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1ccea77e | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
d83a7cb3 JP |
2 | /* |
3 | * transition.c - Kernel Live Patching transition functions | |
4 | * | |
5 | * Copyright (C) 2015-2016 Josh Poimboeuf <jpoimboe@redhat.com> | |
d83a7cb3 JP |
6 | */ |
7 | ||
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
9 | ||
10 | #include <linux/cpu.h> | |
11 | #include <linux/stacktrace.h> | |
10517429 | 12 | #include "core.h" |
d83a7cb3 JP |
13 | #include "patch.h" |
14 | #include "transition.h" | |
d83a7cb3 JP |
15 | |
16 | #define MAX_STACK_ENTRIES 100 | |
17 | #define STACK_ERR_BUF_SIZE 128 | |
18 | ||
cba82dea MB |
19 | #define SIGNALS_TIMEOUT 15 |
20 | ||
d83a7cb3 JP |
21 | struct klp_patch *klp_transition_patch; |
22 | ||
23 | static int klp_target_state = KLP_UNDEFINED; | |
24 | ||
cba82dea MB |
25 | static unsigned int klp_signals_cnt; |
26 | ||
d83a7cb3 JP |
27 | /* |
28 | * This work can be performed periodically to finish patching or unpatching any | |
29 | * "straggler" tasks which failed to transition in the first attempt. | |
30 | */ | |
31 | static void klp_transition_work_fn(struct work_struct *work) | |
32 | { | |
33 | mutex_lock(&klp_mutex); | |
34 | ||
35 | if (klp_transition_patch) | |
36 | klp_try_complete_transition(); | |
37 | ||
38 | mutex_unlock(&klp_mutex); | |
39 | } | |
40 | static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); | |
41 | ||
842c0884 PM |
42 | /* |
43 | * This function is just a stub to implement a hard force | |
6932689e | 44 | * of synchronize_rcu(). This requires synchronizing |
842c0884 PM |
45 | * tasks even in userspace and idle. |
46 | */ | |
47 | static void klp_sync(struct work_struct *work) | |
48 | { | |
49 | } | |
50 | ||
51 | /* | |
52 | * We allow to patch also functions where RCU is not watching, | |
53 | * e.g. before user_exit(). We can not rely on the RCU infrastructure | |
54 | * to do the synchronization. Instead hard force the sched synchronization. | |
55 | * | |
56 | * This approach allows to use RCU functions for manipulating func_stack | |
57 | * safely. | |
58 | */ | |
59 | static void klp_synchronize_transition(void) | |
60 | { | |
61 | schedule_on_each_cpu(klp_sync); | |
62 | } | |
63 | ||
d83a7cb3 JP |
64 | /* |
65 | * The transition to the target patch state is complete. Clean up the data | |
66 | * structures. | |
67 | */ | |
68 | static void klp_complete_transition(void) | |
69 | { | |
70 | struct klp_object *obj; | |
71 | struct klp_func *func; | |
72 | struct task_struct *g, *task; | |
73 | unsigned int cpu; | |
74 | ||
af026796 JL |
75 | pr_debug("'%s': completing %s transition\n", |
76 | klp_transition_patch->mod->name, | |
77 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
78 | ||
d697bad5 | 79 | if (klp_transition_patch->replace && klp_target_state == KLP_PATCHED) { |
7e35e4eb | 80 | klp_unpatch_replaced_patches(klp_transition_patch); |
d697bad5 PM |
81 | klp_discard_nops(klp_transition_patch); |
82 | } | |
e1452b60 | 83 | |
d83a7cb3 JP |
84 | if (klp_target_state == KLP_UNPATCHED) { |
85 | /* | |
86 | * All tasks have transitioned to KLP_UNPATCHED so we can now | |
87 | * remove the new functions from the func_stack. | |
88 | */ | |
89 | klp_unpatch_objects(klp_transition_patch); | |
90 | ||
91 | /* | |
92 | * Make sure klp_ftrace_handler() can no longer see functions | |
93 | * from this patch on the ops->func_stack. Otherwise, after | |
94 | * func->transition gets cleared, the handler may choose a | |
95 | * removed function. | |
96 | */ | |
842c0884 | 97 | klp_synchronize_transition(); |
d83a7cb3 JP |
98 | } |
99 | ||
d0807da7 MB |
100 | klp_for_each_object(klp_transition_patch, obj) |
101 | klp_for_each_func(obj, func) | |
d83a7cb3 | 102 | func->transition = false; |
3ec24776 | 103 | |
d83a7cb3 JP |
104 | /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ |
105 | if (klp_target_state == KLP_PATCHED) | |
842c0884 | 106 | klp_synchronize_transition(); |
d83a7cb3 JP |
107 | |
108 | read_lock(&tasklist_lock); | |
109 | for_each_process_thread(g, task) { | |
110 | WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); | |
111 | task->patch_state = KLP_UNDEFINED; | |
112 | } | |
113 | read_unlock(&tasklist_lock); | |
114 | ||
115 | for_each_possible_cpu(cpu) { | |
116 | task = idle_task(cpu); | |
117 | WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); | |
118 | task->patch_state = KLP_UNDEFINED; | |
119 | } | |
120 | ||
93862e38 JL |
121 | klp_for_each_object(klp_transition_patch, obj) { |
122 | if (!klp_is_object_loaded(obj)) | |
123 | continue; | |
124 | if (klp_target_state == KLP_PATCHED) | |
125 | klp_post_patch_callback(obj); | |
126 | else if (klp_target_state == KLP_UNPATCHED) | |
127 | klp_post_unpatch_callback(obj); | |
128 | } | |
129 | ||
6116c303 JL |
130 | pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, |
131 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
132 | ||
d83a7cb3 JP |
133 | klp_target_state = KLP_UNDEFINED; |
134 | klp_transition_patch = NULL; | |
135 | } | |
136 | ||
137 | /* | |
138 | * This is called in the error path, to cancel a transition before it has | |
139 | * started, i.e. klp_init_transition() has been called but | |
140 | * klp_start_transition() hasn't. If the transition *has* been started, | |
141 | * klp_reverse_transition() should be used instead. | |
142 | */ | |
143 | void klp_cancel_transition(void) | |
144 | { | |
3ec24776 JP |
145 | if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) |
146 | return; | |
147 | ||
af026796 JL |
148 | pr_debug("'%s': canceling patching transition, going to unpatch\n", |
149 | klp_transition_patch->mod->name); | |
150 | ||
3ec24776 | 151 | klp_target_state = KLP_UNPATCHED; |
d83a7cb3 JP |
152 | klp_complete_transition(); |
153 | } | |
154 | ||
155 | /* | |
156 | * Switch the patched state of the task to the set of functions in the target | |
157 | * patch state. | |
158 | * | |
159 | * NOTE: If task is not 'current', the caller must ensure the task is inactive. | |
160 | * Otherwise klp_ftrace_handler() might read the wrong 'patch_state' value. | |
161 | */ | |
162 | void klp_update_patch_state(struct task_struct *task) | |
163 | { | |
842c0884 | 164 | /* |
6932689e | 165 | * A variant of synchronize_rcu() is used to allow patching functions |
842c0884 PM |
166 | * where RCU is not watching, see klp_synchronize_transition(). |
167 | */ | |
168 | preempt_disable_notrace(); | |
d83a7cb3 JP |
169 | |
170 | /* | |
171 | * This test_and_clear_tsk_thread_flag() call also serves as a read | |
172 | * barrier (smp_rmb) for two cases: | |
173 | * | |
174 | * 1) Enforce the order of the TIF_PATCH_PENDING read and the | |
175 | * klp_target_state read. The corresponding write barrier is in | |
176 | * klp_init_transition(). | |
177 | * | |
178 | * 2) Enforce the order of the TIF_PATCH_PENDING read and a future read | |
179 | * of func->transition, if klp_ftrace_handler() is called later on | |
180 | * the same CPU. See __klp_disable_patch(). | |
181 | */ | |
182 | if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) | |
183 | task->patch_state = READ_ONCE(klp_target_state); | |
184 | ||
842c0884 | 185 | preempt_enable_notrace(); |
d83a7cb3 JP |
186 | } |
187 | ||
188 | /* | |
189 | * Determine whether the given stack trace includes any references to a | |
190 | * to-be-patched or to-be-unpatched function. | |
191 | */ | |
25e39e32 TG |
192 | static int klp_check_stack_func(struct klp_func *func, unsigned long *entries, |
193 | unsigned int nr_entries) | |
d83a7cb3 JP |
194 | { |
195 | unsigned long func_addr, func_size, address; | |
196 | struct klp_ops *ops; | |
197 | int i; | |
198 | ||
25e39e32 TG |
199 | for (i = 0; i < nr_entries; i++) { |
200 | address = entries[i]; | |
d83a7cb3 JP |
201 | |
202 | if (klp_target_state == KLP_UNPATCHED) { | |
203 | /* | |
204 | * Check for the to-be-unpatched function | |
205 | * (the func itself). | |
206 | */ | |
207 | func_addr = (unsigned long)func->new_func; | |
208 | func_size = func->new_size; | |
209 | } else { | |
210 | /* | |
211 | * Check for the to-be-patched function | |
212 | * (the previous func). | |
213 | */ | |
19514910 | 214 | ops = klp_find_ops(func->old_func); |
d83a7cb3 JP |
215 | |
216 | if (list_is_singular(&ops->func_stack)) { | |
217 | /* original function */ | |
19514910 | 218 | func_addr = (unsigned long)func->old_func; |
d83a7cb3 JP |
219 | func_size = func->old_size; |
220 | } else { | |
221 | /* previously patched function */ | |
222 | struct klp_func *prev; | |
223 | ||
224 | prev = list_next_entry(func, stack_node); | |
225 | func_addr = (unsigned long)prev->new_func; | |
226 | func_size = prev->new_size; | |
227 | } | |
228 | } | |
229 | ||
230 | if (address >= func_addr && address < func_addr + func_size) | |
231 | return -EAGAIN; | |
232 | } | |
233 | ||
234 | return 0; | |
235 | } | |
236 | ||
237 | /* | |
238 | * Determine whether it's safe to transition the task to the target patch state | |
239 | * by looking for any to-be-patched or to-be-unpatched functions on its stack. | |
240 | */ | |
00619f7c | 241 | static int klp_check_stack(struct task_struct *task, const char **oldname) |
d83a7cb3 JP |
242 | { |
243 | static unsigned long entries[MAX_STACK_ENTRIES]; | |
d83a7cb3 JP |
244 | struct klp_object *obj; |
245 | struct klp_func *func; | |
25e39e32 | 246 | int ret, nr_entries; |
d83a7cb3 | 247 | |
25e39e32 | 248 | ret = stack_trace_save_tsk_reliable(task, entries, ARRAY_SIZE(entries)); |
00619f7c PZ |
249 | if (ret < 0) |
250 | return -EINVAL; | |
25e39e32 | 251 | nr_entries = ret; |
d83a7cb3 JP |
252 | |
253 | klp_for_each_object(klp_transition_patch, obj) { | |
254 | if (!obj->patched) | |
255 | continue; | |
256 | klp_for_each_func(obj, func) { | |
25e39e32 | 257 | ret = klp_check_stack_func(func, entries, nr_entries); |
d83a7cb3 | 258 | if (ret) { |
00619f7c PZ |
259 | *oldname = func->old_name; |
260 | return -EADDRINUSE; | |
d83a7cb3 JP |
261 | } |
262 | } | |
263 | } | |
264 | ||
265 | return 0; | |
266 | } | |
267 | ||
00619f7c PZ |
268 | static int klp_check_and_switch_task(struct task_struct *task, void *arg) |
269 | { | |
270 | int ret; | |
271 | ||
272 | if (task_curr(task) && task != current) | |
273 | return -EBUSY; | |
274 | ||
275 | ret = klp_check_stack(task, arg); | |
276 | if (ret) | |
277 | return ret; | |
278 | ||
279 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
280 | task->patch_state = klp_target_state; | |
281 | return 0; | |
282 | } | |
283 | ||
d83a7cb3 JP |
284 | /* |
285 | * Try to safely switch a task to the target patch state. If it's currently | |
286 | * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or | |
287 | * if the stack is unreliable, return false. | |
288 | */ | |
289 | static bool klp_try_switch_task(struct task_struct *task) | |
290 | { | |
00619f7c | 291 | const char *old_name; |
d83a7cb3 | 292 | int ret; |
d83a7cb3 JP |
293 | |
294 | /* check if this task has already switched over */ | |
295 | if (task->patch_state == klp_target_state) | |
296 | return true; | |
297 | ||
67059d65 MB |
298 | /* |
299 | * For arches which don't have reliable stack traces, we have to rely | |
300 | * on other methods (e.g., switching tasks at kernel exit). | |
301 | */ | |
302 | if (!klp_have_reliable_stack()) | |
303 | return false; | |
304 | ||
d83a7cb3 JP |
305 | /* |
306 | * Now try to check the stack for any to-be-patched or to-be-unpatched | |
307 | * functions. If all goes well, switch the task to the target patch | |
308 | * state. | |
309 | */ | |
00619f7c PZ |
310 | ret = task_call_func(task, klp_check_and_switch_task, &old_name); |
311 | switch (ret) { | |
312 | case 0: /* success */ | |
313 | break; | |
d83a7cb3 | 314 | |
00619f7c PZ |
315 | case -EBUSY: /* klp_check_and_switch_task() */ |
316 | pr_debug("%s: %s:%d is running\n", | |
317 | __func__, task->comm, task->pid); | |
318 | break; | |
319 | case -EINVAL: /* klp_check_and_switch_task() */ | |
320 | pr_debug("%s: %s:%d has an unreliable stack\n", | |
321 | __func__, task->comm, task->pid); | |
322 | break; | |
323 | case -EADDRINUSE: /* klp_check_and_switch_task() */ | |
324 | pr_debug("%s: %s:%d is sleeping on function %s\n", | |
325 | __func__, task->comm, task->pid, old_name); | |
326 | break; | |
327 | ||
328 | default: | |
329 | pr_debug("%s: Unknown error code (%d) when trying to switch %s:%d\n", | |
330 | __func__, ret, task->comm, task->pid); | |
331 | break; | |
d83a7cb3 JP |
332 | } |
333 | ||
00619f7c | 334 | return !ret; |
d83a7cb3 JP |
335 | } |
336 | ||
0b3d5279 MB |
337 | /* |
338 | * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set. | |
339 | * Kthreads with TIF_PATCH_PENDING set are woken up. | |
340 | */ | |
341 | static void klp_send_signals(void) | |
342 | { | |
343 | struct task_struct *g, *task; | |
344 | ||
345 | if (klp_signals_cnt == SIGNALS_TIMEOUT) | |
346 | pr_notice("signaling remaining tasks\n"); | |
347 | ||
348 | read_lock(&tasklist_lock); | |
349 | for_each_process_thread(g, task) { | |
350 | if (!klp_patch_pending(task)) | |
351 | continue; | |
352 | ||
353 | /* | |
354 | * There is a small race here. We could see TIF_PATCH_PENDING | |
355 | * set and decide to wake up a kthread or send a fake signal. | |
356 | * Meanwhile the task could migrate itself and the action | |
357 | * would be meaningless. It is not serious though. | |
358 | */ | |
359 | if (task->flags & PF_KTHREAD) { | |
360 | /* | |
361 | * Wake up a kthread which sleeps interruptedly and | |
362 | * still has not been migrated. | |
363 | */ | |
364 | wake_up_state(task, TASK_INTERRUPTIBLE); | |
365 | } else { | |
366 | /* | |
367 | * Send fake signal to all non-kthread tasks which are | |
368 | * still not migrated. | |
369 | */ | |
8df1947c | 370 | set_notify_signal(task); |
0b3d5279 MB |
371 | } |
372 | } | |
373 | read_unlock(&tasklist_lock); | |
374 | } | |
375 | ||
d83a7cb3 JP |
376 | /* |
377 | * Try to switch all remaining tasks to the target patch state by walking the | |
378 | * stacks of sleeping tasks and looking for any to-be-patched or | |
379 | * to-be-unpatched functions. If such functions are found, the task can't be | |
380 | * switched yet. | |
381 | * | |
382 | * If any tasks are still stuck in the initial patch state, schedule a retry. | |
383 | */ | |
384 | void klp_try_complete_transition(void) | |
385 | { | |
386 | unsigned int cpu; | |
387 | struct task_struct *g, *task; | |
958ef1e3 | 388 | struct klp_patch *patch; |
d83a7cb3 JP |
389 | bool complete = true; |
390 | ||
391 | WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); | |
392 | ||
d83a7cb3 JP |
393 | /* |
394 | * Try to switch the tasks to the target patch state by walking their | |
395 | * stacks and looking for any to-be-patched or to-be-unpatched | |
396 | * functions. If such functions are found on a stack, or if the stack | |
397 | * is deemed unreliable, the task can't be switched yet. | |
398 | * | |
399 | * Usually this will transition most (or all) of the tasks on a system | |
400 | * unless the patch includes changes to a very common function. | |
401 | */ | |
402 | read_lock(&tasklist_lock); | |
403 | for_each_process_thread(g, task) | |
404 | if (!klp_try_switch_task(task)) | |
405 | complete = false; | |
406 | read_unlock(&tasklist_lock); | |
407 | ||
408 | /* | |
409 | * Ditto for the idle "swapper" tasks. | |
410 | */ | |
1daf08a0 | 411 | cpus_read_lock(); |
d83a7cb3 JP |
412 | for_each_possible_cpu(cpu) { |
413 | task = idle_task(cpu); | |
414 | if (cpu_online(cpu)) { | |
5de62ea8 | 415 | if (!klp_try_switch_task(task)) { |
d83a7cb3 | 416 | complete = false; |
5de62ea8 PZ |
417 | /* Make idle task go through the main loop. */ |
418 | wake_up_if_idle(cpu); | |
419 | } | |
d83a7cb3 JP |
420 | } else if (task->patch_state != klp_target_state) { |
421 | /* offline idle tasks can be switched immediately */ | |
422 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
423 | task->patch_state = klp_target_state; | |
424 | } | |
425 | } | |
1daf08a0 | 426 | cpus_read_unlock(); |
d83a7cb3 JP |
427 | |
428 | if (!complete) { | |
cba82dea MB |
429 | if (klp_signals_cnt && !(klp_signals_cnt % SIGNALS_TIMEOUT)) |
430 | klp_send_signals(); | |
431 | klp_signals_cnt++; | |
432 | ||
d83a7cb3 JP |
433 | /* |
434 | * Some tasks weren't able to be switched over. Try again | |
435 | * later and/or wait for other methods like kernel exit | |
436 | * switching. | |
437 | */ | |
438 | schedule_delayed_work(&klp_transition_work, | |
439 | round_jiffies_relative(HZ)); | |
440 | return; | |
441 | } | |
442 | ||
d83a7cb3 | 443 | /* we're done, now cleanup the data structures */ |
958ef1e3 | 444 | patch = klp_transition_patch; |
d83a7cb3 | 445 | klp_complete_transition(); |
958ef1e3 PM |
446 | |
447 | /* | |
7e35e4eb | 448 | * It would make more sense to free the unused patches in |
958ef1e3 PM |
449 | * klp_complete_transition() but it is called also |
450 | * from klp_cancel_transition(). | |
451 | */ | |
7e35e4eb PM |
452 | if (!patch->enabled) |
453 | klp_free_patch_async(patch); | |
454 | else if (patch->replace) | |
455 | klp_free_replaced_patches_async(patch); | |
d83a7cb3 JP |
456 | } |
457 | ||
458 | /* | |
459 | * Start the transition to the specified target patch state so tasks can begin | |
460 | * switching to it. | |
461 | */ | |
462 | void klp_start_transition(void) | |
463 | { | |
464 | struct task_struct *g, *task; | |
465 | unsigned int cpu; | |
466 | ||
467 | WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); | |
468 | ||
af026796 JL |
469 | pr_notice("'%s': starting %s transition\n", |
470 | klp_transition_patch->mod->name, | |
d83a7cb3 JP |
471 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); |
472 | ||
d83a7cb3 JP |
473 | /* |
474 | * Mark all normal tasks as needing a patch state update. They'll | |
475 | * switch either in klp_try_complete_transition() or as they exit the | |
476 | * kernel. | |
477 | */ | |
478 | read_lock(&tasklist_lock); | |
479 | for_each_process_thread(g, task) | |
480 | if (task->patch_state != klp_target_state) | |
481 | set_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
482 | read_unlock(&tasklist_lock); | |
483 | ||
484 | /* | |
485 | * Mark all idle tasks as needing a patch state update. They'll switch | |
486 | * either in klp_try_complete_transition() or at the idle loop switch | |
487 | * point. | |
488 | */ | |
489 | for_each_possible_cpu(cpu) { | |
490 | task = idle_task(cpu); | |
491 | if (task->patch_state != klp_target_state) | |
492 | set_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
493 | } | |
cba82dea MB |
494 | |
495 | klp_signals_cnt = 0; | |
d83a7cb3 JP |
496 | } |
497 | ||
498 | /* | |
499 | * Initialize the global target patch state and all tasks to the initial patch | |
500 | * state, and initialize all function transition states to true in preparation | |
501 | * for patching or unpatching. | |
502 | */ | |
503 | void klp_init_transition(struct klp_patch *patch, int state) | |
504 | { | |
505 | struct task_struct *g, *task; | |
506 | unsigned int cpu; | |
507 | struct klp_object *obj; | |
508 | struct klp_func *func; | |
509 | int initial_state = !state; | |
510 | ||
511 | WARN_ON_ONCE(klp_target_state != KLP_UNDEFINED); | |
512 | ||
513 | klp_transition_patch = patch; | |
514 | ||
515 | /* | |
516 | * Set the global target patch state which tasks will switch to. This | |
517 | * has no effect until the TIF_PATCH_PENDING flags get set later. | |
518 | */ | |
519 | klp_target_state = state; | |
520 | ||
af026796 JL |
521 | pr_debug("'%s': initializing %s transition\n", patch->mod->name, |
522 | klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); | |
523 | ||
d83a7cb3 JP |
524 | /* |
525 | * Initialize all tasks to the initial patch state to prepare them for | |
526 | * switching to the target state. | |
527 | */ | |
528 | read_lock(&tasklist_lock); | |
529 | for_each_process_thread(g, task) { | |
530 | WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED); | |
531 | task->patch_state = initial_state; | |
532 | } | |
533 | read_unlock(&tasklist_lock); | |
534 | ||
535 | /* | |
536 | * Ditto for the idle "swapper" tasks. | |
537 | */ | |
538 | for_each_possible_cpu(cpu) { | |
539 | task = idle_task(cpu); | |
540 | WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED); | |
541 | task->patch_state = initial_state; | |
542 | } | |
543 | ||
544 | /* | |
545 | * Enforce the order of the task->patch_state initializations and the | |
546 | * func->transition updates to ensure that klp_ftrace_handler() doesn't | |
547 | * see a func in transition with a task->patch_state of KLP_UNDEFINED. | |
548 | * | |
549 | * Also enforce the order of the klp_target_state write and future | |
550 | * TIF_PATCH_PENDING writes to ensure klp_update_patch_state() doesn't | |
551 | * set a task->patch_state to KLP_UNDEFINED. | |
552 | */ | |
553 | smp_wmb(); | |
554 | ||
555 | /* | |
556 | * Set the func transition states so klp_ftrace_handler() will know to | |
557 | * switch to the transition logic. | |
558 | * | |
559 | * When patching, the funcs aren't yet in the func_stack and will be | |
560 | * made visible to the ftrace handler shortly by the calls to | |
561 | * klp_patch_object(). | |
562 | * | |
563 | * When unpatching, the funcs are already in the func_stack and so are | |
564 | * already visible to the ftrace handler. | |
565 | */ | |
566 | klp_for_each_object(patch, obj) | |
567 | klp_for_each_func(obj, func) | |
568 | func->transition = true; | |
569 | } | |
570 | ||
571 | /* | |
572 | * This function can be called in the middle of an existing transition to | |
573 | * reverse the direction of the target patch state. This can be done to | |
574 | * effectively cancel an existing enable or disable operation if there are any | |
575 | * tasks which are stuck in the initial patch state. | |
576 | */ | |
577 | void klp_reverse_transition(void) | |
578 | { | |
579 | unsigned int cpu; | |
580 | struct task_struct *g, *task; | |
581 | ||
af026796 JL |
582 | pr_debug("'%s': reversing transition from %s\n", |
583 | klp_transition_patch->mod->name, | |
584 | klp_target_state == KLP_PATCHED ? "patching to unpatching" : | |
585 | "unpatching to patching"); | |
586 | ||
d83a7cb3 JP |
587 | klp_transition_patch->enabled = !klp_transition_patch->enabled; |
588 | ||
589 | klp_target_state = !klp_target_state; | |
590 | ||
591 | /* | |
592 | * Clear all TIF_PATCH_PENDING flags to prevent races caused by | |
593 | * klp_update_patch_state() running in parallel with | |
594 | * klp_start_transition(). | |
595 | */ | |
596 | read_lock(&tasklist_lock); | |
597 | for_each_process_thread(g, task) | |
598 | clear_tsk_thread_flag(task, TIF_PATCH_PENDING); | |
599 | read_unlock(&tasklist_lock); | |
600 | ||
601 | for_each_possible_cpu(cpu) | |
602 | clear_tsk_thread_flag(idle_task(cpu), TIF_PATCH_PENDING); | |
603 | ||
604 | /* Let any remaining calls to klp_update_patch_state() complete */ | |
842c0884 | 605 | klp_synchronize_transition(); |
d83a7cb3 JP |
606 | |
607 | klp_start_transition(); | |
608 | } | |
609 | ||
610 | /* Called from copy_process() during fork */ | |
611 | void klp_copy_process(struct task_struct *child) | |
612 | { | |
d83a7cb3 | 613 | |
747f7a29 RR |
614 | /* |
615 | * The parent process may have gone through a KLP transition since | |
616 | * the thread flag was copied in setup_thread_stack earlier. Bring | |
617 | * the task flag up to date with the parent here. | |
618 | * | |
619 | * The operation is serialized against all klp_*_transition() | |
620 | * operations by the tasklist_lock. The only exception is | |
621 | * klp_update_patch_state(current), but we cannot race with | |
622 | * that because we are current. | |
623 | */ | |
624 | if (test_tsk_thread_flag(current, TIF_PATCH_PENDING)) | |
625 | set_tsk_thread_flag(child, TIF_PATCH_PENDING); | |
626 | else | |
627 | clear_tsk_thread_flag(child, TIF_PATCH_PENDING); | |
628 | ||
629 | child->patch_state = current->patch_state; | |
d83a7cb3 | 630 | } |
43347d56 | 631 | |
c99a2be7 MB |
632 | /* |
633 | * Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an | |
634 | * existing transition to finish. | |
635 | * | |
636 | * NOTE: klp_update_patch_state(task) requires the task to be inactive or | |
637 | * 'current'. This is not the case here and the consistency model could be | |
638 | * broken. Administrator, who is the only one to execute the | |
639 | * klp_force_transitions(), has to be aware of this. | |
640 | */ | |
641 | void klp_force_transition(void) | |
642 | { | |
68007289 | 643 | struct klp_patch *patch; |
c99a2be7 MB |
644 | struct task_struct *g, *task; |
645 | unsigned int cpu; | |
646 | ||
647 | pr_warn("forcing remaining tasks to the patched state\n"); | |
648 | ||
649 | read_lock(&tasklist_lock); | |
650 | for_each_process_thread(g, task) | |
651 | klp_update_patch_state(task); | |
652 | read_unlock(&tasklist_lock); | |
653 | ||
654 | for_each_possible_cpu(cpu) | |
655 | klp_update_patch_state(idle_task(cpu)); | |
656 | ||
29573083 CZ |
657 | /* Set forced flag for patches being removed. */ |
658 | if (klp_target_state == KLP_UNPATCHED) | |
659 | klp_transition_patch->forced = true; | |
660 | else if (klp_transition_patch->replace) { | |
661 | klp_for_each_patch(patch) { | |
662 | if (patch != klp_transition_patch) | |
663 | patch->forced = true; | |
664 | } | |
665 | } | |
c99a2be7 | 666 | } |