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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 | { | |
e76ff06a | 131 | return !!klp_root_kobj; |
b700e7f0 SJ |
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 | ||
0937e3b0 | 338 | static void klp_disable_func(struct klp_func *func) |
b700e7f0 | 339 | { |
3c33f5b9 | 340 | struct klp_ops *ops; |
b700e7f0 | 341 | |
0937e3b0 JP |
342 | WARN_ON(func->state != KLP_ENABLED); |
343 | WARN_ON(!func->old_addr); | |
b700e7f0 | 344 | |
3c33f5b9 JP |
345 | ops = klp_find_ops(func->old_addr); |
346 | if (WARN_ON(!ops)) | |
0937e3b0 | 347 | return; |
b700e7f0 | 348 | |
3c33f5b9 | 349 | if (list_is_singular(&ops->func_stack)) { |
0937e3b0 JP |
350 | WARN_ON(unregister_ftrace_function(&ops->fops)); |
351 | WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0)); | |
3c33f5b9 JP |
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; | |
b700e7f0 SJ |
361 | } |
362 | ||
363 | static int klp_enable_func(struct klp_func *func) | |
364 | { | |
3c33f5b9 | 365 | struct klp_ops *ops; |
b700e7f0 SJ |
366 | int ret; |
367 | ||
368 | if (WARN_ON(!func->old_addr)) | |
369 | return -EINVAL; | |
370 | ||
371 | if (WARN_ON(func->state != KLP_DISABLED)) | |
372 | return -EINVAL; | |
373 | ||
3c33f5b9 JP |
374 | ops = klp_find_ops(func->old_addr); |
375 | if (!ops) { | |
376 | ops = kzalloc(sizeof(*ops), GFP_KERNEL); | |
377 | if (!ops) | |
378 | return -ENOMEM; | |
379 | ||
380 | ops->fops.func = klp_ftrace_handler; | |
381 | ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS | | |
382 | FTRACE_OPS_FL_DYNAMIC | | |
383 | FTRACE_OPS_FL_IPMODIFY; | |
384 | ||
385 | list_add(&ops->node, &klp_ops); | |
386 | ||
387 | INIT_LIST_HEAD(&ops->func_stack); | |
388 | list_add_rcu(&func->stack_node, &ops->func_stack); | |
389 | ||
390 | ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0); | |
391 | if (ret) { | |
392 | pr_err("failed to set ftrace filter for function '%s' (%d)\n", | |
393 | func->old_name, ret); | |
394 | goto err; | |
395 | } | |
396 | ||
397 | ret = register_ftrace_function(&ops->fops); | |
398 | if (ret) { | |
399 | pr_err("failed to register ftrace handler for function '%s' (%d)\n", | |
400 | func->old_name, ret); | |
401 | ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); | |
402 | goto err; | |
403 | } | |
404 | ||
b700e7f0 | 405 | |
b700e7f0 | 406 | } else { |
3c33f5b9 | 407 | list_add_rcu(&func->stack_node, &ops->func_stack); |
b700e7f0 SJ |
408 | } |
409 | ||
3c33f5b9 JP |
410 | func->state = KLP_ENABLED; |
411 | ||
dbed7dda | 412 | return 0; |
3c33f5b9 JP |
413 | |
414 | err: | |
415 | list_del_rcu(&func->stack_node); | |
416 | list_del(&ops->node); | |
417 | kfree(ops); | |
b700e7f0 SJ |
418 | return ret; |
419 | } | |
420 | ||
0937e3b0 | 421 | static void klp_disable_object(struct klp_object *obj) |
b700e7f0 SJ |
422 | { |
423 | struct klp_func *func; | |
b700e7f0 | 424 | |
0937e3b0 JP |
425 | for (func = obj->funcs; func->old_name; func++) |
426 | if (func->state == KLP_ENABLED) | |
427 | klp_disable_func(func); | |
b700e7f0 SJ |
428 | |
429 | obj->state = KLP_DISABLED; | |
b700e7f0 SJ |
430 | } |
431 | ||
432 | static int klp_enable_object(struct klp_object *obj) | |
433 | { | |
434 | struct klp_func *func; | |
435 | int ret; | |
436 | ||
437 | if (WARN_ON(obj->state != KLP_DISABLED)) | |
438 | return -EINVAL; | |
439 | ||
440 | if (WARN_ON(!klp_is_object_loaded(obj))) | |
441 | return -EINVAL; | |
442 | ||
443 | for (func = obj->funcs; func->old_name; func++) { | |
444 | ret = klp_enable_func(func); | |
0937e3b0 JP |
445 | if (ret) { |
446 | klp_disable_object(obj); | |
447 | return ret; | |
448 | } | |
b700e7f0 SJ |
449 | } |
450 | obj->state = KLP_ENABLED; | |
451 | ||
452 | return 0; | |
b700e7f0 SJ |
453 | } |
454 | ||
455 | static int __klp_disable_patch(struct klp_patch *patch) | |
456 | { | |
457 | struct klp_object *obj; | |
b700e7f0 | 458 | |
83a90bb1 JP |
459 | /* enforce stacking: only the last enabled patch can be disabled */ |
460 | if (!list_is_last(&patch->list, &klp_patches) && | |
461 | list_next_entry(patch, list)->state == KLP_ENABLED) | |
462 | return -EBUSY; | |
463 | ||
b700e7f0 SJ |
464 | pr_notice("disabling patch '%s'\n", patch->mod->name); |
465 | ||
466 | for (obj = patch->objs; obj->funcs; obj++) { | |
0937e3b0 JP |
467 | if (obj->state == KLP_ENABLED) |
468 | klp_disable_object(obj); | |
b700e7f0 SJ |
469 | } |
470 | ||
471 | patch->state = KLP_DISABLED; | |
472 | ||
473 | return 0; | |
474 | } | |
475 | ||
476 | /** | |
477 | * klp_disable_patch() - disables a registered patch | |
478 | * @patch: The registered, enabled patch to be disabled | |
479 | * | |
480 | * Unregisters the patched functions from ftrace. | |
481 | * | |
482 | * Return: 0 on success, otherwise error | |
483 | */ | |
484 | int klp_disable_patch(struct klp_patch *patch) | |
485 | { | |
486 | int ret; | |
487 | ||
488 | mutex_lock(&klp_mutex); | |
489 | ||
490 | if (!klp_is_patch_registered(patch)) { | |
491 | ret = -EINVAL; | |
492 | goto err; | |
493 | } | |
494 | ||
495 | if (patch->state == KLP_DISABLED) { | |
496 | ret = -EINVAL; | |
497 | goto err; | |
498 | } | |
499 | ||
500 | ret = __klp_disable_patch(patch); | |
501 | ||
502 | err: | |
503 | mutex_unlock(&klp_mutex); | |
504 | return ret; | |
505 | } | |
506 | EXPORT_SYMBOL_GPL(klp_disable_patch); | |
507 | ||
508 | static int __klp_enable_patch(struct klp_patch *patch) | |
509 | { | |
510 | struct klp_object *obj; | |
511 | int ret; | |
512 | ||
513 | if (WARN_ON(patch->state != KLP_DISABLED)) | |
514 | return -EINVAL; | |
515 | ||
83a90bb1 JP |
516 | /* enforce stacking: only the first disabled patch can be enabled */ |
517 | if (patch->list.prev != &klp_patches && | |
518 | list_prev_entry(patch, list)->state == KLP_DISABLED) | |
519 | return -EBUSY; | |
520 | ||
b700e7f0 SJ |
521 | pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n"); |
522 | add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK); | |
523 | ||
524 | pr_notice("enabling patch '%s'\n", patch->mod->name); | |
525 | ||
526 | for (obj = patch->objs; obj->funcs; obj++) { | |
b700e7f0 SJ |
527 | if (!klp_is_object_loaded(obj)) |
528 | continue; | |
529 | ||
530 | ret = klp_enable_object(obj); | |
531 | if (ret) | |
532 | goto unregister; | |
533 | } | |
534 | ||
535 | patch->state = KLP_ENABLED; | |
536 | ||
537 | return 0; | |
538 | ||
539 | unregister: | |
540 | WARN_ON(__klp_disable_patch(patch)); | |
541 | return ret; | |
542 | } | |
543 | ||
544 | /** | |
545 | * klp_enable_patch() - enables a registered patch | |
546 | * @patch: The registered, disabled patch to be enabled | |
547 | * | |
548 | * Performs the needed symbol lookups and code relocations, | |
549 | * then registers the patched functions with ftrace. | |
550 | * | |
551 | * Return: 0 on success, otherwise error | |
552 | */ | |
553 | int klp_enable_patch(struct klp_patch *patch) | |
554 | { | |
555 | int ret; | |
556 | ||
557 | mutex_lock(&klp_mutex); | |
558 | ||
559 | if (!klp_is_patch_registered(patch)) { | |
560 | ret = -EINVAL; | |
561 | goto err; | |
562 | } | |
563 | ||
564 | ret = __klp_enable_patch(patch); | |
565 | ||
566 | err: | |
567 | mutex_unlock(&klp_mutex); | |
568 | return ret; | |
569 | } | |
570 | EXPORT_SYMBOL_GPL(klp_enable_patch); | |
571 | ||
572 | /* | |
573 | * Sysfs Interface | |
574 | * | |
575 | * /sys/kernel/livepatch | |
576 | * /sys/kernel/livepatch/<patch> | |
577 | * /sys/kernel/livepatch/<patch>/enabled | |
578 | * /sys/kernel/livepatch/<patch>/<object> | |
579 | * /sys/kernel/livepatch/<patch>/<object>/<func> | |
580 | */ | |
581 | ||
582 | static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, | |
583 | const char *buf, size_t count) | |
584 | { | |
585 | struct klp_patch *patch; | |
586 | int ret; | |
587 | unsigned long val; | |
588 | ||
589 | ret = kstrtoul(buf, 10, &val); | |
590 | if (ret) | |
591 | return -EINVAL; | |
592 | ||
593 | if (val != KLP_DISABLED && val != KLP_ENABLED) | |
594 | return -EINVAL; | |
595 | ||
596 | patch = container_of(kobj, struct klp_patch, kobj); | |
597 | ||
598 | mutex_lock(&klp_mutex); | |
599 | ||
600 | if (val == patch->state) { | |
601 | /* already in requested state */ | |
602 | ret = -EINVAL; | |
603 | goto err; | |
604 | } | |
605 | ||
606 | if (val == KLP_ENABLED) { | |
607 | ret = __klp_enable_patch(patch); | |
608 | if (ret) | |
609 | goto err; | |
610 | } else { | |
611 | ret = __klp_disable_patch(patch); | |
612 | if (ret) | |
613 | goto err; | |
614 | } | |
615 | ||
616 | mutex_unlock(&klp_mutex); | |
617 | ||
618 | return count; | |
619 | ||
620 | err: | |
621 | mutex_unlock(&klp_mutex); | |
622 | return ret; | |
623 | } | |
624 | ||
625 | static ssize_t enabled_show(struct kobject *kobj, | |
626 | struct kobj_attribute *attr, char *buf) | |
627 | { | |
628 | struct klp_patch *patch; | |
629 | ||
630 | patch = container_of(kobj, struct klp_patch, kobj); | |
631 | return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state); | |
632 | } | |
633 | ||
634 | static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled); | |
635 | static struct attribute *klp_patch_attrs[] = { | |
636 | &enabled_kobj_attr.attr, | |
637 | NULL | |
638 | }; | |
639 | ||
640 | static void klp_kobj_release_patch(struct kobject *kobj) | |
641 | { | |
642 | /* | |
643 | * Once we have a consistency model we'll need to module_put() the | |
644 | * patch module here. See klp_register_patch() for more details. | |
645 | */ | |
646 | } | |
647 | ||
648 | static struct kobj_type klp_ktype_patch = { | |
649 | .release = klp_kobj_release_patch, | |
650 | .sysfs_ops = &kobj_sysfs_ops, | |
651 | .default_attrs = klp_patch_attrs, | |
652 | }; | |
653 | ||
654 | static void klp_kobj_release_func(struct kobject *kobj) | |
655 | { | |
b700e7f0 SJ |
656 | } |
657 | ||
658 | static struct kobj_type klp_ktype_func = { | |
659 | .release = klp_kobj_release_func, | |
660 | .sysfs_ops = &kobj_sysfs_ops, | |
661 | }; | |
662 | ||
663 | /* | |
664 | * Free all functions' kobjects in the array up to some limit. When limit is | |
665 | * NULL, all kobjects are freed. | |
666 | */ | |
667 | static void klp_free_funcs_limited(struct klp_object *obj, | |
668 | struct klp_func *limit) | |
669 | { | |
670 | struct klp_func *func; | |
671 | ||
672 | for (func = obj->funcs; func->old_name && func != limit; func++) | |
673 | kobject_put(&func->kobj); | |
674 | } | |
675 | ||
676 | /* Clean up when a patched object is unloaded */ | |
677 | static void klp_free_object_loaded(struct klp_object *obj) | |
678 | { | |
679 | struct klp_func *func; | |
680 | ||
681 | obj->mod = NULL; | |
682 | ||
683 | for (func = obj->funcs; func->old_name; func++) | |
684 | func->old_addr = 0; | |
685 | } | |
686 | ||
687 | /* | |
688 | * Free all objects' kobjects in the array up to some limit. When limit is | |
689 | * NULL, all kobjects are freed. | |
690 | */ | |
691 | static void klp_free_objects_limited(struct klp_patch *patch, | |
692 | struct klp_object *limit) | |
693 | { | |
694 | struct klp_object *obj; | |
695 | ||
696 | for (obj = patch->objs; obj->funcs && obj != limit; obj++) { | |
697 | klp_free_funcs_limited(obj, NULL); | |
698 | kobject_put(obj->kobj); | |
699 | } | |
700 | } | |
701 | ||
702 | static void klp_free_patch(struct klp_patch *patch) | |
703 | { | |
704 | klp_free_objects_limited(patch, NULL); | |
705 | if (!list_empty(&patch->list)) | |
706 | list_del(&patch->list); | |
707 | kobject_put(&patch->kobj); | |
708 | } | |
709 | ||
710 | static int klp_init_func(struct klp_object *obj, struct klp_func *func) | |
711 | { | |
3c33f5b9 | 712 | INIT_LIST_HEAD(&func->stack_node); |
b700e7f0 SJ |
713 | func->state = KLP_DISABLED; |
714 | ||
3c33f5b9 | 715 | return kobject_init_and_add(&func->kobj, &klp_ktype_func, |
e0b561ee | 716 | obj->kobj, "%s", func->old_name); |
b700e7f0 SJ |
717 | } |
718 | ||
719 | /* parts of the initialization that is done only when the object is loaded */ | |
720 | static int klp_init_object_loaded(struct klp_patch *patch, | |
721 | struct klp_object *obj) | |
722 | { | |
723 | struct klp_func *func; | |
724 | int ret; | |
725 | ||
726 | if (obj->relocs) { | |
727 | ret = klp_write_object_relocations(patch->mod, obj); | |
728 | if (ret) | |
729 | return ret; | |
730 | } | |
731 | ||
732 | for (func = obj->funcs; func->old_name; func++) { | |
733 | ret = klp_find_verify_func_addr(obj, func); | |
734 | if (ret) | |
735 | return ret; | |
736 | } | |
737 | ||
738 | return 0; | |
739 | } | |
740 | ||
741 | static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) | |
742 | { | |
743 | struct klp_func *func; | |
744 | int ret; | |
745 | const char *name; | |
746 | ||
747 | if (!obj->funcs) | |
748 | return -EINVAL; | |
749 | ||
750 | obj->state = KLP_DISABLED; | |
8cb2c2dc | 751 | obj->mod = NULL; |
b700e7f0 SJ |
752 | |
753 | klp_find_object_module(obj); | |
754 | ||
755 | name = klp_is_module(obj) ? obj->name : "vmlinux"; | |
756 | obj->kobj = kobject_create_and_add(name, &patch->kobj); | |
757 | if (!obj->kobj) | |
758 | return -ENOMEM; | |
759 | ||
760 | for (func = obj->funcs; func->old_name; func++) { | |
761 | ret = klp_init_func(obj, func); | |
762 | if (ret) | |
763 | goto free; | |
764 | } | |
765 | ||
766 | if (klp_is_object_loaded(obj)) { | |
767 | ret = klp_init_object_loaded(patch, obj); | |
768 | if (ret) | |
769 | goto free; | |
770 | } | |
771 | ||
772 | return 0; | |
773 | ||
774 | free: | |
775 | klp_free_funcs_limited(obj, func); | |
776 | kobject_put(obj->kobj); | |
777 | return ret; | |
778 | } | |
779 | ||
780 | static int klp_init_patch(struct klp_patch *patch) | |
781 | { | |
782 | struct klp_object *obj; | |
783 | int ret; | |
784 | ||
785 | if (!patch->objs) | |
786 | return -EINVAL; | |
787 | ||
788 | mutex_lock(&klp_mutex); | |
789 | ||
790 | patch->state = KLP_DISABLED; | |
791 | ||
792 | ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch, | |
e0b561ee | 793 | klp_root_kobj, "%s", patch->mod->name); |
b700e7f0 SJ |
794 | if (ret) |
795 | goto unlock; | |
796 | ||
797 | for (obj = patch->objs; obj->funcs; obj++) { | |
798 | ret = klp_init_object(patch, obj); | |
799 | if (ret) | |
800 | goto free; | |
801 | } | |
802 | ||
99590ba5 | 803 | list_add_tail(&patch->list, &klp_patches); |
b700e7f0 SJ |
804 | |
805 | mutex_unlock(&klp_mutex); | |
806 | ||
807 | return 0; | |
808 | ||
809 | free: | |
810 | klp_free_objects_limited(patch, obj); | |
811 | kobject_put(&patch->kobj); | |
812 | unlock: | |
813 | mutex_unlock(&klp_mutex); | |
814 | return ret; | |
815 | } | |
816 | ||
817 | /** | |
818 | * klp_unregister_patch() - unregisters a patch | |
819 | * @patch: Disabled patch to be unregistered | |
820 | * | |
821 | * Frees the data structures and removes the sysfs interface. | |
822 | * | |
823 | * Return: 0 on success, otherwise error | |
824 | */ | |
825 | int klp_unregister_patch(struct klp_patch *patch) | |
826 | { | |
827 | int ret = 0; | |
828 | ||
829 | mutex_lock(&klp_mutex); | |
830 | ||
831 | if (!klp_is_patch_registered(patch)) { | |
832 | ret = -EINVAL; | |
833 | goto out; | |
834 | } | |
835 | ||
836 | if (patch->state == KLP_ENABLED) { | |
837 | ret = -EBUSY; | |
838 | goto out; | |
839 | } | |
840 | ||
841 | klp_free_patch(patch); | |
842 | ||
843 | out: | |
844 | mutex_unlock(&klp_mutex); | |
845 | return ret; | |
846 | } | |
847 | EXPORT_SYMBOL_GPL(klp_unregister_patch); | |
848 | ||
849 | /** | |
850 | * klp_register_patch() - registers a patch | |
851 | * @patch: Patch to be registered | |
852 | * | |
853 | * Initializes the data structure associated with the patch and | |
854 | * creates the sysfs interface. | |
855 | * | |
856 | * Return: 0 on success, otherwise error | |
857 | */ | |
858 | int klp_register_patch(struct klp_patch *patch) | |
859 | { | |
860 | int ret; | |
861 | ||
862 | if (!klp_initialized()) | |
863 | return -ENODEV; | |
864 | ||
865 | if (!patch || !patch->mod) | |
866 | return -EINVAL; | |
867 | ||
868 | /* | |
869 | * A reference is taken on the patch module to prevent it from being | |
870 | * unloaded. Right now, we don't allow patch modules to unload since | |
871 | * there is currently no method to determine if a thread is still | |
872 | * running in the patched code contained in the patch module once | |
873 | * the ftrace registration is successful. | |
874 | */ | |
875 | if (!try_module_get(patch->mod)) | |
876 | return -ENODEV; | |
877 | ||
878 | ret = klp_init_patch(patch); | |
879 | if (ret) | |
880 | module_put(patch->mod); | |
881 | ||
882 | return ret; | |
883 | } | |
884 | EXPORT_SYMBOL_GPL(klp_register_patch); | |
885 | ||
36e505c1 | 886 | static int klp_module_notify_coming(struct klp_patch *patch, |
b700e7f0 SJ |
887 | struct klp_object *obj) |
888 | { | |
889 | struct module *pmod = patch->mod; | |
890 | struct module *mod = obj->mod; | |
891 | int ret; | |
892 | ||
893 | ret = klp_init_object_loaded(patch, obj); | |
36e505c1 MH |
894 | if (ret) { |
895 | pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n", | |
896 | pmod->name, mod->name, ret); | |
897 | return ret; | |
898 | } | |
b700e7f0 SJ |
899 | |
900 | if (patch->state == KLP_DISABLED) | |
36e505c1 | 901 | return 0; |
b700e7f0 SJ |
902 | |
903 | pr_notice("applying patch '%s' to loading module '%s'\n", | |
904 | pmod->name, mod->name); | |
905 | ||
906 | ret = klp_enable_object(obj); | |
36e505c1 MH |
907 | if (ret) |
908 | pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", | |
909 | pmod->name, mod->name, ret); | |
910 | return ret; | |
b700e7f0 SJ |
911 | } |
912 | ||
913 | static void klp_module_notify_going(struct klp_patch *patch, | |
914 | struct klp_object *obj) | |
915 | { | |
916 | struct module *pmod = patch->mod; | |
917 | struct module *mod = obj->mod; | |
b700e7f0 SJ |
918 | |
919 | if (patch->state == KLP_DISABLED) | |
920 | goto disabled; | |
921 | ||
922 | pr_notice("reverting patch '%s' on unloading module '%s'\n", | |
923 | pmod->name, mod->name); | |
924 | ||
0937e3b0 | 925 | klp_disable_object(obj); |
b700e7f0 SJ |
926 | |
927 | disabled: | |
928 | klp_free_object_loaded(obj); | |
929 | } | |
930 | ||
931 | static int klp_module_notify(struct notifier_block *nb, unsigned long action, | |
932 | void *data) | |
933 | { | |
36e505c1 | 934 | int ret; |
b700e7f0 SJ |
935 | struct module *mod = data; |
936 | struct klp_patch *patch; | |
937 | struct klp_object *obj; | |
938 | ||
939 | if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING) | |
940 | return 0; | |
941 | ||
942 | mutex_lock(&klp_mutex); | |
943 | ||
8cb2c2dc PM |
944 | /* |
945 | * Each module has to know that the notifier has been called. | |
946 | * We never know what module will get patched by a new patch. | |
947 | */ | |
948 | if (action == MODULE_STATE_COMING) | |
949 | mod->klp_alive = true; | |
950 | else /* MODULE_STATE_GOING */ | |
951 | mod->klp_alive = false; | |
952 | ||
b700e7f0 SJ |
953 | list_for_each_entry(patch, &klp_patches, list) { |
954 | for (obj = patch->objs; obj->funcs; obj++) { | |
955 | if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) | |
956 | continue; | |
957 | ||
958 | if (action == MODULE_STATE_COMING) { | |
959 | obj->mod = mod; | |
36e505c1 MH |
960 | ret = klp_module_notify_coming(patch, obj); |
961 | if (ret) { | |
962 | obj->mod = NULL; | |
963 | pr_warn("patch '%s' is in an inconsistent state!\n", | |
964 | patch->mod->name); | |
965 | } | |
b700e7f0 SJ |
966 | } else /* MODULE_STATE_GOING */ |
967 | klp_module_notify_going(patch, obj); | |
968 | ||
969 | break; | |
970 | } | |
971 | } | |
972 | ||
973 | mutex_unlock(&klp_mutex); | |
974 | ||
975 | return 0; | |
976 | } | |
977 | ||
978 | static struct notifier_block klp_module_nb = { | |
979 | .notifier_call = klp_module_notify, | |
980 | .priority = INT_MIN+1, /* called late but before ftrace notifier */ | |
981 | }; | |
982 | ||
983 | static int klp_init(void) | |
984 | { | |
985 | int ret; | |
986 | ||
b9dfe0be JK |
987 | ret = klp_check_compiler_support(); |
988 | if (ret) { | |
989 | pr_info("Your compiler is too old; turning off.\n"); | |
990 | return -EINVAL; | |
991 | } | |
992 | ||
b700e7f0 SJ |
993 | ret = register_module_notifier(&klp_module_nb); |
994 | if (ret) | |
995 | return ret; | |
996 | ||
997 | klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); | |
998 | if (!klp_root_kobj) { | |
999 | ret = -ENOMEM; | |
1000 | goto unregister; | |
1001 | } | |
1002 | ||
1003 | return 0; | |
1004 | ||
1005 | unregister: | |
1006 | unregister_module_notifier(&klp_module_nb); | |
1007 | return ret; | |
1008 | } | |
1009 | ||
1010 | module_init(klp_init); |