kernel/livepatch/core.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * core.c - Kernel Live Patching Core
   4  *
   5  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   6  * Copyright (C) 2014 SUSE
   7  */
   8
   9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mutex.h>
  14 #include <linux/slab.h>
  15 #include <linux/list.h>
  16 #include <linux/kallsyms.h>
  17 #include <linux/livepatch.h>
  18 #include <linux/elf.h>
  19 #include <linux/moduleloader.h>
  20 #include <linux/completion.h>
  21 #include <linux/memory.h>
  22 #include <linux/rcupdate.h>
  23 #include <asm/cacheflush.h>
  24 #include "core.h"
  25 #include "patch.h"
  26 #include "state.h"
  27 #include "transition.h"
  28
  29 /*
  30  * klp_mutex is a coarse lock which serializes access to klp data.  All
  31  * accesses to klp-related variables and structures must have mutex protection,
  32  * except within the following functions which carefully avoid the need for it:
  33  *
  34  * - klp_ftrace_handler()
  35  * - klp_update_patch_state()
  36  */
  37 DEFINE_MUTEX(klp_mutex);
  38
  39 /*
  40  * Actively used patches: enabled or in transition. Note that replaced
  41  * or disabled patches are not listed even though the related kernel
  42  * module still can be loaded.
  43  */
  44 LIST_HEAD(klp_patches);
  45
  46 static struct kobject *klp_root_kobj;
  47
  48 static bool klp_is_module(struct klp_object *obj)
  49 {
  50         return obj->name;
  51 }
  52
  53 /* sets obj->mod if object is not vmlinux and module is found */
  54 static void klp_find_object_module(struct klp_object *obj)
  55 {
  56         struct module *mod;
  57
  58         if (!klp_is_module(obj))
  59                 return;
  60
  61         rcu_read_lock_sched();
  62         /*
  63          * We do not want to block removal of patched modules and therefore
  64          * we do not take a reference here. The patches are removed by
  65          * klp_module_going() instead.
  66          */
  67         mod = find_module(obj->name);
  68         /*
  69          * Do not mess work of klp_module_coming() and klp_module_going().
  70          * Note that the patch might still be needed before klp_module_going()
  71          * is called. Module functions can be called even in the GOING state
  72          * until mod->exit() finishes. This is especially important for
  73          * patches that modify semantic of the functions.
  74          */
  75         if (mod && mod->klp_alive)
  76                 obj->mod = mod;
  77
  78         rcu_read_unlock_sched();
  79 }
  80
  81 static bool klp_initialized(void)
  82 {
  83         return !!klp_root_kobj;
  84 }
  85
  86 static struct klp_func *klp_find_func(struct klp_object *obj,
  87                                       struct klp_func *old_func)
  88 {
  89         struct klp_func *func;
  90
  91         klp_for_each_func(obj, func) {
  92                 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
  93                     (old_func->old_sympos == func->old_sympos)) {
  94                         return func;
  95                 }
  96         }
  97
  98         return NULL;
  99 }
 100
 101 static struct klp_object *klp_find_object(struct klp_patch *patch,
 102                                           struct klp_object *old_obj)
 103 {
 104         struct klp_object *obj;
 105
 106         klp_for_each_object(patch, obj) {
 107                 if (klp_is_module(old_obj)) {
 108                         if (klp_is_module(obj) &&
 109                             strcmp(old_obj->name, obj->name) == 0) {
 110                                 return obj;
 111                         }
 112                 } else if (!klp_is_module(obj)) {
 113                         return obj;
 114                 }
 115         }
 116
 117         return NULL;
 118 }
 119
 120 struct klp_find_arg {
 121         const char *objname;
 122         const char *name;
 123         unsigned long addr;
 124         unsigned long count;
 125         unsigned long pos;
 126 };
 127
 128 static int klp_find_callback(void *data, const char *name,
 129                              struct module *mod, unsigned long addr)
 130 {
 131         struct klp_find_arg *args = data;
 132
 133         if ((mod && !args->objname) || (!mod && args->objname))
 134                 return 0;
 135
 136         if (strcmp(args->name, name))
 137                 return 0;
 138
 139         if (args->objname && strcmp(args->objname, mod->name))
 140                 return 0;
 141
 142         args->addr = addr;
 143         args->count++;
 144
 145         /*
 146          * Finish the search when the symbol is found for the desired position
 147          * or the position is not defined for a non-unique symbol.
 148          */
 149         if ((args->pos && (args->count == args->pos)) ||
 150             (!args->pos && (args->count > 1)))
 151                 return 1;
 152
 153         return 0;
 154 }
 155
 156 static int klp_find_object_symbol(const char *objname, const char *name,
 157                                   unsigned long sympos, unsigned long *addr)
 158 {
 159         struct klp_find_arg args = {
 160                 .objname = objname,
 161                 .name = name,
 162                 .addr = 0,
 163                 .count = 0,
 164                 .pos = sympos,
 165         };
 166
 167         if (objname)
 168                 module_kallsyms_on_each_symbol(klp_find_callback, &args);
 169         else
 170                 kallsyms_on_each_symbol(klp_find_callback, &args);
 171
 172         /*
 173          * Ensure an address was found. If sympos is 0, ensure symbol is unique;
 174          * otherwise ensure the symbol position count matches sympos.
 175          */
 176         if (args.addr == 0)
 177                 pr_err("symbol '%s' not found in symbol table\n", name);
 178         else if (args.count > 1 && sympos == 0) {
 179                 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
 180                        name, objname);
 181         } else if (sympos != args.count && sympos > 0) {
 182                 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
 183                        sympos, name, objname ? objname : "vmlinux");
 184         } else {
 185                 *addr = args.addr;
 186                 return 0;
 187         }
 188
 189         *addr = 0;
 190         return -EINVAL;
 191 }
 192
 193 static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
 194                                unsigned int symndx, Elf_Shdr *relasec,
 195                                const char *sec_objname)
 196 {
 197         int i, cnt, ret;
 198         char sym_objname[MODULE_NAME_LEN];
 199         char sym_name[KSYM_NAME_LEN];
 200         Elf_Rela *relas;
 201         Elf_Sym *sym;
 202         unsigned long sympos, addr;
 203         bool sym_vmlinux;
 204         bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
 205
 206         /*
 207          * Since the field widths for sym_objname and sym_name in the sscanf()
 208          * call are hard-coded and correspond to MODULE_NAME_LEN and
 209          * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
 210          * and KSYM_NAME_LEN have the values we expect them to have.
 211          *
 212          * Because the value of MODULE_NAME_LEN can differ among architectures,
 213          * we use the smallest/strictest upper bound possible (56, based on
 214          * the current definition of MODULE_NAME_LEN) to prevent overflows.
 215          */
 216         BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
 217
 218         relas = (Elf_Rela *) relasec->sh_addr;
 219         /* For each rela in this klp relocation section */
 220         for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
 221                 sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
 222                 if (sym->st_shndx != SHN_LIVEPATCH) {
 223                         pr_err("symbol %s is not marked as a livepatch symbol\n",
 224                                strtab + sym->st_name);
 225                         return -EINVAL;
 226                 }
 227
 228                 /* Format: .klp.sym.sym_objname.sym_name,sympos */
 229                 cnt = sscanf(strtab + sym->st_name,
 230                              ".klp.sym.%55[^.].%511[^,],%lu",
 231                              sym_objname, sym_name, &sympos);
 232                 if (cnt != 3) {
 233                         pr_err("symbol %s has an incorrectly formatted name\n",
 234                                strtab + sym->st_name);
 235                         return -EINVAL;
 236                 }
 237
 238                 sym_vmlinux = !strcmp(sym_objname, "vmlinux");
 239
 240                 /*
 241                  * Prevent module-specific KLP rela sections from referencing
 242                  * vmlinux symbols.  This helps prevent ordering issues with
 243                  * module special section initializations.  Presumably such
 244                  * symbols are exported and normal relas can be used instead.
 245                  */
 246                 if (!sec_vmlinux && sym_vmlinux) {
 247                         pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section",
 248                                sym_name);
 249                         return -EINVAL;
 250                 }
 251
 252                 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
 253                 ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
 254                                              sym_name, sympos, &addr);
 255                 if (ret)
 256                         return ret;
 257
 258                 sym->st_value = addr;
 259         }
 260
 261         return 0;
 262 }
 263
 264 /*
 265  * At a high-level, there are two types of klp relocation sections: those which
 266  * reference symbols which live in vmlinux; and those which reference symbols
 267  * which live in other modules.  This function is called for both types:
 268  *
 269  * 1) When a klp module itself loads, the module code calls this function to
 270  *    write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
 271  *    These relocations are written to the klp module text to allow the patched
 272  *    code/data to reference unexported vmlinux symbols.  They're written as
 273  *    early as possible to ensure that other module init code (.e.g.,
 274  *    jump_label_apply_nops) can access any unexported vmlinux symbols which
 275  *    might be referenced by the klp module's special sections.
 276  *
 277  * 2) When a to-be-patched module loads -- or is already loaded when a
 278  *    corresponding klp module loads -- klp code calls this function to write
 279  *    module-specific klp relocations (.klp.rela.{module}.* sections).  These
 280  *    are written to the klp module text to allow the patched code/data to
 281  *    reference symbols which live in the to-be-patched module or one of its
 282  *    module dependencies.  Exported symbols are supported, in addition to
 283  *    unexported symbols, in order to enable late module patching, which allows
 284  *    the to-be-patched module to be loaded and patched sometime *after* the
 285  *    klp module is loaded.
 286  */
 287 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
 288                              const char *shstrtab, const char *strtab,
 289                              unsigned int symndx, unsigned int secndx,
 290                              const char *objname)
 291 {
 292         int cnt, ret;
 293         char sec_objname[MODULE_NAME_LEN];
 294         Elf_Shdr *sec = sechdrs + secndx;
 295
 296         /*
 297          * Format: .klp.rela.sec_objname.section_name
 298          * See comment in klp_resolve_symbols() for an explanation
 299          * of the selected field width value.
 300          */
 301         cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
 302                      sec_objname);
 303         if (cnt != 1) {
 304                 pr_err("section %s has an incorrectly formatted name\n",
 305                        shstrtab + sec->sh_name);
 306                 return -EINVAL;
 307         }
 308
 309         if (strcmp(objname ? objname : "vmlinux", sec_objname))
 310                 return 0;
 311
 312         ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
 313         if (ret)
 314                 return ret;
 315
 316         return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
 317 }
 318
 319 /*
 320  * Sysfs Interface
 321  *
 322  * /sys/kernel/livepatch
 323  * /sys/kernel/livepatch/<patch>
 324  * /sys/kernel/livepatch/<patch>/enabled
 325  * /sys/kernel/livepatch/<patch>/transition
 326  * /sys/kernel/livepatch/<patch>/force
 327  * /sys/kernel/livepatch/<patch>/<object>
 328  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
 329  */
 330 static int __klp_disable_patch(struct klp_patch *patch);
 331
 332 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
 333                              const char *buf, size_t count)
 334 {
 335         struct klp_patch *patch;
 336         int ret;
 337         bool enabled;
 338
 339         ret = kstrtobool(buf, &enabled);
 340         if (ret)
 341                 return ret;
 342
 343         patch = container_of(kobj, struct klp_patch, kobj);
 344
 345         mutex_lock(&klp_mutex);
 346
 347         if (patch->enabled == enabled) {
 348                 /* already in requested state */
 349                 ret = -EINVAL;
 350                 goto out;
 351         }
 352
 353         /*
 354          * Allow to reverse a pending transition in both ways. It might be
 355          * necessary to complete the transition without forcing and breaking
 356          * the system integrity.
 357          *
 358          * Do not allow to re-enable a disabled patch.
 359          */
 360         if (patch == klp_transition_patch)
 361                 klp_reverse_transition();
 362         else if (!enabled)
 363                 ret = __klp_disable_patch(patch);
 364         else
 365                 ret = -EINVAL;
 366
 367 out:
 368         mutex_unlock(&klp_mutex);
 369
 370         if (ret)
 371                 return ret;
 372         return count;
 373 }
 374
 375 static ssize_t enabled_show(struct kobject *kobj,
 376                             struct kobj_attribute *attr, char *buf)
 377 {
 378         struct klp_patch *patch;
 379
 380         patch = container_of(kobj, struct klp_patch, kobj);
 381         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
 382 }
 383
 384 static ssize_t transition_show(struct kobject *kobj,
 385                                struct kobj_attribute *attr, char *buf)
 386 {
 387         struct klp_patch *patch;
 388
 389         patch = container_of(kobj, struct klp_patch, kobj);
 390         return snprintf(buf, PAGE_SIZE-1, "%d\n",
 391                         patch == klp_transition_patch);
 392 }
 393
 394 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
 395                            const char *buf, size_t count)
 396 {
 397         struct klp_patch *patch;
 398         int ret;
 399         bool val;
 400
 401         ret = kstrtobool(buf, &val);
 402         if (ret)
 403                 return ret;
 404
 405         if (!val)
 406                 return count;
 407
 408         mutex_lock(&klp_mutex);
 409
 410         patch = container_of(kobj, struct klp_patch, kobj);
 411         if (patch != klp_transition_patch) {
 412                 mutex_unlock(&klp_mutex);
 413                 return -EINVAL;
 414         }
 415
 416         klp_force_transition();
 417
 418         mutex_unlock(&klp_mutex);
 419
 420         return count;
 421 }
 422
 423 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 424 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
 425 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
 426 static struct attribute *klp_patch_attrs[] = {
 427         &enabled_kobj_attr.attr,
 428         &transition_kobj_attr.attr,
 429         &force_kobj_attr.attr,
 430         NULL
 431 };
 432 ATTRIBUTE_GROUPS(klp_patch);
 433
 434 static void klp_free_object_dynamic(struct klp_object *obj)
 435 {
 436         kfree(obj->name);
 437         kfree(obj);
 438 }
 439
 440 static void klp_init_func_early(struct klp_object *obj,
 441                                 struct klp_func *func);
 442 static void klp_init_object_early(struct klp_patch *patch,
 443                                   struct klp_object *obj);
 444
 445 static struct klp_object *klp_alloc_object_dynamic(const char *name,
 446                                                    struct klp_patch *patch)
 447 {
 448         struct klp_object *obj;
 449
 450         obj = kzalloc(sizeof(*obj), GFP_KERNEL);
 451         if (!obj)
 452                 return NULL;
 453
 454         if (name) {
 455                 obj->name = kstrdup(name, GFP_KERNEL);
 456                 if (!obj->name) {
 457                         kfree(obj);
 458                         return NULL;
 459                 }
 460         }
 461
 462         klp_init_object_early(patch, obj);
 463         obj->dynamic = true;
 464
 465         return obj;
 466 }
 467
 468 static void klp_free_func_nop(struct klp_func *func)
 469 {
 470         kfree(func->old_name);
 471         kfree(func);
 472 }
 473
 474 static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
 475                                            struct klp_object *obj)
 476 {
 477         struct klp_func *func;
 478
 479         func = kzalloc(sizeof(*func), GFP_KERNEL);
 480         if (!func)
 481                 return NULL;
 482
 483         if (old_func->old_name) {
 484                 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
 485                 if (!func->old_name) {
 486                         kfree(func);
 487                         return NULL;
 488                 }
 489         }
 490
 491         klp_init_func_early(obj, func);
 492         /*
 493          * func->new_func is same as func->old_func. These addresses are
 494          * set when the object is loaded, see klp_init_object_loaded().
 495          */
 496         func->old_sympos = old_func->old_sympos;
 497         func->nop = true;
 498
 499         return func;
 500 }
 501
 502 static int klp_add_object_nops(struct klp_patch *patch,
 503                                struct klp_object *old_obj)
 504 {
 505         struct klp_object *obj;
 506         struct klp_func *func, *old_func;
 507
 508         obj = klp_find_object(patch, old_obj);
 509
 510         if (!obj) {
 511                 obj = klp_alloc_object_dynamic(old_obj->name, patch);
 512                 if (!obj)
 513                         return -ENOMEM;
 514         }
 515
 516         klp_for_each_func(old_obj, old_func) {
 517                 func = klp_find_func(obj, old_func);
 518                 if (func)
 519                         continue;
 520
 521                 func = klp_alloc_func_nop(old_func, obj);
 522                 if (!func)
 523                         return -ENOMEM;
 524         }
 525
 526         return 0;
 527 }
 528
 529 /*
 530  * Add 'nop' functions which simply return to the caller to run
 531  * the original function. The 'nop' functions are added to a
 532  * patch to facilitate a 'replace' mode.
 533  */
 534 static int klp_add_nops(struct klp_patch *patch)
 535 {
 536         struct klp_patch *old_patch;
 537         struct klp_object *old_obj;
 538
 539         klp_for_each_patch(old_patch) {
 540                 klp_for_each_object(old_patch, old_obj) {
 541                         int err;
 542
 543                         err = klp_add_object_nops(patch, old_obj);
 544                         if (err)
 545                                 return err;
 546                 }
 547         }
 548
 549         return 0;
 550 }
 551
 552 static void klp_kobj_release_patch(struct kobject *kobj)
 553 {
 554         struct klp_patch *patch;
 555
 556         patch = container_of(kobj, struct klp_patch, kobj);
 557         complete(&patch->finish);
 558 }
 559
 560 static struct kobj_type klp_ktype_patch = {
 561         .release = klp_kobj_release_patch,
 562         .sysfs_ops = &kobj_sysfs_ops,
 563         .default_groups = klp_patch_groups,
 564 };
 565
 566 static void klp_kobj_release_object(struct kobject *kobj)
 567 {
 568         struct klp_object *obj;
 569
 570         obj = container_of(kobj, struct klp_object, kobj);
 571
 572         if (obj->dynamic)
 573                 klp_free_object_dynamic(obj);
 574 }
 575
 576 static struct kobj_type klp_ktype_object = {
 577         .release = klp_kobj_release_object,
 578         .sysfs_ops = &kobj_sysfs_ops,
 579 };
 580
 581 static void klp_kobj_release_func(struct kobject *kobj)
 582 {
 583         struct klp_func *func;
 584
 585         func = container_of(kobj, struct klp_func, kobj);
 586
 587         if (func->nop)
 588                 klp_free_func_nop(func);
 589 }
 590
 591 static struct kobj_type klp_ktype_func = {
 592         .release = klp_kobj_release_func,
 593         .sysfs_ops = &kobj_sysfs_ops,
 594 };
 595
 596 static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
 597 {
 598         struct klp_func *func, *tmp_func;
 599
 600         klp_for_each_func_safe(obj, func, tmp_func) {
 601                 if (nops_only && !func->nop)
 602                         continue;
 603
 604                 list_del(&func->node);
 605                 kobject_put(&func->kobj);
 606         }
 607 }
 608
 609 /* Clean up when a patched object is unloaded */
 610 static void klp_free_object_loaded(struct klp_object *obj)
 611 {
 612         struct klp_func *func;
 613
 614         obj->mod = NULL;
 615
 616         klp_for_each_func(obj, func) {
 617                 func->old_func = NULL;
 618
 619                 if (func->nop)
 620                         func->new_func = NULL;
 621         }
 622 }
 623
 624 static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
 625 {
 626         struct klp_object *obj, *tmp_obj;
 627
 628         klp_for_each_object_safe(patch, obj, tmp_obj) {
 629                 __klp_free_funcs(obj, nops_only);
 630
 631                 if (nops_only && !obj->dynamic)
 632                         continue;
 633
 634                 list_del(&obj->node);
 635                 kobject_put(&obj->kobj);
 636         }
 637 }
 638
 639 static void klp_free_objects(struct klp_patch *patch)
 640 {
 641         __klp_free_objects(patch, false);
 642 }
 643
 644 static void klp_free_objects_dynamic(struct klp_patch *patch)
 645 {
 646         __klp_free_objects(patch, true);
 647 }
 648
 649 /*
 650  * This function implements the free operations that can be called safely
 651  * under klp_mutex.
 652  *
 653  * The operation must be completed by calling klp_free_patch_finish()
 654  * outside klp_mutex.
 655  */
 656 static void klp_free_patch_start(struct klp_patch *patch)
 657 {
 658         if (!list_empty(&patch->list))
 659                 list_del(&patch->list);
 660
 661         klp_free_objects(patch);
 662 }
 663
 664 /*
 665  * This function implements the free part that must be called outside
 666  * klp_mutex.
 667  *
 668  * It must be called after klp_free_patch_start(). And it has to be
 669  * the last function accessing the livepatch structures when the patch
 670  * gets disabled.
 671  */
 672 static void klp_free_patch_finish(struct klp_patch *patch)
 673 {
 674         /*
 675          * Avoid deadlock with enabled_store() sysfs callback by
 676          * calling this outside klp_mutex. It is safe because
 677          * this is called when the patch gets disabled and it
 678          * cannot get enabled again.
 679          */
 680         kobject_put(&patch->kobj);
 681         wait_for_completion(&patch->finish);
 682
 683         /* Put the module after the last access to struct klp_patch. */
 684         if (!patch->forced)
 685                 module_put(patch->mod);
 686 }
 687
 688 /*
 689  * The livepatch might be freed from sysfs interface created by the patch.
 690  * This work allows to wait until the interface is destroyed in a separate
 691  * context.
 692  */
 693 static void klp_free_patch_work_fn(struct work_struct *work)
 694 {
 695         struct klp_patch *patch =
 696                 container_of(work, struct klp_patch, free_work);
 697
 698         klp_free_patch_finish(patch);
 699 }
 700
 701 void klp_free_patch_async(struct klp_patch *patch)
 702 {
 703         klp_free_patch_start(patch);
 704         schedule_work(&patch->free_work);
 705 }
 706
 707 void klp_free_replaced_patches_async(struct klp_patch *new_patch)
 708 {
 709         struct klp_patch *old_patch, *tmp_patch;
 710
 711         klp_for_each_patch_safe(old_patch, tmp_patch) {
 712                 if (old_patch == new_patch)
 713                         return;
 714                 klp_free_patch_async(old_patch);
 715         }
 716 }
 717
 718 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 719 {
 720         if (!func->old_name)
 721                 return -EINVAL;
 722
 723         /*
 724          * NOPs get the address later. The patched module must be loaded,
 725          * see klp_init_object_loaded().
 726          */
 727         if (!func->new_func && !func->nop)
 728                 return -EINVAL;
 729
 730         if (strlen(func->old_name) >= KSYM_NAME_LEN)
 731                 return -EINVAL;
 732
 733         INIT_LIST_HEAD(&func->stack_node);
 734         func->patched = false;
 735         func->transition = false;
 736
 737         /* The format for the sysfs directory is <function,sympos> where sympos
 738          * is the nth occurrence of this symbol in kallsyms for the patched
 739          * object. If the user selects 0 for old_sympos, then 1 will be used
 740          * since a unique symbol will be the first occurrence.
 741          */
 742         return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
 743                            func->old_name,
 744                            func->old_sympos ? func->old_sympos : 1);
 745 }
 746
 747 static int klp_apply_object_relocs(struct klp_patch *patch,
 748                                    struct klp_object *obj)
 749 {
 750         int i, ret;
 751         struct klp_modinfo *info = patch->mod->klp_info;
 752
 753         for (i = 1; i < info->hdr.e_shnum; i++) {
 754                 Elf_Shdr *sec = info->sechdrs + i;
 755
 756                 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
 757                         continue;
 758
 759                 ret = klp_apply_section_relocs(patch->mod, info->sechdrs,
 760                                                info->secstrings,
 761                                                patch->mod->core_kallsyms.strtab,
 762                                                info->symndx, i, obj->name);
 763                 if (ret)
 764                         return ret;
 765         }
 766
 767         return 0;
 768 }
 769
 770 /* parts of the initialization that is done only when the object is loaded */
 771 static int klp_init_object_loaded(struct klp_patch *patch,
 772                                   struct klp_object *obj)
 773 {
 774         struct klp_func *func;
 775         int ret;
 776
 777         if (klp_is_module(obj)) {
 778                 /*
 779                  * Only write module-specific relocations here
 780                  * (.klp.rela.{module}.*).  vmlinux-specific relocations were
 781                  * written earlier during the initialization of the klp module
 782                  * itself.
 783                  */
 784                 ret = klp_apply_object_relocs(patch, obj);
 785                 if (ret)
 786                         return ret;
 787         }
 788
 789         klp_for_each_func(obj, func) {
 790                 ret = klp_find_object_symbol(obj->name, func->old_name,
 791                                              func->old_sympos,
 792                                              (unsigned long *)&func->old_func);
 793                 if (ret)
 794                         return ret;
 795
 796                 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
 797                                                   &func->old_size, NULL);
 798                 if (!ret) {
 799                         pr_err("kallsyms size lookup failed for '%s'\n",
 800                                func->old_name);
 801                         return -ENOENT;
 802                 }
 803
 804                 if (func->nop)
 805                         func->new_func = func->old_func;
 806
 807                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
 808                                                   &func->new_size, NULL);
 809                 if (!ret) {
 810                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
 811                                func->old_name);
 812                         return -ENOENT;
 813                 }
 814         }
 815
 816         return 0;
 817 }
 818
 819 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 820 {
 821         struct klp_func *func;
 822         int ret;
 823         const char *name;
 824
 825         if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
 826                 return -EINVAL;
 827
 828         obj->patched = false;
 829         obj->mod = NULL;
 830
 831         klp_find_object_module(obj);
 832
 833         name = klp_is_module(obj) ? obj->name : "vmlinux";
 834         ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
 835         if (ret)
 836                 return ret;
 837
 838         klp_for_each_func(obj, func) {
 839                 ret = klp_init_func(obj, func);
 840                 if (ret)
 841                         return ret;
 842         }
 843
 844         if (klp_is_object_loaded(obj))
 845                 ret = klp_init_object_loaded(patch, obj);
 846
 847         return ret;
 848 }
 849
 850 static void klp_init_func_early(struct klp_object *obj,
 851                                 struct klp_func *func)
 852 {
 853         kobject_init(&func->kobj, &klp_ktype_func);
 854         list_add_tail(&func->node, &obj->func_list);
 855 }
 856
 857 static void klp_init_object_early(struct klp_patch *patch,
 858                                   struct klp_object *obj)
 859 {
 860         INIT_LIST_HEAD(&obj->func_list);
 861         kobject_init(&obj->kobj, &klp_ktype_object);
 862         list_add_tail(&obj->node, &patch->obj_list);
 863 }
 864
 865 static void klp_init_patch_early(struct klp_patch *patch)
 866 {
 867         struct klp_object *obj;
 868         struct klp_func *func;
 869
 870         INIT_LIST_HEAD(&patch->list);
 871         INIT_LIST_HEAD(&patch->obj_list);
 872         kobject_init(&patch->kobj, &klp_ktype_patch);
 873         patch->enabled = false;
 874         patch->forced = false;
 875         INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
 876         init_completion(&patch->finish);
 877
 878         klp_for_each_object_static(patch, obj) {
 879                 klp_init_object_early(patch, obj);
 880
 881                 klp_for_each_func_static(obj, func) {
 882                         klp_init_func_early(obj, func);
 883                 }
 884         }
 885 }
 886
 887 static int klp_init_patch(struct klp_patch *patch)
 888 {
 889         struct klp_object *obj;
 890         int ret;
 891
 892         ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
 893         if (ret)
 894                 return ret;
 895
 896         if (patch->replace) {
 897                 ret = klp_add_nops(patch);
 898                 if (ret)
 899                         return ret;
 900         }
 901
 902         klp_for_each_object(patch, obj) {
 903                 ret = klp_init_object(patch, obj);
 904                 if (ret)
 905                         return ret;
 906         }
 907
 908         list_add_tail(&patch->list, &klp_patches);
 909
 910         return 0;
 911 }
 912
 913 static int __klp_disable_patch(struct klp_patch *patch)
 914 {
 915         struct klp_object *obj;
 916
 917         if (WARN_ON(!patch->enabled))
 918                 return -EINVAL;
 919
 920         if (klp_transition_patch)
 921                 return -EBUSY;
 922
 923         klp_init_transition(patch, KLP_UNPATCHED);
 924
 925         klp_for_each_object(patch, obj)
 926                 if (obj->patched)
 927                         klp_pre_unpatch_callback(obj);
 928
 929         /*
 930          * Enforce the order of the func->transition writes in
 931          * klp_init_transition() and the TIF_PATCH_PENDING writes in
 932          * klp_start_transition().  In the rare case where klp_ftrace_handler()
 933          * is called shortly after klp_update_patch_state() switches the task,
 934          * this ensures the handler sees that func->transition is set.
 935          */
 936         smp_wmb();
 937
 938         klp_start_transition();
 939         patch->enabled = false;
 940         klp_try_complete_transition();
 941
 942         return 0;
 943 }
 944
 945 static int __klp_enable_patch(struct klp_patch *patch)
 946 {
 947         struct klp_object *obj;
 948         int ret;
 949
 950         if (klp_transition_patch)
 951                 return -EBUSY;
 952
 953         if (WARN_ON(patch->enabled))
 954                 return -EINVAL;
 955
 956         pr_notice("enabling patch '%s'\n", patch->mod->name);
 957
 958         klp_init_transition(patch, KLP_PATCHED);
 959
 960         /*
 961          * Enforce the order of the func->transition writes in
 962          * klp_init_transition() and the ops->func_stack writes in
 963          * klp_patch_object(), so that klp_ftrace_handler() will see the
 964          * func->transition updates before the handler is registered and the
 965          * new funcs become visible to the handler.
 966          */
 967         smp_wmb();
 968
 969         klp_for_each_object(patch, obj) {
 970                 if (!klp_is_object_loaded(obj))
 971                         continue;
 972
 973                 ret = klp_pre_patch_callback(obj);
 974                 if (ret) {
 975                         pr_warn("pre-patch callback failed for object '%s'\n",
 976                                 klp_is_module(obj) ? obj->name : "vmlinux");
 977                         goto err;
 978                 }
 979
 980                 ret = klp_patch_object(obj);
 981                 if (ret) {
 982                         pr_warn("failed to patch object '%s'\n",
 983                                 klp_is_module(obj) ? obj->name : "vmlinux");
 984                         goto err;
 985                 }
 986         }
 987
 988         klp_start_transition();
 989         patch->enabled = true;
 990         klp_try_complete_transition();
 991
 992         return 0;
 993 err:
 994         pr_warn("failed to enable patch '%s'\n", patch->mod->name);
 995
 996         klp_cancel_transition();
 997         return ret;
 998 }
 999
1000 /**
1001  * klp_enable_patch() - enable the livepatch
1002  * @patch:      patch to be enabled
1003  *
1004  * Initializes the data structure associated with the patch, creates the sysfs
1005  * interface, performs the needed symbol lookups and code relocations,
1006  * registers the patched functions with ftrace.
1007  *
1008  * This function is supposed to be called from the livepatch module_init()
1009  * callback.
1010  *
1011  * Return: 0 on success, otherwise error
1012  */
1013 int klp_enable_patch(struct klp_patch *patch)
1014 {
1015         int ret;
1016         struct klp_object *obj;
1017
1018         if (!patch || !patch->mod || !patch->objs)
1019                 return -EINVAL;
1020
1021         klp_for_each_object_static(patch, obj) {
1022                 if (!obj->funcs)
1023                         return -EINVAL;
1024         }
1025
1026
1027         if (!is_livepatch_module(patch->mod)) {
1028                 pr_err("module %s is not marked as a livepatch module\n",
1029                        patch->mod->name);
1030                 return -EINVAL;
1031         }
1032
1033         if (!klp_initialized())
1034                 return -ENODEV;
1035
1036         if (!klp_have_reliable_stack()) {
1037                 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1038                 pr_warn("The livepatch transition may never complete.\n");
1039         }
1040
1041         mutex_lock(&klp_mutex);
1042
1043         if (!klp_is_patch_compatible(patch)) {
1044                 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1045                         patch->mod->name);
1046                 mutex_unlock(&klp_mutex);
1047                 return -EINVAL;
1048         }
1049
1050         if (!try_module_get(patch->mod)) {
1051                 mutex_unlock(&klp_mutex);
1052                 return -ENODEV;
1053         }
1054
1055         klp_init_patch_early(patch);
1056
1057         ret = klp_init_patch(patch);
1058         if (ret)
1059                 goto err;
1060
1061         ret = __klp_enable_patch(patch);
1062         if (ret)
1063                 goto err;
1064
1065         mutex_unlock(&klp_mutex);
1066
1067         return 0;
1068
1069 err:
1070         klp_free_patch_start(patch);
1071
1072         mutex_unlock(&klp_mutex);
1073
1074         klp_free_patch_finish(patch);
1075
1076         return ret;
1077 }
1078 EXPORT_SYMBOL_GPL(klp_enable_patch);
1079
1080 /*
1081  * This function unpatches objects from the replaced livepatches.
1082  *
1083  * We could be pretty aggressive here. It is called in the situation where
1084  * these structures are no longer accessed from the ftrace handler.
1085  * All functions are redirected by the klp_transition_patch. They
1086  * use either a new code or they are in the original code because
1087  * of the special nop function patches.
1088  *
1089  * The only exception is when the transition was forced. In this case,
1090  * klp_ftrace_handler() might still see the replaced patch on the stack.
1091  * Fortunately, it is carefully designed to work with removed functions
1092  * thanks to RCU. We only have to keep the patches on the system. Also
1093  * this is handled transparently by patch->module_put.
1094  */
1095 void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1096 {
1097         struct klp_patch *old_patch;
1098
1099         klp_for_each_patch(old_patch) {
1100                 if (old_patch == new_patch)
1101                         return;
1102
1103                 old_patch->enabled = false;
1104                 klp_unpatch_objects(old_patch);
1105         }
1106 }
1107
1108 /*
1109  * This function removes the dynamically allocated 'nop' functions.
1110  *
1111  * We could be pretty aggressive. NOPs do not change the existing
1112  * behavior except for adding unnecessary delay by the ftrace handler.
1113  *
1114  * It is safe even when the transition was forced. The ftrace handler
1115  * will see a valid ops->func_stack entry thanks to RCU.
1116  *
1117  * We could even free the NOPs structures. They must be the last entry
1118  * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1119  * It does the same as klp_synchronize_transition() to make sure that
1120  * nobody is inside the ftrace handler once the operation finishes.
1121  *
1122  * IMPORTANT: It must be called right after removing the replaced patches!
1123  */
1124 void klp_discard_nops(struct klp_patch *new_patch)
1125 {
1126         klp_unpatch_objects_dynamic(klp_transition_patch);
1127         klp_free_objects_dynamic(klp_transition_patch);
1128 }
1129
1130 /*
1131  * Remove parts of patches that touch a given kernel module. The list of
1132  * patches processed might be limited. When limit is NULL, all patches
1133  * will be handled.
1134  */
1135 static void klp_cleanup_module_patches_limited(struct module *mod,
1136                                                struct klp_patch *limit)
1137 {
1138         struct klp_patch *patch;
1139         struct klp_object *obj;
1140
1141         klp_for_each_patch(patch) {
1142                 if (patch == limit)
1143                         break;
1144
1145                 klp_for_each_object(patch, obj) {
1146                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1147                                 continue;
1148
1149                         if (patch != klp_transition_patch)
1150                                 klp_pre_unpatch_callback(obj);
1151
1152                         pr_notice("reverting patch '%s' on unloading module '%s'\n",
1153                                   patch->mod->name, obj->mod->name);
1154                         klp_unpatch_object(obj);
1155
1156                         klp_post_unpatch_callback(obj);
1157
1158                         klp_free_object_loaded(obj);
1159                         break;
1160                 }
1161         }
1162 }
1163
1164 int klp_module_coming(struct module *mod)
1165 {
1166         int ret;
1167         struct klp_patch *patch;
1168         struct klp_object *obj;
1169
1170         if (WARN_ON(mod->state != MODULE_STATE_COMING))
1171                 return -EINVAL;
1172
1173         if (!strcmp(mod->name, "vmlinux")) {
1174                 pr_err("vmlinux.ko: invalid module name");
1175                 return -EINVAL;
1176         }
1177
1178         mutex_lock(&klp_mutex);
1179         /*
1180          * Each module has to know that klp_module_coming()
1181          * has been called. We never know what module will
1182          * get patched by a new patch.
1183          */
1184         mod->klp_alive = true;
1185
1186         klp_for_each_patch(patch) {
1187                 klp_for_each_object(patch, obj) {
1188                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1189                                 continue;
1190
1191                         obj->mod = mod;
1192
1193                         ret = klp_init_object_loaded(patch, obj);
1194                         if (ret) {
1195                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1196                                         patch->mod->name, obj->mod->name, ret);
1197                                 goto err;
1198                         }
1199
1200                         pr_notice("applying patch '%s' to loading module '%s'\n",
1201                                   patch->mod->name, obj->mod->name);
1202
1203                         ret = klp_pre_patch_callback(obj);
1204                         if (ret) {
1205                                 pr_warn("pre-patch callback failed for object '%s'\n",
1206                                         obj->name);
1207                                 goto err;
1208                         }
1209
1210                         ret = klp_patch_object(obj);
1211                         if (ret) {
1212                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1213                                         patch->mod->name, obj->mod->name, ret);
1214
1215                                 klp_post_unpatch_callback(obj);
1216                                 goto err;
1217                         }
1218
1219                         if (patch != klp_transition_patch)
1220                                 klp_post_patch_callback(obj);
1221
1222                         break;
1223                 }
1224         }
1225
1226         mutex_unlock(&klp_mutex);
1227
1228         return 0;
1229
1230 err:
1231         /*
1232          * If a patch is unsuccessfully applied, return
1233          * error to the module loader.
1234          */
1235         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1236                 patch->mod->name, obj->mod->name, obj->mod->name);
1237         mod->klp_alive = false;
1238         obj->mod = NULL;
1239         klp_cleanup_module_patches_limited(mod, patch);
1240         mutex_unlock(&klp_mutex);
1241
1242         return ret;
1243 }
1244
1245 void klp_module_going(struct module *mod)
1246 {
1247         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1248                     mod->state != MODULE_STATE_COMING))
1249                 return;
1250
1251         mutex_lock(&klp_mutex);
1252         /*
1253          * Each module has to know that klp_module_going()
1254          * has been called. We never know what module will
1255          * get patched by a new patch.
1256          */
1257         mod->klp_alive = false;
1258
1259         klp_cleanup_module_patches_limited(mod, NULL);
1260
1261         mutex_unlock(&klp_mutex);
1262 }
1263
1264 static int __init klp_init(void)
1265 {
1266         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1267         if (!klp_root_kobj)
1268                 return -ENOMEM;
1269
1270         return 0;
1271 }
1272
1273 module_init(klp_init);