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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/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);
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 <linux/elf.h>
32#include <linux/moduleloader.h>
33#include <asm/cacheflush.h>
34
35/**
36 * struct klp_ops - structure for tracking registered ftrace ops structs
37 *
38 * A single ftrace_ops is shared between all enabled replacement functions
39 * (klp_func structs) which have the same old_addr. This allows the switch
40 * between function versions to happen instantaneously by updating the klp_ops
41 * struct's func_stack list. The winner is the klp_func at the top of the
42 * func_stack (front of the list).
43 *
44 * @node: node for the global klp_ops list
45 * @func_stack: list head for the stack of klp_func's (active func is on top)
46 * @fops: registered ftrace ops struct
47 */
48struct klp_ops {
49 struct list_head node;
50 struct list_head func_stack;
51 struct ftrace_ops fops;
52};
53
54/*
55 * The klp_mutex protects the global lists and state transitions of any
56 * structure reachable from them. References to any structure must be obtained
57 * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
58 * ensure it gets consistent data).
59 */
60static DEFINE_MUTEX(klp_mutex);
61
62static LIST_HEAD(klp_patches);
63static LIST_HEAD(klp_ops);
64
65static struct kobject *klp_root_kobj;
66
67static struct klp_ops *klp_find_ops(unsigned long old_addr)
68{
69 struct klp_ops *ops;
70 struct klp_func *func;
71
72 list_for_each_entry(ops, &klp_ops, node) {
73 func = list_first_entry(&ops->func_stack, struct klp_func,
74 stack_node);
75 if (func->old_addr == old_addr)
76 return ops;
77 }
78
79 return NULL;
80}
81
82static bool klp_is_module(struct klp_object *obj)
83{
84 return obj->name;
85}
86
87static bool klp_is_object_loaded(struct klp_object *obj)
88{
89 return !obj->name || obj->mod;
90}
91
92/* sets obj->mod if object is not vmlinux and module is found */
93static void klp_find_object_module(struct klp_object *obj)
94{
95 struct module *mod;
96
97 if (!klp_is_module(obj))
98 return;
99
100 mutex_lock(&module_mutex);
101 /*
102 * We do not want to block removal of patched modules and therefore
103 * we do not take a reference here. The patches are removed by
104 * klp_module_going() instead.
105 */
106 mod = find_module(obj->name);
107 /*
108 * Do not mess work of klp_module_coming() and klp_module_going().
109 * Note that the patch might still be needed before klp_module_going()
110 * is called. Module functions can be called even in the GOING state
111 * until mod->exit() finishes. This is especially important for
112 * patches that modify semantic of the functions.
113 */
114 if (mod && mod->klp_alive)
115 obj->mod = mod;
116
117 mutex_unlock(&module_mutex);
118}
119
120/* klp_mutex must be held by caller */
121static bool klp_is_patch_registered(struct klp_patch *patch)
122{
123 struct klp_patch *mypatch;
124
125 list_for_each_entry(mypatch, &klp_patches, list)
126 if (mypatch == patch)
127 return true;
128
129 return false;
130}
131
132static bool klp_initialized(void)
133{
134 return !!klp_root_kobj;
135}
136
137struct klp_find_arg {
138 const char *objname;
139 const char *name;
140 unsigned long addr;
141 unsigned long count;
142 unsigned long pos;
143};
144
145static int klp_find_callback(void *data, const char *name,
146 struct module *mod, unsigned long addr)
147{
148 struct klp_find_arg *args = data;
149
150 if ((mod && !args->objname) || (!mod && args->objname))
151 return 0;
152
153 if (strcmp(args->name, name))
154 return 0;
155
156 if (args->objname && strcmp(args->objname, mod->name))
157 return 0;
158
159 args->addr = addr;
160 args->count++;
161
162 /*
163 * Finish the search when the symbol is found for the desired position
164 * or the position is not defined for a non-unique symbol.
165 */
166 if ((args->pos && (args->count == args->pos)) ||
167 (!args->pos && (args->count > 1)))
168 return 1;
169
170 return 0;
171}
172
173static int klp_find_object_symbol(const char *objname, const char *name,
174 unsigned long sympos, unsigned long *addr)
175{
176 struct klp_find_arg args = {
177 .objname = objname,
178 .name = name,
179 .addr = 0,
180 .count = 0,
181 .pos = sympos,
182 };
183
184 mutex_lock(&module_mutex);
185 kallsyms_on_each_symbol(klp_find_callback, &args);
186 mutex_unlock(&module_mutex);
187
188 /*
189 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
190 * otherwise ensure the symbol position count matches sympos.
191 */
192 if (args.addr == 0)
193 pr_err("symbol '%s' not found in symbol table\n", name);
194 else if (args.count > 1 && sympos == 0) {
195 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
196 name, objname);
197 } else if (sympos != args.count && sympos > 0) {
198 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
199 sympos, name, objname ? objname : "vmlinux");
200 } else {
201 *addr = args.addr;
202 return 0;
203 }
204
205 *addr = 0;
206 return -EINVAL;
207}
208
209static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
210{
211 int i, cnt, vmlinux, ret;
212 char objname[MODULE_NAME_LEN];
213 char symname[KSYM_NAME_LEN];
214 char *strtab = pmod->core_kallsyms.strtab;
215 Elf_Rela *relas;
216 Elf_Sym *sym;
217 unsigned long sympos, addr;
218
219 /*
220 * Since the field widths for objname and symname in the sscanf()
221 * call are hard-coded and correspond to MODULE_NAME_LEN and
222 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
223 * and KSYM_NAME_LEN have the values we expect them to have.
224 *
225 * Because the value of MODULE_NAME_LEN can differ among architectures,
226 * we use the smallest/strictest upper bound possible (56, based on
227 * the current definition of MODULE_NAME_LEN) to prevent overflows.
228 */
229 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
230
231 relas = (Elf_Rela *) relasec->sh_addr;
232 /* For each rela in this klp relocation section */
233 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
234 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
235 if (sym->st_shndx != SHN_LIVEPATCH) {
236 pr_err("symbol %s is not marked as a livepatch symbol",
237 strtab + sym->st_name);
238 return -EINVAL;
239 }
240
241 /* Format: .klp.sym.objname.symname,sympos */
242 cnt = sscanf(strtab + sym->st_name,
243 ".klp.sym.%55[^.].%127[^,],%lu",
244 objname, symname, &sympos);
245 if (cnt != 3) {
246 pr_err("symbol %s has an incorrectly formatted name",
247 strtab + sym->st_name);
248 return -EINVAL;
249 }
250
251 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
252 vmlinux = !strcmp(objname, "vmlinux");
253 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
254 symname, sympos, &addr);
255 if (ret)
256 return ret;
257
258 sym->st_value = addr;
259 }
260
261 return 0;
262}
263
264static int klp_write_object_relocations(struct module *pmod,
265 struct klp_object *obj)
266{
267 int i, cnt, ret = 0;
268 const char *objname, *secname;
269 char sec_objname[MODULE_NAME_LEN];
270 Elf_Shdr *sec;
271
272 if (WARN_ON(!klp_is_object_loaded(obj)))
273 return -EINVAL;
274
275 objname = klp_is_module(obj) ? obj->name : "vmlinux";
276
277 /* For each klp relocation section */
278 for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
279 sec = pmod->klp_info->sechdrs + i;
280 secname = pmod->klp_info->secstrings + sec->sh_name;
281 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
282 continue;
283
284 /*
285 * Format: .klp.rela.sec_objname.section_name
286 * See comment in klp_resolve_symbols() for an explanation
287 * of the selected field width value.
288 */
289 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
290 if (cnt != 1) {
291 pr_err("section %s has an incorrectly formatted name",
292 secname);
293 ret = -EINVAL;
294 break;
295 }
296
297 if (strcmp(objname, sec_objname))
298 continue;
299
300 ret = klp_resolve_symbols(sec, pmod);
301 if (ret)
302 break;
303
304 ret = apply_relocate_add(pmod->klp_info->sechdrs,
305 pmod->core_kallsyms.strtab,
306 pmod->klp_info->symndx, i, pmod);
307 if (ret)
308 break;
309 }
310
311 return ret;
312}
313
314static void notrace klp_ftrace_handler(unsigned long ip,
315 unsigned long parent_ip,
316 struct ftrace_ops *fops,
317 struct pt_regs *regs)
318{
319 struct klp_ops *ops;
320 struct klp_func *func;
321
322 ops = container_of(fops, struct klp_ops, fops);
323
324 rcu_read_lock();
325 func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
326 stack_node);
327 if (WARN_ON_ONCE(!func))
328 goto unlock;
329
330 klp_arch_set_pc(regs, (unsigned long)func->new_func);
331unlock:
332 rcu_read_unlock();
333}
334
335/*
336 * Convert a function address into the appropriate ftrace location.
337 *
338 * Usually this is just the address of the function, but on some architectures
339 * it's more complicated so allow them to provide a custom behaviour.
340 */
341#ifndef klp_get_ftrace_location
342static unsigned long klp_get_ftrace_location(unsigned long faddr)
343{
344 return faddr;
345}
346#endif
347
348static void klp_disable_func(struct klp_func *func)
349{
350 struct klp_ops *ops;
351
352 if (WARN_ON(func->state != KLP_ENABLED))
353 return;
354 if (WARN_ON(!func->old_addr))
355 return;
356
357 ops = klp_find_ops(func->old_addr);
358 if (WARN_ON(!ops))
359 return;
360
361 if (list_is_singular(&ops->func_stack)) {
362 unsigned long ftrace_loc;
363
364 ftrace_loc = klp_get_ftrace_location(func->old_addr);
365 if (WARN_ON(!ftrace_loc))
366 return;
367
368 WARN_ON(unregister_ftrace_function(&ops->fops));
369 WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
370
371 list_del_rcu(&func->stack_node);
372 list_del(&ops->node);
373 kfree(ops);
374 } else {
375 list_del_rcu(&func->stack_node);
376 }
377
378 func->state = KLP_DISABLED;
379}
380
381static int klp_enable_func(struct klp_func *func)
382{
383 struct klp_ops *ops;
384 int ret;
385
386 if (WARN_ON(!func->old_addr))
387 return -EINVAL;
388
389 if (WARN_ON(func->state != KLP_DISABLED))
390 return -EINVAL;
391
392 ops = klp_find_ops(func->old_addr);
393 if (!ops) {
394 unsigned long ftrace_loc;
395
396 ftrace_loc = klp_get_ftrace_location(func->old_addr);
397 if (!ftrace_loc) {
398 pr_err("failed to find location for function '%s'\n",
399 func->old_name);
400 return -EINVAL;
401 }
402
403 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
404 if (!ops)
405 return -ENOMEM;
406
407 ops->fops.func = klp_ftrace_handler;
408 ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
409 FTRACE_OPS_FL_DYNAMIC |
410 FTRACE_OPS_FL_IPMODIFY;
411
412 list_add(&ops->node, &klp_ops);
413
414 INIT_LIST_HEAD(&ops->func_stack);
415 list_add_rcu(&func->stack_node, &ops->func_stack);
416
417 ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
418 if (ret) {
419 pr_err("failed to set ftrace filter for function '%s' (%d)\n",
420 func->old_name, ret);
421 goto err;
422 }
423
424 ret = register_ftrace_function(&ops->fops);
425 if (ret) {
426 pr_err("failed to register ftrace handler for function '%s' (%d)\n",
427 func->old_name, ret);
428 ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
429 goto err;
430 }
431
432
433 } else {
434 list_add_rcu(&func->stack_node, &ops->func_stack);
435 }
436
437 func->state = KLP_ENABLED;
438
439 return 0;
440
441err:
442 list_del_rcu(&func->stack_node);
443 list_del(&ops->node);
444 kfree(ops);
445 return ret;
446}
447
448static void klp_disable_object(struct klp_object *obj)
449{
450 struct klp_func *func;
451
452 klp_for_each_func(obj, func)
453 if (func->state == KLP_ENABLED)
454 klp_disable_func(func);
455
456 obj->state = KLP_DISABLED;
457}
458
459static int klp_enable_object(struct klp_object *obj)
460{
461 struct klp_func *func;
462 int ret;
463
464 if (WARN_ON(obj->state != KLP_DISABLED))
465 return -EINVAL;
466
467 if (WARN_ON(!klp_is_object_loaded(obj)))
468 return -EINVAL;
469
470 klp_for_each_func(obj, func) {
471 ret = klp_enable_func(func);
472 if (ret) {
473 klp_disable_object(obj);
474 return ret;
475 }
476 }
477 obj->state = KLP_ENABLED;
478
479 return 0;
480}
481
482static int __klp_disable_patch(struct klp_patch *patch)
483{
484 struct klp_object *obj;
485
486 /* enforce stacking: only the last enabled patch can be disabled */
487 if (!list_is_last(&patch->list, &klp_patches) &&
488 list_next_entry(patch, list)->state == KLP_ENABLED)
489 return -EBUSY;
490
491 pr_notice("disabling patch '%s'\n", patch->mod->name);
492
493 klp_for_each_object(patch, obj) {
494 if (obj->state == KLP_ENABLED)
495 klp_disable_object(obj);
496 }
497
498 patch->state = KLP_DISABLED;
499
500 return 0;
501}
502
503/**
504 * klp_disable_patch() - disables a registered patch
505 * @patch: The registered, enabled patch to be disabled
506 *
507 * Unregisters the patched functions from ftrace.
508 *
509 * Return: 0 on success, otherwise error
510 */
511int klp_disable_patch(struct klp_patch *patch)
512{
513 int ret;
514
515 mutex_lock(&klp_mutex);
516
517 if (!klp_is_patch_registered(patch)) {
518 ret = -EINVAL;
519 goto err;
520 }
521
522 if (patch->state == KLP_DISABLED) {
523 ret = -EINVAL;
524 goto err;
525 }
526
527 ret = __klp_disable_patch(patch);
528
529err:
530 mutex_unlock(&klp_mutex);
531 return ret;
532}
533EXPORT_SYMBOL_GPL(klp_disable_patch);
534
535static int __klp_enable_patch(struct klp_patch *patch)
536{
537 struct klp_object *obj;
538 int ret;
539
540 if (WARN_ON(patch->state != KLP_DISABLED))
541 return -EINVAL;
542
543 /* enforce stacking: only the first disabled patch can be enabled */
544 if (patch->list.prev != &klp_patches &&
545 list_prev_entry(patch, list)->state == KLP_DISABLED)
546 return -EBUSY;
547
548 pr_notice("enabling patch '%s'\n", patch->mod->name);
549
550 klp_for_each_object(patch, obj) {
551 if (!klp_is_object_loaded(obj))
552 continue;
553
554 ret = klp_enable_object(obj);
555 if (ret)
556 goto unregister;
557 }
558
559 patch->state = KLP_ENABLED;
560
561 return 0;
562
563unregister:
564 WARN_ON(__klp_disable_patch(patch));
565 return ret;
566}
567
568/**
569 * klp_enable_patch() - enables a registered patch
570 * @patch: The registered, disabled patch to be enabled
571 *
572 * Performs the needed symbol lookups and code relocations,
573 * then registers the patched functions with ftrace.
574 *
575 * Return: 0 on success, otherwise error
576 */
577int klp_enable_patch(struct klp_patch *patch)
578{
579 int ret;
580
581 mutex_lock(&klp_mutex);
582
583 if (!klp_is_patch_registered(patch)) {
584 ret = -EINVAL;
585 goto err;
586 }
587
588 ret = __klp_enable_patch(patch);
589
590err:
591 mutex_unlock(&klp_mutex);
592 return ret;
593}
594EXPORT_SYMBOL_GPL(klp_enable_patch);
595
596/*
597 * Sysfs Interface
598 *
599 * /sys/kernel/livepatch
600 * /sys/kernel/livepatch/<patch>
601 * /sys/kernel/livepatch/<patch>/enabled
602 * /sys/kernel/livepatch/<patch>/<object>
603 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
604 */
605
606static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
607 const char *buf, size_t count)
608{
609 struct klp_patch *patch;
610 int ret;
611 unsigned long val;
612
613 ret = kstrtoul(buf, 10, &val);
614 if (ret)
615 return -EINVAL;
616
617 if (val != KLP_DISABLED && val != KLP_ENABLED)
618 return -EINVAL;
619
620 patch = container_of(kobj, struct klp_patch, kobj);
621
622 mutex_lock(&klp_mutex);
623
624 if (val == patch->state) {
625 /* already in requested state */
626 ret = -EINVAL;
627 goto err;
628 }
629
630 if (val == KLP_ENABLED) {
631 ret = __klp_enable_patch(patch);
632 if (ret)
633 goto err;
634 } else {
635 ret = __klp_disable_patch(patch);
636 if (ret)
637 goto err;
638 }
639
640 mutex_unlock(&klp_mutex);
641
642 return count;
643
644err:
645 mutex_unlock(&klp_mutex);
646 return ret;
647}
648
649static ssize_t enabled_show(struct kobject *kobj,
650 struct kobj_attribute *attr, char *buf)
651{
652 struct klp_patch *patch;
653
654 patch = container_of(kobj, struct klp_patch, kobj);
655 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
656}
657
658static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
659static struct attribute *klp_patch_attrs[] = {
660 &enabled_kobj_attr.attr,
661 NULL
662};
663
664static void klp_kobj_release_patch(struct kobject *kobj)
665{
666 /*
667 * Once we have a consistency model we'll need to module_put() the
668 * patch module here. See klp_register_patch() for more details.
669 */
670}
671
672static struct kobj_type klp_ktype_patch = {
673 .release = klp_kobj_release_patch,
674 .sysfs_ops = &kobj_sysfs_ops,
675 .default_attrs = klp_patch_attrs,
676};
677
678static void klp_kobj_release_object(struct kobject *kobj)
679{
680}
681
682static struct kobj_type klp_ktype_object = {
683 .release = klp_kobj_release_object,
684 .sysfs_ops = &kobj_sysfs_ops,
685};
686
687static void klp_kobj_release_func(struct kobject *kobj)
688{
689}
690
691static struct kobj_type klp_ktype_func = {
692 .release = klp_kobj_release_func,
693 .sysfs_ops = &kobj_sysfs_ops,
694};
695
696/*
697 * Free all functions' kobjects in the array up to some limit. When limit is
698 * NULL, all kobjects are freed.
699 */
700static void klp_free_funcs_limited(struct klp_object *obj,
701 struct klp_func *limit)
702{
703 struct klp_func *func;
704
705 for (func = obj->funcs; func->old_name && func != limit; func++)
706 kobject_put(&func->kobj);
707}
708
709/* Clean up when a patched object is unloaded */
710static void klp_free_object_loaded(struct klp_object *obj)
711{
712 struct klp_func *func;
713
714 obj->mod = NULL;
715
716 klp_for_each_func(obj, func)
717 func->old_addr = 0;
718}
719
720/*
721 * Free all objects' kobjects in the array up to some limit. When limit is
722 * NULL, all kobjects are freed.
723 */
724static void klp_free_objects_limited(struct klp_patch *patch,
725 struct klp_object *limit)
726{
727 struct klp_object *obj;
728
729 for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
730 klp_free_funcs_limited(obj, NULL);
731 kobject_put(&obj->kobj);
732 }
733}
734
735static void klp_free_patch(struct klp_patch *patch)
736{
737 klp_free_objects_limited(patch, NULL);
738 if (!list_empty(&patch->list))
739 list_del(&patch->list);
740 kobject_put(&patch->kobj);
741}
742
743static int klp_init_func(struct klp_object *obj, struct klp_func *func)
744{
745 if (!func->old_name || !func->new_func)
746 return -EINVAL;
747
748 INIT_LIST_HEAD(&func->stack_node);
749 func->state = KLP_DISABLED;
750
751 /* The format for the sysfs directory is <function,sympos> where sympos
752 * is the nth occurrence of this symbol in kallsyms for the patched
753 * object. If the user selects 0 for old_sympos, then 1 will be used
754 * since a unique symbol will be the first occurrence.
755 */
756 return kobject_init_and_add(&func->kobj, &klp_ktype_func,
757 &obj->kobj, "%s,%lu", func->old_name,
758 func->old_sympos ? func->old_sympos : 1);
759}
760
761/* Arches may override this to finish any remaining arch-specific tasks */
762void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
763 struct klp_object *obj)
764{
765}
766
767/* parts of the initialization that is done only when the object is loaded */
768static int klp_init_object_loaded(struct klp_patch *patch,
769 struct klp_object *obj)
770{
771 struct klp_func *func;
772 int ret;
773
774 module_disable_ro(patch->mod);
775 ret = klp_write_object_relocations(patch->mod, obj);
776 if (ret) {
777 module_enable_ro(patch->mod, true);
778 return ret;
779 }
780
781 arch_klp_init_object_loaded(patch, obj);
782 module_enable_ro(patch->mod, true);
783
784 klp_for_each_func(obj, func) {
785 ret = klp_find_object_symbol(obj->name, func->old_name,
786 func->old_sympos,
787 &func->old_addr);
788 if (ret)
789 return ret;
790 }
791
792 return 0;
793}
794
795static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
796{
797 struct klp_func *func;
798 int ret;
799 const char *name;
800
801 if (!obj->funcs)
802 return -EINVAL;
803
804 obj->state = KLP_DISABLED;
805 obj->mod = NULL;
806
807 klp_find_object_module(obj);
808
809 name = klp_is_module(obj) ? obj->name : "vmlinux";
810 ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
811 &patch->kobj, "%s", name);
812 if (ret)
813 return ret;
814
815 klp_for_each_func(obj, func) {
816 ret = klp_init_func(obj, func);
817 if (ret)
818 goto free;
819 }
820
821 if (klp_is_object_loaded(obj)) {
822 ret = klp_init_object_loaded(patch, obj);
823 if (ret)
824 goto free;
825 }
826
827 return 0;
828
829free:
830 klp_free_funcs_limited(obj, func);
831 kobject_put(&obj->kobj);
832 return ret;
833}
834
835static int klp_init_patch(struct klp_patch *patch)
836{
837 struct klp_object *obj;
838 int ret;
839
840 if (!patch->objs)
841 return -EINVAL;
842
843 mutex_lock(&klp_mutex);
844
845 patch->state = KLP_DISABLED;
846
847 ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
848 klp_root_kobj, "%s", patch->mod->name);
849 if (ret)
850 goto unlock;
851
852 klp_for_each_object(patch, obj) {
853 ret = klp_init_object(patch, obj);
854 if (ret)
855 goto free;
856 }
857
858 list_add_tail(&patch->list, &klp_patches);
859
860 mutex_unlock(&klp_mutex);
861
862 return 0;
863
864free:
865 klp_free_objects_limited(patch, obj);
866 kobject_put(&patch->kobj);
867unlock:
868 mutex_unlock(&klp_mutex);
869 return ret;
870}
871
872/**
873 * klp_unregister_patch() - unregisters a patch
874 * @patch: Disabled patch to be unregistered
875 *
876 * Frees the data structures and removes the sysfs interface.
877 *
878 * Return: 0 on success, otherwise error
879 */
880int klp_unregister_patch(struct klp_patch *patch)
881{
882 int ret = 0;
883
884 mutex_lock(&klp_mutex);
885
886 if (!klp_is_patch_registered(patch)) {
887 ret = -EINVAL;
888 goto out;
889 }
890
891 if (patch->state == KLP_ENABLED) {
892 ret = -EBUSY;
893 goto out;
894 }
895
896 klp_free_patch(patch);
897
898out:
899 mutex_unlock(&klp_mutex);
900 return ret;
901}
902EXPORT_SYMBOL_GPL(klp_unregister_patch);
903
904/**
905 * klp_register_patch() - registers a patch
906 * @patch: Patch to be registered
907 *
908 * Initializes the data structure associated with the patch and
909 * creates the sysfs interface.
910 *
911 * Return: 0 on success, otherwise error
912 */
913int klp_register_patch(struct klp_patch *patch)
914{
915 int ret;
916
917 if (!patch || !patch->mod)
918 return -EINVAL;
919
920 if (!is_livepatch_module(patch->mod)) {
921 pr_err("module %s is not marked as a livepatch module",
922 patch->mod->name);
923 return -EINVAL;
924 }
925
926 if (!klp_initialized())
927 return -ENODEV;
928
929 /*
930 * A reference is taken on the patch module to prevent it from being
931 * unloaded. Right now, we don't allow patch modules to unload since
932 * there is currently no method to determine if a thread is still
933 * running in the patched code contained in the patch module once
934 * the ftrace registration is successful.
935 */
936 if (!try_module_get(patch->mod))
937 return -ENODEV;
938
939 ret = klp_init_patch(patch);
940 if (ret)
941 module_put(patch->mod);
942
943 return ret;
944}
945EXPORT_SYMBOL_GPL(klp_register_patch);
946
947int klp_module_coming(struct module *mod)
948{
949 int ret;
950 struct klp_patch *patch;
951 struct klp_object *obj;
952
953 if (WARN_ON(mod->state != MODULE_STATE_COMING))
954 return -EINVAL;
955
956 mutex_lock(&klp_mutex);
957 /*
958 * Each module has to know that klp_module_coming()
959 * has been called. We never know what module will
960 * get patched by a new patch.
961 */
962 mod->klp_alive = true;
963
964 list_for_each_entry(patch, &klp_patches, list) {
965 klp_for_each_object(patch, obj) {
966 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
967 continue;
968
969 obj->mod = mod;
970
971 ret = klp_init_object_loaded(patch, obj);
972 if (ret) {
973 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
974 patch->mod->name, obj->mod->name, ret);
975 goto err;
976 }
977
978 if (patch->state == KLP_DISABLED)
979 break;
980
981 pr_notice("applying patch '%s' to loading module '%s'\n",
982 patch->mod->name, obj->mod->name);
983
984 ret = klp_enable_object(obj);
985 if (ret) {
986 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
987 patch->mod->name, obj->mod->name, ret);
988 goto err;
989 }
990
991 break;
992 }
993 }
994
995 mutex_unlock(&klp_mutex);
996
997 return 0;
998
999err:
1000 /*
1001 * If a patch is unsuccessfully applied, return
1002 * error to the module loader.
1003 */
1004 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1005 patch->mod->name, obj->mod->name, obj->mod->name);
1006 mod->klp_alive = false;
1007 klp_free_object_loaded(obj);
1008 mutex_unlock(&klp_mutex);
1009
1010 return ret;
1011}
1012
1013void klp_module_going(struct module *mod)
1014{
1015 struct klp_patch *patch;
1016 struct klp_object *obj;
1017
1018 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1019 mod->state != MODULE_STATE_COMING))
1020 return;
1021
1022 mutex_lock(&klp_mutex);
1023 /*
1024 * Each module has to know that klp_module_going()
1025 * has been called. We never know what module will
1026 * get patched by a new patch.
1027 */
1028 mod->klp_alive = false;
1029
1030 list_for_each_entry(patch, &klp_patches, list) {
1031 klp_for_each_object(patch, obj) {
1032 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1033 continue;
1034
1035 if (patch->state != KLP_DISABLED) {
1036 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1037 patch->mod->name, obj->mod->name);
1038 klp_disable_object(obj);
1039 }
1040
1041 klp_free_object_loaded(obj);
1042 break;
1043 }
1044 }
1045
1046 mutex_unlock(&klp_mutex);
1047}
1048
1049static int __init klp_init(void)
1050{
1051 int ret;
1052
1053 ret = klp_check_compiler_support();
1054 if (ret) {
1055 pr_info("Your compiler is too old; turning off.\n");
1056 return -EINVAL;
1057 }
1058
1059 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1060 if (!klp_root_kobj)
1061 return -ENOMEM;
1062
1063 return 0;
1064}
1065
1066module_init(klp_init);