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
  32 /**
  33  * struct klp_ops - structure for tracking registered ftrace ops structs
  34  *
  35  * A single ftrace_ops is shared between all enabled replacement functions
  36  * (klp_func structs) which have the same old_addr.  This allows the switch
  37  * between function versions to happen instantaneously by updating the klp_ops
  38  * struct's func_stack list.  The winner is the klp_func at the top of the
  39  * func_stack (front of the list).
  40  *
  41  * @node:       node for the global klp_ops list
  42  * @func_stack: list head for the stack of klp_func's (active func is on top)
  43  * @fops:       registered ftrace ops struct
  44  */
  45 struct klp_ops {
  46         struct list_head node;
  47         struct list_head func_stack;
  48         struct ftrace_ops fops;
  49 };
  50
  51 /*
  52  * The klp_mutex protects the global lists and state transitions of any
  53  * structure reachable from them.  References to any structure must be obtained
  54  * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
  55  * ensure it gets consistent data).
  56  */
  57 static DEFINE_MUTEX(klp_mutex);
  58
  59 static LIST_HEAD(klp_patches);
  60 static LIST_HEAD(klp_ops);
  61
  62 static struct kobject *klp_root_kobj;
  63
  64 static struct klp_ops *klp_find_ops(unsigned long old_addr)
  65 {
  66         struct klp_ops *ops;
  67         struct klp_func *func;
  68
  69         list_for_each_entry(ops, &klp_ops, node) {
  70                 func = list_first_entry(&ops->func_stack, struct klp_func,
  71                                         stack_node);
  72                 if (func->old_addr == old_addr)
  73                         return ops;
  74         }
  75
  76         return NULL;
  77 }
  78
  79 static bool klp_is_module(struct klp_object *obj)
  80 {
  81         return obj->name;
  82 }
  83
  84 static bool klp_is_object_loaded(struct klp_object *obj)
  85 {
  86         return !obj->name || obj->mod;
  87 }
  88
  89 /* sets obj->mod if object is not vmlinux and module is found */
  90 static void klp_find_object_module(struct klp_object *obj)
  91 {
  92         struct module *mod;
  93
  94         if (!klp_is_module(obj))
  95                 return;
  96
  97         mutex_lock(&module_mutex);
  98         /*
  99          * We do not want to block removal of patched modules and therefore
 100          * we do not take a reference here. The patches are removed by
 101          * a going module handler instead.
 102          */
 103         mod = find_module(obj->name);
 104         /*
 105          * Do not mess work of the module coming and going notifiers.
 106          * Note that the patch might still be needed before the going handler
 107          * is called. Module functions can be called even in the GOING state
 108          * until mod->exit() finishes. This is especially important for
 109          * patches that modify semantic of the functions.
 110          */
 111         if (mod && mod->klp_alive)
 112                 obj->mod = mod;
 113
 114         mutex_unlock(&module_mutex);
 115 }
 116
 117 /* klp_mutex must be held by caller */
 118 static bool klp_is_patch_registered(struct klp_patch *patch)
 119 {
 120         struct klp_patch *mypatch;
 121
 122         list_for_each_entry(mypatch, &klp_patches, list)
 123                 if (mypatch == patch)
 124                         return true;
 125
 126         return false;
 127 }
 128
 129 static bool klp_initialized(void)
 130 {
 131         return !!klp_root_kobj;
 132 }
 133
 134 struct klp_find_arg {
 135         const char *objname;
 136         const char *name;
 137         unsigned long addr;
 138         /*
 139          * If count == 0, the symbol was not found. If count == 1, a unique
 140          * match was found and addr is set.  If count > 1, there is
 141          * unresolvable ambiguity among "count" number of symbols with the same
 142          * name in the same object.
 143          */
 144         unsigned long count;
 145 };
 146
 147 static int klp_find_callback(void *data, const char *name,
 148                              struct module *mod, unsigned long addr)
 149 {
 150         struct klp_find_arg *args = data;
 151
 152         if ((mod && !args->objname) || (!mod && args->objname))
 153                 return 0;
 154
 155         if (strcmp(args->name, name))
 156                 return 0;
 157
 158         if (args->objname && strcmp(args->objname, mod->name))
 159                 return 0;
 160
 161         /*
 162          * args->addr might be overwritten if another match is found
 163          * but klp_find_object_symbol() handles this and only returns the
 164          * addr if count == 1.
 165          */
 166         args->addr = addr;
 167         args->count++;
 168
 169         return 0;
 170 }
 171
 172 static int klp_find_object_symbol(const char *objname, const char *name,
 173                                   unsigned long *addr)
 174 {
 175         struct klp_find_arg args = {
 176                 .objname = objname,
 177                 .name = name,
 178                 .addr = 0,
 179                 .count = 0
 180         };
 181
 182         mutex_lock(&module_mutex);
 183         kallsyms_on_each_symbol(klp_find_callback, &args);
 184         mutex_unlock(&module_mutex);
 185
 186         if (args.count == 0)
 187                 pr_err("symbol '%s' not found in symbol table\n", name);
 188         else if (args.count > 1)
 189                 pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n",
 190                        args.count, name, objname);
 191         else {
 192                 *addr = args.addr;
 193                 return 0;
 194         }
 195
 196         *addr = 0;
 197         return -EINVAL;
 198 }
 199
 200 struct klp_verify_args {
 201         const char *name;
 202         const unsigned long addr;
 203 };
 204
 205 static int klp_verify_callback(void *data, const char *name,
 206                                struct module *mod, unsigned long addr)
 207 {
 208         struct klp_verify_args *args = data;
 209
 210         if (!mod &&
 211             !strcmp(args->name, name) &&
 212             args->addr == addr)
 213                 return 1;
 214
 215         return 0;
 216 }
 217
 218 static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
 219 {
 220         struct klp_verify_args args = {
 221                 .name = name,
 222                 .addr = addr,
 223         };
 224         int ret;
 225
 226         mutex_lock(&module_mutex);
 227         ret = kallsyms_on_each_symbol(klp_verify_callback, &args);
 228         mutex_unlock(&module_mutex);
 229
 230         if (!ret) {
 231                 pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
 232                         name, addr);
 233                 return -EINVAL;
 234         }
 235
 236         return 0;
 237 }
 238
 239 static int klp_find_verify_func_addr(struct klp_object *obj,
 240                                      struct klp_func *func)
 241 {
 242         int ret;
 243
 244 #if defined(CONFIG_RANDOMIZE_BASE)
 245         /* If KASLR has been enabled, adjust old_addr accordingly */
 246         if (kaslr_enabled() && func->old_addr)
 247                 func->old_addr += kaslr_offset();
 248 #endif
 249
 250         if (!func->old_addr || klp_is_module(obj))
 251                 ret = klp_find_object_symbol(obj->name, func->old_name,
 252                                              &func->old_addr);
 253         else
 254                 ret = klp_verify_vmlinux_symbol(func->old_name,
 255                                                 func->old_addr);
 256
 257         return ret;
 258 }
 259
 260 /*
 261  * external symbols are located outside the parent object (where the parent
 262  * object is either vmlinux or the kmod being patched).
 263  */
 264 static int klp_find_external_symbol(struct module *pmod, const char *name,
 265                                     unsigned long *addr)
 266 {
 267         const struct kernel_symbol *sym;
 268
 269         /* first, check if it's an exported symbol */
 270         preempt_disable();
 271         sym = find_symbol(name, NULL, NULL, true, true);
 272         if (sym) {
 273                 *addr = sym->value;
 274                 preempt_enable();
 275                 return 0;
 276         }
 277         preempt_enable();
 278
 279         /* otherwise check if it's in another .o within the patch module */
 280         return klp_find_object_symbol(pmod->name, name, addr);
 281 }
 282
 283 static int klp_write_object_relocations(struct module *pmod,
 284                                         struct klp_object *obj)
 285 {
 286         int ret;
 287         struct klp_reloc *reloc;
 288
 289         if (WARN_ON(!klp_is_object_loaded(obj)))
 290                 return -EINVAL;
 291
 292         if (WARN_ON(!obj->relocs))
 293                 return -EINVAL;
 294
 295         for (reloc = obj->relocs; reloc->name; reloc++) {
 296                 if (!klp_is_module(obj)) {
 297                         ret = klp_verify_vmlinux_symbol(reloc->name,
 298                                                         reloc->val);
 299                         if (ret)
 300                                 return ret;
 301                 } else {
 302                         /* module, reloc->val needs to be discovered */
 303                         if (reloc->external)
 304                                 ret = klp_find_external_symbol(pmod,
 305                                                                reloc->name,
 306                                                                &reloc->val);
 307                         else
 308                                 ret = klp_find_object_symbol(obj->mod->name,
 309                                                              reloc->name,
 310                                                              &reloc->val);
 311                         if (ret)
 312                                 return ret;
 313                 }
 314                 ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
 315                                              reloc->val + reloc->addend);
 316                 if (ret) {
 317                         pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
 318                                reloc->name, reloc->val, ret);
 319                         return ret;
 320                 }
 321         }
 322
 323         return 0;
 324 }
 325
 326 static void notrace klp_ftrace_handler(unsigned long ip,
 327                                        unsigned long parent_ip,
 328                                        struct ftrace_ops *fops,
 329                                        struct pt_regs *regs)
 330 {
 331         struct klp_ops *ops;
 332         struct klp_func *func;
 333
 334         ops = container_of(fops, struct klp_ops, fops);
 335
 336         rcu_read_lock();
 337         func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
 338                                       stack_node);
 339         if (WARN_ON_ONCE(!func))
 340                 goto unlock;
 341
 342         klp_arch_set_pc(regs, (unsigned long)func->new_func);
 343 unlock:
 344         rcu_read_unlock();
 345 }
 346
 347 static void klp_disable_func(struct klp_func *func)
 348 {
 349         struct klp_ops *ops;
 350
 351         WARN_ON(func->state != KLP_ENABLED);
 352         WARN_ON(!func->old_addr);
 353
 354         ops = klp_find_ops(func->old_addr);
 355         if (WARN_ON(!ops))
 356                 return;
 357
 358         if (list_is_singular(&ops->func_stack)) {
 359                 WARN_ON(unregister_ftrace_function(&ops->fops));
 360                 WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
 361
 362                 list_del_rcu(&func->stack_node);
 363                 list_del(&ops->node);
 364                 kfree(ops);
 365         } else {
 366                 list_del_rcu(&func->stack_node);
 367         }
 368
 369         func->state = KLP_DISABLED;
 370 }
 371
 372 static int klp_enable_func(struct klp_func *func)
 373 {
 374         struct klp_ops *ops;
 375         int ret;
 376
 377         if (WARN_ON(!func->old_addr))
 378                 return -EINVAL;
 379
 380         if (WARN_ON(func->state != KLP_DISABLED))
 381                 return -EINVAL;
 382
 383         ops = klp_find_ops(func->old_addr);
 384         if (!ops) {
 385                 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
 386                 if (!ops)
 387                         return -ENOMEM;
 388
 389                 ops->fops.func = klp_ftrace_handler;
 390                 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
 391                                   FTRACE_OPS_FL_DYNAMIC |
 392                                   FTRACE_OPS_FL_IPMODIFY;
 393
 394                 list_add(&ops->node, &klp_ops);
 395
 396                 INIT_LIST_HEAD(&ops->func_stack);
 397                 list_add_rcu(&func->stack_node, &ops->func_stack);
 398
 399                 ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
 400                 if (ret) {
 401                         pr_err("failed to set ftrace filter for function '%s' (%d)\n",
 402                                func->old_name, ret);
 403                         goto err;
 404                 }
 405
 406                 ret = register_ftrace_function(&ops->fops);
 407                 if (ret) {
 408                         pr_err("failed to register ftrace handler for function '%s' (%d)\n",
 409                                func->old_name, ret);
 410                         ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
 411                         goto err;
 412                 }
 413
 414
 415         } else {
 416                 list_add_rcu(&func->stack_node, &ops->func_stack);
 417         }
 418
 419         func->state = KLP_ENABLED;
 420
 421         return 0;
 422
 423 err:
 424         list_del_rcu(&func->stack_node);
 425         list_del(&ops->node);
 426         kfree(ops);
 427         return ret;
 428 }
 429
 430 static void klp_disable_object(struct klp_object *obj)
 431 {
 432         struct klp_func *func;
 433
 434         klp_for_each_func(obj, func)
 435                 if (func->state == KLP_ENABLED)
 436                         klp_disable_func(func);
 437
 438         obj->state = KLP_DISABLED;
 439 }
 440
 441 static int klp_enable_object(struct klp_object *obj)
 442 {
 443         struct klp_func *func;
 444         int ret;
 445
 446         if (WARN_ON(obj->state != KLP_DISABLED))
 447                 return -EINVAL;
 448
 449         if (WARN_ON(!klp_is_object_loaded(obj)))
 450                 return -EINVAL;
 451
 452         klp_for_each_func(obj, func) {
 453                 ret = klp_enable_func(func);
 454                 if (ret) {
 455                         klp_disable_object(obj);
 456                         return ret;
 457                 }
 458         }
 459         obj->state = KLP_ENABLED;
 460
 461         return 0;
 462 }
 463
 464 static int __klp_disable_patch(struct klp_patch *patch)
 465 {
 466         struct klp_object *obj;
 467
 468         /* enforce stacking: only the last enabled patch can be disabled */
 469         if (!list_is_last(&patch->list, &klp_patches) &&
 470             list_next_entry(patch, list)->state == KLP_ENABLED)
 471                 return -EBUSY;
 472
 473         pr_notice("disabling patch '%s'\n", patch->mod->name);
 474
 475         klp_for_each_object(patch, obj) {
 476                 if (obj->state == KLP_ENABLED)
 477                         klp_disable_object(obj);
 478         }
 479
 480         patch->state = KLP_DISABLED;
 481
 482         return 0;
 483 }
 484
 485 /**
 486  * klp_disable_patch() - disables a registered patch
 487  * @patch:      The registered, enabled patch to be disabled
 488  *
 489  * Unregisters the patched functions from ftrace.
 490  *
 491  * Return: 0 on success, otherwise error
 492  */
 493 int klp_disable_patch(struct klp_patch *patch)
 494 {
 495         int ret;
 496
 497         mutex_lock(&klp_mutex);
 498
 499         if (!klp_is_patch_registered(patch)) {
 500                 ret = -EINVAL;
 501                 goto err;
 502         }
 503
 504         if (patch->state == KLP_DISABLED) {
 505                 ret = -EINVAL;
 506                 goto err;
 507         }
 508
 509         ret = __klp_disable_patch(patch);
 510
 511 err:
 512         mutex_unlock(&klp_mutex);
 513         return ret;
 514 }
 515 EXPORT_SYMBOL_GPL(klp_disable_patch);
 516
 517 static int __klp_enable_patch(struct klp_patch *patch)
 518 {
 519         struct klp_object *obj;
 520         int ret;
 521
 522         if (WARN_ON(patch->state != KLP_DISABLED))
 523                 return -EINVAL;
 524
 525         /* enforce stacking: only the first disabled patch can be enabled */
 526         if (patch->list.prev != &klp_patches &&
 527             list_prev_entry(patch, list)->state == KLP_DISABLED)
 528                 return -EBUSY;
 529
 530         pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
 531         add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
 532
 533         pr_notice("enabling patch '%s'\n", patch->mod->name);
 534
 535         klp_for_each_object(patch, obj) {
 536                 if (!klp_is_object_loaded(obj))
 537                         continue;
 538
 539                 ret = klp_enable_object(obj);
 540                 if (ret)
 541                         goto unregister;
 542         }
 543
 544         patch->state = KLP_ENABLED;
 545
 546         return 0;
 547
 548 unregister:
 549         WARN_ON(__klp_disable_patch(patch));
 550         return ret;
 551 }
 552
 553 /**
 554  * klp_enable_patch() - enables a registered patch
 555  * @patch:      The registered, disabled patch to be enabled
 556  *
 557  * Performs the needed symbol lookups and code relocations,
 558  * then registers the patched functions with ftrace.
 559  *
 560  * Return: 0 on success, otherwise error
 561  */
 562 int klp_enable_patch(struct klp_patch *patch)
 563 {
 564         int ret;
 565
 566         mutex_lock(&klp_mutex);
 567
 568         if (!klp_is_patch_registered(patch)) {
 569                 ret = -EINVAL;
 570                 goto err;
 571         }
 572
 573         ret = __klp_enable_patch(patch);
 574
 575 err:
 576         mutex_unlock(&klp_mutex);
 577         return ret;
 578 }
 579 EXPORT_SYMBOL_GPL(klp_enable_patch);
 580
 581 /*
 582  * Sysfs Interface
 583  *
 584  * /sys/kernel/livepatch
 585  * /sys/kernel/livepatch/<patch>
 586  * /sys/kernel/livepatch/<patch>/enabled
 587  * /sys/kernel/livepatch/<patch>/<object>
 588  * /sys/kernel/livepatch/<patch>/<object>/<func>
 589  */
 590
 591 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 592                              const char *buf, size_t count)
 593 {
 594         struct klp_patch *patch;
 595         int ret;
 596         unsigned long val;
 597
 598         ret = kstrtoul(buf, 10, &val);
 599         if (ret)
 600                 return -EINVAL;
 601
 602         if (val != KLP_DISABLED && val != KLP_ENABLED)
 603                 return -EINVAL;
 604
 605         patch = container_of(kobj, struct klp_patch, kobj);
 606
 607         mutex_lock(&klp_mutex);
 608
 609         if (val == patch->state) {
 610                 /* already in requested state */
 611                 ret = -EINVAL;
 612                 goto err;
 613         }
 614
 615         if (val == KLP_ENABLED) {
 616                 ret = __klp_enable_patch(patch);
 617                 if (ret)
 618                         goto err;
 619         } else {
 620                 ret = __klp_disable_patch(patch);
 621                 if (ret)
 622                         goto err;
 623         }
 624
 625         mutex_unlock(&klp_mutex);
 626
 627         return count;
 628
 629 err:
 630         mutex_unlock(&klp_mutex);
 631         return ret;
 632 }
 633
 634 static ssize_t enabled_show(struct kobject *kobj,
 635                             struct kobj_attribute *attr, char *buf)
 636 {
 637         struct klp_patch *patch;
 638
 639         patch = container_of(kobj, struct klp_patch, kobj);
 640         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
 641 }
 642
 643 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 644 static struct attribute *klp_patch_attrs[] = {
 645         &enabled_kobj_attr.attr,
 646         NULL
 647 };
 648
 649 static void klp_kobj_release_patch(struct kobject *kobj)
 650 {
 651         /*
 652          * Once we have a consistency model we'll need to module_put() the
 653          * patch module here.  See klp_register_patch() for more details.
 654          */
 655 }
 656
 657 static struct kobj_type klp_ktype_patch = {
 658         .release = klp_kobj_release_patch,
 659         .sysfs_ops = &kobj_sysfs_ops,
 660         .default_attrs = klp_patch_attrs,
 661 };
 662
 663 static void klp_kobj_release_object(struct kobject *kobj)
 664 {
 665 }
 666
 667 static struct kobj_type klp_ktype_object = {
 668         .release = klp_kobj_release_object,
 669         .sysfs_ops = &kobj_sysfs_ops,
 670 };
 671
 672 static void klp_kobj_release_func(struct kobject *kobj)
 673 {
 674 }
 675
 676 static struct kobj_type klp_ktype_func = {
 677         .release = klp_kobj_release_func,
 678         .sysfs_ops = &kobj_sysfs_ops,
 679 };
 680
 681 /*
 682  * Free all functions' kobjects in the array up to some limit. When limit is
 683  * NULL, all kobjects are freed.
 684  */
 685 static void klp_free_funcs_limited(struct klp_object *obj,
 686                                    struct klp_func *limit)
 687 {
 688         struct klp_func *func;
 689
 690         for (func = obj->funcs; func->old_name && func != limit; func++)
 691                 kobject_put(&func->kobj);
 692 }
 693
 694 /* Clean up when a patched object is unloaded */
 695 static void klp_free_object_loaded(struct klp_object *obj)
 696 {
 697         struct klp_func *func;
 698
 699         obj->mod = NULL;
 700
 701         klp_for_each_func(obj, func)
 702                 func->old_addr = 0;
 703 }
 704
 705 /*
 706  * Free all objects' kobjects in the array up to some limit. When limit is
 707  * NULL, all kobjects are freed.
 708  */
 709 static void klp_free_objects_limited(struct klp_patch *patch,
 710                                      struct klp_object *limit)
 711 {
 712         struct klp_object *obj;
 713
 714         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 715                 klp_free_funcs_limited(obj, NULL);
 716                 kobject_put(&obj->kobj);
 717         }
 718 }
 719
 720 static void klp_free_patch(struct klp_patch *patch)
 721 {
 722         klp_free_objects_limited(patch, NULL);
 723         if (!list_empty(&patch->list))
 724                 list_del(&patch->list);
 725         kobject_put(&patch->kobj);
 726 }
 727
 728 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 729 {
 730         INIT_LIST_HEAD(&func->stack_node);
 731         func->state = KLP_DISABLED;
 732
 733         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 734                                     &obj->kobj, "%s", func->old_name);
 735 }
 736
 737 /* parts of the initialization that is done only when the object is loaded */
 738 static int klp_init_object_loaded(struct klp_patch *patch,
 739                                   struct klp_object *obj)
 740 {
 741         struct klp_func *func;
 742         int ret;
 743
 744         if (obj->relocs) {
 745                 ret = klp_write_object_relocations(patch->mod, obj);
 746                 if (ret)
 747                         return ret;
 748         }
 749
 750         klp_for_each_func(obj, func) {
 751                 ret = klp_find_verify_func_addr(obj, func);
 752                 if (ret)
 753                         return ret;
 754         }
 755
 756         return 0;
 757 }
 758
 759 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 760 {
 761         struct klp_func *func;
 762         int ret;
 763         const char *name;
 764
 765         if (!obj->funcs)
 766                 return -EINVAL;
 767
 768         obj->state = KLP_DISABLED;
 769         obj->mod = NULL;
 770
 771         klp_find_object_module(obj);
 772
 773         name = klp_is_module(obj) ? obj->name : "vmlinux";
 774         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
 775                                    &patch->kobj, "%s", name);
 776         if (ret)
 777                 return ret;
 778
 779         klp_for_each_func(obj, func) {
 780                 ret = klp_init_func(obj, func);
 781                 if (ret)
 782                         goto free;
 783         }
 784
 785         if (klp_is_object_loaded(obj)) {
 786                 ret = klp_init_object_loaded(patch, obj);
 787                 if (ret)
 788                         goto free;
 789         }
 790
 791         return 0;
 792
 793 free:
 794         klp_free_funcs_limited(obj, func);
 795         kobject_put(&obj->kobj);
 796         return ret;
 797 }
 798
 799 static int klp_init_patch(struct klp_patch *patch)
 800 {
 801         struct klp_object *obj;
 802         int ret;
 803
 804         if (!patch->objs)
 805                 return -EINVAL;
 806
 807         mutex_lock(&klp_mutex);
 808
 809         patch->state = KLP_DISABLED;
 810
 811         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 812                                    klp_root_kobj, "%s", patch->mod->name);
 813         if (ret)
 814                 goto unlock;
 815
 816         klp_for_each_object(patch, obj) {
 817                 ret = klp_init_object(patch, obj);
 818                 if (ret)
 819                         goto free;
 820         }
 821
 822         list_add_tail(&patch->list, &klp_patches);
 823
 824         mutex_unlock(&klp_mutex);
 825
 826         return 0;
 827
 828 free:
 829         klp_free_objects_limited(patch, obj);
 830         kobject_put(&patch->kobj);
 831 unlock:
 832         mutex_unlock(&klp_mutex);
 833         return ret;
 834 }
 835
 836 /**
 837  * klp_unregister_patch() - unregisters a patch
 838  * @patch:      Disabled patch to be unregistered
 839  *
 840  * Frees the data structures and removes the sysfs interface.
 841  *
 842  * Return: 0 on success, otherwise error
 843  */
 844 int klp_unregister_patch(struct klp_patch *patch)
 845 {
 846         int ret = 0;
 847
 848         mutex_lock(&klp_mutex);
 849
 850         if (!klp_is_patch_registered(patch)) {
 851                 ret = -EINVAL;
 852                 goto out;
 853         }
 854
 855         if (patch->state == KLP_ENABLED) {
 856                 ret = -EBUSY;
 857                 goto out;
 858         }
 859
 860         klp_free_patch(patch);
 861
 862 out:
 863         mutex_unlock(&klp_mutex);
 864         return ret;
 865 }
 866 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 867
 868 /**
 869  * klp_register_patch() - registers a patch
 870  * @patch:      Patch to be registered
 871  *
 872  * Initializes the data structure associated with the patch and
 873  * creates the sysfs interface.
 874  *
 875  * Return: 0 on success, otherwise error
 876  */
 877 int klp_register_patch(struct klp_patch *patch)
 878 {
 879         int ret;
 880
 881         if (!klp_initialized())
 882                 return -ENODEV;
 883
 884         if (!patch || !patch->mod)
 885                 return -EINVAL;
 886
 887         /*
 888          * A reference is taken on the patch module to prevent it from being
 889          * unloaded.  Right now, we don't allow patch modules to unload since
 890          * there is currently no method to determine if a thread is still
 891          * running in the patched code contained in the patch module once
 892          * the ftrace registration is successful.
 893          */
 894         if (!try_module_get(patch->mod))
 895                 return -ENODEV;
 896
 897         ret = klp_init_patch(patch);
 898         if (ret)
 899                 module_put(patch->mod);
 900
 901         return ret;
 902 }
 903 EXPORT_SYMBOL_GPL(klp_register_patch);
 904
 905 static int klp_module_notify_coming(struct klp_patch *patch,
 906                                      struct klp_object *obj)
 907 {
 908         struct module *pmod = patch->mod;
 909         struct module *mod = obj->mod;
 910         int ret;
 911
 912         ret = klp_init_object_loaded(patch, obj);
 913         if (ret) {
 914                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
 915                         pmod->name, mod->name, ret);
 916                 return ret;
 917         }
 918
 919         if (patch->state == KLP_DISABLED)
 920                 return 0;
 921
 922         pr_notice("applying patch '%s' to loading module '%s'\n",
 923                   pmod->name, mod->name);
 924
 925         ret = klp_enable_object(obj);
 926         if (ret)
 927                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 928                         pmod->name, mod->name, ret);
 929         return ret;
 930 }
 931
 932 static void klp_module_notify_going(struct klp_patch *patch,
 933                                     struct klp_object *obj)
 934 {
 935         struct module *pmod = patch->mod;
 936         struct module *mod = obj->mod;
 937
 938         if (patch->state == KLP_DISABLED)
 939                 goto disabled;
 940
 941         pr_notice("reverting patch '%s' on unloading module '%s'\n",
 942                   pmod->name, mod->name);
 943
 944         klp_disable_object(obj);
 945
 946 disabled:
 947         klp_free_object_loaded(obj);
 948 }
 949
 950 static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 951                              void *data)
 952 {
 953         int ret;
 954         struct module *mod = data;
 955         struct klp_patch *patch;
 956         struct klp_object *obj;
 957
 958         if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
 959                 return 0;
 960
 961         mutex_lock(&klp_mutex);
 962
 963         /*
 964          * Each module has to know that the notifier has been called.
 965          * We never know what module will get patched by a new patch.
 966          */
 967         if (action == MODULE_STATE_COMING)
 968                 mod->klp_alive = true;
 969         else /* MODULE_STATE_GOING */
 970                 mod->klp_alive = false;
 971
 972         list_for_each_entry(patch, &klp_patches, list) {
 973                 klp_for_each_object(patch, obj) {
 974                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 975                                 continue;
 976
 977                         if (action == MODULE_STATE_COMING) {
 978                                 obj->mod = mod;
 979                                 ret = klp_module_notify_coming(patch, obj);
 980                                 if (ret) {
 981                                         obj->mod = NULL;
 982                                         pr_warn("patch '%s' is in an inconsistent state!\n",
 983                                                 patch->mod->name);
 984                                 }
 985                         } else /* MODULE_STATE_GOING */
 986                                 klp_module_notify_going(patch, obj);
 987
 988                         break;
 989                 }
 990         }
 991
 992         mutex_unlock(&klp_mutex);
 993
 994         return 0;
 995 }
 996
 997 static struct notifier_block klp_module_nb = {
 998         .notifier_call = klp_module_notify,
 999         .priority = INT_MIN+1, /* called late but before ftrace notifier */
1000 };
1001
1002 static int __init klp_init(void)
1003 {
1004         int ret;
1005
1006         ret = klp_check_compiler_support();
1007         if (ret) {
1008                 pr_info("Your compiler is too old; turning off.\n");
1009                 return -EINVAL;
1010         }
1011
1012         ret = register_module_notifier(&klp_module_nb);
1013         if (ret)
1014                 return ret;
1015
1016         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1017         if (!klp_root_kobj) {
1018                 ret = -ENOMEM;
1019                 goto unregister;
1020         }
1021
1022         return 0;
1023
1024 unregister:
1025         unregister_module_notifier(&klp_module_nb);
1026         return ret;
1027 }
1028
1029 module_init(klp_init);