Commit | Line | Data |
---|---|---|
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 | ||
c99a2be7 MB |
36 | static bool klp_forced = false; |
37 | ||
d83a7cb3 JP |
38 | /* |
39 | * This work can be performed periodically to finish patching or unpatching any | |
40 | * "straggler" tasks which failed to transition in the first attempt. | |
41 | */ | |
42 | static void klp_transition_work_fn(struct work_struct *work) | |
43 | { | |
44 | mutex_lock(&klp_mutex); | |
45 | ||
46 | if (klp_transition_patch) | |
47 | klp_try_complete_transition(); | |
48 | ||
49 | mutex_unlock(&klp_mutex); | |
50 | } | |
51 | static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); | |
52 | ||
842c0884 PM |
53 | /* |
54 | * This function is just a stub to implement a hard force | |
55 | * of synchronize_sched(). This requires synchronizing | |
56 | * tasks even in userspace and idle. | |
57 | */ | |
58 | static void klp_sync(struct work_struct *work) | |
59 | { | |
60 | } | |
61 | ||
62 | /* | |
63 | * We allow to patch also functions where RCU is not watching, | |
64 | * e.g. before user_exit(). We can not rely on the RCU infrastructure | |
65 | * to do the synchronization. Instead hard force the sched synchronization. | |
66 | * | |
67 | * This approach allows to use RCU functions for manipulating func_stack | |
68 | * safely. | |
69 | */ | |
70 | static void klp_synchronize_transition(void) | |
71 | { | |
72 | schedule_on_each_cpu(klp_sync); | |
73 | } | |
74 | ||
d83a7cb3 JP |
75 | /* |
76 | * The transition to the target patch state is complete. Clean up the data | |
77 | * structures. | |
78 | */ | |
79 | static void klp_complete_transition(void) | |
80 | { | |
81 | struct klp_object *obj; | |
82 | struct klp_func *func; | |
83 | struct task_struct *g, *task; | |
84 | unsigned int cpu; | |
85 | ||
af026796 JL |
86 | pr_debug("'%s': completing %s transition\n", |
87 | klp_transition_patch->mod->name, | |
88 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
89 | ||
d83a7cb3 JP |
90 | if (klp_target_state == KLP_UNPATCHED) { |
91 | /* | |
92 | * All tasks have transitioned to KLP_UNPATCHED so we can now | |
93 | * remove the new functions from the func_stack. | |
94 | */ | |
95 | klp_unpatch_objects(klp_transition_patch); | |
96 | ||
97 | /* | |
98 | * Make sure klp_ftrace_handler() can no longer see functions | |
99 | * from this patch on the ops->func_stack. Otherwise, after | |
100 | * func->transition gets cleared, the handler may choose a | |
101 | * removed function. | |
102 | */ | |
842c0884 | 103 | klp_synchronize_transition(); |
d83a7cb3 JP |
104 | } |
105 | ||
d0807da7 MB |
106 | klp_for_each_object(klp_transition_patch, obj) |
107 | klp_for_each_func(obj, func) | |
d83a7cb3 | 108 | func->transition = false; |
3ec24776 | 109 | |
d83a7cb3 JP |
110 | /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ |
111 | if (klp_target_state == KLP_PATCHED) | |
842c0884 | 112 | klp_synchronize_transition(); |
d83a7cb3 JP |
113 | |
114 | read_lock(&tasklist_lock); | |
115 | for_each_process_thread(g, task) { | |
116 | WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); | |
117 | task->patch_state = KLP_UNDEFINED; | |
118 | } | |
119 | read_unlock(&tasklist_lock); | |
120 | ||
121 | for_each_possible_cpu(cpu) { | |
122 | task = idle_task(cpu); | |
123 | WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); | |
124 | task->patch_state = KLP_UNDEFINED; | |
125 | } | |
126 | ||
93862e38 JL |
127 | klp_for_each_object(klp_transition_patch, obj) { |
128 | if (!klp_is_object_loaded(obj)) | |
129 | continue; | |
130 | if (klp_target_state == KLP_PATCHED) | |
131 | klp_post_patch_callback(obj); | |
132 | else if (klp_target_state == KLP_UNPATCHED) | |
133 | klp_post_unpatch_callback(obj); | |
134 | } | |
135 | ||
6116c303 JL |
136 | pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, |
137 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
138 | ||
93862e38 | 139 | /* |
d0807da7 MB |
140 | * klp_forced set implies unbounded increase of module's ref count if |
141 | * the module is disabled/enabled in a loop. | |
93862e38 | 142 | */ |
d0807da7 | 143 | if (!klp_forced && klp_target_state == KLP_UNPATCHED) |
93862e38 | 144 | module_put(klp_transition_patch->mod); |
93862e38 | 145 | |
d83a7cb3 JP |
146 | klp_target_state = KLP_UNDEFINED; |
147 | klp_transition_patch = NULL; | |
148 | } | |
149 | ||
150 | /* | |
151 | * This is called in the error path, to cancel a transition before it has | |
152 | * started, i.e. klp_init_transition() has been called but | |
153 | * klp_start_transition() hasn't. If the transition *has* been started, | |
154 | * klp_reverse_transition() should be used instead. | |
155 | */ | |
156 | void klp_cancel_transition(void) | |
157 | { | |
3ec24776 JP |
158 | if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) |
159 | return; | |
160 | ||
af026796 JL |
161 | pr_debug("'%s': canceling patching transition, going to unpatch\n", |
162 | klp_transition_patch->mod->name); | |
163 | ||
3ec24776 | 164 | klp_target_state = KLP_UNPATCHED; |
d83a7cb3 JP |
165 | klp_complete_transition(); |
166 | } | |
167 | ||
168 | /* | |
169 | * Switch the patched state of the task to the set of functions in the target | |
170 | * patch state. | |
171 | * | |
172 | * NOTE: If task is not 'current', the caller must ensure the task is inactive. | |
173 | * Otherwise klp_ftrace_handler() might read the wrong 'patch_state' value. | |
174 | */ | |
175 | void klp_update_patch_state(struct task_struct *task) | |
176 | { | |
842c0884 PM |
177 | /* |
178 | * A variant of synchronize_sched() is used to allow patching functions | |
179 | * where RCU is not watching, see klp_synchronize_transition(). | |
180 | */ | |
181 | preempt_disable_notrace(); | |
d83a7cb3 JP |
182 | |
183 | /* | |
184 | * This test_and_clear_tsk_thread_flag() call also serves as a read | |
185 | * barrier (smp_rmb) for two cases: | |
186 | * | |
187 | * 1) Enforce the order of the TIF_PATCH_PENDING read and the | |
188 | * klp_target_state read. The corresponding write barrier is in | |
189 | * klp_init_transition(). | |
190 | * | |
191 | * 2) Enforce the order of the TIF_PATCH_PENDING read and a future read | |
192 | * of func->transition, if klp_ftrace_handler() is called later on | |
193 | * the same CPU. See __klp_disable_patch(). | |
194 | */ | |
195 | if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) | |
196 | task->patch_state = READ_ONCE(klp_target_state); | |
197 | ||
842c0884 | 198 | preempt_enable_notrace(); |
d83a7cb3 JP |
199 | } |
200 | ||
201 | /* | |
202 | * Determine whether the given stack trace includes any references to a | |
203 | * to-be-patched or to-be-unpatched function. | |
204 | */ | |
205 | static int klp_check_stack_func(struct klp_func *func, | |
206 | struct stack_trace *trace) | |
207 | { | |
208 | unsigned long func_addr, func_size, address; | |
209 | struct klp_ops *ops; | |
210 | int i; | |
211 | ||
d83a7cb3 JP |
212 | for (i = 0; i < trace->nr_entries; i++) { |
213 | address = trace->entries[i]; | |
214 | ||
215 | if (klp_target_state == KLP_UNPATCHED) { | |
216 | /* | |
217 | * Check for the to-be-unpatched function | |
218 | * (the func itself). | |
219 | */ | |
220 | func_addr = (unsigned long)func->new_func; | |
221 | func_size = func->new_size; | |
222 | } else { | |
223 | /* | |
224 | * Check for the to-be-patched function | |
225 | * (the previous func). | |
226 | */ | |
227 | ops = klp_find_ops(func->old_addr); | |
228 | ||
229 | if (list_is_singular(&ops->func_stack)) { | |
230 | /* original function */ | |
231 | func_addr = func->old_addr; | |
232 | func_size = func->old_size; | |
233 | } else { | |
234 | /* previously patched function */ | |
235 | struct klp_func *prev; | |
236 | ||
237 | prev = list_next_entry(func, stack_node); | |
238 | func_addr = (unsigned long)prev->new_func; | |
239 | func_size = prev->new_size; | |
240 | } | |
241 | } | |
242 | ||
243 | if (address >= func_addr && address < func_addr + func_size) | |
244 | return -EAGAIN; | |
245 | } | |
246 | ||
247 | return 0; | |
248 | } | |
249 | ||
250 | /* | |
251 | * Determine whether it's safe to transition the task to the target patch state | |
252 | * by looking for any to-be-patched or to-be-unpatched functions on its stack. | |
253 | */ | |
254 | static int klp_check_stack(struct task_struct *task, char *err_buf) | |
255 | { | |
256 | static unsigned long entries[MAX_STACK_ENTRIES]; | |
257 | struct stack_trace trace; | |
258 | struct klp_object *obj; | |
259 | struct klp_func *func; | |
260 | int ret; | |
261 | ||
262 | trace.skip = 0; | |
263 | trace.nr_entries = 0; | |
264 | trace.max_entries = MAX_STACK_ENTRIES; | |
265 | trace.entries = entries; | |
266 | ret = save_stack_trace_tsk_reliable(task, &trace); | |
267 | WARN_ON_ONCE(ret == -ENOSYS); | |
268 | if (ret) { | |
269 | snprintf(err_buf, STACK_ERR_BUF_SIZE, | |
270 | "%s: %s:%d has an unreliable stack\n", | |
271 | __func__, task->comm, task->pid); | |
272 | return ret; | |
273 | } | |
274 | ||
275 | klp_for_each_object(klp_transition_patch, obj) { | |
276 | if (!obj->patched) | |
277 | continue; | |
278 | klp_for_each_func(obj, func) { | |
279 | ret = klp_check_stack_func(func, &trace); | |
280 | if (ret) { | |
281 | snprintf(err_buf, STACK_ERR_BUF_SIZE, | |
282 | "%s: %s:%d is sleeping on function %s\n", | |
283 | __func__, task->comm, task->pid, | |
284 | func->old_name); | |
285 | return ret; | |
286 | } | |
287 | } | |
288 | } | |
289 | ||
290 | return 0; | |
291 | } | |
292 | ||
293 | /* | |
294 | * Try to safely switch a task to the target patch state. If it's currently | |
295 | * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or | |
296 | * if the stack is unreliable, return false. | |
297 | */ | |
298 | static bool klp_try_switch_task(struct task_struct *task) | |
299 | { | |
300 | struct rq *rq; | |
301 | struct rq_flags flags; | |
302 | int ret; | |
303 | bool success = false; | |
304 | char err_buf[STACK_ERR_BUF_SIZE]; | |
305 | ||
306 | err_buf[0] = '\0'; | |
307 | ||
308 | /* check if this task has already switched over */ | |
309 | if (task->patch_state == klp_target_state) | |
310 | return true; | |
311 | ||
d83a7cb3 JP |
312 | /* |
313 | * Now try to check the stack for any to-be-patched or to-be-unpatched | |
314 | * functions. If all goes well, switch the task to the target patch | |
315 | * state. | |
316 | */ | |
317 | rq = task_rq_lock(task, &flags); | |
318 | ||
319 | if (task_running(rq, task) && task != current) { | |
320 | snprintf(err_buf, STACK_ERR_BUF_SIZE, | |
321 | "%s: %s:%d is running\n", __func__, task->comm, | |
322 | task->pid); | |
323 | goto done; | |
324 | } | |
325 | ||
326 | ret = klp_check_stack(task, err_buf); | |
327 | if (ret) | |
328 | goto done; | |
329 | ||
330 | success = true; | |
331 | ||
332 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
333 | task->patch_state = klp_target_state; | |
334 | ||
335 | done: | |
336 | task_rq_unlock(rq, task, &flags); | |
337 | ||
338 | /* | |
339 | * Due to console deadlock issues, pr_debug() can't be used while | |
340 | * holding the task rq lock. Instead we have to use a temporary buffer | |
341 | * and print the debug message after releasing the lock. | |
342 | */ | |
343 | if (err_buf[0] != '\0') | |
344 | pr_debug("%s", err_buf); | |
345 | ||
346 | return success; | |
347 | ||
348 | } | |
349 | ||
350 | /* | |
351 | * Try to switch all remaining tasks to the target patch state by walking the | |
352 | * stacks of sleeping tasks and looking for any to-be-patched or | |
353 | * to-be-unpatched functions. If such functions are found, the task can't be | |
354 | * switched yet. | |
355 | * | |
356 | * If any tasks are still stuck in the initial patch state, schedule a retry. | |
357 | */ | |
358 | void klp_try_complete_transition(void) | |
359 | { | |
360 | unsigned int cpu; | |
361 | struct task_struct *g, *task; | |
362 | bool complete = true; | |
363 | ||
364 | WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); | |
365 | ||
d83a7cb3 JP |
366 | /* |
367 | * Try to switch the tasks to the target patch state by walking their | |
368 | * stacks and looking for any to-be-patched or to-be-unpatched | |
369 | * functions. If such functions are found on a stack, or if the stack | |
370 | * is deemed unreliable, the task can't be switched yet. | |
371 | * | |
372 | * Usually this will transition most (or all) of the tasks on a system | |
373 | * unless the patch includes changes to a very common function. | |
374 | */ | |
375 | read_lock(&tasklist_lock); | |
376 | for_each_process_thread(g, task) | |
377 | if (!klp_try_switch_task(task)) | |
378 | complete = false; | |
379 | read_unlock(&tasklist_lock); | |
380 | ||
381 | /* | |
382 | * Ditto for the idle "swapper" tasks. | |
383 | */ | |
384 | get_online_cpus(); | |
385 | for_each_possible_cpu(cpu) { | |
386 | task = idle_task(cpu); | |
387 | if (cpu_online(cpu)) { | |
388 | if (!klp_try_switch_task(task)) | |
389 | complete = false; | |
390 | } else if (task->patch_state != klp_target_state) { | |
391 | /* offline idle tasks can be switched immediately */ | |
392 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
393 | task->patch_state = klp_target_state; | |
394 | } | |
395 | } | |
396 | put_online_cpus(); | |
397 | ||
398 | if (!complete) { | |
399 | /* | |
400 | * Some tasks weren't able to be switched over. Try again | |
401 | * later and/or wait for other methods like kernel exit | |
402 | * switching. | |
403 | */ | |
404 | schedule_delayed_work(&klp_transition_work, | |
405 | round_jiffies_relative(HZ)); | |
406 | return; | |
407 | } | |
408 | ||
d83a7cb3 JP |
409 | /* we're done, now cleanup the data structures */ |
410 | klp_complete_transition(); | |
411 | } | |
412 | ||
413 | /* | |
414 | * Start the transition to the specified target patch state so tasks can begin | |
415 | * switching to it. | |
416 | */ | |
417 | void klp_start_transition(void) | |
418 | { | |
419 | struct task_struct *g, *task; | |
420 | unsigned int cpu; | |
421 | ||
422 | WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); | |
423 | ||
af026796 JL |
424 | pr_notice("'%s': starting %s transition\n", |
425 | klp_transition_patch->mod->name, | |
d83a7cb3 JP |
426 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); |
427 | ||
d83a7cb3 JP |
428 | /* |
429 | * Mark all normal tasks as needing a patch state update. They'll | |
430 | * switch either in klp_try_complete_transition() or as they exit the | |
431 | * kernel. | |
432 | */ | |
433 | read_lock(&tasklist_lock); | |
434 | for_each_process_thread(g, task) | |
435 | if (task->patch_state != klp_target_state) | |
436 | set_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
437 | read_unlock(&tasklist_lock); | |
438 | ||
439 | /* | |
440 | * Mark all idle tasks as needing a patch state update. They'll switch | |
441 | * either in klp_try_complete_transition() or at the idle loop switch | |
442 | * point. | |
443 | */ | |
444 | for_each_possible_cpu(cpu) { | |
445 | task = idle_task(cpu); | |
446 | if (task->patch_state != klp_target_state) | |
447 | set_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
448 | } | |
449 | } | |
450 | ||
451 | /* | |
452 | * Initialize the global target patch state and all tasks to the initial patch | |
453 | * state, and initialize all function transition states to true in preparation | |
454 | * for patching or unpatching. | |
455 | */ | |
456 | void klp_init_transition(struct klp_patch *patch, int state) | |
457 | { | |
458 | struct task_struct *g, *task; | |
459 | unsigned int cpu; | |
460 | struct klp_object *obj; | |
461 | struct klp_func *func; | |
462 | int initial_state = !state; | |
463 | ||
464 | WARN_ON_ONCE(klp_target_state != KLP_UNDEFINED); | |
465 | ||
466 | klp_transition_patch = patch; | |
467 | ||
468 | /* | |
469 | * Set the global target patch state which tasks will switch to. This | |
470 | * has no effect until the TIF_PATCH_PENDING flags get set later. | |
471 | */ | |
472 | klp_target_state = state; | |
473 | ||
af026796 JL |
474 | pr_debug("'%s': initializing %s transition\n", patch->mod->name, |
475 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
476 | ||
d83a7cb3 JP |
477 | /* |
478 | * Initialize all tasks to the initial patch state to prepare them for | |
479 | * switching to the target state. | |
480 | */ | |
481 | read_lock(&tasklist_lock); | |
482 | for_each_process_thread(g, task) { | |
483 | WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED); | |
484 | task->patch_state = initial_state; | |
485 | } | |
486 | read_unlock(&tasklist_lock); | |
487 | ||
488 | /* | |
489 | * Ditto for the idle "swapper" tasks. | |
490 | */ | |
491 | for_each_possible_cpu(cpu) { | |
492 | task = idle_task(cpu); | |
493 | WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED); | |
494 | task->patch_state = initial_state; | |
495 | } | |
496 | ||
497 | /* | |
498 | * Enforce the order of the task->patch_state initializations and the | |
499 | * func->transition updates to ensure that klp_ftrace_handler() doesn't | |
500 | * see a func in transition with a task->patch_state of KLP_UNDEFINED. | |
501 | * | |
502 | * Also enforce the order of the klp_target_state write and future | |
503 | * TIF_PATCH_PENDING writes to ensure klp_update_patch_state() doesn't | |
504 | * set a task->patch_state to KLP_UNDEFINED. | |
505 | */ | |
506 | smp_wmb(); | |
507 | ||
508 | /* | |
509 | * Set the func transition states so klp_ftrace_handler() will know to | |
510 | * switch to the transition logic. | |
511 | * | |
512 | * When patching, the funcs aren't yet in the func_stack and will be | |
513 | * made visible to the ftrace handler shortly by the calls to | |
514 | * klp_patch_object(). | |
515 | * | |
516 | * When unpatching, the funcs are already in the func_stack and so are | |
517 | * already visible to the ftrace handler. | |
518 | */ | |
519 | klp_for_each_object(patch, obj) | |
520 | klp_for_each_func(obj, func) | |
521 | func->transition = true; | |
522 | } | |
523 | ||
524 | /* | |
525 | * This function can be called in the middle of an existing transition to | |
526 | * reverse the direction of the target patch state. This can be done to | |
527 | * effectively cancel an existing enable or disable operation if there are any | |
528 | * tasks which are stuck in the initial patch state. | |
529 | */ | |
530 | void klp_reverse_transition(void) | |
531 | { | |
532 | unsigned int cpu; | |
533 | struct task_struct *g, *task; | |
534 | ||
af026796 JL |
535 | pr_debug("'%s': reversing transition from %s\n", |
536 | klp_transition_patch->mod->name, | |
537 | klp_target_state == KLP_PATCHED ? "patching to unpatching" : | |
538 | "unpatching to patching"); | |
539 | ||
d83a7cb3 JP |
540 | klp_transition_patch->enabled = !klp_transition_patch->enabled; |
541 | ||
542 | klp_target_state = !klp_target_state; | |
543 | ||
544 | /* | |
545 | * Clear all TIF_PATCH_PENDING flags to prevent races caused by | |
546 | * klp_update_patch_state() running in parallel with | |
547 | * klp_start_transition(). | |
548 | */ | |
549 | read_lock(&tasklist_lock); | |
550 | for_each_process_thread(g, task) | |
551 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
552 | read_unlock(&tasklist_lock); | |
553 | ||
554 | for_each_possible_cpu(cpu) | |
555 | clear_tsk_thread_flag(idle_task(cpu), TIF_PATCH_PENDING); | |
556 | ||
557 | /* Let any remaining calls to klp_update_patch_state() complete */ | |
842c0884 | 558 | klp_synchronize_transition(); |
d83a7cb3 JP |
559 | |
560 | klp_start_transition(); | |
561 | } | |
562 | ||
563 | /* Called from copy_process() during fork */ | |
564 | void klp_copy_process(struct task_struct *child) | |
565 | { | |
566 | child->patch_state = current->patch_state; | |
567 | ||
568 | /* TIF_PATCH_PENDING gets copied in setup_thread_stack() */ | |
569 | } | |
43347d56 MB |
570 | |
571 | /* | |
572 | * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set. | |
573 | * Kthreads with TIF_PATCH_PENDING set are woken up. Only admin can request this | |
574 | * action currently. | |
575 | */ | |
576 | void klp_send_signals(void) | |
577 | { | |
578 | struct task_struct *g, *task; | |
579 | ||
580 | pr_notice("signaling remaining tasks\n"); | |
581 | ||
582 | read_lock(&tasklist_lock); | |
583 | for_each_process_thread(g, task) { | |
584 | if (!klp_patch_pending(task)) | |
585 | continue; | |
586 | ||
587 | /* | |
588 | * There is a small race here. We could see TIF_PATCH_PENDING | |
589 | * set and decide to wake up a kthread or send a fake signal. | |
590 | * Meanwhile the task could migrate itself and the action | |
591 | * would be meaningless. It is not serious though. | |
592 | */ | |
593 | if (task->flags & PF_KTHREAD) { | |
594 | /* | |
595 | * Wake up a kthread which sleeps interruptedly and | |
596 | * still has not been migrated. | |
597 | */ | |
598 | wake_up_state(task, TASK_INTERRUPTIBLE); | |
599 | } else { | |
600 | /* | |
601 | * Send fake signal to all non-kthread tasks which are | |
602 | * still not migrated. | |
603 | */ | |
604 | spin_lock_irq(&task->sighand->siglock); | |
605 | signal_wake_up(task, 0); | |
606 | spin_unlock_irq(&task->sighand->siglock); | |
607 | } | |
608 | } | |
609 | read_unlock(&tasklist_lock); | |
610 | } | |
c99a2be7 MB |
611 | |
612 | /* | |
613 | * Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an | |
614 | * existing transition to finish. | |
615 | * | |
616 | * NOTE: klp_update_patch_state(task) requires the task to be inactive or | |
617 | * 'current'. This is not the case here and the consistency model could be | |
618 | * broken. Administrator, who is the only one to execute the | |
619 | * klp_force_transitions(), has to be aware of this. | |
620 | */ | |
621 | void klp_force_transition(void) | |
622 | { | |
623 | struct task_struct *g, *task; | |
624 | unsigned int cpu; | |
625 | ||
626 | pr_warn("forcing remaining tasks to the patched state\n"); | |
627 | ||
628 | read_lock(&tasklist_lock); | |
629 | for_each_process_thread(g, task) | |
630 | klp_update_patch_state(task); | |
631 | read_unlock(&tasklist_lock); | |
632 | ||
633 | for_each_possible_cpu(cpu) | |
634 | klp_update_patch_state(idle_task(cpu)); | |
635 | ||
636 | klp_forced = true; | |
637 | } |