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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/*
2 * core.c - Kernel Live Patching Core
3 *
4 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
5 * Copyright (C) 2014 SUSE
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2
10 * of the License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, see <http://www.gnu.org/licenses/>.
19 */
20
21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23#include <linux/module.h>
24#include <linux/kernel.h>
25#include <linux/mutex.h>
26#include <linux/slab.h>
27#include <linux/list.h>
28#include <linux/kallsyms.h>
29#include <linux/livepatch.h>
30#include <linux/elf.h>
31#include <linux/moduleloader.h>
32#include <linux/completion.h>
33#include <asm/cacheflush.h>
34#include "core.h"
35#include "patch.h"
36#include "transition.h"
37
38/*
39 * klp_mutex is a coarse lock which serializes access to klp data. All
40 * accesses to klp-related variables and structures must have mutex protection,
41 * except within the following functions which carefully avoid the need for it:
42 *
43 * - klp_ftrace_handler()
44 * - klp_update_patch_state()
45 */
46DEFINE_MUTEX(klp_mutex);
47
48static LIST_HEAD(klp_patches);
49
50static struct kobject *klp_root_kobj;
51
52static bool klp_is_module(struct klp_object *obj)
53{
54 return obj->name;
55}
56
57/* sets obj->mod if object is not vmlinux and module is found */
58static void klp_find_object_module(struct klp_object *obj)
59{
60 struct module *mod;
61
62 if (!klp_is_module(obj))
63 return;
64
65 mutex_lock(&module_mutex);
66 /*
67 * We do not want to block removal of patched modules and therefore
68 * we do not take a reference here. The patches are removed by
69 * klp_module_going() instead.
70 */
71 mod = find_module(obj->name);
72 /*
73 * Do not mess work of klp_module_coming() and klp_module_going().
74 * Note that the patch might still be needed before klp_module_going()
75 * is called. Module functions can be called even in the GOING state
76 * until mod->exit() finishes. This is especially important for
77 * patches that modify semantic of the functions.
78 */
79 if (mod && mod->klp_alive)
80 obj->mod = mod;
81
82 mutex_unlock(&module_mutex);
83}
84
85static bool klp_is_patch_registered(struct klp_patch *patch)
86{
87 struct klp_patch *mypatch;
88
89 list_for_each_entry(mypatch, &klp_patches, list)
90 if (mypatch == patch)
91 return true;
92
93 return false;
94}
95
96static bool klp_initialized(void)
97{
98 return !!klp_root_kobj;
99}
100
101struct klp_find_arg {
102 const char *objname;
103 const char *name;
104 unsigned long addr;
105 unsigned long count;
106 unsigned long pos;
107};
108
109static int klp_find_callback(void *data, const char *name,
110 struct module *mod, unsigned long addr)
111{
112 struct klp_find_arg *args = data;
113
114 if ((mod && !args->objname) || (!mod && args->objname))
115 return 0;
116
117 if (strcmp(args->name, name))
118 return 0;
119
120 if (args->objname && strcmp(args->objname, mod->name))
121 return 0;
122
123 args->addr = addr;
124 args->count++;
125
126 /*
127 * Finish the search when the symbol is found for the desired position
128 * or the position is not defined for a non-unique symbol.
129 */
130 if ((args->pos && (args->count == args->pos)) ||
131 (!args->pos && (args->count > 1)))
132 return 1;
133
134 return 0;
135}
136
137static int klp_find_object_symbol(const char *objname, const char *name,
138 unsigned long sympos, unsigned long *addr)
139{
140 struct klp_find_arg args = {
141 .objname = objname,
142 .name = name,
143 .addr = 0,
144 .count = 0,
145 .pos = sympos,
146 };
147
148 mutex_lock(&module_mutex);
149 if (objname)
150 module_kallsyms_on_each_symbol(klp_find_callback, &args);
151 else
152 kallsyms_on_each_symbol(klp_find_callback, &args);
153 mutex_unlock(&module_mutex);
154
155 /*
156 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
157 * otherwise ensure the symbol position count matches sympos.
158 */
159 if (args.addr == 0)
160 pr_err("symbol '%s' not found in symbol table\n", name);
161 else if (args.count > 1 && sympos == 0) {
162 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
163 name, objname);
164 } else if (sympos != args.count && sympos > 0) {
165 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
166 sympos, name, objname ? objname : "vmlinux");
167 } else {
168 *addr = args.addr;
169 return 0;
170 }
171
172 *addr = 0;
173 return -EINVAL;
174}
175
176static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
177{
178 int i, cnt, vmlinux, ret;
179 char objname[MODULE_NAME_LEN];
180 char symname[KSYM_NAME_LEN];
181 char *strtab = pmod->core_kallsyms.strtab;
182 Elf_Rela *relas;
183 Elf_Sym *sym;
184 unsigned long sympos, addr;
185
186 /*
187 * Since the field widths for objname and symname in the sscanf()
188 * call are hard-coded and correspond to MODULE_NAME_LEN and
189 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
190 * and KSYM_NAME_LEN have the values we expect them to have.
191 *
192 * Because the value of MODULE_NAME_LEN can differ among architectures,
193 * we use the smallest/strictest upper bound possible (56, based on
194 * the current definition of MODULE_NAME_LEN) to prevent overflows.
195 */
196 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
197
198 relas = (Elf_Rela *) relasec->sh_addr;
199 /* For each rela in this klp relocation section */
200 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
201 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
202 if (sym->st_shndx != SHN_LIVEPATCH) {
203 pr_err("symbol %s is not marked as a livepatch symbol\n",
204 strtab + sym->st_name);
205 return -EINVAL;
206 }
207
208 /* Format: .klp.sym.objname.symname,sympos */
209 cnt = sscanf(strtab + sym->st_name,
210 ".klp.sym.%55[^.].%127[^,],%lu",
211 objname, symname, &sympos);
212 if (cnt != 3) {
213 pr_err("symbol %s has an incorrectly formatted name\n",
214 strtab + sym->st_name);
215 return -EINVAL;
216 }
217
218 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
219 vmlinux = !strcmp(objname, "vmlinux");
220 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
221 symname, sympos, &addr);
222 if (ret)
223 return ret;
224
225 sym->st_value = addr;
226 }
227
228 return 0;
229}
230
231static int klp_write_object_relocations(struct module *pmod,
232 struct klp_object *obj)
233{
234 int i, cnt, ret = 0;
235 const char *objname, *secname;
236 char sec_objname[MODULE_NAME_LEN];
237 Elf_Shdr *sec;
238
239 if (WARN_ON(!klp_is_object_loaded(obj)))
240 return -EINVAL;
241
242 objname = klp_is_module(obj) ? obj->name : "vmlinux";
243
244 /* For each klp relocation section */
245 for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
246 sec = pmod->klp_info->sechdrs + i;
247 secname = pmod->klp_info->secstrings + sec->sh_name;
248 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
249 continue;
250
251 /*
252 * Format: .klp.rela.sec_objname.section_name
253 * See comment in klp_resolve_symbols() for an explanation
254 * of the selected field width value.
255 */
256 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
257 if (cnt != 1) {
258 pr_err("section %s has an incorrectly formatted name\n",
259 secname);
260 ret = -EINVAL;
261 break;
262 }
263
264 if (strcmp(objname, sec_objname))
265 continue;
266
267 ret = klp_resolve_symbols(sec, pmod);
268 if (ret)
269 break;
270
271 ret = apply_relocate_add(pmod->klp_info->sechdrs,
272 pmod->core_kallsyms.strtab,
273 pmod->klp_info->symndx, i, pmod);
274 if (ret)
275 break;
276 }
277
278 return ret;
279}
280
281static int __klp_disable_patch(struct klp_patch *patch)
282{
283 struct klp_object *obj;
284
285 if (WARN_ON(!patch->enabled))
286 return -EINVAL;
287
288 if (klp_transition_patch)
289 return -EBUSY;
290
291 /* enforce stacking: only the last enabled patch can be disabled */
292 if (!list_is_last(&patch->list, &klp_patches) &&
293 list_next_entry(patch, list)->enabled)
294 return -EBUSY;
295
296 klp_init_transition(patch, KLP_UNPATCHED);
297
298 klp_for_each_object(patch, obj)
299 if (obj->patched)
300 klp_pre_unpatch_callback(obj);
301
302 /*
303 * Enforce the order of the func->transition writes in
304 * klp_init_transition() and the TIF_PATCH_PENDING writes in
305 * klp_start_transition(). In the rare case where klp_ftrace_handler()
306 * is called shortly after klp_update_patch_state() switches the task,
307 * this ensures the handler sees that func->transition is set.
308 */
309 smp_wmb();
310
311 klp_start_transition();
312 klp_try_complete_transition();
313 patch->enabled = false;
314
315 return 0;
316}
317
318/**
319 * klp_disable_patch() - disables a registered patch
320 * @patch: The registered, enabled patch to be disabled
321 *
322 * Unregisters the patched functions from ftrace.
323 *
324 * Return: 0 on success, otherwise error
325 */
326int klp_disable_patch(struct klp_patch *patch)
327{
328 int ret;
329
330 mutex_lock(&klp_mutex);
331
332 if (!klp_is_patch_registered(patch)) {
333 ret = -EINVAL;
334 goto err;
335 }
336
337 if (!patch->enabled) {
338 ret = -EINVAL;
339 goto err;
340 }
341
342 ret = __klp_disable_patch(patch);
343
344err:
345 mutex_unlock(&klp_mutex);
346 return ret;
347}
348EXPORT_SYMBOL_GPL(klp_disable_patch);
349
350static int __klp_enable_patch(struct klp_patch *patch)
351{
352 struct klp_object *obj;
353 int ret;
354
355 if (klp_transition_patch)
356 return -EBUSY;
357
358 if (WARN_ON(patch->enabled))
359 return -EINVAL;
360
361 /* enforce stacking: only the first disabled patch can be enabled */
362 if (patch->list.prev != &klp_patches &&
363 !list_prev_entry(patch, list)->enabled)
364 return -EBUSY;
365
366 /*
367 * A reference is taken on the patch module to prevent it from being
368 * unloaded.
369 */
370 if (!try_module_get(patch->mod))
371 return -ENODEV;
372
373 pr_notice("enabling patch '%s'\n", patch->mod->name);
374
375 klp_init_transition(patch, KLP_PATCHED);
376
377 /*
378 * Enforce the order of the func->transition writes in
379 * klp_init_transition() and the ops->func_stack writes in
380 * klp_patch_object(), so that klp_ftrace_handler() will see the
381 * func->transition updates before the handler is registered and the
382 * new funcs become visible to the handler.
383 */
384 smp_wmb();
385
386 klp_for_each_object(patch, obj) {
387 if (!klp_is_object_loaded(obj))
388 continue;
389
390 ret = klp_pre_patch_callback(obj);
391 if (ret) {
392 pr_warn("pre-patch callback failed for object '%s'\n",
393 klp_is_module(obj) ? obj->name : "vmlinux");
394 goto err;
395 }
396
397 ret = klp_patch_object(obj);
398 if (ret) {
399 pr_warn("failed to patch object '%s'\n",
400 klp_is_module(obj) ? obj->name : "vmlinux");
401 goto err;
402 }
403 }
404
405 klp_start_transition();
406 klp_try_complete_transition();
407 patch->enabled = true;
408
409 return 0;
410err:
411 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
412
413 klp_cancel_transition();
414 return ret;
415}
416
417/**
418 * klp_enable_patch() - enables a registered patch
419 * @patch: The registered, disabled patch to be enabled
420 *
421 * Performs the needed symbol lookups and code relocations,
422 * then registers the patched functions with ftrace.
423 *
424 * Return: 0 on success, otherwise error
425 */
426int klp_enable_patch(struct klp_patch *patch)
427{
428 int ret;
429
430 mutex_lock(&klp_mutex);
431
432 if (!klp_is_patch_registered(patch)) {
433 ret = -EINVAL;
434 goto err;
435 }
436
437 ret = __klp_enable_patch(patch);
438
439err:
440 mutex_unlock(&klp_mutex);
441 return ret;
442}
443EXPORT_SYMBOL_GPL(klp_enable_patch);
444
445/*
446 * Sysfs Interface
447 *
448 * /sys/kernel/livepatch
449 * /sys/kernel/livepatch/<patch>
450 * /sys/kernel/livepatch/<patch>/enabled
451 * /sys/kernel/livepatch/<patch>/transition
452 * /sys/kernel/livepatch/<patch>/signal
453 * /sys/kernel/livepatch/<patch>/force
454 * /sys/kernel/livepatch/<patch>/<object>
455 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
456 */
457
458static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
459 const char *buf, size_t count)
460{
461 struct klp_patch *patch;
462 int ret;
463 bool enabled;
464
465 ret = kstrtobool(buf, &enabled);
466 if (ret)
467 return ret;
468
469 patch = container_of(kobj, struct klp_patch, kobj);
470
471 mutex_lock(&klp_mutex);
472
473 if (!klp_is_patch_registered(patch)) {
474 /*
475 * Module with the patch could either disappear meanwhile or is
476 * not properly initialized yet.
477 */
478 ret = -EINVAL;
479 goto err;
480 }
481
482 if (patch->enabled == enabled) {
483 /* already in requested state */
484 ret = -EINVAL;
485 goto err;
486 }
487
488 if (patch == klp_transition_patch) {
489 klp_reverse_transition();
490 } else if (enabled) {
491 ret = __klp_enable_patch(patch);
492 if (ret)
493 goto err;
494 } else {
495 ret = __klp_disable_patch(patch);
496 if (ret)
497 goto err;
498 }
499
500 mutex_unlock(&klp_mutex);
501
502 return count;
503
504err:
505 mutex_unlock(&klp_mutex);
506 return ret;
507}
508
509static ssize_t enabled_show(struct kobject *kobj,
510 struct kobj_attribute *attr, char *buf)
511{
512 struct klp_patch *patch;
513
514 patch = container_of(kobj, struct klp_patch, kobj);
515 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
516}
517
518static ssize_t transition_show(struct kobject *kobj,
519 struct kobj_attribute *attr, char *buf)
520{
521 struct klp_patch *patch;
522
523 patch = container_of(kobj, struct klp_patch, kobj);
524 return snprintf(buf, PAGE_SIZE-1, "%d\n",
525 patch == klp_transition_patch);
526}
527
528static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
529 const char *buf, size_t count)
530{
531 struct klp_patch *patch;
532 int ret;
533 bool val;
534
535 ret = kstrtobool(buf, &val);
536 if (ret)
537 return ret;
538
539 if (!val)
540 return count;
541
542 mutex_lock(&klp_mutex);
543
544 patch = container_of(kobj, struct klp_patch, kobj);
545 if (patch != klp_transition_patch) {
546 mutex_unlock(&klp_mutex);
547 return -EINVAL;
548 }
549
550 klp_send_signals();
551
552 mutex_unlock(&klp_mutex);
553
554 return count;
555}
556
557static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
558 const char *buf, size_t count)
559{
560 struct klp_patch *patch;
561 int ret;
562 bool val;
563
564 ret = kstrtobool(buf, &val);
565 if (ret)
566 return ret;
567
568 if (!val)
569 return count;
570
571 mutex_lock(&klp_mutex);
572
573 patch = container_of(kobj, struct klp_patch, kobj);
574 if (patch != klp_transition_patch) {
575 mutex_unlock(&klp_mutex);
576 return -EINVAL;
577 }
578
579 klp_force_transition();
580
581 mutex_unlock(&klp_mutex);
582
583 return count;
584}
585
586static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
587static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
588static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
589static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
590static struct attribute *klp_patch_attrs[] = {
591 &enabled_kobj_attr.attr,
592 &transition_kobj_attr.attr,
593 &signal_kobj_attr.attr,
594 &force_kobj_attr.attr,
595 NULL
596};
597
598static void klp_kobj_release_patch(struct kobject *kobj)
599{
600 struct klp_patch *patch;
601
602 patch = container_of(kobj, struct klp_patch, kobj);
603 complete(&patch->finish);
604}
605
606static struct kobj_type klp_ktype_patch = {
607 .release = klp_kobj_release_patch,
608 .sysfs_ops = &kobj_sysfs_ops,
609 .default_attrs = klp_patch_attrs,
610};
611
612static void klp_kobj_release_object(struct kobject *kobj)
613{
614}
615
616static struct kobj_type klp_ktype_object = {
617 .release = klp_kobj_release_object,
618 .sysfs_ops = &kobj_sysfs_ops,
619};
620
621static void klp_kobj_release_func(struct kobject *kobj)
622{
623}
624
625static struct kobj_type klp_ktype_func = {
626 .release = klp_kobj_release_func,
627 .sysfs_ops = &kobj_sysfs_ops,
628};
629
630/*
631 * Free all functions' kobjects in the array up to some limit. When limit is
632 * NULL, all kobjects are freed.
633 */
634static void klp_free_funcs_limited(struct klp_object *obj,
635 struct klp_func *limit)
636{
637 struct klp_func *func;
638
639 for (func = obj->funcs; func->old_name && func != limit; func++)
640 kobject_put(&func->kobj);
641}
642
643/* Clean up when a patched object is unloaded */
644static void klp_free_object_loaded(struct klp_object *obj)
645{
646 struct klp_func *func;
647
648 obj->mod = NULL;
649
650 klp_for_each_func(obj, func)
651 func->old_addr = 0;
652}
653
654/*
655 * Free all objects' kobjects in the array up to some limit. When limit is
656 * NULL, all kobjects are freed.
657 */
658static void klp_free_objects_limited(struct klp_patch *patch,
659 struct klp_object *limit)
660{
661 struct klp_object *obj;
662
663 for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
664 klp_free_funcs_limited(obj, NULL);
665 kobject_put(&obj->kobj);
666 }
667}
668
669static void klp_free_patch(struct klp_patch *patch)
670{
671 klp_free_objects_limited(patch, NULL);
672 if (!list_empty(&patch->list))
673 list_del(&patch->list);
674}
675
676static int klp_init_func(struct klp_object *obj, struct klp_func *func)
677{
678 if (!func->old_name || !func->new_func)
679 return -EINVAL;
680
681 INIT_LIST_HEAD(&func->stack_node);
682 func->patched = false;
683 func->transition = false;
684
685 /* The format for the sysfs directory is <function,sympos> where sympos
686 * is the nth occurrence of this symbol in kallsyms for the patched
687 * object. If the user selects 0 for old_sympos, then 1 will be used
688 * since a unique symbol will be the first occurrence.
689 */
690 return kobject_init_and_add(&func->kobj, &klp_ktype_func,
691 &obj->kobj, "%s,%lu", func->old_name,
692 func->old_sympos ? func->old_sympos : 1);
693}
694
695/* Arches may override this to finish any remaining arch-specific tasks */
696void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
697 struct klp_object *obj)
698{
699}
700
701/* parts of the initialization that is done only when the object is loaded */
702static int klp_init_object_loaded(struct klp_patch *patch,
703 struct klp_object *obj)
704{
705 struct klp_func *func;
706 int ret;
707
708 module_disable_ro(patch->mod);
709 ret = klp_write_object_relocations(patch->mod, obj);
710 if (ret) {
711 module_enable_ro(patch->mod, true);
712 return ret;
713 }
714
715 arch_klp_init_object_loaded(patch, obj);
716 module_enable_ro(patch->mod, true);
717
718 klp_for_each_func(obj, func) {
719 ret = klp_find_object_symbol(obj->name, func->old_name,
720 func->old_sympos,
721 &func->old_addr);
722 if (ret)
723 return ret;
724
725 ret = kallsyms_lookup_size_offset(func->old_addr,
726 &func->old_size, NULL);
727 if (!ret) {
728 pr_err("kallsyms size lookup failed for '%s'\n",
729 func->old_name);
730 return -ENOENT;
731 }
732
733 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
734 &func->new_size, NULL);
735 if (!ret) {
736 pr_err("kallsyms size lookup failed for '%s' replacement\n",
737 func->old_name);
738 return -ENOENT;
739 }
740 }
741
742 return 0;
743}
744
745static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
746{
747 struct klp_func *func;
748 int ret;
749 const char *name;
750
751 if (!obj->funcs)
752 return -EINVAL;
753
754 obj->patched = false;
755 obj->mod = NULL;
756
757 klp_find_object_module(obj);
758
759 name = klp_is_module(obj) ? obj->name : "vmlinux";
760 ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
761 &patch->kobj, "%s", name);
762 if (ret)
763 return ret;
764
765 klp_for_each_func(obj, func) {
766 ret = klp_init_func(obj, func);
767 if (ret)
768 goto free;
769 }
770
771 if (klp_is_object_loaded(obj)) {
772 ret = klp_init_object_loaded(patch, obj);
773 if (ret)
774 goto free;
775 }
776
777 return 0;
778
779free:
780 klp_free_funcs_limited(obj, func);
781 kobject_put(&obj->kobj);
782 return ret;
783}
784
785static int klp_init_patch(struct klp_patch *patch)
786{
787 struct klp_object *obj;
788 int ret;
789
790 if (!patch->objs)
791 return -EINVAL;
792
793 mutex_lock(&klp_mutex);
794
795 patch->enabled = false;
796 init_completion(&patch->finish);
797
798 ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
799 klp_root_kobj, "%s", patch->mod->name);
800 if (ret) {
801 mutex_unlock(&klp_mutex);
802 return ret;
803 }
804
805 klp_for_each_object(patch, obj) {
806 ret = klp_init_object(patch, obj);
807 if (ret)
808 goto free;
809 }
810
811 list_add_tail(&patch->list, &klp_patches);
812
813 mutex_unlock(&klp_mutex);
814
815 return 0;
816
817free:
818 klp_free_objects_limited(patch, obj);
819
820 mutex_unlock(&klp_mutex);
821
822 kobject_put(&patch->kobj);
823 wait_for_completion(&patch->finish);
824
825 return ret;
826}
827
828/**
829 * klp_unregister_patch() - unregisters a patch
830 * @patch: Disabled patch to be unregistered
831 *
832 * Frees the data structures and removes the sysfs interface.
833 *
834 * Return: 0 on success, otherwise error
835 */
836int klp_unregister_patch(struct klp_patch *patch)
837{
838 int ret;
839
840 mutex_lock(&klp_mutex);
841
842 if (!klp_is_patch_registered(patch)) {
843 ret = -EINVAL;
844 goto err;
845 }
846
847 if (patch->enabled) {
848 ret = -EBUSY;
849 goto err;
850 }
851
852 klp_free_patch(patch);
853
854 mutex_unlock(&klp_mutex);
855
856 kobject_put(&patch->kobj);
857 wait_for_completion(&patch->finish);
858
859 return 0;
860err:
861 mutex_unlock(&klp_mutex);
862 return ret;
863}
864EXPORT_SYMBOL_GPL(klp_unregister_patch);
865
866/**
867 * klp_register_patch() - registers a patch
868 * @patch: Patch to be registered
869 *
870 * Initializes the data structure associated with the patch and
871 * creates the sysfs interface.
872 *
873 * There is no need to take the reference on the patch module here. It is done
874 * later when the patch is enabled.
875 *
876 * Return: 0 on success, otherwise error
877 */
878int klp_register_patch(struct klp_patch *patch)
879{
880 if (!patch || !patch->mod)
881 return -EINVAL;
882
883 if (!is_livepatch_module(patch->mod)) {
884 pr_err("module %s is not marked as a livepatch module\n",
885 patch->mod->name);
886 return -EINVAL;
887 }
888
889 if (!klp_initialized())
890 return -ENODEV;
891
892 if (!klp_have_reliable_stack()) {
893 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
894 return -ENOSYS;
895 }
896
897 return klp_init_patch(patch);
898}
899EXPORT_SYMBOL_GPL(klp_register_patch);
900
901/*
902 * Remove parts of patches that touch a given kernel module. The list of
903 * patches processed might be limited. When limit is NULL, all patches
904 * will be handled.
905 */
906static void klp_cleanup_module_patches_limited(struct module *mod,
907 struct klp_patch *limit)
908{
909 struct klp_patch *patch;
910 struct klp_object *obj;
911
912 list_for_each_entry(patch, &klp_patches, list) {
913 if (patch == limit)
914 break;
915
916 klp_for_each_object(patch, obj) {
917 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
918 continue;
919
920 /*
921 * Only unpatch the module if the patch is enabled or
922 * is in transition.
923 */
924 if (patch->enabled || patch == klp_transition_patch) {
925
926 if (patch != klp_transition_patch)
927 klp_pre_unpatch_callback(obj);
928
929 pr_notice("reverting patch '%s' on unloading module '%s'\n",
930 patch->mod->name, obj->mod->name);
931 klp_unpatch_object(obj);
932
933 klp_post_unpatch_callback(obj);
934 }
935
936 klp_free_object_loaded(obj);
937 break;
938 }
939 }
940}
941
942int klp_module_coming(struct module *mod)
943{
944 int ret;
945 struct klp_patch *patch;
946 struct klp_object *obj;
947
948 if (WARN_ON(mod->state != MODULE_STATE_COMING))
949 return -EINVAL;
950
951 mutex_lock(&klp_mutex);
952 /*
953 * Each module has to know that klp_module_coming()
954 * has been called. We never know what module will
955 * get patched by a new patch.
956 */
957 mod->klp_alive = true;
958
959 list_for_each_entry(patch, &klp_patches, list) {
960 klp_for_each_object(patch, obj) {
961 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
962 continue;
963
964 obj->mod = mod;
965
966 ret = klp_init_object_loaded(patch, obj);
967 if (ret) {
968 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
969 patch->mod->name, obj->mod->name, ret);
970 goto err;
971 }
972
973 /*
974 * Only patch the module if the patch is enabled or is
975 * in transition.
976 */
977 if (!patch->enabled && patch != klp_transition_patch)
978 break;
979
980 pr_notice("applying patch '%s' to loading module '%s'\n",
981 patch->mod->name, obj->mod->name);
982
983 ret = klp_pre_patch_callback(obj);
984 if (ret) {
985 pr_warn("pre-patch callback failed for object '%s'\n",
986 obj->name);
987 goto err;
988 }
989
990 ret = klp_patch_object(obj);
991 if (ret) {
992 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
993 patch->mod->name, obj->mod->name, ret);
994
995 klp_post_unpatch_callback(obj);
996 goto err;
997 }
998
999 if (patch != klp_transition_patch)
1000 klp_post_patch_callback(obj);
1001
1002 break;
1003 }
1004 }
1005
1006 mutex_unlock(&klp_mutex);
1007
1008 return 0;
1009
1010err:
1011 /*
1012 * If a patch is unsuccessfully applied, return
1013 * error to the module loader.
1014 */
1015 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1016 patch->mod->name, obj->mod->name, obj->mod->name);
1017 mod->klp_alive = false;
1018 klp_cleanup_module_patches_limited(mod, patch);
1019 mutex_unlock(&klp_mutex);
1020
1021 return ret;
1022}
1023
1024void klp_module_going(struct module *mod)
1025{
1026 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1027 mod->state != MODULE_STATE_COMING))
1028 return;
1029
1030 mutex_lock(&klp_mutex);
1031 /*
1032 * Each module has to know that klp_module_going()
1033 * has been called. We never know what module will
1034 * get patched by a new patch.
1035 */
1036 mod->klp_alive = false;
1037
1038 klp_cleanup_module_patches_limited(mod, NULL);
1039
1040 mutex_unlock(&klp_mutex);
1041}
1042
1043static int __init klp_init(void)
1044{
1045 int ret;
1046
1047 ret = klp_check_compiler_support();
1048 if (ret) {
1049 pr_info("Your compiler is too old; turning off.\n");
1050 return -EINVAL;
1051 }
1052
1053 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1054 if (!klp_root_kobj)
1055 return -ENOMEM;
1056
1057 return 0;
1058}
1059
1060module_init(klp_init);