1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/init.h>
3 #include <linux/static_call.h>
6 #include <linux/sort.h>
7 #include <linux/slab.h>
8 #include <linux/module.h>
10 #include <linux/processor.h>
11 #include <asm/sections.h>
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[];
18 static bool static_call_initialized;
20 /* mutex to protect key modules/sites */
21 static DEFINE_MUTEX(static_call_mutex);
23 static void static_call_lock(void)
25 mutex_lock(&static_call_mutex);
28 static void static_call_unlock(void)
30 mutex_unlock(&static_call_mutex);
33 static inline void *static_call_addr(struct static_call_site *site)
35 return (void *)((long)site->addr + (long)&site->addr);
38 static inline unsigned long __static_call_key(const struct static_call_site *site)
40 return (long)site->key + (long)&site->key;
43 static inline struct static_call_key *static_call_key(const struct static_call_site *site)
45 return (void *)(__static_call_key(site) & ~STATIC_CALL_SITE_FLAGS);
48 /* These assume the key is word-aligned. */
49 static inline bool static_call_is_init(struct static_call_site *site)
51 return __static_call_key(site) & STATIC_CALL_SITE_INIT;
54 static inline bool static_call_is_tail(struct static_call_site *site)
56 return __static_call_key(site) & STATIC_CALL_SITE_TAIL;
59 static inline void static_call_set_init(struct static_call_site *site)
61 site->key = (__static_call_key(site) | STATIC_CALL_SITE_INIT) -
65 static int static_call_site_cmp(const void *_a, const void *_b)
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);
81 static void static_call_site_swap(void *_a, void *_b, int size)
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;
88 a->addr = b->addr - delta;
89 a->key = b->key - delta;
91 b->addr = tmp.addr + delta;
92 b->key = tmp.key + delta;
95 static inline void static_call_sort_entries(struct static_call_site *start,
96 struct static_call_site *stop)
98 sort(start, stop - start, sizeof(struct static_call_site),
99 static_call_site_cmp, static_call_site_swap);
102 static inline bool static_call_key_has_mods(struct static_call_key *key)
104 return !(key->type & 1);
107 static inline struct static_call_mod *static_call_key_next(struct static_call_key *key)
109 if (!static_call_key_has_mods(key))
115 static inline struct static_call_site *static_call_key_sites(struct static_call_key *key)
117 if (static_call_key_has_mods(key))
120 return (struct static_call_site *)(key->type & ~1);
123 void __static_call_update(struct static_call_key *key, void *tramp, void *func)
125 struct static_call_site *site, *stop;
126 struct static_call_mod *site_mod, first;
131 if (key->func == func)
136 arch_static_call_transform(NULL, tramp, func, false);
139 * If uninitialized, we'll not update the callsites, but they still
140 * point to the trampoline and we just patched that.
142 if (WARN_ON_ONCE(!static_call_initialized))
145 first = (struct static_call_mod){
146 .next = static_call_key_next(key),
148 .sites = static_call_key_sites(key),
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;
155 if (!site_mod->sites) {
157 * This can happen if the static call key is defined in
158 * a module which doesn't use it.
160 * It also happens in the has_mods case, where the
161 * 'first' entry has no sites associated with it.
166 stop = __stop_static_call_sites;
169 #ifdef CONFIG_MODULES
170 stop = mod->static_call_sites +
171 mod->num_static_call_sites;
172 init = mod->state == MODULE_STATE_COMING;
176 for (site = site_mod->sites;
177 site < stop && static_call_key(site) == key; site++) {
178 void *site_addr = static_call_addr(site);
180 if (!init && static_call_is_init(site))
183 if (!kernel_text_address((unsigned long)site_addr)) {
185 * This skips patching built-in __exit, which
186 * is part of init_section_contains() but is
187 * not part of kernel_text_address().
189 * Skipping built-in __exit is fine since it
190 * will never be executed.
192 WARN_ONCE(!static_call_is_init(site),
193 "can't patch static call site at %pS",
198 arch_static_call_transform(site_addr, NULL, func,
199 static_call_is_tail(site));
204 static_call_unlock();
207 EXPORT_SYMBOL_GPL(__static_call_update);
209 static int __static_call_init(struct module *mod,
210 struct static_call_site *start,
211 struct static_call_site *stop)
213 struct static_call_site *site;
214 struct static_call_key *key, *prev_key = NULL;
215 struct static_call_mod *site_mod;
220 static_call_sort_entries(start, stop);
222 for (site = start; site < stop; site++) {
223 void *site_addr = static_call_addr(site);
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);
229 key = static_call_key(site);
230 if (key != prev_key) {
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.
238 * This allows architectures (eg. x86) to call
239 * static_call_init() before memory allocation works.
247 site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
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.
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);
261 key->mods = site_mod;
263 site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
269 site_mod->sites = site;
270 site_mod->next = static_call_key_next(key);
271 key->mods = site_mod;
275 arch_static_call_transform(site_addr, NULL, key->func,
276 static_call_is_tail(site));
282 static int addr_conflict(struct static_call_site *site, void *start, void *end)
284 unsigned long addr = (unsigned long)static_call_addr(site);
286 if (addr <= (unsigned long)end &&
287 addr + CALL_INSN_SIZE > (unsigned long)start)
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)
297 struct static_call_site *iter = iter_start;
299 while (iter < iter_stop) {
300 if (init || !static_call_is_init(iter)) {
301 if (addr_conflict(iter, start, end))
310 #ifdef CONFIG_MODULES
312 static int __static_call_mod_text_reserved(void *start, void *end)
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))
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);
336 static unsigned long tramp_key_lookup(unsigned long addr)
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;
342 for (tramp_key = start; tramp_key != stop; tramp_key++) {
345 tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp;
347 return (long)tramp_key->key + (long)&tramp_key->key;
353 static int static_call_add_module(struct module *mod)
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;
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;
365 * Is the key is exported, 'addr' points to the key, which
366 * means modules are allowed to call static_call_update() on
369 * Otherwise, the key isn't exported, and 'addr' points to the
370 * trampoline so we need to lookup the key.
372 * We go through this dance to prevent crazy modules from
373 * abusing sensitive static calls.
375 if (!kernel_text_address(addr))
378 key = tramp_key_lookup(addr);
380 pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n",
381 static_call_addr(site));
385 key |= s_key & STATIC_CALL_SITE_FLAGS;
386 site->key = key - (long)&site->key;
389 return __static_call_init(mod, start, stop);
392 static void static_call_del_module(struct module *mod)
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;
401 for (site = start; site < stop; site++) {
402 key = static_call_key(site);
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)
416 *prev = site_mod->next;
421 static int static_call_module_notify(struct notifier_block *nb,
422 unsigned long val, void *data)
424 struct module *mod = data;
431 case MODULE_STATE_COMING:
432 ret = static_call_add_module(mod);
434 WARN(1, "Failed to allocate memory for static calls");
435 static_call_del_module(mod);
438 case MODULE_STATE_GOING:
439 static_call_del_module(mod);
443 static_call_unlock();
446 return notifier_from_errno(ret);
449 static struct notifier_block static_call_module_nb = {
450 .notifier_call = static_call_module_notify,
455 static inline int __static_call_mod_text_reserved(void *start, void *end)
460 #endif /* CONFIG_MODULES */
462 int static_call_text_reserved(void *start, void *end)
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);
471 return __static_call_mod_text_reserved(start, end);
474 int __init static_call_init(void)
478 if (static_call_initialized)
483 ret = __static_call_init(NULL, __start_static_call_sites,
484 __stop_static_call_sites);
485 static_call_unlock();
489 pr_err("Failed to allocate memory for static_call!\n");
493 static_call_initialized = true;
495 #ifdef CONFIG_MODULES
496 register_module_notifier(&static_call_module_nb);
500 early_initcall(static_call_init);
502 long __static_call_return0(void)
507 #ifdef CONFIG_STATIC_CALL_SELFTEST
509 static int func_a(int x)
514 static int func_b(int x)
519 DEFINE_STATIC_CALL(sc_selftest, func_a);
521 static struct static_call_data {
525 } static_call_data [] __initdata = {
531 static int __init test_static_call_init(void)
535 for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
536 struct static_call_data *scd = &static_call_data[i];
539 static_call_update(sc_selftest, scd->func);
541 WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
546 early_initcall(test_static_call_init);
548 #endif /* CONFIG_STATIC_CALL_SELFTEST */