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b700e7f0 SJ |
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 | ||
3c33f5b9 JP |
32 | /** |
33 | * struct klp_ops - structure for tracking registered ftrace ops structs | |
34 | * | |
35 | * A single ftrace_ops is shared between all enabled replacement functions | |
36 | * (klp_func structs) which have the same old_addr. This allows the switch | |
37 | * between function versions to happen instantaneously by updating the klp_ops | |
38 | * struct's func_stack list. The winner is the klp_func at the top of the | |
39 | * func_stack (front of the list). | |
40 | * | |
41 | * @node: node for the global klp_ops list | |
42 | * @func_stack: list head for the stack of klp_func's (active func is on top) | |
43 | * @fops: registered ftrace ops struct | |
b700e7f0 | 44 | */ |
3c33f5b9 JP |
45 | struct klp_ops { |
46 | struct list_head node; | |
47 | struct list_head func_stack; | |
48 | struct ftrace_ops fops; | |
49 | }; | |
b700e7f0 | 50 | |
3c33f5b9 JP |
51 | /* |
52 | * The klp_mutex protects the global lists and state transitions of any | |
53 | * structure reachable from them. References to any structure must be obtained | |
54 | * under mutex protection (except in klp_ftrace_handler(), which uses RCU to | |
55 | * ensure it gets consistent data). | |
56 | */ | |
b700e7f0 | 57 | static DEFINE_MUTEX(klp_mutex); |
3c33f5b9 | 58 | |
b700e7f0 | 59 | static LIST_HEAD(klp_patches); |
3c33f5b9 | 60 | static LIST_HEAD(klp_ops); |
b700e7f0 SJ |
61 | |
62 | static struct kobject *klp_root_kobj; | |
63 | ||
3c33f5b9 JP |
64 | static struct klp_ops *klp_find_ops(unsigned long old_addr) |
65 | { | |
66 | struct klp_ops *ops; | |
67 | struct klp_func *func; | |
68 | ||
69 | list_for_each_entry(ops, &klp_ops, node) { | |
70 | func = list_first_entry(&ops->func_stack, struct klp_func, | |
71 | stack_node); | |
72 | if (func->old_addr == old_addr) | |
73 | return ops; | |
74 | } | |
75 | ||
76 | return NULL; | |
77 | } | |
78 | ||
b700e7f0 SJ |
79 | static bool klp_is_module(struct klp_object *obj) |
80 | { | |
81 | return obj->name; | |
82 | } | |
83 | ||
84 | static bool klp_is_object_loaded(struct klp_object *obj) | |
85 | { | |
86 | return !obj->name || obj->mod; | |
87 | } | |
88 | ||
89 | /* sets obj->mod if object is not vmlinux and module is found */ | |
90 | static void klp_find_object_module(struct klp_object *obj) | |
91 | { | |
92 | if (!klp_is_module(obj)) | |
93 | return; | |
94 | ||
95 | mutex_lock(&module_mutex); | |
96 | /* | |
97 | * We don't need to take a reference on the module here because we have | |
98 | * the klp_mutex, which is also taken by the module notifier. This | |
99 | * prevents any module from unloading until we release the klp_mutex. | |
100 | */ | |
101 | obj->mod = find_module(obj->name); | |
102 | mutex_unlock(&module_mutex); | |
103 | } | |
104 | ||
105 | /* klp_mutex must be held by caller */ | |
106 | static bool klp_is_patch_registered(struct klp_patch *patch) | |
107 | { | |
108 | struct klp_patch *mypatch; | |
109 | ||
110 | list_for_each_entry(mypatch, &klp_patches, list) | |
111 | if (mypatch == patch) | |
112 | return true; | |
113 | ||
114 | return false; | |
115 | } | |
116 | ||
117 | static bool klp_initialized(void) | |
118 | { | |
119 | return klp_root_kobj; | |
120 | } | |
121 | ||
122 | struct klp_find_arg { | |
123 | const char *objname; | |
124 | const char *name; | |
125 | unsigned long addr; | |
126 | /* | |
127 | * If count == 0, the symbol was not found. If count == 1, a unique | |
128 | * match was found and addr is set. If count > 1, there is | |
129 | * unresolvable ambiguity among "count" number of symbols with the same | |
130 | * name in the same object. | |
131 | */ | |
132 | unsigned long count; | |
133 | }; | |
134 | ||
135 | static int klp_find_callback(void *data, const char *name, | |
136 | struct module *mod, unsigned long addr) | |
137 | { | |
138 | struct klp_find_arg *args = data; | |
139 | ||
140 | if ((mod && !args->objname) || (!mod && args->objname)) | |
141 | return 0; | |
142 | ||
143 | if (strcmp(args->name, name)) | |
144 | return 0; | |
145 | ||
146 | if (args->objname && strcmp(args->objname, mod->name)) | |
147 | return 0; | |
148 | ||
149 | /* | |
150 | * args->addr might be overwritten if another match is found | |
151 | * but klp_find_object_symbol() handles this and only returns the | |
152 | * addr if count == 1. | |
153 | */ | |
154 | args->addr = addr; | |
155 | args->count++; | |
156 | ||
157 | return 0; | |
158 | } | |
159 | ||
160 | static int klp_find_object_symbol(const char *objname, const char *name, | |
161 | unsigned long *addr) | |
162 | { | |
163 | struct klp_find_arg args = { | |
164 | .objname = objname, | |
165 | .name = name, | |
166 | .addr = 0, | |
167 | .count = 0 | |
168 | }; | |
169 | ||
170 | kallsyms_on_each_symbol(klp_find_callback, &args); | |
171 | ||
172 | if (args.count == 0) | |
173 | pr_err("symbol '%s' not found in symbol table\n", name); | |
174 | else if (args.count > 1) | |
175 | pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n", | |
176 | args.count, name, objname); | |
177 | else { | |
178 | *addr = args.addr; | |
179 | return 0; | |
180 | } | |
181 | ||
182 | *addr = 0; | |
183 | return -EINVAL; | |
184 | } | |
185 | ||
186 | struct klp_verify_args { | |
187 | const char *name; | |
188 | const unsigned long addr; | |
189 | }; | |
190 | ||
191 | static int klp_verify_callback(void *data, const char *name, | |
192 | struct module *mod, unsigned long addr) | |
193 | { | |
194 | struct klp_verify_args *args = data; | |
195 | ||
196 | if (!mod && | |
197 | !strcmp(args->name, name) && | |
198 | args->addr == addr) | |
199 | return 1; | |
200 | ||
201 | return 0; | |
202 | } | |
203 | ||
204 | static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr) | |
205 | { | |
206 | struct klp_verify_args args = { | |
207 | .name = name, | |
208 | .addr = addr, | |
209 | }; | |
210 | ||
211 | if (kallsyms_on_each_symbol(klp_verify_callback, &args)) | |
212 | return 0; | |
213 | ||
f638f4dc | 214 | pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n", |
b700e7f0 SJ |
215 | name, addr); |
216 | return -EINVAL; | |
217 | } | |
218 | ||
219 | static int klp_find_verify_func_addr(struct klp_object *obj, | |
220 | struct klp_func *func) | |
221 | { | |
222 | int ret; | |
223 | ||
224 | #if defined(CONFIG_RANDOMIZE_BASE) | |
225 | /* KASLR is enabled, disregard old_addr from user */ | |
226 | func->old_addr = 0; | |
227 | #endif | |
228 | ||
229 | if (!func->old_addr || klp_is_module(obj)) | |
230 | ret = klp_find_object_symbol(obj->name, func->old_name, | |
231 | &func->old_addr); | |
232 | else | |
233 | ret = klp_verify_vmlinux_symbol(func->old_name, | |
234 | func->old_addr); | |
235 | ||
236 | return ret; | |
237 | } | |
238 | ||
239 | /* | |
240 | * external symbols are located outside the parent object (where the parent | |
241 | * object is either vmlinux or the kmod being patched). | |
242 | */ | |
243 | static int klp_find_external_symbol(struct module *pmod, const char *name, | |
244 | unsigned long *addr) | |
245 | { | |
246 | const struct kernel_symbol *sym; | |
247 | ||
248 | /* first, check if it's an exported symbol */ | |
249 | preempt_disable(); | |
250 | sym = find_symbol(name, NULL, NULL, true, true); | |
251 | preempt_enable(); | |
252 | if (sym) { | |
253 | *addr = sym->value; | |
254 | return 0; | |
255 | } | |
256 | ||
257 | /* otherwise check if it's in another .o within the patch module */ | |
258 | return klp_find_object_symbol(pmod->name, name, addr); | |
259 | } | |
260 | ||
261 | static int klp_write_object_relocations(struct module *pmod, | |
262 | struct klp_object *obj) | |
263 | { | |
264 | int ret; | |
265 | struct klp_reloc *reloc; | |
266 | ||
267 | if (WARN_ON(!klp_is_object_loaded(obj))) | |
268 | return -EINVAL; | |
269 | ||
270 | if (WARN_ON(!obj->relocs)) | |
271 | return -EINVAL; | |
272 | ||
273 | for (reloc = obj->relocs; reloc->name; reloc++) { | |
274 | if (!klp_is_module(obj)) { | |
275 | ret = klp_verify_vmlinux_symbol(reloc->name, | |
276 | reloc->val); | |
277 | if (ret) | |
278 | return ret; | |
279 | } else { | |
280 | /* module, reloc->val needs to be discovered */ | |
281 | if (reloc->external) | |
282 | ret = klp_find_external_symbol(pmod, | |
283 | reloc->name, | |
284 | &reloc->val); | |
285 | else | |
286 | ret = klp_find_object_symbol(obj->mod->name, | |
287 | reloc->name, | |
288 | &reloc->val); | |
289 | if (ret) | |
290 | return ret; | |
291 | } | |
292 | ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc, | |
293 | reloc->val + reloc->addend); | |
294 | if (ret) { | |
295 | pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n", | |
296 | reloc->name, reloc->val, ret); | |
297 | return ret; | |
298 | } | |
299 | } | |
300 | ||
301 | return 0; | |
302 | } | |
303 | ||
304 | static void notrace klp_ftrace_handler(unsigned long ip, | |
305 | unsigned long parent_ip, | |
3c33f5b9 | 306 | struct ftrace_ops *fops, |
b700e7f0 SJ |
307 | struct pt_regs *regs) |
308 | { | |
3c33f5b9 JP |
309 | struct klp_ops *ops; |
310 | struct klp_func *func; | |
311 | ||
312 | ops = container_of(fops, struct klp_ops, fops); | |
313 | ||
314 | rcu_read_lock(); | |
315 | func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, | |
316 | stack_node); | |
317 | rcu_read_unlock(); | |
318 | ||
319 | if (WARN_ON_ONCE(!func)) | |
320 | return; | |
b700e7f0 | 321 | |
b5bfc517 | 322 | klp_arch_set_pc(regs, (unsigned long)func->new_func); |
b700e7f0 SJ |
323 | } |
324 | ||
325 | static int klp_disable_func(struct klp_func *func) | |
326 | { | |
3c33f5b9 | 327 | struct klp_ops *ops; |
b700e7f0 SJ |
328 | int ret; |
329 | ||
330 | if (WARN_ON(func->state != KLP_ENABLED)) | |
331 | return -EINVAL; | |
332 | ||
333 | if (WARN_ON(!func->old_addr)) | |
334 | return -EINVAL; | |
335 | ||
3c33f5b9 JP |
336 | ops = klp_find_ops(func->old_addr); |
337 | if (WARN_ON(!ops)) | |
338 | return -EINVAL; | |
b700e7f0 | 339 | |
3c33f5b9 JP |
340 | if (list_is_singular(&ops->func_stack)) { |
341 | ret = unregister_ftrace_function(&ops->fops); | |
342 | if (ret) { | |
343 | pr_err("failed to unregister ftrace handler for function '%s' (%d)\n", | |
344 | func->old_name, ret); | |
345 | return ret; | |
346 | } | |
347 | ||
348 | ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); | |
349 | if (ret) | |
350 | pr_warn("function unregister succeeded but failed to clear the filter\n"); | |
351 | ||
352 | list_del_rcu(&func->stack_node); | |
353 | list_del(&ops->node); | |
354 | kfree(ops); | |
355 | } else { | |
356 | list_del_rcu(&func->stack_node); | |
357 | } | |
b700e7f0 SJ |
358 | |
359 | func->state = KLP_DISABLED; | |
360 | ||
361 | return 0; | |
362 | } | |
363 | ||
364 | static int klp_enable_func(struct klp_func *func) | |
365 | { | |
3c33f5b9 | 366 | struct klp_ops *ops; |
b700e7f0 SJ |
367 | int ret; |
368 | ||
369 | if (WARN_ON(!func->old_addr)) | |
370 | return -EINVAL; | |
371 | ||
372 | if (WARN_ON(func->state != KLP_DISABLED)) | |
373 | return -EINVAL; | |
374 | ||
3c33f5b9 JP |
375 | ops = klp_find_ops(func->old_addr); |
376 | if (!ops) { | |
377 | ops = kzalloc(sizeof(*ops), GFP_KERNEL); | |
378 | if (!ops) | |
379 | return -ENOMEM; | |
380 | ||
381 | ops->fops.func = klp_ftrace_handler; | |
382 | ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS | | |
383 | FTRACE_OPS_FL_DYNAMIC | | |
384 | FTRACE_OPS_FL_IPMODIFY; | |
385 | ||
386 | list_add(&ops->node, &klp_ops); | |
387 | ||
388 | INIT_LIST_HEAD(&ops->func_stack); | |
389 | list_add_rcu(&func->stack_node, &ops->func_stack); | |
390 | ||
391 | ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0); | |
392 | if (ret) { | |
393 | pr_err("failed to set ftrace filter for function '%s' (%d)\n", | |
394 | func->old_name, ret); | |
395 | goto err; | |
396 | } | |
397 | ||
398 | ret = register_ftrace_function(&ops->fops); | |
399 | if (ret) { | |
400 | pr_err("failed to register ftrace handler for function '%s' (%d)\n", | |
401 | func->old_name, ret); | |
402 | ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); | |
403 | goto err; | |
404 | } | |
405 | ||
b700e7f0 | 406 | |
b700e7f0 | 407 | } else { |
3c33f5b9 | 408 | list_add_rcu(&func->stack_node, &ops->func_stack); |
b700e7f0 SJ |
409 | } |
410 | ||
3c33f5b9 JP |
411 | func->state = KLP_ENABLED; |
412 | ||
dbed7dda | 413 | return 0; |
3c33f5b9 JP |
414 | |
415 | err: | |
416 | list_del_rcu(&func->stack_node); | |
417 | list_del(&ops->node); | |
418 | kfree(ops); | |
b700e7f0 SJ |
419 | return ret; |
420 | } | |
421 | ||
422 | static int klp_disable_object(struct klp_object *obj) | |
423 | { | |
424 | struct klp_func *func; | |
425 | int ret; | |
426 | ||
427 | for (func = obj->funcs; func->old_name; func++) { | |
428 | if (func->state != KLP_ENABLED) | |
429 | continue; | |
430 | ||
431 | ret = klp_disable_func(func); | |
432 | if (ret) | |
433 | return ret; | |
434 | } | |
435 | ||
436 | obj->state = KLP_DISABLED; | |
437 | ||
438 | return 0; | |
439 | } | |
440 | ||
441 | static int klp_enable_object(struct klp_object *obj) | |
442 | { | |
443 | struct klp_func *func; | |
444 | int ret; | |
445 | ||
446 | if (WARN_ON(obj->state != KLP_DISABLED)) | |
447 | return -EINVAL; | |
448 | ||
449 | if (WARN_ON(!klp_is_object_loaded(obj))) | |
450 | return -EINVAL; | |
451 | ||
452 | for (func = obj->funcs; func->old_name; func++) { | |
453 | ret = klp_enable_func(func); | |
454 | if (ret) | |
455 | goto unregister; | |
456 | } | |
457 | obj->state = KLP_ENABLED; | |
458 | ||
459 | return 0; | |
460 | ||
461 | unregister: | |
462 | WARN_ON(klp_disable_object(obj)); | |
463 | return ret; | |
464 | } | |
465 | ||
466 | static int __klp_disable_patch(struct klp_patch *patch) | |
467 | { | |
468 | struct klp_object *obj; | |
469 | int ret; | |
470 | ||
83a90bb1 JP |
471 | /* enforce stacking: only the last enabled patch can be disabled */ |
472 | if (!list_is_last(&patch->list, &klp_patches) && | |
473 | list_next_entry(patch, list)->state == KLP_ENABLED) | |
474 | return -EBUSY; | |
475 | ||
b700e7f0 SJ |
476 | pr_notice("disabling patch '%s'\n", patch->mod->name); |
477 | ||
478 | for (obj = patch->objs; obj->funcs; obj++) { | |
479 | if (obj->state != KLP_ENABLED) | |
480 | continue; | |
481 | ||
482 | ret = klp_disable_object(obj); | |
483 | if (ret) | |
484 | return ret; | |
485 | } | |
486 | ||
487 | patch->state = KLP_DISABLED; | |
488 | ||
489 | return 0; | |
490 | } | |
491 | ||
492 | /** | |
493 | * klp_disable_patch() - disables a registered patch | |
494 | * @patch: The registered, enabled patch to be disabled | |
495 | * | |
496 | * Unregisters the patched functions from ftrace. | |
497 | * | |
498 | * Return: 0 on success, otherwise error | |
499 | */ | |
500 | int klp_disable_patch(struct klp_patch *patch) | |
501 | { | |
502 | int ret; | |
503 | ||
504 | mutex_lock(&klp_mutex); | |
505 | ||
506 | if (!klp_is_patch_registered(patch)) { | |
507 | ret = -EINVAL; | |
508 | goto err; | |
509 | } | |
510 | ||
511 | if (patch->state == KLP_DISABLED) { | |
512 | ret = -EINVAL; | |
513 | goto err; | |
514 | } | |
515 | ||
516 | ret = __klp_disable_patch(patch); | |
517 | ||
518 | err: | |
519 | mutex_unlock(&klp_mutex); | |
520 | return ret; | |
521 | } | |
522 | EXPORT_SYMBOL_GPL(klp_disable_patch); | |
523 | ||
524 | static int __klp_enable_patch(struct klp_patch *patch) | |
525 | { | |
526 | struct klp_object *obj; | |
527 | int ret; | |
528 | ||
529 | if (WARN_ON(patch->state != KLP_DISABLED)) | |
530 | return -EINVAL; | |
531 | ||
83a90bb1 JP |
532 | /* enforce stacking: only the first disabled patch can be enabled */ |
533 | if (patch->list.prev != &klp_patches && | |
534 | list_prev_entry(patch, list)->state == KLP_DISABLED) | |
535 | return -EBUSY; | |
536 | ||
b700e7f0 SJ |
537 | pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n"); |
538 | add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK); | |
539 | ||
540 | pr_notice("enabling patch '%s'\n", patch->mod->name); | |
541 | ||
542 | for (obj = patch->objs; obj->funcs; obj++) { | |
543 | klp_find_object_module(obj); | |
544 | ||
545 | if (!klp_is_object_loaded(obj)) | |
546 | continue; | |
547 | ||
548 | ret = klp_enable_object(obj); | |
549 | if (ret) | |
550 | goto unregister; | |
551 | } | |
552 | ||
553 | patch->state = KLP_ENABLED; | |
554 | ||
555 | return 0; | |
556 | ||
557 | unregister: | |
558 | WARN_ON(__klp_disable_patch(patch)); | |
559 | return ret; | |
560 | } | |
561 | ||
562 | /** | |
563 | * klp_enable_patch() - enables a registered patch | |
564 | * @patch: The registered, disabled patch to be enabled | |
565 | * | |
566 | * Performs the needed symbol lookups and code relocations, | |
567 | * then registers the patched functions with ftrace. | |
568 | * | |
569 | * Return: 0 on success, otherwise error | |
570 | */ | |
571 | int klp_enable_patch(struct klp_patch *patch) | |
572 | { | |
573 | int ret; | |
574 | ||
575 | mutex_lock(&klp_mutex); | |
576 | ||
577 | if (!klp_is_patch_registered(patch)) { | |
578 | ret = -EINVAL; | |
579 | goto err; | |
580 | } | |
581 | ||
582 | ret = __klp_enable_patch(patch); | |
583 | ||
584 | err: | |
585 | mutex_unlock(&klp_mutex); | |
586 | return ret; | |
587 | } | |
588 | EXPORT_SYMBOL_GPL(klp_enable_patch); | |
589 | ||
590 | /* | |
591 | * Sysfs Interface | |
592 | * | |
593 | * /sys/kernel/livepatch | |
594 | * /sys/kernel/livepatch/<patch> | |
595 | * /sys/kernel/livepatch/<patch>/enabled | |
596 | * /sys/kernel/livepatch/<patch>/<object> | |
597 | * /sys/kernel/livepatch/<patch>/<object>/<func> | |
598 | */ | |
599 | ||
600 | static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, | |
601 | const char *buf, size_t count) | |
602 | { | |
603 | struct klp_patch *patch; | |
604 | int ret; | |
605 | unsigned long val; | |
606 | ||
607 | ret = kstrtoul(buf, 10, &val); | |
608 | if (ret) | |
609 | return -EINVAL; | |
610 | ||
611 | if (val != KLP_DISABLED && val != KLP_ENABLED) | |
612 | return -EINVAL; | |
613 | ||
614 | patch = container_of(kobj, struct klp_patch, kobj); | |
615 | ||
616 | mutex_lock(&klp_mutex); | |
617 | ||
618 | if (val == patch->state) { | |
619 | /* already in requested state */ | |
620 | ret = -EINVAL; | |
621 | goto err; | |
622 | } | |
623 | ||
624 | if (val == KLP_ENABLED) { | |
625 | ret = __klp_enable_patch(patch); | |
626 | if (ret) | |
627 | goto err; | |
628 | } else { | |
629 | ret = __klp_disable_patch(patch); | |
630 | if (ret) | |
631 | goto err; | |
632 | } | |
633 | ||
634 | mutex_unlock(&klp_mutex); | |
635 | ||
636 | return count; | |
637 | ||
638 | err: | |
639 | mutex_unlock(&klp_mutex); | |
640 | return ret; | |
641 | } | |
642 | ||
643 | static ssize_t enabled_show(struct kobject *kobj, | |
644 | struct kobj_attribute *attr, char *buf) | |
645 | { | |
646 | struct klp_patch *patch; | |
647 | ||
648 | patch = container_of(kobj, struct klp_patch, kobj); | |
649 | return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state); | |
650 | } | |
651 | ||
652 | static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled); | |
653 | static struct attribute *klp_patch_attrs[] = { | |
654 | &enabled_kobj_attr.attr, | |
655 | NULL | |
656 | }; | |
657 | ||
658 | static void klp_kobj_release_patch(struct kobject *kobj) | |
659 | { | |
660 | /* | |
661 | * Once we have a consistency model we'll need to module_put() the | |
662 | * patch module here. See klp_register_patch() for more details. | |
663 | */ | |
664 | } | |
665 | ||
666 | static struct kobj_type klp_ktype_patch = { | |
667 | .release = klp_kobj_release_patch, | |
668 | .sysfs_ops = &kobj_sysfs_ops, | |
669 | .default_attrs = klp_patch_attrs, | |
670 | }; | |
671 | ||
672 | static void klp_kobj_release_func(struct kobject *kobj) | |
673 | { | |
b700e7f0 SJ |
674 | } |
675 | ||
676 | static struct kobj_type klp_ktype_func = { | |
677 | .release = klp_kobj_release_func, | |
678 | .sysfs_ops = &kobj_sysfs_ops, | |
679 | }; | |
680 | ||
681 | /* | |
682 | * Free all functions' kobjects in the array up to some limit. When limit is | |
683 | * NULL, all kobjects are freed. | |
684 | */ | |
685 | static void klp_free_funcs_limited(struct klp_object *obj, | |
686 | struct klp_func *limit) | |
687 | { | |
688 | struct klp_func *func; | |
689 | ||
690 | for (func = obj->funcs; func->old_name && func != limit; func++) | |
691 | kobject_put(&func->kobj); | |
692 | } | |
693 | ||
694 | /* Clean up when a patched object is unloaded */ | |
695 | static void klp_free_object_loaded(struct klp_object *obj) | |
696 | { | |
697 | struct klp_func *func; | |
698 | ||
699 | obj->mod = NULL; | |
700 | ||
701 | for (func = obj->funcs; func->old_name; func++) | |
702 | func->old_addr = 0; | |
703 | } | |
704 | ||
705 | /* | |
706 | * Free all objects' kobjects in the array up to some limit. When limit is | |
707 | * NULL, all kobjects are freed. | |
708 | */ | |
709 | static void klp_free_objects_limited(struct klp_patch *patch, | |
710 | struct klp_object *limit) | |
711 | { | |
712 | struct klp_object *obj; | |
713 | ||
714 | for (obj = patch->objs; obj->funcs && obj != limit; obj++) { | |
715 | klp_free_funcs_limited(obj, NULL); | |
716 | kobject_put(obj->kobj); | |
717 | } | |
718 | } | |
719 | ||
720 | static void klp_free_patch(struct klp_patch *patch) | |
721 | { | |
722 | klp_free_objects_limited(patch, NULL); | |
723 | if (!list_empty(&patch->list)) | |
724 | list_del(&patch->list); | |
725 | kobject_put(&patch->kobj); | |
726 | } | |
727 | ||
728 | static int klp_init_func(struct klp_object *obj, struct klp_func *func) | |
729 | { | |
3c33f5b9 | 730 | INIT_LIST_HEAD(&func->stack_node); |
b700e7f0 SJ |
731 | func->state = KLP_DISABLED; |
732 | ||
3c33f5b9 | 733 | return kobject_init_and_add(&func->kobj, &klp_ktype_func, |
e0b561ee | 734 | obj->kobj, "%s", func->old_name); |
b700e7f0 SJ |
735 | } |
736 | ||
737 | /* parts of the initialization that is done only when the object is loaded */ | |
738 | static int klp_init_object_loaded(struct klp_patch *patch, | |
739 | struct klp_object *obj) | |
740 | { | |
741 | struct klp_func *func; | |
742 | int ret; | |
743 | ||
744 | if (obj->relocs) { | |
745 | ret = klp_write_object_relocations(patch->mod, obj); | |
746 | if (ret) | |
747 | return ret; | |
748 | } | |
749 | ||
750 | for (func = obj->funcs; func->old_name; func++) { | |
751 | ret = klp_find_verify_func_addr(obj, func); | |
752 | if (ret) | |
753 | return ret; | |
754 | } | |
755 | ||
756 | return 0; | |
757 | } | |
758 | ||
759 | static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) | |
760 | { | |
761 | struct klp_func *func; | |
762 | int ret; | |
763 | const char *name; | |
764 | ||
765 | if (!obj->funcs) | |
766 | return -EINVAL; | |
767 | ||
768 | obj->state = KLP_DISABLED; | |
769 | ||
770 | klp_find_object_module(obj); | |
771 | ||
772 | name = klp_is_module(obj) ? obj->name : "vmlinux"; | |
773 | obj->kobj = kobject_create_and_add(name, &patch->kobj); | |
774 | if (!obj->kobj) | |
775 | return -ENOMEM; | |
776 | ||
777 | for (func = obj->funcs; func->old_name; func++) { | |
778 | ret = klp_init_func(obj, func); | |
779 | if (ret) | |
780 | goto free; | |
781 | } | |
782 | ||
783 | if (klp_is_object_loaded(obj)) { | |
784 | ret = klp_init_object_loaded(patch, obj); | |
785 | if (ret) | |
786 | goto free; | |
787 | } | |
788 | ||
789 | return 0; | |
790 | ||
791 | free: | |
792 | klp_free_funcs_limited(obj, func); | |
793 | kobject_put(obj->kobj); | |
794 | return ret; | |
795 | } | |
796 | ||
797 | static int klp_init_patch(struct klp_patch *patch) | |
798 | { | |
799 | struct klp_object *obj; | |
800 | int ret; | |
801 | ||
802 | if (!patch->objs) | |
803 | return -EINVAL; | |
804 | ||
805 | mutex_lock(&klp_mutex); | |
806 | ||
807 | patch->state = KLP_DISABLED; | |
808 | ||
809 | ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch, | |
e0b561ee | 810 | klp_root_kobj, "%s", patch->mod->name); |
b700e7f0 SJ |
811 | if (ret) |
812 | goto unlock; | |
813 | ||
814 | for (obj = patch->objs; obj->funcs; obj++) { | |
815 | ret = klp_init_object(patch, obj); | |
816 | if (ret) | |
817 | goto free; | |
818 | } | |
819 | ||
99590ba5 | 820 | list_add_tail(&patch->list, &klp_patches); |
b700e7f0 SJ |
821 | |
822 | mutex_unlock(&klp_mutex); | |
823 | ||
824 | return 0; | |
825 | ||
826 | free: | |
827 | klp_free_objects_limited(patch, obj); | |
828 | kobject_put(&patch->kobj); | |
829 | unlock: | |
830 | mutex_unlock(&klp_mutex); | |
831 | return ret; | |
832 | } | |
833 | ||
834 | /** | |
835 | * klp_unregister_patch() - unregisters a patch | |
836 | * @patch: Disabled patch to be unregistered | |
837 | * | |
838 | * Frees the data structures and removes the sysfs interface. | |
839 | * | |
840 | * Return: 0 on success, otherwise error | |
841 | */ | |
842 | int klp_unregister_patch(struct klp_patch *patch) | |
843 | { | |
844 | int ret = 0; | |
845 | ||
846 | mutex_lock(&klp_mutex); | |
847 | ||
848 | if (!klp_is_patch_registered(patch)) { | |
849 | ret = -EINVAL; | |
850 | goto out; | |
851 | } | |
852 | ||
853 | if (patch->state == KLP_ENABLED) { | |
854 | ret = -EBUSY; | |
855 | goto out; | |
856 | } | |
857 | ||
858 | klp_free_patch(patch); | |
859 | ||
860 | out: | |
861 | mutex_unlock(&klp_mutex); | |
862 | return ret; | |
863 | } | |
864 | EXPORT_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 | * Return: 0 on success, otherwise error | |
874 | */ | |
875 | int klp_register_patch(struct klp_patch *patch) | |
876 | { | |
877 | int ret; | |
878 | ||
879 | if (!klp_initialized()) | |
880 | return -ENODEV; | |
881 | ||
882 | if (!patch || !patch->mod) | |
883 | return -EINVAL; | |
884 | ||
885 | /* | |
886 | * A reference is taken on the patch module to prevent it from being | |
887 | * unloaded. Right now, we don't allow patch modules to unload since | |
888 | * there is currently no method to determine if a thread is still | |
889 | * running in the patched code contained in the patch module once | |
890 | * the ftrace registration is successful. | |
891 | */ | |
892 | if (!try_module_get(patch->mod)) | |
893 | return -ENODEV; | |
894 | ||
895 | ret = klp_init_patch(patch); | |
896 | if (ret) | |
897 | module_put(patch->mod); | |
898 | ||
899 | return ret; | |
900 | } | |
901 | EXPORT_SYMBOL_GPL(klp_register_patch); | |
902 | ||
903 | static void klp_module_notify_coming(struct klp_patch *patch, | |
904 | struct klp_object *obj) | |
905 | { | |
906 | struct module *pmod = patch->mod; | |
907 | struct module *mod = obj->mod; | |
908 | int ret; | |
909 | ||
910 | ret = klp_init_object_loaded(patch, obj); | |
911 | if (ret) | |
912 | goto err; | |
913 | ||
914 | if (patch->state == KLP_DISABLED) | |
915 | return; | |
916 | ||
917 | pr_notice("applying patch '%s' to loading module '%s'\n", | |
918 | pmod->name, mod->name); | |
919 | ||
920 | ret = klp_enable_object(obj); | |
921 | if (!ret) | |
922 | return; | |
923 | ||
924 | err: | |
925 | pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", | |
926 | pmod->name, mod->name, ret); | |
927 | } | |
928 | ||
929 | static void klp_module_notify_going(struct klp_patch *patch, | |
930 | struct klp_object *obj) | |
931 | { | |
932 | struct module *pmod = patch->mod; | |
933 | struct module *mod = obj->mod; | |
934 | int ret; | |
935 | ||
936 | if (patch->state == KLP_DISABLED) | |
937 | goto disabled; | |
938 | ||
939 | pr_notice("reverting patch '%s' on unloading module '%s'\n", | |
940 | pmod->name, mod->name); | |
941 | ||
942 | ret = klp_disable_object(obj); | |
943 | if (ret) | |
944 | pr_warn("failed to revert patch '%s' on module '%s' (%d)\n", | |
945 | pmod->name, mod->name, ret); | |
946 | ||
947 | disabled: | |
948 | klp_free_object_loaded(obj); | |
949 | } | |
950 | ||
951 | static int klp_module_notify(struct notifier_block *nb, unsigned long action, | |
952 | void *data) | |
953 | { | |
954 | struct module *mod = data; | |
955 | struct klp_patch *patch; | |
956 | struct klp_object *obj; | |
957 | ||
958 | if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING) | |
959 | return 0; | |
960 | ||
961 | mutex_lock(&klp_mutex); | |
962 | ||
963 | list_for_each_entry(patch, &klp_patches, list) { | |
964 | for (obj = patch->objs; obj->funcs; obj++) { | |
965 | if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) | |
966 | continue; | |
967 | ||
968 | if (action == MODULE_STATE_COMING) { | |
969 | obj->mod = mod; | |
970 | klp_module_notify_coming(patch, obj); | |
971 | } else /* MODULE_STATE_GOING */ | |
972 | klp_module_notify_going(patch, obj); | |
973 | ||
974 | break; | |
975 | } | |
976 | } | |
977 | ||
978 | mutex_unlock(&klp_mutex); | |
979 | ||
980 | return 0; | |
981 | } | |
982 | ||
983 | static struct notifier_block klp_module_nb = { | |
984 | .notifier_call = klp_module_notify, | |
985 | .priority = INT_MIN+1, /* called late but before ftrace notifier */ | |
986 | }; | |
987 | ||
988 | static int klp_init(void) | |
989 | { | |
990 | int ret; | |
991 | ||
b9dfe0be JK |
992 | ret = klp_check_compiler_support(); |
993 | if (ret) { | |
994 | pr_info("Your compiler is too old; turning off.\n"); | |
995 | return -EINVAL; | |
996 | } | |
997 | ||
b700e7f0 SJ |
998 | ret = register_module_notifier(&klp_module_nb); |
999 | if (ret) | |
1000 | return ret; | |
1001 | ||
1002 | klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); | |
1003 | if (!klp_root_kobj) { | |
1004 | ret = -ENOMEM; | |
1005 | goto unregister; | |
1006 | } | |
1007 | ||
1008 | return 0; | |
1009 | ||
1010 | unregister: | |
1011 | unregister_module_notifier(&klp_module_nb); | |
1012 | return ret; | |
1013 | } | |
1014 | ||
1015 | module_init(klp_init); |