| 1 | /* |
| 2 | * jump label support |
| 3 | * |
| 4 | * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> |
| 5 | * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com> |
| 6 | * |
| 7 | */ |
| 8 | #include <linux/memory.h> |
| 9 | #include <linux/uaccess.h> |
| 10 | #include <linux/module.h> |
| 11 | #include <linux/list.h> |
| 12 | #include <linux/slab.h> |
| 13 | #include <linux/sort.h> |
| 14 | #include <linux/err.h> |
| 15 | #include <linux/static_key.h> |
| 16 | |
| 17 | #ifdef HAVE_JUMP_LABEL |
| 18 | |
| 19 | /* mutex to protect coming/going of the the jump_label table */ |
| 20 | static DEFINE_MUTEX(jump_label_mutex); |
| 21 | |
| 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 | |
| 32 | static int jump_label_cmp(const void *a, const void *b) |
| 33 | { |
| 34 | const struct jump_entry *jea = a; |
| 35 | const struct jump_entry *jeb = b; |
| 36 | |
| 37 | if (jea->key < jeb->key) |
| 38 | return -1; |
| 39 | |
| 40 | if (jea->key > jeb->key) |
| 41 | return 1; |
| 42 | |
| 43 | return 0; |
| 44 | } |
| 45 | |
| 46 | static void |
| 47 | jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) |
| 48 | { |
| 49 | unsigned long size; |
| 50 | |
| 51 | size = (((unsigned long)stop - (unsigned long)start) |
| 52 | / sizeof(struct jump_entry)); |
| 53 | sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL); |
| 54 | } |
| 55 | |
| 56 | static void jump_label_update(struct static_key *key, int enable); |
| 57 | |
| 58 | void static_key_slow_inc(struct static_key *key) |
| 59 | { |
| 60 | if (atomic_inc_not_zero(&key->enabled)) |
| 61 | return; |
| 62 | |
| 63 | jump_label_lock(); |
| 64 | if (atomic_read(&key->enabled) == 0) { |
| 65 | if (!jump_label_get_branch_default(key)) |
| 66 | jump_label_update(key, JUMP_LABEL_ENABLE); |
| 67 | else |
| 68 | jump_label_update(key, JUMP_LABEL_DISABLE); |
| 69 | } |
| 70 | atomic_inc(&key->enabled); |
| 71 | jump_label_unlock(); |
| 72 | } |
| 73 | EXPORT_SYMBOL_GPL(static_key_slow_inc); |
| 74 | |
| 75 | static void __static_key_slow_dec(struct static_key *key, |
| 76 | unsigned long rate_limit, struct delayed_work *work) |
| 77 | { |
| 78 | if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) { |
| 79 | WARN(atomic_read(&key->enabled) < 0, |
| 80 | "jump label: negative count!\n"); |
| 81 | return; |
| 82 | } |
| 83 | |
| 84 | if (rate_limit) { |
| 85 | atomic_inc(&key->enabled); |
| 86 | schedule_delayed_work(work, rate_limit); |
| 87 | } else { |
| 88 | if (!jump_label_get_branch_default(key)) |
| 89 | jump_label_update(key, JUMP_LABEL_DISABLE); |
| 90 | else |
| 91 | jump_label_update(key, JUMP_LABEL_ENABLE); |
| 92 | } |
| 93 | jump_label_unlock(); |
| 94 | } |
| 95 | |
| 96 | static void jump_label_update_timeout(struct work_struct *work) |
| 97 | { |
| 98 | struct static_key_deferred *key = |
| 99 | container_of(work, struct static_key_deferred, work.work); |
| 100 | __static_key_slow_dec(&key->key, 0, NULL); |
| 101 | } |
| 102 | |
| 103 | void static_key_slow_dec(struct static_key *key) |
| 104 | { |
| 105 | __static_key_slow_dec(key, 0, NULL); |
| 106 | } |
| 107 | EXPORT_SYMBOL_GPL(static_key_slow_dec); |
| 108 | |
| 109 | void static_key_slow_dec_deferred(struct static_key_deferred *key) |
| 110 | { |
| 111 | __static_key_slow_dec(&key->key, key->timeout, &key->work); |
| 112 | } |
| 113 | EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred); |
| 114 | |
| 115 | void jump_label_rate_limit(struct static_key_deferred *key, |
| 116 | unsigned long rl) |
| 117 | { |
| 118 | key->timeout = rl; |
| 119 | INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); |
| 120 | } |
| 121 | |
| 122 | static int addr_conflict(struct jump_entry *entry, void *start, void *end) |
| 123 | { |
| 124 | if (entry->code <= (unsigned long)end && |
| 125 | entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start) |
| 126 | return 1; |
| 127 | |
| 128 | return 0; |
| 129 | } |
| 130 | |
| 131 | static int __jump_label_text_reserved(struct jump_entry *iter_start, |
| 132 | struct jump_entry *iter_stop, void *start, void *end) |
| 133 | { |
| 134 | struct jump_entry *iter; |
| 135 | |
| 136 | iter = iter_start; |
| 137 | while (iter < iter_stop) { |
| 138 | if (addr_conflict(iter, start, end)) |
| 139 | return 1; |
| 140 | iter++; |
| 141 | } |
| 142 | |
| 143 | return 0; |
| 144 | } |
| 145 | |
| 146 | /* |
| 147 | * Update code which is definitely not currently executing. |
| 148 | * Architectures which need heavyweight synchronization to modify |
| 149 | * running code can override this to make the non-live update case |
| 150 | * cheaper. |
| 151 | */ |
| 152 | void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, |
| 153 | enum jump_label_type type) |
| 154 | { |
| 155 | arch_jump_label_transform(entry, type); |
| 156 | } |
| 157 | |
| 158 | static void __jump_label_update(struct static_key *key, |
| 159 | struct jump_entry *entry, |
| 160 | struct jump_entry *stop, int enable) |
| 161 | { |
| 162 | for (; (entry < stop) && |
| 163 | (entry->key == (jump_label_t)(unsigned long)key); |
| 164 | entry++) { |
| 165 | /* |
| 166 | * entry->code set to 0 invalidates module init text sections |
| 167 | * kernel_text_address() verifies we are not in core kernel |
| 168 | * init code, see jump_label_invalidate_module_init(). |
| 169 | */ |
| 170 | if (entry->code && kernel_text_address(entry->code)) |
| 171 | arch_jump_label_transform(entry, enable); |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | static enum jump_label_type jump_label_type(struct static_key *key) |
| 176 | { |
| 177 | bool true_branch = jump_label_get_branch_default(key); |
| 178 | bool state = static_key_enabled(key); |
| 179 | |
| 180 | if ((!true_branch && state) || (true_branch && !state)) |
| 181 | return JUMP_LABEL_ENABLE; |
| 182 | |
| 183 | return JUMP_LABEL_DISABLE; |
| 184 | } |
| 185 | |
| 186 | void __init jump_label_init(void) |
| 187 | { |
| 188 | struct jump_entry *iter_start = __start___jump_table; |
| 189 | struct jump_entry *iter_stop = __stop___jump_table; |
| 190 | struct static_key *key = NULL; |
| 191 | struct jump_entry *iter; |
| 192 | |
| 193 | jump_label_lock(); |
| 194 | jump_label_sort_entries(iter_start, iter_stop); |
| 195 | |
| 196 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 197 | struct static_key *iterk; |
| 198 | |
| 199 | iterk = (struct static_key *)(unsigned long)iter->key; |
| 200 | arch_jump_label_transform_static(iter, jump_label_type(iterk)); |
| 201 | if (iterk == key) |
| 202 | continue; |
| 203 | |
| 204 | key = iterk; |
| 205 | /* |
| 206 | * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. |
| 207 | */ |
| 208 | *((unsigned long *)&key->entries) += (unsigned long)iter; |
| 209 | #ifdef CONFIG_MODULES |
| 210 | key->next = NULL; |
| 211 | #endif |
| 212 | } |
| 213 | jump_label_unlock(); |
| 214 | } |
| 215 | |
| 216 | #ifdef CONFIG_MODULES |
| 217 | |
| 218 | struct static_key_mod { |
| 219 | struct static_key_mod *next; |
| 220 | struct jump_entry *entries; |
| 221 | struct module *mod; |
| 222 | }; |
| 223 | |
| 224 | static int __jump_label_mod_text_reserved(void *start, void *end) |
| 225 | { |
| 226 | struct module *mod; |
| 227 | |
| 228 | mod = __module_text_address((unsigned long)start); |
| 229 | if (!mod) |
| 230 | return 0; |
| 231 | |
| 232 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); |
| 233 | |
| 234 | return __jump_label_text_reserved(mod->jump_entries, |
| 235 | mod->jump_entries + mod->num_jump_entries, |
| 236 | start, end); |
| 237 | } |
| 238 | |
| 239 | static void __jump_label_mod_update(struct static_key *key, int enable) |
| 240 | { |
| 241 | struct static_key_mod *mod = key->next; |
| 242 | |
| 243 | while (mod) { |
| 244 | struct module *m = mod->mod; |
| 245 | |
| 246 | __jump_label_update(key, mod->entries, |
| 247 | m->jump_entries + m->num_jump_entries, |
| 248 | enable); |
| 249 | mod = mod->next; |
| 250 | } |
| 251 | } |
| 252 | |
| 253 | /*** |
| 254 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() |
| 255 | * @mod: module to patch |
| 256 | * |
| 257 | * Allow for run-time selection of the optimal nops. Before the module |
| 258 | * loads patch these with arch_get_jump_label_nop(), which is specified by |
| 259 | * the arch specific jump label code. |
| 260 | */ |
| 261 | void jump_label_apply_nops(struct module *mod) |
| 262 | { |
| 263 | struct jump_entry *iter_start = mod->jump_entries; |
| 264 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 265 | struct jump_entry *iter; |
| 266 | |
| 267 | /* if the module doesn't have jump label entries, just return */ |
| 268 | if (iter_start == iter_stop) |
| 269 | return; |
| 270 | |
| 271 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 272 | arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE); |
| 273 | } |
| 274 | } |
| 275 | |
| 276 | static int jump_label_add_module(struct module *mod) |
| 277 | { |
| 278 | struct jump_entry *iter_start = mod->jump_entries; |
| 279 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 280 | struct jump_entry *iter; |
| 281 | struct static_key *key = NULL; |
| 282 | struct static_key_mod *jlm; |
| 283 | |
| 284 | /* if the module doesn't have jump label entries, just return */ |
| 285 | if (iter_start == iter_stop) |
| 286 | return 0; |
| 287 | |
| 288 | jump_label_sort_entries(iter_start, iter_stop); |
| 289 | |
| 290 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 291 | struct static_key *iterk; |
| 292 | |
| 293 | iterk = (struct static_key *)(unsigned long)iter->key; |
| 294 | if (iterk == key) |
| 295 | continue; |
| 296 | |
| 297 | key = iterk; |
| 298 | if (__module_address(iter->key) == mod) { |
| 299 | /* |
| 300 | * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. |
| 301 | */ |
| 302 | *((unsigned long *)&key->entries) += (unsigned long)iter; |
| 303 | key->next = NULL; |
| 304 | continue; |
| 305 | } |
| 306 | jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); |
| 307 | if (!jlm) |
| 308 | return -ENOMEM; |
| 309 | jlm->mod = mod; |
| 310 | jlm->entries = iter; |
| 311 | jlm->next = key->next; |
| 312 | key->next = jlm; |
| 313 | |
| 314 | if (jump_label_type(key) == JUMP_LABEL_ENABLE) |
| 315 | __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE); |
| 316 | } |
| 317 | |
| 318 | return 0; |
| 319 | } |
| 320 | |
| 321 | static void jump_label_del_module(struct module *mod) |
| 322 | { |
| 323 | struct jump_entry *iter_start = mod->jump_entries; |
| 324 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 325 | struct jump_entry *iter; |
| 326 | struct static_key *key = NULL; |
| 327 | struct static_key_mod *jlm, **prev; |
| 328 | |
| 329 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 330 | if (iter->key == (jump_label_t)(unsigned long)key) |
| 331 | continue; |
| 332 | |
| 333 | key = (struct static_key *)(unsigned long)iter->key; |
| 334 | |
| 335 | if (__module_address(iter->key) == mod) |
| 336 | continue; |
| 337 | |
| 338 | prev = &key->next; |
| 339 | jlm = key->next; |
| 340 | |
| 341 | while (jlm && jlm->mod != mod) { |
| 342 | prev = &jlm->next; |
| 343 | jlm = jlm->next; |
| 344 | } |
| 345 | |
| 346 | if (jlm) { |
| 347 | *prev = jlm->next; |
| 348 | kfree(jlm); |
| 349 | } |
| 350 | } |
| 351 | } |
| 352 | |
| 353 | static void jump_label_invalidate_module_init(struct module *mod) |
| 354 | { |
| 355 | struct jump_entry *iter_start = mod->jump_entries; |
| 356 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 357 | struct jump_entry *iter; |
| 358 | |
| 359 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 360 | if (within_module_init(iter->code, mod)) |
| 361 | iter->code = 0; |
| 362 | } |
| 363 | } |
| 364 | |
| 365 | static int |
| 366 | jump_label_module_notify(struct notifier_block *self, unsigned long val, |
| 367 | void *data) |
| 368 | { |
| 369 | struct module *mod = data; |
| 370 | int ret = 0; |
| 371 | |
| 372 | switch (val) { |
| 373 | case MODULE_STATE_COMING: |
| 374 | jump_label_lock(); |
| 375 | ret = jump_label_add_module(mod); |
| 376 | if (ret) |
| 377 | jump_label_del_module(mod); |
| 378 | jump_label_unlock(); |
| 379 | break; |
| 380 | case MODULE_STATE_GOING: |
| 381 | jump_label_lock(); |
| 382 | jump_label_del_module(mod); |
| 383 | jump_label_unlock(); |
| 384 | break; |
| 385 | case MODULE_STATE_LIVE: |
| 386 | jump_label_lock(); |
| 387 | jump_label_invalidate_module_init(mod); |
| 388 | jump_label_unlock(); |
| 389 | break; |
| 390 | } |
| 391 | |
| 392 | return notifier_from_errno(ret); |
| 393 | } |
| 394 | |
| 395 | struct notifier_block jump_label_module_nb = { |
| 396 | .notifier_call = jump_label_module_notify, |
| 397 | .priority = 1, /* higher than tracepoints */ |
| 398 | }; |
| 399 | |
| 400 | static __init int jump_label_init_module(void) |
| 401 | { |
| 402 | return register_module_notifier(&jump_label_module_nb); |
| 403 | } |
| 404 | early_initcall(jump_label_init_module); |
| 405 | |
| 406 | #endif /* CONFIG_MODULES */ |
| 407 | |
| 408 | /*** |
| 409 | * jump_label_text_reserved - check if addr range is reserved |
| 410 | * @start: start text addr |
| 411 | * @end: end text addr |
| 412 | * |
| 413 | * checks if the text addr located between @start and @end |
| 414 | * overlaps with any of the jump label patch addresses. Code |
| 415 | * that wants to modify kernel text should first verify that |
| 416 | * it does not overlap with any of the jump label addresses. |
| 417 | * Caller must hold jump_label_mutex. |
| 418 | * |
| 419 | * returns 1 if there is an overlap, 0 otherwise |
| 420 | */ |
| 421 | int jump_label_text_reserved(void *start, void *end) |
| 422 | { |
| 423 | int ret = __jump_label_text_reserved(__start___jump_table, |
| 424 | __stop___jump_table, start, end); |
| 425 | |
| 426 | if (ret) |
| 427 | return ret; |
| 428 | |
| 429 | #ifdef CONFIG_MODULES |
| 430 | ret = __jump_label_mod_text_reserved(start, end); |
| 431 | #endif |
| 432 | return ret; |
| 433 | } |
| 434 | |
| 435 | static void jump_label_update(struct static_key *key, int enable) |
| 436 | { |
| 437 | struct jump_entry *stop = __stop___jump_table; |
| 438 | struct jump_entry *entry = jump_label_get_entries(key); |
| 439 | |
| 440 | #ifdef CONFIG_MODULES |
| 441 | struct module *mod = __module_address((unsigned long)key); |
| 442 | |
| 443 | __jump_label_mod_update(key, enable); |
| 444 | |
| 445 | if (mod) |
| 446 | stop = mod->jump_entries + mod->num_jump_entries; |
| 447 | #endif |
| 448 | /* if there are no users, entry can be NULL */ |
| 449 | if (entry) |
| 450 | __jump_label_update(key, entry, stop, enable); |
| 451 | } |
| 452 | |
| 453 | #endif |