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 <linux/elf.h>
  32 #include <linux/moduleloader.h>
  33 #include <asm/cacheflush.h>
  34
  35 /**
  36  * struct klp_ops - structure for tracking registered ftrace ops structs
  37  *
  38  * A single ftrace_ops is shared between all enabled replacement functions
  39  * (klp_func structs) which have the same old_addr.  This allows the switch
  40  * between function versions to happen instantaneously by updating the klp_ops
  41  * struct's func_stack list.  The winner is the klp_func at the top of the
  42  * func_stack (front of the list).
  43  *
  44  * @node:       node for the global klp_ops list
  45  * @func_stack: list head for the stack of klp_func's (active func is on top)
  46  * @fops:       registered ftrace ops struct
  47  */
  48 struct klp_ops {
  49         struct list_head node;
  50         struct list_head func_stack;
  51         struct ftrace_ops fops;
  52 };
  53
  54 /*
  55  * The klp_mutex protects the global lists and state transitions of any
  56  * structure reachable from them.  References to any structure must be obtained
  57  * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
  58  * ensure it gets consistent data).
  59  */
  60 static DEFINE_MUTEX(klp_mutex);
  61
  62 static LIST_HEAD(klp_patches);
  63 static LIST_HEAD(klp_ops);
  64
  65 static struct kobject *klp_root_kobj;
  66
  67 static struct klp_ops *klp_find_ops(unsigned long old_addr)
  68 {
  69         struct klp_ops *ops;
  70         struct klp_func *func;
  71
  72         list_for_each_entry(ops, &klp_ops, node) {
  73                 func = list_first_entry(&ops->func_stack, struct klp_func,
  74                                         stack_node);
  75                 if (func->old_addr == old_addr)
  76                         return ops;
  77         }
  78
  79         return NULL;
  80 }
  81
  82 static bool klp_is_module(struct klp_object *obj)
  83 {
  84         return obj->name;
  85 }
  86
  87 static bool klp_is_object_loaded(struct klp_object *obj)
  88 {
  89         return !obj->name || obj->mod;
  90 }
  91
  92 /* sets obj->mod if object is not vmlinux and module is found */
  93 static void klp_find_object_module(struct klp_object *obj)
  94 {
  95         struct module *mod;
  96
  97         if (!klp_is_module(obj))
  98                 return;
  99
 100         mutex_lock(&module_mutex);
 101         /*
 102          * We do not want to block removal of patched modules and therefore
 103          * we do not take a reference here. The patches are removed by
 104          * klp_module_going() instead.
 105          */
 106         mod = find_module(obj->name);
 107         /*
 108          * Do not mess work of klp_module_coming() and klp_module_going().
 109          * Note that the patch might still be needed before klp_module_going()
 110          * is called. Module functions can be called even in the GOING state
 111          * until mod->exit() finishes. This is especially important for
 112          * patches that modify semantic of the functions.
 113          */
 114         if (mod && mod->klp_alive)
 115                 obj->mod = mod;
 116
 117         mutex_unlock(&module_mutex);
 118 }
 119
 120 /* klp_mutex must be held by caller */
 121 static bool klp_is_patch_registered(struct klp_patch *patch)
 122 {
 123         struct klp_patch *mypatch;
 124
 125         list_for_each_entry(mypatch, &klp_patches, list)
 126                 if (mypatch == patch)
 127                         return true;
 128
 129         return false;
 130 }
 131
 132 static bool klp_initialized(void)
 133 {
 134         return !!klp_root_kobj;
 135 }
 136
 137 struct klp_find_arg {
 138         const char *objname;
 139         const char *name;
 140         unsigned long addr;
 141         unsigned long count;
 142         unsigned long pos;
 143 };
 144
 145 static int klp_find_callback(void *data, const char *name,
 146                              struct module *mod, unsigned long addr)
 147 {
 148         struct klp_find_arg *args = data;
 149
 150         if ((mod && !args->objname) || (!mod && args->objname))
 151                 return 0;
 152
 153         if (strcmp(args->name, name))
 154                 return 0;
 155
 156         if (args->objname && strcmp(args->objname, mod->name))
 157                 return 0;
 158
 159         args->addr = addr;
 160         args->count++;
 161
 162         /*
 163          * Finish the search when the symbol is found for the desired position
 164          * or the position is not defined for a non-unique symbol.
 165          */
 166         if ((args->pos && (args->count == args->pos)) ||
 167             (!args->pos && (args->count > 1)))
 168                 return 1;
 169
 170         return 0;
 171 }
 172
 173 static int klp_find_object_symbol(const char *objname, const char *name,
 174                                   unsigned long sympos, unsigned long *addr)
 175 {
 176         struct klp_find_arg args = {
 177                 .objname = objname,
 178                 .name = name,
 179                 .addr = 0,
 180                 .count = 0,
 181                 .pos = sympos,
 182         };
 183
 184         mutex_lock(&module_mutex);
 185         kallsyms_on_each_symbol(klp_find_callback, &args);
 186         mutex_unlock(&module_mutex);
 187
 188         /*
 189          * Ensure an address was found. If sympos is 0, ensure symbol is unique;
 190          * otherwise ensure the symbol position count matches sympos.
 191          */
 192         if (args.addr == 0)
 193                 pr_err("symbol '%s' not found in symbol table\n", name);
 194         else if (args.count > 1 && sympos == 0) {
 195                 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
 196                        name, objname);
 197         } else if (sympos != args.count && sympos > 0) {
 198                 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
 199                        sympos, name, objname ? objname : "vmlinux");
 200         } else {
 201                 *addr = args.addr;
 202                 return 0;
 203         }
 204
 205         *addr = 0;
 206         return -EINVAL;
 207 }
 208
 209 static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 210 {
 211         int i, cnt, vmlinux, ret;
 212         char objname[MODULE_NAME_LEN];
 213         char symname[KSYM_NAME_LEN];
 214         char *strtab = pmod->core_kallsyms.strtab;
 215         Elf_Rela *relas;
 216         Elf_Sym *sym;
 217         unsigned long sympos, addr;
 218
 219         /*
 220          * Since the field widths for objname and symname in the sscanf()
 221          * call are hard-coded and correspond to MODULE_NAME_LEN and
 222          * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
 223          * and KSYM_NAME_LEN have the values we expect them to have.
 224          *
 225          * Because the value of MODULE_NAME_LEN can differ among architectures,
 226          * we use the smallest/strictest upper bound possible (56, based on
 227          * the current definition of MODULE_NAME_LEN) to prevent overflows.
 228          */
 229         BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
 230
 231         relas = (Elf_Rela *) relasec->sh_addr;
 232         /* For each rela in this klp relocation section */
 233         for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
 234                 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
 235                 if (sym->st_shndx != SHN_LIVEPATCH) {
 236                         pr_err("symbol %s is not marked as a livepatch symbol",
 237                                strtab + sym->st_name);
 238                         return -EINVAL;
 239                 }
 240
 241                 /* Format: .klp.sym.objname.symname,sympos */
 242                 cnt = sscanf(strtab + sym->st_name,
 243                              ".klp.sym.%55[^.].%127[^,],%lu",
 244                              objname, symname, &sympos);
 245                 if (cnt != 3) {
 246                         pr_err("symbol %s has an incorrectly formatted name",
 247                                strtab + sym->st_name);
 248                         return -EINVAL;
 249                 }
 250
 251                 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
 252                 vmlinux = !strcmp(objname, "vmlinux");
 253                 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
 254                                              symname, sympos, &addr);
 255                 if (ret)
 256                         return ret;
 257
 258                 sym->st_value = addr;
 259         }
 260
 261         return 0;
 262 }
 263
 264 static int klp_write_object_relocations(struct module *pmod,
 265                                         struct klp_object *obj)
 266 {
 267         int i, cnt, ret = 0;
 268         const char *objname, *secname;
 269         char sec_objname[MODULE_NAME_LEN];
 270         Elf_Shdr *sec;
 271
 272         if (WARN_ON(!klp_is_object_loaded(obj)))
 273                 return -EINVAL;
 274
 275         objname = klp_is_module(obj) ? obj->name : "vmlinux";
 276
 277         /* For each klp relocation section */
 278         for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
 279                 sec = pmod->klp_info->sechdrs + i;
 280                 secname = pmod->klp_info->secstrings + sec->sh_name;
 281                 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
 282                         continue;
 283
 284                 /*
 285                  * Format: .klp.rela.sec_objname.section_name
 286                  * See comment in klp_resolve_symbols() for an explanation
 287                  * of the selected field width value.
 288                  */
 289                 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
 290                 if (cnt != 1) {
 291                         pr_err("section %s has an incorrectly formatted name",
 292                                secname);
 293                         ret = -EINVAL;
 294                         break;
 295                 }
 296
 297                 if (strcmp(objname, sec_objname))
 298                         continue;
 299
 300                 ret = klp_resolve_symbols(sec, pmod);
 301                 if (ret)
 302                         break;
 303
 304                 ret = apply_relocate_add(pmod->klp_info->sechdrs,
 305                                          pmod->core_kallsyms.strtab,
 306                                          pmod->klp_info->symndx, i, pmod);
 307                 if (ret)
 308                         break;
 309         }
 310
 311         return ret;
 312 }
 313
 314 static void notrace klp_ftrace_handler(unsigned long ip,
 315                                        unsigned long parent_ip,
 316                                        struct ftrace_ops *fops,
 317                                        struct pt_regs *regs)
 318 {
 319         struct klp_ops *ops;
 320         struct klp_func *func;
 321
 322         ops = container_of(fops, struct klp_ops, fops);
 323
 324         rcu_read_lock();
 325         func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
 326                                       stack_node);
 327         if (WARN_ON_ONCE(!func))
 328                 goto unlock;
 329
 330         klp_arch_set_pc(regs, (unsigned long)func->new_func);
 331 unlock:
 332         rcu_read_unlock();
 333 }
 334
 335 /*
 336  * Convert a function address into the appropriate ftrace location.
 337  *
 338  * Usually this is just the address of the function, but on some architectures
 339  * it's more complicated so allow them to provide a custom behaviour.
 340  */
 341 #ifndef klp_get_ftrace_location
 342 static unsigned long klp_get_ftrace_location(unsigned long faddr)
 343 {
 344         return faddr;
 345 }
 346 #endif
 347
 348 static void klp_disable_func(struct klp_func *func)
 349 {
 350         struct klp_ops *ops;
 351
 352         if (WARN_ON(func->state != KLP_ENABLED))
 353                 return;
 354         if (WARN_ON(!func->old_addr))
 355                 return;
 356
 357         ops = klp_find_ops(func->old_addr);
 358         if (WARN_ON(!ops))
 359                 return;
 360
 361         if (list_is_singular(&ops->func_stack)) {
 362                 unsigned long ftrace_loc;
 363
 364                 ftrace_loc = klp_get_ftrace_location(func->old_addr);
 365                 if (WARN_ON(!ftrace_loc))
 366                         return;
 367
 368                 WARN_ON(unregister_ftrace_function(&ops->fops));
 369                 WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
 370
 371                 list_del_rcu(&func->stack_node);
 372                 list_del(&ops->node);
 373                 kfree(ops);
 374         } else {
 375                 list_del_rcu(&func->stack_node);
 376         }
 377
 378         func->state = KLP_DISABLED;
 379 }
 380
 381 static int klp_enable_func(struct klp_func *func)
 382 {
 383         struct klp_ops *ops;
 384         int ret;
 385
 386         if (WARN_ON(!func->old_addr))
 387                 return -EINVAL;
 388
 389         if (WARN_ON(func->state != KLP_DISABLED))
 390                 return -EINVAL;
 391
 392         ops = klp_find_ops(func->old_addr);
 393         if (!ops) {
 394                 unsigned long ftrace_loc;
 395
 396                 ftrace_loc = klp_get_ftrace_location(func->old_addr);
 397                 if (!ftrace_loc) {
 398                         pr_err("failed to find location for function '%s'\n",
 399                                 func->old_name);
 400                         return -EINVAL;
 401                 }
 402
 403                 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
 404                 if (!ops)
 405                         return -ENOMEM;
 406
 407                 ops->fops.func = klp_ftrace_handler;
 408                 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
 409                                   FTRACE_OPS_FL_DYNAMIC |
 410                                   FTRACE_OPS_FL_IPMODIFY;
 411
 412                 list_add(&ops->node, &klp_ops);
 413
 414                 INIT_LIST_HEAD(&ops->func_stack);
 415                 list_add_rcu(&func->stack_node, &ops->func_stack);
 416
 417                 ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
 418                 if (ret) {
 419                         pr_err("failed to set ftrace filter for function '%s' (%d)\n",
 420                                func->old_name, ret);
 421                         goto err;
 422                 }
 423
 424                 ret = register_ftrace_function(&ops->fops);
 425                 if (ret) {
 426                         pr_err("failed to register ftrace handler for function '%s' (%d)\n",
 427                                func->old_name, ret);
 428                         ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
 429                         goto err;
 430                 }
 431
 432
 433         } else {
 434                 list_add_rcu(&func->stack_node, &ops->func_stack);
 435         }
 436
 437         func->state = KLP_ENABLED;
 438
 439         return 0;
 440
 441 err:
 442         list_del_rcu(&func->stack_node);
 443         list_del(&ops->node);
 444         kfree(ops);
 445         return ret;
 446 }
 447
 448 static void klp_disable_object(struct klp_object *obj)
 449 {
 450         struct klp_func *func;
 451
 452         klp_for_each_func(obj, func)
 453                 if (func->state == KLP_ENABLED)
 454                         klp_disable_func(func);
 455
 456         obj->state = KLP_DISABLED;
 457 }
 458
 459 static int klp_enable_object(struct klp_object *obj)
 460 {
 461         struct klp_func *func;
 462         int ret;
 463
 464         if (WARN_ON(obj->state != KLP_DISABLED))
 465                 return -EINVAL;
 466
 467         if (WARN_ON(!klp_is_object_loaded(obj)))
 468                 return -EINVAL;
 469
 470         klp_for_each_func(obj, func) {
 471                 ret = klp_enable_func(func);
 472                 if (ret) {
 473                         klp_disable_object(obj);
 474                         return ret;
 475                 }
 476         }
 477         obj->state = KLP_ENABLED;
 478
 479         return 0;
 480 }
 481
 482 static int __klp_disable_patch(struct klp_patch *patch)
 483 {
 484         struct klp_object *obj;
 485
 486         /* enforce stacking: only the last enabled patch can be disabled */
 487         if (!list_is_last(&patch->list, &klp_patches) &&
 488             list_next_entry(patch, list)->state == KLP_ENABLED)
 489                 return -EBUSY;
 490
 491         pr_notice("disabling patch '%s'\n", patch->mod->name);
 492
 493         klp_for_each_object(patch, obj) {
 494                 if (obj->state == KLP_ENABLED)
 495                         klp_disable_object(obj);
 496         }
 497
 498         patch->state = KLP_DISABLED;
 499
 500         return 0;
 501 }
 502
 503 /**
 504  * klp_disable_patch() - disables a registered patch
 505  * @patch:      The registered, enabled patch to be disabled
 506  *
 507  * Unregisters the patched functions from ftrace.
 508  *
 509  * Return: 0 on success, otherwise error
 510  */
 511 int klp_disable_patch(struct klp_patch *patch)
 512 {
 513         int ret;
 514
 515         mutex_lock(&klp_mutex);
 516
 517         if (!klp_is_patch_registered(patch)) {
 518                 ret = -EINVAL;
 519                 goto err;
 520         }
 521
 522         if (patch->state == KLP_DISABLED) {
 523                 ret = -EINVAL;
 524                 goto err;
 525         }
 526
 527         ret = __klp_disable_patch(patch);
 528
 529 err:
 530         mutex_unlock(&klp_mutex);
 531         return ret;
 532 }
 533 EXPORT_SYMBOL_GPL(klp_disable_patch);
 534
 535 static int __klp_enable_patch(struct klp_patch *patch)
 536 {
 537         struct klp_object *obj;
 538         int ret;
 539
 540         if (WARN_ON(patch->state != KLP_DISABLED))
 541                 return -EINVAL;
 542
 543         /* enforce stacking: only the first disabled patch can be enabled */
 544         if (patch->list.prev != &klp_patches &&
 545             list_prev_entry(patch, list)->state == KLP_DISABLED)
 546                 return -EBUSY;
 547
 548         pr_notice("enabling patch '%s'\n", patch->mod->name);
 549
 550         klp_for_each_object(patch, obj) {
 551                 if (!klp_is_object_loaded(obj))
 552                         continue;
 553
 554                 ret = klp_enable_object(obj);
 555                 if (ret)
 556                         goto unregister;
 557         }
 558
 559         patch->state = KLP_ENABLED;
 560
 561         return 0;
 562
 563 unregister:
 564         WARN_ON(__klp_disable_patch(patch));
 565         return ret;
 566 }
 567
 568 /**
 569  * klp_enable_patch() - enables a registered patch
 570  * @patch:      The registered, disabled patch to be enabled
 571  *
 572  * Performs the needed symbol lookups and code relocations,
 573  * then registers the patched functions with ftrace.
 574  *
 575  * Return: 0 on success, otherwise error
 576  */
 577 int klp_enable_patch(struct klp_patch *patch)
 578 {
 579         int ret;
 580
 581         mutex_lock(&klp_mutex);
 582
 583         if (!klp_is_patch_registered(patch)) {
 584                 ret = -EINVAL;
 585                 goto err;
 586         }
 587
 588         ret = __klp_enable_patch(patch);
 589
 590 err:
 591         mutex_unlock(&klp_mutex);
 592         return ret;
 593 }
 594 EXPORT_SYMBOL_GPL(klp_enable_patch);
 595
 596 /*
 597  * Sysfs Interface
 598  *
 599  * /sys/kernel/livepatch
 600  * /sys/kernel/livepatch/<patch>
 601  * /sys/kernel/livepatch/<patch>/enabled
 602  * /sys/kernel/livepatch/<patch>/<object>
 603  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
 604  */
 605
 606 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 607                              const char *buf, size_t count)
 608 {
 609         struct klp_patch *patch;
 610         int ret;
 611         unsigned long val;
 612
 613         ret = kstrtoul(buf, 10, &val);
 614         if (ret)
 615                 return -EINVAL;
 616
 617         if (val != KLP_DISABLED && val != KLP_ENABLED)
 618                 return -EINVAL;
 619
 620         patch = container_of(kobj, struct klp_patch, kobj);
 621
 622         mutex_lock(&klp_mutex);
 623
 624         if (val == patch->state) {
 625                 /* already in requested state */
 626                 ret = -EINVAL;
 627                 goto err;
 628         }
 629
 630         if (val == KLP_ENABLED) {
 631                 ret = __klp_enable_patch(patch);
 632                 if (ret)
 633                         goto err;
 634         } else {
 635                 ret = __klp_disable_patch(patch);
 636                 if (ret)
 637                         goto err;
 638         }
 639
 640         mutex_unlock(&klp_mutex);
 641
 642         return count;
 643
 644 err:
 645         mutex_unlock(&klp_mutex);
 646         return ret;
 647 }
 648
 649 static ssize_t enabled_show(struct kobject *kobj,
 650                             struct kobj_attribute *attr, char *buf)
 651 {
 652         struct klp_patch *patch;
 653
 654         patch = container_of(kobj, struct klp_patch, kobj);
 655         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
 656 }
 657
 658 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 659 static struct attribute *klp_patch_attrs[] = {
 660         &enabled_kobj_attr.attr,
 661         NULL
 662 };
 663
 664 static void klp_kobj_release_patch(struct kobject *kobj)
 665 {
 666         /*
 667          * Once we have a consistency model we'll need to module_put() the
 668          * patch module here.  See klp_register_patch() for more details.
 669          */
 670 }
 671
 672 static struct kobj_type klp_ktype_patch = {
 673         .release = klp_kobj_release_patch,
 674         .sysfs_ops = &kobj_sysfs_ops,
 675         .default_attrs = klp_patch_attrs,
 676 };
 677
 678 static void klp_kobj_release_object(struct kobject *kobj)
 679 {
 680 }
 681
 682 static struct kobj_type klp_ktype_object = {
 683         .release = klp_kobj_release_object,
 684         .sysfs_ops = &kobj_sysfs_ops,
 685 };
 686
 687 static void klp_kobj_release_func(struct kobject *kobj)
 688 {
 689 }
 690
 691 static struct kobj_type klp_ktype_func = {
 692         .release = klp_kobj_release_func,
 693         .sysfs_ops = &kobj_sysfs_ops,
 694 };
 695
 696 /*
 697  * Free all functions' kobjects in the array up to some limit. When limit is
 698  * NULL, all kobjects are freed.
 699  */
 700 static void klp_free_funcs_limited(struct klp_object *obj,
 701                                    struct klp_func *limit)
 702 {
 703         struct klp_func *func;
 704
 705         for (func = obj->funcs; func->old_name && func != limit; func++)
 706                 kobject_put(&func->kobj);
 707 }
 708
 709 /* Clean up when a patched object is unloaded */
 710 static void klp_free_object_loaded(struct klp_object *obj)
 711 {
 712         struct klp_func *func;
 713
 714         obj->mod = NULL;
 715
 716         klp_for_each_func(obj, func)
 717                 func->old_addr = 0;
 718 }
 719
 720 /*
 721  * Free all objects' kobjects in the array up to some limit. When limit is
 722  * NULL, all kobjects are freed.
 723  */
 724 static void klp_free_objects_limited(struct klp_patch *patch,
 725                                      struct klp_object *limit)
 726 {
 727         struct klp_object *obj;
 728
 729         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
 730                 klp_free_funcs_limited(obj, NULL);
 731                 kobject_put(&obj->kobj);
 732         }
 733 }
 734
 735 static void klp_free_patch(struct klp_patch *patch)
 736 {
 737         klp_free_objects_limited(patch, NULL);
 738         if (!list_empty(&patch->list))
 739                 list_del(&patch->list);
 740         kobject_put(&patch->kobj);
 741 }
 742
 743 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 744 {
 745         if (!func->old_name || !func->new_func)
 746                 return -EINVAL;
 747
 748         INIT_LIST_HEAD(&func->stack_node);
 749         func->state = KLP_DISABLED;
 750
 751         /* The format for the sysfs directory is <function,sympos> where sympos
 752          * is the nth occurrence of this symbol in kallsyms for the patched
 753          * object. If the user selects 0 for old_sympos, then 1 will be used
 754          * since a unique symbol will be the first occurrence.
 755          */
 756         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
 757                                     &obj->kobj, "%s,%lu", func->old_name,
 758                                     func->old_sympos ? func->old_sympos : 1);
 759 }
 760
 761 /* Arches may override this to finish any remaining arch-specific tasks */
 762 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
 763                                         struct klp_object *obj)
 764 {
 765 }
 766
 767 /* parts of the initialization that is done only when the object is loaded */
 768 static int klp_init_object_loaded(struct klp_patch *patch,
 769                                   struct klp_object *obj)
 770 {
 771         struct klp_func *func;
 772         int ret;
 773
 774         module_disable_ro(patch->mod);
 775         ret = klp_write_object_relocations(patch->mod, obj);
 776         if (ret) {
 777                 module_enable_ro(patch->mod, true);
 778                 return ret;
 779         }
 780
 781         arch_klp_init_object_loaded(patch, obj);
 782         module_enable_ro(patch->mod, true);
 783
 784         klp_for_each_func(obj, func) {
 785                 ret = klp_find_object_symbol(obj->name, func->old_name,
 786                                              func->old_sympos,
 787                                              &func->old_addr);
 788                 if (ret)
 789                         return ret;
 790         }
 791
 792         return 0;
 793 }
 794
 795 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 796 {
 797         struct klp_func *func;
 798         int ret;
 799         const char *name;
 800
 801         if (!obj->funcs)
 802                 return -EINVAL;
 803
 804         obj->state = KLP_DISABLED;
 805         obj->mod = NULL;
 806
 807         klp_find_object_module(obj);
 808
 809         name = klp_is_module(obj) ? obj->name : "vmlinux";
 810         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
 811                                    &patch->kobj, "%s", name);
 812         if (ret)
 813                 return ret;
 814
 815         klp_for_each_func(obj, func) {
 816                 ret = klp_init_func(obj, func);
 817                 if (ret)
 818                         goto free;
 819         }
 820
 821         if (klp_is_object_loaded(obj)) {
 822                 ret = klp_init_object_loaded(patch, obj);
 823                 if (ret)
 824                         goto free;
 825         }
 826
 827         return 0;
 828
 829 free:
 830         klp_free_funcs_limited(obj, func);
 831         kobject_put(&obj->kobj);
 832         return ret;
 833 }
 834
 835 static int klp_init_patch(struct klp_patch *patch)
 836 {
 837         struct klp_object *obj;
 838         int ret;
 839
 840         if (!patch->objs)
 841                 return -EINVAL;
 842
 843         mutex_lock(&klp_mutex);
 844
 845         patch->state = KLP_DISABLED;
 846
 847         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
 848                                    klp_root_kobj, "%s", patch->mod->name);
 849         if (ret)
 850                 goto unlock;
 851
 852         klp_for_each_object(patch, obj) {
 853                 ret = klp_init_object(patch, obj);
 854                 if (ret)
 855                         goto free;
 856         }
 857
 858         list_add_tail(&patch->list, &klp_patches);
 859
 860         mutex_unlock(&klp_mutex);
 861
 862         return 0;
 863
 864 free:
 865         klp_free_objects_limited(patch, obj);
 866         kobject_put(&patch->kobj);
 867 unlock:
 868         mutex_unlock(&klp_mutex);
 869         return ret;
 870 }
 871
 872 /**
 873  * klp_unregister_patch() - unregisters a patch
 874  * @patch:      Disabled patch to be unregistered
 875  *
 876  * Frees the data structures and removes the sysfs interface.
 877  *
 878  * Return: 0 on success, otherwise error
 879  */
 880 int klp_unregister_patch(struct klp_patch *patch)
 881 {
 882         int ret = 0;
 883
 884         mutex_lock(&klp_mutex);
 885
 886         if (!klp_is_patch_registered(patch)) {
 887                 ret = -EINVAL;
 888                 goto out;
 889         }
 890
 891         if (patch->state == KLP_ENABLED) {
 892                 ret = -EBUSY;
 893                 goto out;
 894         }
 895
 896         klp_free_patch(patch);
 897
 898 out:
 899         mutex_unlock(&klp_mutex);
 900         return ret;
 901 }
 902 EXPORT_SYMBOL_GPL(klp_unregister_patch);
 903
 904 /**
 905  * klp_register_patch() - registers a patch
 906  * @patch:      Patch to be registered
 907  *
 908  * Initializes the data structure associated with the patch and
 909  * creates the sysfs interface.
 910  *
 911  * Return: 0 on success, otherwise error
 912  */
 913 int klp_register_patch(struct klp_patch *patch)
 914 {
 915         int ret;
 916
 917         if (!patch || !patch->mod)
 918                 return -EINVAL;
 919
 920         if (!is_livepatch_module(patch->mod)) {
 921                 pr_err("module %s is not marked as a livepatch module",
 922                        patch->mod->name);
 923                 return -EINVAL;
 924         }
 925
 926         if (!klp_initialized())
 927                 return -ENODEV;
 928
 929         /*
 930          * A reference is taken on the patch module to prevent it from being
 931          * unloaded.  Right now, we don't allow patch modules to unload since
 932          * there is currently no method to determine if a thread is still
 933          * running in the patched code contained in the patch module once
 934          * the ftrace registration is successful.
 935          */
 936         if (!try_module_get(patch->mod))
 937                 return -ENODEV;
 938
 939         ret = klp_init_patch(patch);
 940         if (ret)
 941                 module_put(patch->mod);
 942
 943         return ret;
 944 }
 945 EXPORT_SYMBOL_GPL(klp_register_patch);
 946
 947 int klp_module_coming(struct module *mod)
 948 {
 949         int ret;
 950         struct klp_patch *patch;
 951         struct klp_object *obj;
 952
 953         if (WARN_ON(mod->state != MODULE_STATE_COMING))
 954                 return -EINVAL;
 955
 956         mutex_lock(&klp_mutex);
 957         /*
 958          * Each module has to know that klp_module_coming()
 959          * has been called. We never know what module will
 960          * get patched by a new patch.
 961          */
 962         mod->klp_alive = true;
 963
 964         list_for_each_entry(patch, &klp_patches, list) {
 965                 klp_for_each_object(patch, obj) {
 966                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 967                                 continue;
 968
 969                         obj->mod = mod;
 970
 971                         ret = klp_init_object_loaded(patch, obj);
 972                         if (ret) {
 973                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
 974                                         patch->mod->name, obj->mod->name, ret);
 975                                 goto err;
 976                         }
 977
 978                         if (patch->state == KLP_DISABLED)
 979                                 break;
 980
 981                         pr_notice("applying patch '%s' to loading module '%s'\n",
 982                                   patch->mod->name, obj->mod->name);
 983
 984                         ret = klp_enable_object(obj);
 985                         if (ret) {
 986                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
 987                                         patch->mod->name, obj->mod->name, ret);
 988                                 goto err;
 989                         }
 990
 991                         break;
 992                 }
 993         }
 994
 995         mutex_unlock(&klp_mutex);
 996
 997         return 0;
 998
 999 err:
1000         /*
1001          * If a patch is unsuccessfully applied, return
1002          * error to the module loader.
1003          */
1004         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1005                 patch->mod->name, obj->mod->name, obj->mod->name);
1006         mod->klp_alive = false;
1007         klp_free_object_loaded(obj);
1008         mutex_unlock(&klp_mutex);
1009
1010         return ret;
1011 }
1012
1013 void klp_module_going(struct module *mod)
1014 {
1015         struct klp_patch *patch;
1016         struct klp_object *obj;
1017
1018         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1019                     mod->state != MODULE_STATE_COMING))
1020                 return;
1021
1022         mutex_lock(&klp_mutex);
1023         /*
1024          * Each module has to know that klp_module_going()
1025          * has been called. We never know what module will
1026          * get patched by a new patch.
1027          */
1028         mod->klp_alive = false;
1029
1030         list_for_each_entry(patch, &klp_patches, list) {
1031                 klp_for_each_object(patch, obj) {
1032                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1033                                 continue;
1034
1035                         if (patch->state != KLP_DISABLED) {
1036                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1037                                           patch->mod->name, obj->mod->name);
1038                                 klp_disable_object(obj);
1039                         }
1040
1041                         klp_free_object_loaded(obj);
1042                         break;
1043                 }
1044         }
1045
1046         mutex_unlock(&klp_mutex);
1047 }
1048
1049 static int __init klp_init(void)
1050 {
1051         int ret;
1052
1053         ret = klp_check_compiler_support();
1054         if (ret) {
1055                 pr_info("Your compiler is too old; turning off.\n");
1056                 return -EINVAL;
1057         }
1058
1059         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1060         if (!klp_root_kobj)
1061                 return -ENOMEM;
1062
1063         return 0;
1064 }
1065
1066 module_init(klp_init);