41be6061b92f28650065019b583b48610f6d7240
[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         patch = container_of(kobj, struct klp_patch, kobj);
536
537         /*
538          * klp_mutex lock is not grabbed here intentionally. It is not really
539          * needed. The race window is harmless and grabbing the lock would only
540          * hold the action back.
541          */
542         if (patch != klp_transition_patch)
543                 return -EINVAL;
544
545         ret = kstrtobool(buf, &val);
546         if (ret)
547                 return ret;
548
549         if (val)
550                 klp_send_signals();
551
552         return count;
553 }
554
555 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
556                            const char *buf, size_t count)
557 {
558         struct klp_patch *patch;
559         int ret;
560         bool val;
561
562         patch = container_of(kobj, struct klp_patch, kobj);
563
564         /*
565          * klp_mutex lock is not grabbed here intentionally. It is not really
566          * needed. The race window is harmless and grabbing the lock would only
567          * hold the action back.
568          */
569         if (patch != klp_transition_patch)
570                 return -EINVAL;
571
572         ret = kstrtobool(buf, &val);
573         if (ret)
574                 return ret;
575
576         if (val)
577                 klp_force_transition();
578
579         return count;
580 }
581
582 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
583 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
584 static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
585 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
586 static struct attribute *klp_patch_attrs[] = {
587         &enabled_kobj_attr.attr,
588         &transition_kobj_attr.attr,
589         &signal_kobj_attr.attr,
590         &force_kobj_attr.attr,
591         NULL
592 };
593
594 static void klp_kobj_release_patch(struct kobject *kobj)
595 {
596         struct klp_patch *patch;
597
598         patch = container_of(kobj, struct klp_patch, kobj);
599         complete(&patch->finish);
600 }
601
602 static struct kobj_type klp_ktype_patch = {
603         .release = klp_kobj_release_patch,
604         .sysfs_ops = &kobj_sysfs_ops,
605         .default_attrs = klp_patch_attrs,
606 };
607
608 static void klp_kobj_release_object(struct kobject *kobj)
609 {
610 }
611
612 static struct kobj_type klp_ktype_object = {
613         .release = klp_kobj_release_object,
614         .sysfs_ops = &kobj_sysfs_ops,
615 };
616
617 static void klp_kobj_release_func(struct kobject *kobj)
618 {
619 }
620
621 static struct kobj_type klp_ktype_func = {
622         .release = klp_kobj_release_func,
623         .sysfs_ops = &kobj_sysfs_ops,
624 };
625
626 /*
627  * Free all functions' kobjects in the array up to some limit. When limit is
628  * NULL, all kobjects are freed.
629  */
630 static void klp_free_funcs_limited(struct klp_object *obj,
631                                    struct klp_func *limit)
632 {
633         struct klp_func *func;
634
635         for (func = obj->funcs; func->old_name && func != limit; func++)
636                 kobject_put(&func->kobj);
637 }
638
639 /* Clean up when a patched object is unloaded */
640 static void klp_free_object_loaded(struct klp_object *obj)
641 {
642         struct klp_func *func;
643
644         obj->mod = NULL;
645
646         klp_for_each_func(obj, func)
647                 func->old_addr = 0;
648 }
649
650 /*
651  * Free all objects' kobjects in the array up to some limit. When limit is
652  * NULL, all kobjects are freed.
653  */
654 static void klp_free_objects_limited(struct klp_patch *patch,
655                                      struct klp_object *limit)
656 {
657         struct klp_object *obj;
658
659         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
660                 klp_free_funcs_limited(obj, NULL);
661                 kobject_put(&obj->kobj);
662         }
663 }
664
665 static void klp_free_patch(struct klp_patch *patch)
666 {
667         klp_free_objects_limited(patch, NULL);
668         if (!list_empty(&patch->list))
669                 list_del(&patch->list);
670 }
671
672 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
673 {
674         if (!func->old_name || !func->new_func)
675                 return -EINVAL;
676
677         INIT_LIST_HEAD(&func->stack_node);
678         func->patched = false;
679         func->transition = false;
680
681         /* The format for the sysfs directory is <function,sympos> where sympos
682          * is the nth occurrence of this symbol in kallsyms for the patched
683          * object. If the user selects 0 for old_sympos, then 1 will be used
684          * since a unique symbol will be the first occurrence.
685          */
686         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
687                                     &obj->kobj, "%s,%lu", func->old_name,
688                                     func->old_sympos ? func->old_sympos : 1);
689 }
690
691 /* Arches may override this to finish any remaining arch-specific tasks */
692 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
693                                         struct klp_object *obj)
694 {
695 }
696
697 /* parts of the initialization that is done only when the object is loaded */
698 static int klp_init_object_loaded(struct klp_patch *patch,
699                                   struct klp_object *obj)
700 {
701         struct klp_func *func;
702         int ret;
703
704         module_disable_ro(patch->mod);
705         ret = klp_write_object_relocations(patch->mod, obj);
706         if (ret) {
707                 module_enable_ro(patch->mod, true);
708                 return ret;
709         }
710
711         arch_klp_init_object_loaded(patch, obj);
712         module_enable_ro(patch->mod, true);
713
714         klp_for_each_func(obj, func) {
715                 ret = klp_find_object_symbol(obj->name, func->old_name,
716                                              func->old_sympos,
717                                              &func->old_addr);
718                 if (ret)
719                         return ret;
720
721                 ret = kallsyms_lookup_size_offset(func->old_addr,
722                                                   &func->old_size, NULL);
723                 if (!ret) {
724                         pr_err("kallsyms size lookup failed for '%s'\n",
725                                func->old_name);
726                         return -ENOENT;
727                 }
728
729                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
730                                                   &func->new_size, NULL);
731                 if (!ret) {
732                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
733                                func->old_name);
734                         return -ENOENT;
735                 }
736         }
737
738         return 0;
739 }
740
741 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
742 {
743         struct klp_func *func;
744         int ret;
745         const char *name;
746
747         if (!obj->funcs)
748                 return -EINVAL;
749
750         obj->patched = false;
751         obj->mod = NULL;
752
753         klp_find_object_module(obj);
754
755         name = klp_is_module(obj) ? obj->name : "vmlinux";
756         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
757                                    &patch->kobj, "%s", name);
758         if (ret)
759                 return ret;
760
761         klp_for_each_func(obj, func) {
762                 ret = klp_init_func(obj, func);
763                 if (ret)
764                         goto free;
765         }
766
767         if (klp_is_object_loaded(obj)) {
768                 ret = klp_init_object_loaded(patch, obj);
769                 if (ret)
770                         goto free;
771         }
772
773         return 0;
774
775 free:
776         klp_free_funcs_limited(obj, func);
777         kobject_put(&obj->kobj);
778         return ret;
779 }
780
781 static int klp_init_patch(struct klp_patch *patch)
782 {
783         struct klp_object *obj;
784         int ret;
785
786         if (!patch->objs)
787                 return -EINVAL;
788
789         mutex_lock(&klp_mutex);
790
791         patch->enabled = false;
792         init_completion(&patch->finish);
793
794         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
795                                    klp_root_kobj, "%s", patch->mod->name);
796         if (ret) {
797                 mutex_unlock(&klp_mutex);
798                 return ret;
799         }
800
801         klp_for_each_object(patch, obj) {
802                 ret = klp_init_object(patch, obj);
803                 if (ret)
804                         goto free;
805         }
806
807         list_add_tail(&patch->list, &klp_patches);
808
809         mutex_unlock(&klp_mutex);
810
811         return 0;
812
813 free:
814         klp_free_objects_limited(patch, obj);
815
816         mutex_unlock(&klp_mutex);
817
818         kobject_put(&patch->kobj);
819         wait_for_completion(&patch->finish);
820
821         return ret;
822 }
823
824 /**
825  * klp_unregister_patch() - unregisters a patch
826  * @patch:      Disabled patch to be unregistered
827  *
828  * Frees the data structures and removes the sysfs interface.
829  *
830  * Return: 0 on success, otherwise error
831  */
832 int klp_unregister_patch(struct klp_patch *patch)
833 {
834         int ret;
835
836         mutex_lock(&klp_mutex);
837
838         if (!klp_is_patch_registered(patch)) {
839                 ret = -EINVAL;
840                 goto err;
841         }
842
843         if (patch->enabled) {
844                 ret = -EBUSY;
845                 goto err;
846         }
847
848         klp_free_patch(patch);
849
850         mutex_unlock(&klp_mutex);
851
852         kobject_put(&patch->kobj);
853         wait_for_completion(&patch->finish);
854
855         return 0;
856 err:
857         mutex_unlock(&klp_mutex);
858         return ret;
859 }
860 EXPORT_SYMBOL_GPL(klp_unregister_patch);
861
862 /**
863  * klp_register_patch() - registers a patch
864  * @patch:      Patch to be registered
865  *
866  * Initializes the data structure associated with the patch and
867  * creates the sysfs interface.
868  *
869  * There is no need to take the reference on the patch module here. It is done
870  * later when the patch is enabled.
871  *
872  * Return: 0 on success, otherwise error
873  */
874 int klp_register_patch(struct klp_patch *patch)
875 {
876         if (!patch || !patch->mod)
877                 return -EINVAL;
878
879         if (!is_livepatch_module(patch->mod)) {
880                 pr_err("module %s is not marked as a livepatch module\n",
881                        patch->mod->name);
882                 return -EINVAL;
883         }
884
885         if (!klp_initialized())
886                 return -ENODEV;
887
888         if (!klp_have_reliable_stack()) {
889                 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
890                 return -ENOSYS;
891         }
892
893         return klp_init_patch(patch);
894 }
895 EXPORT_SYMBOL_GPL(klp_register_patch);
896
897 /*
898  * Remove parts of patches that touch a given kernel module. The list of
899  * patches processed might be limited. When limit is NULL, all patches
900  * will be handled.
901  */
902 static void klp_cleanup_module_patches_limited(struct module *mod,
903                                                struct klp_patch *limit)
904 {
905         struct klp_patch *patch;
906         struct klp_object *obj;
907
908         list_for_each_entry(patch, &klp_patches, list) {
909                 if (patch == limit)
910                         break;
911
912                 klp_for_each_object(patch, obj) {
913                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
914                                 continue;
915
916                         /*
917                          * Only unpatch the module if the patch is enabled or
918                          * is in transition.
919                          */
920                         if (patch->enabled || patch == klp_transition_patch) {
921
922                                 if (patch != klp_transition_patch)
923                                         klp_pre_unpatch_callback(obj);
924
925                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
926                                           patch->mod->name, obj->mod->name);
927                                 klp_unpatch_object(obj);
928
929                                 klp_post_unpatch_callback(obj);
930                         }
931
932                         klp_free_object_loaded(obj);
933                         break;
934                 }
935         }
936 }
937
938 int klp_module_coming(struct module *mod)
939 {
940         int ret;
941         struct klp_patch *patch;
942         struct klp_object *obj;
943
944         if (WARN_ON(mod->state != MODULE_STATE_COMING))
945                 return -EINVAL;
946
947         mutex_lock(&klp_mutex);
948         /*
949          * Each module has to know that klp_module_coming()
950          * has been called. We never know what module will
951          * get patched by a new patch.
952          */
953         mod->klp_alive = true;
954
955         list_for_each_entry(patch, &klp_patches, list) {
956                 klp_for_each_object(patch, obj) {
957                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
958                                 continue;
959
960                         obj->mod = mod;
961
962                         ret = klp_init_object_loaded(patch, obj);
963                         if (ret) {
964                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
965                                         patch->mod->name, obj->mod->name, ret);
966                                 goto err;
967                         }
968
969                         /*
970                          * Only patch the module if the patch is enabled or is
971                          * in transition.
972                          */
973                         if (!patch->enabled && patch != klp_transition_patch)
974                                 break;
975
976                         pr_notice("applying patch '%s' to loading module '%s'\n",
977                                   patch->mod->name, obj->mod->name);
978
979                         ret = klp_pre_patch_callback(obj);
980                         if (ret) {
981                                 pr_warn("pre-patch callback failed for object '%s'\n",
982                                         obj->name);
983                                 goto err;
984                         }
985
986                         ret = klp_patch_object(obj);
987                         if (ret) {
988                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
989                                         patch->mod->name, obj->mod->name, ret);
990
991                                 klp_post_unpatch_callback(obj);
992                                 goto err;
993                         }
994
995                         if (patch != klp_transition_patch)
996                                 klp_post_patch_callback(obj);
997
998                         break;
999                 }
1000         }
1001
1002         mutex_unlock(&klp_mutex);
1003
1004         return 0;
1005
1006 err:
1007         /*
1008          * If a patch is unsuccessfully applied, return
1009          * error to the module loader.
1010          */
1011         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1012                 patch->mod->name, obj->mod->name, obj->mod->name);
1013         mod->klp_alive = false;
1014         klp_cleanup_module_patches_limited(mod, patch);
1015         mutex_unlock(&klp_mutex);
1016
1017         return ret;
1018 }
1019
1020 void klp_module_going(struct module *mod)
1021 {
1022         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1023                     mod->state != MODULE_STATE_COMING))
1024                 return;
1025
1026         mutex_lock(&klp_mutex);
1027         /*
1028          * Each module has to know that klp_module_going()
1029          * has been called. We never know what module will
1030          * get patched by a new patch.
1031          */
1032         mod->klp_alive = false;
1033
1034         klp_cleanup_module_patches_limited(mod, NULL);
1035
1036         mutex_unlock(&klp_mutex);
1037 }
1038
1039 static int __init klp_init(void)
1040 {
1041         int ret;
1042
1043         ret = klp_check_compiler_support();
1044         if (ret) {
1045                 pr_info("Your compiler is too old; turning off.\n");
1046                 return -EINVAL;
1047         }
1048
1049         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1050         if (!klp_root_kobj)
1051                 return -ENOMEM;
1052
1053         return 0;
1054 }
1055
1056 module_init(klp_init);