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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/ftrace.h>
28#include <linux/list.h>
29#include <linux/kallsyms.h>
30#include <linux/livepatch.h>
31#include <asm/cacheflush.h>
32
33/**
34 * struct klp_ops - structure for tracking registered ftrace ops structs
35 *
36 * A single ftrace_ops is shared between all enabled replacement functions
37 * (klp_func structs) which have the same old_addr. This allows the switch
38 * between function versions to happen instantaneously by updating the klp_ops
39 * struct's func_stack list. The winner is the klp_func at the top of the
40 * func_stack (front of the list).
41 *
42 * @node: node for the global klp_ops list
43 * @func_stack: list head for the stack of klp_func's (active func is on top)
44 * @fops: registered ftrace ops struct
45 */
46struct klp_ops {
47 struct list_head node;
48 struct list_head func_stack;
49 struct ftrace_ops fops;
50};
51
52/*
53 * The klp_mutex protects the global lists and state transitions of any
54 * structure reachable from them. References to any structure must be obtained
55 * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
56 * ensure it gets consistent data).
57 */
58static DEFINE_MUTEX(klp_mutex);
59
60static LIST_HEAD(klp_patches);
61static LIST_HEAD(klp_ops);
62
63static struct kobject *klp_root_kobj;
64
65static struct klp_ops *klp_find_ops(unsigned long old_addr)
66{
67 struct klp_ops *ops;
68 struct klp_func *func;
69
70 list_for_each_entry(ops, &klp_ops, node) {
71 func = list_first_entry(&ops->func_stack, struct klp_func,
72 stack_node);
73 if (func->old_addr == old_addr)
74 return ops;
75 }
76
77 return NULL;
78}
79
80static bool klp_is_module(struct klp_object *obj)
81{
82 return obj->name;
83}
84
85static bool klp_is_object_loaded(struct klp_object *obj)
86{
87 return !obj->name || obj->mod;
88}
89
90/* sets obj->mod if object is not vmlinux and module is found */
91static void klp_find_object_module(struct klp_object *obj)
92{
93 struct module *mod;
94
95 if (!klp_is_module(obj))
96 return;
97
98 mutex_lock(&module_mutex);
99 /*
100 * We do not want to block removal of patched modules and therefore
101 * we do not take a reference here. The patches are removed by
102 * klp_module_going() instead.
103 */
104 mod = find_module(obj->name);
105 /*
106 * Do not mess work of klp_module_coming() and klp_module_going().
107 * Note that the patch might still be needed before klp_module_going()
108 * is called. Module functions can be called even in the GOING state
109 * until mod->exit() finishes. This is especially important for
110 * patches that modify semantic of the functions.
111 */
112 if (mod && mod->klp_alive)
113 obj->mod = mod;
114
115 mutex_unlock(&module_mutex);
116}
117
118/* klp_mutex must be held by caller */
119static bool klp_is_patch_registered(struct klp_patch *patch)
120{
121 struct klp_patch *mypatch;
122
123 list_for_each_entry(mypatch, &klp_patches, list)
124 if (mypatch == patch)
125 return true;
126
127 return false;
128}
129
130static bool klp_initialized(void)
131{
132 return !!klp_root_kobj;
133}
134
135struct klp_find_arg {
136 const char *objname;
137 const char *name;
138 unsigned long addr;
139 unsigned long count;
140 unsigned long pos;
141};
142
143static int klp_find_callback(void *data, const char *name,
144 struct module *mod, unsigned long addr)
145{
146 struct klp_find_arg *args = data;
147
148 if ((mod && !args->objname) || (!mod && args->objname))
149 return 0;
150
151 if (strcmp(args->name, name))
152 return 0;
153
154 if (args->objname && strcmp(args->objname, mod->name))
155 return 0;
156
157 args->addr = addr;
158 args->count++;
159
160 /*
161 * Finish the search when the symbol is found for the desired position
162 * or the position is not defined for a non-unique symbol.
163 */
164 if ((args->pos && (args->count == args->pos)) ||
165 (!args->pos && (args->count > 1)))
166 return 1;
167
168 return 0;
169}
170
171static int klp_find_object_symbol(const char *objname, const char *name,
172 unsigned long sympos, unsigned long *addr)
173{
174 struct klp_find_arg args = {
175 .objname = objname,
176 .name = name,
177 .addr = 0,
178 .count = 0,
179 .pos = sympos,
180 };
181
182 mutex_lock(&module_mutex);
183 kallsyms_on_each_symbol(klp_find_callback, &args);
184 mutex_unlock(&module_mutex);
185
186 /*
187 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
188 * otherwise ensure the symbol position count matches sympos.
189 */
190 if (args.addr == 0)
191 pr_err("symbol '%s' not found in symbol table\n", name);
192 else if (args.count > 1 && sympos == 0) {
193 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
194 name, objname);
195 } else if (sympos != args.count && sympos > 0) {
196 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
197 sympos, name, objname ? objname : "vmlinux");
198 } else {
199 *addr = args.addr;
200 return 0;
201 }
202
203 *addr = 0;
204 return -EINVAL;
205}
206
207/*
208 * external symbols are located outside the parent object (where the parent
209 * object is either vmlinux or the kmod being patched).
210 */
211static int klp_find_external_symbol(struct module *pmod, const char *name,
212 unsigned long *addr)
213{
214 const struct kernel_symbol *sym;
215
216 /* first, check if it's an exported symbol */
217 preempt_disable();
218 sym = find_symbol(name, NULL, NULL, true, true);
219 if (sym) {
220 *addr = sym->value;
221 preempt_enable();
222 return 0;
223 }
224 preempt_enable();
225
226 /*
227 * Check if it's in another .o within the patch module. This also
228 * checks that the external symbol is unique.
229 */
230 return klp_find_object_symbol(pmod->name, name, 0, addr);
231}
232
233static int klp_write_object_relocations(struct module *pmod,
234 struct klp_object *obj)
235{
236 int ret = 0;
237 unsigned long val;
238 struct klp_reloc *reloc;
239
240 if (WARN_ON(!klp_is_object_loaded(obj)))
241 return -EINVAL;
242
243 if (WARN_ON(!obj->relocs))
244 return -EINVAL;
245
246 module_disable_ro(pmod);
247
248 for (reloc = obj->relocs; reloc->name; reloc++) {
249 /* discover the address of the referenced symbol */
250 if (reloc->external) {
251 if (reloc->sympos > 0) {
252 pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n",
253 reloc->name);
254 ret = -EINVAL;
255 goto out;
256 }
257 ret = klp_find_external_symbol(pmod, reloc->name, &val);
258 } else
259 ret = klp_find_object_symbol(obj->name,
260 reloc->name,
261 reloc->sympos,
262 &val);
263 if (ret)
264 goto out;
265
266 ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
267 val + reloc->addend);
268 if (ret) {
269 pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
270 reloc->name, val, ret);
271 goto out;
272 }
273 }
274
275out:
276 module_enable_ro(pmod);
277 return ret;
278}
279
280static void notrace klp_ftrace_handler(unsigned long ip,
281 unsigned long parent_ip,
282 struct ftrace_ops *fops,
283 struct pt_regs *regs)
284{
285 struct klp_ops *ops;
286 struct klp_func *func;
287
288 ops = container_of(fops, struct klp_ops, fops);
289
290 rcu_read_lock();
291 func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
292 stack_node);
293 if (WARN_ON_ONCE(!func))
294 goto unlock;
295
296 klp_arch_set_pc(regs, (unsigned long)func->new_func);
297unlock:
298 rcu_read_unlock();
299}
300
301static void klp_disable_func(struct klp_func *func)
302{
303 struct klp_ops *ops;
304
305 if (WARN_ON(func->state != KLP_ENABLED))
306 return;
307 if (WARN_ON(!func->old_addr))
308 return;
309
310 ops = klp_find_ops(func->old_addr);
311 if (WARN_ON(!ops))
312 return;
313
314 if (list_is_singular(&ops->func_stack)) {
315 WARN_ON(unregister_ftrace_function(&ops->fops));
316 WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
317
318 list_del_rcu(&func->stack_node);
319 list_del(&ops->node);
320 kfree(ops);
321 } else {
322 list_del_rcu(&func->stack_node);
323 }
324
325 func->state = KLP_DISABLED;
326}
327
328static int klp_enable_func(struct klp_func *func)
329{
330 struct klp_ops *ops;
331 int ret;
332
333 if (WARN_ON(!func->old_addr))
334 return -EINVAL;
335
336 if (WARN_ON(func->state != KLP_DISABLED))
337 return -EINVAL;
338
339 ops = klp_find_ops(func->old_addr);
340 if (!ops) {
341 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
342 if (!ops)
343 return -ENOMEM;
344
345 ops->fops.func = klp_ftrace_handler;
346 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
347 FTRACE_OPS_FL_DYNAMIC |
348 FTRACE_OPS_FL_IPMODIFY;
349
350 list_add(&ops->node, &klp_ops);
351
352 INIT_LIST_HEAD(&ops->func_stack);
353 list_add_rcu(&func->stack_node, &ops->func_stack);
354
355 ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
356 if (ret) {
357 pr_err("failed to set ftrace filter for function '%s' (%d)\n",
358 func->old_name, ret);
359 goto err;
360 }
361
362 ret = register_ftrace_function(&ops->fops);
363 if (ret) {
364 pr_err("failed to register ftrace handler for function '%s' (%d)\n",
365 func->old_name, ret);
366 ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
367 goto err;
368 }
369
370
371 } else {
372 list_add_rcu(&func->stack_node, &ops->func_stack);
373 }
374
375 func->state = KLP_ENABLED;
376
377 return 0;
378
379err:
380 list_del_rcu(&func->stack_node);
381 list_del(&ops->node);
382 kfree(ops);
383 return ret;
384}
385
386static void klp_disable_object(struct klp_object *obj)
387{
388 struct klp_func *func;
389
390 klp_for_each_func(obj, func)
391 if (func->state == KLP_ENABLED)
392 klp_disable_func(func);
393
394 obj->state = KLP_DISABLED;
395}
396
397static int klp_enable_object(struct klp_object *obj)
398{
399 struct klp_func *func;
400 int ret;
401
402 if (WARN_ON(obj->state != KLP_DISABLED))
403 return -EINVAL;
404
405 if (WARN_ON(!klp_is_object_loaded(obj)))
406 return -EINVAL;
407
408 klp_for_each_func(obj, func) {
409 ret = klp_enable_func(func);
410 if (ret) {
411 klp_disable_object(obj);
412 return ret;
413 }
414 }
415 obj->state = KLP_ENABLED;
416
417 return 0;
418}
419
420static int __klp_disable_patch(struct klp_patch *patch)
421{
422 struct klp_object *obj;
423
424 /* enforce stacking: only the last enabled patch can be disabled */
425 if (!list_is_last(&patch->list, &klp_patches) &&
426 list_next_entry(patch, list)->state == KLP_ENABLED)
427 return -EBUSY;
428
429 pr_notice("disabling patch '%s'\n", patch->mod->name);
430
431 klp_for_each_object(patch, obj) {
432 if (obj->state == KLP_ENABLED)
433 klp_disable_object(obj);
434 }
435
436 patch->state = KLP_DISABLED;
437
438 return 0;
439}
440
441/**
442 * klp_disable_patch() - disables a registered patch
443 * @patch: The registered, enabled patch to be disabled
444 *
445 * Unregisters the patched functions from ftrace.
446 *
447 * Return: 0 on success, otherwise error
448 */
449int klp_disable_patch(struct klp_patch *patch)
450{
451 int ret;
452
453 mutex_lock(&klp_mutex);
454
455 if (!klp_is_patch_registered(patch)) {
456 ret = -EINVAL;
457 goto err;
458 }
459
460 if (patch->state == KLP_DISABLED) {
461 ret = -EINVAL;
462 goto err;
463 }
464
465 ret = __klp_disable_patch(patch);
466
467err:
468 mutex_unlock(&klp_mutex);
469 return ret;
470}
471EXPORT_SYMBOL_GPL(klp_disable_patch);
472
473static int __klp_enable_patch(struct klp_patch *patch)
474{
475 struct klp_object *obj;
476 int ret;
477
478 if (WARN_ON(patch->state != KLP_DISABLED))
479 return -EINVAL;
480
481 /* enforce stacking: only the first disabled patch can be enabled */
482 if (patch->list.prev != &klp_patches &&
483 list_prev_entry(patch, list)->state == KLP_DISABLED)
484 return -EBUSY;
485
486 pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
487 add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
488
489 pr_notice("enabling patch '%s'\n", patch->mod->name);
490
491 klp_for_each_object(patch, obj) {
492 if (!klp_is_object_loaded(obj))
493 continue;
494
495 ret = klp_enable_object(obj);
496 if (ret)
497 goto unregister;
498 }
499
500 patch->state = KLP_ENABLED;
501
502 return 0;
503
504unregister:
505 WARN_ON(__klp_disable_patch(patch));
506 return ret;
507}
508
509/**
510 * klp_enable_patch() - enables a registered patch
511 * @patch: The registered, disabled patch to be enabled
512 *
513 * Performs the needed symbol lookups and code relocations,
514 * then registers the patched functions with ftrace.
515 *
516 * Return: 0 on success, otherwise error
517 */
518int klp_enable_patch(struct klp_patch *patch)
519{
520 int ret;
521
522 mutex_lock(&klp_mutex);
523
524 if (!klp_is_patch_registered(patch)) {
525 ret = -EINVAL;
526 goto err;
527 }
528
529 ret = __klp_enable_patch(patch);
530
531err:
532 mutex_unlock(&klp_mutex);
533 return ret;
534}
535EXPORT_SYMBOL_GPL(klp_enable_patch);
536
537/*
538 * Sysfs Interface
539 *
540 * /sys/kernel/livepatch
541 * /sys/kernel/livepatch/<patch>
542 * /sys/kernel/livepatch/<patch>/enabled
543 * /sys/kernel/livepatch/<patch>/<object>
544 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
545 */
546
547static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
548 const char *buf, size_t count)
549{
550 struct klp_patch *patch;
551 int ret;
552 unsigned long val;
553
554 ret = kstrtoul(buf, 10, &val);
555 if (ret)
556 return -EINVAL;
557
558 if (val != KLP_DISABLED && val != KLP_ENABLED)
559 return -EINVAL;
560
561 patch = container_of(kobj, struct klp_patch, kobj);
562
563 mutex_lock(&klp_mutex);
564
565 if (val == patch->state) {
566 /* already in requested state */
567 ret = -EINVAL;
568 goto err;
569 }
570
571 if (val == KLP_ENABLED) {
572 ret = __klp_enable_patch(patch);
573 if (ret)
574 goto err;
575 } else {
576 ret = __klp_disable_patch(patch);
577 if (ret)
578 goto err;
579 }
580
581 mutex_unlock(&klp_mutex);
582
583 return count;
584
585err:
586 mutex_unlock(&klp_mutex);
587 return ret;
588}
589
590static ssize_t enabled_show(struct kobject *kobj,
591 struct kobj_attribute *attr, char *buf)
592{
593 struct klp_patch *patch;
594
595 patch = container_of(kobj, struct klp_patch, kobj);
596 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
597}
598
599static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
600static struct attribute *klp_patch_attrs[] = {
601 &enabled_kobj_attr.attr,
602 NULL
603};
604
605static void klp_kobj_release_patch(struct kobject *kobj)
606{
607 /*
608 * Once we have a consistency model we'll need to module_put() the
609 * patch module here. See klp_register_patch() for more details.
610 */
611}
612
613static struct kobj_type klp_ktype_patch = {
614 .release = klp_kobj_release_patch,
615 .sysfs_ops = &kobj_sysfs_ops,
616 .default_attrs = klp_patch_attrs,
617};
618
619static void klp_kobj_release_object(struct kobject *kobj)
620{
621}
622
623static struct kobj_type klp_ktype_object = {
624 .release = klp_kobj_release_object,
625 .sysfs_ops = &kobj_sysfs_ops,
626};
627
628static void klp_kobj_release_func(struct kobject *kobj)
629{
630}
631
632static struct kobj_type klp_ktype_func = {
633 .release = klp_kobj_release_func,
634 .sysfs_ops = &kobj_sysfs_ops,
635};
636
637/*
638 * Free all functions' kobjects in the array up to some limit. When limit is
639 * NULL, all kobjects are freed.
640 */
641static void klp_free_funcs_limited(struct klp_object *obj,
642 struct klp_func *limit)
643{
644 struct klp_func *func;
645
646 for (func = obj->funcs; func->old_name && func != limit; func++)
647 kobject_put(&func->kobj);
648}
649
650/* Clean up when a patched object is unloaded */
651static void klp_free_object_loaded(struct klp_object *obj)
652{
653 struct klp_func *func;
654
655 obj->mod = NULL;
656
657 klp_for_each_func(obj, func)
658 func->old_addr = 0;
659}
660
661/*
662 * Free all objects' kobjects in the array up to some limit. When limit is
663 * NULL, all kobjects are freed.
664 */
665static void klp_free_objects_limited(struct klp_patch *patch,
666 struct klp_object *limit)
667{
668 struct klp_object *obj;
669
670 for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
671 klp_free_funcs_limited(obj, NULL);
672 kobject_put(&obj->kobj);
673 }
674}
675
676static void klp_free_patch(struct klp_patch *patch)
677{
678 klp_free_objects_limited(patch, NULL);
679 if (!list_empty(&patch->list))
680 list_del(&patch->list);
681 kobject_put(&patch->kobj);
682}
683
684static int klp_init_func(struct klp_object *obj, struct klp_func *func)
685{
686 INIT_LIST_HEAD(&func->stack_node);
687 func->state = KLP_DISABLED;
688
689 /* The format for the sysfs directory is <function,sympos> where sympos
690 * is the nth occurrence of this symbol in kallsyms for the patched
691 * object. If the user selects 0 for old_sympos, then 1 will be used
692 * since a unique symbol will be the first occurrence.
693 */
694 return kobject_init_and_add(&func->kobj, &klp_ktype_func,
695 &obj->kobj, "%s,%lu", func->old_name,
696 func->old_sympos ? func->old_sympos : 1);
697}
698
699/* parts of the initialization that is done only when the object is loaded */
700static int klp_init_object_loaded(struct klp_patch *patch,
701 struct klp_object *obj)
702{
703 struct klp_func *func;
704 int ret;
705
706 if (obj->relocs) {
707 ret = klp_write_object_relocations(patch->mod, obj);
708 if (ret)
709 return ret;
710 }
711
712 klp_for_each_func(obj, func) {
713 ret = klp_find_object_symbol(obj->name, func->old_name,
714 func->old_sympos,
715 &func->old_addr);
716 if (ret)
717 return ret;
718 }
719
720 return 0;
721}
722
723static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
724{
725 struct klp_func *func;
726 int ret;
727 const char *name;
728
729 if (!obj->funcs)
730 return -EINVAL;
731
732 obj->state = KLP_DISABLED;
733 obj->mod = NULL;
734
735 klp_find_object_module(obj);
736
737 name = klp_is_module(obj) ? obj->name : "vmlinux";
738 ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
739 &patch->kobj, "%s", name);
740 if (ret)
741 return ret;
742
743 klp_for_each_func(obj, func) {
744 ret = klp_init_func(obj, func);
745 if (ret)
746 goto free;
747 }
748
749 if (klp_is_object_loaded(obj)) {
750 ret = klp_init_object_loaded(patch, obj);
751 if (ret)
752 goto free;
753 }
754
755 return 0;
756
757free:
758 klp_free_funcs_limited(obj, func);
759 kobject_put(&obj->kobj);
760 return ret;
761}
762
763static int klp_init_patch(struct klp_patch *patch)
764{
765 struct klp_object *obj;
766 int ret;
767
768 if (!patch->objs)
769 return -EINVAL;
770
771 mutex_lock(&klp_mutex);
772
773 patch->state = KLP_DISABLED;
774
775 ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
776 klp_root_kobj, "%s", patch->mod->name);
777 if (ret)
778 goto unlock;
779
780 klp_for_each_object(patch, obj) {
781 ret = klp_init_object(patch, obj);
782 if (ret)
783 goto free;
784 }
785
786 list_add_tail(&patch->list, &klp_patches);
787
788 mutex_unlock(&klp_mutex);
789
790 return 0;
791
792free:
793 klp_free_objects_limited(patch, obj);
794 kobject_put(&patch->kobj);
795unlock:
796 mutex_unlock(&klp_mutex);
797 return ret;
798}
799
800/**
801 * klp_unregister_patch() - unregisters a patch
802 * @patch: Disabled patch to be unregistered
803 *
804 * Frees the data structures and removes the sysfs interface.
805 *
806 * Return: 0 on success, otherwise error
807 */
808int klp_unregister_patch(struct klp_patch *patch)
809{
810 int ret = 0;
811
812 mutex_lock(&klp_mutex);
813
814 if (!klp_is_patch_registered(patch)) {
815 ret = -EINVAL;
816 goto out;
817 }
818
819 if (patch->state == KLP_ENABLED) {
820 ret = -EBUSY;
821 goto out;
822 }
823
824 klp_free_patch(patch);
825
826out:
827 mutex_unlock(&klp_mutex);
828 return ret;
829}
830EXPORT_SYMBOL_GPL(klp_unregister_patch);
831
832/**
833 * klp_register_patch() - registers a patch
834 * @patch: Patch to be registered
835 *
836 * Initializes the data structure associated with the patch and
837 * creates the sysfs interface.
838 *
839 * Return: 0 on success, otherwise error
840 */
841int klp_register_patch(struct klp_patch *patch)
842{
843 int ret;
844
845 if (!klp_initialized())
846 return -ENODEV;
847
848 if (!patch || !patch->mod)
849 return -EINVAL;
850
851 /*
852 * A reference is taken on the patch module to prevent it from being
853 * unloaded. Right now, we don't allow patch modules to unload since
854 * there is currently no method to determine if a thread is still
855 * running in the patched code contained in the patch module once
856 * the ftrace registration is successful.
857 */
858 if (!try_module_get(patch->mod))
859 return -ENODEV;
860
861 ret = klp_init_patch(patch);
862 if (ret)
863 module_put(patch->mod);
864
865 return ret;
866}
867EXPORT_SYMBOL_GPL(klp_register_patch);
868
869int klp_module_coming(struct module *mod)
870{
871 int ret;
872 struct klp_patch *patch;
873 struct klp_object *obj;
874
875 if (WARN_ON(mod->state != MODULE_STATE_COMING))
876 return -EINVAL;
877
878 mutex_lock(&klp_mutex);
879 /*
880 * Each module has to know that klp_module_coming()
881 * has been called. We never know what module will
882 * get patched by a new patch.
883 */
884 mod->klp_alive = true;
885
886 list_for_each_entry(patch, &klp_patches, list) {
887 klp_for_each_object(patch, obj) {
888 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
889 continue;
890
891 obj->mod = mod;
892
893 ret = klp_init_object_loaded(patch, obj);
894 if (ret) {
895 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
896 patch->mod->name, obj->mod->name, ret);
897 goto err;
898 }
899
900 if (patch->state == KLP_DISABLED)
901 break;
902
903 pr_notice("applying patch '%s' to loading module '%s'\n",
904 patch->mod->name, obj->mod->name);
905
906 ret = klp_enable_object(obj);
907 if (ret) {
908 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
909 patch->mod->name, obj->mod->name, ret);
910 goto err;
911 }
912
913 break;
914 }
915 }
916
917 mutex_unlock(&klp_mutex);
918
919 return 0;
920
921err:
922 /*
923 * If a patch is unsuccessfully applied, return
924 * error to the module loader.
925 */
926 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
927 patch->mod->name, obj->mod->name, obj->mod->name);
928 mod->klp_alive = false;
929 klp_free_object_loaded(obj);
930 mutex_unlock(&klp_mutex);
931
932 return ret;
933}
934
935void klp_module_going(struct module *mod)
936{
937 struct klp_patch *patch;
938 struct klp_object *obj;
939
940 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
941 mod->state != MODULE_STATE_COMING))
942 return;
943
944 mutex_lock(&klp_mutex);
945 /*
946 * Each module has to know that klp_module_going()
947 * has been called. We never know what module will
948 * get patched by a new patch.
949 */
950 mod->klp_alive = false;
951
952 list_for_each_entry(patch, &klp_patches, list) {
953 klp_for_each_object(patch, obj) {
954 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
955 continue;
956
957 if (patch->state != KLP_DISABLED) {
958 pr_notice("reverting patch '%s' on unloading module '%s'\n",
959 patch->mod->name, obj->mod->name);
960 klp_disable_object(obj);
961 }
962
963 klp_free_object_loaded(obj);
964 break;
965 }
966 }
967
968 mutex_unlock(&klp_mutex);
969}
970
971static int __init klp_init(void)
972{
973 int ret;
974
975 ret = klp_check_compiler_support();
976 if (ret) {
977 pr_info("Your compiler is too old; turning off.\n");
978 return -EINVAL;
979 }
980
981 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
982 if (!klp_root_kobj)
983 return -ENOMEM;
984
985 return 0;
986}
987
988module_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>/replace
350 * /sys/kernel/livepatch/<patch>/<object>
351 * /sys/kernel/livepatch/<patch>/<object>/patched
352 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
353 */
354static int __klp_disable_patch(struct klp_patch *patch);
355
356static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
357 const char *buf, size_t count)
358{
359 struct klp_patch *patch;
360 int ret;
361 bool enabled;
362
363 ret = kstrtobool(buf, &enabled);
364 if (ret)
365 return ret;
366
367 patch = container_of(kobj, struct klp_patch, kobj);
368
369 mutex_lock(&klp_mutex);
370
371 if (patch->enabled == enabled) {
372 /* already in requested state */
373 ret = -EINVAL;
374 goto out;
375 }
376
377 /*
378 * Allow to reverse a pending transition in both ways. It might be
379 * necessary to complete the transition without forcing and breaking
380 * the system integrity.
381 *
382 * Do not allow to re-enable a disabled patch.
383 */
384 if (patch == klp_transition_patch)
385 klp_reverse_transition();
386 else if (!enabled)
387 ret = __klp_disable_patch(patch);
388 else
389 ret = -EINVAL;
390
391out:
392 mutex_unlock(&klp_mutex);
393
394 if (ret)
395 return ret;
396 return count;
397}
398
399static ssize_t enabled_show(struct kobject *kobj,
400 struct kobj_attribute *attr, char *buf)
401{
402 struct klp_patch *patch;
403
404 patch = container_of(kobj, struct klp_patch, kobj);
405 return sysfs_emit(buf, "%d\n", patch->enabled);
406}
407
408static ssize_t transition_show(struct kobject *kobj,
409 struct kobj_attribute *attr, char *buf)
410{
411 struct klp_patch *patch;
412
413 patch = container_of(kobj, struct klp_patch, kobj);
414 return sysfs_emit(buf, "%d\n", 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 ssize_t replace_show(struct kobject *kobj,
447 struct kobj_attribute *attr, char *buf)
448{
449 struct klp_patch *patch;
450
451 patch = container_of(kobj, struct klp_patch, kobj);
452 return sysfs_emit(buf, "%d\n", patch->replace);
453}
454
455static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
456static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
457static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
458static struct kobj_attribute replace_kobj_attr = __ATTR_RO(replace);
459static struct attribute *klp_patch_attrs[] = {
460 &enabled_kobj_attr.attr,
461 &transition_kobj_attr.attr,
462 &force_kobj_attr.attr,
463 &replace_kobj_attr.attr,
464 NULL
465};
466ATTRIBUTE_GROUPS(klp_patch);
467
468static ssize_t patched_show(struct kobject *kobj,
469 struct kobj_attribute *attr, char *buf)
470{
471 struct klp_object *obj;
472
473 obj = container_of(kobj, struct klp_object, kobj);
474 return sysfs_emit(buf, "%d\n", obj->patched);
475}
476
477static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
478static struct attribute *klp_object_attrs[] = {
479 &patched_kobj_attr.attr,
480 NULL,
481};
482ATTRIBUTE_GROUPS(klp_object);
483
484static void klp_free_object_dynamic(struct klp_object *obj)
485{
486 kfree(obj->name);
487 kfree(obj);
488}
489
490static void klp_init_func_early(struct klp_object *obj,
491 struct klp_func *func);
492static void klp_init_object_early(struct klp_patch *patch,
493 struct klp_object *obj);
494
495static struct klp_object *klp_alloc_object_dynamic(const char *name,
496 struct klp_patch *patch)
497{
498 struct klp_object *obj;
499
500 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
501 if (!obj)
502 return NULL;
503
504 if (name) {
505 obj->name = kstrdup(name, GFP_KERNEL);
506 if (!obj->name) {
507 kfree(obj);
508 return NULL;
509 }
510 }
511
512 klp_init_object_early(patch, obj);
513 obj->dynamic = true;
514
515 return obj;
516}
517
518static void klp_free_func_nop(struct klp_func *func)
519{
520 kfree(func->old_name);
521 kfree(func);
522}
523
524static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
525 struct klp_object *obj)
526{
527 struct klp_func *func;
528
529 func = kzalloc(sizeof(*func), GFP_KERNEL);
530 if (!func)
531 return NULL;
532
533 if (old_func->old_name) {
534 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
535 if (!func->old_name) {
536 kfree(func);
537 return NULL;
538 }
539 }
540
541 klp_init_func_early(obj, func);
542 /*
543 * func->new_func is same as func->old_func. These addresses are
544 * set when the object is loaded, see klp_init_object_loaded().
545 */
546 func->old_sympos = old_func->old_sympos;
547 func->nop = true;
548
549 return func;
550}
551
552static int klp_add_object_nops(struct klp_patch *patch,
553 struct klp_object *old_obj)
554{
555 struct klp_object *obj;
556 struct klp_func *func, *old_func;
557
558 obj = klp_find_object(patch, old_obj);
559
560 if (!obj) {
561 obj = klp_alloc_object_dynamic(old_obj->name, patch);
562 if (!obj)
563 return -ENOMEM;
564 }
565
566 klp_for_each_func(old_obj, old_func) {
567 func = klp_find_func(obj, old_func);
568 if (func)
569 continue;
570
571 func = klp_alloc_func_nop(old_func, obj);
572 if (!func)
573 return -ENOMEM;
574 }
575
576 return 0;
577}
578
579/*
580 * Add 'nop' functions which simply return to the caller to run
581 * the original function. The 'nop' functions are added to a
582 * patch to facilitate a 'replace' mode.
583 */
584static int klp_add_nops(struct klp_patch *patch)
585{
586 struct klp_patch *old_patch;
587 struct klp_object *old_obj;
588
589 klp_for_each_patch(old_patch) {
590 klp_for_each_object(old_patch, old_obj) {
591 int err;
592
593 err = klp_add_object_nops(patch, old_obj);
594 if (err)
595 return err;
596 }
597 }
598
599 return 0;
600}
601
602static void klp_kobj_release_patch(struct kobject *kobj)
603{
604 struct klp_patch *patch;
605
606 patch = container_of(kobj, struct klp_patch, kobj);
607 complete(&patch->finish);
608}
609
610static const struct kobj_type klp_ktype_patch = {
611 .release = klp_kobj_release_patch,
612 .sysfs_ops = &kobj_sysfs_ops,
613 .default_groups = klp_patch_groups,
614};
615
616static void klp_kobj_release_object(struct kobject *kobj)
617{
618 struct klp_object *obj;
619
620 obj = container_of(kobj, struct klp_object, kobj);
621
622 if (obj->dynamic)
623 klp_free_object_dynamic(obj);
624}
625
626static const struct kobj_type klp_ktype_object = {
627 .release = klp_kobj_release_object,
628 .sysfs_ops = &kobj_sysfs_ops,
629 .default_groups = klp_object_groups,
630};
631
632static void klp_kobj_release_func(struct kobject *kobj)
633{
634 struct klp_func *func;
635
636 func = container_of(kobj, struct klp_func, kobj);
637
638 if (func->nop)
639 klp_free_func_nop(func);
640}
641
642static const struct kobj_type klp_ktype_func = {
643 .release = klp_kobj_release_func,
644 .sysfs_ops = &kobj_sysfs_ops,
645};
646
647static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
648{
649 struct klp_func *func, *tmp_func;
650
651 klp_for_each_func_safe(obj, func, tmp_func) {
652 if (nops_only && !func->nop)
653 continue;
654
655 list_del(&func->node);
656 kobject_put(&func->kobj);
657 }
658}
659
660/* Clean up when a patched object is unloaded */
661static void klp_free_object_loaded(struct klp_object *obj)
662{
663 struct klp_func *func;
664
665 obj->mod = NULL;
666
667 klp_for_each_func(obj, func) {
668 func->old_func = NULL;
669
670 if (func->nop)
671 func->new_func = NULL;
672 }
673}
674
675static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
676{
677 struct klp_object *obj, *tmp_obj;
678
679 klp_for_each_object_safe(patch, obj, tmp_obj) {
680 __klp_free_funcs(obj, nops_only);
681
682 if (nops_only && !obj->dynamic)
683 continue;
684
685 list_del(&obj->node);
686 kobject_put(&obj->kobj);
687 }
688}
689
690static void klp_free_objects(struct klp_patch *patch)
691{
692 __klp_free_objects(patch, false);
693}
694
695static void klp_free_objects_dynamic(struct klp_patch *patch)
696{
697 __klp_free_objects(patch, true);
698}
699
700/*
701 * This function implements the free operations that can be called safely
702 * under klp_mutex.
703 *
704 * The operation must be completed by calling klp_free_patch_finish()
705 * outside klp_mutex.
706 */
707static void klp_free_patch_start(struct klp_patch *patch)
708{
709 if (!list_empty(&patch->list))
710 list_del(&patch->list);
711
712 klp_free_objects(patch);
713}
714
715/*
716 * This function implements the free part that must be called outside
717 * klp_mutex.
718 *
719 * It must be called after klp_free_patch_start(). And it has to be
720 * the last function accessing the livepatch structures when the patch
721 * gets disabled.
722 */
723static void klp_free_patch_finish(struct klp_patch *patch)
724{
725 /*
726 * Avoid deadlock with enabled_store() sysfs callback by
727 * calling this outside klp_mutex. It is safe because
728 * this is called when the patch gets disabled and it
729 * cannot get enabled again.
730 */
731 kobject_put(&patch->kobj);
732 wait_for_completion(&patch->finish);
733
734 /* Put the module after the last access to struct klp_patch. */
735 if (!patch->forced)
736 module_put(patch->mod);
737}
738
739/*
740 * The livepatch might be freed from sysfs interface created by the patch.
741 * This work allows to wait until the interface is destroyed in a separate
742 * context.
743 */
744static void klp_free_patch_work_fn(struct work_struct *work)
745{
746 struct klp_patch *patch =
747 container_of(work, struct klp_patch, free_work);
748
749 klp_free_patch_finish(patch);
750}
751
752void klp_free_patch_async(struct klp_patch *patch)
753{
754 klp_free_patch_start(patch);
755 schedule_work(&patch->free_work);
756}
757
758void klp_free_replaced_patches_async(struct klp_patch *new_patch)
759{
760 struct klp_patch *old_patch, *tmp_patch;
761
762 klp_for_each_patch_safe(old_patch, tmp_patch) {
763 if (old_patch == new_patch)
764 return;
765 klp_free_patch_async(old_patch);
766 }
767}
768
769static int klp_init_func(struct klp_object *obj, struct klp_func *func)
770{
771 if (!func->old_name)
772 return -EINVAL;
773
774 /*
775 * NOPs get the address later. The patched module must be loaded,
776 * see klp_init_object_loaded().
777 */
778 if (!func->new_func && !func->nop)
779 return -EINVAL;
780
781 if (strlen(func->old_name) >= KSYM_NAME_LEN)
782 return -EINVAL;
783
784 INIT_LIST_HEAD(&func->stack_node);
785 func->patched = false;
786 func->transition = false;
787
788 /* The format for the sysfs directory is <function,sympos> where sympos
789 * is the nth occurrence of this symbol in kallsyms for the patched
790 * object. If the user selects 0 for old_sympos, then 1 will be used
791 * since a unique symbol will be the first occurrence.
792 */
793 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
794 func->old_name,
795 func->old_sympos ? func->old_sympos : 1);
796}
797
798static int klp_write_object_relocs(struct klp_patch *patch,
799 struct klp_object *obj,
800 bool apply)
801{
802 int i, ret;
803 struct klp_modinfo *info = patch->mod->klp_info;
804
805 for (i = 1; i < info->hdr.e_shnum; i++) {
806 Elf_Shdr *sec = info->sechdrs + i;
807
808 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
809 continue;
810
811 ret = klp_write_section_relocs(patch->mod, info->sechdrs,
812 info->secstrings,
813 patch->mod->core_kallsyms.strtab,
814 info->symndx, i, obj->name, apply);
815 if (ret)
816 return ret;
817 }
818
819 return 0;
820}
821
822static int klp_apply_object_relocs(struct klp_patch *patch,
823 struct klp_object *obj)
824{
825 return klp_write_object_relocs(patch, obj, true);
826}
827
828static void klp_clear_object_relocs(struct klp_patch *patch,
829 struct klp_object *obj)
830{
831 klp_write_object_relocs(patch, obj, false);
832}
833
834/* parts of the initialization that is done only when the object is loaded */
835static int klp_init_object_loaded(struct klp_patch *patch,
836 struct klp_object *obj)
837{
838 struct klp_func *func;
839 int ret;
840
841 if (klp_is_module(obj)) {
842 /*
843 * Only write module-specific relocations here
844 * (.klp.rela.{module}.*). vmlinux-specific relocations were
845 * written earlier during the initialization of the klp module
846 * itself.
847 */
848 ret = klp_apply_object_relocs(patch, obj);
849 if (ret)
850 return ret;
851 }
852
853 klp_for_each_func(obj, func) {
854 ret = klp_find_object_symbol(obj->name, func->old_name,
855 func->old_sympos,
856 (unsigned long *)&func->old_func);
857 if (ret)
858 return ret;
859
860 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
861 &func->old_size, NULL);
862 if (!ret) {
863 pr_err("kallsyms size lookup failed for '%s'\n",
864 func->old_name);
865 return -ENOENT;
866 }
867
868 if (func->nop)
869 func->new_func = func->old_func;
870
871 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
872 &func->new_size, NULL);
873 if (!ret) {
874 pr_err("kallsyms size lookup failed for '%s' replacement\n",
875 func->old_name);
876 return -ENOENT;
877 }
878 }
879
880 return 0;
881}
882
883static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
884{
885 struct klp_func *func;
886 int ret;
887 const char *name;
888
889 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
890 return -EINVAL;
891
892 obj->patched = false;
893 obj->mod = NULL;
894
895 klp_find_object_module(obj);
896
897 name = klp_is_module(obj) ? obj->name : "vmlinux";
898 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
899 if (ret)
900 return ret;
901
902 klp_for_each_func(obj, func) {
903 ret = klp_init_func(obj, func);
904 if (ret)
905 return ret;
906 }
907
908 if (klp_is_object_loaded(obj))
909 ret = klp_init_object_loaded(patch, obj);
910
911 return ret;
912}
913
914static void klp_init_func_early(struct klp_object *obj,
915 struct klp_func *func)
916{
917 kobject_init(&func->kobj, &klp_ktype_func);
918 list_add_tail(&func->node, &obj->func_list);
919}
920
921static void klp_init_object_early(struct klp_patch *patch,
922 struct klp_object *obj)
923{
924 INIT_LIST_HEAD(&obj->func_list);
925 kobject_init(&obj->kobj, &klp_ktype_object);
926 list_add_tail(&obj->node, &patch->obj_list);
927}
928
929static void klp_init_patch_early(struct klp_patch *patch)
930{
931 struct klp_object *obj;
932 struct klp_func *func;
933
934 INIT_LIST_HEAD(&patch->list);
935 INIT_LIST_HEAD(&patch->obj_list);
936 kobject_init(&patch->kobj, &klp_ktype_patch);
937 patch->enabled = false;
938 patch->forced = false;
939 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
940 init_completion(&patch->finish);
941
942 klp_for_each_object_static(patch, obj) {
943 klp_init_object_early(patch, obj);
944
945 klp_for_each_func_static(obj, func) {
946 klp_init_func_early(obj, func);
947 }
948 }
949}
950
951static int klp_init_patch(struct klp_patch *patch)
952{
953 struct klp_object *obj;
954 int ret;
955
956 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
957 if (ret)
958 return ret;
959
960 if (patch->replace) {
961 ret = klp_add_nops(patch);
962 if (ret)
963 return ret;
964 }
965
966 klp_for_each_object(patch, obj) {
967 ret = klp_init_object(patch, obj);
968 if (ret)
969 return ret;
970 }
971
972 list_add_tail(&patch->list, &klp_patches);
973
974 return 0;
975}
976
977static int __klp_disable_patch(struct klp_patch *patch)
978{
979 struct klp_object *obj;
980
981 if (WARN_ON(!patch->enabled))
982 return -EINVAL;
983
984 if (klp_transition_patch)
985 return -EBUSY;
986
987 klp_init_transition(patch, KLP_TRANSITION_UNPATCHED);
988
989 klp_for_each_object(patch, obj)
990 if (obj->patched)
991 klp_pre_unpatch_callback(obj);
992
993 /*
994 * Enforce the order of the func->transition writes in
995 * klp_init_transition() and the TIF_PATCH_PENDING writes in
996 * klp_start_transition(). In the rare case where klp_ftrace_handler()
997 * is called shortly after klp_update_patch_state() switches the task,
998 * this ensures the handler sees that func->transition is set.
999 */
1000 smp_wmb();
1001
1002 klp_start_transition();
1003 patch->enabled = false;
1004 klp_try_complete_transition();
1005
1006 return 0;
1007}
1008
1009static int __klp_enable_patch(struct klp_patch *patch)
1010{
1011 struct klp_object *obj;
1012 int ret;
1013
1014 if (klp_transition_patch)
1015 return -EBUSY;
1016
1017 if (WARN_ON(patch->enabled))
1018 return -EINVAL;
1019
1020 pr_notice("enabling patch '%s'\n", patch->mod->name);
1021
1022 klp_init_transition(patch, KLP_TRANSITION_PATCHED);
1023
1024 /*
1025 * Enforce the order of the func->transition writes in
1026 * klp_init_transition() and the ops->func_stack writes in
1027 * klp_patch_object(), so that klp_ftrace_handler() will see the
1028 * func->transition updates before the handler is registered and the
1029 * new funcs become visible to the handler.
1030 */
1031 smp_wmb();
1032
1033 klp_for_each_object(patch, obj) {
1034 if (!klp_is_object_loaded(obj))
1035 continue;
1036
1037 ret = klp_pre_patch_callback(obj);
1038 if (ret) {
1039 pr_warn("pre-patch callback failed for object '%s'\n",
1040 klp_is_module(obj) ? obj->name : "vmlinux");
1041 goto err;
1042 }
1043
1044 ret = klp_patch_object(obj);
1045 if (ret) {
1046 pr_warn("failed to patch object '%s'\n",
1047 klp_is_module(obj) ? obj->name : "vmlinux");
1048 goto err;
1049 }
1050 }
1051
1052 klp_start_transition();
1053 patch->enabled = true;
1054 klp_try_complete_transition();
1055
1056 return 0;
1057err:
1058 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
1059
1060 klp_cancel_transition();
1061 return ret;
1062}
1063
1064/**
1065 * klp_enable_patch() - enable the livepatch
1066 * @patch: patch to be enabled
1067 *
1068 * Initializes the data structure associated with the patch, creates the sysfs
1069 * interface, performs the needed symbol lookups and code relocations,
1070 * registers the patched functions with ftrace.
1071 *
1072 * This function is supposed to be called from the livepatch module_init()
1073 * callback.
1074 *
1075 * Return: 0 on success, otherwise error
1076 */
1077int klp_enable_patch(struct klp_patch *patch)
1078{
1079 int ret;
1080 struct klp_object *obj;
1081
1082 if (!patch || !patch->mod || !patch->objs)
1083 return -EINVAL;
1084
1085 klp_for_each_object_static(patch, obj) {
1086 if (!obj->funcs)
1087 return -EINVAL;
1088 }
1089
1090
1091 if (!is_livepatch_module(patch->mod)) {
1092 pr_err("module %s is not marked as a livepatch module\n",
1093 patch->mod->name);
1094 return -EINVAL;
1095 }
1096
1097 if (!klp_initialized())
1098 return -ENODEV;
1099
1100 if (!klp_have_reliable_stack()) {
1101 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1102 pr_warn("The livepatch transition may never complete.\n");
1103 }
1104
1105 mutex_lock(&klp_mutex);
1106
1107 if (!klp_is_patch_compatible(patch)) {
1108 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1109 patch->mod->name);
1110 mutex_unlock(&klp_mutex);
1111 return -EINVAL;
1112 }
1113
1114 if (!try_module_get(patch->mod)) {
1115 mutex_unlock(&klp_mutex);
1116 return -ENODEV;
1117 }
1118
1119 klp_init_patch_early(patch);
1120
1121 ret = klp_init_patch(patch);
1122 if (ret)
1123 goto err;
1124
1125 ret = __klp_enable_patch(patch);
1126 if (ret)
1127 goto err;
1128
1129 mutex_unlock(&klp_mutex);
1130
1131 return 0;
1132
1133err:
1134 klp_free_patch_start(patch);
1135
1136 mutex_unlock(&klp_mutex);
1137
1138 klp_free_patch_finish(patch);
1139
1140 return ret;
1141}
1142EXPORT_SYMBOL_GPL(klp_enable_patch);
1143
1144/*
1145 * This function unpatches objects from the replaced livepatches.
1146 *
1147 * We could be pretty aggressive here. It is called in the situation where
1148 * these structures are no longer accessed from the ftrace handler.
1149 * All functions are redirected by the klp_transition_patch. They
1150 * use either a new code or they are in the original code because
1151 * of the special nop function patches.
1152 *
1153 * The only exception is when the transition was forced. In this case,
1154 * klp_ftrace_handler() might still see the replaced patch on the stack.
1155 * Fortunately, it is carefully designed to work with removed functions
1156 * thanks to RCU. We only have to keep the patches on the system. Also
1157 * this is handled transparently by patch->module_put.
1158 */
1159void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1160{
1161 struct klp_patch *old_patch;
1162
1163 klp_for_each_patch(old_patch) {
1164 if (old_patch == new_patch)
1165 return;
1166
1167 old_patch->enabled = false;
1168 klp_unpatch_objects(old_patch);
1169 }
1170}
1171
1172/*
1173 * This function removes the dynamically allocated 'nop' functions.
1174 *
1175 * We could be pretty aggressive. NOPs do not change the existing
1176 * behavior except for adding unnecessary delay by the ftrace handler.
1177 *
1178 * It is safe even when the transition was forced. The ftrace handler
1179 * will see a valid ops->func_stack entry thanks to RCU.
1180 *
1181 * We could even free the NOPs structures. They must be the last entry
1182 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1183 * It does the same as klp_synchronize_transition() to make sure that
1184 * nobody is inside the ftrace handler once the operation finishes.
1185 *
1186 * IMPORTANT: It must be called right after removing the replaced patches!
1187 */
1188void klp_discard_nops(struct klp_patch *new_patch)
1189{
1190 klp_unpatch_objects_dynamic(klp_transition_patch);
1191 klp_free_objects_dynamic(klp_transition_patch);
1192}
1193
1194/*
1195 * Remove parts of patches that touch a given kernel module. The list of
1196 * patches processed might be limited. When limit is NULL, all patches
1197 * will be handled.
1198 */
1199static void klp_cleanup_module_patches_limited(struct module *mod,
1200 struct klp_patch *limit)
1201{
1202 struct klp_patch *patch;
1203 struct klp_object *obj;
1204
1205 klp_for_each_patch(patch) {
1206 if (patch == limit)
1207 break;
1208
1209 klp_for_each_object(patch, obj) {
1210 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1211 continue;
1212
1213 if (patch != klp_transition_patch)
1214 klp_pre_unpatch_callback(obj);
1215
1216 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1217 patch->mod->name, obj->mod->name);
1218 klp_unpatch_object(obj);
1219
1220 klp_post_unpatch_callback(obj);
1221 klp_clear_object_relocs(patch, obj);
1222 klp_free_object_loaded(obj);
1223 break;
1224 }
1225 }
1226}
1227
1228int klp_module_coming(struct module *mod)
1229{
1230 int ret;
1231 struct klp_patch *patch;
1232 struct klp_object *obj;
1233
1234 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1235 return -EINVAL;
1236
1237 if (!strcmp(mod->name, "vmlinux")) {
1238 pr_err("vmlinux.ko: invalid module name\n");
1239 return -EINVAL;
1240 }
1241
1242 mutex_lock(&klp_mutex);
1243 /*
1244 * Each module has to know that klp_module_coming()
1245 * has been called. We never know what module will
1246 * get patched by a new patch.
1247 */
1248 mod->klp_alive = true;
1249
1250 klp_for_each_patch(patch) {
1251 klp_for_each_object(patch, obj) {
1252 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1253 continue;
1254
1255 obj->mod = mod;
1256
1257 ret = klp_init_object_loaded(patch, obj);
1258 if (ret) {
1259 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1260 patch->mod->name, obj->mod->name, ret);
1261 goto err;
1262 }
1263
1264 pr_notice("applying patch '%s' to loading module '%s'\n",
1265 patch->mod->name, obj->mod->name);
1266
1267 ret = klp_pre_patch_callback(obj);
1268 if (ret) {
1269 pr_warn("pre-patch callback failed for object '%s'\n",
1270 obj->name);
1271 goto err;
1272 }
1273
1274 ret = klp_patch_object(obj);
1275 if (ret) {
1276 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1277 patch->mod->name, obj->mod->name, ret);
1278
1279 klp_post_unpatch_callback(obj);
1280 goto err;
1281 }
1282
1283 if (patch != klp_transition_patch)
1284 klp_post_patch_callback(obj);
1285
1286 break;
1287 }
1288 }
1289
1290 mutex_unlock(&klp_mutex);
1291
1292 return 0;
1293
1294err:
1295 /*
1296 * If a patch is unsuccessfully applied, return
1297 * error to the module loader.
1298 */
1299 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1300 patch->mod->name, obj->mod->name, obj->mod->name);
1301 mod->klp_alive = false;
1302 obj->mod = NULL;
1303 klp_cleanup_module_patches_limited(mod, patch);
1304 mutex_unlock(&klp_mutex);
1305
1306 return ret;
1307}
1308
1309void klp_module_going(struct module *mod)
1310{
1311 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1312 mod->state != MODULE_STATE_COMING))
1313 return;
1314
1315 mutex_lock(&klp_mutex);
1316 /*
1317 * Each module has to know that klp_module_going()
1318 * has been called. We never know what module will
1319 * get patched by a new patch.
1320 */
1321 mod->klp_alive = false;
1322
1323 klp_cleanup_module_patches_limited(mod, NULL);
1324
1325 mutex_unlock(&klp_mutex);
1326}
1327
1328static int __init klp_init(void)
1329{
1330 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1331 if (!klp_root_kobj)
1332 return -ENOMEM;
1333
1334 return 0;
1335}
1336
1337module_init(klp_init);