Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid
[muen/linux.git] / kernel / livepatch / core.c
1 /*
2  * core.c - Kernel Live Patching Core
3  *
4  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
5  * Copyright (C) 2014 SUSE
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version 2
10  * of the License, or (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, see <http://www.gnu.org/licenses/>.
19  */
20
21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23 #include <linux/module.h>
24 #include <linux/kernel.h>
25 #include <linux/mutex.h>
26 #include <linux/slab.h>
27 #include <linux/list.h>
28 #include <linux/kallsyms.h>
29 #include <linux/livepatch.h>
30 #include <linux/elf.h>
31 #include <linux/moduleloader.h>
32 #include <linux/completion.h>
33 #include <asm/cacheflush.h>
34 #include "core.h"
35 #include "patch.h"
36 #include "transition.h"
37
38 /*
39  * klp_mutex is a coarse lock which serializes access to klp data.  All
40  * accesses to klp-related variables and structures must have mutex protection,
41  * except within the following functions which carefully avoid the need for it:
42  *
43  * - klp_ftrace_handler()
44  * - klp_update_patch_state()
45  */
46 DEFINE_MUTEX(klp_mutex);
47
48 static LIST_HEAD(klp_patches);
49
50 static struct kobject *klp_root_kobj;
51
52 static bool klp_is_module(struct klp_object *obj)
53 {
54         return obj->name;
55 }
56
57 /* sets obj->mod if object is not vmlinux and module is found */
58 static void klp_find_object_module(struct klp_object *obj)
59 {
60         struct module *mod;
61
62         if (!klp_is_module(obj))
63                 return;
64
65         mutex_lock(&module_mutex);
66         /*
67          * We do not want to block removal of patched modules and therefore
68          * we do not take a reference here. The patches are removed by
69          * klp_module_going() instead.
70          */
71         mod = find_module(obj->name);
72         /*
73          * Do not mess work of klp_module_coming() and klp_module_going().
74          * Note that the patch might still be needed before klp_module_going()
75          * is called. Module functions can be called even in the GOING state
76          * until mod->exit() finishes. This is especially important for
77          * patches that modify semantic of the functions.
78          */
79         if (mod && mod->klp_alive)
80                 obj->mod = mod;
81
82         mutex_unlock(&module_mutex);
83 }
84
85 static bool klp_is_patch_registered(struct klp_patch *patch)
86 {
87         struct klp_patch *mypatch;
88
89         list_for_each_entry(mypatch, &klp_patches, list)
90                 if (mypatch == patch)
91                         return true;
92
93         return false;
94 }
95
96 static bool klp_initialized(void)
97 {
98         return !!klp_root_kobj;
99 }
100
101 struct klp_find_arg {
102         const char *objname;
103         const char *name;
104         unsigned long addr;
105         unsigned long count;
106         unsigned long pos;
107 };
108
109 static int klp_find_callback(void *data, const char *name,
110                              struct module *mod, unsigned long addr)
111 {
112         struct klp_find_arg *args = data;
113
114         if ((mod && !args->objname) || (!mod && args->objname))
115                 return 0;
116
117         if (strcmp(args->name, name))
118                 return 0;
119
120         if (args->objname && strcmp(args->objname, mod->name))
121                 return 0;
122
123         args->addr = addr;
124         args->count++;
125
126         /*
127          * Finish the search when the symbol is found for the desired position
128          * or the position is not defined for a non-unique symbol.
129          */
130         if ((args->pos && (args->count == args->pos)) ||
131             (!args->pos && (args->count > 1)))
132                 return 1;
133
134         return 0;
135 }
136
137 static int klp_find_object_symbol(const char *objname, const char *name,
138                                   unsigned long sympos, unsigned long *addr)
139 {
140         struct klp_find_arg args = {
141                 .objname = objname,
142                 .name = name,
143                 .addr = 0,
144                 .count = 0,
145                 .pos = sympos,
146         };
147
148         mutex_lock(&module_mutex);
149         if (objname)
150                 module_kallsyms_on_each_symbol(klp_find_callback, &args);
151         else
152                 kallsyms_on_each_symbol(klp_find_callback, &args);
153         mutex_unlock(&module_mutex);
154
155         /*
156          * Ensure an address was found. If sympos is 0, ensure symbol is unique;
157          * otherwise ensure the symbol position count matches sympos.
158          */
159         if (args.addr == 0)
160                 pr_err("symbol '%s' not found in symbol table\n", name);
161         else if (args.count > 1 && sympos == 0) {
162                 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
163                        name, objname);
164         } else if (sympos != args.count && sympos > 0) {
165                 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
166                        sympos, name, objname ? objname : "vmlinux");
167         } else {
168                 *addr = args.addr;
169                 return 0;
170         }
171
172         *addr = 0;
173         return -EINVAL;
174 }
175
176 static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
177 {
178         int i, cnt, vmlinux, ret;
179         char objname[MODULE_NAME_LEN];
180         char symname[KSYM_NAME_LEN];
181         char *strtab = pmod->core_kallsyms.strtab;
182         Elf_Rela *relas;
183         Elf_Sym *sym;
184         unsigned long sympos, addr;
185
186         /*
187          * Since the field widths for objname and symname in the sscanf()
188          * call are hard-coded and correspond to MODULE_NAME_LEN and
189          * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
190          * and KSYM_NAME_LEN have the values we expect them to have.
191          *
192          * Because the value of MODULE_NAME_LEN can differ among architectures,
193          * we use the smallest/strictest upper bound possible (56, based on
194          * the current definition of MODULE_NAME_LEN) to prevent overflows.
195          */
196         BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
197
198         relas = (Elf_Rela *) relasec->sh_addr;
199         /* For each rela in this klp relocation section */
200         for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
201                 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
202                 if (sym->st_shndx != SHN_LIVEPATCH) {
203                         pr_err("symbol %s is not marked as a livepatch symbol\n",
204                                strtab + sym->st_name);
205                         return -EINVAL;
206                 }
207
208                 /* Format: .klp.sym.objname.symname,sympos */
209                 cnt = sscanf(strtab + sym->st_name,
210                              ".klp.sym.%55[^.].%127[^,],%lu",
211                              objname, symname, &sympos);
212                 if (cnt != 3) {
213                         pr_err("symbol %s has an incorrectly formatted name\n",
214                                strtab + sym->st_name);
215                         return -EINVAL;
216                 }
217
218                 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
219                 vmlinux = !strcmp(objname, "vmlinux");
220                 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
221                                              symname, sympos, &addr);
222                 if (ret)
223                         return ret;
224
225                 sym->st_value = addr;
226         }
227
228         return 0;
229 }
230
231 static int klp_write_object_relocations(struct module *pmod,
232                                         struct klp_object *obj)
233 {
234         int i, cnt, ret = 0;
235         const char *objname, *secname;
236         char sec_objname[MODULE_NAME_LEN];
237         Elf_Shdr *sec;
238
239         if (WARN_ON(!klp_is_object_loaded(obj)))
240                 return -EINVAL;
241
242         objname = klp_is_module(obj) ? obj->name : "vmlinux";
243
244         /* For each klp relocation section */
245         for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
246                 sec = pmod->klp_info->sechdrs + i;
247                 secname = pmod->klp_info->secstrings + sec->sh_name;
248                 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
249                         continue;
250
251                 /*
252                  * Format: .klp.rela.sec_objname.section_name
253                  * See comment in klp_resolve_symbols() for an explanation
254                  * of the selected field width value.
255                  */
256                 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
257                 if (cnt != 1) {
258                         pr_err("section %s has an incorrectly formatted name\n",
259                                secname);
260                         ret = -EINVAL;
261                         break;
262                 }
263
264                 if (strcmp(objname, sec_objname))
265                         continue;
266
267                 ret = klp_resolve_symbols(sec, pmod);
268                 if (ret)
269                         break;
270
271                 ret = apply_relocate_add(pmod->klp_info->sechdrs,
272                                          pmod->core_kallsyms.strtab,
273                                          pmod->klp_info->symndx, i, pmod);
274                 if (ret)
275                         break;
276         }
277
278         return ret;
279 }
280
281 static int __klp_disable_patch(struct klp_patch *patch)
282 {
283         struct klp_object *obj;
284
285         if (WARN_ON(!patch->enabled))
286                 return -EINVAL;
287
288         if (klp_transition_patch)
289                 return -EBUSY;
290
291         /* enforce stacking: only the last enabled patch can be disabled */
292         if (!list_is_last(&patch->list, &klp_patches) &&
293             list_next_entry(patch, list)->enabled)
294                 return -EBUSY;
295
296         klp_init_transition(patch, KLP_UNPATCHED);
297
298         klp_for_each_object(patch, obj)
299                 if (obj->patched)
300                         klp_pre_unpatch_callback(obj);
301
302         /*
303          * Enforce the order of the func->transition writes in
304          * klp_init_transition() and the TIF_PATCH_PENDING writes in
305          * klp_start_transition().  In the rare case where klp_ftrace_handler()
306          * is called shortly after klp_update_patch_state() switches the task,
307          * this ensures the handler sees that func->transition is set.
308          */
309         smp_wmb();
310
311         klp_start_transition();
312         klp_try_complete_transition();
313         patch->enabled = false;
314
315         return 0;
316 }
317
318 /**
319  * klp_disable_patch() - disables a registered patch
320  * @patch:      The registered, enabled patch to be disabled
321  *
322  * Unregisters the patched functions from ftrace.
323  *
324  * Return: 0 on success, otherwise error
325  */
326 int klp_disable_patch(struct klp_patch *patch)
327 {
328         int ret;
329
330         mutex_lock(&klp_mutex);
331
332         if (!klp_is_patch_registered(patch)) {
333                 ret = -EINVAL;
334                 goto err;
335         }
336
337         if (!patch->enabled) {
338                 ret = -EINVAL;
339                 goto err;
340         }
341
342         ret = __klp_disable_patch(patch);
343
344 err:
345         mutex_unlock(&klp_mutex);
346         return ret;
347 }
348 EXPORT_SYMBOL_GPL(klp_disable_patch);
349
350 static int __klp_enable_patch(struct klp_patch *patch)
351 {
352         struct klp_object *obj;
353         int ret;
354
355         if (klp_transition_patch)
356                 return -EBUSY;
357
358         if (WARN_ON(patch->enabled))
359                 return -EINVAL;
360
361         /* enforce stacking: only the first disabled patch can be enabled */
362         if (patch->list.prev != &klp_patches &&
363             !list_prev_entry(patch, list)->enabled)
364                 return -EBUSY;
365
366         /*
367          * A reference is taken on the patch module to prevent it from being
368          * unloaded.
369          *
370          * Note: For immediate (no consistency model) patches we don't allow
371          * patch modules to unload since there is no safe/sane method to
372          * determine if a thread is still running in the patched code contained
373          * in the patch module once the ftrace registration is successful.
374          */
375         if (!try_module_get(patch->mod))
376                 return -ENODEV;
377
378         pr_notice("enabling patch '%s'\n", patch->mod->name);
379
380         klp_init_transition(patch, KLP_PATCHED);
381
382         /*
383          * Enforce the order of the func->transition writes in
384          * klp_init_transition() and the ops->func_stack writes in
385          * klp_patch_object(), so that klp_ftrace_handler() will see the
386          * func->transition updates before the handler is registered and the
387          * new funcs become visible to the handler.
388          */
389         smp_wmb();
390
391         klp_for_each_object(patch, obj) {
392                 if (!klp_is_object_loaded(obj))
393                         continue;
394
395                 ret = klp_pre_patch_callback(obj);
396                 if (ret) {
397                         pr_warn("pre-patch callback failed for object '%s'\n",
398                                 klp_is_module(obj) ? obj->name : "vmlinux");
399                         goto err;
400                 }
401
402                 ret = klp_patch_object(obj);
403                 if (ret) {
404                         pr_warn("failed to patch object '%s'\n",
405                                 klp_is_module(obj) ? obj->name : "vmlinux");
406                         goto err;
407                 }
408         }
409
410         klp_start_transition();
411         klp_try_complete_transition();
412         patch->enabled = true;
413
414         return 0;
415 err:
416         pr_warn("failed to enable patch '%s'\n", patch->mod->name);
417
418         klp_cancel_transition();
419         return ret;
420 }
421
422 /**
423  * klp_enable_patch() - enables a registered patch
424  * @patch:      The registered, disabled patch to be enabled
425  *
426  * Performs the needed symbol lookups and code relocations,
427  * then registers the patched functions with ftrace.
428  *
429  * Return: 0 on success, otherwise error
430  */
431 int klp_enable_patch(struct klp_patch *patch)
432 {
433         int ret;
434
435         mutex_lock(&klp_mutex);
436
437         if (!klp_is_patch_registered(patch)) {
438                 ret = -EINVAL;
439                 goto err;
440         }
441
442         ret = __klp_enable_patch(patch);
443
444 err:
445         mutex_unlock(&klp_mutex);
446         return ret;
447 }
448 EXPORT_SYMBOL_GPL(klp_enable_patch);
449
450 /*
451  * Sysfs Interface
452  *
453  * /sys/kernel/livepatch
454  * /sys/kernel/livepatch/<patch>
455  * /sys/kernel/livepatch/<patch>/enabled
456  * /sys/kernel/livepatch/<patch>/transition
457  * /sys/kernel/livepatch/<patch>/<object>
458  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
459  */
460
461 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
462                              const char *buf, size_t count)
463 {
464         struct klp_patch *patch;
465         int ret;
466         bool enabled;
467
468         ret = kstrtobool(buf, &enabled);
469         if (ret)
470                 return ret;
471
472         patch = container_of(kobj, struct klp_patch, kobj);
473
474         mutex_lock(&klp_mutex);
475
476         if (!klp_is_patch_registered(patch)) {
477                 /*
478                  * Module with the patch could either disappear meanwhile or is
479                  * not properly initialized yet.
480                  */
481                 ret = -EINVAL;
482                 goto err;
483         }
484
485         if (patch->enabled == enabled) {
486                 /* already in requested state */
487                 ret = -EINVAL;
488                 goto err;
489         }
490
491         if (patch == klp_transition_patch) {
492                 klp_reverse_transition();
493         } else if (enabled) {
494                 ret = __klp_enable_patch(patch);
495                 if (ret)
496                         goto err;
497         } else {
498                 ret = __klp_disable_patch(patch);
499                 if (ret)
500                         goto err;
501         }
502
503         mutex_unlock(&klp_mutex);
504
505         return count;
506
507 err:
508         mutex_unlock(&klp_mutex);
509         return ret;
510 }
511
512 static ssize_t enabled_show(struct kobject *kobj,
513                             struct kobj_attribute *attr, char *buf)
514 {
515         struct klp_patch *patch;
516
517         patch = container_of(kobj, struct klp_patch, kobj);
518         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
519 }
520
521 static ssize_t transition_show(struct kobject *kobj,
522                                struct kobj_attribute *attr, char *buf)
523 {
524         struct klp_patch *patch;
525
526         patch = container_of(kobj, struct klp_patch, kobj);
527         return snprintf(buf, PAGE_SIZE-1, "%d\n",
528                         patch == klp_transition_patch);
529 }
530
531 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
532 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
533 static struct attribute *klp_patch_attrs[] = {
534         &enabled_kobj_attr.attr,
535         &transition_kobj_attr.attr,
536         NULL
537 };
538
539 static void klp_kobj_release_patch(struct kobject *kobj)
540 {
541         struct klp_patch *patch;
542
543         patch = container_of(kobj, struct klp_patch, kobj);
544         complete(&patch->finish);
545 }
546
547 static struct kobj_type klp_ktype_patch = {
548         .release = klp_kobj_release_patch,
549         .sysfs_ops = &kobj_sysfs_ops,
550         .default_attrs = klp_patch_attrs,
551 };
552
553 static void klp_kobj_release_object(struct kobject *kobj)
554 {
555 }
556
557 static struct kobj_type klp_ktype_object = {
558         .release = klp_kobj_release_object,
559         .sysfs_ops = &kobj_sysfs_ops,
560 };
561
562 static void klp_kobj_release_func(struct kobject *kobj)
563 {
564 }
565
566 static struct kobj_type klp_ktype_func = {
567         .release = klp_kobj_release_func,
568         .sysfs_ops = &kobj_sysfs_ops,
569 };
570
571 /*
572  * Free all functions' kobjects in the array up to some limit. When limit is
573  * NULL, all kobjects are freed.
574  */
575 static void klp_free_funcs_limited(struct klp_object *obj,
576                                    struct klp_func *limit)
577 {
578         struct klp_func *func;
579
580         for (func = obj->funcs; func->old_name && func != limit; func++)
581                 kobject_put(&func->kobj);
582 }
583
584 /* Clean up when a patched object is unloaded */
585 static void klp_free_object_loaded(struct klp_object *obj)
586 {
587         struct klp_func *func;
588
589         obj->mod = NULL;
590
591         klp_for_each_func(obj, func)
592                 func->old_addr = 0;
593 }
594
595 /*
596  * Free all objects' kobjects in the array up to some limit. When limit is
597  * NULL, all kobjects are freed.
598  */
599 static void klp_free_objects_limited(struct klp_patch *patch,
600                                      struct klp_object *limit)
601 {
602         struct klp_object *obj;
603
604         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
605                 klp_free_funcs_limited(obj, NULL);
606                 kobject_put(&obj->kobj);
607         }
608 }
609
610 static void klp_free_patch(struct klp_patch *patch)
611 {
612         klp_free_objects_limited(patch, NULL);
613         if (!list_empty(&patch->list))
614                 list_del(&patch->list);
615 }
616
617 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
618 {
619         if (!func->old_name || !func->new_func)
620                 return -EINVAL;
621
622         INIT_LIST_HEAD(&func->stack_node);
623         func->patched = false;
624         func->transition = false;
625
626         /* The format for the sysfs directory is <function,sympos> where sympos
627          * is the nth occurrence of this symbol in kallsyms for the patched
628          * object. If the user selects 0 for old_sympos, then 1 will be used
629          * since a unique symbol will be the first occurrence.
630          */
631         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
632                                     &obj->kobj, "%s,%lu", func->old_name,
633                                     func->old_sympos ? func->old_sympos : 1);
634 }
635
636 /* Arches may override this to finish any remaining arch-specific tasks */
637 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
638                                         struct klp_object *obj)
639 {
640 }
641
642 /* parts of the initialization that is done only when the object is loaded */
643 static int klp_init_object_loaded(struct klp_patch *patch,
644                                   struct klp_object *obj)
645 {
646         struct klp_func *func;
647         int ret;
648
649         module_disable_ro(patch->mod);
650         ret = klp_write_object_relocations(patch->mod, obj);
651         if (ret) {
652                 module_enable_ro(patch->mod, true);
653                 return ret;
654         }
655
656         arch_klp_init_object_loaded(patch, obj);
657         module_enable_ro(patch->mod, true);
658
659         klp_for_each_func(obj, func) {
660                 ret = klp_find_object_symbol(obj->name, func->old_name,
661                                              func->old_sympos,
662                                              &func->old_addr);
663                 if (ret)
664                         return ret;
665
666                 ret = kallsyms_lookup_size_offset(func->old_addr,
667                                                   &func->old_size, NULL);
668                 if (!ret) {
669                         pr_err("kallsyms size lookup failed for '%s'\n",
670                                func->old_name);
671                         return -ENOENT;
672                 }
673
674                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
675                                                   &func->new_size, NULL);
676                 if (!ret) {
677                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
678                                func->old_name);
679                         return -ENOENT;
680                 }
681         }
682
683         return 0;
684 }
685
686 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
687 {
688         struct klp_func *func;
689         int ret;
690         const char *name;
691
692         if (!obj->funcs)
693                 return -EINVAL;
694
695         obj->patched = false;
696         obj->mod = NULL;
697
698         klp_find_object_module(obj);
699
700         name = klp_is_module(obj) ? obj->name : "vmlinux";
701         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
702                                    &patch->kobj, "%s", name);
703         if (ret)
704                 return ret;
705
706         klp_for_each_func(obj, func) {
707                 ret = klp_init_func(obj, func);
708                 if (ret)
709                         goto free;
710         }
711
712         if (klp_is_object_loaded(obj)) {
713                 ret = klp_init_object_loaded(patch, obj);
714                 if (ret)
715                         goto free;
716         }
717
718         return 0;
719
720 free:
721         klp_free_funcs_limited(obj, func);
722         kobject_put(&obj->kobj);
723         return ret;
724 }
725
726 static int klp_init_patch(struct klp_patch *patch)
727 {
728         struct klp_object *obj;
729         int ret;
730
731         if (!patch->objs)
732                 return -EINVAL;
733
734         mutex_lock(&klp_mutex);
735
736         patch->enabled = false;
737         init_completion(&patch->finish);
738
739         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
740                                    klp_root_kobj, "%s", patch->mod->name);
741         if (ret) {
742                 mutex_unlock(&klp_mutex);
743                 return ret;
744         }
745
746         klp_for_each_object(patch, obj) {
747                 ret = klp_init_object(patch, obj);
748                 if (ret)
749                         goto free;
750         }
751
752         list_add_tail(&patch->list, &klp_patches);
753
754         mutex_unlock(&klp_mutex);
755
756         return 0;
757
758 free:
759         klp_free_objects_limited(patch, obj);
760
761         mutex_unlock(&klp_mutex);
762
763         kobject_put(&patch->kobj);
764         wait_for_completion(&patch->finish);
765
766         return ret;
767 }
768
769 /**
770  * klp_unregister_patch() - unregisters a patch
771  * @patch:      Disabled patch to be unregistered
772  *
773  * Frees the data structures and removes the sysfs interface.
774  *
775  * Return: 0 on success, otherwise error
776  */
777 int klp_unregister_patch(struct klp_patch *patch)
778 {
779         int ret;
780
781         mutex_lock(&klp_mutex);
782
783         if (!klp_is_patch_registered(patch)) {
784                 ret = -EINVAL;
785                 goto err;
786         }
787
788         if (patch->enabled) {
789                 ret = -EBUSY;
790                 goto err;
791         }
792
793         klp_free_patch(patch);
794
795         mutex_unlock(&klp_mutex);
796
797         kobject_put(&patch->kobj);
798         wait_for_completion(&patch->finish);
799
800         return 0;
801 err:
802         mutex_unlock(&klp_mutex);
803         return ret;
804 }
805 EXPORT_SYMBOL_GPL(klp_unregister_patch);
806
807 /**
808  * klp_register_patch() - registers a patch
809  * @patch:      Patch to be registered
810  *
811  * Initializes the data structure associated with the patch and
812  * creates the sysfs interface.
813  *
814  * There is no need to take the reference on the patch module here. It is done
815  * later when the patch is enabled.
816  *
817  * Return: 0 on success, otherwise error
818  */
819 int klp_register_patch(struct klp_patch *patch)
820 {
821         if (!patch || !patch->mod)
822                 return -EINVAL;
823
824         if (!is_livepatch_module(patch->mod)) {
825                 pr_err("module %s is not marked as a livepatch module\n",
826                        patch->mod->name);
827                 return -EINVAL;
828         }
829
830         if (!klp_initialized())
831                 return -ENODEV;
832
833         /*
834          * Architectures without reliable stack traces have to set
835          * patch->immediate because there's currently no way to patch kthreads
836          * with the consistency model.
837          */
838         if (!klp_have_reliable_stack() && !patch->immediate) {
839                 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
840                 return -ENOSYS;
841         }
842
843         return klp_init_patch(patch);
844 }
845 EXPORT_SYMBOL_GPL(klp_register_patch);
846
847 /*
848  * Remove parts of patches that touch a given kernel module. The list of
849  * patches processed might be limited. When limit is NULL, all patches
850  * will be handled.
851  */
852 static void klp_cleanup_module_patches_limited(struct module *mod,
853                                                struct klp_patch *limit)
854 {
855         struct klp_patch *patch;
856         struct klp_object *obj;
857
858         list_for_each_entry(patch, &klp_patches, list) {
859                 if (patch == limit)
860                         break;
861
862                 klp_for_each_object(patch, obj) {
863                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
864                                 continue;
865
866                         /*
867                          * Only unpatch the module if the patch is enabled or
868                          * is in transition.
869                          */
870                         if (patch->enabled || patch == klp_transition_patch) {
871
872                                 if (patch != klp_transition_patch)
873                                         klp_pre_unpatch_callback(obj);
874
875                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
876                                           patch->mod->name, obj->mod->name);
877                                 klp_unpatch_object(obj);
878
879                                 klp_post_unpatch_callback(obj);
880                         }
881
882                         klp_free_object_loaded(obj);
883                         break;
884                 }
885         }
886 }
887
888 int klp_module_coming(struct module *mod)
889 {
890         int ret;
891         struct klp_patch *patch;
892         struct klp_object *obj;
893
894         if (WARN_ON(mod->state != MODULE_STATE_COMING))
895                 return -EINVAL;
896
897         mutex_lock(&klp_mutex);
898         /*
899          * Each module has to know that klp_module_coming()
900          * has been called. We never know what module will
901          * get patched by a new patch.
902          */
903         mod->klp_alive = true;
904
905         list_for_each_entry(patch, &klp_patches, list) {
906                 klp_for_each_object(patch, obj) {
907                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
908                                 continue;
909
910                         obj->mod = mod;
911
912                         ret = klp_init_object_loaded(patch, obj);
913                         if (ret) {
914                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
915                                         patch->mod->name, obj->mod->name, ret);
916                                 goto err;
917                         }
918
919                         /*
920                          * Only patch the module if the patch is enabled or is
921                          * in transition.
922                          */
923                         if (!patch->enabled && patch != klp_transition_patch)
924                                 break;
925
926                         pr_notice("applying patch '%s' to loading module '%s'\n",
927                                   patch->mod->name, obj->mod->name);
928
929                         ret = klp_pre_patch_callback(obj);
930                         if (ret) {
931                                 pr_warn("pre-patch callback failed for object '%s'\n",
932                                         obj->name);
933                                 goto err;
934                         }
935
936                         ret = klp_patch_object(obj);
937                         if (ret) {
938                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
939                                         patch->mod->name, obj->mod->name, ret);
940
941                                 klp_post_unpatch_callback(obj);
942                                 goto err;
943                         }
944
945                         if (patch != klp_transition_patch)
946                                 klp_post_patch_callback(obj);
947
948                         break;
949                 }
950         }
951
952         mutex_unlock(&klp_mutex);
953
954         return 0;
955
956 err:
957         /*
958          * If a patch is unsuccessfully applied, return
959          * error to the module loader.
960          */
961         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
962                 patch->mod->name, obj->mod->name, obj->mod->name);
963         mod->klp_alive = false;
964         klp_cleanup_module_patches_limited(mod, patch);
965         mutex_unlock(&klp_mutex);
966
967         return ret;
968 }
969
970 void klp_module_going(struct module *mod)
971 {
972         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
973                     mod->state != MODULE_STATE_COMING))
974                 return;
975
976         mutex_lock(&klp_mutex);
977         /*
978          * Each module has to know that klp_module_going()
979          * has been called. We never know what module will
980          * get patched by a new patch.
981          */
982         mod->klp_alive = false;
983
984         klp_cleanup_module_patches_limited(mod, NULL);
985
986         mutex_unlock(&klp_mutex);
987 }
988
989 static int __init klp_init(void)
990 {
991         int ret;
992
993         ret = klp_check_compiler_support();
994         if (ret) {
995                 pr_info("Your compiler is too old; turning off.\n");
996                 return -EINVAL;
997         }
998
999         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1000         if (!klp_root_kobj)
1001                 return -ENOMEM;
1002
1003         return 0;
1004 }
1005
1006 module_init(klp_init);