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d83a7cb3 JP |
1 | /* |
2 | * transition.c - Kernel Live Patching transition functions | |
3 | * | |
4 | * Copyright (C) 2015-2016 Josh Poimboeuf <jpoimboe@redhat.com> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public License | |
8 | * as published by the Free Software Foundation; either version 2 | |
9 | * of the License, or (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program; if not, see <http://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
21 | ||
22 | #include <linux/cpu.h> | |
23 | #include <linux/stacktrace.h> | |
10517429 | 24 | #include "core.h" |
d83a7cb3 JP |
25 | #include "patch.h" |
26 | #include "transition.h" | |
27 | #include "../sched/sched.h" | |
28 | ||
29 | #define MAX_STACK_ENTRIES 100 | |
30 | #define STACK_ERR_BUF_SIZE 128 | |
31 | ||
d83a7cb3 JP |
32 | struct klp_patch *klp_transition_patch; |
33 | ||
34 | static int klp_target_state = KLP_UNDEFINED; | |
35 | ||
36 | /* | |
37 | * This work can be performed periodically to finish patching or unpatching any | |
38 | * "straggler" tasks which failed to transition in the first attempt. | |
39 | */ | |
40 | static void klp_transition_work_fn(struct work_struct *work) | |
41 | { | |
42 | mutex_lock(&klp_mutex); | |
43 | ||
44 | if (klp_transition_patch) | |
45 | klp_try_complete_transition(); | |
46 | ||
47 | mutex_unlock(&klp_mutex); | |
48 | } | |
49 | static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); | |
50 | ||
842c0884 PM |
51 | /* |
52 | * This function is just a stub to implement a hard force | |
53 | * of synchronize_sched(). This requires synchronizing | |
54 | * tasks even in userspace and idle. | |
55 | */ | |
56 | static void klp_sync(struct work_struct *work) | |
57 | { | |
58 | } | |
59 | ||
60 | /* | |
61 | * We allow to patch also functions where RCU is not watching, | |
62 | * e.g. before user_exit(). We can not rely on the RCU infrastructure | |
63 | * to do the synchronization. Instead hard force the sched synchronization. | |
64 | * | |
65 | * This approach allows to use RCU functions for manipulating func_stack | |
66 | * safely. | |
67 | */ | |
68 | static void klp_synchronize_transition(void) | |
69 | { | |
70 | schedule_on_each_cpu(klp_sync); | |
71 | } | |
72 | ||
d83a7cb3 JP |
73 | /* |
74 | * The transition to the target patch state is complete. Clean up the data | |
75 | * structures. | |
76 | */ | |
77 | static void klp_complete_transition(void) | |
78 | { | |
79 | struct klp_object *obj; | |
80 | struct klp_func *func; | |
81 | struct task_struct *g, *task; | |
82 | unsigned int cpu; | |
3ec24776 | 83 | bool immediate_func = false; |
d83a7cb3 | 84 | |
af026796 JL |
85 | pr_debug("'%s': completing %s transition\n", |
86 | klp_transition_patch->mod->name, | |
87 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
88 | ||
d83a7cb3 JP |
89 | if (klp_target_state == KLP_UNPATCHED) { |
90 | /* | |
91 | * All tasks have transitioned to KLP_UNPATCHED so we can now | |
92 | * remove the new functions from the func_stack. | |
93 | */ | |
94 | klp_unpatch_objects(klp_transition_patch); | |
95 | ||
96 | /* | |
97 | * Make sure klp_ftrace_handler() can no longer see functions | |
98 | * from this patch on the ops->func_stack. Otherwise, after | |
99 | * func->transition gets cleared, the handler may choose a | |
100 | * removed function. | |
101 | */ | |
842c0884 | 102 | klp_synchronize_transition(); |
d83a7cb3 JP |
103 | } |
104 | ||
105 | if (klp_transition_patch->immediate) | |
106 | goto done; | |
107 | ||
3ec24776 JP |
108 | klp_for_each_object(klp_transition_patch, obj) { |
109 | klp_for_each_func(obj, func) { | |
d83a7cb3 | 110 | func->transition = false; |
3ec24776 JP |
111 | if (func->immediate) |
112 | immediate_func = true; | |
113 | } | |
114 | } | |
115 | ||
d83a7cb3 JP |
116 | /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ |
117 | if (klp_target_state == KLP_PATCHED) | |
842c0884 | 118 | klp_synchronize_transition(); |
d83a7cb3 JP |
119 | |
120 | read_lock(&tasklist_lock); | |
121 | for_each_process_thread(g, task) { | |
122 | WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); | |
123 | task->patch_state = KLP_UNDEFINED; | |
124 | } | |
125 | read_unlock(&tasklist_lock); | |
126 | ||
127 | for_each_possible_cpu(cpu) { | |
128 | task = idle_task(cpu); | |
129 | WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); | |
130 | task->patch_state = KLP_UNDEFINED; | |
131 | } | |
132 | ||
133 | done: | |
93862e38 JL |
134 | klp_for_each_object(klp_transition_patch, obj) { |
135 | if (!klp_is_object_loaded(obj)) | |
136 | continue; | |
137 | if (klp_target_state == KLP_PATCHED) | |
138 | klp_post_patch_callback(obj); | |
139 | else if (klp_target_state == KLP_UNPATCHED) | |
140 | klp_post_unpatch_callback(obj); | |
141 | } | |
142 | ||
6116c303 JL |
143 | pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, |
144 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
145 | ||
93862e38 JL |
146 | /* |
147 | * See complementary comment in __klp_enable_patch() for why we | |
148 | * keep the module reference for immediate patches. | |
149 | */ | |
150 | if (!klp_transition_patch->immediate && !immediate_func && | |
151 | klp_target_state == KLP_UNPATCHED) { | |
152 | module_put(klp_transition_patch->mod); | |
153 | } | |
154 | ||
d83a7cb3 JP |
155 | klp_target_state = KLP_UNDEFINED; |
156 | klp_transition_patch = NULL; | |
157 | } | |
158 | ||
159 | /* | |
160 | * This is called in the error path, to cancel a transition before it has | |
161 | * started, i.e. klp_init_transition() has been called but | |
162 | * klp_start_transition() hasn't. If the transition *has* been started, | |
163 | * klp_reverse_transition() should be used instead. | |
164 | */ | |
165 | void klp_cancel_transition(void) | |
166 | { | |
3ec24776 JP |
167 | if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) |
168 | return; | |
169 | ||
af026796 JL |
170 | pr_debug("'%s': canceling patching transition, going to unpatch\n", |
171 | klp_transition_patch->mod->name); | |
172 | ||
3ec24776 | 173 | klp_target_state = KLP_UNPATCHED; |
d83a7cb3 JP |
174 | klp_complete_transition(); |
175 | } | |
176 | ||
177 | /* | |
178 | * Switch the patched state of the task to the set of functions in the target | |
179 | * patch state. | |
180 | * | |
181 | * NOTE: If task is not 'current', the caller must ensure the task is inactive. | |
182 | * Otherwise klp_ftrace_handler() might read the wrong 'patch_state' value. | |
183 | */ | |
184 | void klp_update_patch_state(struct task_struct *task) | |
185 | { | |
842c0884 PM |
186 | /* |
187 | * A variant of synchronize_sched() is used to allow patching functions | |
188 | * where RCU is not watching, see klp_synchronize_transition(). | |
189 | */ | |
190 | preempt_disable_notrace(); | |
d83a7cb3 JP |
191 | |
192 | /* | |
193 | * This test_and_clear_tsk_thread_flag() call also serves as a read | |
194 | * barrier (smp_rmb) for two cases: | |
195 | * | |
196 | * 1) Enforce the order of the TIF_PATCH_PENDING read and the | |
197 | * klp_target_state read. The corresponding write barrier is in | |
198 | * klp_init_transition(). | |
199 | * | |
200 | * 2) Enforce the order of the TIF_PATCH_PENDING read and a future read | |
201 | * of func->transition, if klp_ftrace_handler() is called later on | |
202 | * the same CPU. See __klp_disable_patch(). | |
203 | */ | |
204 | if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) | |
205 | task->patch_state = READ_ONCE(klp_target_state); | |
206 | ||
842c0884 | 207 | preempt_enable_notrace(); |
d83a7cb3 JP |
208 | } |
209 | ||
210 | /* | |
211 | * Determine whether the given stack trace includes any references to a | |
212 | * to-be-patched or to-be-unpatched function. | |
213 | */ | |
214 | static int klp_check_stack_func(struct klp_func *func, | |
215 | struct stack_trace *trace) | |
216 | { | |
217 | unsigned long func_addr, func_size, address; | |
218 | struct klp_ops *ops; | |
219 | int i; | |
220 | ||
221 | if (func->immediate) | |
222 | return 0; | |
223 | ||
224 | for (i = 0; i < trace->nr_entries; i++) { | |
225 | address = trace->entries[i]; | |
226 | ||
227 | if (klp_target_state == KLP_UNPATCHED) { | |
228 | /* | |
229 | * Check for the to-be-unpatched function | |
230 | * (the func itself). | |
231 | */ | |
232 | func_addr = (unsigned long)func->new_func; | |
233 | func_size = func->new_size; | |
234 | } else { | |
235 | /* | |
236 | * Check for the to-be-patched function | |
237 | * (the previous func). | |
238 | */ | |
239 | ops = klp_find_ops(func->old_addr); | |
240 | ||
241 | if (list_is_singular(&ops->func_stack)) { | |
242 | /* original function */ | |
243 | func_addr = func->old_addr; | |
244 | func_size = func->old_size; | |
245 | } else { | |
246 | /* previously patched function */ | |
247 | struct klp_func *prev; | |
248 | ||
249 | prev = list_next_entry(func, stack_node); | |
250 | func_addr = (unsigned long)prev->new_func; | |
251 | func_size = prev->new_size; | |
252 | } | |
253 | } | |
254 | ||
255 | if (address >= func_addr && address < func_addr + func_size) | |
256 | return -EAGAIN; | |
257 | } | |
258 | ||
259 | return 0; | |
260 | } | |
261 | ||
262 | /* | |
263 | * Determine whether it's safe to transition the task to the target patch state | |
264 | * by looking for any to-be-patched or to-be-unpatched functions on its stack. | |
265 | */ | |
266 | static int klp_check_stack(struct task_struct *task, char *err_buf) | |
267 | { | |
268 | static unsigned long entries[MAX_STACK_ENTRIES]; | |
269 | struct stack_trace trace; | |
270 | struct klp_object *obj; | |
271 | struct klp_func *func; | |
272 | int ret; | |
273 | ||
274 | trace.skip = 0; | |
275 | trace.nr_entries = 0; | |
276 | trace.max_entries = MAX_STACK_ENTRIES; | |
277 | trace.entries = entries; | |
278 | ret = save_stack_trace_tsk_reliable(task, &trace); | |
279 | WARN_ON_ONCE(ret == -ENOSYS); | |
280 | if (ret) { | |
281 | snprintf(err_buf, STACK_ERR_BUF_SIZE, | |
282 | "%s: %s:%d has an unreliable stack\n", | |
283 | __func__, task->comm, task->pid); | |
284 | return ret; | |
285 | } | |
286 | ||
287 | klp_for_each_object(klp_transition_patch, obj) { | |
288 | if (!obj->patched) | |
289 | continue; | |
290 | klp_for_each_func(obj, func) { | |
291 | ret = klp_check_stack_func(func, &trace); | |
292 | if (ret) { | |
293 | snprintf(err_buf, STACK_ERR_BUF_SIZE, | |
294 | "%s: %s:%d is sleeping on function %s\n", | |
295 | __func__, task->comm, task->pid, | |
296 | func->old_name); | |
297 | return ret; | |
298 | } | |
299 | } | |
300 | } | |
301 | ||
302 | return 0; | |
303 | } | |
304 | ||
305 | /* | |
306 | * Try to safely switch a task to the target patch state. If it's currently | |
307 | * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or | |
308 | * if the stack is unreliable, return false. | |
309 | */ | |
310 | static bool klp_try_switch_task(struct task_struct *task) | |
311 | { | |
312 | struct rq *rq; | |
313 | struct rq_flags flags; | |
314 | int ret; | |
315 | bool success = false; | |
316 | char err_buf[STACK_ERR_BUF_SIZE]; | |
317 | ||
318 | err_buf[0] = '\0'; | |
319 | ||
320 | /* check if this task has already switched over */ | |
321 | if (task->patch_state == klp_target_state) | |
322 | return true; | |
323 | ||
324 | /* | |
325 | * For arches which don't have reliable stack traces, we have to rely | |
326 | * on other methods (e.g., switching tasks at kernel exit). | |
327 | */ | |
328 | if (!klp_have_reliable_stack()) | |
329 | return false; | |
330 | ||
331 | /* | |
332 | * Now try to check the stack for any to-be-patched or to-be-unpatched | |
333 | * functions. If all goes well, switch the task to the target patch | |
334 | * state. | |
335 | */ | |
336 | rq = task_rq_lock(task, &flags); | |
337 | ||
338 | if (task_running(rq, task) && task != current) { | |
339 | snprintf(err_buf, STACK_ERR_BUF_SIZE, | |
340 | "%s: %s:%d is running\n", __func__, task->comm, | |
341 | task->pid); | |
342 | goto done; | |
343 | } | |
344 | ||
345 | ret = klp_check_stack(task, err_buf); | |
346 | if (ret) | |
347 | goto done; | |
348 | ||
349 | success = true; | |
350 | ||
351 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
352 | task->patch_state = klp_target_state; | |
353 | ||
354 | done: | |
355 | task_rq_unlock(rq, task, &flags); | |
356 | ||
357 | /* | |
358 | * Due to console deadlock issues, pr_debug() can't be used while | |
359 | * holding the task rq lock. Instead we have to use a temporary buffer | |
360 | * and print the debug message after releasing the lock. | |
361 | */ | |
362 | if (err_buf[0] != '\0') | |
363 | pr_debug("%s", err_buf); | |
364 | ||
365 | return success; | |
366 | ||
367 | } | |
368 | ||
369 | /* | |
370 | * Try to switch all remaining tasks to the target patch state by walking the | |
371 | * stacks of sleeping tasks and looking for any to-be-patched or | |
372 | * to-be-unpatched functions. If such functions are found, the task can't be | |
373 | * switched yet. | |
374 | * | |
375 | * If any tasks are still stuck in the initial patch state, schedule a retry. | |
376 | */ | |
377 | void klp_try_complete_transition(void) | |
378 | { | |
379 | unsigned int cpu; | |
380 | struct task_struct *g, *task; | |
381 | bool complete = true; | |
382 | ||
383 | WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); | |
384 | ||
385 | /* | |
386 | * If the patch can be applied or reverted immediately, skip the | |
387 | * per-task transitions. | |
388 | */ | |
389 | if (klp_transition_patch->immediate) | |
390 | goto success; | |
391 | ||
392 | /* | |
393 | * Try to switch the tasks to the target patch state by walking their | |
394 | * stacks and looking for any to-be-patched or to-be-unpatched | |
395 | * functions. If such functions are found on a stack, or if the stack | |
396 | * is deemed unreliable, the task can't be switched yet. | |
397 | * | |
398 | * Usually this will transition most (or all) of the tasks on a system | |
399 | * unless the patch includes changes to a very common function. | |
400 | */ | |
401 | read_lock(&tasklist_lock); | |
402 | for_each_process_thread(g, task) | |
403 | if (!klp_try_switch_task(task)) | |
404 | complete = false; | |
405 | read_unlock(&tasklist_lock); | |
406 | ||
407 | /* | |
408 | * Ditto for the idle "swapper" tasks. | |
409 | */ | |
410 | get_online_cpus(); | |
411 | for_each_possible_cpu(cpu) { | |
412 | task = idle_task(cpu); | |
413 | if (cpu_online(cpu)) { | |
414 | if (!klp_try_switch_task(task)) | |
415 | complete = false; | |
416 | } else if (task->patch_state != klp_target_state) { | |
417 | /* offline idle tasks can be switched immediately */ | |
418 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
419 | task->patch_state = klp_target_state; | |
420 | } | |
421 | } | |
422 | put_online_cpus(); | |
423 | ||
424 | if (!complete) { | |
425 | /* | |
426 | * Some tasks weren't able to be switched over. Try again | |
427 | * later and/or wait for other methods like kernel exit | |
428 | * switching. | |
429 | */ | |
430 | schedule_delayed_work(&klp_transition_work, | |
431 | round_jiffies_relative(HZ)); | |
432 | return; | |
433 | } | |
434 | ||
435 | success: | |
d83a7cb3 JP |
436 | /* we're done, now cleanup the data structures */ |
437 | klp_complete_transition(); | |
438 | } | |
439 | ||
440 | /* | |
441 | * Start the transition to the specified target patch state so tasks can begin | |
442 | * switching to it. | |
443 | */ | |
444 | void klp_start_transition(void) | |
445 | { | |
446 | struct task_struct *g, *task; | |
447 | unsigned int cpu; | |
448 | ||
449 | WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); | |
450 | ||
af026796 JL |
451 | pr_notice("'%s': starting %s transition\n", |
452 | klp_transition_patch->mod->name, | |
d83a7cb3 JP |
453 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); |
454 | ||
455 | /* | |
456 | * If the patch can be applied or reverted immediately, skip the | |
457 | * per-task transitions. | |
458 | */ | |
459 | if (klp_transition_patch->immediate) | |
460 | return; | |
461 | ||
462 | /* | |
463 | * Mark all normal tasks as needing a patch state update. They'll | |
464 | * switch either in klp_try_complete_transition() or as they exit the | |
465 | * kernel. | |
466 | */ | |
467 | read_lock(&tasklist_lock); | |
468 | for_each_process_thread(g, task) | |
469 | if (task->patch_state != klp_target_state) | |
470 | set_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
471 | read_unlock(&tasklist_lock); | |
472 | ||
473 | /* | |
474 | * Mark all idle tasks as needing a patch state update. They'll switch | |
475 | * either in klp_try_complete_transition() or at the idle loop switch | |
476 | * point. | |
477 | */ | |
478 | for_each_possible_cpu(cpu) { | |
479 | task = idle_task(cpu); | |
480 | if (task->patch_state != klp_target_state) | |
481 | set_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
482 | } | |
483 | } | |
484 | ||
485 | /* | |
486 | * Initialize the global target patch state and all tasks to the initial patch | |
487 | * state, and initialize all function transition states to true in preparation | |
488 | * for patching or unpatching. | |
489 | */ | |
490 | void klp_init_transition(struct klp_patch *patch, int state) | |
491 | { | |
492 | struct task_struct *g, *task; | |
493 | unsigned int cpu; | |
494 | struct klp_object *obj; | |
495 | struct klp_func *func; | |
496 | int initial_state = !state; | |
497 | ||
498 | WARN_ON_ONCE(klp_target_state != KLP_UNDEFINED); | |
499 | ||
500 | klp_transition_patch = patch; | |
501 | ||
502 | /* | |
503 | * Set the global target patch state which tasks will switch to. This | |
504 | * has no effect until the TIF_PATCH_PENDING flags get set later. | |
505 | */ | |
506 | klp_target_state = state; | |
507 | ||
af026796 JL |
508 | pr_debug("'%s': initializing %s transition\n", patch->mod->name, |
509 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
510 | ||
d83a7cb3 JP |
511 | /* |
512 | * If the patch can be applied or reverted immediately, skip the | |
513 | * per-task transitions. | |
514 | */ | |
515 | if (patch->immediate) | |
516 | return; | |
517 | ||
518 | /* | |
519 | * Initialize all tasks to the initial patch state to prepare them for | |
520 | * switching to the target state. | |
521 | */ | |
522 | read_lock(&tasklist_lock); | |
523 | for_each_process_thread(g, task) { | |
524 | WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED); | |
525 | task->patch_state = initial_state; | |
526 | } | |
527 | read_unlock(&tasklist_lock); | |
528 | ||
529 | /* | |
530 | * Ditto for the idle "swapper" tasks. | |
531 | */ | |
532 | for_each_possible_cpu(cpu) { | |
533 | task = idle_task(cpu); | |
534 | WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED); | |
535 | task->patch_state = initial_state; | |
536 | } | |
537 | ||
538 | /* | |
539 | * Enforce the order of the task->patch_state initializations and the | |
540 | * func->transition updates to ensure that klp_ftrace_handler() doesn't | |
541 | * see a func in transition with a task->patch_state of KLP_UNDEFINED. | |
542 | * | |
543 | * Also enforce the order of the klp_target_state write and future | |
544 | * TIF_PATCH_PENDING writes to ensure klp_update_patch_state() doesn't | |
545 | * set a task->patch_state to KLP_UNDEFINED. | |
546 | */ | |
547 | smp_wmb(); | |
548 | ||
549 | /* | |
550 | * Set the func transition states so klp_ftrace_handler() will know to | |
551 | * switch to the transition logic. | |
552 | * | |
553 | * When patching, the funcs aren't yet in the func_stack and will be | |
554 | * made visible to the ftrace handler shortly by the calls to | |
555 | * klp_patch_object(). | |
556 | * | |
557 | * When unpatching, the funcs are already in the func_stack and so are | |
558 | * already visible to the ftrace handler. | |
559 | */ | |
560 | klp_for_each_object(patch, obj) | |
561 | klp_for_each_func(obj, func) | |
562 | func->transition = true; | |
563 | } | |
564 | ||
565 | /* | |
566 | * This function can be called in the middle of an existing transition to | |
567 | * reverse the direction of the target patch state. This can be done to | |
568 | * effectively cancel an existing enable or disable operation if there are any | |
569 | * tasks which are stuck in the initial patch state. | |
570 | */ | |
571 | void klp_reverse_transition(void) | |
572 | { | |
573 | unsigned int cpu; | |
574 | struct task_struct *g, *task; | |
575 | ||
af026796 JL |
576 | pr_debug("'%s': reversing transition from %s\n", |
577 | klp_transition_patch->mod->name, | |
578 | klp_target_state == KLP_PATCHED ? "patching to unpatching" : | |
579 | "unpatching to patching"); | |
580 | ||
d83a7cb3 JP |
581 | klp_transition_patch->enabled = !klp_transition_patch->enabled; |
582 | ||
583 | klp_target_state = !klp_target_state; | |
584 | ||
585 | /* | |
586 | * Clear all TIF_PATCH_PENDING flags to prevent races caused by | |
587 | * klp_update_patch_state() running in parallel with | |
588 | * klp_start_transition(). | |
589 | */ | |
590 | read_lock(&tasklist_lock); | |
591 | for_each_process_thread(g, task) | |
592 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
593 | read_unlock(&tasklist_lock); | |
594 | ||
595 | for_each_possible_cpu(cpu) | |
596 | clear_tsk_thread_flag(idle_task(cpu), TIF_PATCH_PENDING); | |
597 | ||
598 | /* Let any remaining calls to klp_update_patch_state() complete */ | |
842c0884 | 599 | klp_synchronize_transition(); |
d83a7cb3 JP |
600 | |
601 | klp_start_transition(); | |
602 | } | |
603 | ||
604 | /* Called from copy_process() during fork */ | |
605 | void klp_copy_process(struct task_struct *child) | |
606 | { | |
607 | child->patch_state = current->patch_state; | |
608 | ||
609 | /* TIF_PATCH_PENDING gets copied in setup_thread_stack() */ | |
610 | } | |
43347d56 MB |
611 | |
612 | /* | |
613 | * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set. | |
614 | * Kthreads with TIF_PATCH_PENDING set are woken up. Only admin can request this | |
615 | * action currently. | |
616 | */ | |
617 | void klp_send_signals(void) | |
618 | { | |
619 | struct task_struct *g, *task; | |
620 | ||
621 | pr_notice("signaling remaining tasks\n"); | |
622 | ||
623 | read_lock(&tasklist_lock); | |
624 | for_each_process_thread(g, task) { | |
625 | if (!klp_patch_pending(task)) | |
626 | continue; | |
627 | ||
628 | /* | |
629 | * There is a small race here. We could see TIF_PATCH_PENDING | |
630 | * set and decide to wake up a kthread or send a fake signal. | |
631 | * Meanwhile the task could migrate itself and the action | |
632 | * would be meaningless. It is not serious though. | |
633 | */ | |
634 | if (task->flags & PF_KTHREAD) { | |
635 | /* | |
636 | * Wake up a kthread which sleeps interruptedly and | |
637 | * still has not been migrated. | |
638 | */ | |
639 | wake_up_state(task, TASK_INTERRUPTIBLE); | |
640 | } else { | |
641 | /* | |
642 | * Send fake signal to all non-kthread tasks which are | |
643 | * still not migrated. | |
644 | */ | |
645 | spin_lock_irq(&task->sighand->siglock); | |
646 | signal_wake_up(task, 0); | |
647 | spin_unlock_irq(&task->sighand->siglock); | |
648 | } | |
649 | } | |
650 | read_unlock(&tasklist_lock); | |
651 | } |