kernel/livepatch/core.c

   1 /*
   2  * core.c - Kernel Live Patching Core
   3  *
   4  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   5  * Copyright (C) 2014 SUSE
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2
  10  * of the License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/module.h>
  24 #include <linux/kernel.h>
  25 #include <linux/mutex.h>
  26 #include <linux/slab.h>
  27 #include <linux/ftrace.h>
  28 #include <linux/list.h>
  29 #include <linux/kallsyms.h>
  30 #include <linux/livepatch.h>
  31 #include <linux/elf.h>
  32 #include <linux/moduleloader.h>
  33 #include <asm/cacheflush.h>
  34
  35 /**
  36  * struct klp_ops - structure for tracking registered ftrace ops structs
  37  *
  38  * A single ftrace_ops is shared between all enabled replacement functions
  39  * (klp_func structs) which have the same old_addr.  This allows the switch
  40  * between function versions to happen instantaneously by updating the klp_ops
  41  * struct's func_stack list.  The winner is the klp_func at the top of the
  42  * func_stack (front of the list).
  43  *
  44  * @node:       node for the global klp_ops list
  45  * @func_stack: list head for the stack of klp_func's (active func is on top)
  46  * @fops:       registered ftrace ops struct
  47  */
  48 struct klp_ops {
  49         struct list_head node;
  50         struct list_head func_stack;
  51         struct ftrace_ops fops;
  52 };
  53
  54 /*
  55  * The klp_mutex protects the global lists and state transitions of any
  56  * structure reachable from them.  References to any structure must be obtained
  57  * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
  58  * ensure it gets consistent data).
  59  */
  60 static DEFINE_MUTEX(klp_mutex);
  61
  62 static LIST_HEAD(klp_patches);
  63 static LIST_HEAD(klp_ops);
  64
  65 static struct kobject *klp_root_kobj;
  66
  67 static struct klp_ops *klp_find_ops(unsigned long old_addr)
  68 {
  69         struct klp_ops *ops;
  70         struct klp_func *func;
  71
  72         list_for_each_entry(ops, &klp_ops, node) {
  73                 func = list_first_entry(&ops->func_stack, struct klp_func,
  74                                         stack_node);
  75                 if (func->old_addr == old_addr)
  76                         return ops;
  77         }
  78
  79         return NULL;
  80 }
  81
  82 static bool klp_is_module(struct klp_object *obj)
  83 {
  84         return obj->name;
  85 }
  86
  87 static bool klp_is_object_loaded(struct klp_object *obj)
  88 {
  89         return !obj->name || obj->mod;
  90 }
  91
  92 /* sets obj->mod if object is not vmlinux and module is found */
  93 static void klp_find_object_module(struct klp_object *obj)
  94 {
  95         struct module *mod;
  96
  97         if (!klp_is_module(obj))
  98                 return;
  99
 100         mutex_lock(&module_mutex);
 101         /*
 102          * We do not want to block removal of patched modules and therefore
 103          * we do not take a reference here. The patches are removed by
 104          * klp_module_going() instead.
 105          */
 106         mod = find_module(obj->name);
 107         /*
 108          * Do not mess work of klp_module_coming() and klp_module_going().
 109          * Note that the patch might still be needed before klp_module_going()
 110          * is called. Module functions can be called even in the GOING state
 111          * until mod->exit() finishes. This is especially important for
 112          * patches that modify semantic of the functions.
 113          */
 114         if (mod && mod->klp_alive)
 115                 obj->mod = mod;
 116
 117         mutex_unlock(&module_mutex);
 118 }
 119
 120 /* klp_mutex must be held by caller */
 121 static bool klp_is_patch_registered(struct klp_patch *patch)
 122 {
 123         struct klp_patch *mypatch;
 124
 125         list_for_each_entry(mypatch, &klp_patches, list)
 126                 if (mypatch == patch)
 127                         return true;
 128
 129         return false;
 130 }
 131
 132 static bool klp_initialized(void)
 133 {
 134         return !!klp_root_kobj;
 135 }
 136
 137 struct klp_find_arg {
 138         const char *objname;
 139         const char *name;
 140         unsigned long addr;
 141         unsigned long count;
 142         unsigned long pos;
 143 };
 144
 145 static int klp_find_callback(void *data, const char *name,
 146                              struct module *mod, unsigned long addr)
 147 {
 148         struct klp_find_arg *args = data;
 149
 150         if ((mod && !args->objname) || (!mod && args->objname))
 151                 return 0;
 152
 153         if (strcmp(args->name, name))
 154                 return 0;
 155
 156         if (args->objname && strcmp(args->objname, mod->name))
 157                 return 0;
 158
 159         args->addr = addr;
 160         args->count++;
 161
 162         /*
 163          * Finish the search when the symbol is found for the desired position
 164          * or the position is not defined for a non-unique symbol.
 165          */
 166         if ((args->pos && (args->count == args->pos)) ||
 167             (!args->pos && (args->count > 1)))
 168                 return 1;
 169
 170         return 0;
 171 }
 172
 173 static int klp_find_object_symbol(const char *objname, const char *name,
 174                                   unsigned long sympos, unsigned long *addr)
 175 {
 176         struct klp_find_arg args = {
 177                 .objname = objname,
 178                 .name = name,
 179                 .addr = 0,
 180                 .count = 0,
 181                 .pos = sympos,
 182         };
 183
 184         mutex_lock(&module_mutex);
 185         kallsyms_on_each_symbol(klp_find_callback, &args);
 186         mutex_unlock(&module_mutex);
 187
 188         /*
 189          * Ensure an address was found. If sympos is 0, ensure symbol is unique;
 190          * otherwise ensure the symbol position count matches sympos.
 191          */
 192         if (args.addr == 0)
 193                 pr_err("symbol '%s' not found in symbol table\n", name);
 194         else if (args.count > 1 && sympos == 0) {
 195                 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
 196                        name, objname);
 197         } else if (sympos != args.count && sympos > 0) {
 198                 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
 199                        sympos, name, objname ? objname : "vmlinux");
 200         } else {
 201                 *addr = args.addr;
 202                 return 0;
 203         }
 204
 205         *addr = 0;
 206         return -EINVAL;
 207 }
 208
 209 static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 210 {
 211         int i, cnt, vmlinux, ret;
 212         char objname[MODULE_NAME_LEN];
 213         char symname[KSYM_NAME_LEN];
 214         char *strtab = pmod->core_kallsyms.strtab;
 215         Elf_Rela *relas;
 216         Elf_Sym *sym;
 217         unsigned long sympos, addr;
 218
 219         /*
 220          * Since the field widths for objname and symname in the sscanf()
 221          * call are hard-coded and correspond to MODULE_NAME_LEN and
 222          * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
 223          * and KSYM_NAME_LEN have the values we expect them to have.
 224          *
 225          * Because the value of MODULE_NAME_LEN can differ among architectures,
 226          * we use the smallest/strictest upper bound possible (56, based on
 227          * the current definition of MODULE_NAME_LEN) to prevent overflows.
 228          */
 229         BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
 230
 231         relas = (Elf_Rela *) relasec->sh_addr;
 232         /* For each rela in this klp relocation section */
 233         for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
 234                 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
 235                 if (sym->st_shndx != SHN_LIVEPATCH) {
 236                         pr_err("symbol %s is not marked as a livepatch symbol",
 237                                strtab + sym->st_name);
 238                         return -EINVAL;
 239                 }
 240
 241                 /* Format: .klp.sym.objname.symname,sympos */
 242                 cnt = sscanf(strtab + sym->st_name,
 243                              ".klp.sym.%55[^.].%127[^,],%lu",
 244                              objname, symname, &sympos);
 245                 if (cnt != 3) {
 246                         pr_err("symbol %s has an incorrectly formatted name",
 247                                strtab + sym->st_name);
 248                         return -EINVAL;
 249                 }
 250
 251                 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
 252                 vmlinux = !strcmp(objname, "vmlinux");
 253                 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
 254                                              symname, sympos, &addr);
 255                 if (ret)
 256                         return ret;
 257
 258                 sym->st_value = addr;
 259         }
 260
 261         return 0;
 262 }
 263
 264 static int klp_write_object_relocations(struct module *pmod,
 265                                         struct klp_object *obj)
 266 {
 267         int i, cnt, ret = 0;
 268         const char *objname, *secname;
 269         char sec_objname[MODULE_NAME_LEN];
 270         Elf_Shdr *sec;
 271
 272         if (WARN_ON(!klp_is_object_loaded(obj)))
 273                 return -EINVAL;
 274
 275         objname = klp_is_module(obj) ? obj->name : "vmlinux";
 276
 277         module_disable_ro(pmod);
 278         /* For each klp relocation section */
 279         for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
 280                 sec = pmod->klp_info->sechdrs + i;
 281                 secname = pmod->klp_info->secstrings + sec->sh_name;
 282                 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
 283                         continue;
 284
 285                 /*
 286                  * Format: .klp.rela.sec_objname.section_name
 287                  * See comment in klp_resolve_symbols() for an explanation
 288                  * of the selected field width value.
 289                  */
 290                 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
 291                 if (cnt != 1) {
 292                         pr_err("section %s has an incorrectly formatted name",
 293                                secname);
 294                         ret = -EINVAL;
 295                         break;
 296                 }
 297
 298                 if (strcmp(objname, sec_objname))
 299                         continue;
 300
 301                 ret = klp_resolve_symbols(sec, pmod);
 302                 if (ret)
 303                         break;
 304
 305                 ret = apply_relocate_add(pmod->klp_info->sechdrs,
 306                                          pmod->core_kallsyms.strtab,
 307                                          pmod->klp_info->symndx, i, pmod);
 308                 if (ret)
 309                         break;
 310         }
 311
 312         module_enable_ro(pmod);
 313         return ret;
 314 }
 315
 316 static void notrace klp_ftrace_handler(unsigned long ip,
 317                                        unsigned long parent_ip,
 318                                        struct ftrace_ops *fops,
 319                                        struct pt_regs *regs)
 320 {
 321         struct klp_ops *ops;
 322         struct klp_func *func;
 323
 324         ops = container_of(fops, struct klp_ops, fops);
 325
 326         rcu_read_lock();
 327         func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
 328                                       stack_node);
 329         if (WARN_ON_ONCE(!func))
 330                 goto unlock;
 331
 332         klp_arch_set_pc(regs, (unsigned long)func->new_func);
 333 unlock:
 334         rcu_read_unlock();
 335 }
 336
 337 /*
 338  * Convert a function address into the appropriate ftrace location.
 339  *
 340  * Usually this is just the address of the function, but on some architectures
 341  * it's more complicated so allow them to provide a custom behaviour.
 342  */
 343 #ifndef klp_get_ftrace_location
 344 static unsigned long klp_get_ftrace_location(unsigned long faddr)
 345 {
 346         return faddr;
 347 }
 348 #endif
 349
 350 static void klp_disable_func(struct klp_func *func)
 351 {
 352         struct klp_ops *ops;
 353
 354         if (WARN_ON(func->state != KLP_ENABLED))
 355                 return;
 356         if (WARN_ON(!func->old_addr))
 357                 return;
 358
 359         ops = klp_find_ops(func->old_addr);
 360         if (WARN_ON(!ops))
 361                 return;
 362
 363         if (list_is_singular(&ops->func_stack)) {
 364                 unsigned long ftrace_loc;
 365
 366                 ftrace_loc = klp_get_ftrace_location(func->old_addr);
 367                 if (WARN_ON(!ftrace_loc))
 368                         return;
 369
 370                 WARN_ON(unregister_ftrace_function(&ops->fops));
 371                 WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
 372
 373                 list_del_rcu(&func->stack_node);
 374                 list_del(&ops->node);
 375                 kfree(ops);
 376         } else {
 377                 list_del_rcu(&func->stack_node);
 378         }
 379
 380         func->state = KLP_DISABLED;
 381 }
 382
 383 static int klp_enable_func(struct klp_func *func)
 384 {
 385         struct klp_ops *ops;
 386         int ret;
 387
 388         if (WARN_ON(!func->old_addr))
 389                 return -EINVAL;
 390
 391         if (WARN_ON(func->state != KLP_DISABLED))
 392                 return -EINVAL;
 393
 394         ops = klp_find_ops(func->old_addr);
 395         if (!ops) {
 396                 unsigned long ftrace_loc;
 397
 398                 ftrace_loc = klp_get_ftrace_location(func->old_addr);
 399                 if (!ftrace_loc) {
 400                         pr_err("failed to find location for function '%s'\n",
 401                                 func->old_name);
 402                         return -EINVAL;
 403                 }
 404
 405                 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
 406                 if (!ops)
 407                         return -ENOMEM;
 408
 409                 ops->fops.func = klp_ftrace_handler;
 410                 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
 411                                   FTRACE_OPS_FL_DYNAMIC |
 412                                   FTRACE_OPS_FL_IPMODIFY;
 413
 414                 list_add(&ops->node, &klp_ops);
 415
 416                 INIT_LIST_HEAD(&ops->func_stack);
 417                 list_add_rcu(&func->stack_node, &ops->func_stack);
 418
 419                 ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
 420                 if (ret) {
 421                         pr_err("failed to set ftrace filter for function '%s' (%d)\n",
 422                                func->old_name, ret);
 423                         goto err;
 424                 }
 425
 426                 ret = register_ftrace_function(&ops->fops);
 427                 if (ret) {
 428                         pr_err("failed to register ftrace handler for function '%s' (%d)\n",
 429                                func->old_name, ret);
 430                         ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
 431                         goto err;
 432                 }
 433
 434
 435         } else {
 436                 list_add_rcu(&func->stack_node, &ops->func_stack);
 437         }
 438
 439         func->state = KLP_ENABLED;
 440
 441         return 0;
 442
 443 err:
 444         list_del_rcu(&func->stack_node);
 445         list_del(&ops->node);
 446         kfree(ops);
 447         return ret;
 448 }
 449
 450 static void klp_disable_object(struct klp_object *obj)
 451 {
 452         struct klp_func *func;
 453
 454         klp_for_each_func(obj, func)
 455                 if (func->state == KLP_ENABLED)
 456                         klp_disable_func(func);
 457
 458         obj->state = KLP_DISABLED;
 459 }
 460
 461 static int klp_enable_object(struct klp_object *obj)
 462 {
 463         struct klp_func *func;
 464         int ret;
 465
 466         if (WARN_ON(obj->state != KLP_DISABLED))
 467                 return -EINVAL;
 468
 469         if (WARN_ON(!klp_is_object_loaded(obj)))
 470                 return -EINVAL;
 471
 472         klp_for_each_func(obj, func) {
 473                 ret = klp_enable_func(func);
 474                 if (ret) {
 475                         klp_disable_object(obj);
 476                         return ret;
 477                 }
 478         }
 479         obj->state = KLP_ENABLED;
 480
 481         return 0;
 482 }
 483
 484 static int __klp_disable_patch(struct klp_patch *patch)
 485 {
 486         struct klp_object *obj;
 487
 488         /* enforce stacking: only the last enabled patch can be disabled */
 489         if (!list_is_last(&patch->list, &klp_patches) &&
 490             list_next_entry(patch, list)->state == KLP_ENABLED)
 491                 return -EBUSY;
 492
 493         pr_notice("disabling patch '%s'\n", patch->mod->name);
 494
 495         klp_for_each_object(patch, obj) {
 496                 if (obj->state == KLP_ENABLED)
 497                         klp_disable_object(obj);
 498         }
 499
 500         patch->state = KLP_DISABLED;
 501
 502         return 0;
 503 }
 504
 505 /**
 506  * klp_disable_patch() - disables a registered patch
 507  * @patch:      The registered, enabled patch to be disabled
 508  *
 509  * Unregisters the patched functions from ftrace.
 510  *
 511  * Return: 0 on success, otherwise error
 512  */
 513 int klp_disable_patch(struct klp_patch *patch)
 514 {
 515         int ret;
 516
 517         mutex_lock(&klp_mutex);
 518
 519         if (!klp_is_patch_registered(patch)) {
 520                 ret = -EINVAL;
 521                 goto err;
 522         }
 523
 524         if (patch->state == KLP_DISABLED) {
 525                 ret = -EINVAL;
 526                 goto err;
 527         }
 528
 529         ret = __klp_disable_patch(patch);
 530
 531 err:
 532         mutex_unlock(&klp_mutex);
 533         return ret;
 534 }
 535 EXPORT_SYMBOL_GPL(klp_disable_patch);
 536
 537 static int __klp_enable_patch(struct klp_patch *patch)
 538 {
 539         struct klp_object *obj;
 540         int ret;
 541
 542         if (WARN_ON(patch->state != KLP_DISABLED))
 543                 return -EINVAL;
 544
 545         /* enforce stacking: only the first disabled patch can be enabled */
 546         if (patch->list.prev != &klp_patches &&
 547             list_prev_entry(patch, list)->state == KLP_DISABLED)
 548                 return -EBUSY;
 549
 550         pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
 551         add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
 552
 553         pr_notice("enabling patch '%s'\n", patch->mod->name);
 554
 555         klp_for_each_object(patch, obj) {
 556                 if (!klp_is_object_loaded(obj))
 557                         continue;
 558
 559                 ret = klp_enable_object(obj);
 560                 if (ret)
 561                         goto unregister;
 562         }
 563
 564         patch->state = KLP_ENABLED;
 565
 566         return 0;
 567
 568 unregister:
 569         WARN_ON(__klp_disable_patch(patch));
 570         return ret;
 571 }
 572
 573 /**
 574  * klp_enable_patch() - enables a registered patch
 575  * @patch:      The registered, disabled patch to be enabled
 576  *
 577  * Performs the needed symbol lookups and code relocations,
 578  * then registers the patched functions with ftrace.
 579  *
 580  * Return: 0 on success, otherwise error
 581  */
 582 int klp_enable_patch(struct klp_patch *patch)
 583 {
 584         int ret;
 585
 586         mutex_lock(&klp_mutex);
 587
 588         if (!klp_is_patch_registered(patch)) {
 589                 ret = -EINVAL;
 590                 goto err;
 591         }
 592
 593         ret = __klp_enable_patch(patch);
 594
 595 err:
 596         mutex_unlock(&klp_mutex);
 597         return ret;
 598 }
 599 EXPORT_SYMBOL_GPL(klp_enable_patch);
 600
 601 /*
 602  * Sysfs Interface
 603  *
 604  * /sys/kernel/livepatch
 605  * /sys/kernel/livepatch/<patch>
 606  * /sys/kernel/livepatch/<patch>/enabled
 607  * /sys/kernel/livepatch/<patch>/<object>
 608  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
 609  */
 610
 611 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 612                              const char *buf, size_t count)
 613 {
 614         struct klp_patch *patch;
 615         int ret;
 616         unsigned long val;
 617
 618         ret = kstrtoul(buf, 10, &val);
 619         if (ret)
 620                 return -EINVAL;
 621
 622         if (val != KLP_DISABLED && val != KLP_ENABLED)
 623                 return -EINVAL;
 624
 625         patch = container_of(kobj, struct klp_patch, kobj);
 626
 627         mutex_lock(&klp_mutex);
 628
 629         if (val == patch->state) {
 630                 /* already in requested state */
 631                 ret = -EINVAL;
 632                 goto err;
 633         }
 634
 635         if (val == KLP_ENABLED) {
 636                 ret = __klp_enable_patch(patch);
 637                 if (ret)
 638                         goto err;
 639         } else {
 640                 ret = __klp_disable_patch(patch);
 641                 if (ret)
 642                         goto err;
 643         }
 644
 645         mutex_unlock(&klp_mutex);
 646
 647         return count;
 648
 649 err:
 650         mutex_unlock(&klp_mutex);
 651         return ret;
 652 }
 653
 654 static ssize_t enabled_show(struct kobject *kobj,
 655                             struct kobj_attribute *attr, char *buf)
 656 {
 657         struct klp_patch *patch;
 658
 659         patch = container_of(kobj, struct klp_patch, kobj);
 660         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
 661 }
 662
 663 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 664 static struct attribute *klp_patch_attrs[] = {
 665         &enabled_kobj_attr.attr,
 666         NULL
 667 };
 668
 669 static void klp_kobj_release_patch(struct kobject *kobj)
 670 {
 671         /*
 672          * Once we have a consistency model we'll need to module_put() the
 673          * patch module here.  See klp_register_patch() for more details.
 674          */
 675 }
 676
 677 static struct kobj_type klp_ktype_patch = {
 678         .release = klp_kobj_release_patch,
 679         .sysfs_ops = &kobj_sysfs_ops,
 680         .default_attrs = klp_patch_attrs,
 681 };
 682
 683 static void klp_kobj_release_object(struct kobject *kobj)
 684 {
 685 }
 686
 687 static struct kobj_type klp_ktype_object = {
 688         .release = klp_kobj_release_object,
 689         .sysfs_ops = &kobj_sysfs_ops,
 690 };
 691
 692 static void klp_kobj_release_func(struct kobject *kobj)
 693 {
 694 }
 695
 696 static struct kobj_type klp_ktype_func = {
 697         .release = klp_kobj_release_func,
 698         .sysfs_ops = &kobj_sysfs_ops,
 699 };
 700
 701 /*
 702  * Free all functions' kobjects in the array up to some limit. When limit is
 703  * NULL, all kobjects are freed.
 704  */
 705 static void klp_free_funcs_limited(struct klp_object *obj,
 706                                    struct klp_func *limit)
 707 {
 708         struct klp_func *func;
 709
 710         for (func = obj->funcs; func->old_name && func != limit; func++)
 711                 kobject_put(&func->kobj);
 712 }
 713
 714 /* Clean up when a patched object is unloaded */
 715 static void klp_free_object_loaded(struct klp_object *obj)
 716 {
 717         struct klp_func *func;
 718
 719         obj->mod = NULL;
 720
 721         klp_for_each_func(obj, func)
 722                 func->old_addr = 0;
 723 }
 724
 725 /*
 726  * Free all objects' kobjects in the array up to some limit. When limit is
 727  * NULL, all kobjects are freed.
 728  */
 729 static void klp_free_objects_limited(struct klp_patch *patch,
 730                                      struct klp_object *limit)
 731 {
 732         struct klp_object *obj;
 733
 734         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 735                 klp_free_funcs_limited(obj, NULL);
 736                 kobject_put(&obj->kobj);
 737         }
 738 }
 739
 740 static void klp_free_patch(struct klp_patch *patch)
 741 {
 742         klp_free_objects_limited(patch, NULL);
 743         if (!list_empty(&patch->list))
 744                 list_del(&patch->list);
 745         kobject_put(&patch->kobj);
 746 }
 747
 748 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 749 {
 750         INIT_LIST_HEAD(&func->stack_node);
 751         func->state = KLP_DISABLED;
 752
 753         /* The format for the sysfs directory is <function,sympos> where sympos
 754          * is the nth occurrence of this symbol in kallsyms for the patched
 755          * object. If the user selects 0 for old_sympos, then 1 will be used
 756          * since a unique symbol will be the first occurrence.
 757          */
 758         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 759                                     &obj->kobj, "%s,%lu", func->old_name,
 760                                     func->old_sympos ? func->old_sympos : 1);
 761 }
 762
 763 /* parts of the initialization that is done only when the object is loaded */
 764 static int klp_init_object_loaded(struct klp_patch *patch,
 765                                   struct klp_object *obj)
 766 {
 767         struct klp_func *func;
 768         int ret;
 769
 770         ret = klp_write_object_relocations(patch->mod, obj);
 771         if (ret)
 772                 return ret;
 773
 774         klp_for_each_func(obj, func) {
 775                 ret = klp_find_object_symbol(obj->name, func->old_name,
 776                                              func->old_sympos,
 777                                              &func->old_addr);
 778                 if (ret)
 779                         return ret;
 780         }
 781
 782         return 0;
 783 }
 784
 785 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 786 {
 787         struct klp_func *func;
 788         int ret;
 789         const char *name;
 790
 791         if (!obj->funcs)
 792                 return -EINVAL;
 793
 794         obj->state = KLP_DISABLED;
 795         obj->mod = NULL;
 796
 797         klp_find_object_module(obj);
 798
 799         name = klp_is_module(obj) ? obj->name : "vmlinux";
 800         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
 801                                    &patch->kobj, "%s", name);
 802         if (ret)
 803                 return ret;
 804
 805         klp_for_each_func(obj, func) {
 806                 ret = klp_init_func(obj, func);
 807                 if (ret)
 808                         goto free;
 809         }
 810
 811         if (klp_is_object_loaded(obj)) {
 812                 ret = klp_init_object_loaded(patch, obj);
 813                 if (ret)
 814                         goto free;
 815         }
 816
 817         return 0;
 818
 819 free:
 820         klp_free_funcs_limited(obj, func);
 821         kobject_put(&obj->kobj);
 822         return ret;
 823 }
 824
 825 static int klp_init_patch(struct klp_patch *patch)
 826 {
 827         struct klp_object *obj;
 828         int ret;
 829
 830         if (!patch->objs)
 831                 return -EINVAL;
 832
 833         mutex_lock(&klp_mutex);
 834
 835         patch->state = KLP_DISABLED;
 836
 837         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 838                                    klp_root_kobj, "%s", patch->mod->name);
 839         if (ret)
 840                 goto unlock;
 841
 842         klp_for_each_object(patch, obj) {
 843                 ret = klp_init_object(patch, obj);
 844                 if (ret)
 845                         goto free;
 846         }
 847
 848         list_add_tail(&patch->list, &klp_patches);
 849
 850         mutex_unlock(&klp_mutex);
 851
 852         return 0;
 853
 854 free:
 855         klp_free_objects_limited(patch, obj);
 856         kobject_put(&patch->kobj);
 857 unlock:
 858         mutex_unlock(&klp_mutex);
 859         return ret;
 860 }
 861
 862 /**
 863  * klp_unregister_patch() - unregisters a patch
 864  * @patch:      Disabled patch to be unregistered
 865  *
 866  * Frees the data structures and removes the sysfs interface.
 867  *
 868  * Return: 0 on success, otherwise error
 869  */
 870 int klp_unregister_patch(struct klp_patch *patch)
 871 {
 872         int ret = 0;
 873
 874         mutex_lock(&klp_mutex);
 875
 876         if (!klp_is_patch_registered(patch)) {
 877                 ret = -EINVAL;
 878                 goto out;
 879         }
 880
 881         if (patch->state == KLP_ENABLED) {
 882                 ret = -EBUSY;
 883                 goto out;
 884         }
 885
 886         klp_free_patch(patch);
 887
 888 out:
 889         mutex_unlock(&klp_mutex);
 890         return ret;
 891 }
 892 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 893
 894 /**
 895  * klp_register_patch() - registers a patch
 896  * @patch:      Patch to be registered
 897  *
 898  * Initializes the data structure associated with the patch and
 899  * creates the sysfs interface.
 900  *
 901  * Return: 0 on success, otherwise error
 902  */
 903 int klp_register_patch(struct klp_patch *patch)
 904 {
 905         int ret;
 906
 907         if (!patch || !patch->mod)
 908                 return -EINVAL;
 909
 910         if (!is_livepatch_module(patch->mod)) {
 911                 pr_err("module %s is not marked as a livepatch module",
 912                        patch->mod->name);
 913                 return -EINVAL;
 914         }
 915
 916         if (!klp_initialized())
 917                 return -ENODEV;
 918
 919         /*
 920          * A reference is taken on the patch module to prevent it from being
 921          * unloaded.  Right now, we don't allow patch modules to unload since
 922          * there is currently no method to determine if a thread is still
 923          * running in the patched code contained in the patch module once
 924          * the ftrace registration is successful.
 925          */
 926         if (!try_module_get(patch->mod))
 927                 return -ENODEV;
 928
 929         ret = klp_init_patch(patch);
 930         if (ret)
 931                 module_put(patch->mod);
 932
 933         return ret;
 934 }
 935 EXPORT_SYMBOL_GPL(klp_register_patch);
 936
 937 int klp_module_coming(struct module *mod)
 938 {
 939         int ret;
 940         struct klp_patch *patch;
 941         struct klp_object *obj;
 942
 943         if (WARN_ON(mod->state != MODULE_STATE_COMING))
 944                 return -EINVAL;
 945
 946         mutex_lock(&klp_mutex);
 947         /*
 948          * Each module has to know that klp_module_coming()
 949          * has been called. We never know what module will
 950          * get patched by a new patch.
 951          */
 952         mod->klp_alive = true;
 953
 954         list_for_each_entry(patch, &klp_patches, list) {
 955                 klp_for_each_object(patch, obj) {
 956                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 957                                 continue;
 958
 959                         obj->mod = mod;
 960
 961                         ret = klp_init_object_loaded(patch, obj);
 962                         if (ret) {
 963                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
 964                                         patch->mod->name, obj->mod->name, ret);
 965                                 goto err;
 966                         }
 967
 968                         if (patch->state == KLP_DISABLED)
 969                                 break;
 970
 971                         pr_notice("applying patch '%s' to loading module '%s'\n",
 972                                   patch->mod->name, obj->mod->name);
 973
 974                         ret = klp_enable_object(obj);
 975                         if (ret) {
 976                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 977                                         patch->mod->name, obj->mod->name, ret);
 978                                 goto err;
 979                         }
 980
 981                         break;
 982                 }
 983         }
 984
 985         mutex_unlock(&klp_mutex);
 986
 987         return 0;
 988
 989 err:
 990         /*
 991          * If a patch is unsuccessfully applied, return
 992          * error to the module loader.
 993          */
 994         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
 995                 patch->mod->name, obj->mod->name, obj->mod->name);
 996         mod->klp_alive = false;
 997         klp_free_object_loaded(obj);
 998         mutex_unlock(&klp_mutex);
 999
1000         return ret;
1001 }
1002
1003 void klp_module_going(struct module *mod)
1004 {
1005         struct klp_patch *patch;
1006         struct klp_object *obj;
1007
1008         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1009                     mod->state != MODULE_STATE_COMING))
1010                 return;
1011
1012         mutex_lock(&klp_mutex);
1013         /*
1014          * Each module has to know that klp_module_going()
1015          * has been called. We never know what module will
1016          * get patched by a new patch.
1017          */
1018         mod->klp_alive = false;
1019
1020         list_for_each_entry(patch, &klp_patches, list) {
1021                 klp_for_each_object(patch, obj) {
1022                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1023                                 continue;
1024
1025                         if (patch->state != KLP_DISABLED) {
1026                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1027                                           patch->mod->name, obj->mod->name);
1028                                 klp_disable_object(obj);
1029                         }
1030
1031                         klp_free_object_loaded(obj);
1032                         break;
1033                 }
1034         }
1035
1036         mutex_unlock(&klp_mutex);
1037 }
1038
1039 static int __init klp_init(void)
1040 {
1041         int ret;
1042
1043         ret = klp_check_compiler_support();
1044         if (ret) {
1045                 pr_info("Your compiler is too old; turning off.\n");
1046                 return -EINVAL;
1047         }
1048
1049         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1050         if (!klp_root_kobj)
1051                 return -ENOMEM;
1052
1053         return 0;
1054 }
1055
1056 module_init(klp_init);