELFTEST
508
509static int func_a(int x)
510{
511 return x+1;
512}
513
514static int func_b(int x)
515{
516 return x+2;
517}
518
519DEFINE_STATIC_CALL(sc_selftest, func_a);
520
521static struct static_call_data {
522 int (*func)(int);
523 int val;
524 int expect;
525} static_call_data [] __initdata = {
526 { NULL, 2, 3 },
527 { func_b, 2, 4 },
528 { func_a, 2, 3 }
529};
530
531static int __init test_static_call_init(void)
532{
533 int i;
534
535 for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
536 struct static_call_data *scd = &static_call_data[i];
537
538 if (scd->func)
539 static_call_update(sc_selftest, scd->func);
540
541 WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
542 }
543
544 return 0;
545}
546early_initcall(test_static_call_init);
547
548#endif /* CONFIG_STATIC_CALL_SELFTEST */