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         kallsyms_on_each_symbol(klp_find_callback, &args);
 183
 184         if (args.count == 0)
 185                 pr_err("symbol '%s' not found in symbol table\n", name);
 186         else if (args.count > 1)
 187                 pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n",
 188                        args.count, name, objname);
 189         else {
 190                 *addr = args.addr;
 191                 return 0;
 192         }
 193
 194         *addr = 0;
 195         return -EINVAL;
 196 }
 197
 198 struct klp_verify_args {
 199         const char *name;
 200         const unsigned long addr;
 201 };
 202
 203 static int klp_verify_callback(void *data, const char *name,
 204                                struct module *mod, unsigned long addr)
 205 {
 206         struct klp_verify_args *args = data;
 207
 208         if (!mod &&
 209             !strcmp(args->name, name) &&
 210             args->addr == addr)
 211                 return 1;
 212
 213         return 0;
 214 }
 215
 216 static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
 217 {
 218         struct klp_verify_args args = {
 219                 .name = name,
 220                 .addr = addr,
 221         };
 222
 223         if (kallsyms_on_each_symbol(klp_verify_callback, &args))
 224                 return 0;
 225
 226         pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
 227                 name, addr);
 228         return -EINVAL;
 229 }
 230
 231 static int klp_find_verify_func_addr(struct klp_object *obj,
 232                                      struct klp_func *func)
 233 {
 234         int ret;
 235
 236 #if defined(CONFIG_RANDOMIZE_BASE)
 237         /* KASLR is enabled, disregard old_addr from user */
 238         func->old_addr = 0;
 239 #endif
 240
 241         if (!func->old_addr || klp_is_module(obj))
 242                 ret = klp_find_object_symbol(obj->name, func->old_name,
 243                                              &func->old_addr);
 244         else
 245                 ret = klp_verify_vmlinux_symbol(func->old_name,
 246                                                 func->old_addr);
 247
 248         return ret;
 249 }
 250
 251 /*
 252  * external symbols are located outside the parent object (where the parent
 253  * object is either vmlinux or the kmod being patched).
 254  */
 255 static int klp_find_external_symbol(struct module *pmod, const char *name,
 256                                     unsigned long *addr)
 257 {
 258         const struct kernel_symbol *sym;
 259
 260         /* first, check if it's an exported symbol */
 261         preempt_disable();
 262         sym = find_symbol(name, NULL, NULL, true, true);
 263         if (sym) {
 264                 *addr = sym->value;
 265                 preempt_enable();
 266                 return 0;
 267         }
 268         preempt_enable();
 269
 270         /* otherwise check if it's in another .o within the patch module */
 271         return klp_find_object_symbol(pmod->name, name, addr);
 272 }
 273
 274 static int klp_write_object_relocations(struct module *pmod,
 275                                         struct klp_object *obj)
 276 {
 277         int ret;
 278         struct klp_reloc *reloc;
 279
 280         if (WARN_ON(!klp_is_object_loaded(obj)))
 281                 return -EINVAL;
 282
 283         if (WARN_ON(!obj->relocs))
 284                 return -EINVAL;
 285
 286         for (reloc = obj->relocs; reloc->name; reloc++) {
 287                 if (!klp_is_module(obj)) {
 288                         ret = klp_verify_vmlinux_symbol(reloc->name,
 289                                                         reloc->val);
 290                         if (ret)
 291                                 return ret;
 292                 } else {
 293                         /* module, reloc->val needs to be discovered */
 294                         if (reloc->external)
 295                                 ret = klp_find_external_symbol(pmod,
 296                                                                reloc->name,
 297                                                                &reloc->val);
 298                         else
 299                                 ret = klp_find_object_symbol(obj->mod->name,
 300                                                              reloc->name,
 301                                                              &reloc->val);
 302                         if (ret)
 303                                 return ret;
 304                 }
 305                 ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
 306                                              reloc->val + reloc->addend);
 307                 if (ret) {
 308                         pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
 309                                reloc->name, reloc->val, ret);
 310                         return ret;
 311                 }
 312         }
 313
 314         return 0;
 315 }
 316
 317 static void notrace klp_ftrace_handler(unsigned long ip,
 318                                        unsigned long parent_ip,
 319                                        struct ftrace_ops *fops,
 320                                        struct pt_regs *regs)
 321 {
 322         struct klp_ops *ops;
 323         struct klp_func *func;
 324
 325         ops = container_of(fops, struct klp_ops, fops);
 326
 327         rcu_read_lock();
 328         func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
 329                                       stack_node);
 330         if (WARN_ON_ONCE(!func))
 331                 goto unlock;
 332
 333         klp_arch_set_pc(regs, (unsigned long)func->new_func);
 334 unlock:
 335         rcu_read_unlock();
 336 }
 337
 338 static int klp_disable_func(struct klp_func *func)
 339 {
 340         struct klp_ops *ops;
 341         int ret;
 342
 343         if (WARN_ON(func->state != KLP_ENABLED))
 344                 return -EINVAL;
 345
 346         if (WARN_ON(!func->old_addr))
 347                 return -EINVAL;
 348
 349         ops = klp_find_ops(func->old_addr);
 350         if (WARN_ON(!ops))
 351                 return -EINVAL;
 352
 353         if (list_is_singular(&ops->func_stack)) {
 354                 ret = unregister_ftrace_function(&ops->fops);
 355                 if (ret) {
 356                         pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
 357                                func->old_name, ret);
 358                         return ret;
 359                 }
 360
 361                 ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
 362                 if (ret)
 363                         pr_warn("function unregister succeeded but failed to clear the filter\n");
 364
 365                 list_del_rcu(&func->stack_node);
 366                 list_del(&ops->node);
 367                 kfree(ops);
 368         } else {
 369                 list_del_rcu(&func->stack_node);
 370         }
 371
 372         func->state = KLP_DISABLED;
 373
 374         return 0;
 375 }
 376
 377 static int klp_enable_func(struct klp_func *func)
 378 {
 379         struct klp_ops *ops;
 380         int ret;
 381
 382         if (WARN_ON(!func->old_addr))
 383                 return -EINVAL;
 384
 385         if (WARN_ON(func->state != KLP_DISABLED))
 386                 return -EINVAL;
 387
 388         ops = klp_find_ops(func->old_addr);
 389         if (!ops) {
 390                 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
 391                 if (!ops)
 392                         return -ENOMEM;
 393
 394                 ops->fops.func = klp_ftrace_handler;
 395                 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
 396                                   FTRACE_OPS_FL_DYNAMIC |
 397                                   FTRACE_OPS_FL_IPMODIFY;
 398
 399                 list_add(&ops->node, &klp_ops);
 400
 401                 INIT_LIST_HEAD(&ops->func_stack);
 402                 list_add_rcu(&func->stack_node, &ops->func_stack);
 403
 404                 ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
 405                 if (ret) {
 406                         pr_err("failed to set ftrace filter for function '%s' (%d)\n",
 407                                func->old_name, ret);
 408                         goto err;
 409                 }
 410
 411                 ret = register_ftrace_function(&ops->fops);
 412                 if (ret) {
 413                         pr_err("failed to register ftrace handler for function '%s' (%d)\n",
 414                                func->old_name, ret);
 415                         ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
 416                         goto err;
 417                 }
 418
 419
 420         } else {
 421                 list_add_rcu(&func->stack_node, &ops->func_stack);
 422         }
 423
 424         func->state = KLP_ENABLED;
 425
 426         return 0;
 427
 428 err:
 429         list_del_rcu(&func->stack_node);
 430         list_del(&ops->node);
 431         kfree(ops);
 432         return ret;
 433 }
 434
 435 static int klp_disable_object(struct klp_object *obj)
 436 {
 437         struct klp_func *func;
 438         int ret;
 439
 440         for (func = obj->funcs; func->old_name; func++) {
 441                 if (func->state != KLP_ENABLED)
 442                         continue;
 443
 444                 ret = klp_disable_func(func);
 445                 if (ret)
 446                         return ret;
 447         }
 448
 449         obj->state = KLP_DISABLED;
 450
 451         return 0;
 452 }
 453
 454 static int klp_enable_object(struct klp_object *obj)
 455 {
 456         struct klp_func *func;
 457         int ret;
 458
 459         if (WARN_ON(obj->state != KLP_DISABLED))
 460                 return -EINVAL;
 461
 462         if (WARN_ON(!klp_is_object_loaded(obj)))
 463                 return -EINVAL;
 464
 465         for (func = obj->funcs; func->old_name; func++) {
 466                 ret = klp_enable_func(func);
 467                 if (ret)
 468                         goto unregister;
 469         }
 470         obj->state = KLP_ENABLED;
 471
 472         return 0;
 473
 474 unregister:
 475         WARN_ON(klp_disable_object(obj));
 476         return ret;
 477 }
 478
 479 static int __klp_disable_patch(struct klp_patch *patch)
 480 {
 481         struct klp_object *obj;
 482         int ret;
 483
 484         /* enforce stacking: only the last enabled patch can be disabled */
 485         if (!list_is_last(&patch->list, &klp_patches) &&
 486             list_next_entry(patch, list)->state == KLP_ENABLED)
 487                 return -EBUSY;
 488
 489         pr_notice("disabling patch '%s'\n", patch->mod->name);
 490
 491         for (obj = patch->objs; obj->funcs; obj++) {
 492                 if (obj->state != KLP_ENABLED)
 493                         continue;
 494
 495                 ret = klp_disable_object(obj);
 496                 if (ret)
 497                         return ret;
 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         for (obj = patch->objs; obj->funcs; obj++) {
 556                 klp_find_object_module(obj);
 557
 558                 if (!klp_is_object_loaded(obj))
 559                         continue;
 560
 561                 ret = klp_enable_object(obj);
 562                 if (ret)
 563                         goto unregister;
 564         }
 565
 566         patch->state = KLP_ENABLED;
 567
 568         return 0;
 569
 570 unregister:
 571         WARN_ON(__klp_disable_patch(patch));
 572         return ret;
 573 }
 574
 575 /**
 576  * klp_enable_patch() - enables a registered patch
 577  * @patch:      The registered, disabled patch to be enabled
 578  *
 579  * Performs the needed symbol lookups and code relocations,
 580  * then registers the patched functions with ftrace.
 581  *
 582  * Return: 0 on success, otherwise error
 583  */
 584 int klp_enable_patch(struct klp_patch *patch)
 585 {
 586         int ret;
 587
 588         mutex_lock(&klp_mutex);
 589
 590         if (!klp_is_patch_registered(patch)) {
 591                 ret = -EINVAL;
 592                 goto err;
 593         }
 594
 595         ret = __klp_enable_patch(patch);
 596
 597 err:
 598         mutex_unlock(&klp_mutex);
 599         return ret;
 600 }
 601 EXPORT_SYMBOL_GPL(klp_enable_patch);
 602
 603 /*
 604  * Sysfs Interface
 605  *
 606  * /sys/kernel/livepatch
 607  * /sys/kernel/livepatch/<patch>
 608  * /sys/kernel/livepatch/<patch>/enabled
 609  * /sys/kernel/livepatch/<patch>/<object>
 610  * /sys/kernel/livepatch/<patch>/<object>/<func>
 611  */
 612
 613 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 614                              const char *buf, size_t count)
 615 {
 616         struct klp_patch *patch;
 617         int ret;
 618         unsigned long val;
 619
 620         ret = kstrtoul(buf, 10, &val);
 621         if (ret)
 622                 return -EINVAL;
 623
 624         if (val != KLP_DISABLED && val != KLP_ENABLED)
 625                 return -EINVAL;
 626
 627         patch = container_of(kobj, struct klp_patch, kobj);
 628
 629         mutex_lock(&klp_mutex);
 630
 631         if (val == patch->state) {
 632                 /* already in requested state */
 633                 ret = -EINVAL;
 634                 goto err;
 635         }
 636
 637         if (val == KLP_ENABLED) {
 638                 ret = __klp_enable_patch(patch);
 639                 if (ret)
 640                         goto err;
 641         } else {
 642                 ret = __klp_disable_patch(patch);
 643                 if (ret)
 644                         goto err;
 645         }
 646
 647         mutex_unlock(&klp_mutex);
 648
 649         return count;
 650
 651 err:
 652         mutex_unlock(&klp_mutex);
 653         return ret;
 654 }
 655
 656 static ssize_t enabled_show(struct kobject *kobj,
 657                             struct kobj_attribute *attr, char *buf)
 658 {
 659         struct klp_patch *patch;
 660
 661         patch = container_of(kobj, struct klp_patch, kobj);
 662         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
 663 }
 664
 665 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 666 static struct attribute *klp_patch_attrs[] = {
 667         &enabled_kobj_attr.attr,
 668         NULL
 669 };
 670
 671 static void klp_kobj_release_patch(struct kobject *kobj)
 672 {
 673         /*
 674          * Once we have a consistency model we'll need to module_put() the
 675          * patch module here.  See klp_register_patch() for more details.
 676          */
 677 }
 678
 679 static struct kobj_type klp_ktype_patch = {
 680         .release = klp_kobj_release_patch,
 681         .sysfs_ops = &kobj_sysfs_ops,
 682         .default_attrs = klp_patch_attrs,
 683 };
 684
 685 static void klp_kobj_release_func(struct kobject *kobj)
 686 {
 687 }
 688
 689 static struct kobj_type klp_ktype_func = {
 690         .release = klp_kobj_release_func,
 691         .sysfs_ops = &kobj_sysfs_ops,
 692 };
 693
 694 /*
 695  * Free all functions' kobjects in the array up to some limit. When limit is
 696  * NULL, all kobjects are freed.
 697  */
 698 static void klp_free_funcs_limited(struct klp_object *obj,
 699                                    struct klp_func *limit)
 700 {
 701         struct klp_func *func;
 702
 703         for (func = obj->funcs; func->old_name && func != limit; func++)
 704                 kobject_put(&func->kobj);
 705 }
 706
 707 /* Clean up when a patched object is unloaded */
 708 static void klp_free_object_loaded(struct klp_object *obj)
 709 {
 710         struct klp_func *func;
 711
 712         obj->mod = NULL;
 713
 714         for (func = obj->funcs; func->old_name; func++)
 715                 func->old_addr = 0;
 716 }
 717
 718 /*
 719  * Free all objects' kobjects in the array up to some limit. When limit is
 720  * NULL, all kobjects are freed.
 721  */
 722 static void klp_free_objects_limited(struct klp_patch *patch,
 723                                      struct klp_object *limit)
 724 {
 725         struct klp_object *obj;
 726
 727         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 728                 klp_free_funcs_limited(obj, NULL);
 729                 kobject_put(obj->kobj);
 730         }
 731 }
 732
 733 static void klp_free_patch(struct klp_patch *patch)
 734 {
 735         klp_free_objects_limited(patch, NULL);
 736         if (!list_empty(&patch->list))
 737                 list_del(&patch->list);
 738         kobject_put(&patch->kobj);
 739 }
 740
 741 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 742 {
 743         INIT_LIST_HEAD(&func->stack_node);
 744         func->state = KLP_DISABLED;
 745
 746         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 747                                     obj->kobj, "%s", func->old_name);
 748 }
 749
 750 /* parts of the initialization that is done only when the object is loaded */
 751 static int klp_init_object_loaded(struct klp_patch *patch,
 752                                   struct klp_object *obj)
 753 {
 754         struct klp_func *func;
 755         int ret;
 756
 757         if (obj->relocs) {
 758                 ret = klp_write_object_relocations(patch->mod, obj);
 759                 if (ret)
 760                         return ret;
 761         }
 762
 763         for (func = obj->funcs; func->old_name; func++) {
 764                 ret = klp_find_verify_func_addr(obj, func);
 765                 if (ret)
 766                         return ret;
 767         }
 768
 769         return 0;
 770 }
 771
 772 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 773 {
 774         struct klp_func *func;
 775         int ret;
 776         const char *name;
 777
 778         if (!obj->funcs)
 779                 return -EINVAL;
 780
 781         obj->state = KLP_DISABLED;
 782         obj->mod = NULL;
 783
 784         klp_find_object_module(obj);
 785
 786         name = klp_is_module(obj) ? obj->name : "vmlinux";
 787         obj->kobj = kobject_create_and_add(name, &patch->kobj);
 788         if (!obj->kobj)
 789                 return -ENOMEM;
 790
 791         for (func = obj->funcs; func->old_name; func++) {
 792                 ret = klp_init_func(obj, func);
 793                 if (ret)
 794                         goto free;
 795         }
 796
 797         if (klp_is_object_loaded(obj)) {
 798                 ret = klp_init_object_loaded(patch, obj);
 799                 if (ret)
 800                         goto free;
 801         }
 802
 803         return 0;
 804
 805 free:
 806         klp_free_funcs_limited(obj, func);
 807         kobject_put(obj->kobj);
 808         return ret;
 809 }
 810
 811 static int klp_init_patch(struct klp_patch *patch)
 812 {
 813         struct klp_object *obj;
 814         int ret;
 815
 816         if (!patch->objs)
 817                 return -EINVAL;
 818
 819         mutex_lock(&klp_mutex);
 820
 821         patch->state = KLP_DISABLED;
 822
 823         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 824                                    klp_root_kobj, "%s", patch->mod->name);
 825         if (ret)
 826                 goto unlock;
 827
 828         for (obj = patch->objs; obj->funcs; obj++) {
 829                 ret = klp_init_object(patch, obj);
 830                 if (ret)
 831                         goto free;
 832         }
 833
 834         list_add_tail(&patch->list, &klp_patches);
 835
 836         mutex_unlock(&klp_mutex);
 837
 838         return 0;
 839
 840 free:
 841         klp_free_objects_limited(patch, obj);
 842         kobject_put(&patch->kobj);
 843 unlock:
 844         mutex_unlock(&klp_mutex);
 845         return ret;
 846 }
 847
 848 /**
 849  * klp_unregister_patch() - unregisters a patch
 850  * @patch:      Disabled patch to be unregistered
 851  *
 852  * Frees the data structures and removes the sysfs interface.
 853  *
 854  * Return: 0 on success, otherwise error
 855  */
 856 int klp_unregister_patch(struct klp_patch *patch)
 857 {
 858         int ret = 0;
 859
 860         mutex_lock(&klp_mutex);
 861
 862         if (!klp_is_patch_registered(patch)) {
 863                 ret = -EINVAL;
 864                 goto out;
 865         }
 866
 867         if (patch->state == KLP_ENABLED) {
 868                 ret = -EBUSY;
 869                 goto out;
 870         }
 871
 872         klp_free_patch(patch);
 873
 874 out:
 875         mutex_unlock(&klp_mutex);
 876         return ret;
 877 }
 878 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 879
 880 /**
 881  * klp_register_patch() - registers a patch
 882  * @patch:      Patch to be registered
 883  *
 884  * Initializes the data structure associated with the patch and
 885  * creates the sysfs interface.
 886  *
 887  * Return: 0 on success, otherwise error
 888  */
 889 int klp_register_patch(struct klp_patch *patch)
 890 {
 891         int ret;
 892
 893         if (!klp_initialized())
 894                 return -ENODEV;
 895
 896         if (!patch || !patch->mod)
 897                 return -EINVAL;
 898
 899         /*
 900          * A reference is taken on the patch module to prevent it from being
 901          * unloaded.  Right now, we don't allow patch modules to unload since
 902          * there is currently no method to determine if a thread is still
 903          * running in the patched code contained in the patch module once
 904          * the ftrace registration is successful.
 905          */
 906         if (!try_module_get(patch->mod))
 907                 return -ENODEV;
 908
 909         ret = klp_init_patch(patch);
 910         if (ret)
 911                 module_put(patch->mod);
 912
 913         return ret;
 914 }
 915 EXPORT_SYMBOL_GPL(klp_register_patch);
 916
 917 static void klp_module_notify_coming(struct klp_patch *patch,
 918                                      struct klp_object *obj)
 919 {
 920         struct module *pmod = patch->mod;
 921         struct module *mod = obj->mod;
 922         int ret;
 923
 924         ret = klp_init_object_loaded(patch, obj);
 925         if (ret)
 926                 goto err;
 927
 928         if (patch->state == KLP_DISABLED)
 929                 return;
 930
 931         pr_notice("applying patch '%s' to loading module '%s'\n",
 932                   pmod->name, mod->name);
 933
 934         ret = klp_enable_object(obj);
 935         if (!ret)
 936                 return;
 937
 938 err:
 939         pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 940                 pmod->name, mod->name, ret);
 941 }
 942
 943 static void klp_module_notify_going(struct klp_patch *patch,
 944                                     struct klp_object *obj)
 945 {
 946         struct module *pmod = patch->mod;
 947         struct module *mod = obj->mod;
 948         int ret;
 949
 950         if (patch->state == KLP_DISABLED)
 951                 goto disabled;
 952
 953         pr_notice("reverting patch '%s' on unloading module '%s'\n",
 954                   pmod->name, mod->name);
 955
 956         ret = klp_disable_object(obj);
 957         if (ret)
 958                 pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
 959                         pmod->name, mod->name, ret);
 960
 961 disabled:
 962         klp_free_object_loaded(obj);
 963 }
 964
 965 static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 966                              void *data)
 967 {
 968         struct module *mod = data;
 969         struct klp_patch *patch;
 970         struct klp_object *obj;
 971
 972         if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
 973                 return 0;
 974
 975         mutex_lock(&klp_mutex);
 976
 977         /*
 978          * Each module has to know that the notifier has been called.
 979          * We never know what module will get patched by a new patch.
 980          */
 981         if (action == MODULE_STATE_COMING)
 982                 mod->klp_alive = true;
 983         else /* MODULE_STATE_GOING */
 984                 mod->klp_alive = false;
 985
 986         list_for_each_entry(patch, &klp_patches, list) {
 987                 for (obj = patch->objs; obj->funcs; obj++) {
 988                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 989                                 continue;
 990
 991                         if (action == MODULE_STATE_COMING) {
 992                                 obj->mod = mod;
 993                                 klp_module_notify_coming(patch, obj);
 994                         } else /* MODULE_STATE_GOING */
 995                                 klp_module_notify_going(patch, obj);
 996
 997                         break;
 998                 }
 999         }
1000
1001         mutex_unlock(&klp_mutex);
1002
1003         return 0;
1004 }
1005
1006 static struct notifier_block klp_module_nb = {
1007         .notifier_call = klp_module_notify,
1008         .priority = INT_MIN+1, /* called late but before ftrace notifier */
1009 };
1010
1011 static int klp_init(void)
1012 {
1013         int ret;
1014
1015         ret = klp_check_compiler_support();
1016         if (ret) {
1017                 pr_info("Your compiler is too old; turning off.\n");
1018                 return -EINVAL;
1019         }
1020
1021         ret = register_module_notifier(&klp_module_nb);
1022         if (ret)
1023                 return ret;
1024
1025         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1026         if (!klp_root_kobj) {
1027                 ret = -ENOMEM;
1028                 goto unregister;
1029         }
1030
1031         return 0;
1032
1033 unregister:
1034         unregister_module_notifier(&klp_module_nb);
1035         return ret;
1036 }
1037
1038 module_init(klp_init);