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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 | { | |
8cb2c2dc PM |
92 | struct module *mod; |
93 | ||
b700e7f0 SJ |
94 | if (!klp_is_module(obj)) |
95 | return; | |
96 | ||
97 | mutex_lock(&module_mutex); | |
98 | /* | |
8cb2c2dc PM |
99 | * We do not want to block removal of patched modules and therefore |
100 | * we do not take a reference here. The patches are removed by | |
101 | * a going module handler instead. | |
102 | */ | |
103 | mod = find_module(obj->name); | |
104 | /* | |
105 | * Do not mess work of the module coming and going notifiers. | |
106 | * Note that the patch might still be needed before the going handler | |
107 | * is called. Module functions can be called even in the GOING state | |
108 | * until mod->exit() finishes. This is especially important for | |
109 | * patches that modify semantic of the functions. | |
b700e7f0 | 110 | */ |
8cb2c2dc PM |
111 | if (mod && mod->klp_alive) |
112 | obj->mod = mod; | |
113 | ||
b700e7f0 SJ |
114 | mutex_unlock(&module_mutex); |
115 | } | |
116 | ||
117 | /* klp_mutex must be held by caller */ | |
118 | static bool klp_is_patch_registered(struct klp_patch *patch) | |
119 | { | |
120 | struct klp_patch *mypatch; | |
121 | ||
122 | list_for_each_entry(mypatch, &klp_patches, list) | |
123 | if (mypatch == patch) | |
124 | return true; | |
125 | ||
126 | return false; | |
127 | } | |
128 | ||
129 | static bool klp_initialized(void) | |
130 | { | |
131 | return klp_root_kobj; | |
132 | } | |
133 | ||
134 | struct klp_find_arg { | |
135 | const char *objname; | |
136 | const char *name; | |
137 | unsigned long addr; | |
138 | /* | |
139 | * If count == 0, the symbol was not found. If count == 1, a unique | |
140 | * match was found and addr is set. If count > 1, there is | |
141 | * unresolvable ambiguity among "count" number of symbols with the same | |
142 | * name in the same object. | |
143 | */ | |
144 | unsigned long count; | |
145 | }; | |
146 | ||
147 | static int klp_find_callback(void *data, const char *name, | |
148 | struct module *mod, unsigned long addr) | |
149 | { | |
150 | struct klp_find_arg *args = data; | |
151 | ||
152 | if ((mod && !args->objname) || (!mod && args->objname)) | |
153 | return 0; | |
154 | ||
155 | if (strcmp(args->name, name)) | |
156 | return 0; | |
157 | ||
158 | if (args->objname && strcmp(args->objname, mod->name)) | |
159 | return 0; | |
160 | ||
161 | /* | |
162 | * args->addr might be overwritten if another match is found | |
163 | * but klp_find_object_symbol() handles this and only returns the | |
164 | * addr if count == 1. | |
165 | */ | |
166 | args->addr = addr; | |
167 | args->count++; | |
168 | ||
169 | return 0; | |
170 | } | |
171 | ||
172 | static int klp_find_object_symbol(const char *objname, const char *name, | |
173 | unsigned long *addr) | |
174 | { | |
175 | struct klp_find_arg args = { | |
176 | .objname = objname, | |
177 | .name = name, | |
178 | .addr = 0, | |
179 | .count = 0 | |
180 | }; | |
181 | ||
182 | kallsyms_on_each_symbol(klp_find_callback, &args); | |
183 | ||
184 | if (args.count == 0) | |
185 | pr_err("symbol '%s' not found in symbol table\n", name); | |
186 | else if (args.count > 1) | |
187 | pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n", | |
188 | args.count, name, objname); | |
189 | else { | |
190 | *addr = args.addr; | |
191 | return 0; | |
192 | } | |
193 | ||
194 | *addr = 0; | |
195 | return -EINVAL; | |
196 | } | |
197 | ||
198 | struct klp_verify_args { | |
199 | const char *name; | |
200 | const unsigned long addr; | |
201 | }; | |
202 | ||
203 | static int klp_verify_callback(void *data, const char *name, | |
204 | struct module *mod, unsigned long addr) | |
205 | { | |
206 | struct klp_verify_args *args = data; | |
207 | ||
208 | if (!mod && | |
209 | !strcmp(args->name, name) && | |
210 | args->addr == addr) | |
211 | return 1; | |
212 | ||
213 | return 0; | |
214 | } | |
215 | ||
216 | static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr) | |
217 | { | |
218 | struct klp_verify_args args = { | |
219 | .name = name, | |
220 | .addr = addr, | |
221 | }; | |
222 | ||
223 | if (kallsyms_on_each_symbol(klp_verify_callback, &args)) | |
224 | return 0; | |
225 | ||
f638f4dc | 226 | pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n", |
b700e7f0 SJ |
227 | name, addr); |
228 | return -EINVAL; | |
229 | } | |
230 | ||
231 | static int klp_find_verify_func_addr(struct klp_object *obj, | |
232 | struct klp_func *func) | |
233 | { | |
234 | int ret; | |
235 | ||
236 | #if defined(CONFIG_RANDOMIZE_BASE) | |
237 | /* KASLR is enabled, disregard old_addr from user */ | |
238 | func->old_addr = 0; | |
239 | #endif | |
240 | ||
241 | if (!func->old_addr || klp_is_module(obj)) | |
242 | ret = klp_find_object_symbol(obj->name, func->old_name, | |
243 | &func->old_addr); | |
244 | else | |
245 | ret = klp_verify_vmlinux_symbol(func->old_name, | |
246 | func->old_addr); | |
247 | ||
248 | return ret; | |
249 | } | |
250 | ||
251 | /* | |
252 | * external symbols are located outside the parent object (where the parent | |
253 | * object is either vmlinux or the kmod being patched). | |
254 | */ | |
255 | static int klp_find_external_symbol(struct module *pmod, const char *name, | |
256 | unsigned long *addr) | |
257 | { | |
258 | const struct kernel_symbol *sym; | |
259 | ||
260 | /* first, check if it's an exported symbol */ | |
261 | preempt_disable(); | |
262 | sym = find_symbol(name, NULL, NULL, true, true); | |
b700e7f0 SJ |
263 | if (sym) { |
264 | *addr = sym->value; | |
c064a0de | 265 | preempt_enable(); |
b700e7f0 SJ |
266 | return 0; |
267 | } | |
c064a0de | 268 | preempt_enable(); |
b700e7f0 SJ |
269 | |
270 | /* otherwise check if it's in another .o within the patch module */ | |
271 | return klp_find_object_symbol(pmod->name, name, addr); | |
272 | } | |
273 | ||
274 | static int klp_write_object_relocations(struct module *pmod, | |
275 | struct klp_object *obj) | |
276 | { | |
277 | int ret; | |
278 | struct klp_reloc *reloc; | |
279 | ||
280 | if (WARN_ON(!klp_is_object_loaded(obj))) | |
281 | return -EINVAL; | |
282 | ||
283 | if (WARN_ON(!obj->relocs)) | |
284 | return -EINVAL; | |
285 | ||
286 | for (reloc = obj->relocs; reloc->name; reloc++) { | |
287 | if (!klp_is_module(obj)) { | |
288 | ret = klp_verify_vmlinux_symbol(reloc->name, | |
289 | reloc->val); | |
290 | if (ret) | |
291 | return ret; | |
292 | } else { | |
293 | /* module, reloc->val needs to be discovered */ | |
294 | if (reloc->external) | |
295 | ret = klp_find_external_symbol(pmod, | |
296 | reloc->name, | |
297 | &reloc->val); | |
298 | else | |
299 | ret = klp_find_object_symbol(obj->mod->name, | |
300 | reloc->name, | |
301 | &reloc->val); | |
302 | if (ret) | |
303 | return ret; | |
304 | } | |
305 | ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc, | |
306 | reloc->val + reloc->addend); | |
307 | if (ret) { | |
308 | pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n", | |
309 | reloc->name, reloc->val, ret); | |
310 | return ret; | |
311 | } | |
312 | } | |
313 | ||
314 | return 0; | |
315 | } | |
316 | ||
317 | static void notrace klp_ftrace_handler(unsigned long ip, | |
318 | unsigned long parent_ip, | |
3c33f5b9 | 319 | struct ftrace_ops *fops, |
b700e7f0 SJ |
320 | struct pt_regs *regs) |
321 | { | |
3c33f5b9 JP |
322 | struct klp_ops *ops; |
323 | struct klp_func *func; | |
324 | ||
325 | ops = container_of(fops, struct klp_ops, fops); | |
326 | ||
327 | rcu_read_lock(); | |
328 | func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, | |
329 | stack_node); | |
3c33f5b9 | 330 | if (WARN_ON_ONCE(!func)) |
c4ce0da8 | 331 | goto unlock; |
b700e7f0 | 332 | |
b5bfc517 | 333 | klp_arch_set_pc(regs, (unsigned long)func->new_func); |
c4ce0da8 PM |
334 | unlock: |
335 | rcu_read_unlock(); | |
b700e7f0 SJ |
336 | } |
337 | ||
338 | static int klp_disable_func(struct klp_func *func) | |
339 | { | |
3c33f5b9 | 340 | struct klp_ops *ops; |
b700e7f0 SJ |
341 | int ret; |
342 | ||
343 | if (WARN_ON(func->state != KLP_ENABLED)) | |
344 | return -EINVAL; | |
345 | ||
346 | if (WARN_ON(!func->old_addr)) | |
347 | return -EINVAL; | |
348 | ||
3c33f5b9 JP |
349 | ops = klp_find_ops(func->old_addr); |
350 | if (WARN_ON(!ops)) | |
351 | return -EINVAL; | |
b700e7f0 | 352 | |
3c33f5b9 JP |
353 | if (list_is_singular(&ops->func_stack)) { |
354 | ret = unregister_ftrace_function(&ops->fops); | |
355 | if (ret) { | |
356 | pr_err("failed to unregister ftrace handler for function '%s' (%d)\n", | |
357 | func->old_name, ret); | |
358 | return ret; | |
359 | } | |
360 | ||
361 | ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); | |
362 | if (ret) | |
363 | pr_warn("function unregister succeeded but failed to clear the filter\n"); | |
364 | ||
365 | list_del_rcu(&func->stack_node); | |
366 | list_del(&ops->node); | |
367 | kfree(ops); | |
368 | } else { | |
369 | list_del_rcu(&func->stack_node); | |
370 | } | |
b700e7f0 SJ |
371 | |
372 | func->state = KLP_DISABLED; | |
373 | ||
374 | return 0; | |
375 | } | |
376 | ||
377 | static int klp_enable_func(struct klp_func *func) | |
378 | { | |
3c33f5b9 | 379 | struct klp_ops *ops; |
b700e7f0 SJ |
380 | int ret; |
381 | ||
382 | if (WARN_ON(!func->old_addr)) | |
383 | return -EINVAL; | |
384 | ||
385 | if (WARN_ON(func->state != KLP_DISABLED)) | |
386 | return -EINVAL; | |
387 | ||
3c33f5b9 JP |
388 | ops = klp_find_ops(func->old_addr); |
389 | if (!ops) { | |
390 | ops = kzalloc(sizeof(*ops), GFP_KERNEL); | |
391 | if (!ops) | |
392 | return -ENOMEM; | |
393 | ||
394 | ops->fops.func = klp_ftrace_handler; | |
395 | ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS | | |
396 | FTRACE_OPS_FL_DYNAMIC | | |
397 | FTRACE_OPS_FL_IPMODIFY; | |
398 | ||
399 | list_add(&ops->node, &klp_ops); | |
400 | ||
401 | INIT_LIST_HEAD(&ops->func_stack); | |
402 | list_add_rcu(&func->stack_node, &ops->func_stack); | |
403 | ||
404 | ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0); | |
405 | if (ret) { | |
406 | pr_err("failed to set ftrace filter for function '%s' (%d)\n", | |
407 | func->old_name, ret); | |
408 | goto err; | |
409 | } | |
410 | ||
411 | ret = register_ftrace_function(&ops->fops); | |
412 | if (ret) { | |
413 | pr_err("failed to register ftrace handler for function '%s' (%d)\n", | |
414 | func->old_name, ret); | |
415 | ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); | |
416 | goto err; | |
417 | } | |
418 | ||
b700e7f0 | 419 | |
b700e7f0 | 420 | } else { |
3c33f5b9 | 421 | list_add_rcu(&func->stack_node, &ops->func_stack); |
b700e7f0 SJ |
422 | } |
423 | ||
3c33f5b9 JP |
424 | func->state = KLP_ENABLED; |
425 | ||
dbed7dda | 426 | return 0; |
3c33f5b9 JP |
427 | |
428 | err: | |
429 | list_del_rcu(&func->stack_node); | |
430 | list_del(&ops->node); | |
431 | kfree(ops); | |
b700e7f0 SJ |
432 | return ret; |
433 | } | |
434 | ||
435 | static int klp_disable_object(struct klp_object *obj) | |
436 | { | |
437 | struct klp_func *func; | |
438 | int ret; | |
439 | ||
440 | for (func = obj->funcs; func->old_name; func++) { | |
441 | if (func->state != KLP_ENABLED) | |
442 | continue; | |
443 | ||
444 | ret = klp_disable_func(func); | |
445 | if (ret) | |
446 | return ret; | |
447 | } | |
448 | ||
449 | obj->state = KLP_DISABLED; | |
450 | ||
451 | return 0; | |
452 | } | |
453 | ||
454 | static int klp_enable_object(struct klp_object *obj) | |
455 | { | |
456 | struct klp_func *func; | |
457 | int ret; | |
458 | ||
459 | if (WARN_ON(obj->state != KLP_DISABLED)) | |
460 | return -EINVAL; | |
461 | ||
462 | if (WARN_ON(!klp_is_object_loaded(obj))) | |
463 | return -EINVAL; | |
464 | ||
465 | for (func = obj->funcs; func->old_name; func++) { | |
466 | ret = klp_enable_func(func); | |
467 | if (ret) | |
468 | goto unregister; | |
469 | } | |
470 | obj->state = KLP_ENABLED; | |
471 | ||
472 | return 0; | |
473 | ||
474 | unregister: | |
475 | WARN_ON(klp_disable_object(obj)); | |
476 | return ret; | |
477 | } | |
478 | ||
479 | static int __klp_disable_patch(struct klp_patch *patch) | |
480 | { | |
481 | struct klp_object *obj; | |
482 | int ret; | |
483 | ||
83a90bb1 JP |
484 | /* enforce stacking: only the last enabled patch can be disabled */ |
485 | if (!list_is_last(&patch->list, &klp_patches) && | |
486 | list_next_entry(patch, list)->state == KLP_ENABLED) | |
487 | return -EBUSY; | |
488 | ||
b700e7f0 SJ |
489 | pr_notice("disabling patch '%s'\n", patch->mod->name); |
490 | ||
491 | for (obj = patch->objs; obj->funcs; obj++) { | |
492 | if (obj->state != KLP_ENABLED) | |
493 | continue; | |
494 | ||
495 | ret = klp_disable_object(obj); | |
496 | if (ret) | |
497 | return ret; | |
498 | } | |
499 | ||
500 | patch->state = KLP_DISABLED; | |
501 | ||
502 | return 0; | |
503 | } | |
504 | ||
505 | /** | |
506 | * klp_disable_patch() - disables a registered patch | |
507 | * @patch: The registered, enabled patch to be disabled | |
508 | * | |
509 | * Unregisters the patched functions from ftrace. | |
510 | * | |
511 | * Return: 0 on success, otherwise error | |
512 | */ | |
513 | int klp_disable_patch(struct klp_patch *patch) | |
514 | { | |
515 | int ret; | |
516 | ||
517 | mutex_lock(&klp_mutex); | |
518 | ||
519 | if (!klp_is_patch_registered(patch)) { | |
520 | ret = -EINVAL; | |
521 | goto err; | |
522 | } | |
523 | ||
524 | if (patch->state == KLP_DISABLED) { | |
525 | ret = -EINVAL; | |
526 | goto err; | |
527 | } | |
528 | ||
529 | ret = __klp_disable_patch(patch); | |
530 | ||
531 | err: | |
532 | mutex_unlock(&klp_mutex); | |
533 | return ret; | |
534 | } | |
535 | EXPORT_SYMBOL_GPL(klp_disable_patch); | |
536 | ||
537 | static int __klp_enable_patch(struct klp_patch *patch) | |
538 | { | |
539 | struct klp_object *obj; | |
540 | int ret; | |
541 | ||
542 | if (WARN_ON(patch->state != KLP_DISABLED)) | |
543 | return -EINVAL; | |
544 | ||
83a90bb1 JP |
545 | /* enforce stacking: only the first disabled patch can be enabled */ |
546 | if (patch->list.prev != &klp_patches && | |
547 | list_prev_entry(patch, list)->state == KLP_DISABLED) | |
548 | return -EBUSY; | |
549 | ||
b700e7f0 SJ |
550 | pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n"); |
551 | add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK); | |
552 | ||
553 | pr_notice("enabling patch '%s'\n", patch->mod->name); | |
554 | ||
555 | for (obj = patch->objs; obj->funcs; obj++) { | |
556 | klp_find_object_module(obj); | |
557 | ||
558 | if (!klp_is_object_loaded(obj)) | |
559 | continue; | |
560 | ||
561 | ret = klp_enable_object(obj); | |
562 | if (ret) | |
563 | goto unregister; | |
564 | } | |
565 | ||
566 | patch->state = KLP_ENABLED; | |
567 | ||
568 | return 0; | |
569 | ||
570 | unregister: | |
571 | WARN_ON(__klp_disable_patch(patch)); | |
572 | return ret; | |
573 | } | |
574 | ||
575 | /** | |
576 | * klp_enable_patch() - enables a registered patch | |
577 | * @patch: The registered, disabled patch to be enabled | |
578 | * | |
579 | * Performs the needed symbol lookups and code relocations, | |
580 | * then registers the patched functions with ftrace. | |
581 | * | |
582 | * Return: 0 on success, otherwise error | |
583 | */ | |
584 | int klp_enable_patch(struct klp_patch *patch) | |
585 | { | |
586 | int ret; | |
587 | ||
588 | mutex_lock(&klp_mutex); | |
589 | ||
590 | if (!klp_is_patch_registered(patch)) { | |
591 | ret = -EINVAL; | |
592 | goto err; | |
593 | } | |
594 | ||
595 | ret = __klp_enable_patch(patch); | |
596 | ||
597 | err: | |
598 | mutex_unlock(&klp_mutex); | |
599 | return ret; | |
600 | } | |
601 | EXPORT_SYMBOL_GPL(klp_enable_patch); | |
602 | ||
603 | /* | |
604 | * Sysfs Interface | |
605 | * | |
606 | * /sys/kernel/livepatch | |
607 | * /sys/kernel/livepatch/<patch> | |
608 | * /sys/kernel/livepatch/<patch>/enabled | |
609 | * /sys/kernel/livepatch/<patch>/<object> | |
610 | * /sys/kernel/livepatch/<patch>/<object>/<func> | |
611 | */ | |
612 | ||
613 | static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, | |
614 | const char *buf, size_t count) | |
615 | { | |
616 | struct klp_patch *patch; | |
617 | int ret; | |
618 | unsigned long val; | |
619 | ||
620 | ret = kstrtoul(buf, 10, &val); | |
621 | if (ret) | |
622 | return -EINVAL; | |
623 | ||
624 | if (val != KLP_DISABLED && val != KLP_ENABLED) | |
625 | return -EINVAL; | |
626 | ||
627 | patch = container_of(kobj, struct klp_patch, kobj); | |
628 | ||
629 | mutex_lock(&klp_mutex); | |
630 | ||
631 | if (val == patch->state) { | |
632 | /* already in requested state */ | |
633 | ret = -EINVAL; | |
634 | goto err; | |
635 | } | |
636 | ||
637 | if (val == KLP_ENABLED) { | |
638 | ret = __klp_enable_patch(patch); | |
639 | if (ret) | |
640 | goto err; | |
641 | } else { | |
642 | ret = __klp_disable_patch(patch); | |
643 | if (ret) | |
644 | goto err; | |
645 | } | |
646 | ||
647 | mutex_unlock(&klp_mutex); | |
648 | ||
649 | return count; | |
650 | ||
651 | err: | |
652 | mutex_unlock(&klp_mutex); | |
653 | return ret; | |
654 | } | |
655 | ||
656 | static ssize_t enabled_show(struct kobject *kobj, | |
657 | struct kobj_attribute *attr, char *buf) | |
658 | { | |
659 | struct klp_patch *patch; | |
660 | ||
661 | patch = container_of(kobj, struct klp_patch, kobj); | |
662 | return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state); | |
663 | } | |
664 | ||
665 | static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled); | |
666 | static struct attribute *klp_patch_attrs[] = { | |
667 | &enabled_kobj_attr.attr, | |
668 | NULL | |
669 | }; | |
670 | ||
671 | static void klp_kobj_release_patch(struct kobject *kobj) | |
672 | { | |
673 | /* | |
674 | * Once we have a consistency model we'll need to module_put() the | |
675 | * patch module here. See klp_register_patch() for more details. | |
676 | */ | |
677 | } | |
678 | ||
679 | static struct kobj_type klp_ktype_patch = { | |
680 | .release = klp_kobj_release_patch, | |
681 | .sysfs_ops = &kobj_sysfs_ops, | |
682 | .default_attrs = klp_patch_attrs, | |
683 | }; | |
684 | ||
685 | static void klp_kobj_release_func(struct kobject *kobj) | |
686 | { | |
b700e7f0 SJ |
687 | } |
688 | ||
689 | static struct kobj_type klp_ktype_func = { | |
690 | .release = klp_kobj_release_func, | |
691 | .sysfs_ops = &kobj_sysfs_ops, | |
692 | }; | |
693 | ||
694 | /* | |
695 | * Free all functions' kobjects in the array up to some limit. When limit is | |
696 | * NULL, all kobjects are freed. | |
697 | */ | |
698 | static void klp_free_funcs_limited(struct klp_object *obj, | |
699 | struct klp_func *limit) | |
700 | { | |
701 | struct klp_func *func; | |
702 | ||
703 | for (func = obj->funcs; func->old_name && func != limit; func++) | |
704 | kobject_put(&func->kobj); | |
705 | } | |
706 | ||
707 | /* Clean up when a patched object is unloaded */ | |
708 | static void klp_free_object_loaded(struct klp_object *obj) | |
709 | { | |
710 | struct klp_func *func; | |
711 | ||
712 | obj->mod = NULL; | |
713 | ||
714 | for (func = obj->funcs; func->old_name; func++) | |
715 | func->old_addr = 0; | |
716 | } | |
717 | ||
718 | /* | |
719 | * Free all objects' kobjects in the array up to some limit. When limit is | |
720 | * NULL, all kobjects are freed. | |
721 | */ | |
722 | static void klp_free_objects_limited(struct klp_patch *patch, | |
723 | struct klp_object *limit) | |
724 | { | |
725 | struct klp_object *obj; | |
726 | ||
727 | for (obj = patch->objs; obj->funcs && obj != limit; obj++) { | |
728 | klp_free_funcs_limited(obj, NULL); | |
729 | kobject_put(obj->kobj); | |
730 | } | |
731 | } | |
732 | ||
733 | static void klp_free_patch(struct klp_patch *patch) | |
734 | { | |
735 | klp_free_objects_limited(patch, NULL); | |
736 | if (!list_empty(&patch->list)) | |
737 | list_del(&patch->list); | |
738 | kobject_put(&patch->kobj); | |
739 | } | |
740 | ||
741 | static int klp_init_func(struct klp_object *obj, struct klp_func *func) | |
742 | { | |
3c33f5b9 | 743 | INIT_LIST_HEAD(&func->stack_node); |
b700e7f0 SJ |
744 | func->state = KLP_DISABLED; |
745 | ||
3c33f5b9 | 746 | return kobject_init_and_add(&func->kobj, &klp_ktype_func, |
e0b561ee | 747 | obj->kobj, "%s", func->old_name); |
b700e7f0 SJ |
748 | } |
749 | ||
750 | /* parts of the initialization that is done only when the object is loaded */ | |
751 | static int klp_init_object_loaded(struct klp_patch *patch, | |
752 | struct klp_object *obj) | |
753 | { | |
754 | struct klp_func *func; | |
755 | int ret; | |
756 | ||
757 | if (obj->relocs) { | |
758 | ret = klp_write_object_relocations(patch->mod, obj); | |
759 | if (ret) | |
760 | return ret; | |
761 | } | |
762 | ||
763 | for (func = obj->funcs; func->old_name; func++) { | |
764 | ret = klp_find_verify_func_addr(obj, func); | |
765 | if (ret) | |
766 | return ret; | |
767 | } | |
768 | ||
769 | return 0; | |
770 | } | |
771 | ||
772 | static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) | |
773 | { | |
774 | struct klp_func *func; | |
775 | int ret; | |
776 | const char *name; | |
777 | ||
778 | if (!obj->funcs) | |
779 | return -EINVAL; | |
780 | ||
781 | obj->state = KLP_DISABLED; | |
8cb2c2dc | 782 | obj->mod = NULL; |
b700e7f0 SJ |
783 | |
784 | klp_find_object_module(obj); | |
785 | ||
786 | name = klp_is_module(obj) ? obj->name : "vmlinux"; | |
787 | obj->kobj = kobject_create_and_add(name, &patch->kobj); | |
788 | if (!obj->kobj) | |
789 | return -ENOMEM; | |
790 | ||
791 | for (func = obj->funcs; func->old_name; func++) { | |
792 | ret = klp_init_func(obj, func); | |
793 | if (ret) | |
794 | goto free; | |
795 | } | |
796 | ||
797 | if (klp_is_object_loaded(obj)) { | |
798 | ret = klp_init_object_loaded(patch, obj); | |
799 | if (ret) | |
800 | goto free; | |
801 | } | |
802 | ||
803 | return 0; | |
804 | ||
805 | free: | |
806 | klp_free_funcs_limited(obj, func); | |
807 | kobject_put(obj->kobj); | |
808 | return ret; | |
809 | } | |
810 | ||
811 | static int klp_init_patch(struct klp_patch *patch) | |
812 | { | |
813 | struct klp_object *obj; | |
814 | int ret; | |
815 | ||
816 | if (!patch->objs) | |
817 | return -EINVAL; | |
818 | ||
819 | mutex_lock(&klp_mutex); | |
820 | ||
821 | patch->state = KLP_DISABLED; | |
822 | ||
823 | ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch, | |
e0b561ee | 824 | klp_root_kobj, "%s", patch->mod->name); |
b700e7f0 SJ |
825 | if (ret) |
826 | goto unlock; | |
827 | ||
828 | for (obj = patch->objs; obj->funcs; obj++) { | |
829 | ret = klp_init_object(patch, obj); | |
830 | if (ret) | |
831 | goto free; | |
832 | } | |
833 | ||
99590ba5 | 834 | list_add_tail(&patch->list, &klp_patches); |
b700e7f0 SJ |
835 | |
836 | mutex_unlock(&klp_mutex); | |
837 | ||
838 | return 0; | |
839 | ||
840 | free: | |
841 | klp_free_objects_limited(patch, obj); | |
842 | kobject_put(&patch->kobj); | |
843 | unlock: | |
844 | mutex_unlock(&klp_mutex); | |
845 | return ret; | |
846 | } | |
847 | ||
848 | /** | |
849 | * klp_unregister_patch() - unregisters a patch | |
850 | * @patch: Disabled patch to be unregistered | |
851 | * | |
852 | * Frees the data structures and removes the sysfs interface. | |
853 | * | |
854 | * Return: 0 on success, otherwise error | |
855 | */ | |
856 | int klp_unregister_patch(struct klp_patch *patch) | |
857 | { | |
858 | int ret = 0; | |
859 | ||
860 | mutex_lock(&klp_mutex); | |
861 | ||
862 | if (!klp_is_patch_registered(patch)) { | |
863 | ret = -EINVAL; | |
864 | goto out; | |
865 | } | |
866 | ||
867 | if (patch->state == KLP_ENABLED) { | |
868 | ret = -EBUSY; | |
869 | goto out; | |
870 | } | |
871 | ||
872 | klp_free_patch(patch); | |
873 | ||
874 | out: | |
875 | mutex_unlock(&klp_mutex); | |
876 | return ret; | |
877 | } | |
878 | EXPORT_SYMBOL_GPL(klp_unregister_patch); | |
879 | ||
880 | /** | |
881 | * klp_register_patch() - registers a patch | |
882 | * @patch: Patch to be registered | |
883 | * | |
884 | * Initializes the data structure associated with the patch and | |
885 | * creates the sysfs interface. | |
886 | * | |
887 | * Return: 0 on success, otherwise error | |
888 | */ | |
889 | int klp_register_patch(struct klp_patch *patch) | |
890 | { | |
891 | int ret; | |
892 | ||
893 | if (!klp_initialized()) | |
894 | return -ENODEV; | |
895 | ||
896 | if (!patch || !patch->mod) | |
897 | return -EINVAL; | |
898 | ||
899 | /* | |
900 | * A reference is taken on the patch module to prevent it from being | |
901 | * unloaded. Right now, we don't allow patch modules to unload since | |
902 | * there is currently no method to determine if a thread is still | |
903 | * running in the patched code contained in the patch module once | |
904 | * the ftrace registration is successful. | |
905 | */ | |
906 | if (!try_module_get(patch->mod)) | |
907 | return -ENODEV; | |
908 | ||
909 | ret = klp_init_patch(patch); | |
910 | if (ret) | |
911 | module_put(patch->mod); | |
912 | ||
913 | return ret; | |
914 | } | |
915 | EXPORT_SYMBOL_GPL(klp_register_patch); | |
916 | ||
917 | static void klp_module_notify_coming(struct klp_patch *patch, | |
918 | struct klp_object *obj) | |
919 | { | |
920 | struct module *pmod = patch->mod; | |
921 | struct module *mod = obj->mod; | |
922 | int ret; | |
923 | ||
924 | ret = klp_init_object_loaded(patch, obj); | |
925 | if (ret) | |
926 | goto err; | |
927 | ||
928 | if (patch->state == KLP_DISABLED) | |
929 | return; | |
930 | ||
931 | pr_notice("applying patch '%s' to loading module '%s'\n", | |
932 | pmod->name, mod->name); | |
933 | ||
934 | ret = klp_enable_object(obj); | |
935 | if (!ret) | |
936 | return; | |
937 | ||
938 | err: | |
939 | pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", | |
940 | pmod->name, mod->name, ret); | |
941 | } | |
942 | ||
943 | static void klp_module_notify_going(struct klp_patch *patch, | |
944 | struct klp_object *obj) | |
945 | { | |
946 | struct module *pmod = patch->mod; | |
947 | struct module *mod = obj->mod; | |
948 | int ret; | |
949 | ||
950 | if (patch->state == KLP_DISABLED) | |
951 | goto disabled; | |
952 | ||
953 | pr_notice("reverting patch '%s' on unloading module '%s'\n", | |
954 | pmod->name, mod->name); | |
955 | ||
956 | ret = klp_disable_object(obj); | |
957 | if (ret) | |
958 | pr_warn("failed to revert patch '%s' on module '%s' (%d)\n", | |
959 | pmod->name, mod->name, ret); | |
960 | ||
961 | disabled: | |
962 | klp_free_object_loaded(obj); | |
963 | } | |
964 | ||
965 | static int klp_module_notify(struct notifier_block *nb, unsigned long action, | |
966 | void *data) | |
967 | { | |
968 | struct module *mod = data; | |
969 | struct klp_patch *patch; | |
970 | struct klp_object *obj; | |
971 | ||
972 | if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING) | |
973 | return 0; | |
974 | ||
975 | mutex_lock(&klp_mutex); | |
976 | ||
8cb2c2dc PM |
977 | /* |
978 | * Each module has to know that the notifier has been called. | |
979 | * We never know what module will get patched by a new patch. | |
980 | */ | |
981 | if (action == MODULE_STATE_COMING) | |
982 | mod->klp_alive = true; | |
983 | else /* MODULE_STATE_GOING */ | |
984 | mod->klp_alive = false; | |
985 | ||
b700e7f0 SJ |
986 | list_for_each_entry(patch, &klp_patches, list) { |
987 | for (obj = patch->objs; obj->funcs; obj++) { | |
988 | if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) | |
989 | continue; | |
990 | ||
991 | if (action == MODULE_STATE_COMING) { | |
992 | obj->mod = mod; | |
993 | klp_module_notify_coming(patch, obj); | |
994 | } else /* MODULE_STATE_GOING */ | |
995 | klp_module_notify_going(patch, obj); | |
996 | ||
997 | break; | |
998 | } | |
999 | } | |
1000 | ||
1001 | mutex_unlock(&klp_mutex); | |
1002 | ||
1003 | return 0; | |
1004 | } | |
1005 | ||
1006 | static struct notifier_block klp_module_nb = { | |
1007 | .notifier_call = klp_module_notify, | |
1008 | .priority = INT_MIN+1, /* called late but before ftrace notifier */ | |
1009 | }; | |
1010 | ||
1011 | static int klp_init(void) | |
1012 | { | |
1013 | int ret; | |
1014 | ||
b9dfe0be JK |
1015 | ret = klp_check_compiler_support(); |
1016 | if (ret) { | |
1017 | pr_info("Your compiler is too old; turning off.\n"); | |
1018 | return -EINVAL; | |
1019 | } | |
1020 | ||
b700e7f0 SJ |
1021 | ret = register_module_notifier(&klp_module_nb); |
1022 | if (ret) | |
1023 | return ret; | |
1024 | ||
1025 | klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); | |
1026 | if (!klp_root_kobj) { | |
1027 | ret = -ENOMEM; | |
1028 | goto unregister; | |
1029 | } | |
1030 | ||
1031 | return 0; | |
1032 | ||
1033 | unregister: | |
1034 | unregister_module_notifier(&klp_module_nb); | |
1035 | return ret; | |
1036 | } | |
1037 | ||
1038 | module_init(klp_init); |