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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * core.c - Kernel Live Patching Core
4 *
5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6 * Copyright (C) 2014 SUSE
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/module.h>
12#include <linux/kernel.h>
13#include <linux/mutex.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/kallsyms.h>
17#include <linux/livepatch.h>
18#include <linux/elf.h>
19#include <linux/moduleloader.h>
20#include <linux/completion.h>
21#include <linux/memory.h>
22#include <asm/cacheflush.h>
23#include "core.h"
24#include "patch.h"
25#include "transition.h"
26
27/*
28 * klp_mutex is a coarse lock which serializes access to klp data. All
29 * accesses to klp-related variables and structures must have mutex protection,
30 * except within the following functions which carefully avoid the need for it:
31 *
32 * - klp_ftrace_handler()
33 * - klp_update_patch_state()
34 */
35DEFINE_MUTEX(klp_mutex);
36
37/*
38 * Actively used patches: enabled or in transition. Note that replaced
39 * or disabled patches are not listed even though the related kernel
40 * module still can be loaded.
41 */
42LIST_HEAD(klp_patches);
43
44static struct kobject *klp_root_kobj;
45
46static bool klp_is_module(struct klp_object *obj)
47{
48 return obj->name;
49}
50
51/* sets obj->mod if object is not vmlinux and module is found */
52static void klp_find_object_module(struct klp_object *obj)
53{
54 struct module *mod;
55
56 if (!klp_is_module(obj))
57 return;
58
59 mutex_lock(&module_mutex);
60 /*
61 * We do not want to block removal of patched modules and therefore
62 * we do not take a reference here. The patches are removed by
63 * klp_module_going() instead.
64 */
65 mod = find_module(obj->name);
66 /*
67 * Do not mess work of klp_module_coming() and klp_module_going().
68 * Note that the patch might still be needed before klp_module_going()
69 * is called. Module functions can be called even in the GOING state
70 * until mod->exit() finishes. This is especially important for
71 * patches that modify semantic of the functions.
72 */
73 if (mod && mod->klp_alive)
74 obj->mod = mod;
75
76 mutex_unlock(&module_mutex);
77}
78
79static bool klp_initialized(void)
80{
81 return !!klp_root_kobj;
82}
83
84static struct klp_func *klp_find_func(struct klp_object *obj,
85 struct klp_func *old_func)
86{
87 struct klp_func *func;
88
89 klp_for_each_func(obj, func) {
90 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
91 (old_func->old_sympos == func->old_sympos)) {
92 return func;
93 }
94 }
95
96 return NULL;
97}
98
99static struct klp_object *klp_find_object(struct klp_patch *patch,
100 struct klp_object *old_obj)
101{
102 struct klp_object *obj;
103
104 klp_for_each_object(patch, obj) {
105 if (klp_is_module(old_obj)) {
106 if (klp_is_module(obj) &&
107 strcmp(old_obj->name, obj->name) == 0) {
108 return obj;
109 }
110 } else if (!klp_is_module(obj)) {
111 return obj;
112 }
113 }
114
115 return NULL;
116}
117
118struct klp_find_arg {
119 const char *objname;
120 const char *name;
121 unsigned long addr;
122 unsigned long count;
123 unsigned long pos;
124};
125
126static int klp_find_callback(void *data, const char *name,
127 struct module *mod, unsigned long addr)
128{
129 struct klp_find_arg *args = data;
130
131 if ((mod && !args->objname) || (!mod && args->objname))
132 return 0;
133
134 if (strcmp(args->name, name))
135 return 0;
136
137 if (args->objname && strcmp(args->objname, mod->name))
138 return 0;
139
140 args->addr = addr;
141 args->count++;
142
143 /*
144 * Finish the search when the symbol is found for the desired position
145 * or the position is not defined for a non-unique symbol.
146 */
147 if ((args->pos && (args->count == args->pos)) ||
148 (!args->pos && (args->count > 1)))
149 return 1;
150
151 return 0;
152}
153
154static int klp_find_object_symbol(const char *objname, const char *name,
155 unsigned long sympos, unsigned long *addr)
156{
157 struct klp_find_arg args = {
158 .objname = objname,
159 .name = name,
160 .addr = 0,
161 .count = 0,
162 .pos = sympos,
163 };
164
165 mutex_lock(&module_mutex);
166 if (objname)
167 module_kallsyms_on_each_symbol(klp_find_callback, &args);
168 else
169 kallsyms_on_each_symbol(klp_find_callback, &args);
170 mutex_unlock(&module_mutex);
171
172 /*
173 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
174 * otherwise ensure the symbol position count matches sympos.
175 */
176 if (args.addr == 0)
177 pr_err("symbol '%s' not found in symbol table\n", name);
178 else if (args.count > 1 && sympos == 0) {
179 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
180 name, objname);
181 } else if (sympos != args.count && sympos > 0) {
182 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
183 sympos, name, objname ? objname : "vmlinux");
184 } else {
185 *addr = args.addr;
186 return 0;
187 }
188
189 *addr = 0;
190 return -EINVAL;
191}
192
193static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
194{
195 int i, cnt, vmlinux, ret;
196 char objname[MODULE_NAME_LEN];
197 char symname[KSYM_NAME_LEN];
198 char *strtab = pmod->core_kallsyms.strtab;
199 Elf_Rela *relas;
200 Elf_Sym *sym;
201 unsigned long sympos, addr;
202
203 /*
204 * Since the field widths for objname and symname in the sscanf()
205 * call are hard-coded and correspond to MODULE_NAME_LEN and
206 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
207 * and KSYM_NAME_LEN have the values we expect them to have.
208 *
209 * Because the value of MODULE_NAME_LEN can differ among architectures,
210 * we use the smallest/strictest upper bound possible (56, based on
211 * the current definition of MODULE_NAME_LEN) to prevent overflows.
212 */
213 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
214
215 relas = (Elf_Rela *) relasec->sh_addr;
216 /* For each rela in this klp relocation section */
217 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
218 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
219 if (sym->st_shndx != SHN_LIVEPATCH) {
220 pr_err("symbol %s is not marked as a livepatch symbol\n",
221 strtab + sym->st_name);
222 return -EINVAL;
223 }
224
225 /* Format: .klp.sym.objname.symname,sympos */
226 cnt = sscanf(strtab + sym->st_name,
227 ".klp.sym.%55[^.].%127[^,],%lu",
228 objname, symname, &sympos);
229 if (cnt != 3) {
230 pr_err("symbol %s has an incorrectly formatted name\n",
231 strtab + sym->st_name);
232 return -EINVAL;
233 }
234
235 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
236 vmlinux = !strcmp(objname, "vmlinux");
237 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
238 symname, sympos, &addr);
239 if (ret)
240 return ret;
241
242 sym->st_value = addr;
243 }
244
245 return 0;
246}
247
248static int klp_write_object_relocations(struct module *pmod,
249 struct klp_object *obj)
250{
251 int i, cnt, ret = 0;
252 const char *objname, *secname;
253 char sec_objname[MODULE_NAME_LEN];
254 Elf_Shdr *sec;
255
256 if (WARN_ON(!klp_is_object_loaded(obj)))
257 return -EINVAL;
258
259 objname = klp_is_module(obj) ? obj->name : "vmlinux";
260
261 /* For each klp relocation section */
262 for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
263 sec = pmod->klp_info->sechdrs + i;
264 secname = pmod->klp_info->secstrings + sec->sh_name;
265 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
266 continue;
267
268 /*
269 * Format: .klp.rela.sec_objname.section_name
270 * See comment in klp_resolve_symbols() for an explanation
271 * of the selected field width value.
272 */
273 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
274 if (cnt != 1) {
275 pr_err("section %s has an incorrectly formatted name\n",
276 secname);
277 ret = -EINVAL;
278 break;
279 }
280
281 if (strcmp(objname, sec_objname))
282 continue;
283
284 ret = klp_resolve_symbols(sec, pmod);
285 if (ret)
286 break;
287
288 ret = apply_relocate_add(pmod->klp_info->sechdrs,
289 pmod->core_kallsyms.strtab,
290 pmod->klp_info->symndx, i, pmod);
291 if (ret)
292 break;
293 }
294
295 return ret;
296}
297
298/*
299 * Sysfs Interface
300 *
301 * /sys/kernel/livepatch
302 * /sys/kernel/livepatch/<patch>
303 * /sys/kernel/livepatch/<patch>/enabled
304 * /sys/kernel/livepatch/<patch>/transition
305 * /sys/kernel/livepatch/<patch>/force
306 * /sys/kernel/livepatch/<patch>/<object>
307 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
308 */
309static int __klp_disable_patch(struct klp_patch *patch);
310
311static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
312 const char *buf, size_t count)
313{
314 struct klp_patch *patch;
315 int ret;
316 bool enabled;
317
318 ret = kstrtobool(buf, &enabled);
319 if (ret)
320 return ret;
321
322 patch = container_of(kobj, struct klp_patch, kobj);
323
324 mutex_lock(&klp_mutex);
325
326 if (patch->enabled == enabled) {
327 /* already in requested state */
328 ret = -EINVAL;
329 goto out;
330 }
331
332 /*
333 * Allow to reverse a pending transition in both ways. It might be
334 * necessary to complete the transition without forcing and breaking
335 * the system integrity.
336 *
337 * Do not allow to re-enable a disabled patch.
338 */
339 if (patch == klp_transition_patch)
340 klp_reverse_transition();
341 else if (!enabled)
342 ret = __klp_disable_patch(patch);
343 else
344 ret = -EINVAL;
345
346out:
347 mutex_unlock(&klp_mutex);
348
349 if (ret)
350 return ret;
351 return count;
352}
353
354static ssize_t enabled_show(struct kobject *kobj,
355 struct kobj_attribute *attr, char *buf)
356{
357 struct klp_patch *patch;
358
359 patch = container_of(kobj, struct klp_patch, kobj);
360 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
361}
362
363static ssize_t transition_show(struct kobject *kobj,
364 struct kobj_attribute *attr, char *buf)
365{
366 struct klp_patch *patch;
367
368 patch = container_of(kobj, struct klp_patch, kobj);
369 return snprintf(buf, PAGE_SIZE-1, "%d\n",
370 patch == klp_transition_patch);
371}
372
373static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
374 const char *buf, size_t count)
375{
376 struct klp_patch *patch;
377 int ret;
378 bool val;
379
380 ret = kstrtobool(buf, &val);
381 if (ret)
382 return ret;
383
384 if (!val)
385 return count;
386
387 mutex_lock(&klp_mutex);
388
389 patch = container_of(kobj, struct klp_patch, kobj);
390 if (patch != klp_transition_patch) {
391 mutex_unlock(&klp_mutex);
392 return -EINVAL;
393 }
394
395 klp_force_transition();
396
397 mutex_unlock(&klp_mutex);
398
399 return count;
400}
401
402static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
403static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
404static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
405static struct attribute *klp_patch_attrs[] = {
406 &enabled_kobj_attr.attr,
407 &transition_kobj_attr.attr,
408 &force_kobj_attr.attr,
409 NULL
410};
411ATTRIBUTE_GROUPS(klp_patch);
412
413static void klp_free_object_dynamic(struct klp_object *obj)
414{
415 kfree(obj->name);
416 kfree(obj);
417}
418
419static void klp_init_func_early(struct klp_object *obj,
420 struct klp_func *func);
421static void klp_init_object_early(struct klp_patch *patch,
422 struct klp_object *obj);
423
424static struct klp_object *klp_alloc_object_dynamic(const char *name,
425 struct klp_patch *patch)
426{
427 struct klp_object *obj;
428
429 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
430 if (!obj)
431 return NULL;
432
433 if (name) {
434 obj->name = kstrdup(name, GFP_KERNEL);
435 if (!obj->name) {
436 kfree(obj);
437 return NULL;
438 }
439 }
440
441 klp_init_object_early(patch, obj);
442 obj->dynamic = true;
443
444 return obj;
445}
446
447static void klp_free_func_nop(struct klp_func *func)
448{
449 kfree(func->old_name);
450 kfree(func);
451}
452
453static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
454 struct klp_object *obj)
455{
456 struct klp_func *func;
457
458 func = kzalloc(sizeof(*func), GFP_KERNEL);
459 if (!func)
460 return NULL;
461
462 if (old_func->old_name) {
463 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
464 if (!func->old_name) {
465 kfree(func);
466 return NULL;
467 }
468 }
469
470 klp_init_func_early(obj, func);
471 /*
472 * func->new_func is same as func->old_func. These addresses are
473 * set when the object is loaded, see klp_init_object_loaded().
474 */
475 func->old_sympos = old_func->old_sympos;
476 func->nop = true;
477
478 return func;
479}
480
481static int klp_add_object_nops(struct klp_patch *patch,
482 struct klp_object *old_obj)
483{
484 struct klp_object *obj;
485 struct klp_func *func, *old_func;
486
487 obj = klp_find_object(patch, old_obj);
488
489 if (!obj) {
490 obj = klp_alloc_object_dynamic(old_obj->name, patch);
491 if (!obj)
492 return -ENOMEM;
493 }
494
495 klp_for_each_func(old_obj, old_func) {
496 func = klp_find_func(obj, old_func);
497 if (func)
498 continue;
499
500 func = klp_alloc_func_nop(old_func, obj);
501 if (!func)
502 return -ENOMEM;
503 }
504
505 return 0;
506}
507
508/*
509 * Add 'nop' functions which simply return to the caller to run
510 * the original function. The 'nop' functions are added to a
511 * patch to facilitate a 'replace' mode.
512 */
513static int klp_add_nops(struct klp_patch *patch)
514{
515 struct klp_patch *old_patch;
516 struct klp_object *old_obj;
517
518 klp_for_each_patch(old_patch) {
519 klp_for_each_object(old_patch, old_obj) {
520 int err;
521
522 err = klp_add_object_nops(patch, old_obj);
523 if (err)
524 return err;
525 }
526 }
527
528 return 0;
529}
530
531static void klp_kobj_release_patch(struct kobject *kobj)
532{
533 struct klp_patch *patch;
534
535 patch = container_of(kobj, struct klp_patch, kobj);
536 complete(&patch->finish);
537}
538
539static struct kobj_type klp_ktype_patch = {
540 .release = klp_kobj_release_patch,
541 .sysfs_ops = &kobj_sysfs_ops,
542 .default_groups = klp_patch_groups,
543};
544
545static void klp_kobj_release_object(struct kobject *kobj)
546{
547 struct klp_object *obj;
548
549 obj = container_of(kobj, struct klp_object, kobj);
550
551 if (obj->dynamic)
552 klp_free_object_dynamic(obj);
553}
554
555static struct kobj_type klp_ktype_object = {
556 .release = klp_kobj_release_object,
557 .sysfs_ops = &kobj_sysfs_ops,
558};
559
560static void klp_kobj_release_func(struct kobject *kobj)
561{
562 struct klp_func *func;
563
564 func = container_of(kobj, struct klp_func, kobj);
565
566 if (func->nop)
567 klp_free_func_nop(func);
568}
569
570static struct kobj_type klp_ktype_func = {
571 .release = klp_kobj_release_func,
572 .sysfs_ops = &kobj_sysfs_ops,
573};
574
575static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
576{
577 struct klp_func *func, *tmp_func;
578
579 klp_for_each_func_safe(obj, func, tmp_func) {
580 if (nops_only && !func->nop)
581 continue;
582
583 list_del(&func->node);
584 kobject_put(&func->kobj);
585 }
586}
587
588/* Clean up when a patched object is unloaded */
589static void klp_free_object_loaded(struct klp_object *obj)
590{
591 struct klp_func *func;
592
593 obj->mod = NULL;
594
595 klp_for_each_func(obj, func) {
596 func->old_func = NULL;
597
598 if (func->nop)
599 func->new_func = NULL;
600 }
601}
602
603static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
604{
605 struct klp_object *obj, *tmp_obj;
606
607 klp_for_each_object_safe(patch, obj, tmp_obj) {
608 __klp_free_funcs(obj, nops_only);
609
610 if (nops_only && !obj->dynamic)
611 continue;
612
613 list_del(&obj->node);
614 kobject_put(&obj->kobj);
615 }
616}
617
618static void klp_free_objects(struct klp_patch *patch)
619{
620 __klp_free_objects(patch, false);
621}
622
623static void klp_free_objects_dynamic(struct klp_patch *patch)
624{
625 __klp_free_objects(patch, true);
626}
627
628/*
629 * This function implements the free operations that can be called safely
630 * under klp_mutex.
631 *
632 * The operation must be completed by calling klp_free_patch_finish()
633 * outside klp_mutex.
634 */
635void klp_free_patch_start(struct klp_patch *patch)
636{
637 if (!list_empty(&patch->list))
638 list_del(&patch->list);
639
640 klp_free_objects(patch);
641}
642
643/*
644 * This function implements the free part that must be called outside
645 * klp_mutex.
646 *
647 * It must be called after klp_free_patch_start(). And it has to be
648 * the last function accessing the livepatch structures when the patch
649 * gets disabled.
650 */
651static void klp_free_patch_finish(struct klp_patch *patch)
652{
653 /*
654 * Avoid deadlock with enabled_store() sysfs callback by
655 * calling this outside klp_mutex. It is safe because
656 * this is called when the patch gets disabled and it
657 * cannot get enabled again.
658 */
659 kobject_put(&patch->kobj);
660 wait_for_completion(&patch->finish);
661
662 /* Put the module after the last access to struct klp_patch. */
663 if (!patch->forced)
664 module_put(patch->mod);
665}
666
667/*
668 * The livepatch might be freed from sysfs interface created by the patch.
669 * This work allows to wait until the interface is destroyed in a separate
670 * context.
671 */
672static void klp_free_patch_work_fn(struct work_struct *work)
673{
674 struct klp_patch *patch =
675 container_of(work, struct klp_patch, free_work);
676
677 klp_free_patch_finish(patch);
678}
679
680static int klp_init_func(struct klp_object *obj, struct klp_func *func)
681{
682 if (!func->old_name)
683 return -EINVAL;
684
685 /*
686 * NOPs get the address later. The patched module must be loaded,
687 * see klp_init_object_loaded().
688 */
689 if (!func->new_func && !func->nop)
690 return -EINVAL;
691
692 if (strlen(func->old_name) >= KSYM_NAME_LEN)
693 return -EINVAL;
694
695 INIT_LIST_HEAD(&func->stack_node);
696 func->patched = false;
697 func->transition = false;
698
699 /* The format for the sysfs directory is <function,sympos> where sympos
700 * is the nth occurrence of this symbol in kallsyms for the patched
701 * object. If the user selects 0 for old_sympos, then 1 will be used
702 * since a unique symbol will be the first occurrence.
703 */
704 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
705 func->old_name,
706 func->old_sympos ? func->old_sympos : 1);
707}
708
709/* Arches may override this to finish any remaining arch-specific tasks */
710void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
711 struct klp_object *obj)
712{
713}
714
715/* parts of the initialization that is done only when the object is loaded */
716static int klp_init_object_loaded(struct klp_patch *patch,
717 struct klp_object *obj)
718{
719 struct klp_func *func;
720 int ret;
721
722 mutex_lock(&text_mutex);
723
724 module_disable_ro(patch->mod);
725 ret = klp_write_object_relocations(patch->mod, obj);
726 if (ret) {
727 module_enable_ro(patch->mod, true);
728 mutex_unlock(&text_mutex);
729 return ret;
730 }
731
732 arch_klp_init_object_loaded(patch, obj);
733 module_enable_ro(patch->mod, true);
734
735 mutex_unlock(&text_mutex);
736
737 klp_for_each_func(obj, func) {
738 ret = klp_find_object_symbol(obj->name, func->old_name,
739 func->old_sympos,
740 (unsigned long *)&func->old_func);
741 if (ret)
742 return ret;
743
744 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
745 &func->old_size, NULL);
746 if (!ret) {
747 pr_err("kallsyms size lookup failed for '%s'\n",
748 func->old_name);
749 return -ENOENT;
750 }
751
752 if (func->nop)
753 func->new_func = func->old_func;
754
755 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
756 &func->new_size, NULL);
757 if (!ret) {
758 pr_err("kallsyms size lookup failed for '%s' replacement\n",
759 func->old_name);
760 return -ENOENT;
761 }
762 }
763
764 return 0;
765}
766
767static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
768{
769 struct klp_func *func;
770 int ret;
771 const char *name;
772
773 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
774 return -EINVAL;
775
776 obj->patched = false;
777 obj->mod = NULL;
778
779 klp_find_object_module(obj);
780
781 name = klp_is_module(obj) ? obj->name : "vmlinux";
782 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
783 if (ret)
784 return ret;
785
786 klp_for_each_func(obj, func) {
787 ret = klp_init_func(obj, func);
788 if (ret)
789 return ret;
790 }
791
792 if (klp_is_object_loaded(obj))
793 ret = klp_init_object_loaded(patch, obj);
794
795 return ret;
796}
797
798static void klp_init_func_early(struct klp_object *obj,
799 struct klp_func *func)
800{
801 kobject_init(&func->kobj, &klp_ktype_func);
802 list_add_tail(&func->node, &obj->func_list);
803}
804
805static void klp_init_object_early(struct klp_patch *patch,
806 struct klp_object *obj)
807{
808 INIT_LIST_HEAD(&obj->func_list);
809 kobject_init(&obj->kobj, &klp_ktype_object);
810 list_add_tail(&obj->node, &patch->obj_list);
811}
812
813static int klp_init_patch_early(struct klp_patch *patch)
814{
815 struct klp_object *obj;
816 struct klp_func *func;
817
818 if (!patch->objs)
819 return -EINVAL;
820
821 INIT_LIST_HEAD(&patch->list);
822 INIT_LIST_HEAD(&patch->obj_list);
823 kobject_init(&patch->kobj, &klp_ktype_patch);
824 patch->enabled = false;
825 patch->forced = false;
826 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
827 init_completion(&patch->finish);
828
829 klp_for_each_object_static(patch, obj) {
830 if (!obj->funcs)
831 return -EINVAL;
832
833 klp_init_object_early(patch, obj);
834
835 klp_for_each_func_static(obj, func) {
836 klp_init_func_early(obj, func);
837 }
838 }
839
840 if (!try_module_get(patch->mod))
841 return -ENODEV;
842
843 return 0;
844}
845
846static int klp_init_patch(struct klp_patch *patch)
847{
848 struct klp_object *obj;
849 int ret;
850
851 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
852 if (ret)
853 return ret;
854
855 if (patch->replace) {
856 ret = klp_add_nops(patch);
857 if (ret)
858 return ret;
859 }
860
861 klp_for_each_object(patch, obj) {
862 ret = klp_init_object(patch, obj);
863 if (ret)
864 return ret;
865 }
866
867 list_add_tail(&patch->list, &klp_patches);
868
869 return 0;
870}
871
872static int __klp_disable_patch(struct klp_patch *patch)
873{
874 struct klp_object *obj;
875
876 if (WARN_ON(!patch->enabled))
877 return -EINVAL;
878
879 if (klp_transition_patch)
880 return -EBUSY;
881
882 klp_init_transition(patch, KLP_UNPATCHED);
883
884 klp_for_each_object(patch, obj)
885 if (obj->patched)
886 klp_pre_unpatch_callback(obj);
887
888 /*
889 * Enforce the order of the func->transition writes in
890 * klp_init_transition() and the TIF_PATCH_PENDING writes in
891 * klp_start_transition(). In the rare case where klp_ftrace_handler()
892 * is called shortly after klp_update_patch_state() switches the task,
893 * this ensures the handler sees that func->transition is set.
894 */
895 smp_wmb();
896
897 klp_start_transition();
898 patch->enabled = false;
899 klp_try_complete_transition();
900
901 return 0;
902}
903
904static int __klp_enable_patch(struct klp_patch *patch)
905{
906 struct klp_object *obj;
907 int ret;
908
909 if (klp_transition_patch)
910 return -EBUSY;
911
912 if (WARN_ON(patch->enabled))
913 return -EINVAL;
914
915 pr_notice("enabling patch '%s'\n", patch->mod->name);
916
917 klp_init_transition(patch, KLP_PATCHED);
918
919 /*
920 * Enforce the order of the func->transition writes in
921 * klp_init_transition() and the ops->func_stack writes in
922 * klp_patch_object(), so that klp_ftrace_handler() will see the
923 * func->transition updates before the handler is registered and the
924 * new funcs become visible to the handler.
925 */
926 smp_wmb();
927
928 klp_for_each_object(patch, obj) {
929 if (!klp_is_object_loaded(obj))
930 continue;
931
932 ret = klp_pre_patch_callback(obj);
933 if (ret) {
934 pr_warn("pre-patch callback failed for object '%s'\n",
935 klp_is_module(obj) ? obj->name : "vmlinux");
936 goto err;
937 }
938
939 ret = klp_patch_object(obj);
940 if (ret) {
941 pr_warn("failed to patch object '%s'\n",
942 klp_is_module(obj) ? obj->name : "vmlinux");
943 goto err;
944 }
945 }
946
947 klp_start_transition();
948 patch->enabled = true;
949 klp_try_complete_transition();
950
951 return 0;
952err:
953 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
954
955 klp_cancel_transition();
956 return ret;
957}
958
959/**
960 * klp_enable_patch() - enable the livepatch
961 * @patch: patch to be enabled
962 *
963 * Initializes the data structure associated with the patch, creates the sysfs
964 * interface, performs the needed symbol lookups and code relocations,
965 * registers the patched functions with ftrace.
966 *
967 * This function is supposed to be called from the livepatch module_init()
968 * callback.
969 *
970 * Return: 0 on success, otherwise error
971 */
972int klp_enable_patch(struct klp_patch *patch)
973{
974 int ret;
975
976 if (!patch || !patch->mod)
977 return -EINVAL;
978
979 if (!is_livepatch_module(patch->mod)) {
980 pr_err("module %s is not marked as a livepatch module\n",
981 patch->mod->name);
982 return -EINVAL;
983 }
984
985 if (!klp_initialized())
986 return -ENODEV;
987
988 if (!klp_have_reliable_stack()) {
989 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
990 pr_warn("The livepatch transition may never complete.\n");
991 }
992
993 mutex_lock(&klp_mutex);
994
995 ret = klp_init_patch_early(patch);
996 if (ret) {
997 mutex_unlock(&klp_mutex);
998 return ret;
999 }
1000
1001 ret = klp_init_patch(patch);
1002 if (ret)
1003 goto err;
1004
1005 ret = __klp_enable_patch(patch);
1006 if (ret)
1007 goto err;
1008
1009 mutex_unlock(&klp_mutex);
1010
1011 return 0;
1012
1013err:
1014 klp_free_patch_start(patch);
1015
1016 mutex_unlock(&klp_mutex);
1017
1018 klp_free_patch_finish(patch);
1019
1020 return ret;
1021}
1022EXPORT_SYMBOL_GPL(klp_enable_patch);
1023
1024/*
1025 * This function removes replaced patches.
1026 *
1027 * We could be pretty aggressive here. It is called in the situation where
1028 * these structures are no longer accessible. All functions are redirected
1029 * by the klp_transition_patch. They use either a new code or they are in
1030 * the original code because of the special nop function patches.
1031 *
1032 * The only exception is when the transition was forced. In this case,
1033 * klp_ftrace_handler() might still see the replaced patch on the stack.
1034 * Fortunately, it is carefully designed to work with removed functions
1035 * thanks to RCU. We only have to keep the patches on the system. Also
1036 * this is handled transparently by patch->module_put.
1037 */
1038void klp_discard_replaced_patches(struct klp_patch *new_patch)
1039{
1040 struct klp_patch *old_patch, *tmp_patch;
1041
1042 klp_for_each_patch_safe(old_patch, tmp_patch) {
1043 if (old_patch == new_patch)
1044 return;
1045
1046 old_patch->enabled = false;
1047 klp_unpatch_objects(old_patch);
1048 klp_free_patch_start(old_patch);
1049 schedule_work(&old_patch->free_work);
1050 }
1051}
1052
1053/*
1054 * This function removes the dynamically allocated 'nop' functions.
1055 *
1056 * We could be pretty aggressive. NOPs do not change the existing
1057 * behavior except for adding unnecessary delay by the ftrace handler.
1058 *
1059 * It is safe even when the transition was forced. The ftrace handler
1060 * will see a valid ops->func_stack entry thanks to RCU.
1061 *
1062 * We could even free the NOPs structures. They must be the last entry
1063 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1064 * It does the same as klp_synchronize_transition() to make sure that
1065 * nobody is inside the ftrace handler once the operation finishes.
1066 *
1067 * IMPORTANT: It must be called right after removing the replaced patches!
1068 */
1069void klp_discard_nops(struct klp_patch *new_patch)
1070{
1071 klp_unpatch_objects_dynamic(klp_transition_patch);
1072 klp_free_objects_dynamic(klp_transition_patch);
1073}
1074
1075/*
1076 * Remove parts of patches that touch a given kernel module. The list of
1077 * patches processed might be limited. When limit is NULL, all patches
1078 * will be handled.
1079 */
1080static void klp_cleanup_module_patches_limited(struct module *mod,
1081 struct klp_patch *limit)
1082{
1083 struct klp_patch *patch;
1084 struct klp_object *obj;
1085
1086 klp_for_each_patch(patch) {
1087 if (patch == limit)
1088 break;
1089
1090 klp_for_each_object(patch, obj) {
1091 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1092 continue;
1093
1094 if (patch != klp_transition_patch)
1095 klp_pre_unpatch_callback(obj);
1096
1097 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1098 patch->mod->name, obj->mod->name);
1099 klp_unpatch_object(obj);
1100
1101 klp_post_unpatch_callback(obj);
1102
1103 klp_free_object_loaded(obj);
1104 break;
1105 }
1106 }
1107}
1108
1109int klp_module_coming(struct module *mod)
1110{
1111 int ret;
1112 struct klp_patch *patch;
1113 struct klp_object *obj;
1114
1115 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1116 return -EINVAL;
1117
1118 mutex_lock(&klp_mutex);
1119 /*
1120 * Each module has to know that klp_module_coming()
1121 * has been called. We never know what module will
1122 * get patched by a new patch.
1123 */
1124 mod->klp_alive = true;
1125
1126 klp_for_each_patch(patch) {
1127 klp_for_each_object(patch, obj) {
1128 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1129 continue;
1130
1131 obj->mod = mod;
1132
1133 ret = klp_init_object_loaded(patch, obj);
1134 if (ret) {
1135 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1136 patch->mod->name, obj->mod->name, ret);
1137 goto err;
1138 }
1139
1140 pr_notice("applying patch '%s' to loading module '%s'\n",
1141 patch->mod->name, obj->mod->name);
1142
1143 ret = klp_pre_patch_callback(obj);
1144 if (ret) {
1145 pr_warn("pre-patch callback failed for object '%s'\n",
1146 obj->name);
1147 goto err;
1148 }
1149
1150 ret = klp_patch_object(obj);
1151 if (ret) {
1152 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1153 patch->mod->name, obj->mod->name, ret);
1154
1155 klp_post_unpatch_callback(obj);
1156 goto err;
1157 }
1158
1159 if (patch != klp_transition_patch)
1160 klp_post_patch_callback(obj);
1161
1162 break;
1163 }
1164 }
1165
1166 mutex_unlock(&klp_mutex);
1167
1168 return 0;
1169
1170err:
1171 /*
1172 * If a patch is unsuccessfully applied, return
1173 * error to the module loader.
1174 */
1175 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1176 patch->mod->name, obj->mod->name, obj->mod->name);
1177 mod->klp_alive = false;
1178 obj->mod = NULL;
1179 klp_cleanup_module_patches_limited(mod, patch);
1180 mutex_unlock(&klp_mutex);
1181
1182 return ret;
1183}
1184
1185void klp_module_going(struct module *mod)
1186{
1187 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1188 mod->state != MODULE_STATE_COMING))
1189 return;
1190
1191 mutex_lock(&klp_mutex);
1192 /*
1193 * Each module has to know that klp_module_going()
1194 * has been called. We never know what module will
1195 * get patched by a new patch.
1196 */
1197 mod->klp_alive = false;
1198
1199 klp_cleanup_module_patches_limited(mod, NULL);
1200
1201 mutex_unlock(&klp_mutex);
1202}
1203
1204static int __init klp_init(void)
1205{
1206 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1207 if (!klp_root_kobj)
1208 return -ENOMEM;
1209
1210 return 0;
1211}
1212
1213module_init(klp_init);
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * core.c - Kernel Live Patching Core
4 *
5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6 * Copyright (C) 2014 SUSE
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/module.h>
12#include <linux/kernel.h>
13#include <linux/mutex.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/kallsyms.h>
17#include <linux/livepatch.h>
18#include <linux/elf.h>
19#include <linux/moduleloader.h>
20#include <linux/completion.h>
21#include <linux/memory.h>
22#include <linux/rcupdate.h>
23#include <asm/cacheflush.h>
24#include "core.h"
25#include "patch.h"
26#include "state.h"
27#include "transition.h"
28
29/*
30 * klp_mutex is a coarse lock which serializes access to klp data. All
31 * accesses to klp-related variables and structures must have mutex protection,
32 * except within the following functions which carefully avoid the need for it:
33 *
34 * - klp_ftrace_handler()
35 * - klp_update_patch_state()
36 * - __klp_sched_try_switch()
37 */
38DEFINE_MUTEX(klp_mutex);
39
40/*
41 * Actively used patches: enabled or in transition. Note that replaced
42 * or disabled patches are not listed even though the related kernel
43 * module still can be loaded.
44 */
45LIST_HEAD(klp_patches);
46
47static struct kobject *klp_root_kobj;
48
49static bool klp_is_module(struct klp_object *obj)
50{
51 return obj->name;
52}
53
54/* sets obj->mod if object is not vmlinux and module is found */
55static void klp_find_object_module(struct klp_object *obj)
56{
57 struct module *mod;
58
59 if (!klp_is_module(obj))
60 return;
61
62 rcu_read_lock_sched();
63 /*
64 * We do not want to block removal of patched modules and therefore
65 * we do not take a reference here. The patches are removed by
66 * klp_module_going() instead.
67 */
68 mod = find_module(obj->name);
69 /*
70 * Do not mess work of klp_module_coming() and klp_module_going().
71 * Note that the patch might still be needed before klp_module_going()
72 * is called. Module functions can be called even in the GOING state
73 * until mod->exit() finishes. This is especially important for
74 * patches that modify semantic of the functions.
75 */
76 if (mod && mod->klp_alive)
77 obj->mod = mod;
78
79 rcu_read_unlock_sched();
80}
81
82static bool klp_initialized(void)
83{
84 return !!klp_root_kobj;
85}
86
87static struct klp_func *klp_find_func(struct klp_object *obj,
88 struct klp_func *old_func)
89{
90 struct klp_func *func;
91
92 klp_for_each_func(obj, func) {
93 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
94 (old_func->old_sympos == func->old_sympos)) {
95 return func;
96 }
97 }
98
99 return NULL;
100}
101
102static struct klp_object *klp_find_object(struct klp_patch *patch,
103 struct klp_object *old_obj)
104{
105 struct klp_object *obj;
106
107 klp_for_each_object(patch, obj) {
108 if (klp_is_module(old_obj)) {
109 if (klp_is_module(obj) &&
110 strcmp(old_obj->name, obj->name) == 0) {
111 return obj;
112 }
113 } else if (!klp_is_module(obj)) {
114 return obj;
115 }
116 }
117
118 return NULL;
119}
120
121struct klp_find_arg {
122 const char *name;
123 unsigned long addr;
124 unsigned long count;
125 unsigned long pos;
126};
127
128static int klp_match_callback(void *data, unsigned long addr)
129{
130 struct klp_find_arg *args = data;
131
132 args->addr = addr;
133 args->count++;
134
135 /*
136 * Finish the search when the symbol is found for the desired position
137 * or the position is not defined for a non-unique symbol.
138 */
139 if ((args->pos && (args->count == args->pos)) ||
140 (!args->pos && (args->count > 1)))
141 return 1;
142
143 return 0;
144}
145
146static int klp_find_callback(void *data, const char *name, unsigned long addr)
147{
148 struct klp_find_arg *args = data;
149
150 if (strcmp(args->name, name))
151 return 0;
152
153 return klp_match_callback(data, addr);
154}
155
156static int klp_find_object_symbol(const char *objname, const char *name,
157 unsigned long sympos, unsigned long *addr)
158{
159 struct klp_find_arg args = {
160 .name = name,
161 .addr = 0,
162 .count = 0,
163 .pos = sympos,
164 };
165
166 if (objname)
167 module_kallsyms_on_each_symbol(objname, klp_find_callback, &args);
168 else
169 kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
170
171 /*
172 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
173 * otherwise ensure the symbol position count matches sympos.
174 */
175 if (args.addr == 0)
176 pr_err("symbol '%s' not found in symbol table\n", name);
177 else if (args.count > 1 && sympos == 0) {
178 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
179 name, objname);
180 } else if (sympos != args.count && sympos > 0) {
181 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
182 sympos, name, objname ? objname : "vmlinux");
183 } else {
184 *addr = args.addr;
185 return 0;
186 }
187
188 *addr = 0;
189 return -EINVAL;
190}
191
192static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
193 unsigned int symndx, Elf_Shdr *relasec,
194 const char *sec_objname)
195{
196 int i, cnt, ret;
197 char sym_objname[MODULE_NAME_LEN];
198 char sym_name[KSYM_NAME_LEN];
199 Elf_Rela *relas;
200 Elf_Sym *sym;
201 unsigned long sympos, addr;
202 bool sym_vmlinux;
203 bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
204
205 /*
206 * Since the field widths for sym_objname and sym_name in the sscanf()
207 * call are hard-coded and correspond to MODULE_NAME_LEN and
208 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
209 * and KSYM_NAME_LEN have the values we expect them to have.
210 *
211 * Because the value of MODULE_NAME_LEN can differ among architectures,
212 * we use the smallest/strictest upper bound possible (56, based on
213 * the current definition of MODULE_NAME_LEN) to prevent overflows.
214 */
215 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
216
217 relas = (Elf_Rela *) relasec->sh_addr;
218 /* For each rela in this klp relocation section */
219 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
220 sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
221 if (sym->st_shndx != SHN_LIVEPATCH) {
222 pr_err("symbol %s is not marked as a livepatch symbol\n",
223 strtab + sym->st_name);
224 return -EINVAL;
225 }
226
227 /* Format: .klp.sym.sym_objname.sym_name,sympos */
228 cnt = sscanf(strtab + sym->st_name,
229 ".klp.sym.%55[^.].%511[^,],%lu",
230 sym_objname, sym_name, &sympos);
231 if (cnt != 3) {
232 pr_err("symbol %s has an incorrectly formatted name\n",
233 strtab + sym->st_name);
234 return -EINVAL;
235 }
236
237 sym_vmlinux = !strcmp(sym_objname, "vmlinux");
238
239 /*
240 * Prevent module-specific KLP rela sections from referencing
241 * vmlinux symbols. This helps prevent ordering issues with
242 * module special section initializations. Presumably such
243 * symbols are exported and normal relas can be used instead.
244 */
245 if (!sec_vmlinux && sym_vmlinux) {
246 pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section\n",
247 sym_name);
248 return -EINVAL;
249 }
250
251 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
252 ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
253 sym_name, sympos, &addr);
254 if (ret)
255 return ret;
256
257 sym->st_value = addr;
258 }
259
260 return 0;
261}
262
263void __weak clear_relocate_add(Elf_Shdr *sechdrs,
264 const char *strtab,
265 unsigned int symindex,
266 unsigned int relsec,
267 struct module *me)
268{
269}
270
271/*
272 * At a high-level, there are two types of klp relocation sections: those which
273 * reference symbols which live in vmlinux; and those which reference symbols
274 * which live in other modules. This function is called for both types:
275 *
276 * 1) When a klp module itself loads, the module code calls this function to
277 * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
278 * These relocations are written to the klp module text to allow the patched
279 * code/data to reference unexported vmlinux symbols. They're written as
280 * early as possible to ensure that other module init code (.e.g.,
281 * jump_label_apply_nops) can access any unexported vmlinux symbols which
282 * might be referenced by the klp module's special sections.
283 *
284 * 2) When a to-be-patched module loads -- or is already loaded when a
285 * corresponding klp module loads -- klp code calls this function to write
286 * module-specific klp relocations (.klp.rela.{module}.* sections). These
287 * are written to the klp module text to allow the patched code/data to
288 * reference symbols which live in the to-be-patched module or one of its
289 * module dependencies. Exported symbols are supported, in addition to
290 * unexported symbols, in order to enable late module patching, which allows
291 * the to-be-patched module to be loaded and patched sometime *after* the
292 * klp module is loaded.
293 */
294static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
295 const char *shstrtab, const char *strtab,
296 unsigned int symndx, unsigned int secndx,
297 const char *objname, bool apply)
298{
299 int cnt, ret;
300 char sec_objname[MODULE_NAME_LEN];
301 Elf_Shdr *sec = sechdrs + secndx;
302
303 /*
304 * Format: .klp.rela.sec_objname.section_name
305 * See comment in klp_resolve_symbols() for an explanation
306 * of the selected field width value.
307 */
308 cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
309 sec_objname);
310 if (cnt != 1) {
311 pr_err("section %s has an incorrectly formatted name\n",
312 shstrtab + sec->sh_name);
313 return -EINVAL;
314 }
315
316 if (strcmp(objname ? objname : "vmlinux", sec_objname))
317 return 0;
318
319 if (apply) {
320 ret = klp_resolve_symbols(sechdrs, strtab, symndx,
321 sec, sec_objname);
322 if (ret)
323 return ret;
324
325 return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
326 }
327
328 clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
329 return 0;
330}
331
332int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
333 const char *shstrtab, const char *strtab,
334 unsigned int symndx, unsigned int secndx,
335 const char *objname)
336{
337 return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx,
338 secndx, objname, true);
339}
340
341/*
342 * Sysfs Interface
343 *
344 * /sys/kernel/livepatch
345 * /sys/kernel/livepatch/<patch>
346 * /sys/kernel/livepatch/<patch>/enabled
347 * /sys/kernel/livepatch/<patch>/transition
348 * /sys/kernel/livepatch/<patch>/force
349 * /sys/kernel/livepatch/<patch>/<object>
350 * /sys/kernel/livepatch/<patch>/<object>/patched
351 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
352 */
353static int __klp_disable_patch(struct klp_patch *patch);
354
355static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
356 const char *buf, size_t count)
357{
358 struct klp_patch *patch;
359 int ret;
360 bool enabled;
361
362 ret = kstrtobool(buf, &enabled);
363 if (ret)
364 return ret;
365
366 patch = container_of(kobj, struct klp_patch, kobj);
367
368 mutex_lock(&klp_mutex);
369
370 if (patch->enabled == enabled) {
371 /* already in requested state */
372 ret = -EINVAL;
373 goto out;
374 }
375
376 /*
377 * Allow to reverse a pending transition in both ways. It might be
378 * necessary to complete the transition without forcing and breaking
379 * the system integrity.
380 *
381 * Do not allow to re-enable a disabled patch.
382 */
383 if (patch == klp_transition_patch)
384 klp_reverse_transition();
385 else if (!enabled)
386 ret = __klp_disable_patch(patch);
387 else
388 ret = -EINVAL;
389
390out:
391 mutex_unlock(&klp_mutex);
392
393 if (ret)
394 return ret;
395 return count;
396}
397
398static ssize_t enabled_show(struct kobject *kobj,
399 struct kobj_attribute *attr, char *buf)
400{
401 struct klp_patch *patch;
402
403 patch = container_of(kobj, struct klp_patch, kobj);
404 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
405}
406
407static ssize_t transition_show(struct kobject *kobj,
408 struct kobj_attribute *attr, char *buf)
409{
410 struct klp_patch *patch;
411
412 patch = container_of(kobj, struct klp_patch, kobj);
413 return snprintf(buf, PAGE_SIZE-1, "%d\n",
414 patch == klp_transition_patch);
415}
416
417static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
418 const char *buf, size_t count)
419{
420 struct klp_patch *patch;
421 int ret;
422 bool val;
423
424 ret = kstrtobool(buf, &val);
425 if (ret)
426 return ret;
427
428 if (!val)
429 return count;
430
431 mutex_lock(&klp_mutex);
432
433 patch = container_of(kobj, struct klp_patch, kobj);
434 if (patch != klp_transition_patch) {
435 mutex_unlock(&klp_mutex);
436 return -EINVAL;
437 }
438
439 klp_force_transition();
440
441 mutex_unlock(&klp_mutex);
442
443 return count;
444}
445
446static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
447static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
448static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
449static struct attribute *klp_patch_attrs[] = {
450 &enabled_kobj_attr.attr,
451 &transition_kobj_attr.attr,
452 &force_kobj_attr.attr,
453 NULL
454};
455ATTRIBUTE_GROUPS(klp_patch);
456
457static ssize_t patched_show(struct kobject *kobj,
458 struct kobj_attribute *attr, char *buf)
459{
460 struct klp_object *obj;
461
462 obj = container_of(kobj, struct klp_object, kobj);
463 return sysfs_emit(buf, "%d\n", obj->patched);
464}
465
466static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
467static struct attribute *klp_object_attrs[] = {
468 &patched_kobj_attr.attr,
469 NULL,
470};
471ATTRIBUTE_GROUPS(klp_object);
472
473static void klp_free_object_dynamic(struct klp_object *obj)
474{
475 kfree(obj->name);
476 kfree(obj);
477}
478
479static void klp_init_func_early(struct klp_object *obj,
480 struct klp_func *func);
481static void klp_init_object_early(struct klp_patch *patch,
482 struct klp_object *obj);
483
484static struct klp_object *klp_alloc_object_dynamic(const char *name,
485 struct klp_patch *patch)
486{
487 struct klp_object *obj;
488
489 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
490 if (!obj)
491 return NULL;
492
493 if (name) {
494 obj->name = kstrdup(name, GFP_KERNEL);
495 if (!obj->name) {
496 kfree(obj);
497 return NULL;
498 }
499 }
500
501 klp_init_object_early(patch, obj);
502 obj->dynamic = true;
503
504 return obj;
505}
506
507static void klp_free_func_nop(struct klp_func *func)
508{
509 kfree(func->old_name);
510 kfree(func);
511}
512
513static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
514 struct klp_object *obj)
515{
516 struct klp_func *func;
517
518 func = kzalloc(sizeof(*func), GFP_KERNEL);
519 if (!func)
520 return NULL;
521
522 if (old_func->old_name) {
523 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
524 if (!func->old_name) {
525 kfree(func);
526 return NULL;
527 }
528 }
529
530 klp_init_func_early(obj, func);
531 /*
532 * func->new_func is same as func->old_func. These addresses are
533 * set when the object is loaded, see klp_init_object_loaded().
534 */
535 func->old_sympos = old_func->old_sympos;
536 func->nop = true;
537
538 return func;
539}
540
541static int klp_add_object_nops(struct klp_patch *patch,
542 struct klp_object *old_obj)
543{
544 struct klp_object *obj;
545 struct klp_func *func, *old_func;
546
547 obj = klp_find_object(patch, old_obj);
548
549 if (!obj) {
550 obj = klp_alloc_object_dynamic(old_obj->name, patch);
551 if (!obj)
552 return -ENOMEM;
553 }
554
555 klp_for_each_func(old_obj, old_func) {
556 func = klp_find_func(obj, old_func);
557 if (func)
558 continue;
559
560 func = klp_alloc_func_nop(old_func, obj);
561 if (!func)
562 return -ENOMEM;
563 }
564
565 return 0;
566}
567
568/*
569 * Add 'nop' functions which simply return to the caller to run
570 * the original function. The 'nop' functions are added to a
571 * patch to facilitate a 'replace' mode.
572 */
573static int klp_add_nops(struct klp_patch *patch)
574{
575 struct klp_patch *old_patch;
576 struct klp_object *old_obj;
577
578 klp_for_each_patch(old_patch) {
579 klp_for_each_object(old_patch, old_obj) {
580 int err;
581
582 err = klp_add_object_nops(patch, old_obj);
583 if (err)
584 return err;
585 }
586 }
587
588 return 0;
589}
590
591static void klp_kobj_release_patch(struct kobject *kobj)
592{
593 struct klp_patch *patch;
594
595 patch = container_of(kobj, struct klp_patch, kobj);
596 complete(&patch->finish);
597}
598
599static const struct kobj_type klp_ktype_patch = {
600 .release = klp_kobj_release_patch,
601 .sysfs_ops = &kobj_sysfs_ops,
602 .default_groups = klp_patch_groups,
603};
604
605static void klp_kobj_release_object(struct kobject *kobj)
606{
607 struct klp_object *obj;
608
609 obj = container_of(kobj, struct klp_object, kobj);
610
611 if (obj->dynamic)
612 klp_free_object_dynamic(obj);
613}
614
615static const struct kobj_type klp_ktype_object = {
616 .release = klp_kobj_release_object,
617 .sysfs_ops = &kobj_sysfs_ops,
618 .default_groups = klp_object_groups,
619};
620
621static void klp_kobj_release_func(struct kobject *kobj)
622{
623 struct klp_func *func;
624
625 func = container_of(kobj, struct klp_func, kobj);
626
627 if (func->nop)
628 klp_free_func_nop(func);
629}
630
631static const struct kobj_type klp_ktype_func = {
632 .release = klp_kobj_release_func,
633 .sysfs_ops = &kobj_sysfs_ops,
634};
635
636static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
637{
638 struct klp_func *func, *tmp_func;
639
640 klp_for_each_func_safe(obj, func, tmp_func) {
641 if (nops_only && !func->nop)
642 continue;
643
644 list_del(&func->node);
645 kobject_put(&func->kobj);
646 }
647}
648
649/* Clean up when a patched object is unloaded */
650static void klp_free_object_loaded(struct klp_object *obj)
651{
652 struct klp_func *func;
653
654 obj->mod = NULL;
655
656 klp_for_each_func(obj, func) {
657 func->old_func = NULL;
658
659 if (func->nop)
660 func->new_func = NULL;
661 }
662}
663
664static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
665{
666 struct klp_object *obj, *tmp_obj;
667
668 klp_for_each_object_safe(patch, obj, tmp_obj) {
669 __klp_free_funcs(obj, nops_only);
670
671 if (nops_only && !obj->dynamic)
672 continue;
673
674 list_del(&obj->node);
675 kobject_put(&obj->kobj);
676 }
677}
678
679static void klp_free_objects(struct klp_patch *patch)
680{
681 __klp_free_objects(patch, false);
682}
683
684static void klp_free_objects_dynamic(struct klp_patch *patch)
685{
686 __klp_free_objects(patch, true);
687}
688
689/*
690 * This function implements the free operations that can be called safely
691 * under klp_mutex.
692 *
693 * The operation must be completed by calling klp_free_patch_finish()
694 * outside klp_mutex.
695 */
696static void klp_free_patch_start(struct klp_patch *patch)
697{
698 if (!list_empty(&patch->list))
699 list_del(&patch->list);
700
701 klp_free_objects(patch);
702}
703
704/*
705 * This function implements the free part that must be called outside
706 * klp_mutex.
707 *
708 * It must be called after klp_free_patch_start(). And it has to be
709 * the last function accessing the livepatch structures when the patch
710 * gets disabled.
711 */
712static void klp_free_patch_finish(struct klp_patch *patch)
713{
714 /*
715 * Avoid deadlock with enabled_store() sysfs callback by
716 * calling this outside klp_mutex. It is safe because
717 * this is called when the patch gets disabled and it
718 * cannot get enabled again.
719 */
720 kobject_put(&patch->kobj);
721 wait_for_completion(&patch->finish);
722
723 /* Put the module after the last access to struct klp_patch. */
724 if (!patch->forced)
725 module_put(patch->mod);
726}
727
728/*
729 * The livepatch might be freed from sysfs interface created by the patch.
730 * This work allows to wait until the interface is destroyed in a separate
731 * context.
732 */
733static void klp_free_patch_work_fn(struct work_struct *work)
734{
735 struct klp_patch *patch =
736 container_of(work, struct klp_patch, free_work);
737
738 klp_free_patch_finish(patch);
739}
740
741void klp_free_patch_async(struct klp_patch *patch)
742{
743 klp_free_patch_start(patch);
744 schedule_work(&patch->free_work);
745}
746
747void klp_free_replaced_patches_async(struct klp_patch *new_patch)
748{
749 struct klp_patch *old_patch, *tmp_patch;
750
751 klp_for_each_patch_safe(old_patch, tmp_patch) {
752 if (old_patch == new_patch)
753 return;
754 klp_free_patch_async(old_patch);
755 }
756}
757
758static int klp_init_func(struct klp_object *obj, struct klp_func *func)
759{
760 if (!func->old_name)
761 return -EINVAL;
762
763 /*
764 * NOPs get the address later. The patched module must be loaded,
765 * see klp_init_object_loaded().
766 */
767 if (!func->new_func && !func->nop)
768 return -EINVAL;
769
770 if (strlen(func->old_name) >= KSYM_NAME_LEN)
771 return -EINVAL;
772
773 INIT_LIST_HEAD(&func->stack_node);
774 func->patched = false;
775 func->transition = false;
776
777 /* The format for the sysfs directory is <function,sympos> where sympos
778 * is the nth occurrence of this symbol in kallsyms for the patched
779 * object. If the user selects 0 for old_sympos, then 1 will be used
780 * since a unique symbol will be the first occurrence.
781 */
782 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
783 func->old_name,
784 func->old_sympos ? func->old_sympos : 1);
785}
786
787static int klp_write_object_relocs(struct klp_patch *patch,
788 struct klp_object *obj,
789 bool apply)
790{
791 int i, ret;
792 struct klp_modinfo *info = patch->mod->klp_info;
793
794 for (i = 1; i < info->hdr.e_shnum; i++) {
795 Elf_Shdr *sec = info->sechdrs + i;
796
797 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
798 continue;
799
800 ret = klp_write_section_relocs(patch->mod, info->sechdrs,
801 info->secstrings,
802 patch->mod->core_kallsyms.strtab,
803 info->symndx, i, obj->name, apply);
804 if (ret)
805 return ret;
806 }
807
808 return 0;
809}
810
811static int klp_apply_object_relocs(struct klp_patch *patch,
812 struct klp_object *obj)
813{
814 return klp_write_object_relocs(patch, obj, true);
815}
816
817static void klp_clear_object_relocs(struct klp_patch *patch,
818 struct klp_object *obj)
819{
820 klp_write_object_relocs(patch, obj, false);
821}
822
823/* parts of the initialization that is done only when the object is loaded */
824static int klp_init_object_loaded(struct klp_patch *patch,
825 struct klp_object *obj)
826{
827 struct klp_func *func;
828 int ret;
829
830 if (klp_is_module(obj)) {
831 /*
832 * Only write module-specific relocations here
833 * (.klp.rela.{module}.*). vmlinux-specific relocations were
834 * written earlier during the initialization of the klp module
835 * itself.
836 */
837 ret = klp_apply_object_relocs(patch, obj);
838 if (ret)
839 return ret;
840 }
841
842 klp_for_each_func(obj, func) {
843 ret = klp_find_object_symbol(obj->name, func->old_name,
844 func->old_sympos,
845 (unsigned long *)&func->old_func);
846 if (ret)
847 return ret;
848
849 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
850 &func->old_size, NULL);
851 if (!ret) {
852 pr_err("kallsyms size lookup failed for '%s'\n",
853 func->old_name);
854 return -ENOENT;
855 }
856
857 if (func->nop)
858 func->new_func = func->old_func;
859
860 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
861 &func->new_size, NULL);
862 if (!ret) {
863 pr_err("kallsyms size lookup failed for '%s' replacement\n",
864 func->old_name);
865 return -ENOENT;
866 }
867 }
868
869 return 0;
870}
871
872static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
873{
874 struct klp_func *func;
875 int ret;
876 const char *name;
877
878 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
879 return -EINVAL;
880
881 obj->patched = false;
882 obj->mod = NULL;
883
884 klp_find_object_module(obj);
885
886 name = klp_is_module(obj) ? obj->name : "vmlinux";
887 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
888 if (ret)
889 return ret;
890
891 klp_for_each_func(obj, func) {
892 ret = klp_init_func(obj, func);
893 if (ret)
894 return ret;
895 }
896
897 if (klp_is_object_loaded(obj))
898 ret = klp_init_object_loaded(patch, obj);
899
900 return ret;
901}
902
903static void klp_init_func_early(struct klp_object *obj,
904 struct klp_func *func)
905{
906 kobject_init(&func->kobj, &klp_ktype_func);
907 list_add_tail(&func->node, &obj->func_list);
908}
909
910static void klp_init_object_early(struct klp_patch *patch,
911 struct klp_object *obj)
912{
913 INIT_LIST_HEAD(&obj->func_list);
914 kobject_init(&obj->kobj, &klp_ktype_object);
915 list_add_tail(&obj->node, &patch->obj_list);
916}
917
918static void klp_init_patch_early(struct klp_patch *patch)
919{
920 struct klp_object *obj;
921 struct klp_func *func;
922
923 INIT_LIST_HEAD(&patch->list);
924 INIT_LIST_HEAD(&patch->obj_list);
925 kobject_init(&patch->kobj, &klp_ktype_patch);
926 patch->enabled = false;
927 patch->forced = false;
928 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
929 init_completion(&patch->finish);
930
931 klp_for_each_object_static(patch, obj) {
932 klp_init_object_early(patch, obj);
933
934 klp_for_each_func_static(obj, func) {
935 klp_init_func_early(obj, func);
936 }
937 }
938}
939
940static int klp_init_patch(struct klp_patch *patch)
941{
942 struct klp_object *obj;
943 int ret;
944
945 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
946 if (ret)
947 return ret;
948
949 if (patch->replace) {
950 ret = klp_add_nops(patch);
951 if (ret)
952 return ret;
953 }
954
955 klp_for_each_object(patch, obj) {
956 ret = klp_init_object(patch, obj);
957 if (ret)
958 return ret;
959 }
960
961 list_add_tail(&patch->list, &klp_patches);
962
963 return 0;
964}
965
966static int __klp_disable_patch(struct klp_patch *patch)
967{
968 struct klp_object *obj;
969
970 if (WARN_ON(!patch->enabled))
971 return -EINVAL;
972
973 if (klp_transition_patch)
974 return -EBUSY;
975
976 klp_init_transition(patch, KLP_UNPATCHED);
977
978 klp_for_each_object(patch, obj)
979 if (obj->patched)
980 klp_pre_unpatch_callback(obj);
981
982 /*
983 * Enforce the order of the func->transition writes in
984 * klp_init_transition() and the TIF_PATCH_PENDING writes in
985 * klp_start_transition(). In the rare case where klp_ftrace_handler()
986 * is called shortly after klp_update_patch_state() switches the task,
987 * this ensures the handler sees that func->transition is set.
988 */
989 smp_wmb();
990
991 klp_start_transition();
992 patch->enabled = false;
993 klp_try_complete_transition();
994
995 return 0;
996}
997
998static int __klp_enable_patch(struct klp_patch *patch)
999{
1000 struct klp_object *obj;
1001 int ret;
1002
1003 if (klp_transition_patch)
1004 return -EBUSY;
1005
1006 if (WARN_ON(patch->enabled))
1007 return -EINVAL;
1008
1009 pr_notice("enabling patch '%s'\n", patch->mod->name);
1010
1011 klp_init_transition(patch, KLP_PATCHED);
1012
1013 /*
1014 * Enforce the order of the func->transition writes in
1015 * klp_init_transition() and the ops->func_stack writes in
1016 * klp_patch_object(), so that klp_ftrace_handler() will see the
1017 * func->transition updates before the handler is registered and the
1018 * new funcs become visible to the handler.
1019 */
1020 smp_wmb();
1021
1022 klp_for_each_object(patch, obj) {
1023 if (!klp_is_object_loaded(obj))
1024 continue;
1025
1026 ret = klp_pre_patch_callback(obj);
1027 if (ret) {
1028 pr_warn("pre-patch callback failed for object '%s'\n",
1029 klp_is_module(obj) ? obj->name : "vmlinux");
1030 goto err;
1031 }
1032
1033 ret = klp_patch_object(obj);
1034 if (ret) {
1035 pr_warn("failed to patch object '%s'\n",
1036 klp_is_module(obj) ? obj->name : "vmlinux");
1037 goto err;
1038 }
1039 }
1040
1041 klp_start_transition();
1042 patch->enabled = true;
1043 klp_try_complete_transition();
1044
1045 return 0;
1046err:
1047 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
1048
1049 klp_cancel_transition();
1050 return ret;
1051}
1052
1053/**
1054 * klp_enable_patch() - enable the livepatch
1055 * @patch: patch to be enabled
1056 *
1057 * Initializes the data structure associated with the patch, creates the sysfs
1058 * interface, performs the needed symbol lookups and code relocations,
1059 * registers the patched functions with ftrace.
1060 *
1061 * This function is supposed to be called from the livepatch module_init()
1062 * callback.
1063 *
1064 * Return: 0 on success, otherwise error
1065 */
1066int klp_enable_patch(struct klp_patch *patch)
1067{
1068 int ret;
1069 struct klp_object *obj;
1070
1071 if (!patch || !patch->mod || !patch->objs)
1072 return -EINVAL;
1073
1074 klp_for_each_object_static(patch, obj) {
1075 if (!obj->funcs)
1076 return -EINVAL;
1077 }
1078
1079
1080 if (!is_livepatch_module(patch->mod)) {
1081 pr_err("module %s is not marked as a livepatch module\n",
1082 patch->mod->name);
1083 return -EINVAL;
1084 }
1085
1086 if (!klp_initialized())
1087 return -ENODEV;
1088
1089 if (!klp_have_reliable_stack()) {
1090 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1091 pr_warn("The livepatch transition may never complete.\n");
1092 }
1093
1094 mutex_lock(&klp_mutex);
1095
1096 if (!klp_is_patch_compatible(patch)) {
1097 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1098 patch->mod->name);
1099 mutex_unlock(&klp_mutex);
1100 return -EINVAL;
1101 }
1102
1103 if (!try_module_get(patch->mod)) {
1104 mutex_unlock(&klp_mutex);
1105 return -ENODEV;
1106 }
1107
1108 klp_init_patch_early(patch);
1109
1110 ret = klp_init_patch(patch);
1111 if (ret)
1112 goto err;
1113
1114 ret = __klp_enable_patch(patch);
1115 if (ret)
1116 goto err;
1117
1118 mutex_unlock(&klp_mutex);
1119
1120 return 0;
1121
1122err:
1123 klp_free_patch_start(patch);
1124
1125 mutex_unlock(&klp_mutex);
1126
1127 klp_free_patch_finish(patch);
1128
1129 return ret;
1130}
1131EXPORT_SYMBOL_GPL(klp_enable_patch);
1132
1133/*
1134 * This function unpatches objects from the replaced livepatches.
1135 *
1136 * We could be pretty aggressive here. It is called in the situation where
1137 * these structures are no longer accessed from the ftrace handler.
1138 * All functions are redirected by the klp_transition_patch. They
1139 * use either a new code or they are in the original code because
1140 * of the special nop function patches.
1141 *
1142 * The only exception is when the transition was forced. In this case,
1143 * klp_ftrace_handler() might still see the replaced patch on the stack.
1144 * Fortunately, it is carefully designed to work with removed functions
1145 * thanks to RCU. We only have to keep the patches on the system. Also
1146 * this is handled transparently by patch->module_put.
1147 */
1148void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1149{
1150 struct klp_patch *old_patch;
1151
1152 klp_for_each_patch(old_patch) {
1153 if (old_patch == new_patch)
1154 return;
1155
1156 old_patch->enabled = false;
1157 klp_unpatch_objects(old_patch);
1158 }
1159}
1160
1161/*
1162 * This function removes the dynamically allocated 'nop' functions.
1163 *
1164 * We could be pretty aggressive. NOPs do not change the existing
1165 * behavior except for adding unnecessary delay by the ftrace handler.
1166 *
1167 * It is safe even when the transition was forced. The ftrace handler
1168 * will see a valid ops->func_stack entry thanks to RCU.
1169 *
1170 * We could even free the NOPs structures. They must be the last entry
1171 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1172 * It does the same as klp_synchronize_transition() to make sure that
1173 * nobody is inside the ftrace handler once the operation finishes.
1174 *
1175 * IMPORTANT: It must be called right after removing the replaced patches!
1176 */
1177void klp_discard_nops(struct klp_patch *new_patch)
1178{
1179 klp_unpatch_objects_dynamic(klp_transition_patch);
1180 klp_free_objects_dynamic(klp_transition_patch);
1181}
1182
1183/*
1184 * Remove parts of patches that touch a given kernel module. The list of
1185 * patches processed might be limited. When limit is NULL, all patches
1186 * will be handled.
1187 */
1188static void klp_cleanup_module_patches_limited(struct module *mod,
1189 struct klp_patch *limit)
1190{
1191 struct klp_patch *patch;
1192 struct klp_object *obj;
1193
1194 klp_for_each_patch(patch) {
1195 if (patch == limit)
1196 break;
1197
1198 klp_for_each_object(patch, obj) {
1199 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1200 continue;
1201
1202 if (patch != klp_transition_patch)
1203 klp_pre_unpatch_callback(obj);
1204
1205 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1206 patch->mod->name, obj->mod->name);
1207 klp_unpatch_object(obj);
1208
1209 klp_post_unpatch_callback(obj);
1210 klp_clear_object_relocs(patch, obj);
1211 klp_free_object_loaded(obj);
1212 break;
1213 }
1214 }
1215}
1216
1217int klp_module_coming(struct module *mod)
1218{
1219 int ret;
1220 struct klp_patch *patch;
1221 struct klp_object *obj;
1222
1223 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1224 return -EINVAL;
1225
1226 if (!strcmp(mod->name, "vmlinux")) {
1227 pr_err("vmlinux.ko: invalid module name\n");
1228 return -EINVAL;
1229 }
1230
1231 mutex_lock(&klp_mutex);
1232 /*
1233 * Each module has to know that klp_module_coming()
1234 * has been called. We never know what module will
1235 * get patched by a new patch.
1236 */
1237 mod->klp_alive = true;
1238
1239 klp_for_each_patch(patch) {
1240 klp_for_each_object(patch, obj) {
1241 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1242 continue;
1243
1244 obj->mod = mod;
1245
1246 ret = klp_init_object_loaded(patch, obj);
1247 if (ret) {
1248 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1249 patch->mod->name, obj->mod->name, ret);
1250 goto err;
1251 }
1252
1253 pr_notice("applying patch '%s' to loading module '%s'\n",
1254 patch->mod->name, obj->mod->name);
1255
1256 ret = klp_pre_patch_callback(obj);
1257 if (ret) {
1258 pr_warn("pre-patch callback failed for object '%s'\n",
1259 obj->name);
1260 goto err;
1261 }
1262
1263 ret = klp_patch_object(obj);
1264 if (ret) {
1265 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1266 patch->mod->name, obj->mod->name, ret);
1267
1268 klp_post_unpatch_callback(obj);
1269 goto err;
1270 }
1271
1272 if (patch != klp_transition_patch)
1273 klp_post_patch_callback(obj);
1274
1275 break;
1276 }
1277 }
1278
1279 mutex_unlock(&klp_mutex);
1280
1281 return 0;
1282
1283err:
1284 /*
1285 * If a patch is unsuccessfully applied, return
1286 * error to the module loader.
1287 */
1288 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1289 patch->mod->name, obj->mod->name, obj->mod->name);
1290 mod->klp_alive = false;
1291 obj->mod = NULL;
1292 klp_cleanup_module_patches_limited(mod, patch);
1293 mutex_unlock(&klp_mutex);
1294
1295 return ret;
1296}
1297
1298void klp_module_going(struct module *mod)
1299{
1300 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1301 mod->state != MODULE_STATE_COMING))
1302 return;
1303
1304 mutex_lock(&klp_mutex);
1305 /*
1306 * Each module has to know that klp_module_going()
1307 * has been called. We never know what module will
1308 * get patched by a new patch.
1309 */
1310 mod->klp_alive = false;
1311
1312 klp_cleanup_module_patches_limited(mod, NULL);
1313
1314 mutex_unlock(&klp_mutex);
1315}
1316
1317static int __init klp_init(void)
1318{
1319 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1320 if (!klp_root_kobj)
1321 return -ENOMEM;
1322
1323 return 0;
1324}
1325
1326module_init(klp_init);