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 void klp_disable_func(struct klp_func *func)
 339 {
 340         struct klp_ops *ops;
 341
 342         WARN_ON(func->state != KLP_ENABLED);
 343         WARN_ON(!func->old_addr);
 344
 345         ops = klp_find_ops(func->old_addr);
 346         if (WARN_ON(!ops))
 347                 return;
 348
 349         if (list_is_singular(&ops->func_stack)) {
 350                 WARN_ON(unregister_ftrace_function(&ops->fops));
 351                 WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
 352
 353                 list_del_rcu(&func->stack_node);
 354                 list_del(&ops->node);
 355                 kfree(ops);
 356         } else {
 357                 list_del_rcu(&func->stack_node);
 358         }
 359
 360         func->state = KLP_DISABLED;
 361 }
 362
 363 static int klp_enable_func(struct klp_func *func)
 364 {
 365         struct klp_ops *ops;
 366         int ret;
 367
 368         if (WARN_ON(!func->old_addr))
 369                 return -EINVAL;
 370
 371         if (WARN_ON(func->state != KLP_DISABLED))
 372                 return -EINVAL;
 373
 374         ops = klp_find_ops(func->old_addr);
 375         if (!ops) {
 376                 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
 377                 if (!ops)
 378                         return -ENOMEM;
 379
 380                 ops->fops.func = klp_ftrace_handler;
 381                 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
 382                                   FTRACE_OPS_FL_DYNAMIC |
 383                                   FTRACE_OPS_FL_IPMODIFY;
 384
 385                 list_add(&ops->node, &klp_ops);
 386
 387                 INIT_LIST_HEAD(&ops->func_stack);
 388                 list_add_rcu(&func->stack_node, &ops->func_stack);
 389
 390                 ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
 391                 if (ret) {
 392                         pr_err("failed to set ftrace filter for function '%s' (%d)\n",
 393                                func->old_name, ret);
 394                         goto err;
 395                 }
 396
 397                 ret = register_ftrace_function(&ops->fops);
 398                 if (ret) {
 399                         pr_err("failed to register ftrace handler for function '%s' (%d)\n",
 400                                func->old_name, ret);
 401                         ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
 402                         goto err;
 403                 }
 404
 405
 406         } else {
 407                 list_add_rcu(&func->stack_node, &ops->func_stack);
 408         }
 409
 410         func->state = KLP_ENABLED;
 411
 412         return 0;
 413
 414 err:
 415         list_del_rcu(&func->stack_node);
 416         list_del(&ops->node);
 417         kfree(ops);
 418         return ret;
 419 }
 420
 421 static void klp_disable_object(struct klp_object *obj)
 422 {
 423         struct klp_func *func;
 424
 425         for (func = obj->funcs; func->old_name; func++)
 426                 if (func->state == KLP_ENABLED)
 427                         klp_disable_func(func);
 428
 429         obj->state = KLP_DISABLED;
 430 }
 431
 432 static int klp_enable_object(struct klp_object *obj)
 433 {
 434         struct klp_func *func;
 435         int ret;
 436
 437         if (WARN_ON(obj->state != KLP_DISABLED))
 438                 return -EINVAL;
 439
 440         if (WARN_ON(!klp_is_object_loaded(obj)))
 441                 return -EINVAL;
 442
 443         for (func = obj->funcs; func->old_name; func++) {
 444                 ret = klp_enable_func(func);
 445                 if (ret) {
 446                         klp_disable_object(obj);
 447                         return ret;
 448                 }
 449         }
 450         obj->state = KLP_ENABLED;
 451
 452         return 0;
 453 }
 454
 455 static int __klp_disable_patch(struct klp_patch *patch)
 456 {
 457         struct klp_object *obj;
 458
 459         /* enforce stacking: only the last enabled patch can be disabled */
 460         if (!list_is_last(&patch->list, &klp_patches) &&
 461             list_next_entry(patch, list)->state == KLP_ENABLED)
 462                 return -EBUSY;
 463
 464         pr_notice("disabling patch '%s'\n", patch->mod->name);
 465
 466         for (obj = patch->objs; obj->funcs; obj++) {
 467                 if (obj->state == KLP_ENABLED)
 468                         klp_disable_object(obj);
 469         }
 470
 471         patch->state = KLP_DISABLED;
 472
 473         return 0;
 474 }
 475
 476 /**
 477  * klp_disable_patch() - disables a registered patch
 478  * @patch:      The registered, enabled patch to be disabled
 479  *
 480  * Unregisters the patched functions from ftrace.
 481  *
 482  * Return: 0 on success, otherwise error
 483  */
 484 int klp_disable_patch(struct klp_patch *patch)
 485 {
 486         int ret;
 487
 488         mutex_lock(&klp_mutex);
 489
 490         if (!klp_is_patch_registered(patch)) {
 491                 ret = -EINVAL;
 492                 goto err;
 493         }
 494
 495         if (patch->state == KLP_DISABLED) {
 496                 ret = -EINVAL;
 497                 goto err;
 498         }
 499
 500         ret = __klp_disable_patch(patch);
 501
 502 err:
 503         mutex_unlock(&klp_mutex);
 504         return ret;
 505 }
 506 EXPORT_SYMBOL_GPL(klp_disable_patch);
 507
 508 static int __klp_enable_patch(struct klp_patch *patch)
 509 {
 510         struct klp_object *obj;
 511         int ret;
 512
 513         if (WARN_ON(patch->state != KLP_DISABLED))
 514                 return -EINVAL;
 515
 516         /* enforce stacking: only the first disabled patch can be enabled */
 517         if (patch->list.prev != &klp_patches &&
 518             list_prev_entry(patch, list)->state == KLP_DISABLED)
 519                 return -EBUSY;
 520
 521         pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
 522         add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
 523
 524         pr_notice("enabling patch '%s'\n", patch->mod->name);
 525
 526         for (obj = patch->objs; obj->funcs; obj++) {
 527                 if (!klp_is_object_loaded(obj))
 528                         continue;
 529
 530                 ret = klp_enable_object(obj);
 531                 if (ret)
 532                         goto unregister;
 533         }
 534
 535         patch->state = KLP_ENABLED;
 536
 537         return 0;
 538
 539 unregister:
 540         WARN_ON(__klp_disable_patch(patch));
 541         return ret;
 542 }
 543
 544 /**
 545  * klp_enable_patch() - enables a registered patch
 546  * @patch:      The registered, disabled patch to be enabled
 547  *
 548  * Performs the needed symbol lookups and code relocations,
 549  * then registers the patched functions with ftrace.
 550  *
 551  * Return: 0 on success, otherwise error
 552  */
 553 int klp_enable_patch(struct klp_patch *patch)
 554 {
 555         int ret;
 556
 557         mutex_lock(&klp_mutex);
 558
 559         if (!klp_is_patch_registered(patch)) {
 560                 ret = -EINVAL;
 561                 goto err;
 562         }
 563
 564         ret = __klp_enable_patch(patch);
 565
 566 err:
 567         mutex_unlock(&klp_mutex);
 568         return ret;
 569 }
 570 EXPORT_SYMBOL_GPL(klp_enable_patch);
 571
 572 /*
 573  * Sysfs Interface
 574  *
 575  * /sys/kernel/livepatch
 576  * /sys/kernel/livepatch/<patch>
 577  * /sys/kernel/livepatch/<patch>/enabled
 578  * /sys/kernel/livepatch/<patch>/<object>
 579  * /sys/kernel/livepatch/<patch>/<object>/<func>
 580  */
 581
 582 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 583                              const char *buf, size_t count)
 584 {
 585         struct klp_patch *patch;
 586         int ret;
 587         unsigned long val;
 588
 589         ret = kstrtoul(buf, 10, &val);
 590         if (ret)
 591                 return -EINVAL;
 592
 593         if (val != KLP_DISABLED && val != KLP_ENABLED)
 594                 return -EINVAL;
 595
 596         patch = container_of(kobj, struct klp_patch, kobj);
 597
 598         mutex_lock(&klp_mutex);
 599
 600         if (val == patch->state) {
 601                 /* already in requested state */
 602                 ret = -EINVAL;
 603                 goto err;
 604         }
 605
 606         if (val == KLP_ENABLED) {
 607                 ret = __klp_enable_patch(patch);
 608                 if (ret)
 609                         goto err;
 610         } else {
 611                 ret = __klp_disable_patch(patch);
 612                 if (ret)
 613                         goto err;
 614         }
 615
 616         mutex_unlock(&klp_mutex);
 617
 618         return count;
 619
 620 err:
 621         mutex_unlock(&klp_mutex);
 622         return ret;
 623 }
 624
 625 static ssize_t enabled_show(struct kobject *kobj,
 626                             struct kobj_attribute *attr, char *buf)
 627 {
 628         struct klp_patch *patch;
 629
 630         patch = container_of(kobj, struct klp_patch, kobj);
 631         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
 632 }
 633
 634 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 635 static struct attribute *klp_patch_attrs[] = {
 636         &enabled_kobj_attr.attr,
 637         NULL
 638 };
 639
 640 static void klp_kobj_release_patch(struct kobject *kobj)
 641 {
 642         /*
 643          * Once we have a consistency model we'll need to module_put() the
 644          * patch module here.  See klp_register_patch() for more details.
 645          */
 646 }
 647
 648 static struct kobj_type klp_ktype_patch = {
 649         .release = klp_kobj_release_patch,
 650         .sysfs_ops = &kobj_sysfs_ops,
 651         .default_attrs = klp_patch_attrs,
 652 };
 653
 654 static void klp_kobj_release_func(struct kobject *kobj)
 655 {
 656 }
 657
 658 static struct kobj_type klp_ktype_func = {
 659         .release = klp_kobj_release_func,
 660         .sysfs_ops = &kobj_sysfs_ops,
 661 };
 662
 663 /*
 664  * Free all functions' kobjects in the array up to some limit. When limit is
 665  * NULL, all kobjects are freed.
 666  */
 667 static void klp_free_funcs_limited(struct klp_object *obj,
 668                                    struct klp_func *limit)
 669 {
 670         struct klp_func *func;
 671
 672         for (func = obj->funcs; func->old_name && func != limit; func++)
 673                 kobject_put(&func->kobj);
 674 }
 675
 676 /* Clean up when a patched object is unloaded */
 677 static void klp_free_object_loaded(struct klp_object *obj)
 678 {
 679         struct klp_func *func;
 680
 681         obj->mod = NULL;
 682
 683         for (func = obj->funcs; func->old_name; func++)
 684                 func->old_addr = 0;
 685 }
 686
 687 /*
 688  * Free all objects' kobjects in the array up to some limit. When limit is
 689  * NULL, all kobjects are freed.
 690  */
 691 static void klp_free_objects_limited(struct klp_patch *patch,
 692                                      struct klp_object *limit)
 693 {
 694         struct klp_object *obj;
 695
 696         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 697                 klp_free_funcs_limited(obj, NULL);
 698                 kobject_put(obj->kobj);
 699         }
 700 }
 701
 702 static void klp_free_patch(struct klp_patch *patch)
 703 {
 704         klp_free_objects_limited(patch, NULL);
 705         if (!list_empty(&patch->list))
 706                 list_del(&patch->list);
 707         kobject_put(&patch->kobj);
 708 }
 709
 710 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 711 {
 712         INIT_LIST_HEAD(&func->stack_node);
 713         func->state = KLP_DISABLED;
 714
 715         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 716                                     obj->kobj, "%s", func->old_name);
 717 }
 718
 719 /* parts of the initialization that is done only when the object is loaded */
 720 static int klp_init_object_loaded(struct klp_patch *patch,
 721                                   struct klp_object *obj)
 722 {
 723         struct klp_func *func;
 724         int ret;
 725
 726         if (obj->relocs) {
 727                 ret = klp_write_object_relocations(patch->mod, obj);
 728                 if (ret)
 729                         return ret;
 730         }
 731
 732         for (func = obj->funcs; func->old_name; func++) {
 733                 ret = klp_find_verify_func_addr(obj, func);
 734                 if (ret)
 735                         return ret;
 736         }
 737
 738         return 0;
 739 }
 740
 741 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 742 {
 743         struct klp_func *func;
 744         int ret;
 745         const char *name;
 746
 747         if (!obj->funcs)
 748                 return -EINVAL;
 749
 750         obj->state = KLP_DISABLED;
 751         obj->mod = NULL;
 752
 753         klp_find_object_module(obj);
 754
 755         name = klp_is_module(obj) ? obj->name : "vmlinux";
 756         obj->kobj = kobject_create_and_add(name, &patch->kobj);
 757         if (!obj->kobj)
 758                 return -ENOMEM;
 759
 760         for (func = obj->funcs; func->old_name; func++) {
 761                 ret = klp_init_func(obj, func);
 762                 if (ret)
 763                         goto free;
 764         }
 765
 766         if (klp_is_object_loaded(obj)) {
 767                 ret = klp_init_object_loaded(patch, obj);
 768                 if (ret)
 769                         goto free;
 770         }
 771
 772         return 0;
 773
 774 free:
 775         klp_free_funcs_limited(obj, func);
 776         kobject_put(obj->kobj);
 777         return ret;
 778 }
 779
 780 static int klp_init_patch(struct klp_patch *patch)
 781 {
 782         struct klp_object *obj;
 783         int ret;
 784
 785         if (!patch->objs)
 786                 return -EINVAL;
 787
 788         mutex_lock(&klp_mutex);
 789
 790         patch->state = KLP_DISABLED;
 791
 792         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 793                                    klp_root_kobj, "%s", patch->mod->name);
 794         if (ret)
 795                 goto unlock;
 796
 797         for (obj = patch->objs; obj->funcs; obj++) {
 798                 ret = klp_init_object(patch, obj);
 799                 if (ret)
 800                         goto free;
 801         }
 802
 803         list_add_tail(&patch->list, &klp_patches);
 804
 805         mutex_unlock(&klp_mutex);
 806
 807         return 0;
 808
 809 free:
 810         klp_free_objects_limited(patch, obj);
 811         kobject_put(&patch->kobj);
 812 unlock:
 813         mutex_unlock(&klp_mutex);
 814         return ret;
 815 }
 816
 817 /**
 818  * klp_unregister_patch() - unregisters a patch
 819  * @patch:      Disabled patch to be unregistered
 820  *
 821  * Frees the data structures and removes the sysfs interface.
 822  *
 823  * Return: 0 on success, otherwise error
 824  */
 825 int klp_unregister_patch(struct klp_patch *patch)
 826 {
 827         int ret = 0;
 828
 829         mutex_lock(&klp_mutex);
 830
 831         if (!klp_is_patch_registered(patch)) {
 832                 ret = -EINVAL;
 833                 goto out;
 834         }
 835
 836         if (patch->state == KLP_ENABLED) {
 837                 ret = -EBUSY;
 838                 goto out;
 839         }
 840
 841         klp_free_patch(patch);
 842
 843 out:
 844         mutex_unlock(&klp_mutex);
 845         return ret;
 846 }
 847 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 848
 849 /**
 850  * klp_register_patch() - registers a patch
 851  * @patch:      Patch to be registered
 852  *
 853  * Initializes the data structure associated with the patch and
 854  * creates the sysfs interface.
 855  *
 856  * Return: 0 on success, otherwise error
 857  */
 858 int klp_register_patch(struct klp_patch *patch)
 859 {
 860         int ret;
 861
 862         if (!klp_initialized())
 863                 return -ENODEV;
 864
 865         if (!patch || !patch->mod)
 866                 return -EINVAL;
 867
 868         /*
 869          * A reference is taken on the patch module to prevent it from being
 870          * unloaded.  Right now, we don't allow patch modules to unload since
 871          * there is currently no method to determine if a thread is still
 872          * running in the patched code contained in the patch module once
 873          * the ftrace registration is successful.
 874          */
 875         if (!try_module_get(patch->mod))
 876                 return -ENODEV;
 877
 878         ret = klp_init_patch(patch);
 879         if (ret)
 880                 module_put(patch->mod);
 881
 882         return ret;
 883 }
 884 EXPORT_SYMBOL_GPL(klp_register_patch);
 885
 886 static void klp_module_notify_coming(struct klp_patch *patch,
 887                                      struct klp_object *obj)
 888 {
 889         struct module *pmod = patch->mod;
 890         struct module *mod = obj->mod;
 891         int ret;
 892
 893         ret = klp_init_object_loaded(patch, obj);
 894         if (ret)
 895                 goto err;
 896
 897         if (patch->state == KLP_DISABLED)
 898                 return;
 899
 900         pr_notice("applying patch '%s' to loading module '%s'\n",
 901                   pmod->name, mod->name);
 902
 903         ret = klp_enable_object(obj);
 904         if (!ret)
 905                 return;
 906
 907 err:
 908         pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 909                 pmod->name, mod->name, ret);
 910 }
 911
 912 static void klp_module_notify_going(struct klp_patch *patch,
 913                                     struct klp_object *obj)
 914 {
 915         struct module *pmod = patch->mod;
 916         struct module *mod = obj->mod;
 917
 918         if (patch->state == KLP_DISABLED)
 919                 goto disabled;
 920
 921         pr_notice("reverting patch '%s' on unloading module '%s'\n",
 922                   pmod->name, mod->name);
 923
 924         klp_disable_object(obj);
 925
 926 disabled:
 927         klp_free_object_loaded(obj);
 928 }
 929
 930 static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 931                              void *data)
 932 {
 933         struct module *mod = data;
 934         struct klp_patch *patch;
 935         struct klp_object *obj;
 936
 937         if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
 938                 return 0;
 939
 940         mutex_lock(&klp_mutex);
 941
 942         /*
 943          * Each module has to know that the notifier has been called.
 944          * We never know what module will get patched by a new patch.
 945          */
 946         if (action == MODULE_STATE_COMING)
 947                 mod->klp_alive = true;
 948         else /* MODULE_STATE_GOING */
 949                 mod->klp_alive = false;
 950
 951         list_for_each_entry(patch, &klp_patches, list) {
 952                 for (obj = patch->objs; obj->funcs; obj++) {
 953                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 954                                 continue;
 955
 956                         if (action == MODULE_STATE_COMING) {
 957                                 obj->mod = mod;
 958                                 klp_module_notify_coming(patch, obj);
 959                         } else /* MODULE_STATE_GOING */
 960                                 klp_module_notify_going(patch, obj);
 961
 962                         break;
 963                 }
 964         }
 965
 966         mutex_unlock(&klp_mutex);
 967
 968         return 0;
 969 }
 970
 971 static struct notifier_block klp_module_nb = {
 972         .notifier_call = klp_module_notify,
 973         .priority = INT_MIN+1, /* called late but before ftrace notifier */
 974 };
 975
 976 static int klp_init(void)
 977 {
 978         int ret;
 979
 980         ret = klp_check_compiler_support();
 981         if (ret) {
 982                 pr_info("Your compiler is too old; turning off.\n");
 983                 return -EINVAL;
 984         }
 985
 986         ret = register_module_notifier(&klp_module_nb);
 987         if (ret)
 988                 return ret;
 989
 990         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
 991         if (!klp_root_kobj) {
 992                 ret = -ENOMEM;
 993                 goto unregister;
 994         }
 995
 996         return 0;
 997
 998 unregister:
 999         unregister_module_notifier(&klp_module_nb);
1000         return ret;
1001 }
1002
1003 module_init(klp_init);