Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 1 | /* |
| 2 | * jump label support |
| 3 | * |
| 4 | * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 5 | * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com> |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 6 | * |
| 7 | */ |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 8 | #include <linux/memory.h> |
| 9 | #include <linux/uaccess.h> |
| 10 | #include <linux/module.h> |
| 11 | #include <linux/list.h> |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 12 | #include <linux/slab.h> |
| 13 | #include <linux/sort.h> |
| 14 | #include <linux/err.h> |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 15 | #include <linux/jump_label.h> |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 16 | |
| 17 | #ifdef HAVE_JUMP_LABEL |
| 18 | |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 19 | /* mutex to protect coming/going of the the jump_label table */ |
| 20 | static DEFINE_MUTEX(jump_label_mutex); |
| 21 | |
Jason Baron | 91bad2f | 2010-10-01 17:23:48 -0400 | [diff] [blame] | 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 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 32 | bool jump_label_enabled(struct jump_label_key *key) |
| 33 | { |
| 34 | return !!atomic_read(&key->enabled); |
| 35 | } |
| 36 | |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 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 |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 52 | jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 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 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 61 | static void jump_label_update(struct jump_label_key *key, int enable); |
| 62 | |
| 63 | void jump_label_inc(struct jump_label_key *key) |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 64 | { |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 65 | if (atomic_inc_not_zero(&key->enabled)) |
| 66 | return; |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 67 | |
Jason Baron | 91bad2f | 2010-10-01 17:23:48 -0400 | [diff] [blame] | 68 | jump_label_lock(); |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 69 | if (atomic_add_return(1, &key->enabled) == 1) |
| 70 | jump_label_update(key, JUMP_LABEL_ENABLE); |
| 71 | jump_label_unlock(); |
| 72 | } |
| 73 | |
| 74 | void jump_label_dec(struct jump_label_key *key) |
| 75 | { |
| 76 | if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) |
| 77 | return; |
| 78 | |
| 79 | jump_label_update(key, JUMP_LABEL_DISABLE); |
Jason Baron | 91bad2f | 2010-10-01 17:23:48 -0400 | [diff] [blame] | 80 | jump_label_unlock(); |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 81 | } |
| 82 | |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 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 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 92 | static int __jump_label_text_reserved(struct jump_entry *iter_start, |
| 93 | struct jump_entry *iter_stop, void *start, void *end) |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 94 | { |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 95 | struct jump_entry *iter; |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 96 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 97 | iter = iter_start; |
| 98 | while (iter < iter_stop) { |
| 99 | if (addr_conflict(iter, start, end)) |
| 100 | return 1; |
| 101 | iter++; |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 102 | } |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 103 | |
| 104 | return 0; |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 105 | } |
| 106 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 107 | static void __jump_label_update(struct jump_label_key *key, |
Jiri Olsa | 7cbc5b8 | 2011-05-10 12:43:46 +0200 | [diff] [blame] | 108 | struct jump_entry *entry, |
| 109 | struct jump_entry *stop, int enable) |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 110 | { |
Jiri Olsa | 7cbc5b8 | 2011-05-10 12:43:46 +0200 | [diff] [blame] | 111 | for (; (entry < stop) && |
| 112 | (entry->key == (jump_label_t)(unsigned long)key); |
| 113 | entry++) { |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 114 | /* |
| 115 | * entry->code set to 0 invalidates module init text sections |
| 116 | * kernel_text_address() verifies we are not in core kernel |
| 117 | * init code, see jump_label_invalidate_module_init(). |
| 118 | */ |
| 119 | if (entry->code && kernel_text_address(entry->code)) |
| 120 | arch_jump_label_transform(entry, enable); |
| 121 | } |
| 122 | } |
| 123 | |
| 124 | /* |
| 125 | * Not all archs need this. |
| 126 | */ |
| 127 | void __weak arch_jump_label_text_poke_early(jump_label_t addr) |
| 128 | { |
| 129 | } |
| 130 | |
| 131 | static __init int jump_label_init(void) |
| 132 | { |
| 133 | struct jump_entry *iter_start = __start___jump_table; |
| 134 | struct jump_entry *iter_stop = __stop___jump_table; |
| 135 | struct jump_label_key *key = NULL; |
| 136 | struct jump_entry *iter; |
| 137 | |
| 138 | jump_label_lock(); |
| 139 | jump_label_sort_entries(iter_start, iter_stop); |
| 140 | |
| 141 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 142 | arch_jump_label_text_poke_early(iter->code); |
| 143 | if (iter->key == (jump_label_t)(unsigned long)key) |
| 144 | continue; |
| 145 | |
| 146 | key = (struct jump_label_key *)(unsigned long)iter->key; |
| 147 | atomic_set(&key->enabled, 0); |
| 148 | key->entries = iter; |
| 149 | #ifdef CONFIG_MODULES |
| 150 | key->next = NULL; |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 151 | #endif |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 152 | } |
| 153 | jump_label_unlock(); |
| 154 | |
| 155 | return 0; |
| 156 | } |
| 157 | early_initcall(jump_label_init); |
| 158 | |
| 159 | #ifdef CONFIG_MODULES |
| 160 | |
| 161 | struct jump_label_mod { |
| 162 | struct jump_label_mod *next; |
| 163 | struct jump_entry *entries; |
| 164 | struct module *mod; |
| 165 | }; |
| 166 | |
| 167 | static int __jump_label_mod_text_reserved(void *start, void *end) |
| 168 | { |
| 169 | struct module *mod; |
| 170 | |
| 171 | mod = __module_text_address((unsigned long)start); |
| 172 | if (!mod) |
| 173 | return 0; |
| 174 | |
| 175 | WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); |
| 176 | |
| 177 | return __jump_label_text_reserved(mod->jump_entries, |
| 178 | mod->jump_entries + mod->num_jump_entries, |
| 179 | start, end); |
| 180 | } |
| 181 | |
| 182 | static void __jump_label_mod_update(struct jump_label_key *key, int enable) |
| 183 | { |
| 184 | struct jump_label_mod *mod = key->next; |
| 185 | |
| 186 | while (mod) { |
Jiri Olsa | 7cbc5b8 | 2011-05-10 12:43:46 +0200 | [diff] [blame] | 187 | struct module *m = mod->mod; |
| 188 | |
| 189 | __jump_label_update(key, mod->entries, |
| 190 | m->jump_entries + m->num_jump_entries, |
| 191 | enable); |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 192 | mod = mod->next; |
| 193 | } |
| 194 | } |
| 195 | |
| 196 | /*** |
| 197 | * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() |
| 198 | * @mod: module to patch |
| 199 | * |
| 200 | * Allow for run-time selection of the optimal nops. Before the module |
| 201 | * loads patch these with arch_get_jump_label_nop(), which is specified by |
| 202 | * the arch specific jump label code. |
| 203 | */ |
| 204 | void jump_label_apply_nops(struct module *mod) |
| 205 | { |
| 206 | struct jump_entry *iter_start = mod->jump_entries; |
| 207 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 208 | struct jump_entry *iter; |
| 209 | |
| 210 | /* if the module doesn't have jump label entries, just return */ |
| 211 | if (iter_start == iter_stop) |
| 212 | return; |
| 213 | |
| 214 | for (iter = iter_start; iter < iter_stop; iter++) |
| 215 | arch_jump_label_text_poke_early(iter->code); |
| 216 | } |
| 217 | |
| 218 | static int jump_label_add_module(struct module *mod) |
| 219 | { |
| 220 | struct jump_entry *iter_start = mod->jump_entries; |
| 221 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 222 | struct jump_entry *iter; |
| 223 | struct jump_label_key *key = NULL; |
| 224 | struct jump_label_mod *jlm; |
| 225 | |
| 226 | /* if the module doesn't have jump label entries, just return */ |
| 227 | if (iter_start == iter_stop) |
| 228 | return 0; |
| 229 | |
| 230 | jump_label_sort_entries(iter_start, iter_stop); |
| 231 | |
| 232 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 233 | if (iter->key == (jump_label_t)(unsigned long)key) |
| 234 | continue; |
| 235 | |
| 236 | key = (struct jump_label_key *)(unsigned long)iter->key; |
| 237 | |
| 238 | if (__module_address(iter->key) == mod) { |
| 239 | atomic_set(&key->enabled, 0); |
| 240 | key->entries = iter; |
| 241 | key->next = NULL; |
| 242 | continue; |
| 243 | } |
| 244 | |
| 245 | jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL); |
| 246 | if (!jlm) |
| 247 | return -ENOMEM; |
| 248 | |
| 249 | jlm->mod = mod; |
| 250 | jlm->entries = iter; |
| 251 | jlm->next = key->next; |
| 252 | key->next = jlm; |
| 253 | |
| 254 | if (jump_label_enabled(key)) |
Jiri Olsa | 7cbc5b8 | 2011-05-10 12:43:46 +0200 | [diff] [blame] | 255 | __jump_label_update(key, iter, iter_stop, |
| 256 | JUMP_LABEL_ENABLE); |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 257 | } |
| 258 | |
| 259 | return 0; |
| 260 | } |
| 261 | |
| 262 | static void jump_label_del_module(struct module *mod) |
| 263 | { |
| 264 | struct jump_entry *iter_start = mod->jump_entries; |
| 265 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 266 | struct jump_entry *iter; |
| 267 | struct jump_label_key *key = NULL; |
| 268 | struct jump_label_mod *jlm, **prev; |
| 269 | |
| 270 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 271 | if (iter->key == (jump_label_t)(unsigned long)key) |
| 272 | continue; |
| 273 | |
| 274 | key = (struct jump_label_key *)(unsigned long)iter->key; |
| 275 | |
| 276 | if (__module_address(iter->key) == mod) |
| 277 | continue; |
| 278 | |
| 279 | prev = &key->next; |
| 280 | jlm = key->next; |
| 281 | |
| 282 | while (jlm && jlm->mod != mod) { |
| 283 | prev = &jlm->next; |
| 284 | jlm = jlm->next; |
| 285 | } |
| 286 | |
| 287 | if (jlm) { |
| 288 | *prev = jlm->next; |
| 289 | kfree(jlm); |
| 290 | } |
| 291 | } |
| 292 | } |
| 293 | |
| 294 | static void jump_label_invalidate_module_init(struct module *mod) |
| 295 | { |
| 296 | struct jump_entry *iter_start = mod->jump_entries; |
| 297 | struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
| 298 | struct jump_entry *iter; |
| 299 | |
| 300 | for (iter = iter_start; iter < iter_stop; iter++) { |
| 301 | if (within_module_init(iter->code, mod)) |
| 302 | iter->code = 0; |
| 303 | } |
| 304 | } |
| 305 | |
| 306 | static int |
| 307 | jump_label_module_notify(struct notifier_block *self, unsigned long val, |
| 308 | void *data) |
| 309 | { |
| 310 | struct module *mod = data; |
| 311 | int ret = 0; |
| 312 | |
| 313 | switch (val) { |
| 314 | case MODULE_STATE_COMING: |
| 315 | jump_label_lock(); |
| 316 | ret = jump_label_add_module(mod); |
| 317 | if (ret) |
| 318 | jump_label_del_module(mod); |
| 319 | jump_label_unlock(); |
| 320 | break; |
| 321 | case MODULE_STATE_GOING: |
| 322 | jump_label_lock(); |
| 323 | jump_label_del_module(mod); |
| 324 | jump_label_unlock(); |
| 325 | break; |
| 326 | case MODULE_STATE_LIVE: |
| 327 | jump_label_lock(); |
| 328 | jump_label_invalidate_module_init(mod); |
| 329 | jump_label_unlock(); |
| 330 | break; |
| 331 | } |
| 332 | |
| 333 | return notifier_from_errno(ret); |
| 334 | } |
| 335 | |
| 336 | struct notifier_block jump_label_module_nb = { |
| 337 | .notifier_call = jump_label_module_notify, |
| 338 | .priority = 1, /* higher than tracepoints */ |
| 339 | }; |
| 340 | |
| 341 | static __init int jump_label_init_module(void) |
| 342 | { |
| 343 | return register_module_notifier(&jump_label_module_nb); |
| 344 | } |
| 345 | early_initcall(jump_label_init_module); |
| 346 | |
| 347 | #endif /* CONFIG_MODULES */ |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 348 | |
| 349 | /*** |
| 350 | * jump_label_text_reserved - check if addr range is reserved |
| 351 | * @start: start text addr |
| 352 | * @end: end text addr |
| 353 | * |
| 354 | * checks if the text addr located between @start and @end |
| 355 | * overlaps with any of the jump label patch addresses. Code |
| 356 | * that wants to modify kernel text should first verify that |
| 357 | * it does not overlap with any of the jump label addresses. |
Jason Baron | 91bad2f | 2010-10-01 17:23:48 -0400 | [diff] [blame] | 358 | * Caller must hold jump_label_mutex. |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 359 | * |
| 360 | * returns 1 if there is an overlap, 0 otherwise |
| 361 | */ |
| 362 | int jump_label_text_reserved(void *start, void *end) |
| 363 | { |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 364 | int ret = __jump_label_text_reserved(__start___jump_table, |
| 365 | __stop___jump_table, start, end); |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 366 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 367 | if (ret) |
| 368 | return ret; |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 369 | |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 370 | #ifdef CONFIG_MODULES |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 371 | ret = __jump_label_mod_text_reserved(start, end); |
Jason Baron | 4c3ef6d | 2010-09-17 11:09:08 -0400 | [diff] [blame] | 372 | #endif |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 373 | return ret; |
| 374 | } |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 375 | |
| 376 | static void jump_label_update(struct jump_label_key *key, int enable) |
| 377 | { |
Xiao Guangrong | 140fe3b | 2011-06-21 10:35:55 +0800 | [diff] [blame] | 378 | struct jump_entry *entry = key->entries, *stop = __stop___jump_table; |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 379 | |
| 380 | #ifdef CONFIG_MODULES |
Xiao Guangrong | 140fe3b | 2011-06-21 10:35:55 +0800 | [diff] [blame] | 381 | struct module *mod = __module_address((jump_label_t)key); |
| 382 | |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 383 | __jump_label_mod_update(key, enable); |
Xiao Guangrong | 140fe3b | 2011-06-21 10:35:55 +0800 | [diff] [blame] | 384 | |
| 385 | if (mod) |
| 386 | stop = mod->jump_entries + mod->num_jump_entries; |
Jason Baron | d430d3d | 2011-03-16 17:29:47 -0400 | [diff] [blame] | 387 | #endif |
Xiao Guangrong | 140fe3b | 2011-06-21 10:35:55 +0800 | [diff] [blame] | 388 | /* if there are no users, entry can be NULL */ |
| 389 | if (entry) |
| 390 | __jump_label_update(key, entry, stop, enable); |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 391 | } |
| 392 | |
Jason Baron | bf5438fc | 2010-09-17 11:09:00 -0400 | [diff] [blame] | 393 | #endif |