kernel/livepatch/core.c

   1 /*
   2  * core.c - Kernel Live Patching Core
   3  *
   4  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   5  * Copyright (C) 2014 SUSE
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2
  10  * of the License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/module.h>
  24 #include <linux/kernel.h>
  25 #include <linux/mutex.h>
  26 #include <linux/slab.h>
  27 #include <linux/ftrace.h>
  28 #include <linux/list.h>
  29 #include <linux/kallsyms.h>
  30 #include <linux/livepatch.h>
  31 #include <asm/cacheflush.h>
  32
  33 /**
  34  * struct klp_ops - structure for tracking registered ftrace ops structs
  35  *
  36  * A single ftrace_ops is shared between all enabled replacement functions
  37  * (klp_func structs) which have the same old_addr.  This allows the switch
  38  * between function versions to happen instantaneously by updating the klp_ops
  39  * struct's func_stack list.  The winner is the klp_func at the top of the
  40  * func_stack (front of the list).
  41  *
  42  * @node:       node for the global klp_ops list
  43  * @func_stack: list head for the stack of klp_func's (active func is on top)
  44  * @fops:       registered ftrace ops struct
  45  */
  46 struct klp_ops {
  47         struct list_head node;
  48         struct list_head func_stack;
  49         struct ftrace_ops fops;
  50 };
  51
  52 /*
  53  * The klp_mutex protects the global lists and state transitions of any
  54  * structure reachable from them.  References to any structure must be obtained
  55  * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
  56  * ensure it gets consistent data).
  57  */
  58 static DEFINE_MUTEX(klp_mutex);
  59
  60 static LIST_HEAD(klp_patches);
  61 static LIST_HEAD(klp_ops);
  62
  63 static struct kobject *klp_root_kobj;
  64
  65 static struct klp_ops *klp_find_ops(unsigned long old_addr)
  66 {
  67         struct klp_ops *ops;
  68         struct klp_func *func;
  69
  70         list_for_each_entry(ops, &klp_ops, node) {
  71                 func = list_first_entry(&ops->func_stack, struct klp_func,
  72                                         stack_node);
  73                 if (func->old_addr == old_addr)
  74                         return ops;
  75         }
  76
  77         return NULL;
  78 }
  79
  80 static bool klp_is_module(struct klp_object *obj)
  81 {
  82         return obj->name;
  83 }
  84
  85 static bool klp_is_object_loaded(struct klp_object *obj)
  86 {
  87         return !obj->name || obj->mod;
  88 }
  89
  90 /* sets obj->mod if object is not vmlinux and module is found */
  91 static void klp_find_object_module(struct klp_object *obj)
  92 {
  93         struct module *mod;
  94
  95         if (!klp_is_module(obj))
  96                 return;
  97
  98         mutex_lock(&module_mutex);
  99         /*
 100          * We do not want to block removal of patched modules and therefore
 101          * we do not take a reference here. The patches are removed by
 102          * klp_module_going() instead.
 103          */
 104         mod = find_module(obj->name);
 105         /*
 106          * Do not mess work of klp_module_coming() and klp_module_going().
 107          * Note that the patch might still be needed before klp_module_going()
 108          * is called. Module functions can be called even in the GOING state
 109          * until mod->exit() finishes. This is especially important for
 110          * patches that modify semantic of the functions.
 111          */
 112         if (mod && mod->klp_alive)
 113                 obj->mod = mod;
 114
 115         mutex_unlock(&module_mutex);
 116 }
 117
 118 /* klp_mutex must be held by caller */
 119 static bool klp_is_patch_registered(struct klp_patch *patch)
 120 {
 121         struct klp_patch *mypatch;
 122
 123         list_for_each_entry(mypatch, &klp_patches, list)
 124                 if (mypatch == patch)
 125                         return true;
 126
 127         return false;
 128 }
 129
 130 static bool klp_initialized(void)
 131 {
 132         return !!klp_root_kobj;
 133 }
 134
 135 struct klp_find_arg {
 136         const char *objname;
 137         const char *name;
 138         unsigned long addr;
 139         unsigned long count;
 140         unsigned long pos;
 141 };
 142
 143 static int klp_find_callback(void *data, const char *name,
 144                              struct module *mod, unsigned long addr)
 145 {
 146         struct klp_find_arg *args = data;
 147
 148         if ((mod && !args->objname) || (!mod && args->objname))
 149                 return 0;
 150
 151         if (strcmp(args->name, name))
 152                 return 0;
 153
 154         if (args->objname && strcmp(args->objname, mod->name))
 155                 return 0;
 156
 157         args->addr = addr;
 158         args->count++;
 159
 160         /*
 161          * Finish the search when the symbol is found for the desired position
 162          * or the position is not defined for a non-unique symbol.
 163          */
 164         if ((args->pos && (args->count == args->pos)) ||
 165             (!args->pos && (args->count > 1)))
 166                 return 1;
 167
 168         return 0;
 169 }
 170
 171 static int klp_find_object_symbol(const char *objname, const char *name,
 172                                   unsigned long sympos, unsigned long *addr)
 173 {
 174         struct klp_find_arg args = {
 175                 .objname = objname,
 176                 .name = name,
 177                 .addr = 0,
 178                 .count = 0,
 179                 .pos = sympos,
 180         };
 181
 182         mutex_lock(&module_mutex);
 183         kallsyms_on_each_symbol(klp_find_callback, &args);
 184         mutex_unlock(&module_mutex);
 185
 186         /*
 187          * Ensure an address was found. If sympos is 0, ensure symbol is unique;
 188          * otherwise ensure the symbol position count matches sympos.
 189          */
 190         if (args.addr == 0)
 191                 pr_err("symbol '%s' not found in symbol table\n", name);
 192         else if (args.count > 1 && sympos == 0) {
 193                 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
 194                        name, objname);
 195         } else if (sympos != args.count && sympos > 0) {
 196                 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
 197                        sympos, name, objname ? objname : "vmlinux");
 198         } else {
 199                 *addr = args.addr;
 200                 return 0;
 201         }
 202
 203         *addr = 0;
 204         return -EINVAL;
 205 }
 206
 207 /*
 208  * external symbols are located outside the parent object (where the parent
 209  * object is either vmlinux or the kmod being patched).
 210  */
 211 static int klp_find_external_symbol(struct module *pmod, const char *name,
 212                                     unsigned long *addr)
 213 {
 214         const struct kernel_symbol *sym;
 215
 216         /* first, check if it's an exported symbol */
 217         preempt_disable();
 218         sym = find_symbol(name, NULL, NULL, true, true);
 219         if (sym) {
 220                 *addr = sym->value;
 221                 preempt_enable();
 222                 return 0;
 223         }
 224         preempt_enable();
 225
 226         /*
 227          * Check if it's in another .o within the patch module. This also
 228          * checks that the external symbol is unique.
 229          */
 230         return klp_find_object_symbol(pmod->name, name, 0, addr);
 231 }
 232
 233 static int klp_write_object_relocations(struct module *pmod,
 234                                         struct klp_object *obj)
 235 {
 236         int ret = 0;
 237         unsigned long val;
 238         struct klp_reloc *reloc;
 239
 240         if (WARN_ON(!klp_is_object_loaded(obj)))
 241                 return -EINVAL;
 242
 243         if (WARN_ON(!obj->relocs))
 244                 return -EINVAL;
 245
 246         module_disable_ro(pmod);
 247
 248         for (reloc = obj->relocs; reloc->name; reloc++) {
 249                 /* discover the address of the referenced symbol */
 250                 if (reloc->external) {
 251                         if (reloc->sympos > 0) {
 252                                 pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n",
 253                                        reloc->name);
 254                                 ret = -EINVAL;
 255                                 goto out;
 256                         }
 257                         ret = klp_find_external_symbol(pmod, reloc->name, &val);
 258                 } else
 259                         ret = klp_find_object_symbol(obj->name,
 260                                                      reloc->name,
 261                                                      reloc->sympos,
 262                                                      &val);
 263                 if (ret)
 264                         goto out;
 265
 266                 ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
 267                                              val + reloc->addend);
 268                 if (ret) {
 269                         pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
 270                                reloc->name, val, ret);
 271                         goto out;
 272                 }
 273         }
 274
 275 out:
 276         module_enable_ro(pmod);
 277         return ret;
 278 }
 279
 280 static void notrace klp_ftrace_handler(unsigned long ip,
 281                                        unsigned long parent_ip,
 282                                        struct ftrace_ops *fops,
 283                                        struct pt_regs *regs)
 284 {
 285         struct klp_ops *ops;
 286         struct klp_func *func;
 287
 288         ops = container_of(fops, struct klp_ops, fops);
 289
 290         rcu_read_lock();
 291         func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
 292                                       stack_node);
 293         if (WARN_ON_ONCE(!func))
 294                 goto unlock;
 295
 296         klp_arch_set_pc(regs, (unsigned long)func->new_func);
 297 unlock:
 298         rcu_read_unlock();
 299 }
 300
 301 static void klp_disable_func(struct klp_func *func)
 302 {
 303         struct klp_ops *ops;
 304
 305         if (WARN_ON(func->state != KLP_ENABLED))
 306                 return;
 307         if (WARN_ON(!func->old_addr))
 308                 return;
 309
 310         ops = klp_find_ops(func->old_addr);
 311         if (WARN_ON(!ops))
 312                 return;
 313
 314         if (list_is_singular(&ops->func_stack)) {
 315                 WARN_ON(unregister_ftrace_function(&ops->fops));
 316                 WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
 317
 318                 list_del_rcu(&func->stack_node);
 319                 list_del(&ops->node);
 320                 kfree(ops);
 321         } else {
 322                 list_del_rcu(&func->stack_node);
 323         }
 324
 325         func->state = KLP_DISABLED;
 326 }
 327
 328 static int klp_enable_func(struct klp_func *func)
 329 {
 330         struct klp_ops *ops;
 331         int ret;
 332
 333         if (WARN_ON(!func->old_addr))
 334                 return -EINVAL;
 335
 336         if (WARN_ON(func->state != KLP_DISABLED))
 337                 return -EINVAL;
 338
 339         ops = klp_find_ops(func->old_addr);
 340         if (!ops) {
 341                 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
 342                 if (!ops)
 343                         return -ENOMEM;
 344
 345                 ops->fops.func = klp_ftrace_handler;
 346                 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
 347                                   FTRACE_OPS_FL_DYNAMIC |
 348                                   FTRACE_OPS_FL_IPMODIFY;
 349
 350                 list_add(&ops->node, &klp_ops);
 351
 352                 INIT_LIST_HEAD(&ops->func_stack);
 353                 list_add_rcu(&func->stack_node, &ops->func_stack);
 354
 355                 ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
 356                 if (ret) {
 357                         pr_err("failed to set ftrace filter for function '%s' (%d)\n",
 358                                func->old_name, ret);
 359                         goto err;
 360                 }
 361
 362                 ret = register_ftrace_function(&ops->fops);
 363                 if (ret) {
 364                         pr_err("failed to register ftrace handler for function '%s' (%d)\n",
 365                                func->old_name, ret);
 366                         ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
 367                         goto err;
 368                 }
 369
 370
 371         } else {
 372                 list_add_rcu(&func->stack_node, &ops->func_stack);
 373         }
 374
 375         func->state = KLP_ENABLED;
 376
 377         return 0;
 378
 379 err:
 380         list_del_rcu(&func->stack_node);
 381         list_del(&ops->node);
 382         kfree(ops);
 383         return ret;
 384 }
 385
 386 static void klp_disable_object(struct klp_object *obj)
 387 {
 388         struct klp_func *func;
 389
 390         klp_for_each_func(obj, func)
 391                 if (func->state == KLP_ENABLED)
 392                         klp_disable_func(func);
 393
 394         obj->state = KLP_DISABLED;
 395 }
 396
 397 static int klp_enable_object(struct klp_object *obj)
 398 {
 399         struct klp_func *func;
 400         int ret;
 401
 402         if (WARN_ON(obj->state != KLP_DISABLED))
 403                 return -EINVAL;
 404
 405         if (WARN_ON(!klp_is_object_loaded(obj)))
 406                 return -EINVAL;
 407
 408         klp_for_each_func(obj, func) {
 409                 ret = klp_enable_func(func);
 410                 if (ret) {
 411                         klp_disable_object(obj);
 412                         return ret;
 413                 }
 414         }
 415         obj->state = KLP_ENABLED;
 416
 417         return 0;
 418 }
 419
 420 static int __klp_disable_patch(struct klp_patch *patch)
 421 {
 422         struct klp_object *obj;
 423
 424         /* enforce stacking: only the last enabled patch can be disabled */
 425         if (!list_is_last(&patch->list, &klp_patches) &&
 426             list_next_entry(patch, list)->state == KLP_ENABLED)
 427                 return -EBUSY;
 428
 429         pr_notice("disabling patch '%s'\n", patch->mod->name);
 430
 431         klp_for_each_object(patch, obj) {
 432                 if (obj->state == KLP_ENABLED)
 433                         klp_disable_object(obj);
 434         }
 435
 436         patch->state = KLP_DISABLED;
 437
 438         return 0;
 439 }
 440
 441 /**
 442  * klp_disable_patch() - disables a registered patch
 443  * @patch:      The registered, enabled patch to be disabled
 444  *
 445  * Unregisters the patched functions from ftrace.
 446  *
 447  * Return: 0 on success, otherwise error
 448  */
 449 int klp_disable_patch(struct klp_patch *patch)
 450 {
 451         int ret;
 452
 453         mutex_lock(&klp_mutex);
 454
 455         if (!klp_is_patch_registered(patch)) {
 456                 ret = -EINVAL;
 457                 goto err;
 458         }
 459
 460         if (patch->state == KLP_DISABLED) {
 461                 ret = -EINVAL;
 462                 goto err;
 463         }
 464
 465         ret = __klp_disable_patch(patch);
 466
 467 err:
 468         mutex_unlock(&klp_mutex);
 469         return ret;
 470 }
 471 EXPORT_SYMBOL_GPL(klp_disable_patch);
 472
 473 static int __klp_enable_patch(struct klp_patch *patch)
 474 {
 475         struct klp_object *obj;
 476         int ret;
 477
 478         if (WARN_ON(patch->state != KLP_DISABLED))
 479                 return -EINVAL;
 480
 481         /* enforce stacking: only the first disabled patch can be enabled */
 482         if (patch->list.prev != &klp_patches &&
 483             list_prev_entry(patch, list)->state == KLP_DISABLED)
 484                 return -EBUSY;
 485
 486         pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
 487         add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
 488
 489         pr_notice("enabling patch '%s'\n", patch->mod->name);
 490
 491         klp_for_each_object(patch, obj) {
 492                 if (!klp_is_object_loaded(obj))
 493                         continue;
 494
 495                 ret = klp_enable_object(obj);
 496                 if (ret)
 497                         goto unregister;
 498         }
 499
 500         patch->state = KLP_ENABLED;
 501
 502         return 0;
 503
 504 unregister:
 505         WARN_ON(__klp_disable_patch(patch));
 506         return ret;
 507 }
 508
 509 /**
 510  * klp_enable_patch() - enables a registered patch
 511  * @patch:      The registered, disabled patch to be enabled
 512  *
 513  * Performs the needed symbol lookups and code relocations,
 514  * then registers the patched functions with ftrace.
 515  *
 516  * Return: 0 on success, otherwise error
 517  */
 518 int klp_enable_patch(struct klp_patch *patch)
 519 {
 520         int ret;
 521
 522         mutex_lock(&klp_mutex);
 523
 524         if (!klp_is_patch_registered(patch)) {
 525                 ret = -EINVAL;
 526                 goto err;
 527         }
 528
 529         ret = __klp_enable_patch(patch);
 530
 531 err:
 532         mutex_unlock(&klp_mutex);
 533         return ret;
 534 }
 535 EXPORT_SYMBOL_GPL(klp_enable_patch);
 536
 537 /*
 538  * Sysfs Interface
 539  *
 540  * /sys/kernel/livepatch
 541  * /sys/kernel/livepatch/<patch>
 542  * /sys/kernel/livepatch/<patch>/enabled
 543  * /sys/kernel/livepatch/<patch>/<object>
 544  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
 545  */
 546
 547 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 548                              const char *buf, size_t count)
 549 {
 550         struct klp_patch *patch;
 551         int ret;
 552         unsigned long val;
 553
 554         ret = kstrtoul(buf, 10, &val);
 555         if (ret)
 556                 return -EINVAL;
 557
 558         if (val != KLP_DISABLED && val != KLP_ENABLED)
 559                 return -EINVAL;
 560
 561         patch = container_of(kobj, struct klp_patch, kobj);
 562
 563         mutex_lock(&klp_mutex);
 564
 565         if (val == patch->state) {
 566                 /* already in requested state */
 567                 ret = -EINVAL;
 568                 goto err;
 569         }
 570
 571         if (val == KLP_ENABLED) {
 572                 ret = __klp_enable_patch(patch);
 573                 if (ret)
 574                         goto err;
 575         } else {
 576                 ret = __klp_disable_patch(patch);
 577                 if (ret)
 578                         goto err;
 579         }
 580
 581         mutex_unlock(&klp_mutex);
 582
 583         return count;
 584
 585 err:
 586         mutex_unlock(&klp_mutex);
 587         return ret;
 588 }
 589
 590 static ssize_t enabled_show(struct kobject *kobj,
 591                             struct kobj_attribute *attr, char *buf)
 592 {
 593         struct klp_patch *patch;
 594
 595         patch = container_of(kobj, struct klp_patch, kobj);
 596         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
 597 }
 598
 599 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 600 static struct attribute *klp_patch_attrs[] = {
 601         &enabled_kobj_attr.attr,
 602         NULL
 603 };
 604
 605 static void klp_kobj_release_patch(struct kobject *kobj)
 606 {
 607         /*
 608          * Once we have a consistency model we'll need to module_put() the
 609          * patch module here.  See klp_register_patch() for more details.
 610          */
 611 }
 612
 613 static struct kobj_type klp_ktype_patch = {
 614         .release = klp_kobj_release_patch,
 615         .sysfs_ops = &kobj_sysfs_ops,
 616         .default_attrs = klp_patch_attrs,
 617 };
 618
 619 static void klp_kobj_release_object(struct kobject *kobj)
 620 {
 621 }
 622
 623 static struct kobj_type klp_ktype_object = {
 624         .release = klp_kobj_release_object,
 625         .sysfs_ops = &kobj_sysfs_ops,
 626 };
 627
 628 static void klp_kobj_release_func(struct kobject *kobj)
 629 {
 630 }
 631
 632 static struct kobj_type klp_ktype_func = {
 633         .release = klp_kobj_release_func,
 634         .sysfs_ops = &kobj_sysfs_ops,
 635 };
 636
 637 /*
 638  * Free all functions' kobjects in the array up to some limit. When limit is
 639  * NULL, all kobjects are freed.
 640  */
 641 static void klp_free_funcs_limited(struct klp_object *obj,
 642                                    struct klp_func *limit)
 643 {
 644         struct klp_func *func;
 645
 646         for (func = obj->funcs; func->old_name && func != limit; func++)
 647                 kobject_put(&func->kobj);
 648 }
 649
 650 /* Clean up when a patched object is unloaded */
 651 static void klp_free_object_loaded(struct klp_object *obj)
 652 {
 653         struct klp_func *func;
 654
 655         obj->mod = NULL;
 656
 657         klp_for_each_func(obj, func)
 658                 func->old_addr = 0;
 659 }
 660
 661 /*
 662  * Free all objects' kobjects in the array up to some limit. When limit is
 663  * NULL, all kobjects are freed.
 664  */
 665 static void klp_free_objects_limited(struct klp_patch *patch,
 666                                      struct klp_object *limit)
 667 {
 668         struct klp_object *obj;
 669
 670         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 671                 klp_free_funcs_limited(obj, NULL);
 672                 kobject_put(&obj->kobj);
 673         }
 674 }
 675
 676 static void klp_free_patch(struct klp_patch *patch)
 677 {
 678         klp_free_objects_limited(patch, NULL);
 679         if (!list_empty(&patch->list))
 680                 list_del(&patch->list);
 681         kobject_put(&patch->kobj);
 682 }
 683
 684 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 685 {
 686         INIT_LIST_HEAD(&func->stack_node);
 687         func->state = KLP_DISABLED;
 688
 689         /* The format for the sysfs directory is <function,sympos> where sympos
 690          * is the nth occurrence of this symbol in kallsyms for the patched
 691          * object. If the user selects 0 for old_sympos, then 1 will be used
 692          * since a unique symbol will be the first occurrence.
 693          */
 694         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 695                                     &obj->kobj, "%s,%lu", func->old_name,
 696                                     func->old_sympos ? func->old_sympos : 1);
 697 }
 698
 699 /* parts of the initialization that is done only when the object is loaded */
 700 static int klp_init_object_loaded(struct klp_patch *patch,
 701                                   struct klp_object *obj)
 702 {
 703         struct klp_func *func;
 704         int ret;
 705
 706         if (obj->relocs) {
 707                 ret = klp_write_object_relocations(patch->mod, obj);
 708                 if (ret)
 709                         return ret;
 710         }
 711
 712         klp_for_each_func(obj, func) {
 713                 ret = klp_find_object_symbol(obj->name, func->old_name,
 714                                              func->old_sympos,
 715                                              &func->old_addr);
 716                 if (ret)
 717                         return ret;
 718         }
 719
 720         return 0;
 721 }
 722
 723 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 724 {
 725         struct klp_func *func;
 726         int ret;
 727         const char *name;
 728
 729         if (!obj->funcs)
 730                 return -EINVAL;
 731
 732         obj->state = KLP_DISABLED;
 733         obj->mod = NULL;
 734
 735         klp_find_object_module(obj);
 736
 737         name = klp_is_module(obj) ? obj->name : "vmlinux";
 738         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
 739                                    &patch->kobj, "%s", name);
 740         if (ret)
 741                 return ret;
 742
 743         klp_for_each_func(obj, func) {
 744                 ret = klp_init_func(obj, func);
 745                 if (ret)
 746                         goto free;
 747         }
 748
 749         if (klp_is_object_loaded(obj)) {
 750                 ret = klp_init_object_loaded(patch, obj);
 751                 if (ret)
 752                         goto free;
 753         }
 754
 755         return 0;
 756
 757 free:
 758         klp_free_funcs_limited(obj, func);
 759         kobject_put(&obj->kobj);
 760         return ret;
 761 }
 762
 763 static int klp_init_patch(struct klp_patch *patch)
 764 {
 765         struct klp_object *obj;
 766         int ret;
 767
 768         if (!patch->objs)
 769                 return -EINVAL;
 770
 771         mutex_lock(&klp_mutex);
 772
 773         patch->state = KLP_DISABLED;
 774
 775         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 776                                    klp_root_kobj, "%s", patch->mod->name);
 777         if (ret)
 778                 goto unlock;
 779
 780         klp_for_each_object(patch, obj) {
 781                 ret = klp_init_object(patch, obj);
 782                 if (ret)
 783                         goto free;
 784         }
 785
 786         list_add_tail(&patch->list, &klp_patches);
 787
 788         mutex_unlock(&klp_mutex);
 789
 790         return 0;
 791
 792 free:
 793         klp_free_objects_limited(patch, obj);
 794         kobject_put(&patch->kobj);
 795 unlock:
 796         mutex_unlock(&klp_mutex);
 797         return ret;
 798 }
 799
 800 /**
 801  * klp_unregister_patch() - unregisters a patch
 802  * @patch:      Disabled patch to be unregistered
 803  *
 804  * Frees the data structures and removes the sysfs interface.
 805  *
 806  * Return: 0 on success, otherwise error
 807  */
 808 int klp_unregister_patch(struct klp_patch *patch)
 809 {
 810         int ret = 0;
 811
 812         mutex_lock(&klp_mutex);
 813
 814         if (!klp_is_patch_registered(patch)) {
 815                 ret = -EINVAL;
 816                 goto out;
 817         }
 818
 819         if (patch->state == KLP_ENABLED) {
 820                 ret = -EBUSY;
 821                 goto out;
 822         }
 823
 824         klp_free_patch(patch);
 825
 826 out:
 827         mutex_unlock(&klp_mutex);
 828         return ret;
 829 }
 830 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 831
 832 /**
 833  * klp_register_patch() - registers a patch
 834  * @patch:      Patch to be registered
 835  *
 836  * Initializes the data structure associated with the patch and
 837  * creates the sysfs interface.
 838  *
 839  * Return: 0 on success, otherwise error
 840  */
 841 int klp_register_patch(struct klp_patch *patch)
 842 {
 843         int ret;
 844
 845         if (!klp_initialized())
 846                 return -ENODEV;
 847
 848         if (!patch || !patch->mod)
 849                 return -EINVAL;
 850
 851         /*
 852          * A reference is taken on the patch module to prevent it from being
 853          * unloaded.  Right now, we don't allow patch modules to unload since
 854          * there is currently no method to determine if a thread is still
 855          * running in the patched code contained in the patch module once
 856          * the ftrace registration is successful.
 857          */
 858         if (!try_module_get(patch->mod))
 859                 return -ENODEV;
 860
 861         ret = klp_init_patch(patch);
 862         if (ret)
 863                 module_put(patch->mod);
 864
 865         return ret;
 866 }
 867 EXPORT_SYMBOL_GPL(klp_register_patch);
 868
 869 int klp_module_coming(struct module *mod)
 870 {
 871         int ret;
 872         struct klp_patch *patch;
 873         struct klp_object *obj;
 874
 875         if (WARN_ON(mod->state != MODULE_STATE_COMING))
 876                 return -EINVAL;
 877
 878         mutex_lock(&klp_mutex);
 879         /*
 880          * Each module has to know that klp_module_coming()
 881          * has been called. We never know what module will
 882          * get patched by a new patch.
 883          */
 884         mod->klp_alive = true;
 885
 886         list_for_each_entry(patch, &klp_patches, list) {
 887                 klp_for_each_object(patch, obj) {
 888                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 889                                 continue;
 890
 891                         obj->mod = mod;
 892
 893                         ret = klp_init_object_loaded(patch, obj);
 894                         if (ret) {
 895                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
 896                                         patch->mod->name, obj->mod->name, ret);
 897                                 goto err;
 898                         }
 899
 900                         if (patch->state == KLP_DISABLED)
 901                                 break;
 902
 903                         pr_notice("applying patch '%s' to loading module '%s'\n",
 904                                   patch->mod->name, obj->mod->name);
 905
 906                         ret = klp_enable_object(obj);
 907                         if (ret) {
 908                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 909                                         patch->mod->name, obj->mod->name, ret);
 910                                 goto err;
 911                         }
 912
 913                         break;
 914                 }
 915         }
 916
 917         mutex_unlock(&klp_mutex);
 918
 919         return 0;
 920
 921 err:
 922         /*
 923          * If a patch is unsuccessfully applied, return
 924          * error to the module loader.
 925          */
 926         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
 927                 patch->mod->name, obj->mod->name, obj->mod->name);
 928         mod->klp_alive = false;
 929         klp_free_object_loaded(obj);
 930         mutex_unlock(&klp_mutex);
 931
 932         return ret;
 933 }
 934
 935 void klp_module_going(struct module *mod)
 936 {
 937         struct klp_patch *patch;
 938         struct klp_object *obj;
 939
 940         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
 941                     mod->state != MODULE_STATE_COMING))
 942                 return;
 943
 944         mutex_lock(&klp_mutex);
 945         /*
 946          * Each module has to know that klp_module_going()
 947          * has been called. We never know what module will
 948          * get patched by a new patch.
 949          */
 950         mod->klp_alive = false;
 951
 952         list_for_each_entry(patch, &klp_patches, list) {
 953                 klp_for_each_object(patch, obj) {
 954                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 955                                 continue;
 956
 957                         if (patch->state != KLP_DISABLED) {
 958                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
 959                                           patch->mod->name, obj->mod->name);
 960                                 klp_disable_object(obj);
 961                         }
 962
 963                         klp_free_object_loaded(obj);
 964                         break;
 965                 }
 966         }
 967
 968         mutex_unlock(&klp_mutex);
 969 }
 970
 971 static int __init klp_init(void)
 972 {
 973         int ret;
 974
 975         ret = klp_check_compiler_support();
 976         if (ret) {
 977                 pr_info("Your compiler is too old; turning off.\n");
 978                 return -EINVAL;
 979         }
 980
 981         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
 982         if (!klp_root_kobj)
 983                 return -ENOMEM;
 984
 985         return 0;
 986 }
 987
 988 module_init(klp_init);