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