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1 | /* | |
2 | * linux/kernel/exit.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | */ | |
6 | ||
7 | #include <linux/mm.h> | |
8 | #include <linux/slab.h> | |
9 | #include <linux/sched/autogroup.h> | |
10 | #include <linux/sched/mm.h> | |
11 | #include <linux/sched/stat.h> | |
12 | #include <linux/sched/task.h> | |
13 | #include <linux/sched/task_stack.h> | |
14 | #include <linux/sched/cputime.h> | |
15 | #include <linux/interrupt.h> | |
16 | #include <linux/module.h> | |
17 | #include <linux/capability.h> | |
18 | #include <linux/completion.h> | |
19 | #include <linux/personality.h> | |
20 | #include <linux/tty.h> | |
21 | #include <linux/iocontext.h> | |
22 | #include <linux/key.h> | |
23 | #include <linux/cpu.h> | |
24 | #include <linux/acct.h> | |
25 | #include <linux/tsacct_kern.h> | |
26 | #include <linux/file.h> | |
27 | #include <linux/fdtable.h> | |
28 | #include <linux/freezer.h> | |
29 | #include <linux/binfmts.h> | |
30 | #include <linux/nsproxy.h> | |
31 | #include <linux/pid_namespace.h> | |
32 | #include <linux/ptrace.h> | |
33 | #include <linux/profile.h> | |
34 | #include <linux/mount.h> | |
35 | #include <linux/proc_fs.h> | |
36 | #include <linux/kthread.h> | |
37 | #include <linux/mempolicy.h> | |
38 | #include <linux/taskstats_kern.h> | |
39 | #include <linux/delayacct.h> | |
40 | #include <linux/cgroup.h> | |
41 | #include <linux/syscalls.h> | |
42 | #include <linux/signal.h> | |
43 | #include <linux/posix-timers.h> | |
44 | #include <linux/cn_proc.h> | |
45 | #include <linux/mutex.h> | |
46 | #include <linux/futex.h> | |
47 | #include <linux/pipe_fs_i.h> | |
48 | #include <linux/audit.h> /* for audit_free() */ | |
49 | #include <linux/resource.h> | |
50 | #include <linux/blkdev.h> | |
51 | #include <linux/task_io_accounting_ops.h> | |
52 | #include <linux/tracehook.h> | |
53 | #include <linux/fs_struct.h> | |
54 | #include <linux/init_task.h> | |
55 | #include <linux/perf_event.h> | |
56 | #include <trace/events/sched.h> | |
57 | #include <linux/hw_breakpoint.h> | |
58 | #include <linux/oom.h> | |
59 | #include <linux/writeback.h> | |
60 | #include <linux/shm.h> | |
61 | #include <linux/kcov.h> | |
62 | #include <linux/random.h> | |
63 | #include <linux/rcuwait.h> | |
64 | #include <linux/compat.h> | |
65 | ||
66 | #include <linux/uaccess.h> | |
67 | #include <asm/unistd.h> | |
68 | #include <asm/pgtable.h> | |
69 | #include <asm/mmu_context.h> | |
70 | ||
71 | static void __unhash_process(struct task_struct *p, bool group_dead) | |
72 | { | |
73 | nr_threads--; | |
74 | detach_pid(p, PIDTYPE_PID); | |
75 | if (group_dead) { | |
76 | detach_pid(p, PIDTYPE_TGID); | |
77 | detach_pid(p, PIDTYPE_PGID); | |
78 | detach_pid(p, PIDTYPE_SID); | |
79 | ||
80 | list_del_rcu(&p->tasks); | |
81 | list_del_init(&p->sibling); | |
82 | __this_cpu_dec(process_counts); | |
83 | } | |
84 | list_del_rcu(&p->thread_group); | |
85 | list_del_rcu(&p->thread_node); | |
86 | } | |
87 | ||
88 | /* | |
89 | * This function expects the tasklist_lock write-locked. | |
90 | */ | |
91 | static void __exit_signal(struct task_struct *tsk) | |
92 | { | |
93 | struct signal_struct *sig = tsk->signal; | |
94 | bool group_dead = thread_group_leader(tsk); | |
95 | struct sighand_struct *sighand; | |
96 | struct tty_struct *uninitialized_var(tty); | |
97 | u64 utime, stime; | |
98 | ||
99 | sighand = rcu_dereference_check(tsk->sighand, | |
100 | lockdep_tasklist_lock_is_held()); | |
101 | spin_lock(&sighand->siglock); | |
102 | ||
103 | #ifdef CONFIG_POSIX_TIMERS | |
104 | posix_cpu_timers_exit(tsk); | |
105 | if (group_dead) { | |
106 | posix_cpu_timers_exit_group(tsk); | |
107 | } else { | |
108 | /* | |
109 | * This can only happen if the caller is de_thread(). | |
110 | * FIXME: this is the temporary hack, we should teach | |
111 | * posix-cpu-timers to handle this case correctly. | |
112 | */ | |
113 | if (unlikely(has_group_leader_pid(tsk))) | |
114 | posix_cpu_timers_exit_group(tsk); | |
115 | } | |
116 | #endif | |
117 | ||
118 | if (group_dead) { | |
119 | tty = sig->tty; | |
120 | sig->tty = NULL; | |
121 | } else { | |
122 | /* | |
123 | * If there is any task waiting for the group exit | |
124 | * then notify it: | |
125 | */ | |
126 | if (sig->notify_count > 0 && !--sig->notify_count) | |
127 | wake_up_process(sig->group_exit_task); | |
128 | ||
129 | if (tsk == sig->curr_target) | |
130 | sig->curr_target = next_thread(tsk); | |
131 | } | |
132 | ||
133 | add_device_randomness((const void*) &tsk->se.sum_exec_runtime, | |
134 | sizeof(unsigned long long)); | |
135 | ||
136 | /* | |
137 | * Accumulate here the counters for all threads as they die. We could | |
138 | * skip the group leader because it is the last user of signal_struct, | |
139 | * but we want to avoid the race with thread_group_cputime() which can | |
140 | * see the empty ->thread_head list. | |
141 | */ | |
142 | task_cputime(tsk, &utime, &stime); | |
143 | write_seqlock(&sig->stats_lock); | |
144 | sig->utime += utime; | |
145 | sig->stime += stime; | |
146 | sig->gtime += task_gtime(tsk); | |
147 | sig->min_flt += tsk->min_flt; | |
148 | sig->maj_flt += tsk->maj_flt; | |
149 | sig->nvcsw += tsk->nvcsw; | |
150 | sig->nivcsw += tsk->nivcsw; | |
151 | sig->inblock += task_io_get_inblock(tsk); | |
152 | sig->oublock += task_io_get_oublock(tsk); | |
153 | task_io_accounting_add(&sig->ioac, &tsk->ioac); | |
154 | sig->sum_sched_runtime += tsk->se.sum_exec_runtime; | |
155 | sig->nr_threads--; | |
156 | __unhash_process(tsk, group_dead); | |
157 | write_sequnlock(&sig->stats_lock); | |
158 | ||
159 | /* | |
160 | * Do this under ->siglock, we can race with another thread | |
161 | * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals. | |
162 | */ | |
163 | flush_sigqueue(&tsk->pending); | |
164 | tsk->sighand = NULL; | |
165 | spin_unlock(&sighand->siglock); | |
166 | ||
167 | __cleanup_sighand(sighand); | |
168 | clear_tsk_thread_flag(tsk, TIF_SIGPENDING); | |
169 | if (group_dead) { | |
170 | flush_sigqueue(&sig->shared_pending); | |
171 | tty_kref_put(tty); | |
172 | } | |
173 | } | |
174 | ||
175 | static void delayed_put_task_struct(struct rcu_head *rhp) | |
176 | { | |
177 | struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); | |
178 | ||
179 | perf_event_delayed_put(tsk); | |
180 | trace_sched_process_free(tsk); | |
181 | put_task_struct(tsk); | |
182 | } | |
183 | ||
184 | ||
185 | void release_task(struct task_struct *p) | |
186 | { | |
187 | struct task_struct *leader; | |
188 | int zap_leader; | |
189 | repeat: | |
190 | /* don't need to get the RCU readlock here - the process is dead and | |
191 | * can't be modifying its own credentials. But shut RCU-lockdep up */ | |
192 | rcu_read_lock(); | |
193 | atomic_dec(&__task_cred(p)->user->processes); | |
194 | rcu_read_unlock(); | |
195 | ||
196 | proc_flush_task(p); | |
197 | ||
198 | write_lock_irq(&tasklist_lock); | |
199 | ptrace_release_task(p); | |
200 | __exit_signal(p); | |
201 | ||
202 | /* | |
203 | * If we are the last non-leader member of the thread | |
204 | * group, and the leader is zombie, then notify the | |
205 | * group leader's parent process. (if it wants notification.) | |
206 | */ | |
207 | zap_leader = 0; | |
208 | leader = p->group_leader; | |
209 | if (leader != p && thread_group_empty(leader) | |
210 | && leader->exit_state == EXIT_ZOMBIE) { | |
211 | /* | |
212 | * If we were the last child thread and the leader has | |
213 | * exited already, and the leader's parent ignores SIGCHLD, | |
214 | * then we are the one who should release the leader. | |
215 | */ | |
216 | zap_leader = do_notify_parent(leader, leader->exit_signal); | |
217 | if (zap_leader) | |
218 | leader->exit_state = EXIT_DEAD; | |
219 | } | |
220 | ||
221 | write_unlock_irq(&tasklist_lock); | |
222 | cgroup_release(p); | |
223 | release_thread(p); | |
224 | call_rcu(&p->rcu, delayed_put_task_struct); | |
225 | ||
226 | p = leader; | |
227 | if (unlikely(zap_leader)) | |
228 | goto repeat; | |
229 | } | |
230 | ||
231 | /* | |
232 | * Note that if this function returns a valid task_struct pointer (!NULL) | |
233 | * task->usage must remain >0 for the duration of the RCU critical section. | |
234 | */ | |
235 | struct task_struct *task_rcu_dereference(struct task_struct **ptask) | |
236 | { | |
237 | struct sighand_struct *sighand; | |
238 | struct task_struct *task; | |
239 | ||
240 | /* | |
241 | * We need to verify that release_task() was not called and thus | |
242 | * delayed_put_task_struct() can't run and drop the last reference | |
243 | * before rcu_read_unlock(). We check task->sighand != NULL, | |
244 | * but we can read the already freed and reused memory. | |
245 | */ | |
246 | retry: | |
247 | task = rcu_dereference(*ptask); | |
248 | if (!task) | |
249 | return NULL; | |
250 | ||
251 | probe_kernel_address(&task->sighand, sighand); | |
252 | ||
253 | /* | |
254 | * Pairs with atomic_dec_and_test() in put_task_struct(). If this task | |
255 | * was already freed we can not miss the preceding update of this | |
256 | * pointer. | |
257 | */ | |
258 | smp_rmb(); | |
259 | if (unlikely(task != READ_ONCE(*ptask))) | |
260 | goto retry; | |
261 | ||
262 | /* | |
263 | * We've re-checked that "task == *ptask", now we have two different | |
264 | * cases: | |
265 | * | |
266 | * 1. This is actually the same task/task_struct. In this case | |
267 | * sighand != NULL tells us it is still alive. | |
268 | * | |
269 | * 2. This is another task which got the same memory for task_struct. | |
270 | * We can't know this of course, and we can not trust | |
271 | * sighand != NULL. | |
272 | * | |
273 | * In this case we actually return a random value, but this is | |
274 | * correct. | |
275 | * | |
276 | * If we return NULL - we can pretend that we actually noticed that | |
277 | * *ptask was updated when the previous task has exited. Or pretend | |
278 | * that probe_slab_address(&sighand) reads NULL. | |
279 | * | |
280 | * If we return the new task (because sighand is not NULL for any | |
281 | * reason) - this is fine too. This (new) task can't go away before | |
282 | * another gp pass. | |
283 | * | |
284 | * And note: We could even eliminate the false positive if re-read | |
285 | * task->sighand once again to avoid the falsely NULL. But this case | |
286 | * is very unlikely so we don't care. | |
287 | */ | |
288 | if (!sighand) | |
289 | return NULL; | |
290 | ||
291 | return task; | |
292 | } | |
293 | ||
294 | void rcuwait_wake_up(struct rcuwait *w) | |
295 | { | |
296 | struct task_struct *task; | |
297 | ||
298 | rcu_read_lock(); | |
299 | ||
300 | /* | |
301 | * Order condition vs @task, such that everything prior to the load | |
302 | * of @task is visible. This is the condition as to why the user called | |
303 | * rcuwait_trywake() in the first place. Pairs with set_current_state() | |
304 | * barrier (A) in rcuwait_wait_event(). | |
305 | * | |
306 | * WAIT WAKE | |
307 | * [S] tsk = current [S] cond = true | |
308 | * MB (A) MB (B) | |
309 | * [L] cond [L] tsk | |
310 | */ | |
311 | smp_mb(); /* (B) */ | |
312 | ||
313 | /* | |
314 | * Avoid using task_rcu_dereference() magic as long as we are careful, | |
315 | * see comment in rcuwait_wait_event() regarding ->exit_state. | |
316 | */ | |
317 | task = rcu_dereference(w->task); | |
318 | if (task) | |
319 | wake_up_process(task); | |
320 | rcu_read_unlock(); | |
321 | } | |
322 | ||
323 | /* | |
324 | * Determine if a process group is "orphaned", according to the POSIX | |
325 | * definition in 2.2.2.52. Orphaned process groups are not to be affected | |
326 | * by terminal-generated stop signals. Newly orphaned process groups are | |
327 | * to receive a SIGHUP and a SIGCONT. | |
328 | * | |
329 | * "I ask you, have you ever known what it is to be an orphan?" | |
330 | */ | |
331 | static int will_become_orphaned_pgrp(struct pid *pgrp, | |
332 | struct task_struct *ignored_task) | |
333 | { | |
334 | struct task_struct *p; | |
335 | ||
336 | do_each_pid_task(pgrp, PIDTYPE_PGID, p) { | |
337 | if ((p == ignored_task) || | |
338 | (p->exit_state && thread_group_empty(p)) || | |
339 | is_global_init(p->real_parent)) | |
340 | continue; | |
341 | ||
342 | if (task_pgrp(p->real_parent) != pgrp && | |
343 | task_session(p->real_parent) == task_session(p)) | |
344 | return 0; | |
345 | } while_each_pid_task(pgrp, PIDTYPE_PGID, p); | |
346 | ||
347 | return 1; | |
348 | } | |
349 | ||
350 | int is_current_pgrp_orphaned(void) | |
351 | { | |
352 | int retval; | |
353 | ||
354 | read_lock(&tasklist_lock); | |
355 | retval = will_become_orphaned_pgrp(task_pgrp(current), NULL); | |
356 | read_unlock(&tasklist_lock); | |
357 | ||
358 | return retval; | |
359 | } | |
360 | ||
361 | static bool has_stopped_jobs(struct pid *pgrp) | |
362 | { | |
363 | struct task_struct *p; | |
364 | ||
365 | do_each_pid_task(pgrp, PIDTYPE_PGID, p) { | |
366 | if (p->signal->flags & SIGNAL_STOP_STOPPED) | |
367 | return true; | |
368 | } while_each_pid_task(pgrp, PIDTYPE_PGID, p); | |
369 | ||
370 | return false; | |
371 | } | |
372 | ||
373 | /* | |
374 | * Check to see if any process groups have become orphaned as | |
375 | * a result of our exiting, and if they have any stopped jobs, | |
376 | * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2) | |
377 | */ | |
378 | static void | |
379 | kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent) | |
380 | { | |
381 | struct pid *pgrp = task_pgrp(tsk); | |
382 | struct task_struct *ignored_task = tsk; | |
383 | ||
384 | if (!parent) | |
385 | /* exit: our father is in a different pgrp than | |
386 | * we are and we were the only connection outside. | |
387 | */ | |
388 | parent = tsk->real_parent; | |
389 | else | |
390 | /* reparent: our child is in a different pgrp than | |
391 | * we are, and it was the only connection outside. | |
392 | */ | |
393 | ignored_task = NULL; | |
394 | ||
395 | if (task_pgrp(parent) != pgrp && | |
396 | task_session(parent) == task_session(tsk) && | |
397 | will_become_orphaned_pgrp(pgrp, ignored_task) && | |
398 | has_stopped_jobs(pgrp)) { | |
399 | __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp); | |
400 | __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp); | |
401 | } | |
402 | } | |
403 | ||
404 | #ifdef CONFIG_MEMCG | |
405 | /* | |
406 | * A task is exiting. If it owned this mm, find a new owner for the mm. | |
407 | */ | |
408 | void mm_update_next_owner(struct mm_struct *mm) | |
409 | { | |
410 | struct task_struct *c, *g, *p = current; | |
411 | ||
412 | retry: | |
413 | /* | |
414 | * If the exiting or execing task is not the owner, it's | |
415 | * someone else's problem. | |
416 | */ | |
417 | if (mm->owner != p) | |
418 | return; | |
419 | /* | |
420 | * The current owner is exiting/execing and there are no other | |
421 | * candidates. Do not leave the mm pointing to a possibly | |
422 | * freed task structure. | |
423 | */ | |
424 | if (atomic_read(&mm->mm_users) <= 1) { | |
425 | mm->owner = NULL; | |
426 | return; | |
427 | } | |
428 | ||
429 | read_lock(&tasklist_lock); | |
430 | /* | |
431 | * Search in the children | |
432 | */ | |
433 | list_for_each_entry(c, &p->children, sibling) { | |
434 | if (c->mm == mm) | |
435 | goto assign_new_owner; | |
436 | } | |
437 | ||
438 | /* | |
439 | * Search in the siblings | |
440 | */ | |
441 | list_for_each_entry(c, &p->real_parent->children, sibling) { | |
442 | if (c->mm == mm) | |
443 | goto assign_new_owner; | |
444 | } | |
445 | ||
446 | /* | |
447 | * Search through everything else, we should not get here often. | |
448 | */ | |
449 | for_each_process(g) { | |
450 | if (g->flags & PF_KTHREAD) | |
451 | continue; | |
452 | for_each_thread(g, c) { | |
453 | if (c->mm == mm) | |
454 | goto assign_new_owner; | |
455 | if (c->mm) | |
456 | break; | |
457 | } | |
458 | } | |
459 | read_unlock(&tasklist_lock); | |
460 | /* | |
461 | * We found no owner yet mm_users > 1: this implies that we are | |
462 | * most likely racing with swapoff (try_to_unuse()) or /proc or | |
463 | * ptrace or page migration (get_task_mm()). Mark owner as NULL. | |
464 | */ | |
465 | mm->owner = NULL; | |
466 | return; | |
467 | ||
468 | assign_new_owner: | |
469 | BUG_ON(c == p); | |
470 | get_task_struct(c); | |
471 | /* | |
472 | * The task_lock protects c->mm from changing. | |
473 | * We always want mm->owner->mm == mm | |
474 | */ | |
475 | task_lock(c); | |
476 | /* | |
477 | * Delay read_unlock() till we have the task_lock() | |
478 | * to ensure that c does not slip away underneath us | |
479 | */ | |
480 | read_unlock(&tasklist_lock); | |
481 | if (c->mm != mm) { | |
482 | task_unlock(c); | |
483 | put_task_struct(c); | |
484 | goto retry; | |
485 | } | |
486 | mm->owner = c; | |
487 | task_unlock(c); | |
488 | put_task_struct(c); | |
489 | } | |
490 | #endif /* CONFIG_MEMCG */ | |
491 | ||
492 | /* | |
493 | * Turn us into a lazy TLB process if we | |
494 | * aren't already.. | |
495 | */ | |
496 | static void exit_mm(void) | |
497 | { | |
498 | struct mm_struct *mm = current->mm; | |
499 | struct core_state *core_state; | |
500 | ||
501 | mm_release(current, mm); | |
502 | if (!mm) | |
503 | return; | |
504 | sync_mm_rss(mm); | |
505 | /* | |
506 | * Serialize with any possible pending coredump. | |
507 | * We must hold mmap_sem around checking core_state | |
508 | * and clearing tsk->mm. The core-inducing thread | |
509 | * will increment ->nr_threads for each thread in the | |
510 | * group with ->mm != NULL. | |
511 | */ | |
512 | down_read(&mm->mmap_sem); | |
513 | core_state = mm->core_state; | |
514 | if (core_state) { | |
515 | struct core_thread self; | |
516 | ||
517 | up_read(&mm->mmap_sem); | |
518 | ||
519 | self.task = current; | |
520 | self.next = xchg(&core_state->dumper.next, &self); | |
521 | /* | |
522 | * Implies mb(), the result of xchg() must be visible | |
523 | * to core_state->dumper. | |
524 | */ | |
525 | if (atomic_dec_and_test(&core_state->nr_threads)) | |
526 | complete(&core_state->startup); | |
527 | ||
528 | for (;;) { | |
529 | set_current_state(TASK_UNINTERRUPTIBLE); | |
530 | if (!self.task) /* see coredump_finish() */ | |
531 | break; | |
532 | freezable_schedule(); | |
533 | } | |
534 | __set_current_state(TASK_RUNNING); | |
535 | down_read(&mm->mmap_sem); | |
536 | } | |
537 | mmgrab(mm); | |
538 | BUG_ON(mm != current->active_mm); | |
539 | /* more a memory barrier than a real lock */ | |
540 | task_lock(current); | |
541 | current->mm = NULL; | |
542 | up_read(&mm->mmap_sem); | |
543 | enter_lazy_tlb(mm, current); | |
544 | task_unlock(current); | |
545 | mm_update_next_owner(mm); | |
546 | mmput(mm); | |
547 | if (test_thread_flag(TIF_MEMDIE)) | |
548 | exit_oom_victim(); | |
549 | } | |
550 | ||
551 | static struct task_struct *find_alive_thread(struct task_struct *p) | |
552 | { | |
553 | struct task_struct *t; | |
554 | ||
555 | for_each_thread(p, t) { | |
556 | if (!(t->flags & PF_EXITING)) | |
557 | return t; | |
558 | } | |
559 | return NULL; | |
560 | } | |
561 | ||
562 | static struct task_struct *find_child_reaper(struct task_struct *father, | |
563 | struct list_head *dead) | |
564 | __releases(&tasklist_lock) | |
565 | __acquires(&tasklist_lock) | |
566 | { | |
567 | struct pid_namespace *pid_ns = task_active_pid_ns(father); | |
568 | struct task_struct *reaper = pid_ns->child_reaper; | |
569 | struct task_struct *p, *n; | |
570 | ||
571 | if (likely(reaper != father)) | |
572 | return reaper; | |
573 | ||
574 | reaper = find_alive_thread(father); | |
575 | if (reaper) { | |
576 | pid_ns->child_reaper = reaper; | |
577 | return reaper; | |
578 | } | |
579 | ||
580 | write_unlock_irq(&tasklist_lock); | |
581 | if (unlikely(pid_ns == &init_pid_ns)) { | |
582 | panic("Attempted to kill init! exitcode=0x%08x\n", | |
583 | father->signal->group_exit_code ?: father->exit_code); | |
584 | } | |
585 | ||
586 | list_for_each_entry_safe(p, n, dead, ptrace_entry) { | |
587 | list_del_init(&p->ptrace_entry); | |
588 | release_task(p); | |
589 | } | |
590 | ||
591 | zap_pid_ns_processes(pid_ns); | |
592 | write_lock_irq(&tasklist_lock); | |
593 | ||
594 | return father; | |
595 | } | |
596 | ||
597 | /* | |
598 | * When we die, we re-parent all our children, and try to: | |
599 | * 1. give them to another thread in our thread group, if such a member exists | |
600 | * 2. give it to the first ancestor process which prctl'd itself as a | |
601 | * child_subreaper for its children (like a service manager) | |
602 | * 3. give it to the init process (PID 1) in our pid namespace | |
603 | */ | |
604 | static struct task_struct *find_new_reaper(struct task_struct *father, | |
605 | struct task_struct *child_reaper) | |
606 | { | |
607 | struct task_struct *thread, *reaper; | |
608 | ||
609 | thread = find_alive_thread(father); | |
610 | if (thread) | |
611 | return thread; | |
612 | ||
613 | if (father->signal->has_child_subreaper) { | |
614 | unsigned int ns_level = task_pid(father)->level; | |
615 | /* | |
616 | * Find the first ->is_child_subreaper ancestor in our pid_ns. | |
617 | * We can't check reaper != child_reaper to ensure we do not | |
618 | * cross the namespaces, the exiting parent could be injected | |
619 | * by setns() + fork(). | |
620 | * We check pid->level, this is slightly more efficient than | |
621 | * task_active_pid_ns(reaper) != task_active_pid_ns(father). | |
622 | */ | |
623 | for (reaper = father->real_parent; | |
624 | task_pid(reaper)->level == ns_level; | |
625 | reaper = reaper->real_parent) { | |
626 | if (reaper == &init_task) | |
627 | break; | |
628 | if (!reaper->signal->is_child_subreaper) | |
629 | continue; | |
630 | thread = find_alive_thread(reaper); | |
631 | if (thread) | |
632 | return thread; | |
633 | } | |
634 | } | |
635 | ||
636 | return child_reaper; | |
637 | } | |
638 | ||
639 | /* | |
640 | * Any that need to be release_task'd are put on the @dead list. | |
641 | */ | |
642 | static void reparent_leader(struct task_struct *father, struct task_struct *p, | |
643 | struct list_head *dead) | |
644 | { | |
645 | if (unlikely(p->exit_state == EXIT_DEAD)) | |
646 | return; | |
647 | ||
648 | /* We don't want people slaying init. */ | |
649 | p->exit_signal = SIGCHLD; | |
650 | ||
651 | /* If it has exited notify the new parent about this child's death. */ | |
652 | if (!p->ptrace && | |
653 | p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) { | |
654 | if (do_notify_parent(p, p->exit_signal)) { | |
655 | p->exit_state = EXIT_DEAD; | |
656 | list_add(&p->ptrace_entry, dead); | |
657 | } | |
658 | } | |
659 | ||
660 | kill_orphaned_pgrp(p, father); | |
661 | } | |
662 | ||
663 | /* | |
664 | * This does two things: | |
665 | * | |
666 | * A. Make init inherit all the child processes | |
667 | * B. Check to see if any process groups have become orphaned | |
668 | * as a result of our exiting, and if they have any stopped | |
669 | * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2) | |
670 | */ | |
671 | static void forget_original_parent(struct task_struct *father, | |
672 | struct list_head *dead) | |
673 | { | |
674 | struct task_struct *p, *t, *reaper; | |
675 | ||
676 | if (unlikely(!list_empty(&father->ptraced))) | |
677 | exit_ptrace(father, dead); | |
678 | ||
679 | /* Can drop and reacquire tasklist_lock */ | |
680 | reaper = find_child_reaper(father, dead); | |
681 | if (list_empty(&father->children)) | |
682 | return; | |
683 | ||
684 | reaper = find_new_reaper(father, reaper); | |
685 | list_for_each_entry(p, &father->children, sibling) { | |
686 | for_each_thread(p, t) { | |
687 | t->real_parent = reaper; | |
688 | BUG_ON((!t->ptrace) != (t->parent == father)); | |
689 | if (likely(!t->ptrace)) | |
690 | t->parent = t->real_parent; | |
691 | if (t->pdeath_signal) | |
692 | group_send_sig_info(t->pdeath_signal, | |
693 | SEND_SIG_NOINFO, t, | |
694 | PIDTYPE_TGID); | |
695 | } | |
696 | /* | |
697 | * If this is a threaded reparent there is no need to | |
698 | * notify anyone anything has happened. | |
699 | */ | |
700 | if (!same_thread_group(reaper, father)) | |
701 | reparent_leader(father, p, dead); | |
702 | } | |
703 | list_splice_tail_init(&father->children, &reaper->children); | |
704 | } | |
705 | ||
706 | /* | |
707 | * Send signals to all our closest relatives so that they know | |
708 | * to properly mourn us.. | |
709 | */ | |
710 | static void exit_notify(struct task_struct *tsk, int group_dead) | |
711 | { | |
712 | bool autoreap; | |
713 | struct task_struct *p, *n; | |
714 | LIST_HEAD(dead); | |
715 | ||
716 | write_lock_irq(&tasklist_lock); | |
717 | forget_original_parent(tsk, &dead); | |
718 | ||
719 | if (group_dead) | |
720 | kill_orphaned_pgrp(tsk->group_leader, NULL); | |
721 | ||
722 | if (unlikely(tsk->ptrace)) { | |
723 | int sig = thread_group_leader(tsk) && | |
724 | thread_group_empty(tsk) && | |
725 | !ptrace_reparented(tsk) ? | |
726 | tsk->exit_signal : SIGCHLD; | |
727 | autoreap = do_notify_parent(tsk, sig); | |
728 | } else if (thread_group_leader(tsk)) { | |
729 | autoreap = thread_group_empty(tsk) && | |
730 | do_notify_parent(tsk, tsk->exit_signal); | |
731 | } else { | |
732 | autoreap = true; | |
733 | } | |
734 | ||
735 | tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE; | |
736 | if (tsk->exit_state == EXIT_DEAD) | |
737 | list_add(&tsk->ptrace_entry, &dead); | |
738 | ||
739 | /* mt-exec, de_thread() is waiting for group leader */ | |
740 | if (unlikely(tsk->signal->notify_count < 0)) | |
741 | wake_up_process(tsk->signal->group_exit_task); | |
742 | write_unlock_irq(&tasklist_lock); | |
743 | ||
744 | list_for_each_entry_safe(p, n, &dead, ptrace_entry) { | |
745 | list_del_init(&p->ptrace_entry); | |
746 | release_task(p); | |
747 | } | |
748 | } | |
749 | ||
750 | #ifdef CONFIG_DEBUG_STACK_USAGE | |
751 | static void check_stack_usage(void) | |
752 | { | |
753 | static DEFINE_SPINLOCK(low_water_lock); | |
754 | static int lowest_to_date = THREAD_SIZE; | |
755 | unsigned long free; | |
756 | ||
757 | free = stack_not_used(current); | |
758 | ||
759 | if (free >= lowest_to_date) | |
760 | return; | |
761 | ||
762 | spin_lock(&low_water_lock); | |
763 | if (free < lowest_to_date) { | |
764 | pr_info("%s (%d) used greatest stack depth: %lu bytes left\n", | |
765 | current->comm, task_pid_nr(current), free); | |
766 | lowest_to_date = free; | |
767 | } | |
768 | spin_unlock(&low_water_lock); | |
769 | } | |
770 | #else | |
771 | static inline void check_stack_usage(void) {} | |
772 | #endif | |
773 | ||
774 | void __noreturn do_exit(long code) | |
775 | { | |
776 | struct task_struct *tsk = current; | |
777 | int group_dead; | |
778 | ||
779 | profile_task_exit(tsk); | |
780 | kcov_task_exit(tsk); | |
781 | ||
782 | WARN_ON(blk_needs_flush_plug(tsk)); | |
783 | ||
784 | if (unlikely(in_interrupt())) | |
785 | panic("Aiee, killing interrupt handler!"); | |
786 | if (unlikely(!tsk->pid)) | |
787 | panic("Attempted to kill the idle task!"); | |
788 | ||
789 | /* | |
790 | * If do_exit is called because this processes oopsed, it's possible | |
791 | * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before | |
792 | * continuing. Amongst other possible reasons, this is to prevent | |
793 | * mm_release()->clear_child_tid() from writing to a user-controlled | |
794 | * kernel address. | |
795 | */ | |
796 | set_fs(USER_DS); | |
797 | ||
798 | ptrace_event(PTRACE_EVENT_EXIT, code); | |
799 | ||
800 | validate_creds_for_do_exit(tsk); | |
801 | ||
802 | /* | |
803 | * We're taking recursive faults here in do_exit. Safest is to just | |
804 | * leave this task alone and wait for reboot. | |
805 | */ | |
806 | if (unlikely(tsk->flags & PF_EXITING)) { | |
807 | pr_alert("Fixing recursive fault but reboot is needed!\n"); | |
808 | /* | |
809 | * We can do this unlocked here. The futex code uses | |
810 | * this flag just to verify whether the pi state | |
811 | * cleanup has been done or not. In the worst case it | |
812 | * loops once more. We pretend that the cleanup was | |
813 | * done as there is no way to return. Either the | |
814 | * OWNER_DIED bit is set by now or we push the blocked | |
815 | * task into the wait for ever nirwana as well. | |
816 | */ | |
817 | tsk->flags |= PF_EXITPIDONE; | |
818 | set_current_state(TASK_UNINTERRUPTIBLE); | |
819 | schedule(); | |
820 | } | |
821 | ||
822 | exit_signals(tsk); /* sets PF_EXITING */ | |
823 | /* | |
824 | * Ensure that all new tsk->pi_lock acquisitions must observe | |
825 | * PF_EXITING. Serializes against futex.c:attach_to_pi_owner(). | |
826 | */ | |
827 | smp_mb(); | |
828 | /* | |
829 | * Ensure that we must observe the pi_state in exit_mm() -> | |
830 | * mm_release() -> exit_pi_state_list(). | |
831 | */ | |
832 | raw_spin_lock_irq(&tsk->pi_lock); | |
833 | raw_spin_unlock_irq(&tsk->pi_lock); | |
834 | ||
835 | if (unlikely(in_atomic())) { | |
836 | pr_info("note: %s[%d] exited with preempt_count %d\n", | |
837 | current->comm, task_pid_nr(current), | |
838 | preempt_count()); | |
839 | preempt_count_set(PREEMPT_ENABLED); | |
840 | } | |
841 | ||
842 | /* sync mm's RSS info before statistics gathering */ | |
843 | if (tsk->mm) | |
844 | sync_mm_rss(tsk->mm); | |
845 | acct_update_integrals(tsk); | |
846 | group_dead = atomic_dec_and_test(&tsk->signal->live); | |
847 | if (group_dead) { | |
848 | #ifdef CONFIG_POSIX_TIMERS | |
849 | hrtimer_cancel(&tsk->signal->real_timer); | |
850 | exit_itimers(tsk->signal); | |
851 | #endif | |
852 | if (tsk->mm) | |
853 | setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); | |
854 | } | |
855 | acct_collect(code, group_dead); | |
856 | if (group_dead) | |
857 | tty_audit_exit(); | |
858 | audit_free(tsk); | |
859 | ||
860 | tsk->exit_code = code; | |
861 | taskstats_exit(tsk, group_dead); | |
862 | ||
863 | exit_mm(); | |
864 | ||
865 | if (group_dead) | |
866 | acct_process(); | |
867 | trace_sched_process_exit(tsk); | |
868 | ||
869 | exit_sem(tsk); | |
870 | exit_shm(tsk); | |
871 | exit_files(tsk); | |
872 | exit_fs(tsk); | |
873 | if (group_dead) | |
874 | disassociate_ctty(1); | |
875 | exit_task_namespaces(tsk); | |
876 | exit_task_work(tsk); | |
877 | exit_thread(tsk); | |
878 | exit_umh(tsk); | |
879 | ||
880 | /* | |
881 | * Flush inherited counters to the parent - before the parent | |
882 | * gets woken up by child-exit notifications. | |
883 | * | |
884 | * because of cgroup mode, must be called before cgroup_exit() | |
885 | */ | |
886 | perf_event_exit_task(tsk); | |
887 | ||
888 | sched_autogroup_exit_task(tsk); | |
889 | cgroup_exit(tsk); | |
890 | ||
891 | /* | |
892 | * FIXME: do that only when needed, using sched_exit tracepoint | |
893 | */ | |
894 | flush_ptrace_hw_breakpoint(tsk); | |
895 | ||
896 | exit_tasks_rcu_start(); | |
897 | exit_notify(tsk, group_dead); | |
898 | proc_exit_connector(tsk); | |
899 | mpol_put_task_policy(tsk); | |
900 | #ifdef CONFIG_FUTEX | |
901 | if (unlikely(current->pi_state_cache)) | |
902 | kfree(current->pi_state_cache); | |
903 | #endif | |
904 | /* | |
905 | * Make sure we are holding no locks: | |
906 | */ | |
907 | debug_check_no_locks_held(); | |
908 | /* | |
909 | * We can do this unlocked here. The futex code uses this flag | |
910 | * just to verify whether the pi state cleanup has been done | |
911 | * or not. In the worst case it loops once more. | |
912 | */ | |
913 | tsk->flags |= PF_EXITPIDONE; | |
914 | ||
915 | if (tsk->io_context) | |
916 | exit_io_context(tsk); | |
917 | ||
918 | if (tsk->splice_pipe) | |
919 | free_pipe_info(tsk->splice_pipe); | |
920 | ||
921 | if (tsk->task_frag.page) | |
922 | put_page(tsk->task_frag.page); | |
923 | ||
924 | validate_creds_for_do_exit(tsk); | |
925 | ||
926 | check_stack_usage(); | |
927 | preempt_disable(); | |
928 | if (tsk->nr_dirtied) | |
929 | __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied); | |
930 | exit_rcu(); | |
931 | exit_tasks_rcu_finish(); | |
932 | ||
933 | lockdep_free_task(tsk); | |
934 | do_task_dead(); | |
935 | } | |
936 | EXPORT_SYMBOL_GPL(do_exit); | |
937 | ||
938 | void complete_and_exit(struct completion *comp, long code) | |
939 | { | |
940 | if (comp) | |
941 | complete(comp); | |
942 | ||
943 | do_exit(code); | |
944 | } | |
945 | EXPORT_SYMBOL(complete_and_exit); | |
946 | ||
947 | SYSCALL_DEFINE1(exit, int, error_code) | |
948 | { | |
949 | do_exit((error_code&0xff)<<8); | |
950 | } | |
951 | ||
952 | /* | |
953 | * Take down every thread in the group. This is called by fatal signals | |
954 | * as well as by sys_exit_group (below). | |
955 | */ | |
956 | void | |
957 | do_group_exit(int exit_code) | |
958 | { | |
959 | struct signal_struct *sig = current->signal; | |
960 | ||
961 | BUG_ON(exit_code & 0x80); /* core dumps don't get here */ | |
962 | ||
963 | if (signal_group_exit(sig)) | |
964 | exit_code = sig->group_exit_code; | |
965 | else if (!thread_group_empty(current)) { | |
966 | struct sighand_struct *const sighand = current->sighand; | |
967 | ||
968 | spin_lock_irq(&sighand->siglock); | |
969 | if (signal_group_exit(sig)) | |
970 | /* Another thread got here before we took the lock. */ | |
971 | exit_code = sig->group_exit_code; | |
972 | else { | |
973 | sig->group_exit_code = exit_code; | |
974 | sig->flags = SIGNAL_GROUP_EXIT; | |
975 | zap_other_threads(current); | |
976 | } | |
977 | spin_unlock_irq(&sighand->siglock); | |
978 | } | |
979 | ||
980 | do_exit(exit_code); | |
981 | /* NOTREACHED */ | |
982 | } | |
983 | ||
984 | /* | |
985 | * this kills every thread in the thread group. Note that any externally | |
986 | * wait4()-ing process will get the correct exit code - even if this | |
987 | * thread is not the thread group leader. | |
988 | */ | |
989 | SYSCALL_DEFINE1(exit_group, int, error_code) | |
990 | { | |
991 | do_group_exit((error_code & 0xff) << 8); | |
992 | /* NOTREACHED */ | |
993 | return 0; | |
994 | } | |
995 | ||
996 | struct waitid_info { | |
997 | pid_t pid; | |
998 | uid_t uid; | |
999 | int status; | |
1000 | int cause; | |
1001 | }; | |
1002 | ||
1003 | struct wait_opts { | |
1004 | enum pid_type wo_type; | |
1005 | int wo_flags; | |
1006 | struct pid *wo_pid; | |
1007 | ||
1008 | struct waitid_info *wo_info; | |
1009 | int wo_stat; | |
1010 | struct rusage *wo_rusage; | |
1011 | ||
1012 | wait_queue_entry_t child_wait; | |
1013 | int notask_error; | |
1014 | }; | |
1015 | ||
1016 | static int eligible_pid(struct wait_opts *wo, struct task_struct *p) | |
1017 | { | |
1018 | return wo->wo_type == PIDTYPE_MAX || | |
1019 | task_pid_type(p, wo->wo_type) == wo->wo_pid; | |
1020 | } | |
1021 | ||
1022 | static int | |
1023 | eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p) | |
1024 | { | |
1025 | if (!eligible_pid(wo, p)) | |
1026 | return 0; | |
1027 | ||
1028 | /* | |
1029 | * Wait for all children (clone and not) if __WALL is set or | |
1030 | * if it is traced by us. | |
1031 | */ | |
1032 | if (ptrace || (wo->wo_flags & __WALL)) | |
1033 | return 1; | |
1034 | ||
1035 | /* | |
1036 | * Otherwise, wait for clone children *only* if __WCLONE is set; | |
1037 | * otherwise, wait for non-clone children *only*. | |
1038 | * | |
1039 | * Note: a "clone" child here is one that reports to its parent | |
1040 | * using a signal other than SIGCHLD, or a non-leader thread which | |
1041 | * we can only see if it is traced by us. | |
1042 | */ | |
1043 | if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE)) | |
1044 | return 0; | |
1045 | ||
1046 | return 1; | |
1047 | } | |
1048 | ||
1049 | /* | |
1050 | * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold | |
1051 | * read_lock(&tasklist_lock) on entry. If we return zero, we still hold | |
1052 | * the lock and this task is uninteresting. If we return nonzero, we have | |
1053 | * released the lock and the system call should return. | |
1054 | */ | |
1055 | static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) | |
1056 | { | |
1057 | int state, status; | |
1058 | pid_t pid = task_pid_vnr(p); | |
1059 | uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p)); | |
1060 | struct waitid_info *infop; | |
1061 | ||
1062 | if (!likely(wo->wo_flags & WEXITED)) | |
1063 | return 0; | |
1064 | ||
1065 | if (unlikely(wo->wo_flags & WNOWAIT)) { | |
1066 | status = p->exit_code; | |
1067 | get_task_struct(p); | |
1068 | read_unlock(&tasklist_lock); | |
1069 | sched_annotate_sleep(); | |
1070 | if (wo->wo_rusage) | |
1071 | getrusage(p, RUSAGE_BOTH, wo->wo_rusage); | |
1072 | put_task_struct(p); | |
1073 | goto out_info; | |
1074 | } | |
1075 | /* | |
1076 | * Move the task's state to DEAD/TRACE, only one thread can do this. | |
1077 | */ | |
1078 | state = (ptrace_reparented(p) && thread_group_leader(p)) ? | |
1079 | EXIT_TRACE : EXIT_DEAD; | |
1080 | if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE) | |
1081 | return 0; | |
1082 | /* | |
1083 | * We own this thread, nobody else can reap it. | |
1084 | */ | |
1085 | read_unlock(&tasklist_lock); | |
1086 | sched_annotate_sleep(); | |
1087 | ||
1088 | /* | |
1089 | * Check thread_group_leader() to exclude the traced sub-threads. | |
1090 | */ | |
1091 | if (state == EXIT_DEAD && thread_group_leader(p)) { | |
1092 | struct signal_struct *sig = p->signal; | |
1093 | struct signal_struct *psig = current->signal; | |
1094 | unsigned long maxrss; | |
1095 | u64 tgutime, tgstime; | |
1096 | ||
1097 | /* | |
1098 | * The resource counters for the group leader are in its | |
1099 | * own task_struct. Those for dead threads in the group | |
1100 | * are in its signal_struct, as are those for the child | |
1101 | * processes it has previously reaped. All these | |
1102 | * accumulate in the parent's signal_struct c* fields. | |
1103 | * | |
1104 | * We don't bother to take a lock here to protect these | |
1105 | * p->signal fields because the whole thread group is dead | |
1106 | * and nobody can change them. | |
1107 | * | |
1108 | * psig->stats_lock also protects us from our sub-theads | |
1109 | * which can reap other children at the same time. Until | |
1110 | * we change k_getrusage()-like users to rely on this lock | |
1111 | * we have to take ->siglock as well. | |
1112 | * | |
1113 | * We use thread_group_cputime_adjusted() to get times for | |
1114 | * the thread group, which consolidates times for all threads | |
1115 | * in the group including the group leader. | |
1116 | */ | |
1117 | thread_group_cputime_adjusted(p, &tgutime, &tgstime); | |
1118 | spin_lock_irq(¤t->sighand->siglock); | |
1119 | write_seqlock(&psig->stats_lock); | |
1120 | psig->cutime += tgutime + sig->cutime; | |
1121 | psig->cstime += tgstime + sig->cstime; | |
1122 | psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime; | |
1123 | psig->cmin_flt += | |
1124 | p->min_flt + sig->min_flt + sig->cmin_flt; | |
1125 | psig->cmaj_flt += | |
1126 | p->maj_flt + sig->maj_flt + sig->cmaj_flt; | |
1127 | psig->cnvcsw += | |
1128 | p->nvcsw + sig->nvcsw + sig->cnvcsw; | |
1129 | psig->cnivcsw += | |
1130 | p->nivcsw + sig->nivcsw + sig->cnivcsw; | |
1131 | psig->cinblock += | |
1132 | task_io_get_inblock(p) + | |
1133 | sig->inblock + sig->cinblock; | |
1134 | psig->coublock += | |
1135 | task_io_get_oublock(p) + | |
1136 | sig->oublock + sig->coublock; | |
1137 | maxrss = max(sig->maxrss, sig->cmaxrss); | |
1138 | if (psig->cmaxrss < maxrss) | |
1139 | psig->cmaxrss = maxrss; | |
1140 | task_io_accounting_add(&psig->ioac, &p->ioac); | |
1141 | task_io_accounting_add(&psig->ioac, &sig->ioac); | |
1142 | write_sequnlock(&psig->stats_lock); | |
1143 | spin_unlock_irq(¤t->sighand->siglock); | |
1144 | } | |
1145 | ||
1146 | if (wo->wo_rusage) | |
1147 | getrusage(p, RUSAGE_BOTH, wo->wo_rusage); | |
1148 | status = (p->signal->flags & SIGNAL_GROUP_EXIT) | |
1149 | ? p->signal->group_exit_code : p->exit_code; | |
1150 | wo->wo_stat = status; | |
1151 | ||
1152 | if (state == EXIT_TRACE) { | |
1153 | write_lock_irq(&tasklist_lock); | |
1154 | /* We dropped tasklist, ptracer could die and untrace */ | |
1155 | ptrace_unlink(p); | |
1156 | ||
1157 | /* If parent wants a zombie, don't release it now */ | |
1158 | state = EXIT_ZOMBIE; | |
1159 | if (do_notify_parent(p, p->exit_signal)) | |
1160 | state = EXIT_DEAD; | |
1161 | p->exit_state = state; | |
1162 | write_unlock_irq(&tasklist_lock); | |
1163 | } | |
1164 | if (state == EXIT_DEAD) | |
1165 | release_task(p); | |
1166 | ||
1167 | out_info: | |
1168 | infop = wo->wo_info; | |
1169 | if (infop) { | |
1170 | if ((status & 0x7f) == 0) { | |
1171 | infop->cause = CLD_EXITED; | |
1172 | infop->status = status >> 8; | |
1173 | } else { | |
1174 | infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; | |
1175 | infop->status = status & 0x7f; | |
1176 | } | |
1177 | infop->pid = pid; | |
1178 | infop->uid = uid; | |
1179 | } | |
1180 | ||
1181 | return pid; | |
1182 | } | |
1183 | ||
1184 | static int *task_stopped_code(struct task_struct *p, bool ptrace) | |
1185 | { | |
1186 | if (ptrace) { | |
1187 | if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING)) | |
1188 | return &p->exit_code; | |
1189 | } else { | |
1190 | if (p->signal->flags & SIGNAL_STOP_STOPPED) | |
1191 | return &p->signal->group_exit_code; | |
1192 | } | |
1193 | return NULL; | |
1194 | } | |
1195 | ||
1196 | /** | |
1197 | * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED | |
1198 | * @wo: wait options | |
1199 | * @ptrace: is the wait for ptrace | |
1200 | * @p: task to wait for | |
1201 | * | |
1202 | * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED. | |
1203 | * | |
1204 | * CONTEXT: | |
1205 | * read_lock(&tasklist_lock), which is released if return value is | |
1206 | * non-zero. Also, grabs and releases @p->sighand->siglock. | |
1207 | * | |
1208 | * RETURNS: | |
1209 | * 0 if wait condition didn't exist and search for other wait conditions | |
1210 | * should continue. Non-zero return, -errno on failure and @p's pid on | |
1211 | * success, implies that tasklist_lock is released and wait condition | |
1212 | * search should terminate. | |
1213 | */ | |
1214 | static int wait_task_stopped(struct wait_opts *wo, | |
1215 | int ptrace, struct task_struct *p) | |
1216 | { | |
1217 | struct waitid_info *infop; | |
1218 | int exit_code, *p_code, why; | |
1219 | uid_t uid = 0; /* unneeded, required by compiler */ | |
1220 | pid_t pid; | |
1221 | ||
1222 | /* | |
1223 | * Traditionally we see ptrace'd stopped tasks regardless of options. | |
1224 | */ | |
1225 | if (!ptrace && !(wo->wo_flags & WUNTRACED)) | |
1226 | return 0; | |
1227 | ||
1228 | if (!task_stopped_code(p, ptrace)) | |
1229 | return 0; | |
1230 | ||
1231 | exit_code = 0; | |
1232 | spin_lock_irq(&p->sighand->siglock); | |
1233 | ||
1234 | p_code = task_stopped_code(p, ptrace); | |
1235 | if (unlikely(!p_code)) | |
1236 | goto unlock_sig; | |
1237 | ||
1238 | exit_code = *p_code; | |
1239 | if (!exit_code) | |
1240 | goto unlock_sig; | |
1241 | ||
1242 | if (!unlikely(wo->wo_flags & WNOWAIT)) | |
1243 | *p_code = 0; | |
1244 | ||
1245 | uid = from_kuid_munged(current_user_ns(), task_uid(p)); | |
1246 | unlock_sig: | |
1247 | spin_unlock_irq(&p->sighand->siglock); | |
1248 | if (!exit_code) | |
1249 | return 0; | |
1250 | ||
1251 | /* | |
1252 | * Now we are pretty sure this task is interesting. | |
1253 | * Make sure it doesn't get reaped out from under us while we | |
1254 | * give up the lock and then examine it below. We don't want to | |
1255 | * keep holding onto the tasklist_lock while we call getrusage and | |
1256 | * possibly take page faults for user memory. | |
1257 | */ | |
1258 | get_task_struct(p); | |
1259 | pid = task_pid_vnr(p); | |
1260 | why = ptrace ? CLD_TRAPPED : CLD_STOPPED; | |
1261 | read_unlock(&tasklist_lock); | |
1262 | sched_annotate_sleep(); | |
1263 | if (wo->wo_rusage) | |
1264 | getrusage(p, RUSAGE_BOTH, wo->wo_rusage); | |
1265 | put_task_struct(p); | |
1266 | ||
1267 | if (likely(!(wo->wo_flags & WNOWAIT))) | |
1268 | wo->wo_stat = (exit_code << 8) | 0x7f; | |
1269 | ||
1270 | infop = wo->wo_info; | |
1271 | if (infop) { | |
1272 | infop->cause = why; | |
1273 | infop->status = exit_code; | |
1274 | infop->pid = pid; | |
1275 | infop->uid = uid; | |
1276 | } | |
1277 | return pid; | |
1278 | } | |
1279 | ||
1280 | /* | |
1281 | * Handle do_wait work for one task in a live, non-stopped state. | |
1282 | * read_lock(&tasklist_lock) on entry. If we return zero, we still hold | |
1283 | * the lock and this task is uninteresting. If we return nonzero, we have | |
1284 | * released the lock and the system call should return. | |
1285 | */ | |
1286 | static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) | |
1287 | { | |
1288 | struct waitid_info *infop; | |
1289 | pid_t pid; | |
1290 | uid_t uid; | |
1291 | ||
1292 | if (!unlikely(wo->wo_flags & WCONTINUED)) | |
1293 | return 0; | |
1294 | ||
1295 | if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) | |
1296 | return 0; | |
1297 | ||
1298 | spin_lock_irq(&p->sighand->siglock); | |
1299 | /* Re-check with the lock held. */ | |
1300 | if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) { | |
1301 | spin_unlock_irq(&p->sighand->siglock); | |
1302 | return 0; | |
1303 | } | |
1304 | if (!unlikely(wo->wo_flags & WNOWAIT)) | |
1305 | p->signal->flags &= ~SIGNAL_STOP_CONTINUED; | |
1306 | uid = from_kuid_munged(current_user_ns(), task_uid(p)); | |
1307 | spin_unlock_irq(&p->sighand->siglock); | |
1308 | ||
1309 | pid = task_pid_vnr(p); | |
1310 | get_task_struct(p); | |
1311 | read_unlock(&tasklist_lock); | |
1312 | sched_annotate_sleep(); | |
1313 | if (wo->wo_rusage) | |
1314 | getrusage(p, RUSAGE_BOTH, wo->wo_rusage); | |
1315 | put_task_struct(p); | |
1316 | ||
1317 | infop = wo->wo_info; | |
1318 | if (!infop) { | |
1319 | wo->wo_stat = 0xffff; | |
1320 | } else { | |
1321 | infop->cause = CLD_CONTINUED; | |
1322 | infop->pid = pid; | |
1323 | infop->uid = uid; | |
1324 | infop->status = SIGCONT; | |
1325 | } | |
1326 | return pid; | |
1327 | } | |
1328 | ||
1329 | /* | |
1330 | * Consider @p for a wait by @parent. | |
1331 | * | |
1332 | * -ECHILD should be in ->notask_error before the first call. | |
1333 | * Returns nonzero for a final return, when we have unlocked tasklist_lock. | |
1334 | * Returns zero if the search for a child should continue; | |
1335 | * then ->notask_error is 0 if @p is an eligible child, | |
1336 | * or still -ECHILD. | |
1337 | */ | |
1338 | static int wait_consider_task(struct wait_opts *wo, int ptrace, | |
1339 | struct task_struct *p) | |
1340 | { | |
1341 | /* | |
1342 | * We can race with wait_task_zombie() from another thread. | |
1343 | * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition | |
1344 | * can't confuse the checks below. | |
1345 | */ | |
1346 | int exit_state = READ_ONCE(p->exit_state); | |
1347 | int ret; | |
1348 | ||
1349 | if (unlikely(exit_state == EXIT_DEAD)) | |
1350 | return 0; | |
1351 | ||
1352 | ret = eligible_child(wo, ptrace, p); | |
1353 | if (!ret) | |
1354 | return ret; | |
1355 | ||
1356 | if (unlikely(exit_state == EXIT_TRACE)) { | |
1357 | /* | |
1358 | * ptrace == 0 means we are the natural parent. In this case | |
1359 | * we should clear notask_error, debugger will notify us. | |
1360 | */ | |
1361 | if (likely(!ptrace)) | |
1362 | wo->notask_error = 0; | |
1363 | return 0; | |
1364 | } | |
1365 | ||
1366 | if (likely(!ptrace) && unlikely(p->ptrace)) { | |
1367 | /* | |
1368 | * If it is traced by its real parent's group, just pretend | |
1369 | * the caller is ptrace_do_wait() and reap this child if it | |
1370 | * is zombie. | |
1371 | * | |
1372 | * This also hides group stop state from real parent; otherwise | |
1373 | * a single stop can be reported twice as group and ptrace stop. | |
1374 | * If a ptracer wants to distinguish these two events for its | |
1375 | * own children it should create a separate process which takes | |
1376 | * the role of real parent. | |
1377 | */ | |
1378 | if (!ptrace_reparented(p)) | |
1379 | ptrace = 1; | |
1380 | } | |
1381 | ||
1382 | /* slay zombie? */ | |
1383 | if (exit_state == EXIT_ZOMBIE) { | |
1384 | /* we don't reap group leaders with subthreads */ | |
1385 | if (!delay_group_leader(p)) { | |
1386 | /* | |
1387 | * A zombie ptracee is only visible to its ptracer. | |
1388 | * Notification and reaping will be cascaded to the | |
1389 | * real parent when the ptracer detaches. | |
1390 | */ | |
1391 | if (unlikely(ptrace) || likely(!p->ptrace)) | |
1392 | return wait_task_zombie(wo, p); | |
1393 | } | |
1394 | ||
1395 | /* | |
1396 | * Allow access to stopped/continued state via zombie by | |
1397 | * falling through. Clearing of notask_error is complex. | |
1398 | * | |
1399 | * When !@ptrace: | |
1400 | * | |
1401 | * If WEXITED is set, notask_error should naturally be | |
1402 | * cleared. If not, subset of WSTOPPED|WCONTINUED is set, | |
1403 | * so, if there are live subthreads, there are events to | |
1404 | * wait for. If all subthreads are dead, it's still safe | |
1405 | * to clear - this function will be called again in finite | |
1406 | * amount time once all the subthreads are released and | |
1407 | * will then return without clearing. | |
1408 | * | |
1409 | * When @ptrace: | |
1410 | * | |
1411 | * Stopped state is per-task and thus can't change once the | |
1412 | * target task dies. Only continued and exited can happen. | |
1413 | * Clear notask_error if WCONTINUED | WEXITED. | |
1414 | */ | |
1415 | if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED))) | |
1416 | wo->notask_error = 0; | |
1417 | } else { | |
1418 | /* | |
1419 | * @p is alive and it's gonna stop, continue or exit, so | |
1420 | * there always is something to wait for. | |
1421 | */ | |
1422 | wo->notask_error = 0; | |
1423 | } | |
1424 | ||
1425 | /* | |
1426 | * Wait for stopped. Depending on @ptrace, different stopped state | |
1427 | * is used and the two don't interact with each other. | |
1428 | */ | |
1429 | ret = wait_task_stopped(wo, ptrace, p); | |
1430 | if (ret) | |
1431 | return ret; | |
1432 | ||
1433 | /* | |
1434 | * Wait for continued. There's only one continued state and the | |
1435 | * ptracer can consume it which can confuse the real parent. Don't | |
1436 | * use WCONTINUED from ptracer. You don't need or want it. | |
1437 | */ | |
1438 | return wait_task_continued(wo, p); | |
1439 | } | |
1440 | ||
1441 | /* | |
1442 | * Do the work of do_wait() for one thread in the group, @tsk. | |
1443 | * | |
1444 | * -ECHILD should be in ->notask_error before the first call. | |
1445 | * Returns nonzero for a final return, when we have unlocked tasklist_lock. | |
1446 | * Returns zero if the search for a child should continue; then | |
1447 | * ->notask_error is 0 if there were any eligible children, | |
1448 | * or still -ECHILD. | |
1449 | */ | |
1450 | static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk) | |
1451 | { | |
1452 | struct task_struct *p; | |
1453 | ||
1454 | list_for_each_entry(p, &tsk->children, sibling) { | |
1455 | int ret = wait_consider_task(wo, 0, p); | |
1456 | ||
1457 | if (ret) | |
1458 | return ret; | |
1459 | } | |
1460 | ||
1461 | return 0; | |
1462 | } | |
1463 | ||
1464 | static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk) | |
1465 | { | |
1466 | struct task_struct *p; | |
1467 | ||
1468 | list_for_each_entry(p, &tsk->ptraced, ptrace_entry) { | |
1469 | int ret = wait_consider_task(wo, 1, p); | |
1470 | ||
1471 | if (ret) | |
1472 | return ret; | |
1473 | } | |
1474 | ||
1475 | return 0; | |
1476 | } | |
1477 | ||
1478 | static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode, | |
1479 | int sync, void *key) | |
1480 | { | |
1481 | struct wait_opts *wo = container_of(wait, struct wait_opts, | |
1482 | child_wait); | |
1483 | struct task_struct *p = key; | |
1484 | ||
1485 | if (!eligible_pid(wo, p)) | |
1486 | return 0; | |
1487 | ||
1488 | if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent) | |
1489 | return 0; | |
1490 | ||
1491 | return default_wake_function(wait, mode, sync, key); | |
1492 | } | |
1493 | ||
1494 | void __wake_up_parent(struct task_struct *p, struct task_struct *parent) | |
1495 | { | |
1496 | __wake_up_sync_key(&parent->signal->wait_chldexit, | |
1497 | TASK_INTERRUPTIBLE, 1, p); | |
1498 | } | |
1499 | ||
1500 | static long do_wait(struct wait_opts *wo) | |
1501 | { | |
1502 | struct task_struct *tsk; | |
1503 | int retval; | |
1504 | ||
1505 | trace_sched_process_wait(wo->wo_pid); | |
1506 | ||
1507 | init_waitqueue_func_entry(&wo->child_wait, child_wait_callback); | |
1508 | wo->child_wait.private = current; | |
1509 | add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); | |
1510 | repeat: | |
1511 | /* | |
1512 | * If there is nothing that can match our criteria, just get out. | |
1513 | * We will clear ->notask_error to zero if we see any child that | |
1514 | * might later match our criteria, even if we are not able to reap | |
1515 | * it yet. | |
1516 | */ | |
1517 | wo->notask_error = -ECHILD; | |
1518 | if ((wo->wo_type < PIDTYPE_MAX) && | |
1519 | (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type]))) | |
1520 | goto notask; | |
1521 | ||
1522 | set_current_state(TASK_INTERRUPTIBLE); | |
1523 | read_lock(&tasklist_lock); | |
1524 | tsk = current; | |
1525 | do { | |
1526 | retval = do_wait_thread(wo, tsk); | |
1527 | if (retval) | |
1528 | goto end; | |
1529 | ||
1530 | retval = ptrace_do_wait(wo, tsk); | |
1531 | if (retval) | |
1532 | goto end; | |
1533 | ||
1534 | if (wo->wo_flags & __WNOTHREAD) | |
1535 | break; | |
1536 | } while_each_thread(current, tsk); | |
1537 | read_unlock(&tasklist_lock); | |
1538 | ||
1539 | notask: | |
1540 | retval = wo->notask_error; | |
1541 | if (!retval && !(wo->wo_flags & WNOHANG)) { | |
1542 | retval = -ERESTARTSYS; | |
1543 | if (!signal_pending(current)) { | |
1544 | schedule(); | |
1545 | goto repeat; | |
1546 | } | |
1547 | } | |
1548 | end: | |
1549 | __set_current_state(TASK_RUNNING); | |
1550 | remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); | |
1551 | return retval; | |
1552 | } | |
1553 | ||
1554 | static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, | |
1555 | int options, struct rusage *ru) | |
1556 | { | |
1557 | struct wait_opts wo; | |
1558 | struct pid *pid = NULL; | |
1559 | enum pid_type type; | |
1560 | long ret; | |
1561 | ||
1562 | if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED| | |
1563 | __WNOTHREAD|__WCLONE|__WALL)) | |
1564 | return -EINVAL; | |
1565 | if (!(options & (WEXITED|WSTOPPED|WCONTINUED))) | |
1566 | return -EINVAL; | |
1567 | ||
1568 | switch (which) { | |
1569 | case P_ALL: | |
1570 | type = PIDTYPE_MAX; | |
1571 | break; | |
1572 | case P_PID: | |
1573 | type = PIDTYPE_PID; | |
1574 | if (upid <= 0) | |
1575 | return -EINVAL; | |
1576 | break; | |
1577 | case P_PGID: | |
1578 | type = PIDTYPE_PGID; | |
1579 | if (upid <= 0) | |
1580 | return -EINVAL; | |
1581 | break; | |
1582 | default: | |
1583 | return -EINVAL; | |
1584 | } | |
1585 | ||
1586 | if (type < PIDTYPE_MAX) | |
1587 | pid = find_get_pid(upid); | |
1588 | ||
1589 | wo.wo_type = type; | |
1590 | wo.wo_pid = pid; | |
1591 | wo.wo_flags = options; | |
1592 | wo.wo_info = infop; | |
1593 | wo.wo_rusage = ru; | |
1594 | ret = do_wait(&wo); | |
1595 | ||
1596 | put_pid(pid); | |
1597 | return ret; | |
1598 | } | |
1599 | ||
1600 | SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, | |
1601 | infop, int, options, struct rusage __user *, ru) | |
1602 | { | |
1603 | struct rusage r; | |
1604 | struct waitid_info info = {.status = 0}; | |
1605 | long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL); | |
1606 | int signo = 0; | |
1607 | ||
1608 | if (err > 0) { | |
1609 | signo = SIGCHLD; | |
1610 | err = 0; | |
1611 | if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) | |
1612 | return -EFAULT; | |
1613 | } | |
1614 | if (!infop) | |
1615 | return err; | |
1616 | ||
1617 | if (!user_access_begin(infop, sizeof(*infop))) | |
1618 | return -EFAULT; | |
1619 | ||
1620 | unsafe_put_user(signo, &infop->si_signo, Efault); | |
1621 | unsafe_put_user(0, &infop->si_errno, Efault); | |
1622 | unsafe_put_user(info.cause, &infop->si_code, Efault); | |
1623 | unsafe_put_user(info.pid, &infop->si_pid, Efault); | |
1624 | unsafe_put_user(info.uid, &infop->si_uid, Efault); | |
1625 | unsafe_put_user(info.status, &infop->si_status, Efault); | |
1626 | user_access_end(); | |
1627 | return err; | |
1628 | Efault: | |
1629 | user_access_end(); | |
1630 | return -EFAULT; | |
1631 | } | |
1632 | ||
1633 | long kernel_wait4(pid_t upid, int __user *stat_addr, int options, | |
1634 | struct rusage *ru) | |
1635 | { | |
1636 | struct wait_opts wo; | |
1637 | struct pid *pid = NULL; | |
1638 | enum pid_type type; | |
1639 | long ret; | |
1640 | ||
1641 | if (options & ~(WNOHANG|WUNTRACED|WCONTINUED| | |
1642 | __WNOTHREAD|__WCLONE|__WALL)) | |
1643 | return -EINVAL; | |
1644 | ||
1645 | /* -INT_MIN is not defined */ | |
1646 | if (upid == INT_MIN) | |
1647 | return -ESRCH; | |
1648 | ||
1649 | if (upid == -1) | |
1650 | type = PIDTYPE_MAX; | |
1651 | else if (upid < 0) { | |
1652 | type = PIDTYPE_PGID; | |
1653 | pid = find_get_pid(-upid); | |
1654 | } else if (upid == 0) { | |
1655 | type = PIDTYPE_PGID; | |
1656 | pid = get_task_pid(current, PIDTYPE_PGID); | |
1657 | } else /* upid > 0 */ { | |
1658 | type = PIDTYPE_PID; | |
1659 | pid = find_get_pid(upid); | |
1660 | } | |
1661 | ||
1662 | wo.wo_type = type; | |
1663 | wo.wo_pid = pid; | |
1664 | wo.wo_flags = options | WEXITED; | |
1665 | wo.wo_info = NULL; | |
1666 | wo.wo_stat = 0; | |
1667 | wo.wo_rusage = ru; | |
1668 | ret = do_wait(&wo); | |
1669 | put_pid(pid); | |
1670 | if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr)) | |
1671 | ret = -EFAULT; | |
1672 | ||
1673 | return ret; | |
1674 | } | |
1675 | ||
1676 | SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr, | |
1677 | int, options, struct rusage __user *, ru) | |
1678 | { | |
1679 | struct rusage r; | |
1680 | long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL); | |
1681 | ||
1682 | if (err > 0) { | |
1683 | if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) | |
1684 | return -EFAULT; | |
1685 | } | |
1686 | return err; | |
1687 | } | |
1688 | ||
1689 | #ifdef __ARCH_WANT_SYS_WAITPID | |
1690 | ||
1691 | /* | |
1692 | * sys_waitpid() remains for compatibility. waitpid() should be | |
1693 | * implemented by calling sys_wait4() from libc.a. | |
1694 | */ | |
1695 | SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options) | |
1696 | { | |
1697 | return kernel_wait4(pid, stat_addr, options, NULL); | |
1698 | } | |
1699 | ||
1700 | #endif | |
1701 | ||
1702 | #ifdef CONFIG_COMPAT | |
1703 | COMPAT_SYSCALL_DEFINE4(wait4, | |
1704 | compat_pid_t, pid, | |
1705 | compat_uint_t __user *, stat_addr, | |
1706 | int, options, | |
1707 | struct compat_rusage __user *, ru) | |
1708 | { | |
1709 | struct rusage r; | |
1710 | long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL); | |
1711 | if (err > 0) { | |
1712 | if (ru && put_compat_rusage(&r, ru)) | |
1713 | return -EFAULT; | |
1714 | } | |
1715 | return err; | |
1716 | } | |
1717 | ||
1718 | COMPAT_SYSCALL_DEFINE5(waitid, | |
1719 | int, which, compat_pid_t, pid, | |
1720 | struct compat_siginfo __user *, infop, int, options, | |
1721 | struct compat_rusage __user *, uru) | |
1722 | { | |
1723 | struct rusage ru; | |
1724 | struct waitid_info info = {.status = 0}; | |
1725 | long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL); | |
1726 | int signo = 0; | |
1727 | if (err > 0) { | |
1728 | signo = SIGCHLD; | |
1729 | err = 0; | |
1730 | if (uru) { | |
1731 | /* kernel_waitid() overwrites everything in ru */ | |
1732 | if (COMPAT_USE_64BIT_TIME) | |
1733 | err = copy_to_user(uru, &ru, sizeof(ru)); | |
1734 | else | |
1735 | err = put_compat_rusage(&ru, uru); | |
1736 | if (err) | |
1737 | return -EFAULT; | |
1738 | } | |
1739 | } | |
1740 | ||
1741 | if (!infop) | |
1742 | return err; | |
1743 | ||
1744 | if (!user_access_begin(infop, sizeof(*infop))) | |
1745 | return -EFAULT; | |
1746 | ||
1747 | unsafe_put_user(signo, &infop->si_signo, Efault); | |
1748 | unsafe_put_user(0, &infop->si_errno, Efault); | |
1749 | unsafe_put_user(info.cause, &infop->si_code, Efault); | |
1750 | unsafe_put_user(info.pid, &infop->si_pid, Efault); | |
1751 | unsafe_put_user(info.uid, &infop->si_uid, Efault); | |
1752 | unsafe_put_user(info.status, &infop->si_status, Efault); | |
1753 | user_access_end(); | |
1754 | return err; | |
1755 | Efault: | |
1756 | user_access_end(); | |
1757 | return -EFAULT; | |
1758 | } | |
1759 | #endif | |
1760 | ||
1761 | __weak void abort(void) | |
1762 | { | |
1763 | BUG(); | |
1764 | ||
1765 | /* if that doesn't kill us, halt */ | |
1766 | panic("Oops failed to kill thread"); | |
1767 | } | |
1768 | EXPORT_SYMBOL(abort); |