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/list.h>
  28 #include <linux/kallsyms.h>
  29 #include <linux/livepatch.h>
  30 #include <linux/elf.h>
  31 #include <linux/moduleloader.h>
  32 #include <linux/completion.h>
  33 #include <asm/cacheflush.h>
  34 #include "core.h"
  35 #include "patch.h"
  36 #include "transition.h"
  37
  38 /*
  39  * klp_mutex is a coarse lock which serializes access to klp data.  All
  40  * accesses to klp-related variables and structures must have mutex protection,
  41  * except within the following functions which carefully avoid the need for it:
  42  *
  43  * - klp_ftrace_handler()
  44  * - klp_update_patch_state()
  45  */
  46 DEFINE_MUTEX(klp_mutex);
  47
  48 static LIST_HEAD(klp_patches);
  49
  50 static struct kobject *klp_root_kobj;
  51
  52 static bool klp_is_module(struct klp_object *obj)
  53 {
  54         return obj->name;
  55 }
  56
  57 /* sets obj->mod if object is not vmlinux and module is found */
  58 static void klp_find_object_module(struct klp_object *obj)
  59 {
  60         struct module *mod;
  61
  62         if (!klp_is_module(obj))
  63                 return;
  64
  65         mutex_lock(&module_mutex);
  66         /*
  67          * We do not want to block removal of patched modules and therefore
  68          * we do not take a reference here. The patches are removed by
  69          * klp_module_going() instead.
  70          */
  71         mod = find_module(obj->name);
  72         /*
  73          * Do not mess work of klp_module_coming() and klp_module_going().
  74          * Note that the patch might still be needed before klp_module_going()
  75          * is called. Module functions can be called even in the GOING state
  76          * until mod->exit() finishes. This is especially important for
  77          * patches that modify semantic of the functions.
  78          */
  79         if (mod && mod->klp_alive)
  80                 obj->mod = mod;
  81
  82         mutex_unlock(&module_mutex);
  83 }
  84
  85 static bool klp_is_patch_registered(struct klp_patch *patch)
  86 {
  87         struct klp_patch *mypatch;
  88
  89         list_for_each_entry(mypatch, &klp_patches, list)
  90                 if (mypatch == patch)
  91                         return true;
  92
  93         return false;
  94 }
  95
  96 static bool klp_initialized(void)
  97 {
  98         return !!klp_root_kobj;
  99 }
 100
 101 struct klp_find_arg {
 102         const char *objname;
 103         const char *name;
 104         unsigned long addr;
 105         unsigned long count;
 106         unsigned long pos;
 107 };
 108
 109 static int klp_find_callback(void *data, const char *name,
 110                              struct module *mod, unsigned long addr)
 111 {
 112         struct klp_find_arg *args = data;
 113
 114         if ((mod && !args->objname) || (!mod && args->objname))
 115                 return 0;
 116
 117         if (strcmp(args->name, name))
 118                 return 0;
 119
 120         if (args->objname && strcmp(args->objname, mod->name))
 121                 return 0;
 122
 123         args->addr = addr;
 124         args->count++;
 125
 126         /*
 127          * Finish the search when the symbol is found for the desired position
 128          * or the position is not defined for a non-unique symbol.
 129          */
 130         if ((args->pos && (args->count == args->pos)) ||
 131             (!args->pos && (args->count > 1)))
 132                 return 1;
 133
 134         return 0;
 135 }
 136
 137 static int klp_find_object_symbol(const char *objname, const char *name,
 138                                   unsigned long sympos, unsigned long *addr)
 139 {
 140         struct klp_find_arg args = {
 141                 .objname = objname,
 142                 .name = name,
 143                 .addr = 0,
 144                 .count = 0,
 145                 .pos = sympos,
 146         };
 147
 148         mutex_lock(&module_mutex);
 149         if (objname)
 150                 module_kallsyms_on_each_symbol(klp_find_callback, &args);
 151         else
 152                 kallsyms_on_each_symbol(klp_find_callback, &args);
 153         mutex_unlock(&module_mutex);
 154
 155         /*
 156          * Ensure an address was found. If sympos is 0, ensure symbol is unique;
 157          * otherwise ensure the symbol position count matches sympos.
 158          */
 159         if (args.addr == 0)
 160                 pr_err("symbol '%s' not found in symbol table\n", name);
 161         else if (args.count > 1 && sympos == 0) {
 162                 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
 163                        name, objname);
 164         } else if (sympos != args.count && sympos > 0) {
 165                 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
 166                        sympos, name, objname ? objname : "vmlinux");
 167         } else {
 168                 *addr = args.addr;
 169                 return 0;
 170         }
 171
 172         *addr = 0;
 173         return -EINVAL;
 174 }
 175
 176 static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 177 {
 178         int i, cnt, vmlinux, ret;
 179         char objname[MODULE_NAME_LEN];
 180         char symname[KSYM_NAME_LEN];
 181         char *strtab = pmod->core_kallsyms.strtab;
 182         Elf_Rela *relas;
 183         Elf_Sym *sym;
 184         unsigned long sympos, addr;
 185
 186         /*
 187          * Since the field widths for objname and symname in the sscanf()
 188          * call are hard-coded and correspond to MODULE_NAME_LEN and
 189          * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
 190          * and KSYM_NAME_LEN have the values we expect them to have.
 191          *
 192          * Because the value of MODULE_NAME_LEN can differ among architectures,
 193          * we use the smallest/strictest upper bound possible (56, based on
 194          * the current definition of MODULE_NAME_LEN) to prevent overflows.
 195          */
 196         BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
 197
 198         relas = (Elf_Rela *) relasec->sh_addr;
 199         /* For each rela in this klp relocation section */
 200         for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
 201                 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
 202                 if (sym->st_shndx != SHN_LIVEPATCH) {
 203                         pr_err("symbol %s is not marked as a livepatch symbol\n",
 204                                strtab + sym->st_name);
 205                         return -EINVAL;
 206                 }
 207
 208                 /* Format: .klp.sym.objname.symname,sympos */
 209                 cnt = sscanf(strtab + sym->st_name,
 210                              ".klp.sym.%55[^.].%127[^,],%lu",
 211                              objname, symname, &sympos);
 212                 if (cnt != 3) {
 213                         pr_err("symbol %s has an incorrectly formatted name\n",
 214                                strtab + sym->st_name);
 215                         return -EINVAL;
 216                 }
 217
 218                 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
 219                 vmlinux = !strcmp(objname, "vmlinux");
 220                 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
 221                                              symname, sympos, &addr);
 222                 if (ret)
 223                         return ret;
 224
 225                 sym->st_value = addr;
 226         }
 227
 228         return 0;
 229 }
 230
 231 static int klp_write_object_relocations(struct module *pmod,
 232                                         struct klp_object *obj)
 233 {
 234         int i, cnt, ret = 0;
 235         const char *objname, *secname;
 236         char sec_objname[MODULE_NAME_LEN];
 237         Elf_Shdr *sec;
 238
 239         if (WARN_ON(!klp_is_object_loaded(obj)))
 240                 return -EINVAL;
 241
 242         objname = klp_is_module(obj) ? obj->name : "vmlinux";
 243
 244         /* For each klp relocation section */
 245         for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
 246                 sec = pmod->klp_info->sechdrs + i;
 247                 secname = pmod->klp_info->secstrings + sec->sh_name;
 248                 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
 249                         continue;
 250
 251                 /*
 252                  * Format: .klp.rela.sec_objname.section_name
 253                  * See comment in klp_resolve_symbols() for an explanation
 254                  * of the selected field width value.
 255                  */
 256                 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
 257                 if (cnt != 1) {
 258                         pr_err("section %s has an incorrectly formatted name\n",
 259                                secname);
 260                         ret = -EINVAL;
 261                         break;
 262                 }
 263
 264                 if (strcmp(objname, sec_objname))
 265                         continue;
 266
 267                 ret = klp_resolve_symbols(sec, pmod);
 268                 if (ret)
 269                         break;
 270
 271                 ret = apply_relocate_add(pmod->klp_info->sechdrs,
 272                                          pmod->core_kallsyms.strtab,
 273                                          pmod->klp_info->symndx, i, pmod);
 274                 if (ret)
 275                         break;
 276         }
 277
 278         return ret;
 279 }
 280
 281 static int __klp_disable_patch(struct klp_patch *patch)
 282 {
 283         struct klp_object *obj;
 284
 285         if (WARN_ON(!patch->enabled))
 286                 return -EINVAL;
 287
 288         if (klp_transition_patch)
 289                 return -EBUSY;
 290
 291         /* enforce stacking: only the last enabled patch can be disabled */
 292         if (!list_is_last(&patch->list, &klp_patches) &&
 293             list_next_entry(patch, list)->enabled)
 294                 return -EBUSY;
 295
 296         klp_init_transition(patch, KLP_UNPATCHED);
 297
 298         klp_for_each_object(patch, obj)
 299                 if (obj->patched)
 300                         klp_pre_unpatch_callback(obj);
 301
 302         /*
 303          * Enforce the order of the func->transition writes in
 304          * klp_init_transition() and the TIF_PATCH_PENDING writes in
 305          * klp_start_transition().  In the rare case where klp_ftrace_handler()
 306          * is called shortly after klp_update_patch_state() switches the task,
 307          * this ensures the handler sees that func->transition is set.
 308          */
 309         smp_wmb();
 310
 311         klp_start_transition();
 312         klp_try_complete_transition();
 313         patch->enabled = false;
 314
 315         return 0;
 316 }
 317
 318 /**
 319  * klp_disable_patch() - disables a registered patch
 320  * @patch:      The registered, enabled patch to be disabled
 321  *
 322  * Unregisters the patched functions from ftrace.
 323  *
 324  * Return: 0 on success, otherwise error
 325  */
 326 int klp_disable_patch(struct klp_patch *patch)
 327 {
 328         int ret;
 329
 330         mutex_lock(&klp_mutex);
 331
 332         if (!klp_is_patch_registered(patch)) {
 333                 ret = -EINVAL;
 334                 goto err;
 335         }
 336
 337         if (!patch->enabled) {
 338                 ret = -EINVAL;
 339                 goto err;
 340         }
 341
 342         ret = __klp_disable_patch(patch);
 343
 344 err:
 345         mutex_unlock(&klp_mutex);
 346         return ret;
 347 }
 348 EXPORT_SYMBOL_GPL(klp_disable_patch);
 349
 350 static int __klp_enable_patch(struct klp_patch *patch)
 351 {
 352         struct klp_object *obj;
 353         int ret;
 354
 355         if (klp_transition_patch)
 356                 return -EBUSY;
 357
 358         if (WARN_ON(patch->enabled))
 359                 return -EINVAL;
 360
 361         /* enforce stacking: only the first disabled patch can be enabled */
 362         if (patch->list.prev != &klp_patches &&
 363             !list_prev_entry(patch, list)->enabled)
 364                 return -EBUSY;
 365
 366         /*
 367          * A reference is taken on the patch module to prevent it from being
 368          * unloaded.
 369          */
 370         if (!try_module_get(patch->mod))
 371                 return -ENODEV;
 372
 373         pr_notice("enabling patch '%s'\n", patch->mod->name);
 374
 375         klp_init_transition(patch, KLP_PATCHED);
 376
 377         /*
 378          * Enforce the order of the func->transition writes in
 379          * klp_init_transition() and the ops->func_stack writes in
 380          * klp_patch_object(), so that klp_ftrace_handler() will see the
 381          * func->transition updates before the handler is registered and the
 382          * new funcs become visible to the handler.
 383          */
 384         smp_wmb();
 385
 386         klp_for_each_object(patch, obj) {
 387                 if (!klp_is_object_loaded(obj))
 388                         continue;
 389
 390                 ret = klp_pre_patch_callback(obj);
 391                 if (ret) {
 392                         pr_warn("pre-patch callback failed for object '%s'\n",
 393                                 klp_is_module(obj) ? obj->name : "vmlinux");
 394                         goto err;
 395                 }
 396
 397                 ret = klp_patch_object(obj);
 398                 if (ret) {
 399                         pr_warn("failed to patch object '%s'\n",
 400                                 klp_is_module(obj) ? obj->name : "vmlinux");
 401                         goto err;
 402                 }
 403         }
 404
 405         klp_start_transition();
 406         klp_try_complete_transition();
 407         patch->enabled = true;
 408
 409         return 0;
 410 err:
 411         pr_warn("failed to enable patch '%s'\n", patch->mod->name);
 412
 413         klp_cancel_transition();
 414         return ret;
 415 }
 416
 417 /**
 418  * klp_enable_patch() - enables a registered patch
 419  * @patch:      The registered, disabled patch to be enabled
 420  *
 421  * Performs the needed symbol lookups and code relocations,
 422  * then registers the patched functions with ftrace.
 423  *
 424  * Return: 0 on success, otherwise error
 425  */
 426 int klp_enable_patch(struct klp_patch *patch)
 427 {
 428         int ret;
 429
 430         mutex_lock(&klp_mutex);
 431
 432         if (!klp_is_patch_registered(patch)) {
 433                 ret = -EINVAL;
 434                 goto err;
 435         }
 436
 437         ret = __klp_enable_patch(patch);
 438
 439 err:
 440         mutex_unlock(&klp_mutex);
 441         return ret;
 442 }
 443 EXPORT_SYMBOL_GPL(klp_enable_patch);
 444
 445 /*
 446  * Sysfs Interface
 447  *
 448  * /sys/kernel/livepatch
 449  * /sys/kernel/livepatch/<patch>
 450  * /sys/kernel/livepatch/<patch>/enabled
 451  * /sys/kernel/livepatch/<patch>/transition
 452  * /sys/kernel/livepatch/<patch>/signal
 453  * /sys/kernel/livepatch/<patch>/force
 454  * /sys/kernel/livepatch/<patch>/<object>
 455  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
 456  */
 457
 458 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 459                              const char *buf, size_t count)
 460 {
 461         struct klp_patch *patch;
 462         int ret;
 463         bool enabled;
 464
 465         ret = kstrtobool(buf, &enabled);
 466         if (ret)
 467                 return ret;
 468
 469         patch = container_of(kobj, struct klp_patch, kobj);
 470
 471         mutex_lock(&klp_mutex);
 472
 473         if (!klp_is_patch_registered(patch)) {
 474                 /*
 475                  * Module with the patch could either disappear meanwhile or is
 476                  * not properly initialized yet.
 477                  */
 478                 ret = -EINVAL;
 479                 goto err;
 480         }
 481
 482         if (patch->enabled == enabled) {
 483                 /* already in requested state */
 484                 ret = -EINVAL;
 485                 goto err;
 486         }
 487
 488         if (patch == klp_transition_patch) {
 489                 klp_reverse_transition();
 490         } else if (enabled) {
 491                 ret = __klp_enable_patch(patch);
 492                 if (ret)
 493                         goto err;
 494         } else {
 495                 ret = __klp_disable_patch(patch);
 496                 if (ret)
 497                         goto err;
 498         }
 499
 500         mutex_unlock(&klp_mutex);
 501
 502         return count;
 503
 504 err:
 505         mutex_unlock(&klp_mutex);
 506         return ret;
 507 }
 508
 509 static ssize_t enabled_show(struct kobject *kobj,
 510                             struct kobj_attribute *attr, char *buf)
 511 {
 512         struct klp_patch *patch;
 513
 514         patch = container_of(kobj, struct klp_patch, kobj);
 515         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
 516 }
 517
 518 static ssize_t transition_show(struct kobject *kobj,
 519                                struct kobj_attribute *attr, char *buf)
 520 {
 521         struct klp_patch *patch;
 522
 523         patch = container_of(kobj, struct klp_patch, kobj);
 524         return snprintf(buf, PAGE_SIZE-1, "%d\n",
 525                         patch == klp_transition_patch);
 526 }
 527
 528 static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
 529                             const char *buf, size_t count)
 530 {
 531         struct klp_patch *patch;
 532         int ret;
 533         bool val;
 534
 535         ret = kstrtobool(buf, &val);
 536         if (ret)
 537                 return ret;
 538
 539         if (!val)
 540                 return count;
 541
 542         mutex_lock(&klp_mutex);
 543
 544         patch = container_of(kobj, struct klp_patch, kobj);
 545         if (patch != klp_transition_patch) {
 546                 mutex_unlock(&klp_mutex);
 547                 return -EINVAL;
 548         }
 549
 550         klp_send_signals();
 551
 552         mutex_unlock(&klp_mutex);
 553
 554         return count;
 555 }
 556
 557 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
 558                            const char *buf, size_t count)
 559 {
 560         struct klp_patch *patch;
 561         int ret;
 562         bool val;
 563
 564         ret = kstrtobool(buf, &val);
 565         if (ret)
 566                 return ret;
 567
 568         if (!val)
 569                 return count;
 570
 571         mutex_lock(&klp_mutex);
 572
 573         patch = container_of(kobj, struct klp_patch, kobj);
 574         if (patch != klp_transition_patch) {
 575                 mutex_unlock(&klp_mutex);
 576                 return -EINVAL;
 577         }
 578
 579         klp_force_transition();
 580
 581         mutex_unlock(&klp_mutex);
 582
 583         return count;
 584 }
 585
 586 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 587 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
 588 static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
 589 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
 590 static struct attribute *klp_patch_attrs[] = {
 591         &enabled_kobj_attr.attr,
 592         &transition_kobj_attr.attr,
 593         &signal_kobj_attr.attr,
 594         &force_kobj_attr.attr,
 595         NULL
 596 };
 597
 598 static void klp_kobj_release_patch(struct kobject *kobj)
 599 {
 600         struct klp_patch *patch;
 601
 602         patch = container_of(kobj, struct klp_patch, kobj);
 603         complete(&patch->finish);
 604 }
 605
 606 static struct kobj_type klp_ktype_patch = {
 607         .release = klp_kobj_release_patch,
 608         .sysfs_ops = &kobj_sysfs_ops,
 609         .default_attrs = klp_patch_attrs,
 610 };
 611
 612 static void klp_kobj_release_object(struct kobject *kobj)
 613 {
 614 }
 615
 616 static struct kobj_type klp_ktype_object = {
 617         .release = klp_kobj_release_object,
 618         .sysfs_ops = &kobj_sysfs_ops,
 619 };
 620
 621 static void klp_kobj_release_func(struct kobject *kobj)
 622 {
 623 }
 624
 625 static struct kobj_type klp_ktype_func = {
 626         .release = klp_kobj_release_func,
 627         .sysfs_ops = &kobj_sysfs_ops,
 628 };
 629
 630 /*
 631  * Free all functions' kobjects in the array up to some limit. When limit is
 632  * NULL, all kobjects are freed.
 633  */
 634 static void klp_free_funcs_limited(struct klp_object *obj,
 635                                    struct klp_func *limit)
 636 {
 637         struct klp_func *func;
 638
 639         for (func = obj->funcs; func->old_name && func != limit; func++)
 640                 kobject_put(&func->kobj);
 641 }
 642
 643 /* Clean up when a patched object is unloaded */
 644 static void klp_free_object_loaded(struct klp_object *obj)
 645 {
 646         struct klp_func *func;
 647
 648         obj->mod = NULL;
 649
 650         klp_for_each_func(obj, func)
 651                 func->old_addr = 0;
 652 }
 653
 654 /*
 655  * Free all objects' kobjects in the array up to some limit. When limit is
 656  * NULL, all kobjects are freed.
 657  */
 658 static void klp_free_objects_limited(struct klp_patch *patch,
 659                                      struct klp_object *limit)
 660 {
 661         struct klp_object *obj;
 662
 663         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 664                 klp_free_funcs_limited(obj, NULL);
 665                 kobject_put(&obj->kobj);
 666         }
 667 }
 668
 669 static void klp_free_patch(struct klp_patch *patch)
 670 {
 671         klp_free_objects_limited(patch, NULL);
 672         if (!list_empty(&patch->list))
 673                 list_del(&patch->list);
 674 }
 675
 676 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 677 {
 678         if (!func->old_name || !func->new_func)
 679                 return -EINVAL;
 680
 681         INIT_LIST_HEAD(&func->stack_node);
 682         func->patched = false;
 683         func->transition = false;
 684
 685         /* The format for the sysfs directory is <function,sympos> where sympos
 686          * is the nth occurrence of this symbol in kallsyms for the patched
 687          * object. If the user selects 0 for old_sympos, then 1 will be used
 688          * since a unique symbol will be the first occurrence.
 689          */
 690         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 691                                     &obj->kobj, "%s,%lu", func->old_name,
 692                                     func->old_sympos ? func->old_sympos : 1);
 693 }
 694
 695 /* Arches may override this to finish any remaining arch-specific tasks */
 696 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
 697                                         struct klp_object *obj)
 698 {
 699 }
 700
 701 /* parts of the initialization that is done only when the object is loaded */
 702 static int klp_init_object_loaded(struct klp_patch *patch,
 703                                   struct klp_object *obj)
 704 {
 705         struct klp_func *func;
 706         int ret;
 707
 708         module_disable_ro(patch->mod);
 709         ret = klp_write_object_relocations(patch->mod, obj);
 710         if (ret) {
 711                 module_enable_ro(patch->mod, true);
 712                 return ret;
 713         }
 714
 715         arch_klp_init_object_loaded(patch, obj);
 716         module_enable_ro(patch->mod, true);
 717
 718         klp_for_each_func(obj, func) {
 719                 ret = klp_find_object_symbol(obj->name, func->old_name,
 720                                              func->old_sympos,
 721                                              &func->old_addr);
 722                 if (ret)
 723                         return ret;
 724
 725                 ret = kallsyms_lookup_size_offset(func->old_addr,
 726                                                   &func->old_size, NULL);
 727                 if (!ret) {
 728                         pr_err("kallsyms size lookup failed for '%s'\n",
 729                                func->old_name);
 730                         return -ENOENT;
 731                 }
 732
 733                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
 734                                                   &func->new_size, NULL);
 735                 if (!ret) {
 736                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
 737                                func->old_name);
 738                         return -ENOENT;
 739                 }
 740         }
 741
 742         return 0;
 743 }
 744
 745 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 746 {
 747         struct klp_func *func;
 748         int ret;
 749         const char *name;
 750
 751         if (!obj->funcs)
 752                 return -EINVAL;
 753
 754         obj->patched = false;
 755         obj->mod = NULL;
 756
 757         klp_find_object_module(obj);
 758
 759         name = klp_is_module(obj) ? obj->name : "vmlinux";
 760         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
 761                                    &patch->kobj, "%s", name);
 762         if (ret)
 763                 return ret;
 764
 765         klp_for_each_func(obj, func) {
 766                 ret = klp_init_func(obj, func);
 767                 if (ret)
 768                         goto free;
 769         }
 770
 771         if (klp_is_object_loaded(obj)) {
 772                 ret = klp_init_object_loaded(patch, obj);
 773                 if (ret)
 774                         goto free;
 775         }
 776
 777         return 0;
 778
 779 free:
 780         klp_free_funcs_limited(obj, func);
 781         kobject_put(&obj->kobj);
 782         return ret;
 783 }
 784
 785 static int klp_init_patch(struct klp_patch *patch)
 786 {
 787         struct klp_object *obj;
 788         int ret;
 789
 790         if (!patch->objs)
 791                 return -EINVAL;
 792
 793         mutex_lock(&klp_mutex);
 794
 795         patch->enabled = false;
 796         init_completion(&patch->finish);
 797
 798         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 799                                    klp_root_kobj, "%s", patch->mod->name);
 800         if (ret) {
 801                 mutex_unlock(&klp_mutex);
 802                 return ret;
 803         }
 804
 805         klp_for_each_object(patch, obj) {
 806                 ret = klp_init_object(patch, obj);
 807                 if (ret)
 808                         goto free;
 809         }
 810
 811         list_add_tail(&patch->list, &klp_patches);
 812
 813         mutex_unlock(&klp_mutex);
 814
 815         return 0;
 816
 817 free:
 818         klp_free_objects_limited(patch, obj);
 819
 820         mutex_unlock(&klp_mutex);
 821
 822         kobject_put(&patch->kobj);
 823         wait_for_completion(&patch->finish);
 824
 825         return ret;
 826 }
 827
 828 /**
 829  * klp_unregister_patch() - unregisters a patch
 830  * @patch:      Disabled patch to be unregistered
 831  *
 832  * Frees the data structures and removes the sysfs interface.
 833  *
 834  * Return: 0 on success, otherwise error
 835  */
 836 int klp_unregister_patch(struct klp_patch *patch)
 837 {
 838         int ret;
 839
 840         mutex_lock(&klp_mutex);
 841
 842         if (!klp_is_patch_registered(patch)) {
 843                 ret = -EINVAL;
 844                 goto err;
 845         }
 846
 847         if (patch->enabled) {
 848                 ret = -EBUSY;
 849                 goto err;
 850         }
 851
 852         klp_free_patch(patch);
 853
 854         mutex_unlock(&klp_mutex);
 855
 856         kobject_put(&patch->kobj);
 857         wait_for_completion(&patch->finish);
 858
 859         return 0;
 860 err:
 861         mutex_unlock(&klp_mutex);
 862         return ret;
 863 }
 864 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 865
 866 /**
 867  * klp_register_patch() - registers a patch
 868  * @patch:      Patch to be registered
 869  *
 870  * Initializes the data structure associated with the patch and
 871  * creates the sysfs interface.
 872  *
 873  * There is no need to take the reference on the patch module here. It is done
 874  * later when the patch is enabled.
 875  *
 876  * Return: 0 on success, otherwise error
 877  */
 878 int klp_register_patch(struct klp_patch *patch)
 879 {
 880         if (!patch || !patch->mod)
 881                 return -EINVAL;
 882
 883         if (!is_livepatch_module(patch->mod)) {
 884                 pr_err("module %s is not marked as a livepatch module\n",
 885                        patch->mod->name);
 886                 return -EINVAL;
 887         }
 888
 889         if (!klp_initialized())
 890                 return -ENODEV;
 891
 892         if (!klp_have_reliable_stack()) {
 893                 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
 894                 return -ENOSYS;
 895         }
 896
 897         return klp_init_patch(patch);
 898 }
 899 EXPORT_SYMBOL_GPL(klp_register_patch);
 900
 901 /*
 902  * Remove parts of patches that touch a given kernel module. The list of
 903  * patches processed might be limited. When limit is NULL, all patches
 904  * will be handled.
 905  */
 906 static void klp_cleanup_module_patches_limited(struct module *mod,
 907                                                struct klp_patch *limit)
 908 {
 909         struct klp_patch *patch;
 910         struct klp_object *obj;
 911
 912         list_for_each_entry(patch, &klp_patches, list) {
 913                 if (patch == limit)
 914                         break;
 915
 916                 klp_for_each_object(patch, obj) {
 917                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 918                                 continue;
 919
 920                         /*
 921                          * Only unpatch the module if the patch is enabled or
 922                          * is in transition.
 923                          */
 924                         if (patch->enabled || patch == klp_transition_patch) {
 925
 926                                 if (patch != klp_transition_patch)
 927                                         klp_pre_unpatch_callback(obj);
 928
 929                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
 930                                           patch->mod->name, obj->mod->name);
 931                                 klp_unpatch_object(obj);
 932
 933                                 klp_post_unpatch_callback(obj);
 934                         }
 935
 936                         klp_free_object_loaded(obj);
 937                         break;
 938                 }
 939         }
 940 }
 941
 942 int klp_module_coming(struct module *mod)
 943 {
 944         int ret;
 945         struct klp_patch *patch;
 946         struct klp_object *obj;
 947
 948         if (WARN_ON(mod->state != MODULE_STATE_COMING))
 949                 return -EINVAL;
 950
 951         mutex_lock(&klp_mutex);
 952         /*
 953          * Each module has to know that klp_module_coming()
 954          * has been called. We never know what module will
 955          * get patched by a new patch.
 956          */
 957         mod->klp_alive = true;
 958
 959         list_for_each_entry(patch, &klp_patches, list) {
 960                 klp_for_each_object(patch, obj) {
 961                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 962                                 continue;
 963
 964                         obj->mod = mod;
 965
 966                         ret = klp_init_object_loaded(patch, obj);
 967                         if (ret) {
 968                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
 969                                         patch->mod->name, obj->mod->name, ret);
 970                                 goto err;
 971                         }
 972
 973                         /*
 974                          * Only patch the module if the patch is enabled or is
 975                          * in transition.
 976                          */
 977                         if (!patch->enabled && patch != klp_transition_patch)
 978                                 break;
 979
 980                         pr_notice("applying patch '%s' to loading module '%s'\n",
 981                                   patch->mod->name, obj->mod->name);
 982
 983                         ret = klp_pre_patch_callback(obj);
 984                         if (ret) {
 985                                 pr_warn("pre-patch callback failed for object '%s'\n",
 986                                         obj->name);
 987                                 goto err;
 988                         }
 989
 990                         ret = klp_patch_object(obj);
 991                         if (ret) {
 992                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 993                                         patch->mod->name, obj->mod->name, ret);
 994
 995                                 klp_post_unpatch_callback(obj);
 996                                 goto err;
 997                         }
 998
 999                         if (patch != klp_transition_patch)
1000                                 klp_post_patch_callback(obj);
1001
1002                         break;
1003                 }
1004         }
1005
1006         mutex_unlock(&klp_mutex);
1007
1008         return 0;
1009
1010 err:
1011         /*
1012          * If a patch is unsuccessfully applied, return
1013          * error to the module loader.
1014          */
1015         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1016                 patch->mod->name, obj->mod->name, obj->mod->name);
1017         mod->klp_alive = false;
1018         klp_cleanup_module_patches_limited(mod, patch);
1019         mutex_unlock(&klp_mutex);
1020
1021         return ret;
1022 }
1023
1024 void klp_module_going(struct module *mod)
1025 {
1026         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1027                     mod->state != MODULE_STATE_COMING))
1028                 return;
1029
1030         mutex_lock(&klp_mutex);
1031         /*
1032          * Each module has to know that klp_module_going()
1033          * has been called. We never know what module will
1034          * get patched by a new patch.
1035          */
1036         mod->klp_alive = false;
1037
1038         klp_cleanup_module_patches_limited(mod, NULL);
1039
1040         mutex_unlock(&klp_mutex);
1041 }
1042
1043 static int __init klp_init(void)
1044 {
1045         int ret;
1046
1047         ret = klp_check_compiler_support();
1048         if (ret) {
1049                 pr_info("Your compiler is too old; turning off.\n");
1050                 return -EINVAL;
1051         }
1052
1053         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1054         if (!klp_root_kobj)
1055                 return -ENOMEM;
1056
1057         return 0;
1058 }
1059
1060 module_init(klp_init);