livepatch: add (un)patch callbacks
[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 (klp_transition_patch)
286                 return -EBUSY;
287
288         /* enforce stacking: only the last enabled patch can be disabled */
289         if (!list_is_last(&patch->list, &klp_patches) &&
290             list_next_entry(patch, list)->enabled)
291                 return -EBUSY;
292
293         klp_init_transition(patch, KLP_UNPATCHED);
294
295         klp_for_each_object(patch, obj)
296                 if (patch->enabled && obj->patched)
297                         klp_pre_unpatch_callback(obj);
298
299         /*
300          * Enforce the order of the func->transition writes in
301          * klp_init_transition() and the TIF_PATCH_PENDING writes in
302          * klp_start_transition().  In the rare case where klp_ftrace_handler()
303          * is called shortly after klp_update_patch_state() switches the task,
304          * this ensures the handler sees that func->transition is set.
305          */
306         smp_wmb();
307
308         klp_start_transition();
309         klp_try_complete_transition();
310         patch->enabled = false;
311
312         return 0;
313 }
314
315 /**
316  * klp_disable_patch() - disables a registered patch
317  * @patch:      The registered, enabled patch to be disabled
318  *
319  * Unregisters the patched functions from ftrace.
320  *
321  * Return: 0 on success, otherwise error
322  */
323 int klp_disable_patch(struct klp_patch *patch)
324 {
325         int ret;
326
327         mutex_lock(&klp_mutex);
328
329         if (!klp_is_patch_registered(patch)) {
330                 ret = -EINVAL;
331                 goto err;
332         }
333
334         if (!patch->enabled) {
335                 ret = -EINVAL;
336                 goto err;
337         }
338
339         ret = __klp_disable_patch(patch);
340
341 err:
342         mutex_unlock(&klp_mutex);
343         return ret;
344 }
345 EXPORT_SYMBOL_GPL(klp_disable_patch);
346
347 static int __klp_enable_patch(struct klp_patch *patch)
348 {
349         struct klp_object *obj;
350         int ret;
351
352         if (klp_transition_patch)
353                 return -EBUSY;
354
355         if (WARN_ON(patch->enabled))
356                 return -EINVAL;
357
358         /* enforce stacking: only the first disabled patch can be enabled */
359         if (patch->list.prev != &klp_patches &&
360             !list_prev_entry(patch, list)->enabled)
361                 return -EBUSY;
362
363         /*
364          * A reference is taken on the patch module to prevent it from being
365          * unloaded.
366          *
367          * Note: For immediate (no consistency model) patches we don't allow
368          * patch modules to unload since there is no safe/sane method to
369          * determine if a thread is still running in the patched code contained
370          * in the patch module once the ftrace registration is successful.
371          */
372         if (!try_module_get(patch->mod))
373                 return -ENODEV;
374
375         pr_notice("enabling patch '%s'\n", patch->mod->name);
376
377         klp_init_transition(patch, KLP_PATCHED);
378
379         /*
380          * Enforce the order of the func->transition writes in
381          * klp_init_transition() and the ops->func_stack writes in
382          * klp_patch_object(), so that klp_ftrace_handler() will see the
383          * func->transition updates before the handler is registered and the
384          * new funcs become visible to the handler.
385          */
386         smp_wmb();
387
388         klp_for_each_object(patch, obj) {
389                 if (!klp_is_object_loaded(obj))
390                         continue;
391
392                 ret = klp_pre_patch_callback(obj);
393                 if (ret) {
394                         pr_warn("pre-patch callback failed for object '%s'\n",
395                                 klp_is_module(obj) ? obj->name : "vmlinux");
396                         goto err;
397                 }
398
399                 ret = klp_patch_object(obj);
400                 if (ret) {
401                         pr_warn("failed to patch object '%s'\n",
402                                 klp_is_module(obj) ? obj->name : "vmlinux");
403                         goto err;
404                 }
405         }
406
407         klp_start_transition();
408         klp_try_complete_transition();
409         patch->enabled = true;
410
411         return 0;
412 err:
413         pr_warn("failed to enable patch '%s'\n", patch->mod->name);
414
415         klp_cancel_transition();
416         return ret;
417 }
418
419 /**
420  * klp_enable_patch() - enables a registered patch
421  * @patch:      The registered, disabled patch to be enabled
422  *
423  * Performs the needed symbol lookups and code relocations,
424  * then registers the patched functions with ftrace.
425  *
426  * Return: 0 on success, otherwise error
427  */
428 int klp_enable_patch(struct klp_patch *patch)
429 {
430         int ret;
431
432         mutex_lock(&klp_mutex);
433
434         if (!klp_is_patch_registered(patch)) {
435                 ret = -EINVAL;
436                 goto err;
437         }
438
439         ret = __klp_enable_patch(patch);
440
441 err:
442         mutex_unlock(&klp_mutex);
443         return ret;
444 }
445 EXPORT_SYMBOL_GPL(klp_enable_patch);
446
447 /*
448  * Sysfs Interface
449  *
450  * /sys/kernel/livepatch
451  * /sys/kernel/livepatch/<patch>
452  * /sys/kernel/livepatch/<patch>/enabled
453  * /sys/kernel/livepatch/<patch>/transition
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 struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
529 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
530 static struct attribute *klp_patch_attrs[] = {
531         &enabled_kobj_attr.attr,
532         &transition_kobj_attr.attr,
533         NULL
534 };
535
536 static void klp_kobj_release_patch(struct kobject *kobj)
537 {
538         struct klp_patch *patch;
539
540         patch = container_of(kobj, struct klp_patch, kobj);
541         complete(&patch->finish);
542 }
543
544 static struct kobj_type klp_ktype_patch = {
545         .release = klp_kobj_release_patch,
546         .sysfs_ops = &kobj_sysfs_ops,
547         .default_attrs = klp_patch_attrs,
548 };
549
550 static void klp_kobj_release_object(struct kobject *kobj)
551 {
552 }
553
554 static struct kobj_type klp_ktype_object = {
555         .release = klp_kobj_release_object,
556         .sysfs_ops = &kobj_sysfs_ops,
557 };
558
559 static void klp_kobj_release_func(struct kobject *kobj)
560 {
561 }
562
563 static struct kobj_type klp_ktype_func = {
564         .release = klp_kobj_release_func,
565         .sysfs_ops = &kobj_sysfs_ops,
566 };
567
568 /*
569  * Free all functions' kobjects in the array up to some limit. When limit is
570  * NULL, all kobjects are freed.
571  */
572 static void klp_free_funcs_limited(struct klp_object *obj,
573                                    struct klp_func *limit)
574 {
575         struct klp_func *func;
576
577         for (func = obj->funcs; func->old_name && func != limit; func++)
578                 kobject_put(&func->kobj);
579 }
580
581 /* Clean up when a patched object is unloaded */
582 static void klp_free_object_loaded(struct klp_object *obj)
583 {
584         struct klp_func *func;
585
586         obj->mod = NULL;
587
588         klp_for_each_func(obj, func)
589                 func->old_addr = 0;
590 }
591
592 /*
593  * Free all objects' kobjects in the array up to some limit. When limit is
594  * NULL, all kobjects are freed.
595  */
596 static void klp_free_objects_limited(struct klp_patch *patch,
597                                      struct klp_object *limit)
598 {
599         struct klp_object *obj;
600
601         for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
602                 klp_free_funcs_limited(obj, NULL);
603                 kobject_put(&obj->kobj);
604         }
605 }
606
607 static void klp_free_patch(struct klp_patch *patch)
608 {
609         klp_free_objects_limited(patch, NULL);
610         if (!list_empty(&patch->list))
611                 list_del(&patch->list);
612 }
613
614 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
615 {
616         if (!func->old_name || !func->new_func)
617                 return -EINVAL;
618
619         INIT_LIST_HEAD(&func->stack_node);
620         func->patched = false;
621         func->transition = false;
622
623         /* The format for the sysfs directory is <function,sympos> where sympos
624          * is the nth occurrence of this symbol in kallsyms for the patched
625          * object. If the user selects 0 for old_sympos, then 1 will be used
626          * since a unique symbol will be the first occurrence.
627          */
628         return kobject_init_and_add(&func->kobj, &klp_ktype_func,
629                                     &obj->kobj, "%s,%lu", func->old_name,
630                                     func->old_sympos ? func->old_sympos : 1);
631 }
632
633 /* Arches may override this to finish any remaining arch-specific tasks */
634 void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
635                                         struct klp_object *obj)
636 {
637 }
638
639 /* parts of the initialization that is done only when the object is loaded */
640 static int klp_init_object_loaded(struct klp_patch *patch,
641                                   struct klp_object *obj)
642 {
643         struct klp_func *func;
644         int ret;
645
646         module_disable_ro(patch->mod);
647         ret = klp_write_object_relocations(patch->mod, obj);
648         if (ret) {
649                 module_enable_ro(patch->mod, true);
650                 return ret;
651         }
652
653         arch_klp_init_object_loaded(patch, obj);
654         module_enable_ro(patch->mod, true);
655
656         klp_for_each_func(obj, func) {
657                 ret = klp_find_object_symbol(obj->name, func->old_name,
658                                              func->old_sympos,
659                                              &func->old_addr);
660                 if (ret)
661                         return ret;
662
663                 ret = kallsyms_lookup_size_offset(func->old_addr,
664                                                   &func->old_size, NULL);
665                 if (!ret) {
666                         pr_err("kallsyms size lookup failed for '%s'\n",
667                                func->old_name);
668                         return -ENOENT;
669                 }
670
671                 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
672                                                   &func->new_size, NULL);
673                 if (!ret) {
674                         pr_err("kallsyms size lookup failed for '%s' replacement\n",
675                                func->old_name);
676                         return -ENOENT;
677                 }
678         }
679
680         return 0;
681 }
682
683 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
684 {
685         struct klp_func *func;
686         int ret;
687         const char *name;
688
689         if (!obj->funcs)
690                 return -EINVAL;
691
692         obj->patched = false;
693         obj->mod = NULL;
694
695         klp_find_object_module(obj);
696
697         name = klp_is_module(obj) ? obj->name : "vmlinux";
698         ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
699                                    &patch->kobj, "%s", name);
700         if (ret)
701                 return ret;
702
703         klp_for_each_func(obj, func) {
704                 ret = klp_init_func(obj, func);
705                 if (ret)
706                         goto free;
707         }
708
709         if (klp_is_object_loaded(obj)) {
710                 ret = klp_init_object_loaded(patch, obj);
711                 if (ret)
712                         goto free;
713         }
714
715         return 0;
716
717 free:
718         klp_free_funcs_limited(obj, func);
719         kobject_put(&obj->kobj);
720         return ret;
721 }
722
723 static int klp_init_patch(struct klp_patch *patch)
724 {
725         struct klp_object *obj;
726         int ret;
727
728         if (!patch->objs)
729                 return -EINVAL;
730
731         mutex_lock(&klp_mutex);
732
733         patch->enabled = false;
734         init_completion(&patch->finish);
735
736         ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
737                                    klp_root_kobj, "%s", patch->mod->name);
738         if (ret) {
739                 mutex_unlock(&klp_mutex);
740                 return ret;
741         }
742
743         klp_for_each_object(patch, obj) {
744                 ret = klp_init_object(patch, obj);
745                 if (ret)
746                         goto free;
747         }
748
749         list_add_tail(&patch->list, &klp_patches);
750
751         mutex_unlock(&klp_mutex);
752
753         return 0;
754
755 free:
756         klp_free_objects_limited(patch, obj);
757
758         mutex_unlock(&klp_mutex);
759
760         kobject_put(&patch->kobj);
761         wait_for_completion(&patch->finish);
762
763         return ret;
764 }
765
766 /**
767  * klp_unregister_patch() - unregisters a patch
768  * @patch:      Disabled patch to be unregistered
769  *
770  * Frees the data structures and removes the sysfs interface.
771  *
772  * Return: 0 on success, otherwise error
773  */
774 int klp_unregister_patch(struct klp_patch *patch)
775 {
776         int ret;
777
778         mutex_lock(&klp_mutex);
779
780         if (!klp_is_patch_registered(patch)) {
781                 ret = -EINVAL;
782                 goto err;
783         }
784
785         if (patch->enabled) {
786                 ret = -EBUSY;
787                 goto err;
788         }
789
790         klp_free_patch(patch);
791
792         mutex_unlock(&klp_mutex);
793
794         kobject_put(&patch->kobj);
795         wait_for_completion(&patch->finish);
796
797         return 0;
798 err:
799         mutex_unlock(&klp_mutex);
800         return ret;
801 }
802 EXPORT_SYMBOL_GPL(klp_unregister_patch);
803
804 /**
805  * klp_register_patch() - registers a patch
806  * @patch:      Patch to be registered
807  *
808  * Initializes the data structure associated with the patch and
809  * creates the sysfs interface.
810  *
811  * There is no need to take the reference on the patch module here. It is done
812  * later when the patch is enabled.
813  *
814  * Return: 0 on success, otherwise error
815  */
816 int klp_register_patch(struct klp_patch *patch)
817 {
818         if (!patch || !patch->mod)
819                 return -EINVAL;
820
821         if (!is_livepatch_module(patch->mod)) {
822                 pr_err("module %s is not marked as a livepatch module\n",
823                        patch->mod->name);
824                 return -EINVAL;
825         }
826
827         if (!klp_initialized())
828                 return -ENODEV;
829
830         /*
831          * Architectures without reliable stack traces have to set
832          * patch->immediate because there's currently no way to patch kthreads
833          * with the consistency model.
834          */
835         if (!klp_have_reliable_stack() && !patch->immediate) {
836                 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
837                 return -ENOSYS;
838         }
839
840         return klp_init_patch(patch);
841 }
842 EXPORT_SYMBOL_GPL(klp_register_patch);
843
844 int klp_module_coming(struct module *mod)
845 {
846         int ret;
847         struct klp_patch *patch;
848         struct klp_object *obj;
849
850         if (WARN_ON(mod->state != MODULE_STATE_COMING))
851                 return -EINVAL;
852
853         mutex_lock(&klp_mutex);
854         /*
855          * Each module has to know that klp_module_coming()
856          * has been called. We never know what module will
857          * get patched by a new patch.
858          */
859         mod->klp_alive = true;
860
861         list_for_each_entry(patch, &klp_patches, list) {
862                 klp_for_each_object(patch, obj) {
863                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
864                                 continue;
865
866                         obj->mod = mod;
867
868                         ret = klp_init_object_loaded(patch, obj);
869                         if (ret) {
870                                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
871                                         patch->mod->name, obj->mod->name, ret);
872                                 goto err;
873                         }
874
875                         /*
876                          * Only patch the module if the patch is enabled or is
877                          * in transition.
878                          */
879                         if (!patch->enabled && patch != klp_transition_patch)
880                                 break;
881
882                         pr_notice("applying patch '%s' to loading module '%s'\n",
883                                   patch->mod->name, obj->mod->name);
884
885                         ret = klp_pre_patch_callback(obj);
886                         if (ret) {
887                                 pr_warn("pre-patch callback failed for object '%s'\n",
888                                         obj->name);
889                                 goto err;
890                         }
891
892                         ret = klp_patch_object(obj);
893                         if (ret) {
894                                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
895                                         patch->mod->name, obj->mod->name, ret);
896
897                                 if (patch != klp_transition_patch)
898                                         klp_post_unpatch_callback(obj);
899
900                                 goto err;
901                         }
902
903                         if (patch != klp_transition_patch)
904                                 klp_post_patch_callback(obj);
905
906                         break;
907                 }
908         }
909
910         mutex_unlock(&klp_mutex);
911
912         return 0;
913
914 err:
915         /*
916          * If a patch is unsuccessfully applied, return
917          * error to the module loader.
918          */
919         pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
920                 patch->mod->name, obj->mod->name, obj->mod->name);
921         mod->klp_alive = false;
922         klp_free_object_loaded(obj);
923         mutex_unlock(&klp_mutex);
924
925         return ret;
926 }
927
928 void klp_module_going(struct module *mod)
929 {
930         struct klp_patch *patch;
931         struct klp_object *obj;
932
933         if (WARN_ON(mod->state != MODULE_STATE_GOING &&
934                     mod->state != MODULE_STATE_COMING))
935                 return;
936
937         mutex_lock(&klp_mutex);
938         /*
939          * Each module has to know that klp_module_going()
940          * has been called. We never know what module will
941          * get patched by a new patch.
942          */
943         mod->klp_alive = false;
944
945         list_for_each_entry(patch, &klp_patches, list) {
946                 klp_for_each_object(patch, obj) {
947                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
948                                 continue;
949
950                         /*
951                          * Only unpatch the module if the patch is enabled or
952                          * is in transition.
953                          */
954                         if (patch->enabled || patch == klp_transition_patch) {
955
956                                 if (patch != klp_transition_patch)
957                                         klp_pre_unpatch_callback(obj);
958
959                                 pr_notice("reverting patch '%s' on unloading module '%s'\n",
960                                           patch->mod->name, obj->mod->name);
961                                 klp_unpatch_object(obj);
962
963                                 klp_post_unpatch_callback(obj);
964                         }
965
966                         klp_free_object_loaded(obj);
967                         break;
968                 }
969         }
970
971         mutex_unlock(&klp_mutex);
972 }
973
974 static int __init klp_init(void)
975 {
976         int ret;
977
978         ret = klp_check_compiler_support();
979         if (ret) {
980                 pr_info("Your compiler is too old; turning off.\n");
981                 return -EINVAL;
982         }
983
984         klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
985         if (!klp_root_kobj)
986                 return -ENOMEM;
987
988         return 0;
989 }
990
991 module_init(klp_init);