summaryrefslogtreecommitdiff
path: root/kernel/livepatch/core.c
blob: 782172f073c5ed4bde5318bf96777ee79c618b89 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
/*
 * core.c - Kernel Live Patching Core
 *
 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
 * Copyright (C) 2014 SUSE
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/ftrace.h>
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>

/**
 * struct klp_ops - structure for tracking registered ftrace ops structs
 *
 * A single ftrace_ops is shared between all enabled replacement functions
 * (klp_func structs) which have the same old_addr.  This allows the switch
 * between function versions to happen instantaneously by updating the klp_ops
 * struct's func_stack list.  The winner is the klp_func at the top of the
 * func_stack (front of the list).
 *
 * @node:	node for the global klp_ops list
 * @func_stack:	list head for the stack of klp_func's (active func is on top)
 * @fops:	registered ftrace ops struct
 */
struct klp_ops {
	struct list_head node;
	struct list_head func_stack;
	struct ftrace_ops fops;
};

/*
 * The klp_mutex protects the global lists and state transitions of any
 * structure reachable from them.  References to any structure must be obtained
 * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
 * ensure it gets consistent data).
 */
static DEFINE_MUTEX(klp_mutex);

static LIST_HEAD(klp_patches);
static LIST_HEAD(klp_ops);

static struct kobject *klp_root_kobj;

static struct klp_ops *klp_find_ops(unsigned long old_addr)
{
	struct klp_ops *ops;
	struct klp_func *func;

	list_for_each_entry(ops, &klp_ops, node) {
		func = list_first_entry(&ops->func_stack, struct klp_func,
					stack_node);
		if (func->old_addr == old_addr)
			return ops;
	}

	return NULL;
}

static bool klp_is_module(struct klp_object *obj)
{
	return obj->name;
}

static bool klp_is_object_loaded(struct klp_object *obj)
{
	return !obj->name || obj->mod;
}

/* sets obj->mod if object is not vmlinux and module is found */
static void klp_find_object_module(struct klp_object *obj)
{
	if (!klp_is_module(obj))
		return;

	mutex_lock(&module_mutex);
	/*
	 * We don't need to take a reference on the module here because we have
	 * the klp_mutex, which is also taken by the module notifier.  This
	 * prevents any module from unloading until we release the klp_mutex.
	 */
	obj->mod = find_module(obj->name);
	mutex_unlock(&module_mutex);
}

/* klp_mutex must be held by caller */
static bool klp_is_patch_registered(struct klp_patch *patch)
{
	struct klp_patch *mypatch;

	list_for_each_entry(mypatch, &klp_patches, list)
		if (mypatch == patch)
			return true;

	return false;
}

static bool klp_initialized(void)
{
	return klp_root_kobj;
}

struct klp_find_arg {
	const char *objname;
	const char *name;
	unsigned long addr;
	/*
	 * If count == 0, the symbol was not found. If count == 1, a unique
	 * match was found and addr is set.  If count > 1, there is
	 * unresolvable ambiguity among "count" number of symbols with the same
	 * name in the same object.
	 */
	unsigned long count;
};

static int klp_find_callback(void *data, const char *name,
			     struct module *mod, unsigned long addr)
{
	struct klp_find_arg *args = data;

	if ((mod && !args->objname) || (!mod && args->objname))
		return 0;

	if (strcmp(args->name, name))
		return 0;

	if (args->objname && strcmp(args->objname, mod->name))
		return 0;

	/*
	 * args->addr might be overwritten if another match is found
	 * but klp_find_object_symbol() handles this and only returns the
	 * addr if count == 1.
	 */
	args->addr = addr;
	args->count++;

	return 0;
}

static int klp_find_object_symbol(const char *objname, const char *name,
				  unsigned long *addr)
{
	struct klp_find_arg args = {
		.objname = objname,
		.name = name,
		.addr = 0,
		.count = 0
	};

	kallsyms_on_each_symbol(klp_find_callback, &args);

	if (args.count == 0)
		pr_err("symbol '%s' not found in symbol table\n", name);
	else if (args.count > 1)
		pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n",
		       args.count, name, objname);
	else {
		*addr = args.addr;
		return 0;
	}

	*addr = 0;
	return -EINVAL;
}

struct klp_verify_args {
	const char *name;
	const unsigned long addr;
};

static int klp_verify_callback(void *data, const char *name,
			       struct module *mod, unsigned long addr)
{
	struct klp_verify_args *args = data;

	if (!mod &&
	    !strcmp(args->name, name) &&
	    args->addr == addr)
		return 1;

	return 0;
}

static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
{
	struct klp_verify_args args = {
		.name = name,
		.addr = addr,
	};

	if (kallsyms_on_each_symbol(klp_verify_callback, &args))
		return 0;

	pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
		name, addr);
	return -EINVAL;
}

static int klp_find_verify_func_addr(struct klp_object *obj,
				     struct klp_func *func)
{
	int ret;

#if defined(CONFIG_RANDOMIZE_BASE)
	/* KASLR is enabled, disregard old_addr from user */
	func->old_addr = 0;
#endif

	if (!func->old_addr || klp_is_module(obj))
		ret = klp_find_object_symbol(obj->name, func->old_name,
					     &func->old_addr);
	else
		ret = klp_verify_vmlinux_symbol(func->old_name,
						func->old_addr);

	return ret;
}

/*
 * external symbols are located outside the parent object (where the parent
 * object is either vmlinux or the kmod being patched).
 */
static int klp_find_external_symbol(struct module *pmod, const char *name,
				    unsigned long *addr)
{
	const struct kernel_symbol *sym;

	/* first, check if it's an exported symbol */
	preempt_disable();
	sym = find_symbol(name, NULL, NULL, true, true);
	preempt_enable();
	if (sym) {
		*addr = sym->value;
		return 0;
	}

	/* otherwise check if it's in another .o within the patch module */
	return klp_find_object_symbol(pmod->name, name, addr);
}

static int klp_write_object_relocations(struct module *pmod,
					struct klp_object *obj)
{
	int ret;
	struct klp_reloc *reloc;

	if (WARN_ON(!klp_is_object_loaded(obj)))
		return -EINVAL;

	if (WARN_ON(!obj->relocs))
		return -EINVAL;

	for (reloc = obj->relocs; reloc->name; reloc++) {
		if (!klp_is_module(obj)) {
			ret = klp_verify_vmlinux_symbol(reloc->name,
							reloc->val);
			if (ret)
				return ret;
		} else {
			/* module, reloc->val needs to be discovered */
			if (reloc->external)
				ret = klp_find_external_symbol(pmod,
							       reloc->name,
							       &reloc->val);
			else
				ret = klp_find_object_symbol(obj->mod->name,
							     reloc->name,
							     &reloc->val);
			if (ret)
				return ret;
		}
		ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
					     reloc->val + reloc->addend);
		if (ret) {
			pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
			       reloc->name, reloc->val, ret);
			return ret;
		}
	}

	return 0;
}

static void notrace klp_ftrace_handler(unsigned long ip,
				       unsigned long parent_ip,
				       struct ftrace_ops *fops,
				       struct pt_regs *regs)
{
	struct klp_ops *ops;
	struct klp_func *func;

	ops = container_of(fops, struct klp_ops, fops);

	rcu_read_lock();
	func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
				      stack_node);
	if (WARN_ON_ONCE(!func))
		goto unlock;

	klp_arch_set_pc(regs, (unsigned long)func->new_func);
unlock:
	rcu_read_unlock();
}

static int klp_disable_func(struct klp_func *func)
{
	struct klp_ops *ops;
	int ret;

	if (WARN_ON(func->state != KLP_ENABLED))
		return -EINVAL;

	if (WARN_ON(!func->old_addr))
		return -EINVAL;

	ops = klp_find_ops(func->old_addr);
	if (WARN_ON(!ops))
		return -EINVAL;

	if (list_is_singular(&ops->func_stack)) {
		ret = unregister_ftrace_function(&ops->fops);
		if (ret) {
			pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
			       func->old_name, ret);
			return ret;
		}

		ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
		if (ret)
			pr_warn("function unregister succeeded but failed to clear the filter\n");

		list_del_rcu(&func->stack_node);
		list_del(&ops->node);
		kfree(ops);
	} else {
		list_del_rcu(&func->stack_node);
	}

	func->state = KLP_DISABLED;

	return 0;
}

static int klp_enable_func(struct klp_func *func)
{
	struct klp_ops *ops;
	int ret;

	if (WARN_ON(!func->old_addr))
		return -EINVAL;

	if (WARN_ON(func->state != KLP_DISABLED))
		return -EINVAL;

	ops = klp_find_ops(func->old_addr);
	if (!ops) {
		ops = kzalloc(sizeof(*ops), GFP_KERNEL);
		if (!ops)
			return -ENOMEM;

		ops->fops.func = klp_ftrace_handler;
		ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
				  FTRACE_OPS_FL_DYNAMIC |
				  FTRACE_OPS_FL_IPMODIFY;

		list_add(&ops->node, &klp_ops);

		INIT_LIST_HEAD(&ops->func_stack);
		list_add_rcu(&func->stack_node, &ops->func_stack);

		ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
		if (ret) {
			pr_err("failed to set ftrace filter for function '%s' (%d)\n",
			       func->old_name, ret);
			goto err;
		}

		ret = register_ftrace_function(&ops->fops);
		if (ret) {
			pr_err("failed to register ftrace handler for function '%s' (%d)\n",
			       func->old_name, ret);
			ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
			goto err;
		}


	} else {
		list_add_rcu(&func->stack_node, &ops->func_stack);
	}

	func->state = KLP_ENABLED;

	return 0;

err:
	list_del_rcu(&func->stack_node);
	list_del(&ops->node);
	kfree(ops);
	return ret;
}

static int klp_disable_object(struct klp_object *obj)
{
	struct klp_func *func;
	int ret;

	for (func = obj->funcs; func->old_name; func++) {
		if (func->state != KLP_ENABLED)
			continue;

		ret = klp_disable_func(func);
		if (ret)
			return ret;
	}

	obj->state = KLP_DISABLED;

	return 0;
}

static int klp_enable_object(struct klp_object *obj)
{
	struct klp_func *func;
	int ret;

	if (WARN_ON(obj->state != KLP_DISABLED))
		return -EINVAL;

	if (WARN_ON(!klp_is_object_loaded(obj)))
		return -EINVAL;

	for (func = obj->funcs; func->old_name; func++) {
		ret = klp_enable_func(func);
		if (ret)
			goto unregister;
	}
	obj->state = KLP_ENABLED;

	return 0;

unregister:
	WARN_ON(klp_disable_object(obj));
	return ret;
}

static int __klp_disable_patch(struct klp_patch *patch)
{
	struct klp_object *obj;
	int ret;

	/* enforce stacking: only the last enabled patch can be disabled */
	if (!list_is_last(&patch->list, &klp_patches) &&
	    list_next_entry(patch, list)->state == KLP_ENABLED)
		return -EBUSY;

	pr_notice("disabling patch '%s'\n", patch->mod->name);

	for (obj = patch->objs; obj->funcs; obj++) {
		if (obj->state != KLP_ENABLED)
			continue;

		ret = klp_disable_object(obj);
		if (ret)
			return ret;
	}

	patch->state = KLP_DISABLED;

	return 0;
}

/**
 * klp_disable_patch() - disables a registered patch
 * @patch:	The registered, enabled patch to be disabled
 *
 * Unregisters the patched functions from ftrace.
 *
 * Return: 0 on success, otherwise error
 */
int klp_disable_patch(struct klp_patch *patch)
{
	int ret;

	mutex_lock(&klp_mutex);

	if (!klp_is_patch_registered(patch)) {
		ret = -EINVAL;
		goto err;
	}

	if (patch->state == KLP_DISABLED) {
		ret = -EINVAL;
		goto err;
	}

	ret = __klp_disable_patch(patch);

err:
	mutex_unlock(&klp_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(klp_disable_patch);

static int __klp_enable_patch(struct klp_patch *patch)
{
	struct klp_object *obj;
	int ret;

	if (WARN_ON(patch->state != KLP_DISABLED))
		return -EINVAL;

	/* enforce stacking: only the first disabled patch can be enabled */
	if (patch->list.prev != &klp_patches &&
	    list_prev_entry(patch, list)->state == KLP_DISABLED)
		return -EBUSY;

	pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
	add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);

	pr_notice("enabling patch '%s'\n", patch->mod->name);

	for (obj = patch->objs; obj->funcs; obj++) {
		klp_find_object_module(obj);

		if (!klp_is_object_loaded(obj))
			continue;

		ret = klp_enable_object(obj);
		if (ret)
			goto unregister;
	}

	patch->state = KLP_ENABLED;

	return 0;

unregister:
	WARN_ON(__klp_disable_patch(patch));
	return ret;
}

/**
 * klp_enable_patch() - enables a registered patch
 * @patch:	The registered, disabled patch to be enabled
 *
 * Performs the needed symbol lookups and code relocations,
 * then registers the patched functions with ftrace.
 *
 * Return: 0 on success, otherwise error
 */
int klp_enable_patch(struct klp_patch *patch)
{
	int ret;

	mutex_lock(&klp_mutex);

	if (!klp_is_patch_registered(patch)) {
		ret = -EINVAL;
		goto err;
	}

	ret = __klp_enable_patch(patch);

err:
	mutex_unlock(&klp_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(klp_enable_patch);

/*
 * Sysfs Interface
 *
 * /sys/kernel/livepatch
 * /sys/kernel/livepatch/<patch>
 * /sys/kernel/livepatch/<patch>/enabled
 * /sys/kernel/livepatch/<patch>/<object>
 * /sys/kernel/livepatch/<patch>/<object>/<func>
 */

static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
			     const char *buf, size_t count)
{
	struct klp_patch *patch;
	int ret;
	unsigned long val;

	ret = kstrtoul(buf, 10, &val);
	if (ret)
		return -EINVAL;

	if (val != KLP_DISABLED && val != KLP_ENABLED)
		return -EINVAL;

	patch = container_of(kobj, struct klp_patch, kobj);

	mutex_lock(&klp_mutex);

	if (val == patch->state) {
		/* already in requested state */
		ret = -EINVAL;
		goto err;
	}

	if (val == KLP_ENABLED) {
		ret = __klp_enable_patch(patch);
		if (ret)
			goto err;
	} else {
		ret = __klp_disable_patch(patch);
		if (ret)
			goto err;
	}

	mutex_unlock(&klp_mutex);

	return count;

err:
	mutex_unlock(&klp_mutex);
	return ret;
}

static ssize_t enabled_show(struct kobject *kobj,
			    struct kobj_attribute *attr, char *buf)
{
	struct klp_patch *patch;

	patch = container_of(kobj, struct klp_patch, kobj);
	return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
}

static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
static struct attribute *klp_patch_attrs[] = {
	&enabled_kobj_attr.attr,
	NULL
};

static void klp_kobj_release_patch(struct kobject *kobj)
{
	/*
	 * Once we have a consistency model we'll need to module_put() the
	 * patch module here.  See klp_register_patch() for more details.
	 */
}

static struct kobj_type klp_ktype_patch = {
	.release = klp_kobj_release_patch,
	.sysfs_ops = &kobj_sysfs_ops,
	.default_attrs = klp_patch_attrs,
};

static void klp_kobj_release_func(struct kobject *kobj)
{
}

static struct kobj_type klp_ktype_func = {
	.release = klp_kobj_release_func,
	.sysfs_ops = &kobj_sysfs_ops,
};

/*
 * Free all functions' kobjects in the array up to some limit. When limit is
 * NULL, all kobjects are freed.
 */
static void klp_free_funcs_limited(struct klp_object *obj,
				   struct klp_func *limit)
{
	struct klp_func *func;

	for (func = obj->funcs; func->old_name && func != limit; func++)
		kobject_put(&func->kobj);
}

/* Clean up when a patched object is unloaded */
static void klp_free_object_loaded(struct klp_object *obj)
{
	struct klp_func *func;

	obj->mod = NULL;

	for (func = obj->funcs; func->old_name; func++)
		func->old_addr = 0;
}

/*
 * Free all objects' kobjects in the array up to some limit. When limit is
 * NULL, all kobjects are freed.
 */
static void klp_free_objects_limited(struct klp_patch *patch,
				     struct klp_object *limit)
{
	struct klp_object *obj;

	for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
		klp_free_funcs_limited(obj, NULL);
		kobject_put(obj->kobj);
	}
}

static void klp_free_patch(struct klp_patch *patch)
{
	klp_free_objects_limited(patch, NULL);
	if (!list_empty(&patch->list))
		list_del(&patch->list);
	kobject_put(&patch->kobj);
}

static int klp_init_func(struct klp_object *obj, struct klp_func *func)
{
	INIT_LIST_HEAD(&func->stack_node);
	func->state = KLP_DISABLED;

	return kobject_init_and_add(&func->kobj, &klp_ktype_func,
				    obj->kobj, "%s", func->old_name);
}

/* parts of the initialization that is done only when the object is loaded */
static int klp_init_object_loaded(struct klp_patch *patch,
				  struct klp_object *obj)
{
	struct klp_func *func;
	int ret;

	if (obj->relocs) {
		ret = klp_write_object_relocations(patch->mod, obj);
		if (ret)
			return ret;
	}

	for (func = obj->funcs; func->old_name; func++) {
		ret = klp_find_verify_func_addr(obj, func);
		if (ret)
			return ret;
	}

	return 0;
}

static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
{
	struct klp_func *func;
	int ret;
	const char *name;

	if (!obj->funcs)
		return -EINVAL;

	obj->state = KLP_DISABLED;

	klp_find_object_module(obj);

	name = klp_is_module(obj) ? obj->name : "vmlinux";
	obj->kobj = kobject_create_and_add(name, &patch->kobj);
	if (!obj->kobj)
		return -ENOMEM;

	for (func = obj->funcs; func->old_name; func++) {
		ret = klp_init_func(obj, func);
		if (ret)
			goto free;
	}

	if (klp_is_object_loaded(obj)) {
		ret = klp_init_object_loaded(patch, obj);
		if (ret)
			goto free;
	}

	return 0;

free:
	klp_free_funcs_limited(obj, func);
	kobject_put(obj->kobj);
	return ret;
}

static int klp_init_patch(struct klp_patch *patch)
{
	struct klp_object *obj;
	int ret;

	if (!patch->objs)
		return -EINVAL;

	mutex_lock(&klp_mutex);

	patch->state = KLP_DISABLED;

	ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
				   klp_root_kobj, "%s", patch->mod->name);
	if (ret)
		goto unlock;

	for (obj = patch->objs; obj->funcs; obj++) {
		ret = klp_init_object(patch, obj);
		if (ret)
			goto free;
	}

	list_add_tail(&patch->list, &klp_patches);

	mutex_unlock(&klp_mutex);

	return 0;

free:
	klp_free_objects_limited(patch, obj);
	kobject_put(&patch->kobj);
unlock:
	mutex_unlock(&klp_mutex);
	return ret;
}

/**
 * klp_unregister_patch() - unregisters a patch
 * @patch:	Disabled patch to be unregistered
 *
 * Frees the data structures and removes the sysfs interface.
 *
 * Return: 0 on success, otherwise error
 */
int klp_unregister_patch(struct klp_patch *patch)
{
	int ret = 0;

	mutex_lock(&klp_mutex);

	if (!klp_is_patch_registered(patch)) {
		ret = -EINVAL;
		goto out;
	}

	if (patch->state == KLP_ENABLED) {
		ret = -EBUSY;
		goto out;
	}

	klp_free_patch(patch);

out:
	mutex_unlock(&klp_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(klp_unregister_patch);

/**
 * klp_register_patch() - registers a patch
 * @patch:	Patch to be registered
 *
 * Initializes the data structure associated with the patch and
 * creates the sysfs interface.
 *
 * Return: 0 on success, otherwise error
 */
int klp_register_patch(struct klp_patch *patch)
{
	int ret;

	if (!klp_initialized())
		return -ENODEV;

	if (!patch || !patch->mod)
		return -EINVAL;

	/*
	 * A reference is taken on the patch module to prevent it from being
	 * unloaded.  Right now, we don't allow patch modules to unload since
	 * there is currently no method to determine if a thread is still
	 * running in the patched code contained in the patch module once
	 * the ftrace registration is successful.
	 */
	if (!try_module_get(patch->mod))
		return -ENODEV;

	ret = klp_init_patch(patch);
	if (ret)
		module_put(patch->mod);

	return ret;
}
EXPORT_SYMBOL_GPL(klp_register_patch);

static void klp_module_notify_coming(struct klp_patch *patch,
				     struct klp_object *obj)
{
	struct module *pmod = patch->mod;
	struct module *mod = obj->mod;
	int ret;

	ret = klp_init_object_loaded(patch, obj);
	if (ret)
		goto err;

	if (patch->state == KLP_DISABLED)
		return;

	pr_notice("applying patch '%s' to loading module '%s'\n",
		  pmod->name, mod->name);

	ret = klp_enable_object(obj);
	if (!ret)
		return;

err:
	pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
		pmod->name, mod->name, ret);
}

static void klp_module_notify_going(struct klp_patch *patch,
				    struct klp_object *obj)
{
	struct module *pmod = patch->mod;
	struct module *mod = obj->mod;
	int ret;

	if (patch->state == KLP_DISABLED)
		goto disabled;

	pr_notice("reverting patch '%s' on unloading module '%s'\n",
		  pmod->name, mod->name);

	ret = klp_disable_object(obj);
	if (ret)
		pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
			pmod->name, mod->name, ret);

disabled:
	klp_free_object_loaded(obj);
}

static int klp_module_notify(struct notifier_block *nb, unsigned long action,
			     void *data)
{
	struct module *mod = data;
	struct klp_patch *patch;
	struct klp_object *obj;

	if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
		return 0;

	mutex_lock(&klp_mutex);

	list_for_each_entry(patch, &klp_patches, list) {
		for (obj = patch->objs; obj->funcs; obj++) {
			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
				continue;

			if (action == MODULE_STATE_COMING) {
				obj->mod = mod;
				klp_module_notify_coming(patch, obj);
			} else /* MODULE_STATE_GOING */
				klp_module_notify_going(patch, obj);

			break;
		}
	}

	mutex_unlock(&klp_mutex);

	return 0;
}

static struct notifier_block klp_module_nb = {
	.notifier_call = klp_module_notify,
	.priority = INT_MIN+1, /* called late but before ftrace notifier */
};

static int klp_init(void)
{
	int ret;

	ret = klp_check_compiler_support();
	if (ret) {
		pr_info("Your compiler is too old; turning off.\n");
		return -EINVAL;
	}

	ret = register_module_notifier(&klp_module_nb);
	if (ret)
		return ret;

	klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
	if (!klp_root_kobj) {
		ret = -ENOMEM;
		goto unregister;
	}

	return 0;

unregister:
	unregister_module_notifier(&klp_module_nb);
	return ret;
}

module_init(klp_init);