Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livep...
[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         if (!try_module_get(patch->mod))
371                 return -ENODEV;
372
373         pr_notice("enabling patch '%s'\n", patch->mod->name);
374
375         klp_init_transition(patch, KLP_PATCHED);
376
377         /*
378          * Enforce the order of the func->transition writes in
379          * klp_init_transition() and the ops->func_stack writes in
380          * klp_patch_object(), so that klp_ftrace_handler() will see the
381          * func->transition updates before the handler is registered and the
382          * new funcs become visible to the handler.
383          */
384         smp_wmb();
385
386         klp_for_each_object(patch, obj) {
387                 if (!klp_is_object_loaded(obj))
388                         continue;
389
390                 ret = klp_pre_patch_callback(obj);
391                 if (ret) {
392                         pr_warn("pre-patch callback failed for object '%s'\n",
393                                 klp_is_module(obj) ? obj->name : "vmlinux");
394                         goto err;
395                 }
396
397                 ret = klp_patch_object(obj);
398                 if (ret) {
399                         pr_warn("failed to patch object '%s'\n",
400                                 klp_is_module(obj) ? obj->name : "vmlinux");
401                         goto err;
402                 }
403         }
404
405         klp_start_transition();
406         klp_try_complete_transition();
407         patch->enabled = true;
408
409         return 0;
410 err:
411         pr_warn("failed to enable patch '%s'\n", patch->mod->name);
412
413         klp_cancel_transition();
414         return ret;
415 }
416
417 /**
418  * klp_enable_patch() - enables a registered patch
419  * @patch:      The registered, disabled patch to be enabled
420  *
421  * Performs the needed symbol lookups and code relocations,
422  * then registers the patched functions with ftrace.
423  *
424  * Return: 0 on success, otherwise error
425  */
426 int klp_enable_patch(struct klp_patch *patch)
427 {
428         int ret;
429
430         mutex_lock(&klp_mutex);
431
432         if (!klp_is_patch_registered(patch)) {
433                 ret = -EINVAL;
434                 goto err;
435         }
436
437         ret = __klp_enable_patch(patch);
438
439 err:
440         mutex_unlock(&klp_mutex);
441         return ret;
442 }
443 EXPORT_SYMBOL_GPL(klp_enable_patch);
444
445 /*
446  * Sysfs Interface
447  *
448  * /sys/kernel/livepatch
449  * /sys/kernel/livepatch/<patch>
450  * /sys/kernel/livepatch/<patch>/enabled
451  * /sys/kernel/livepatch/<patch>/transition
452  * /sys/kernel/livepatch/<patch>/signal
453  * /sys/kernel/livepatch/<patch>/force
454  * /sys/kernel/livepatch/<patch>/<object>
455  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
456  */
457
458 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
459                              const char *buf, size_t count)
460 {
461         struct klp_patch *patch;
462         int ret;
463         bool enabled;
464
465         ret = kstrtobool(buf, &enabled);
466         if (ret)
467                 return ret;
468
469         patch = container_of(kobj, struct klp_patch, kobj);
470
471         mutex_lock(&klp_mutex);
472
473         if (!klp_is_patch_registered(patch)) {
474                 /*
475                  * Module with the patch could either disappear meanwhile or is
476                  * not properly initialized yet.
477                  */
478                 ret = -EINVAL;
479                 goto err;
480         }
481
482         if (patch->enabled == enabled) {
483                 /* already in requested state */
484                 ret = -EINVAL;
485                 goto err;
486         }
487
488         if (patch == klp_transition_patch) {
489                 klp_reverse_transition();
490         } else if (enabled) {
491                 ret = __klp_enable_patch(patch);
492                 if (ret)
493                         goto err;
494         } else {
495                 ret = __klp_disable_patch(patch);
496                 if (ret)
497                         goto err;
498         }
499
500         mutex_unlock(&klp_mutex);
501
502         return count;
503
504 err:
505         mutex_unlock(&klp_mutex);
506         return ret;
507 }
508
509 static ssize_t enabled_show(struct kobject *kobj,
510                             struct kobj_attribute *attr, char *buf)
511 {
512         struct klp_patch *patch;
513
514         patch = container_of(kobj, struct klp_patch, kobj);
515         return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
516 }
517
518 static ssize_t transition_show(struct kobject *kobj,
519                                struct kobj_attribute *attr, char *buf)
520 {
521         struct klp_patch *patch;
522
523         patch = container_of(kobj, struct klp_patch, kobj);
524         return snprintf(buf, PAGE_SIZE-1, "%d\n",
525                         patch == klp_transition_patch);
526 }
527
528 static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
529                             const char *buf, size_t count)
530 {
531         struct klp_patch *patch;
532         int ret;
533         bool val;
534
535         ret = kstrtobool(buf, &val);
536         if (ret)
537                 return ret;
538
539         if (!val)
540                 return count;
541
542         mutex_lock(&klp_mutex);
543
544         patch = container_of(kobj, struct klp_patch, kobj);
545         if (patch != klp_transition_patch) {
546                 mutex_unlock(&klp_mutex);
547                 return -EINVAL;
548         }
549
550         klp_send_signals();
551
552         mutex_unlock(&klp_mutex);
553
554         return count;
555 }
556
557 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
558                            const char *buf, size_t count)
559 {
560         struct klp_patch *patch;
561         int ret;
562         bool val;
563
564         ret = kstrtobool(buf, &val);
565         if (ret)
566                 return ret;
567
568         if (!val)
569                 return count;
570
571         mutex_lock(&klp_mutex);
572
573         patch = container_of(kobj, struct klp_patch, kobj);
574         if (patch != klp_transition_patch) {
575                 mutex_unlock(&klp_mutex);
576                 return -EINVAL;
577         }
578
579         klp_force_transition();
580
581         mutex_unlock(&klp_mutex);
582
583         return count;
584 }
585
586 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
587 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
588 static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
589 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
590 static struct attribute *klp_patch_attrs[] = {
591         &enabled_kobj_attr.attr,
592         &transition_kobj_attr.attr,
593         &signal_kobj_attr.attr,
594         &force_kobj_attr.attr,
595         NULL
596 };
597
598 static void klp_kobj_release_patch(struct kobject *kobj)
599 {
600         struct klp_patch *patch;
601
602         patch = container_of(kobj, struct klp_patch, kobj);
603         complete(&patch->finish);
604 }
605
606 static struct kobj_type klp_ktype_patch = {
607         .release = klp_kobj_release_patch,
608         .sysfs_ops = &kobj_sysfs_ops,
609         .default_attrs = klp_patch_attrs,
610 };
611
612 static void klp_kobj_release_object(struct kobject *kobj)
613 {
614 }
615
616 static struct kobj_type klp_ktype_object = {
617         .release = klp_kobj_release_object,
618         .sysfs_ops = &kobj_sysfs_ops,
619 };
620
621 static void klp_kobj_release_func(struct kobject *kobj)
622 {
623 }
624
625 static struct kobj_type klp_ktype_func = {
626         .release = klp_kobj_release_func,
627         .sysfs_ops = &kobj_sysfs_ops,
628 };
629
630 /*
631  * Free all functions' kobjects in the array up to some limit. When limit is
632  * NULL, all kobjects are freed.
633  */
634 static void klp_free_funcs_limited(struct klp_object *obj,
635                                    struct klp_func *limit)
636 {
637         struct klp_func *func;
638
639         for (func = obj->funcs; func->old_name && func != limit; func++)
640                 kobject_put(&func->kobj);
641 }
642
643 /* Clean up when a patched object is unloaded */
644 static void klp_free_object_loaded(struct klp_object *obj)
645 {
646         struct klp_func *func;
647
648         obj->mod = NULL;
649
650         klp_for_each_func(obj, func)
651                 func->old_addr = 0;
652 }
653
654 /*
655  * Free all objects' kobjects in the array up to some limit. When limit is
656  * NULL, all kobjects are freed.
657  */
658 static void klp_free_objects_limited(struct klp_patch *patch,
659                                      struct klp_object *limit)
660 {
661         struct klp_object *obj;
662
663         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
664                 klp_free_funcs_limited(obj, NULL);
665                 kobject_put(&obj->kobj);
666         }
667 }
668
669 static void klp_free_patch(struct klp_patch *patch)
670 {
671         klp_free_objects_limited(patch, NULL);
672         if (!list_empty(&patch->list))
673                 list_del(&patch->list);
674 }
675
676 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
677 {
678         if (!func->old_name || !func->new_func)
679                 return -EINVAL;
680
681         INIT_LIST_HEAD(&func->stack_node);
682         func->patched = false;
683         func->transition = false;
684
685         /* The format for the sysfs directory is <function,sympos> where sympos
686          * is the nth occurrence of this symbol in kallsyms for the patched
687          * object. If the user selects 0 for old_sympos, then 1 will be used
688          * since a unique symbol will be the first occurrence.
689          */
690         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
691                                     &obj->kobj, "%s,%lu", func->old_name,
692                                     func->old_sympos ? func->old_sympos : 1);
693 }
694
695 /* Arches may override this to finish any remaining arch-specific tasks */
696 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
697                                         struct klp_object *obj)
698 {
699 }
700
701 /* parts of the initialization that is done only when the object is loaded */
702 static int klp_init_object_loaded(struct klp_patch *patch,
703                                   struct klp_object *obj)
704 {
705         struct klp_func *func;
706         int ret;
707
708         module_disable_ro(patch->mod);
709         ret = klp_write_object_relocations(patch->mod, obj);
710         if (ret) {
711                 module_enable_ro(patch->mod, true);
712                 return ret;
713         }
714
715         arch_klp_init_object_loaded(patch, obj);
716         module_enable_ro(patch->mod, true);
717
718         klp_for_each_func(obj, func) {
719                 ret = klp_find_object_symbol(obj->name, func->old_name,
720                                              func->old_sympos,
721                                              &func->old_addr);
722                 if (ret)
723                         return ret;
724
725                 ret = kallsyms_lookup_size_offset(func->old_addr,
726                                                   &func->old_size, NULL);
727                 if (!ret) {
728                         pr_err("kallsyms size lookup failed for '%s'\n",
729                                func->old_name);
730                         return -ENOENT;
731                 }
732
733                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
734                                                   &func->new_size, NULL);
735                 if (!ret) {
736                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
737                                func->old_name);
738                         return -ENOENT;
739                 }
740         }
741
742         return 0;
743 }
744
745 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
746 {
747         struct klp_func *func;
748         int ret;
749         const char *name;
750
751         if (!obj->funcs)
752                 return -EINVAL;
753
754         obj->patched = false;
755         obj->mod = NULL;
756
757         klp_find_object_module(obj);
758
759         name = klp_is_module(obj) ? obj->name : "vmlinux";
760         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
761                                    &patch->kobj, "%s", name);
762         if (ret)
763                 return ret;
764
765         klp_for_each_func(obj, func) {
766                 ret = klp_init_func(obj, func);
767                 if (ret)
768                         goto free;
769         }
770
771         if (klp_is_object_loaded(obj)) {
772                 ret = klp_init_object_loaded(patch, obj);
773                 if (ret)
774                         goto free;
775         }
776
777         return 0;
778
779 free:
780         klp_free_funcs_limited(obj, func);
781         kobject_put(&obj->kobj);
782         return ret;
783 }
784
785 static int klp_init_patch(struct klp_patch *patch)
786 {
787         struct klp_object *obj;
788         int ret;
789
790         if (!patch->objs)
791                 return -EINVAL;
792
793         mutex_lock(&klp_mutex);
794
795         patch->enabled = false;
796         init_completion(&patch->finish);
797
798         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
799                                    klp_root_kobj, "%s", patch->mod->name);
800         if (ret) {
801                 mutex_unlock(&klp_mutex);
802                 return ret;
803         }
804
805         klp_for_each_object(patch, obj) {
806                 ret = klp_init_object(patch, obj);
807                 if (ret)
808                         goto free;
809         }
810
811         list_add_tail(&patch->list, &klp_patches);
812
813         mutex_unlock(&klp_mutex);
814
815         return 0;
816
817 free:
818         klp_free_objects_limited(patch, obj);
819
820         mutex_unlock(&klp_mutex);
821
822         kobject_put(&patch->kobj);
823         wait_for_completion(&patch->finish);
824
825         return ret;
826 }
827
828 /**
829  * klp_unregister_patch() - unregisters a patch
830  * @patch:      Disabled patch to be unregistered
831  *
832  * Frees the data structures and removes the sysfs interface.
833  *
834  * Return: 0 on success, otherwise error
835  */
836 int klp_unregister_patch(struct klp_patch *patch)
837 {
838         int ret;
839
840         mutex_lock(&klp_mutex);
841
842         if (!klp_is_patch_registered(patch)) {
843                 ret = -EINVAL;
844                 goto err;
845         }
846
847         if (patch->enabled) {
848                 ret = -EBUSY;
849                 goto err;
850         }
851
852         klp_free_patch(patch);
853
854         mutex_unlock(&klp_mutex);
855
856         kobject_put(&patch->kobj);
857         wait_for_completion(&patch->finish);
858
859         return 0;
860 err:
861         mutex_unlock(&klp_mutex);
862         return ret;
863 }
864 EXPORT_SYMBOL_GPL(klp_unregister_patch);
865
866 /**
867  * klp_register_patch() - registers a patch
868  * @patch:      Patch to be registered
869  *
870  * Initializes the data structure associated with the patch and
871  * creates the sysfs interface.
872  *
873  * There is no need to take the reference on the patch module here. It is done
874  * later when the patch is enabled.
875  *
876  * Return: 0 on success, otherwise error
877  */
878 int klp_register_patch(struct klp_patch *patch)
879 {
880         if (!patch || !patch->mod)
881                 return -EINVAL;
882
883         if (!is_livepatch_module(patch->mod)) {
884                 pr_err("module %s is not marked as a livepatch module\n",
885                        patch->mod->name);
886                 return -EINVAL;
887         }
888
889         if (!klp_initialized())
890                 return -ENODEV;
891
892         if (!klp_have_reliable_stack()) {
893                 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
894                 return -ENOSYS;
895         }
896
897         return klp_init_patch(patch);
898 }
899 EXPORT_SYMBOL_GPL(klp_register_patch);
900
901 /*
902  * Remove parts of patches that touch a given kernel module. The list of
903  * patches processed might be limited. When limit is NULL, all patches
904  * will be handled.
905  */
906 static void klp_cleanup_module_patches_limited(struct module *mod,
907                                                struct klp_patch *limit)
908 {
909         struct klp_patch *patch;
910         struct klp_object *obj;
911
912         list_for_each_entry(patch, &klp_patches, list) {
913                 if (patch == limit)
914                         break;
915
916                 klp_for_each_object(patch, obj) {
917                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
918                                 continue;
919
920                         /*
921                          * Only unpatch the module if the patch is enabled or
922                          * is in transition.
923                          */
924                         if (patch->enabled || patch == klp_transition_patch) {
925
926                                 if (patch != klp_transition_patch)
927                                         klp_pre_unpatch_callback(obj);
928
929                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
930                                           patch->mod->name, obj->mod->name);
931                                 klp_unpatch_object(obj);
932
933                                 klp_post_unpatch_callback(obj);
934                         }
935
936                         klp_free_object_loaded(obj);
937                         break;
938                 }
939         }
940 }
941
942 int klp_module_coming(struct module *mod)
943 {
944         int ret;
945         struct klp_patch *patch;
946         struct klp_object *obj;
947
948         if (WARN_ON(mod->state != MODULE_STATE_COMING))
949                 return -EINVAL;
950
951         mutex_lock(&klp_mutex);
952         /*
953          * Each module has to know that klp_module_coming()
954          * has been called. We never know what module will
955          * get patched by a new patch.
956          */
957         mod->klp_alive = true;
958
959         list_for_each_entry(patch, &klp_patches, list) {
960                 klp_for_each_object(patch, obj) {
961                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
962                                 continue;
963
964                         obj->mod = mod;
965
966                         ret = klp_init_object_loaded(patch, obj);
967                         if (ret) {
968                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
969                                         patch->mod->name, obj->mod->name, ret);
970                                 goto err;
971                         }
972
973                         /*
974                          * Only patch the module if the patch is enabled or is
975                          * in transition.
976                          */
977                         if (!patch->enabled && patch != klp_transition_patch)
978                                 break;
979
980                         pr_notice("applying patch '%s' to loading module '%s'\n",
981                                   patch->mod->name, obj->mod->name);
982
983                         ret = klp_pre_patch_callback(obj);
984                         if (ret) {
985                                 pr_warn("pre-patch callback failed for object '%s'\n",
986                                         obj->name);
987                                 goto err;
988                         }
989
990                         ret = klp_patch_object(obj);
991                         if (ret) {
992                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
993                                         patch->mod->name, obj->mod->name, ret);
994
995                                 klp_post_unpatch_callback(obj);
996                                 goto err;
997                         }
998
999                         if (patch != klp_transition_patch)
1000                                 klp_post_patch_callback(obj);
1001
1002                         break;
1003                 }
1004         }
1005
1006         mutex_unlock(&klp_mutex);
1007
1008         return 0;
1009
1010 err:
1011         /*
1012          * If a patch is unsuccessfully applied, return
1013          * error to the module loader.
1014          */
1015         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1016                 patch->mod->name, obj->mod->name, obj->mod->name);
1017         mod->klp_alive = false;
1018         klp_cleanup_module_patches_limited(mod, patch);
1019         mutex_unlock(&klp_mutex);
1020
1021         return ret;
1022 }
1023
1024 void klp_module_going(struct module *mod)
1025 {
1026         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1027                     mod->state != MODULE_STATE_COMING))
1028                 return;
1029
1030         mutex_lock(&klp_mutex);
1031         /*
1032          * Each module has to know that klp_module_going()
1033          * has been called. We never know what module will
1034          * get patched by a new patch.
1035          */
1036         mod->klp_alive = false;
1037
1038         klp_cleanup_module_patches_limited(mod, NULL);
1039
1040         mutex_unlock(&klp_mutex);
1041 }
1042
1043 static int __init klp_init(void)
1044 {
1045         int ret;
1046
1047         ret = klp_check_compiler_support();
1048         if (ret) {
1049                 pr_info("Your compiler is too old; turning off.\n");
1050                 return -EINVAL;
1051         }
1052
1053         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1054         if (!klp_root_kobj)
1055                 return -ENOMEM;
1056
1057         return 0;
1058 }
1059
1060 module_init(klp_init);