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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * core.c - Kernel Live Patching Core
4 *
5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6 * Copyright (C) 2014 SUSE
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/module.h>
12#include <linux/kernel.h>
13#include <linux/mutex.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/kallsyms.h>
17#include <linux/livepatch.h>
18#include <linux/elf.h>
19#include <linux/moduleloader.h>
20#include <linux/completion.h>
21#include <linux/memory.h>
22#include <linux/rcupdate.h>
23#include <asm/cacheflush.h>
24#include "core.h"
25#include "patch.h"
26#include "state.h"
27#include "transition.h"
28
29/*
30 * klp_mutex is a coarse lock which serializes access to klp data. All
31 * accesses to klp-related variables and structures must have mutex protection,
32 * except within the following functions which carefully avoid the need for it:
33 *
34 * - klp_ftrace_handler()
35 * - klp_update_patch_state()
36 * - __klp_sched_try_switch()
37 */
38DEFINE_MUTEX(klp_mutex);
39
40/*
41 * Actively used patches: enabled or in transition. Note that replaced
42 * or disabled patches are not listed even though the related kernel
43 * module still can be loaded.
44 */
45LIST_HEAD(klp_patches);
46
47static struct kobject *klp_root_kobj;
48
49static bool klp_is_module(struct klp_object *obj)
50{
51 return obj->name;
52}
53
54/* sets obj->mod if object is not vmlinux and module is found */
55static void klp_find_object_module(struct klp_object *obj)
56{
57 struct module *mod;
58
59 if (!klp_is_module(obj))
60 return;
61
62 rcu_read_lock_sched();
63 /*
64 * We do not want to block removal of patched modules and therefore
65 * we do not take a reference here. The patches are removed by
66 * klp_module_going() instead.
67 */
68 mod = find_module(obj->name);
69 /*
70 * Do not mess work of klp_module_coming() and klp_module_going().
71 * Note that the patch might still be needed before klp_module_going()
72 * is called. Module functions can be called even in the GOING state
73 * until mod->exit() finishes. This is especially important for
74 * patches that modify semantic of the functions.
75 */
76 if (mod && mod->klp_alive)
77 obj->mod = mod;
78
79 rcu_read_unlock_sched();
80}
81
82static bool klp_initialized(void)
83{
84 return !!klp_root_kobj;
85}
86
87static struct klp_func *klp_find_func(struct klp_object *obj,
88 struct klp_func *old_func)
89{
90 struct klp_func *func;
91
92 klp_for_each_func(obj, func) {
93 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
94 (old_func->old_sympos == func->old_sympos)) {
95 return func;
96 }
97 }
98
99 return NULL;
100}
101
102static struct klp_object *klp_find_object(struct klp_patch *patch,
103 struct klp_object *old_obj)
104{
105 struct klp_object *obj;
106
107 klp_for_each_object(patch, obj) {
108 if (klp_is_module(old_obj)) {
109 if (klp_is_module(obj) &&
110 strcmp(old_obj->name, obj->name) == 0) {
111 return obj;
112 }
113 } else if (!klp_is_module(obj)) {
114 return obj;
115 }
116 }
117
118 return NULL;
119}
120
121struct klp_find_arg {
122 const char *name;
123 unsigned long addr;
124 unsigned long count;
125 unsigned long pos;
126};
127
128static int klp_match_callback(void *data, unsigned long addr)
129{
130 struct klp_find_arg *args = data;
131
132 args->addr = addr;
133 args->count++;
134
135 /*
136 * Finish the search when the symbol is found for the desired position
137 * or the position is not defined for a non-unique symbol.
138 */
139 if ((args->pos && (args->count == args->pos)) ||
140 (!args->pos && (args->count > 1)))
141 return 1;
142
143 return 0;
144}
145
146static int klp_find_callback(void *data, const char *name, unsigned long addr)
147{
148 struct klp_find_arg *args = data;
149
150 if (strcmp(args->name, name))
151 return 0;
152
153 return klp_match_callback(data, addr);
154}
155
156static int klp_find_object_symbol(const char *objname, const char *name,
157 unsigned long sympos, unsigned long *addr)
158{
159 struct klp_find_arg args = {
160 .name = name,
161 .addr = 0,
162 .count = 0,
163 .pos = sympos,
164 };
165
166 if (objname)
167 module_kallsyms_on_each_symbol(objname, klp_find_callback, &args);
168 else
169 kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
170
171 /*
172 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
173 * otherwise ensure the symbol position count matches sympos.
174 */
175 if (args.addr == 0)
176 pr_err("symbol '%s' not found in symbol table\n", name);
177 else if (args.count > 1 && sympos == 0) {
178 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
179 name, objname);
180 } else if (sympos != args.count && sympos > 0) {
181 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
182 sympos, name, objname ? objname : "vmlinux");
183 } else {
184 *addr = args.addr;
185 return 0;
186 }
187
188 *addr = 0;
189 return -EINVAL;
190}
191
192static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
193 unsigned int symndx, Elf_Shdr *relasec,
194 const char *sec_objname)
195{
196 int i, cnt, ret;
197 char sym_objname[MODULE_NAME_LEN];
198 char sym_name[KSYM_NAME_LEN];
199 Elf_Rela *relas;
200 Elf_Sym *sym;
201 unsigned long sympos, addr;
202 bool sym_vmlinux;
203 bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
204
205 /*
206 * Since the field widths for sym_objname and sym_name in the sscanf()
207 * call are hard-coded and correspond to MODULE_NAME_LEN and
208 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
209 * and KSYM_NAME_LEN have the values we expect them to have.
210 *
211 * Because the value of MODULE_NAME_LEN can differ among architectures,
212 * we use the smallest/strictest upper bound possible (56, based on
213 * the current definition of MODULE_NAME_LEN) to prevent overflows.
214 */
215 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
216
217 relas = (Elf_Rela *) relasec->sh_addr;
218 /* For each rela in this klp relocation section */
219 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
220 sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
221 if (sym->st_shndx != SHN_LIVEPATCH) {
222 pr_err("symbol %s is not marked as a livepatch symbol\n",
223 strtab + sym->st_name);
224 return -EINVAL;
225 }
226
227 /* Format: .klp.sym.sym_objname.sym_name,sympos */
228 cnt = sscanf(strtab + sym->st_name,
229 ".klp.sym.%55[^.].%511[^,],%lu",
230 sym_objname, sym_name, &sympos);
231 if (cnt != 3) {
232 pr_err("symbol %s has an incorrectly formatted name\n",
233 strtab + sym->st_name);
234 return -EINVAL;
235 }
236
237 sym_vmlinux = !strcmp(sym_objname, "vmlinux");
238
239 /*
240 * Prevent module-specific KLP rela sections from referencing
241 * vmlinux symbols. This helps prevent ordering issues with
242 * module special section initializations. Presumably such
243 * symbols are exported and normal relas can be used instead.
244 */
245 if (!sec_vmlinux && sym_vmlinux) {
246 pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section\n",
247 sym_name);
248 return -EINVAL;
249 }
250
251 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
252 ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
253 sym_name, sympos, &addr);
254 if (ret)
255 return ret;
256
257 sym->st_value = addr;
258 }
259
260 return 0;
261}
262
263void __weak clear_relocate_add(Elf_Shdr *sechdrs,
264 const char *strtab,
265 unsigned int symindex,
266 unsigned int relsec,
267 struct module *me)
268{
269}
270
271/*
272 * At a high-level, there are two types of klp relocation sections: those which
273 * reference symbols which live in vmlinux; and those which reference symbols
274 * which live in other modules. This function is called for both types:
275 *
276 * 1) When a klp module itself loads, the module code calls this function to
277 * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
278 * These relocations are written to the klp module text to allow the patched
279 * code/data to reference unexported vmlinux symbols. They're written as
280 * early as possible to ensure that other module init code (.e.g.,
281 * jump_label_apply_nops) can access any unexported vmlinux symbols which
282 * might be referenced by the klp module's special sections.
283 *
284 * 2) When a to-be-patched module loads -- or is already loaded when a
285 * corresponding klp module loads -- klp code calls this function to write
286 * module-specific klp relocations (.klp.rela.{module}.* sections). These
287 * are written to the klp module text to allow the patched code/data to
288 * reference symbols which live in the to-be-patched module or one of its
289 * module dependencies. Exported symbols are supported, in addition to
290 * unexported symbols, in order to enable late module patching, which allows
291 * the to-be-patched module to be loaded and patched sometime *after* the
292 * klp module is loaded.
293 */
294static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
295 const char *shstrtab, const char *strtab,
296 unsigned int symndx, unsigned int secndx,
297 const char *objname, bool apply)
298{
299 int cnt, ret;
300 char sec_objname[MODULE_NAME_LEN];
301 Elf_Shdr *sec = sechdrs + secndx;
302
303 /*
304 * Format: .klp.rela.sec_objname.section_name
305 * See comment in klp_resolve_symbols() for an explanation
306 * of the selected field width value.
307 */
308 cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
309 sec_objname);
310 if (cnt != 1) {
311 pr_err("section %s has an incorrectly formatted name\n",
312 shstrtab + sec->sh_name);
313 return -EINVAL;
314 }
315
316 if (strcmp(objname ? objname : "vmlinux", sec_objname))
317 return 0;
318
319 if (apply) {
320 ret = klp_resolve_symbols(sechdrs, strtab, symndx,
321 sec, sec_objname);
322 if (ret)
323 return ret;
324
325 return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
326 }
327
328 clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
329 return 0;
330}
331
332int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
333 const char *shstrtab, const char *strtab,
334 unsigned int symndx, unsigned int secndx,
335 const char *objname)
336{
337 return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx,
338 secndx, objname, true);
339}
340
341/*
342 * Sysfs Interface
343 *
344 * /sys/kernel/livepatch
345 * /sys/kernel/livepatch/<patch>
346 * /sys/kernel/livepatch/<patch>/enabled
347 * /sys/kernel/livepatch/<patch>/transition
348 * /sys/kernel/livepatch/<patch>/force
349 * /sys/kernel/livepatch/<patch>/<object>
350 * /sys/kernel/livepatch/<patch>/<object>/patched
351 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
352 */
353static int __klp_disable_patch(struct klp_patch *patch);
354
355static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
356 const char *buf, size_t count)
357{
358 struct klp_patch *patch;
359 int ret;
360 bool enabled;
361
362 ret = kstrtobool(buf, &enabled);
363 if (ret)
364 return ret;
365
366 patch = container_of(kobj, struct klp_patch, kobj);
367
368 mutex_lock(&klp_mutex);
369
370 if (patch->enabled == enabled) {
371 /* already in requested state */
372 ret = -EINVAL;
373 goto out;
374 }
375
376 /*
377 * Allow to reverse a pending transition in both ways. It might be
378 * necessary to complete the transition without forcing and breaking
379 * the system integrity.
380 *
381 * Do not allow to re-enable a disabled patch.
382 */
383 if (patch == klp_transition_patch)
384 klp_reverse_transition();
385 else if (!enabled)
386 ret = __klp_disable_patch(patch);
387 else
388 ret = -EINVAL;
389
390out:
391 mutex_unlock(&klp_mutex);
392
393 if (ret)
394 return ret;
395 return count;
396}
397
398static ssize_t enabled_show(struct kobject *kobj,
399 struct kobj_attribute *attr, char *buf)
400{
401 struct klp_patch *patch;
402
403 patch = container_of(kobj, struct klp_patch, kobj);
404 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
405}
406
407static ssize_t transition_show(struct kobject *kobj,
408 struct kobj_attribute *attr, char *buf)
409{
410 struct klp_patch *patch;
411
412 patch = container_of(kobj, struct klp_patch, kobj);
413 return snprintf(buf, PAGE_SIZE-1, "%d\n",
414 patch == klp_transition_patch);
415}
416
417static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
418 const char *buf, size_t count)
419{
420 struct klp_patch *patch;
421 int ret;
422 bool val;
423
424 ret = kstrtobool(buf, &val);
425 if (ret)
426 return ret;
427
428 if (!val)
429 return count;
430
431 mutex_lock(&klp_mutex);
432
433 patch = container_of(kobj, struct klp_patch, kobj);
434 if (patch != klp_transition_patch) {
435 mutex_unlock(&klp_mutex);
436 return -EINVAL;
437 }
438
439 klp_force_transition();
440
441 mutex_unlock(&klp_mutex);
442
443 return count;
444}
445
446static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
447static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
448static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
449static struct attribute *klp_patch_attrs[] = {
450 &enabled_kobj_attr.attr,
451 &transition_kobj_attr.attr,
452 &force_kobj_attr.attr,
453 NULL
454};
455ATTRIBUTE_GROUPS(klp_patch);
456
457static ssize_t patched_show(struct kobject *kobj,
458 struct kobj_attribute *attr, char *buf)
459{
460 struct klp_object *obj;
461
462 obj = container_of(kobj, struct klp_object, kobj);
463 return sysfs_emit(buf, "%d\n", obj->patched);
464}
465
466static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
467static struct attribute *klp_object_attrs[] = {
468 &patched_kobj_attr.attr,
469 NULL,
470};
471ATTRIBUTE_GROUPS(klp_object);
472
473static void klp_free_object_dynamic(struct klp_object *obj)
474{
475 kfree(obj->name);
476 kfree(obj);
477}
478
479static void klp_init_func_early(struct klp_object *obj,
480 struct klp_func *func);
481static void klp_init_object_early(struct klp_patch *patch,
482 struct klp_object *obj);
483
484static struct klp_object *klp_alloc_object_dynamic(const char *name,
485 struct klp_patch *patch)
486{
487 struct klp_object *obj;
488
489 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
490 if (!obj)
491 return NULL;
492
493 if (name) {
494 obj->name = kstrdup(name, GFP_KERNEL);
495 if (!obj->name) {
496 kfree(obj);
497 return NULL;
498 }
499 }
500
501 klp_init_object_early(patch, obj);
502 obj->dynamic = true;
503
504 return obj;
505}
506
507static void klp_free_func_nop(struct klp_func *func)
508{
509 kfree(func->old_name);
510 kfree(func);
511}
512
513static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
514 struct klp_object *obj)
515{
516 struct klp_func *func;
517
518 func = kzalloc(sizeof(*func), GFP_KERNEL);
519 if (!func)
520 return NULL;
521
522 if (old_func->old_name) {
523 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
524 if (!func->old_name) {
525 kfree(func);
526 return NULL;
527 }
528 }
529
530 klp_init_func_early(obj, func);
531 /*
532 * func->new_func is same as func->old_func. These addresses are
533 * set when the object is loaded, see klp_init_object_loaded().
534 */
535 func->old_sympos = old_func->old_sympos;
536 func->nop = true;
537
538 return func;
539}
540
541static int klp_add_object_nops(struct klp_patch *patch,
542 struct klp_object *old_obj)
543{
544 struct klp_object *obj;
545 struct klp_func *func, *old_func;
546
547 obj = klp_find_object(patch, old_obj);
548
549 if (!obj) {
550 obj = klp_alloc_object_dynamic(old_obj->name, patch);
551 if (!obj)
552 return -ENOMEM;
553 }
554
555 klp_for_each_func(old_obj, old_func) {
556 func = klp_find_func(obj, old_func);
557 if (func)
558 continue;
559
560 func = klp_alloc_func_nop(old_func, obj);
561 if (!func)
562 return -ENOMEM;
563 }
564
565 return 0;
566}
567
568/*
569 * Add 'nop' functions which simply return to the caller to run
570 * the original function. The 'nop' functions are added to a
571 * patch to facilitate a 'replace' mode.
572 */
573static int klp_add_nops(struct klp_patch *patch)
574{
575 struct klp_patch *old_patch;
576 struct klp_object *old_obj;
577
578 klp_for_each_patch(old_patch) {
579 klp_for_each_object(old_patch, old_obj) {
580 int err;
581
582 err = klp_add_object_nops(patch, old_obj);
583 if (err)
584 return err;
585 }
586 }
587
588 return 0;
589}
590
591static void klp_kobj_release_patch(struct kobject *kobj)
592{
593 struct klp_patch *patch;
594
595 patch = container_of(kobj, struct klp_patch, kobj);
596 complete(&patch->finish);
597}
598
599static const struct kobj_type klp_ktype_patch = {
600 .release = klp_kobj_release_patch,
601 .sysfs_ops = &kobj_sysfs_ops,
602 .default_groups = klp_patch_groups,
603};
604
605static void klp_kobj_release_object(struct kobject *kobj)
606{
607 struct klp_object *obj;
608
609 obj = container_of(kobj, struct klp_object, kobj);
610
611 if (obj->dynamic)
612 klp_free_object_dynamic(obj);
613}
614
615static const struct kobj_type klp_ktype_object = {
616 .release = klp_kobj_release_object,
617 .sysfs_ops = &kobj_sysfs_ops,
618 .default_groups = klp_object_groups,
619};
620
621static void klp_kobj_release_func(struct kobject *kobj)
622{
623 struct klp_func *func;
624
625 func = container_of(kobj, struct klp_func, kobj);
626
627 if (func->nop)
628 klp_free_func_nop(func);
629}
630
631static const struct kobj_type klp_ktype_func = {
632 .release = klp_kobj_release_func,
633 .sysfs_ops = &kobj_sysfs_ops,
634};
635
636static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
637{
638 struct klp_func *func, *tmp_func;
639
640 klp_for_each_func_safe(obj, func, tmp_func) {
641 if (nops_only && !func->nop)
642 continue;
643
644 list_del(&func->node);
645 kobject_put(&func->kobj);
646 }
647}
648
649/* Clean up when a patched object is unloaded */
650static void klp_free_object_loaded(struct klp_object *obj)
651{
652 struct klp_func *func;
653
654 obj->mod = NULL;
655
656 klp_for_each_func(obj, func) {
657 func->old_func = NULL;
658
659 if (func->nop)
660 func->new_func = NULL;
661 }
662}
663
664static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
665{
666 struct klp_object *obj, *tmp_obj;
667
668 klp_for_each_object_safe(patch, obj, tmp_obj) {
669 __klp_free_funcs(obj, nops_only);
670
671 if (nops_only && !obj->dynamic)
672 continue;
673
674 list_del(&obj->node);
675 kobject_put(&obj->kobj);
676 }
677}
678
679static void klp_free_objects(struct klp_patch *patch)
680{
681 __klp_free_objects(patch, false);
682}
683
684static void klp_free_objects_dynamic(struct klp_patch *patch)
685{
686 __klp_free_objects(patch, true);
687}
688
689/*
690 * This function implements the free operations that can be called safely
691 * under klp_mutex.
692 *
693 * The operation must be completed by calling klp_free_patch_finish()
694 * outside klp_mutex.
695 */
696static void klp_free_patch_start(struct klp_patch *patch)
697{
698 if (!list_empty(&patch->list))
699 list_del(&patch->list);
700
701 klp_free_objects(patch);
702}
703
704/*
705 * This function implements the free part that must be called outside
706 * klp_mutex.
707 *
708 * It must be called after klp_free_patch_start(). And it has to be
709 * the last function accessing the livepatch structures when the patch
710 * gets disabled.
711 */
712static void klp_free_patch_finish(struct klp_patch *patch)
713{
714 /*
715 * Avoid deadlock with enabled_store() sysfs callback by
716 * calling this outside klp_mutex. It is safe because
717 * this is called when the patch gets disabled and it
718 * cannot get enabled again.
719 */
720 kobject_put(&patch->kobj);
721 wait_for_completion(&patch->finish);
722
723 /* Put the module after the last access to struct klp_patch. */
724 if (!patch->forced)
725 module_put(patch->mod);
726}
727
728/*
729 * The livepatch might be freed from sysfs interface created by the patch.
730 * This work allows to wait until the interface is destroyed in a separate
731 * context.
732 */
733static void klp_free_patch_work_fn(struct work_struct *work)
734{
735 struct klp_patch *patch =
736 container_of(work, struct klp_patch, free_work);
737
738 klp_free_patch_finish(patch);
739}
740
741void klp_free_patch_async(struct klp_patch *patch)
742{
743 klp_free_patch_start(patch);
744 schedule_work(&patch->free_work);
745}
746
747void klp_free_replaced_patches_async(struct klp_patch *new_patch)
748{
749 struct klp_patch *old_patch, *tmp_patch;
750
751 klp_for_each_patch_safe(old_patch, tmp_patch) {
752 if (old_patch == new_patch)
753 return;
754 klp_free_patch_async(old_patch);
755 }
756}
757
758static int klp_init_func(struct klp_object *obj, struct klp_func *func)
759{
760 if (!func->old_name)
761 return -EINVAL;
762
763 /*
764 * NOPs get the address later. The patched module must be loaded,
765 * see klp_init_object_loaded().
766 */
767 if (!func->new_func && !func->nop)
768 return -EINVAL;
769
770 if (strlen(func->old_name) >= KSYM_NAME_LEN)
771 return -EINVAL;
772
773 INIT_LIST_HEAD(&func->stack_node);
774 func->patched = false;
775 func->transition = false;
776
777 /* The format for the sysfs directory is <function,sympos> where sympos
778 * is the nth occurrence of this symbol in kallsyms for the patched
779 * object. If the user selects 0 for old_sympos, then 1 will be used
780 * since a unique symbol will be the first occurrence.
781 */
782 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
783 func->old_name,
784 func->old_sympos ? func->old_sympos : 1);
785}
786
787static int klp_write_object_relocs(struct klp_patch *patch,
788 struct klp_object *obj,
789 bool apply)
790{
791 int i, ret;
792 struct klp_modinfo *info = patch->mod->klp_info;
793
794 for (i = 1; i < info->hdr.e_shnum; i++) {
795 Elf_Shdr *sec = info->sechdrs + i;
796
797 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
798 continue;
799
800 ret = klp_write_section_relocs(patch->mod, info->sechdrs,
801 info->secstrings,
802 patch->mod->core_kallsyms.strtab,
803 info->symndx, i, obj->name, apply);
804 if (ret)
805 return ret;
806 }
807
808 return 0;
809}
810
811static int klp_apply_object_relocs(struct klp_patch *patch,
812 struct klp_object *obj)
813{
814 return klp_write_object_relocs(patch, obj, true);
815}
816
817static void klp_clear_object_relocs(struct klp_patch *patch,
818 struct klp_object *obj)
819{
820 klp_write_object_relocs(patch, obj, false);
821}
822
823/* parts of the initialization that is done only when the object is loaded */
824static int klp_init_object_loaded(struct klp_patch *patch,
825 struct klp_object *obj)
826{
827 struct klp_func *func;
828 int ret;
829
830 if (klp_is_module(obj)) {
831 /*
832 * Only write module-specific relocations here
833 * (.klp.rela.{module}.*). vmlinux-specific relocations were
834 * written earlier during the initialization of the klp module
835 * itself.
836 */
837 ret = klp_apply_object_relocs(patch, obj);
838 if (ret)
839 return ret;
840 }
841
842 klp_for_each_func(obj, func) {
843 ret = klp_find_object_symbol(obj->name, func->old_name,
844 func->old_sympos,
845 (unsigned long *)&func->old_func);
846 if (ret)
847 return ret;
848
849 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
850 &func->old_size, NULL);
851 if (!ret) {
852 pr_err("kallsyms size lookup failed for '%s'\n",
853 func->old_name);
854 return -ENOENT;
855 }
856
857 if (func->nop)
858 func->new_func = func->old_func;
859
860 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
861 &func->new_size, NULL);
862 if (!ret) {
863 pr_err("kallsyms size lookup failed for '%s' replacement\n",
864 func->old_name);
865 return -ENOENT;
866 }
867 }
868
869 return 0;
870}
871
872static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
873{
874 struct klp_func *func;
875 int ret;
876 const char *name;
877
878 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
879 return -EINVAL;
880
881 obj->patched = false;
882 obj->mod = NULL;
883
884 klp_find_object_module(obj);
885
886 name = klp_is_module(obj) ? obj->name : "vmlinux";
887 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
888 if (ret)
889 return ret;
890
891 klp_for_each_func(obj, func) {
892 ret = klp_init_func(obj, func);
893 if (ret)
894 return ret;
895 }
896
897 if (klp_is_object_loaded(obj))
898 ret = klp_init_object_loaded(patch, obj);
899
900 return ret;
901}
902
903static void klp_init_func_early(struct klp_object *obj,
904 struct klp_func *func)
905{
906 kobject_init(&func->kobj, &klp_ktype_func);
907 list_add_tail(&func->node, &obj->func_list);
908}
909
910static void klp_init_object_early(struct klp_patch *patch,
911 struct klp_object *obj)
912{
913 INIT_LIST_HEAD(&obj->func_list);
914 kobject_init(&obj->kobj, &klp_ktype_object);
915 list_add_tail(&obj->node, &patch->obj_list);
916}
917
918static void klp_init_patch_early(struct klp_patch *patch)
919{
920 struct klp_object *obj;
921 struct klp_func *func;
922
923 INIT_LIST_HEAD(&patch->list);
924 INIT_LIST_HEAD(&patch->obj_list);
925 kobject_init(&patch->kobj, &klp_ktype_patch);
926 patch->enabled = false;
927 patch->forced = false;
928 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
929 init_completion(&patch->finish);
930
931 klp_for_each_object_static(patch, obj) {
932 klp_init_object_early(patch, obj);
933
934 klp_for_each_func_static(obj, func) {
935 klp_init_func_early(obj, func);
936 }
937 }
938}
939
940static int klp_init_patch(struct klp_patch *patch)
941{
942 struct klp_object *obj;
943 int ret;
944
945 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
946 if (ret)
947 return ret;
948
949 if (patch->replace) {
950 ret = klp_add_nops(patch);
951 if (ret)
952 return ret;
953 }
954
955 klp_for_each_object(patch, obj) {
956 ret = klp_init_object(patch, obj);
957 if (ret)
958 return ret;
959 }
960
961 list_add_tail(&patch->list, &klp_patches);
962
963 return 0;
964}
965
966static int __klp_disable_patch(struct klp_patch *patch)
967{
968 struct klp_object *obj;
969
970 if (WARN_ON(!patch->enabled))
971 return -EINVAL;
972
973 if (klp_transition_patch)
974 return -EBUSY;
975
976 klp_init_transition(patch, KLP_UNPATCHED);
977
978 klp_for_each_object(patch, obj)
979 if (obj->patched)
980 klp_pre_unpatch_callback(obj);
981
982 /*
983 * Enforce the order of the func->transition writes in
984 * klp_init_transition() and the TIF_PATCH_PENDING writes in
985 * klp_start_transition(). In the rare case where klp_ftrace_handler()
986 * is called shortly after klp_update_patch_state() switches the task,
987 * this ensures the handler sees that func->transition is set.
988 */
989 smp_wmb();
990
991 klp_start_transition();
992 patch->enabled = false;
993 klp_try_complete_transition();
994
995 return 0;
996}
997
998static int __klp_enable_patch(struct klp_patch *patch)
999{
1000 struct klp_object *obj;
1001 int ret;
1002
1003 if (klp_transition_patch)
1004 return -EBUSY;
1005
1006 if (WARN_ON(patch->enabled))
1007 return -EINVAL;
1008
1009 pr_notice("enabling patch '%s'\n", patch->mod->name);
1010
1011 klp_init_transition(patch, KLP_PATCHED);
1012
1013 /*
1014 * Enforce the order of the func->transition writes in
1015 * klp_init_transition() and the ops->func_stack writes in
1016 * klp_patch_object(), so that klp_ftrace_handler() will see the
1017 * func->transition updates before the handler is registered and the
1018 * new funcs become visible to the handler.
1019 */
1020 smp_wmb();
1021
1022 klp_for_each_object(patch, obj) {
1023 if (!klp_is_object_loaded(obj))
1024 continue;
1025
1026 ret = klp_pre_patch_callback(obj);
1027 if (ret) {
1028 pr_warn("pre-patch callback failed for object '%s'\n",
1029 klp_is_module(obj) ? obj->name : "vmlinux");
1030 goto err;
1031 }
1032
1033 ret = klp_patch_object(obj);
1034 if (ret) {
1035 pr_warn("failed to patch object '%s'\n",
1036 klp_is_module(obj) ? obj->name : "vmlinux");
1037 goto err;
1038 }
1039 }
1040
1041 klp_start_transition();
1042 patch->enabled = true;
1043 klp_try_complete_transition();
1044
1045 return 0;
1046err:
1047 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
1048
1049 klp_cancel_transition();
1050 return ret;
1051}
1052
1053/**
1054 * klp_enable_patch() - enable the livepatch
1055 * @patch: patch to be enabled
1056 *
1057 * Initializes the data structure associated with the patch, creates the sysfs
1058 * interface, performs the needed symbol lookups and code relocations,
1059 * registers the patched functions with ftrace.
1060 *
1061 * This function is supposed to be called from the livepatch module_init()
1062 * callback.
1063 *
1064 * Return: 0 on success, otherwise error
1065 */
1066int klp_enable_patch(struct klp_patch *patch)
1067{
1068 int ret;
1069 struct klp_object *obj;
1070
1071 if (!patch || !patch->mod || !patch->objs)
1072 return -EINVAL;
1073
1074 klp_for_each_object_static(patch, obj) {
1075 if (!obj->funcs)
1076 return -EINVAL;
1077 }
1078
1079
1080 if (!is_livepatch_module(patch->mod)) {
1081 pr_err("module %s is not marked as a livepatch module\n",
1082 patch->mod->name);
1083 return -EINVAL;
1084 }
1085
1086 if (!klp_initialized())
1087 return -ENODEV;
1088
1089 if (!klp_have_reliable_stack()) {
1090 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1091 pr_warn("The livepatch transition may never complete.\n");
1092 }
1093
1094 mutex_lock(&klp_mutex);
1095
1096 if (!klp_is_patch_compatible(patch)) {
1097 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1098 patch->mod->name);
1099 mutex_unlock(&klp_mutex);
1100 return -EINVAL;
1101 }
1102
1103 if (!try_module_get(patch->mod)) {
1104 mutex_unlock(&klp_mutex);
1105 return -ENODEV;
1106 }
1107
1108 klp_init_patch_early(patch);
1109
1110 ret = klp_init_patch(patch);
1111 if (ret)
1112 goto err;
1113
1114 ret = __klp_enable_patch(patch);
1115 if (ret)
1116 goto err;
1117
1118 mutex_unlock(&klp_mutex);
1119
1120 return 0;
1121
1122err:
1123 klp_free_patch_start(patch);
1124
1125 mutex_unlock(&klp_mutex);
1126
1127 klp_free_patch_finish(patch);
1128
1129 return ret;
1130}
1131EXPORT_SYMBOL_GPL(klp_enable_patch);
1132
1133/*
1134 * This function unpatches objects from the replaced livepatches.
1135 *
1136 * We could be pretty aggressive here. It is called in the situation where
1137 * these structures are no longer accessed from the ftrace handler.
1138 * All functions are redirected by the klp_transition_patch. They
1139 * use either a new code or they are in the original code because
1140 * of the special nop function patches.
1141 *
1142 * The only exception is when the transition was forced. In this case,
1143 * klp_ftrace_handler() might still see the replaced patch on the stack.
1144 * Fortunately, it is carefully designed to work with removed functions
1145 * thanks to RCU. We only have to keep the patches on the system. Also
1146 * this is handled transparently by patch->module_put.
1147 */
1148void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1149{
1150 struct klp_patch *old_patch;
1151
1152 klp_for_each_patch(old_patch) {
1153 if (old_patch == new_patch)
1154 return;
1155
1156 old_patch->enabled = false;
1157 klp_unpatch_objects(old_patch);
1158 }
1159}
1160
1161/*
1162 * This function removes the dynamically allocated 'nop' functions.
1163 *
1164 * We could be pretty aggressive. NOPs do not change the existing
1165 * behavior except for adding unnecessary delay by the ftrace handler.
1166 *
1167 * It is safe even when the transition was forced. The ftrace handler
1168 * will see a valid ops->func_stack entry thanks to RCU.
1169 *
1170 * We could even free the NOPs structures. They must be the last entry
1171 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1172 * It does the same as klp_synchronize_transition() to make sure that
1173 * nobody is inside the ftrace handler once the operation finishes.
1174 *
1175 * IMPORTANT: It must be called right after removing the replaced patches!
1176 */
1177void klp_discard_nops(struct klp_patch *new_patch)
1178{
1179 klp_unpatch_objects_dynamic(klp_transition_patch);
1180 klp_free_objects_dynamic(klp_transition_patch);
1181}
1182
1183/*
1184 * Remove parts of patches that touch a given kernel module. The list of
1185 * patches processed might be limited. When limit is NULL, all patches
1186 * will be handled.
1187 */
1188static void klp_cleanup_module_patches_limited(struct module *mod,
1189 struct klp_patch *limit)
1190{
1191 struct klp_patch *patch;
1192 struct klp_object *obj;
1193
1194 klp_for_each_patch(patch) {
1195 if (patch == limit)
1196 break;
1197
1198 klp_for_each_object(patch, obj) {
1199 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1200 continue;
1201
1202 if (patch != klp_transition_patch)
1203 klp_pre_unpatch_callback(obj);
1204
1205 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1206 patch->mod->name, obj->mod->name);
1207 klp_unpatch_object(obj);
1208
1209 klp_post_unpatch_callback(obj);
1210 klp_clear_object_relocs(patch, obj);
1211 klp_free_object_loaded(obj);
1212 break;
1213 }
1214 }
1215}
1216
1217int klp_module_coming(struct module *mod)
1218{
1219 int ret;
1220 struct klp_patch *patch;
1221 struct klp_object *obj;
1222
1223 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1224 return -EINVAL;
1225
1226 if (!strcmp(mod->name, "vmlinux")) {
1227 pr_err("vmlinux.ko: invalid module name\n");
1228 return -EINVAL;
1229 }
1230
1231 mutex_lock(&klp_mutex);
1232 /*
1233 * Each module has to know that klp_module_coming()
1234 * has been called. We never know what module will
1235 * get patched by a new patch.
1236 */
1237 mod->klp_alive = true;
1238
1239 klp_for_each_patch(patch) {
1240 klp_for_each_object(patch, obj) {
1241 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1242 continue;
1243
1244 obj->mod = mod;
1245
1246 ret = klp_init_object_loaded(patch, obj);
1247 if (ret) {
1248 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1249 patch->mod->name, obj->mod->name, ret);
1250 goto err;
1251 }
1252
1253 pr_notice("applying patch '%s' to loading module '%s'\n",
1254 patch->mod->name, obj->mod->name);
1255
1256 ret = klp_pre_patch_callback(obj);
1257 if (ret) {
1258 pr_warn("pre-patch callback failed for object '%s'\n",
1259 obj->name);
1260 goto err;
1261 }
1262
1263 ret = klp_patch_object(obj);
1264 if (ret) {
1265 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1266 patch->mod->name, obj->mod->name, ret);
1267
1268 klp_post_unpatch_callback(obj);
1269 goto err;
1270 }
1271
1272 if (patch != klp_transition_patch)
1273 klp_post_patch_callback(obj);
1274
1275 break;
1276 }
1277 }
1278
1279 mutex_unlock(&klp_mutex);
1280
1281 return 0;
1282
1283err:
1284 /*
1285 * If a patch is unsuccessfully applied, return
1286 * error to the module loader.
1287 */
1288 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1289 patch->mod->name, obj->mod->name, obj->mod->name);
1290 mod->klp_alive = false;
1291 obj->mod = NULL;
1292 klp_cleanup_module_patches_limited(mod, patch);
1293 mutex_unlock(&klp_mutex);
1294
1295 return ret;
1296}
1297
1298void klp_module_going(struct module *mod)
1299{
1300 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1301 mod->state != MODULE_STATE_COMING))
1302 return;
1303
1304 mutex_lock(&klp_mutex);
1305 /*
1306 * Each module has to know that klp_module_going()
1307 * has been called. We never know what module will
1308 * get patched by a new patch.
1309 */
1310 mod->klp_alive = false;
1311
1312 klp_cleanup_module_patches_limited(mod, NULL);
1313
1314 mutex_unlock(&klp_mutex);
1315}
1316
1317static int __init klp_init(void)
1318{
1319 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1320 if (!klp_root_kobj)
1321 return -ENOMEM;
1322
1323 return 0;
1324}
1325
1326module_init(klp_init);
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * core.c - Kernel Live Patching Core
4 *
5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6 * Copyright (C) 2014 SUSE
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/module.h>
12#include <linux/kernel.h>
13#include <linux/mutex.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/kallsyms.h>
17#include <linux/livepatch.h>
18#include <linux/elf.h>
19#include <linux/moduleloader.h>
20#include <linux/completion.h>
21#include <linux/memory.h>
22#include <asm/cacheflush.h>
23#include "core.h"
24#include "patch.h"
25#include "state.h"
26#include "transition.h"
27
28/*
29 * klp_mutex is a coarse lock which serializes access to klp data. All
30 * accesses to klp-related variables and structures must have mutex protection,
31 * except within the following functions which carefully avoid the need for it:
32 *
33 * - klp_ftrace_handler()
34 * - klp_update_patch_state()
35 */
36DEFINE_MUTEX(klp_mutex);
37
38/*
39 * Actively used patches: enabled or in transition. Note that replaced
40 * or disabled patches are not listed even though the related kernel
41 * module still can be loaded.
42 */
43LIST_HEAD(klp_patches);
44
45static struct kobject *klp_root_kobj;
46
47static bool klp_is_module(struct klp_object *obj)
48{
49 return obj->name;
50}
51
52/* sets obj->mod if object is not vmlinux and module is found */
53static void klp_find_object_module(struct klp_object *obj)
54{
55 struct module *mod;
56
57 if (!klp_is_module(obj))
58 return;
59
60 mutex_lock(&module_mutex);
61 /*
62 * We do not want to block removal of patched modules and therefore
63 * we do not take a reference here. The patches are removed by
64 * klp_module_going() instead.
65 */
66 mod = find_module(obj->name);
67 /*
68 * Do not mess work of klp_module_coming() and klp_module_going().
69 * Note that the patch might still be needed before klp_module_going()
70 * is called. Module functions can be called even in the GOING state
71 * until mod->exit() finishes. This is especially important for
72 * patches that modify semantic of the functions.
73 */
74 if (mod && mod->klp_alive)
75 obj->mod = mod;
76
77 mutex_unlock(&module_mutex);
78}
79
80static bool klp_initialized(void)
81{
82 return !!klp_root_kobj;
83}
84
85static struct klp_func *klp_find_func(struct klp_object *obj,
86 struct klp_func *old_func)
87{
88 struct klp_func *func;
89
90 klp_for_each_func(obj, func) {
91 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
92 (old_func->old_sympos == func->old_sympos)) {
93 return func;
94 }
95 }
96
97 return NULL;
98}
99
100static struct klp_object *klp_find_object(struct klp_patch *patch,
101 struct klp_object *old_obj)
102{
103 struct klp_object *obj;
104
105 klp_for_each_object(patch, obj) {
106 if (klp_is_module(old_obj)) {
107 if (klp_is_module(obj) &&
108 strcmp(old_obj->name, obj->name) == 0) {
109 return obj;
110 }
111 } else if (!klp_is_module(obj)) {
112 return obj;
113 }
114 }
115
116 return NULL;
117}
118
119struct klp_find_arg {
120 const char *objname;
121 const char *name;
122 unsigned long addr;
123 unsigned long count;
124 unsigned long pos;
125};
126
127static int klp_find_callback(void *data, const char *name,
128 struct module *mod, unsigned long addr)
129{
130 struct klp_find_arg *args = data;
131
132 if ((mod && !args->objname) || (!mod && args->objname))
133 return 0;
134
135 if (strcmp(args->name, name))
136 return 0;
137
138 if (args->objname && strcmp(args->objname, mod->name))
139 return 0;
140
141 args->addr = addr;
142 args->count++;
143
144 /*
145 * Finish the search when the symbol is found for the desired position
146 * or the position is not defined for a non-unique symbol.
147 */
148 if ((args->pos && (args->count == args->pos)) ||
149 (!args->pos && (args->count > 1)))
150 return 1;
151
152 return 0;
153}
154
155static int klp_find_object_symbol(const char *objname, const char *name,
156 unsigned long sympos, unsigned long *addr)
157{
158 struct klp_find_arg args = {
159 .objname = objname,
160 .name = name,
161 .addr = 0,
162 .count = 0,
163 .pos = sympos,
164 };
165
166 mutex_lock(&module_mutex);
167 if (objname)
168 module_kallsyms_on_each_symbol(klp_find_callback, &args);
169 else
170 kallsyms_on_each_symbol(klp_find_callback, &args);
171 mutex_unlock(&module_mutex);
172
173 /*
174 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
175 * otherwise ensure the symbol position count matches sympos.
176 */
177 if (args.addr == 0)
178 pr_err("symbol '%s' not found in symbol table\n", name);
179 else if (args.count > 1 && sympos == 0) {
180 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
181 name, objname);
182 } else if (sympos != args.count && sympos > 0) {
183 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
184 sympos, name, objname ? objname : "vmlinux");
185 } else {
186 *addr = args.addr;
187 return 0;
188 }
189
190 *addr = 0;
191 return -EINVAL;
192}
193
194static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
195 unsigned int symndx, Elf_Shdr *relasec,
196 const char *sec_objname)
197{
198 int i, cnt, ret;
199 char sym_objname[MODULE_NAME_LEN];
200 char sym_name[KSYM_NAME_LEN];
201 Elf_Rela *relas;
202 Elf_Sym *sym;
203 unsigned long sympos, addr;
204 bool sym_vmlinux;
205 bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
206
207 /*
208 * Since the field widths for sym_objname and sym_name in the sscanf()
209 * call are hard-coded and correspond to MODULE_NAME_LEN and
210 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
211 * and KSYM_NAME_LEN have the values we expect them to have.
212 *
213 * Because the value of MODULE_NAME_LEN can differ among architectures,
214 * we use the smallest/strictest upper bound possible (56, based on
215 * the current definition of MODULE_NAME_LEN) to prevent overflows.
216 */
217 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
218
219 relas = (Elf_Rela *) relasec->sh_addr;
220 /* For each rela in this klp relocation section */
221 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
222 sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
223 if (sym->st_shndx != SHN_LIVEPATCH) {
224 pr_err("symbol %s is not marked as a livepatch symbol\n",
225 strtab + sym->st_name);
226 return -EINVAL;
227 }
228
229 /* Format: .klp.sym.sym_objname.sym_name,sympos */
230 cnt = sscanf(strtab + sym->st_name,
231 ".klp.sym.%55[^.].%127[^,],%lu",
232 sym_objname, sym_name, &sympos);
233 if (cnt != 3) {
234 pr_err("symbol %s has an incorrectly formatted name\n",
235 strtab + sym->st_name);
236 return -EINVAL;
237 }
238
239 sym_vmlinux = !strcmp(sym_objname, "vmlinux");
240
241 /*
242 * Prevent module-specific KLP rela sections from referencing
243 * vmlinux symbols. This helps prevent ordering issues with
244 * module special section initializations. Presumably such
245 * symbols are exported and normal relas can be used instead.
246 */
247 if (!sec_vmlinux && sym_vmlinux) {
248 pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section",
249 sym_name);
250 return -EINVAL;
251 }
252
253 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
254 ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
255 sym_name, sympos, &addr);
256 if (ret)
257 return ret;
258
259 sym->st_value = addr;
260 }
261
262 return 0;
263}
264
265/*
266 * At a high-level, there are two types of klp relocation sections: those which
267 * reference symbols which live in vmlinux; and those which reference symbols
268 * which live in other modules. This function is called for both types:
269 *
270 * 1) When a klp module itself loads, the module code calls this function to
271 * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
272 * These relocations are written to the klp module text to allow the patched
273 * code/data to reference unexported vmlinux symbols. They're written as
274 * early as possible to ensure that other module init code (.e.g.,
275 * jump_label_apply_nops) can access any unexported vmlinux symbols which
276 * might be referenced by the klp module's special sections.
277 *
278 * 2) When a to-be-patched module loads -- or is already loaded when a
279 * corresponding klp module loads -- klp code calls this function to write
280 * module-specific klp relocations (.klp.rela.{module}.* sections). These
281 * are written to the klp module text to allow the patched code/data to
282 * reference symbols which live in the to-be-patched module or one of its
283 * module dependencies. Exported symbols are supported, in addition to
284 * unexported symbols, in order to enable late module patching, which allows
285 * the to-be-patched module to be loaded and patched sometime *after* the
286 * klp module is loaded.
287 */
288int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
289 const char *shstrtab, const char *strtab,
290 unsigned int symndx, unsigned int secndx,
291 const char *objname)
292{
293 int cnt, ret;
294 char sec_objname[MODULE_NAME_LEN];
295 Elf_Shdr *sec = sechdrs + secndx;
296
297 /*
298 * Format: .klp.rela.sec_objname.section_name
299 * See comment in klp_resolve_symbols() for an explanation
300 * of the selected field width value.
301 */
302 cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
303 sec_objname);
304 if (cnt != 1) {
305 pr_err("section %s has an incorrectly formatted name\n",
306 shstrtab + sec->sh_name);
307 return -EINVAL;
308 }
309
310 if (strcmp(objname ? objname : "vmlinux", sec_objname))
311 return 0;
312
313 ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
314 if (ret)
315 return ret;
316
317 return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
318}
319
320/*
321 * Sysfs Interface
322 *
323 * /sys/kernel/livepatch
324 * /sys/kernel/livepatch/<patch>
325 * /sys/kernel/livepatch/<patch>/enabled
326 * /sys/kernel/livepatch/<patch>/transition
327 * /sys/kernel/livepatch/<patch>/force
328 * /sys/kernel/livepatch/<patch>/<object>
329 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
330 */
331static int __klp_disable_patch(struct klp_patch *patch);
332
333static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
334 const char *buf, size_t count)
335{
336 struct klp_patch *patch;
337 int ret;
338 bool enabled;
339
340 ret = kstrtobool(buf, &enabled);
341 if (ret)
342 return ret;
343
344 patch = container_of(kobj, struct klp_patch, kobj);
345
346 mutex_lock(&klp_mutex);
347
348 if (patch->enabled == enabled) {
349 /* already in requested state */
350 ret = -EINVAL;
351 goto out;
352 }
353
354 /*
355 * Allow to reverse a pending transition in both ways. It might be
356 * necessary to complete the transition without forcing and breaking
357 * the system integrity.
358 *
359 * Do not allow to re-enable a disabled patch.
360 */
361 if (patch == klp_transition_patch)
362 klp_reverse_transition();
363 else if (!enabled)
364 ret = __klp_disable_patch(patch);
365 else
366 ret = -EINVAL;
367
368out:
369 mutex_unlock(&klp_mutex);
370
371 if (ret)
372 return ret;
373 return count;
374}
375
376static ssize_t enabled_show(struct kobject *kobj,
377 struct kobj_attribute *attr, char *buf)
378{
379 struct klp_patch *patch;
380
381 patch = container_of(kobj, struct klp_patch, kobj);
382 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
383}
384
385static ssize_t transition_show(struct kobject *kobj,
386 struct kobj_attribute *attr, char *buf)
387{
388 struct klp_patch *patch;
389
390 patch = container_of(kobj, struct klp_patch, kobj);
391 return snprintf(buf, PAGE_SIZE-1, "%d\n",
392 patch == klp_transition_patch);
393}
394
395static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
396 const char *buf, size_t count)
397{
398 struct klp_patch *patch;
399 int ret;
400 bool val;
401
402 ret = kstrtobool(buf, &val);
403 if (ret)
404 return ret;
405
406 if (!val)
407 return count;
408
409 mutex_lock(&klp_mutex);
410
411 patch = container_of(kobj, struct klp_patch, kobj);
412 if (patch != klp_transition_patch) {
413 mutex_unlock(&klp_mutex);
414 return -EINVAL;
415 }
416
417 klp_force_transition();
418
419 mutex_unlock(&klp_mutex);
420
421 return count;
422}
423
424static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
425static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
426static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
427static struct attribute *klp_patch_attrs[] = {
428 &enabled_kobj_attr.attr,
429 &transition_kobj_attr.attr,
430 &force_kobj_attr.attr,
431 NULL
432};
433ATTRIBUTE_GROUPS(klp_patch);
434
435static void klp_free_object_dynamic(struct klp_object *obj)
436{
437 kfree(obj->name);
438 kfree(obj);
439}
440
441static void klp_init_func_early(struct klp_object *obj,
442 struct klp_func *func);
443static void klp_init_object_early(struct klp_patch *patch,
444 struct klp_object *obj);
445
446static struct klp_object *klp_alloc_object_dynamic(const char *name,
447 struct klp_patch *patch)
448{
449 struct klp_object *obj;
450
451 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
452 if (!obj)
453 return NULL;
454
455 if (name) {
456 obj->name = kstrdup(name, GFP_KERNEL);
457 if (!obj->name) {
458 kfree(obj);
459 return NULL;
460 }
461 }
462
463 klp_init_object_early(patch, obj);
464 obj->dynamic = true;
465
466 return obj;
467}
468
469static void klp_free_func_nop(struct klp_func *func)
470{
471 kfree(func->old_name);
472 kfree(func);
473}
474
475static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
476 struct klp_object *obj)
477{
478 struct klp_func *func;
479
480 func = kzalloc(sizeof(*func), GFP_KERNEL);
481 if (!func)
482 return NULL;
483
484 if (old_func->old_name) {
485 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
486 if (!func->old_name) {
487 kfree(func);
488 return NULL;
489 }
490 }
491
492 klp_init_func_early(obj, func);
493 /*
494 * func->new_func is same as func->old_func. These addresses are
495 * set when the object is loaded, see klp_init_object_loaded().
496 */
497 func->old_sympos = old_func->old_sympos;
498 func->nop = true;
499
500 return func;
501}
502
503static int klp_add_object_nops(struct klp_patch *patch,
504 struct klp_object *old_obj)
505{
506 struct klp_object *obj;
507 struct klp_func *func, *old_func;
508
509 obj = klp_find_object(patch, old_obj);
510
511 if (!obj) {
512 obj = klp_alloc_object_dynamic(old_obj->name, patch);
513 if (!obj)
514 return -ENOMEM;
515 }
516
517 klp_for_each_func(old_obj, old_func) {
518 func = klp_find_func(obj, old_func);
519 if (func)
520 continue;
521
522 func = klp_alloc_func_nop(old_func, obj);
523 if (!func)
524 return -ENOMEM;
525 }
526
527 return 0;
528}
529
530/*
531 * Add 'nop' functions which simply return to the caller to run
532 * the original function. The 'nop' functions are added to a
533 * patch to facilitate a 'replace' mode.
534 */
535static int klp_add_nops(struct klp_patch *patch)
536{
537 struct klp_patch *old_patch;
538 struct klp_object *old_obj;
539
540 klp_for_each_patch(old_patch) {
541 klp_for_each_object(old_patch, old_obj) {
542 int err;
543
544 err = klp_add_object_nops(patch, old_obj);
545 if (err)
546 return err;
547 }
548 }
549
550 return 0;
551}
552
553static void klp_kobj_release_patch(struct kobject *kobj)
554{
555 struct klp_patch *patch;
556
557 patch = container_of(kobj, struct klp_patch, kobj);
558 complete(&patch->finish);
559}
560
561static struct kobj_type klp_ktype_patch = {
562 .release = klp_kobj_release_patch,
563 .sysfs_ops = &kobj_sysfs_ops,
564 .default_groups = klp_patch_groups,
565};
566
567static void klp_kobj_release_object(struct kobject *kobj)
568{
569 struct klp_object *obj;
570
571 obj = container_of(kobj, struct klp_object, kobj);
572
573 if (obj->dynamic)
574 klp_free_object_dynamic(obj);
575}
576
577static struct kobj_type klp_ktype_object = {
578 .release = klp_kobj_release_object,
579 .sysfs_ops = &kobj_sysfs_ops,
580};
581
582static void klp_kobj_release_func(struct kobject *kobj)
583{
584 struct klp_func *func;
585
586 func = container_of(kobj, struct klp_func, kobj);
587
588 if (func->nop)
589 klp_free_func_nop(func);
590}
591
592static struct kobj_type klp_ktype_func = {
593 .release = klp_kobj_release_func,
594 .sysfs_ops = &kobj_sysfs_ops,
595};
596
597static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
598{
599 struct klp_func *func, *tmp_func;
600
601 klp_for_each_func_safe(obj, func, tmp_func) {
602 if (nops_only && !func->nop)
603 continue;
604
605 list_del(&func->node);
606 kobject_put(&func->kobj);
607 }
608}
609
610/* Clean up when a patched object is unloaded */
611static void klp_free_object_loaded(struct klp_object *obj)
612{
613 struct klp_func *func;
614
615 obj->mod = NULL;
616
617 klp_for_each_func(obj, func) {
618 func->old_func = NULL;
619
620 if (func->nop)
621 func->new_func = NULL;
622 }
623}
624
625static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
626{
627 struct klp_object *obj, *tmp_obj;
628
629 klp_for_each_object_safe(patch, obj, tmp_obj) {
630 __klp_free_funcs(obj, nops_only);
631
632 if (nops_only && !obj->dynamic)
633 continue;
634
635 list_del(&obj->node);
636 kobject_put(&obj->kobj);
637 }
638}
639
640static void klp_free_objects(struct klp_patch *patch)
641{
642 __klp_free_objects(patch, false);
643}
644
645static void klp_free_objects_dynamic(struct klp_patch *patch)
646{
647 __klp_free_objects(patch, true);
648}
649
650/*
651 * This function implements the free operations that can be called safely
652 * under klp_mutex.
653 *
654 * The operation must be completed by calling klp_free_patch_finish()
655 * outside klp_mutex.
656 */
657static void klp_free_patch_start(struct klp_patch *patch)
658{
659 if (!list_empty(&patch->list))
660 list_del(&patch->list);
661
662 klp_free_objects(patch);
663}
664
665/*
666 * This function implements the free part that must be called outside
667 * klp_mutex.
668 *
669 * It must be called after klp_free_patch_start(). And it has to be
670 * the last function accessing the livepatch structures when the patch
671 * gets disabled.
672 */
673static void klp_free_patch_finish(struct klp_patch *patch)
674{
675 /*
676 * Avoid deadlock with enabled_store() sysfs callback by
677 * calling this outside klp_mutex. It is safe because
678 * this is called when the patch gets disabled and it
679 * cannot get enabled again.
680 */
681 kobject_put(&patch->kobj);
682 wait_for_completion(&patch->finish);
683
684 /* Put the module after the last access to struct klp_patch. */
685 if (!patch->forced)
686 module_put(patch->mod);
687}
688
689/*
690 * The livepatch might be freed from sysfs interface created by the patch.
691 * This work allows to wait until the interface is destroyed in a separate
692 * context.
693 */
694static void klp_free_patch_work_fn(struct work_struct *work)
695{
696 struct klp_patch *patch =
697 container_of(work, struct klp_patch, free_work);
698
699 klp_free_patch_finish(patch);
700}
701
702void klp_free_patch_async(struct klp_patch *patch)
703{
704 klp_free_patch_start(patch);
705 schedule_work(&patch->free_work);
706}
707
708void klp_free_replaced_patches_async(struct klp_patch *new_patch)
709{
710 struct klp_patch *old_patch, *tmp_patch;
711
712 klp_for_each_patch_safe(old_patch, tmp_patch) {
713 if (old_patch == new_patch)
714 return;
715 klp_free_patch_async(old_patch);
716 }
717}
718
719static int klp_init_func(struct klp_object *obj, struct klp_func *func)
720{
721 if (!func->old_name)
722 return -EINVAL;
723
724 /*
725 * NOPs get the address later. The patched module must be loaded,
726 * see klp_init_object_loaded().
727 */
728 if (!func->new_func && !func->nop)
729 return -EINVAL;
730
731 if (strlen(func->old_name) >= KSYM_NAME_LEN)
732 return -EINVAL;
733
734 INIT_LIST_HEAD(&func->stack_node);
735 func->patched = false;
736 func->transition = false;
737
738 /* The format for the sysfs directory is <function,sympos> where sympos
739 * is the nth occurrence of this symbol in kallsyms for the patched
740 * object. If the user selects 0 for old_sympos, then 1 will be used
741 * since a unique symbol will be the first occurrence.
742 */
743 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
744 func->old_name,
745 func->old_sympos ? func->old_sympos : 1);
746}
747
748static int klp_apply_object_relocs(struct klp_patch *patch,
749 struct klp_object *obj)
750{
751 int i, ret;
752 struct klp_modinfo *info = patch->mod->klp_info;
753
754 for (i = 1; i < info->hdr.e_shnum; i++) {
755 Elf_Shdr *sec = info->sechdrs + i;
756
757 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
758 continue;
759
760 ret = klp_apply_section_relocs(patch->mod, info->sechdrs,
761 info->secstrings,
762 patch->mod->core_kallsyms.strtab,
763 info->symndx, i, obj->name);
764 if (ret)
765 return ret;
766 }
767
768 return 0;
769}
770
771/* parts of the initialization that is done only when the object is loaded */
772static int klp_init_object_loaded(struct klp_patch *patch,
773 struct klp_object *obj)
774{
775 struct klp_func *func;
776 int ret;
777
778 if (klp_is_module(obj)) {
779 /*
780 * Only write module-specific relocations here
781 * (.klp.rela.{module}.*). vmlinux-specific relocations were
782 * written earlier during the initialization of the klp module
783 * itself.
784 */
785 ret = klp_apply_object_relocs(patch, obj);
786 if (ret)
787 return ret;
788 }
789
790 klp_for_each_func(obj, func) {
791 ret = klp_find_object_symbol(obj->name, func->old_name,
792 func->old_sympos,
793 (unsigned long *)&func->old_func);
794 if (ret)
795 return ret;
796
797 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
798 &func->old_size, NULL);
799 if (!ret) {
800 pr_err("kallsyms size lookup failed for '%s'\n",
801 func->old_name);
802 return -ENOENT;
803 }
804
805 if (func->nop)
806 func->new_func = func->old_func;
807
808 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
809 &func->new_size, NULL);
810 if (!ret) {
811 pr_err("kallsyms size lookup failed for '%s' replacement\n",
812 func->old_name);
813 return -ENOENT;
814 }
815 }
816
817 return 0;
818}
819
820static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
821{
822 struct klp_func *func;
823 int ret;
824 const char *name;
825
826 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
827 return -EINVAL;
828
829 obj->patched = false;
830 obj->mod = NULL;
831
832 klp_find_object_module(obj);
833
834 name = klp_is_module(obj) ? obj->name : "vmlinux";
835 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
836 if (ret)
837 return ret;
838
839 klp_for_each_func(obj, func) {
840 ret = klp_init_func(obj, func);
841 if (ret)
842 return ret;
843 }
844
845 if (klp_is_object_loaded(obj))
846 ret = klp_init_object_loaded(patch, obj);
847
848 return ret;
849}
850
851static void klp_init_func_early(struct klp_object *obj,
852 struct klp_func *func)
853{
854 kobject_init(&func->kobj, &klp_ktype_func);
855 list_add_tail(&func->node, &obj->func_list);
856}
857
858static void klp_init_object_early(struct klp_patch *patch,
859 struct klp_object *obj)
860{
861 INIT_LIST_HEAD(&obj->func_list);
862 kobject_init(&obj->kobj, &klp_ktype_object);
863 list_add_tail(&obj->node, &patch->obj_list);
864}
865
866static int klp_init_patch_early(struct klp_patch *patch)
867{
868 struct klp_object *obj;
869 struct klp_func *func;
870
871 if (!patch->objs)
872 return -EINVAL;
873
874 INIT_LIST_HEAD(&patch->list);
875 INIT_LIST_HEAD(&patch->obj_list);
876 kobject_init(&patch->kobj, &klp_ktype_patch);
877 patch->enabled = false;
878 patch->forced = false;
879 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
880 init_completion(&patch->finish);
881
882 klp_for_each_object_static(patch, obj) {
883 if (!obj->funcs)
884 return -EINVAL;
885
886 klp_init_object_early(patch, obj);
887
888 klp_for_each_func_static(obj, func) {
889 klp_init_func_early(obj, func);
890 }
891 }
892
893 if (!try_module_get(patch->mod))
894 return -ENODEV;
895
896 return 0;
897}
898
899static int klp_init_patch(struct klp_patch *patch)
900{
901 struct klp_object *obj;
902 int ret;
903
904 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
905 if (ret)
906 return ret;
907
908 if (patch->replace) {
909 ret = klp_add_nops(patch);
910 if (ret)
911 return ret;
912 }
913
914 klp_for_each_object(patch, obj) {
915 ret = klp_init_object(patch, obj);
916 if (ret)
917 return ret;
918 }
919
920 list_add_tail(&patch->list, &klp_patches);
921
922 return 0;
923}
924
925static int __klp_disable_patch(struct klp_patch *patch)
926{
927 struct klp_object *obj;
928
929 if (WARN_ON(!patch->enabled))
930 return -EINVAL;
931
932 if (klp_transition_patch)
933 return -EBUSY;
934
935 klp_init_transition(patch, KLP_UNPATCHED);
936
937 klp_for_each_object(patch, obj)
938 if (obj->patched)
939 klp_pre_unpatch_callback(obj);
940
941 /*
942 * Enforce the order of the func->transition writes in
943 * klp_init_transition() and the TIF_PATCH_PENDING writes in
944 * klp_start_transition(). In the rare case where klp_ftrace_handler()
945 * is called shortly after klp_update_patch_state() switches the task,
946 * this ensures the handler sees that func->transition is set.
947 */
948 smp_wmb();
949
950 klp_start_transition();
951 patch->enabled = false;
952 klp_try_complete_transition();
953
954 return 0;
955}
956
957static int __klp_enable_patch(struct klp_patch *patch)
958{
959 struct klp_object *obj;
960 int ret;
961
962 if (klp_transition_patch)
963 return -EBUSY;
964
965 if (WARN_ON(patch->enabled))
966 return -EINVAL;
967
968 pr_notice("enabling patch '%s'\n", patch->mod->name);
969
970 klp_init_transition(patch, KLP_PATCHED);
971
972 /*
973 * Enforce the order of the func->transition writes in
974 * klp_init_transition() and the ops->func_stack writes in
975 * klp_patch_object(), so that klp_ftrace_handler() will see the
976 * func->transition updates before the handler is registered and the
977 * new funcs become visible to the handler.
978 */
979 smp_wmb();
980
981 klp_for_each_object(patch, obj) {
982 if (!klp_is_object_loaded(obj))
983 continue;
984
985 ret = klp_pre_patch_callback(obj);
986 if (ret) {
987 pr_warn("pre-patch callback failed for object '%s'\n",
988 klp_is_module(obj) ? obj->name : "vmlinux");
989 goto err;
990 }
991
992 ret = klp_patch_object(obj);
993 if (ret) {
994 pr_warn("failed to patch object '%s'\n",
995 klp_is_module(obj) ? obj->name : "vmlinux");
996 goto err;
997 }
998 }
999
1000 klp_start_transition();
1001 patch->enabled = true;
1002 klp_try_complete_transition();
1003
1004 return 0;
1005err:
1006 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
1007
1008 klp_cancel_transition();
1009 return ret;
1010}
1011
1012/**
1013 * klp_enable_patch() - enable the livepatch
1014 * @patch: patch to be enabled
1015 *
1016 * Initializes the data structure associated with the patch, creates the sysfs
1017 * interface, performs the needed symbol lookups and code relocations,
1018 * registers the patched functions with ftrace.
1019 *
1020 * This function is supposed to be called from the livepatch module_init()
1021 * callback.
1022 *
1023 * Return: 0 on success, otherwise error
1024 */
1025int klp_enable_patch(struct klp_patch *patch)
1026{
1027 int ret;
1028
1029 if (!patch || !patch->mod)
1030 return -EINVAL;
1031
1032 if (!is_livepatch_module(patch->mod)) {
1033 pr_err("module %s is not marked as a livepatch module\n",
1034 patch->mod->name);
1035 return -EINVAL;
1036 }
1037
1038 if (!klp_initialized())
1039 return -ENODEV;
1040
1041 if (!klp_have_reliable_stack()) {
1042 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1043 pr_warn("The livepatch transition may never complete.\n");
1044 }
1045
1046 mutex_lock(&klp_mutex);
1047
1048 if (!klp_is_patch_compatible(patch)) {
1049 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1050 patch->mod->name);
1051 mutex_unlock(&klp_mutex);
1052 return -EINVAL;
1053 }
1054
1055 ret = klp_init_patch_early(patch);
1056 if (ret) {
1057 mutex_unlock(&klp_mutex);
1058 return ret;
1059 }
1060
1061 ret = klp_init_patch(patch);
1062 if (ret)
1063 goto err;
1064
1065 ret = __klp_enable_patch(patch);
1066 if (ret)
1067 goto err;
1068
1069 mutex_unlock(&klp_mutex);
1070
1071 return 0;
1072
1073err:
1074 klp_free_patch_start(patch);
1075
1076 mutex_unlock(&klp_mutex);
1077
1078 klp_free_patch_finish(patch);
1079
1080 return ret;
1081}
1082EXPORT_SYMBOL_GPL(klp_enable_patch);
1083
1084/*
1085 * This function unpatches objects from the replaced livepatches.
1086 *
1087 * We could be pretty aggressive here. It is called in the situation where
1088 * these structures are no longer accessed from the ftrace handler.
1089 * All functions are redirected by the klp_transition_patch. They
1090 * use either a new code or they are in the original code because
1091 * of the special nop function patches.
1092 *
1093 * The only exception is when the transition was forced. In this case,
1094 * klp_ftrace_handler() might still see the replaced patch on the stack.
1095 * Fortunately, it is carefully designed to work with removed functions
1096 * thanks to RCU. We only have to keep the patches on the system. Also
1097 * this is handled transparently by patch->module_put.
1098 */
1099void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1100{
1101 struct klp_patch *old_patch;
1102
1103 klp_for_each_patch(old_patch) {
1104 if (old_patch == new_patch)
1105 return;
1106
1107 old_patch->enabled = false;
1108 klp_unpatch_objects(old_patch);
1109 }
1110}
1111
1112/*
1113 * This function removes the dynamically allocated 'nop' functions.
1114 *
1115 * We could be pretty aggressive. NOPs do not change the existing
1116 * behavior except for adding unnecessary delay by the ftrace handler.
1117 *
1118 * It is safe even when the transition was forced. The ftrace handler
1119 * will see a valid ops->func_stack entry thanks to RCU.
1120 *
1121 * We could even free the NOPs structures. They must be the last entry
1122 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1123 * It does the same as klp_synchronize_transition() to make sure that
1124 * nobody is inside the ftrace handler once the operation finishes.
1125 *
1126 * IMPORTANT: It must be called right after removing the replaced patches!
1127 */
1128void klp_discard_nops(struct klp_patch *new_patch)
1129{
1130 klp_unpatch_objects_dynamic(klp_transition_patch);
1131 klp_free_objects_dynamic(klp_transition_patch);
1132}
1133
1134/*
1135 * Remove parts of patches that touch a given kernel module. The list of
1136 * patches processed might be limited. When limit is NULL, all patches
1137 * will be handled.
1138 */
1139static void klp_cleanup_module_patches_limited(struct module *mod,
1140 struct klp_patch *limit)
1141{
1142 struct klp_patch *patch;
1143 struct klp_object *obj;
1144
1145 klp_for_each_patch(patch) {
1146 if (patch == limit)
1147 break;
1148
1149 klp_for_each_object(patch, obj) {
1150 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1151 continue;
1152
1153 if (patch != klp_transition_patch)
1154 klp_pre_unpatch_callback(obj);
1155
1156 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1157 patch->mod->name, obj->mod->name);
1158 klp_unpatch_object(obj);
1159
1160 klp_post_unpatch_callback(obj);
1161
1162 klp_free_object_loaded(obj);
1163 break;
1164 }
1165 }
1166}
1167
1168int klp_module_coming(struct module *mod)
1169{
1170 int ret;
1171 struct klp_patch *patch;
1172 struct klp_object *obj;
1173
1174 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1175 return -EINVAL;
1176
1177 if (!strcmp(mod->name, "vmlinux")) {
1178 pr_err("vmlinux.ko: invalid module name");
1179 return -EINVAL;
1180 }
1181
1182 mutex_lock(&klp_mutex);
1183 /*
1184 * Each module has to know that klp_module_coming()
1185 * has been called. We never know what module will
1186 * get patched by a new patch.
1187 */
1188 mod->klp_alive = true;
1189
1190 klp_for_each_patch(patch) {
1191 klp_for_each_object(patch, obj) {
1192 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1193 continue;
1194
1195 obj->mod = mod;
1196
1197 ret = klp_init_object_loaded(patch, obj);
1198 if (ret) {
1199 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1200 patch->mod->name, obj->mod->name, ret);
1201 goto err;
1202 }
1203
1204 pr_notice("applying patch '%s' to loading module '%s'\n",
1205 patch->mod->name, obj->mod->name);
1206
1207 ret = klp_pre_patch_callback(obj);
1208 if (ret) {
1209 pr_warn("pre-patch callback failed for object '%s'\n",
1210 obj->name);
1211 goto err;
1212 }
1213
1214 ret = klp_patch_object(obj);
1215 if (ret) {
1216 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1217 patch->mod->name, obj->mod->name, ret);
1218
1219 klp_post_unpatch_callback(obj);
1220 goto err;
1221 }
1222
1223 if (patch != klp_transition_patch)
1224 klp_post_patch_callback(obj);
1225
1226 break;
1227 }
1228 }
1229
1230 mutex_unlock(&klp_mutex);
1231
1232 return 0;
1233
1234err:
1235 /*
1236 * If a patch is unsuccessfully applied, return
1237 * error to the module loader.
1238 */
1239 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1240 patch->mod->name, obj->mod->name, obj->mod->name);
1241 mod->klp_alive = false;
1242 obj->mod = NULL;
1243 klp_cleanup_module_patches_limited(mod, patch);
1244 mutex_unlock(&klp_mutex);
1245
1246 return ret;
1247}
1248
1249void klp_module_going(struct module *mod)
1250{
1251 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1252 mod->state != MODULE_STATE_COMING))
1253 return;
1254
1255 mutex_lock(&klp_mutex);
1256 /*
1257 * Each module has to know that klp_module_going()
1258 * has been called. We never know what module will
1259 * get patched by a new patch.
1260 */
1261 mod->klp_alive = false;
1262
1263 klp_cleanup_module_patches_limited(mod, NULL);
1264
1265 mutex_unlock(&klp_mutex);
1266}
1267
1268static int __init klp_init(void)
1269{
1270 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1271 if (!klp_root_kobj)
1272 return -ENOMEM;
1273
1274 return 0;
1275}
1276
1277module_init(klp_init);