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 (klp_transition_patch)
 286                 return -EBUSY;
 287
 288         /* enforce stacking: only the last enabled patch can be disabled */
 289         if (!list_is_last(&patch->list, &klp_patches) &&
 290             list_next_entry(patch, list)->enabled)
 291                 return -EBUSY;
 292
 293         klp_init_transition(patch, KLP_UNPATCHED);
 294
 295         klp_for_each_object(patch, obj)
 296                 if (patch->enabled && obj->patched)
 297                         klp_pre_unpatch_callback(obj);
 298
 299         /*
 300          * Enforce the order of the func->transition writes in
 301          * klp_init_transition() and the TIF_PATCH_PENDING writes in
 302          * klp_start_transition().  In the rare case where klp_ftrace_handler()
 303          * is called shortly after klp_update_patch_state() switches the task,
 304          * this ensures the handler sees that func->transition is set.
 305          */
 306         smp_wmb();
 307
 308         klp_start_transition();
 309         klp_try_complete_transition();
 310         patch->enabled = false;
 311
 312         return 0;
 313 }
 314
 315 /**
 316  * klp_disable_patch() - disables a registered patch
 317  * @patch:      The registered, enabled patch to be disabled
 318  *
 319  * Unregisters the patched functions from ftrace.
 320  *
 321  * Return: 0 on success, otherwise error
 322  */
 323 int klp_disable_patch(struct klp_patch *patch)
 324 {
 325         int ret;
 326
 327         mutex_lock(&klp_mutex);
 328
 329         if (!klp_is_patch_registered(patch)) {
 330                 ret = -EINVAL;
 331                 goto err;
 332         }
 333
 334         if (!patch->enabled) {
 335                 ret = -EINVAL;
 336                 goto err;
 337         }
 338
 339         ret = __klp_disable_patch(patch);
 340
 341 err:
 342         mutex_unlock(&klp_mutex);
 343         return ret;
 344 }
 345 EXPORT_SYMBOL_GPL(klp_disable_patch);
 346
 347 static int __klp_enable_patch(struct klp_patch *patch)
 348 {
 349         struct klp_object *obj;
 350         int ret;
 351
 352         if (klp_transition_patch)
 353                 return -EBUSY;
 354
 355         if (WARN_ON(patch->enabled))
 356                 return -EINVAL;
 357
 358         /* enforce stacking: only the first disabled patch can be enabled */
 359         if (patch->list.prev != &klp_patches &&
 360             !list_prev_entry(patch, list)->enabled)
 361                 return -EBUSY;
 362
 363         /*
 364          * A reference is taken on the patch module to prevent it from being
 365          * unloaded.
 366          *
 367          * Note: For immediate (no consistency model) patches we don't allow
 368          * patch modules to unload since there is no safe/sane method to
 369          * determine if a thread is still running in the patched code contained
 370          * in the patch module once the ftrace registration is successful.
 371          */
 372         if (!try_module_get(patch->mod))
 373                 return -ENODEV;
 374
 375         pr_notice("enabling patch '%s'\n", patch->mod->name);
 376
 377         klp_init_transition(patch, KLP_PATCHED);
 378
 379         /*
 380          * Enforce the order of the func->transition writes in
 381          * klp_init_transition() and the ops->func_stack writes in
 382          * klp_patch_object(), so that klp_ftrace_handler() will see the
 383          * func->transition updates before the handler is registered and the
 384          * new funcs become visible to the handler.
 385          */
 386         smp_wmb();
 387
 388         klp_for_each_object(patch, obj) {
 389                 if (!klp_is_object_loaded(obj))
 390                         continue;
 391
 392                 ret = klp_pre_patch_callback(obj);
 393                 if (ret) {
 394                         pr_warn("pre-patch callback failed for object '%s'\n",
 395                                 klp_is_module(obj) ? obj->name : "vmlinux");
 396                         goto err;
 397                 }
 398
 399                 ret = klp_patch_object(obj);
 400                 if (ret) {
 401                         pr_warn("failed to patch object '%s'\n",
 402                                 klp_is_module(obj) ? obj->name : "vmlinux");
 403                         goto err;
 404                 }
 405         }
 406
 407         klp_start_transition();
 408         klp_try_complete_transition();
 409         patch->enabled = true;
 410
 411         return 0;
 412 err:
 413         pr_warn("failed to enable patch '%s'\n", patch->mod->name);
 414
 415         klp_cancel_transition();
 416         return ret;
 417 }
 418
 419 /**
 420  * klp_enable_patch() - enables a registered patch
 421  * @patch:      The registered, disabled patch to be enabled
 422  *
 423  * Performs the needed symbol lookups and code relocations,
 424  * then registers the patched functions with ftrace.
 425  *
 426  * Return: 0 on success, otherwise error
 427  */
 428 int klp_enable_patch(struct klp_patch *patch)
 429 {
 430         int ret;
 431
 432         mutex_lock(&klp_mutex);
 433
 434         if (!klp_is_patch_registered(patch)) {
 435                 ret = -EINVAL;
 436                 goto err;
 437         }
 438
 439         ret = __klp_enable_patch(patch);
 440
 441 err:
 442         mutex_unlock(&klp_mutex);
 443         return ret;
 444 }
 445 EXPORT_SYMBOL_GPL(klp_enable_patch);
 446
 447 /*
 448  * Sysfs Interface
 449  *
 450  * /sys/kernel/livepatch
 451  * /sys/kernel/livepatch/<patch>
 452  * /sys/kernel/livepatch/<patch>/enabled
 453  * /sys/kernel/livepatch/<patch>/transition
 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 struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 529 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
 530 static struct attribute *klp_patch_attrs[] = {
 531         &enabled_kobj_attr.attr,
 532         &transition_kobj_attr.attr,
 533         NULL
 534 };
 535
 536 static void klp_kobj_release_patch(struct kobject *kobj)
 537 {
 538         struct klp_patch *patch;
 539
 540         patch = container_of(kobj, struct klp_patch, kobj);
 541         complete(&patch->finish);
 542 }
 543
 544 static struct kobj_type klp_ktype_patch = {
 545         .release = klp_kobj_release_patch,
 546         .sysfs_ops = &kobj_sysfs_ops,
 547         .default_attrs = klp_patch_attrs,
 548 };
 549
 550 static void klp_kobj_release_object(struct kobject *kobj)
 551 {
 552 }
 553
 554 static struct kobj_type klp_ktype_object = {
 555         .release = klp_kobj_release_object,
 556         .sysfs_ops = &kobj_sysfs_ops,
 557 };
 558
 559 static void klp_kobj_release_func(struct kobject *kobj)
 560 {
 561 }
 562
 563 static struct kobj_type klp_ktype_func = {
 564         .release = klp_kobj_release_func,
 565         .sysfs_ops = &kobj_sysfs_ops,
 566 };
 567
 568 /*
 569  * Free all functions' kobjects in the array up to some limit. When limit is
 570  * NULL, all kobjects are freed.
 571  */
 572 static void klp_free_funcs_limited(struct klp_object *obj,
 573                                    struct klp_func *limit)
 574 {
 575         struct klp_func *func;
 576
 577         for (func = obj->funcs; func->old_name && func != limit; func++)
 578                 kobject_put(&func->kobj);
 579 }
 580
 581 /* Clean up when a patched object is unloaded */
 582 static void klp_free_object_loaded(struct klp_object *obj)
 583 {
 584         struct klp_func *func;
 585
 586         obj->mod = NULL;
 587
 588         klp_for_each_func(obj, func)
 589                 func->old_addr = 0;
 590 }
 591
 592 /*
 593  * Free all objects' kobjects in the array up to some limit. When limit is
 594  * NULL, all kobjects are freed.
 595  */
 596 static void klp_free_objects_limited(struct klp_patch *patch,
 597                                      struct klp_object *limit)
 598 {
 599         struct klp_object *obj;
 600
 601         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 602                 klp_free_funcs_limited(obj, NULL);
 603                 kobject_put(&obj->kobj);
 604         }
 605 }
 606
 607 static void klp_free_patch(struct klp_patch *patch)
 608 {
 609         klp_free_objects_limited(patch, NULL);
 610         if (!list_empty(&patch->list))
 611                 list_del(&patch->list);
 612 }
 613
 614 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 615 {
 616         if (!func->old_name || !func->new_func)
 617                 return -EINVAL;
 618
 619         INIT_LIST_HEAD(&func->stack_node);
 620         func->patched = false;
 621         func->transition = false;
 622
 623         /* The format for the sysfs directory is <function,sympos> where sympos
 624          * is the nth occurrence of this symbol in kallsyms for the patched
 625          * object. If the user selects 0 for old_sympos, then 1 will be used
 626          * since a unique symbol will be the first occurrence.
 627          */
 628         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 629                                     &obj->kobj, "%s,%lu", func->old_name,
 630                                     func->old_sympos ? func->old_sympos : 1);
 631 }
 632
 633 /* Arches may override this to finish any remaining arch-specific tasks */
 634 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
 635                                         struct klp_object *obj)
 636 {
 637 }
 638
 639 /* parts of the initialization that is done only when the object is loaded */
 640 static int klp_init_object_loaded(struct klp_patch *patch,
 641                                   struct klp_object *obj)
 642 {
 643         struct klp_func *func;
 644         int ret;
 645
 646         module_disable_ro(patch->mod);
 647         ret = klp_write_object_relocations(patch->mod, obj);
 648         if (ret) {
 649                 module_enable_ro(patch->mod, true);
 650                 return ret;
 651         }
 652
 653         arch_klp_init_object_loaded(patch, obj);
 654         module_enable_ro(patch->mod, true);
 655
 656         klp_for_each_func(obj, func) {
 657                 ret = klp_find_object_symbol(obj->name, func->old_name,
 658                                              func->old_sympos,
 659                                              &func->old_addr);
 660                 if (ret)
 661                         return ret;
 662
 663                 ret = kallsyms_lookup_size_offset(func->old_addr,
 664                                                   &func->old_size, NULL);
 665                 if (!ret) {
 666                         pr_err("kallsyms size lookup failed for '%s'\n",
 667                                func->old_name);
 668                         return -ENOENT;
 669                 }
 670
 671                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
 672                                                   &func->new_size, NULL);
 673                 if (!ret) {
 674                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
 675                                func->old_name);
 676                         return -ENOENT;
 677                 }
 678         }
 679
 680         return 0;
 681 }
 682
 683 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 684 {
 685         struct klp_func *func;
 686         int ret;
 687         const char *name;
 688
 689         if (!obj->funcs)
 690                 return -EINVAL;
 691
 692         obj->patched = false;
 693         obj->mod = NULL;
 694
 695         klp_find_object_module(obj);
 696
 697         name = klp_is_module(obj) ? obj->name : "vmlinux";
 698         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
 699                                    &patch->kobj, "%s", name);
 700         if (ret)
 701                 return ret;
 702
 703         klp_for_each_func(obj, func) {
 704                 ret = klp_init_func(obj, func);
 705                 if (ret)
 706                         goto free;
 707         }
 708
 709         if (klp_is_object_loaded(obj)) {
 710                 ret = klp_init_object_loaded(patch, obj);
 711                 if (ret)
 712                         goto free;
 713         }
 714
 715         return 0;
 716
 717 free:
 718         klp_free_funcs_limited(obj, func);
 719         kobject_put(&obj->kobj);
 720         return ret;
 721 }
 722
 723 static int klp_init_patch(struct klp_patch *patch)
 724 {
 725         struct klp_object *obj;
 726         int ret;
 727
 728         if (!patch->objs)
 729                 return -EINVAL;
 730
 731         mutex_lock(&klp_mutex);
 732
 733         patch->enabled = false;
 734         init_completion(&patch->finish);
 735
 736         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 737                                    klp_root_kobj, "%s", patch->mod->name);
 738         if (ret) {
 739                 mutex_unlock(&klp_mutex);
 740                 return ret;
 741         }
 742
 743         klp_for_each_object(patch, obj) {
 744                 ret = klp_init_object(patch, obj);
 745                 if (ret)
 746                         goto free;
 747         }
 748
 749         list_add_tail(&patch->list, &klp_patches);
 750
 751         mutex_unlock(&klp_mutex);
 752
 753         return 0;
 754
 755 free:
 756         klp_free_objects_limited(patch, obj);
 757
 758         mutex_unlock(&klp_mutex);
 759
 760         kobject_put(&patch->kobj);
 761         wait_for_completion(&patch->finish);
 762
 763         return ret;
 764 }
 765
 766 /**
 767  * klp_unregister_patch() - unregisters a patch
 768  * @patch:      Disabled patch to be unregistered
 769  *
 770  * Frees the data structures and removes the sysfs interface.
 771  *
 772  * Return: 0 on success, otherwise error
 773  */
 774 int klp_unregister_patch(struct klp_patch *patch)
 775 {
 776         int ret;
 777
 778         mutex_lock(&klp_mutex);
 779
 780         if (!klp_is_patch_registered(patch)) {
 781                 ret = -EINVAL;
 782                 goto err;
 783         }
 784
 785         if (patch->enabled) {
 786                 ret = -EBUSY;
 787                 goto err;
 788         }
 789
 790         klp_free_patch(patch);
 791
 792         mutex_unlock(&klp_mutex);
 793
 794         kobject_put(&patch->kobj);
 795         wait_for_completion(&patch->finish);
 796
 797         return 0;
 798 err:
 799         mutex_unlock(&klp_mutex);
 800         return ret;
 801 }
 802 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 803
 804 /**
 805  * klp_register_patch() - registers a patch
 806  * @patch:      Patch to be registered
 807  *
 808  * Initializes the data structure associated with the patch and
 809  * creates the sysfs interface.
 810  *
 811  * There is no need to take the reference on the patch module here. It is done
 812  * later when the patch is enabled.
 813  *
 814  * Return: 0 on success, otherwise error
 815  */
 816 int klp_register_patch(struct klp_patch *patch)
 817 {
 818         if (!patch || !patch->mod)
 819                 return -EINVAL;
 820
 821         if (!is_livepatch_module(patch->mod)) {
 822                 pr_err("module %s is not marked as a livepatch module\n",
 823                        patch->mod->name);
 824                 return -EINVAL;
 825         }
 826
 827         if (!klp_initialized())
 828                 return -ENODEV;
 829
 830         /*
 831          * Architectures without reliable stack traces have to set
 832          * patch->immediate because there's currently no way to patch kthreads
 833          * with the consistency model.
 834          */
 835         if (!klp_have_reliable_stack() && !patch->immediate) {
 836                 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
 837                 return -ENOSYS;
 838         }
 839
 840         return klp_init_patch(patch);
 841 }
 842 EXPORT_SYMBOL_GPL(klp_register_patch);
 843
 844 int klp_module_coming(struct module *mod)
 845 {
 846         int ret;
 847         struct klp_patch *patch;
 848         struct klp_object *obj;
 849
 850         if (WARN_ON(mod->state != MODULE_STATE_COMING))
 851                 return -EINVAL;
 852
 853         mutex_lock(&klp_mutex);
 854         /*
 855          * Each module has to know that klp_module_coming()
 856          * has been called. We never know what module will
 857          * get patched by a new patch.
 858          */
 859         mod->klp_alive = true;
 860
 861         list_for_each_entry(patch, &klp_patches, list) {
 862                 klp_for_each_object(patch, obj) {
 863                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 864                                 continue;
 865
 866                         obj->mod = mod;
 867
 868                         ret = klp_init_object_loaded(patch, obj);
 869                         if (ret) {
 870                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
 871                                         patch->mod->name, obj->mod->name, ret);
 872                                 goto err;
 873                         }
 874
 875                         /*
 876                          * Only patch the module if the patch is enabled or is
 877                          * in transition.
 878                          */
 879                         if (!patch->enabled && patch != klp_transition_patch)
 880                                 break;
 881
 882                         pr_notice("applying patch '%s' to loading module '%s'\n",
 883                                   patch->mod->name, obj->mod->name);
 884
 885                         ret = klp_pre_patch_callback(obj);
 886                         if (ret) {
 887                                 pr_warn("pre-patch callback failed for object '%s'\n",
 888                                         obj->name);
 889                                 goto err;
 890                         }
 891
 892                         ret = klp_patch_object(obj);
 893                         if (ret) {
 894                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 895                                         patch->mod->name, obj->mod->name, ret);
 896
 897                                 if (patch != klp_transition_patch)
 898                                         klp_post_unpatch_callback(obj);
 899
 900                                 goto err;
 901                         }
 902
 903                         if (patch != klp_transition_patch)
 904                                 klp_post_patch_callback(obj);
 905
 906                         break;
 907                 }
 908         }
 909
 910         mutex_unlock(&klp_mutex);
 911
 912         return 0;
 913
 914 err:
 915         /*
 916          * If a patch is unsuccessfully applied, return
 917          * error to the module loader.
 918          */
 919         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
 920                 patch->mod->name, obj->mod->name, obj->mod->name);
 921         mod->klp_alive = false;
 922         klp_free_object_loaded(obj);
 923         mutex_unlock(&klp_mutex);
 924
 925         return ret;
 926 }
 927
 928 void klp_module_going(struct module *mod)
 929 {
 930         struct klp_patch *patch;
 931         struct klp_object *obj;
 932
 933         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
 934                     mod->state != MODULE_STATE_COMING))
 935                 return;
 936
 937         mutex_lock(&klp_mutex);
 938         /*
 939          * Each module has to know that klp_module_going()
 940          * has been called. We never know what module will
 941          * get patched by a new patch.
 942          */
 943         mod->klp_alive = false;
 944
 945         list_for_each_entry(patch, &klp_patches, list) {
 946                 klp_for_each_object(patch, obj) {
 947                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 948                                 continue;
 949
 950                         /*
 951                          * Only unpatch the module if the patch is enabled or
 952                          * is in transition.
 953                          */
 954                         if (patch->enabled || patch == klp_transition_patch) {
 955
 956                                 if (patch != klp_transition_patch)
 957                                         klp_pre_unpatch_callback(obj);
 958
 959                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
 960                                           patch->mod->name, obj->mod->name);
 961                                 klp_unpatch_object(obj);
 962
 963                                 klp_post_unpatch_callback(obj);
 964                         }
 965
 966                         klp_free_object_loaded(obj);
 967                         break;
 968                 }
 969         }
 970
 971         mutex_unlock(&klp_mutex);
 972 }
 973
 974 static int __init klp_init(void)
 975 {
 976         int ret;
 977
 978         ret = klp_check_compiler_support();
 979         if (ret) {
 980                 pr_info("Your compiler is too old; turning off.\n");
 981                 return -EINVAL;
 982         }
 983
 984         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
 985         if (!klp_root_kobj)
 986                 return -ENOMEM;
 987
 988         return 0;
 989 }
 990
 991 module_init(klp_init);