1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/kernel/exit.c
   4 *
   5 *  Copyright (C) 1991, 1992  Linus Torvalds
   6 */
   7
   8#include <linux/mm.h>
   9#include <linux/slab.h>
  10#include <linux/sched/autogroup.h>
  11#include <linux/sched/mm.h>
  12#include <linux/sched/stat.h>
  13#include <linux/sched/task.h>
  14#include <linux/sched/task_stack.h>
  15#include <linux/sched/cputime.h>
  16#include <linux/interrupt.h>
  17#include <linux/module.h>
  18#include <linux/capability.h>
  19#include <linux/completion.h>
  20#include <linux/personality.h>
  21#include <linux/tty.h>
  22#include <linux/iocontext.h>
  23#include <linux/key.h>
  24#include <linux/cpu.h>
  25#include <linux/acct.h>
  26#include <linux/tsacct_kern.h>
  27#include <linux/file.h>
  28#include <linux/fdtable.h>
  29#include <linux/freezer.h>
  30#include <linux/binfmts.h>
  31#include <linux/nsproxy.h>
  32#include <linux/pid_namespace.h>
  33#include <linux/ptrace.h>
  34#include <linux/profile.h>
  35#include <linux/mount.h>
  36#include <linux/proc_fs.h>
  37#include <linux/kthread.h>
  38#include <linux/mempolicy.h>
  39#include <linux/taskstats_kern.h>
  40#include <linux/delayacct.h>
  41#include <linux/cgroup.h>
  42#include <linux/syscalls.h>
  43#include <linux/signal.h>
  44#include <linux/posix-timers.h>
  45#include <linux/cn_proc.h>
  46#include <linux/mutex.h>
  47#include <linux/futex.h>
  48#include <linux/pipe_fs_i.h>
  49#include <linux/audit.h> /* for audit_free() */
  50#include <linux/resource.h>
  51#include <linux/blkdev.h>
  52#include <linux/task_io_accounting_ops.h>
  53#include <linux/tracehook.h>
  54#include <linux/fs_struct.h>
  55#include <linux/init_task.h>
  56#include <linux/perf_event.h>
  57#include <trace/events/sched.h>
  58#include <linux/hw_breakpoint.h>
  59#include <linux/oom.h>
  60#include <linux/writeback.h>
  61#include <linux/shm.h>
  62#include <linux/kcov.h>
  63#include <linux/random.h>
  64#include <linux/rcuwait.h>
  65#include <linux/compat.h>
  66
  67#include <linux/uaccess.h>
  68#include <asm/unistd.h>
  69#include <asm/pgtable.h>
  70#include <asm/mmu_context.h>
  71
  72static void __unhash_process(struct task_struct *p, bool group_dead)
  73{
  74	nr_threads--;
  75	detach_pid(p, PIDTYPE_PID);
  76	if (group_dead) {
  77		detach_pid(p, PIDTYPE_TGID);
  78		detach_pid(p, PIDTYPE_PGID);
  79		detach_pid(p, PIDTYPE_SID);
  80
  81		list_del_rcu(&p->tasks);
  82		list_del_init(&p->sibling);
  83		__this_cpu_dec(process_counts);
  84	}
  85	list_del_rcu(&p->thread_group);
  86	list_del_rcu(&p->thread_node);
  87}
  88
  89/*
  90 * This function expects the tasklist_lock write-locked.
  91 */
  92static void __exit_signal(struct task_struct *tsk)
  93{
  94	struct signal_struct *sig = tsk->signal;
  95	bool group_dead = thread_group_leader(tsk);
  96	struct sighand_struct *sighand;
  97	struct tty_struct *uninitialized_var(tty);
  98	u64 utime, stime;
  99
 100	sighand = rcu_dereference_check(tsk->sighand,
 101					lockdep_tasklist_lock_is_held());
 102	spin_lock(&sighand->siglock);
 103
 104#ifdef CONFIG_POSIX_TIMERS
 105	posix_cpu_timers_exit(tsk);
 106	if (group_dead) {
 107		posix_cpu_timers_exit_group(tsk);
 108	} else {
 109		/*
 110		 * This can only happen if the caller is de_thread().
 111		 * FIXME: this is the temporary hack, we should teach
 112		 * posix-cpu-timers to handle this case correctly.
 113		 */
 114		if (unlikely(has_group_leader_pid(tsk)))
 115			posix_cpu_timers_exit_group(tsk);
 116	}
 117#endif
 118
 119	if (group_dead) {
 120		tty = sig->tty;
 121		sig->tty = NULL;
 122	} else {
 123		/*
 124		 * If there is any task waiting for the group exit
 125		 * then notify it:
 126		 */
 127		if (sig->notify_count > 0 && !--sig->notify_count)
 128			wake_up_process(sig->group_exit_task);
 129
 130		if (tsk == sig->curr_target)
 131			sig->curr_target = next_thread(tsk);
 132	}
 133
 134	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
 135			      sizeof(unsigned long long));
 136
 137	/*
 138	 * Accumulate here the counters for all threads as they die. We could
 139	 * skip the group leader because it is the last user of signal_struct,
 140	 * but we want to avoid the race with thread_group_cputime() which can
 141	 * see the empty ->thread_head list.
 142	 */
 143	task_cputime(tsk, &utime, &stime);
 144	write_seqlock(&sig->stats_lock);
 145	sig->utime += utime;
 146	sig->stime += stime;
 147	sig->gtime += task_gtime(tsk);
 148	sig->min_flt += tsk->min_flt;
 149	sig->maj_flt += tsk->maj_flt;
 150	sig->nvcsw += tsk->nvcsw;
 151	sig->nivcsw += tsk->nivcsw;
 152	sig->inblock += task_io_get_inblock(tsk);
 153	sig->oublock += task_io_get_oublock(tsk);
 154	task_io_accounting_add(&sig->ioac, &tsk->ioac);
 155	sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 156	sig->nr_threads--;
 157	__unhash_process(tsk, group_dead);
 158	write_sequnlock(&sig->stats_lock);
 159
 160	/*
 161	 * Do this under ->siglock, we can race with another thread
 162	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 163	 */
 164	flush_sigqueue(&tsk->pending);
 165	tsk->sighand = NULL;
 166	spin_unlock(&sighand->siglock);
 167
 168	__cleanup_sighand(sighand);
 169	clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 170	if (group_dead) {
 171		flush_sigqueue(&sig->shared_pending);
 172		tty_kref_put(tty);
 173	}
 174}
 175
 176static void delayed_put_task_struct(struct rcu_head *rhp)
 177{
 178	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 179
 180	perf_event_delayed_put(tsk);
 181	trace_sched_process_free(tsk);
 182	put_task_struct(tsk);
 183}
 184
 185void put_task_struct_rcu_user(struct task_struct *task)
 186{
 187	if (refcount_dec_and_test(&task->rcu_users))
 188		call_rcu(&task->rcu, delayed_put_task_struct);
 189}
 190
 191void release_task(struct task_struct *p)
 192{
 193	struct task_struct *leader;
 194	int zap_leader;
 195repeat:
 196	/* don't need to get the RCU readlock here - the process is dead and
 197	 * can't be modifying its own credentials. But shut RCU-lockdep up */
 198	rcu_read_lock();
 199	atomic_dec(&__task_cred(p)->user->processes);
 200	rcu_read_unlock();
 201
 202	proc_flush_task(p);
 203	cgroup_release(p);
 204
 205	write_lock_irq(&tasklist_lock);
 206	ptrace_release_task(p);
 207	__exit_signal(p);
 208
 209	/*
 210	 * If we are the last non-leader member of the thread
 211	 * group, and the leader is zombie, then notify the
 212	 * group leader's parent process. (if it wants notification.)
 213	 */
 214	zap_leader = 0;
 215	leader = p->group_leader;
 216	if (leader != p && thread_group_empty(leader)
 217			&& leader->exit_state == EXIT_ZOMBIE) {
 218		/*
 219		 * If we were the last child thread and the leader has
 220		 * exited already, and the leader's parent ignores SIGCHLD,
 221		 * then we are the one who should release the leader.
 222		 */
 223		zap_leader = do_notify_parent(leader, leader->exit_signal);
 224		if (zap_leader)
 225			leader->exit_state = EXIT_DEAD;
 226	}
 227
 228	write_unlock_irq(&tasklist_lock);
 229	release_thread(p);
 230	put_task_struct_rcu_user(p);
 231
 232	p = leader;
 233	if (unlikely(zap_leader))
 234		goto repeat;
 235}
 236
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 237void rcuwait_wake_up(struct rcuwait *w)
 238{
 239	struct task_struct *task;
 240
 241	rcu_read_lock();
 242
 243	/*
 244	 * Order condition vs @task, such that everything prior to the load
 245	 * of @task is visible. This is the condition as to why the user called
 246	 * rcuwait_trywake() in the first place. Pairs with set_current_state()
 247	 * barrier (A) in rcuwait_wait_event().
 248	 *
 249	 *    WAIT                WAKE
 250	 *    [S] tsk = current	  [S] cond = true
 251	 *        MB (A)	      MB (B)
 252	 *    [L] cond		  [L] tsk
 253	 */
 254	smp_mb(); /* (B) */
 255
 
 
 
 
 256	task = rcu_dereference(w->task);
 257	if (task)
 258		wake_up_process(task);
 259	rcu_read_unlock();
 260}
 261
 262/*
 263 * Determine if a process group is "orphaned", according to the POSIX
 264 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 265 * by terminal-generated stop signals.  Newly orphaned process groups are
 266 * to receive a SIGHUP and a SIGCONT.
 267 *
 268 * "I ask you, have you ever known what it is to be an orphan?"
 269 */
 270static int will_become_orphaned_pgrp(struct pid *pgrp,
 271					struct task_struct *ignored_task)
 272{
 273	struct task_struct *p;
 274
 275	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 276		if ((p == ignored_task) ||
 277		    (p->exit_state && thread_group_empty(p)) ||
 278		    is_global_init(p->real_parent))
 279			continue;
 280
 281		if (task_pgrp(p->real_parent) != pgrp &&
 282		    task_session(p->real_parent) == task_session(p))
 283			return 0;
 284	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 285
 286	return 1;
 287}
 288
 289int is_current_pgrp_orphaned(void)
 290{
 291	int retval;
 292
 293	read_lock(&tasklist_lock);
 294	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 295	read_unlock(&tasklist_lock);
 296
 297	return retval;
 298}
 299
 300static bool has_stopped_jobs(struct pid *pgrp)
 301{
 302	struct task_struct *p;
 303
 304	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 305		if (p->signal->flags & SIGNAL_STOP_STOPPED)
 306			return true;
 307	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 308
 309	return false;
 310}
 311
 312/*
 313 * Check to see if any process groups have become orphaned as
 314 * a result of our exiting, and if they have any stopped jobs,
 315 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 316 */
 317static void
 318kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 319{
 320	struct pid *pgrp = task_pgrp(tsk);
 321	struct task_struct *ignored_task = tsk;
 322
 323	if (!parent)
 324		/* exit: our father is in a different pgrp than
 325		 * we are and we were the only connection outside.
 326		 */
 327		parent = tsk->real_parent;
 328	else
 329		/* reparent: our child is in a different pgrp than
 330		 * we are, and it was the only connection outside.
 331		 */
 332		ignored_task = NULL;
 333
 334	if (task_pgrp(parent) != pgrp &&
 335	    task_session(parent) == task_session(tsk) &&
 336	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
 337	    has_stopped_jobs(pgrp)) {
 338		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 339		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 340	}
 341}
 342
 343#ifdef CONFIG_MEMCG
 344/*
 345 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 346 */
 347void mm_update_next_owner(struct mm_struct *mm)
 348{
 349	struct task_struct *c, *g, *p = current;
 350
 351retry:
 352	/*
 353	 * If the exiting or execing task is not the owner, it's
 354	 * someone else's problem.
 355	 */
 356	if (mm->owner != p)
 357		return;
 358	/*
 359	 * The current owner is exiting/execing and there are no other
 360	 * candidates.  Do not leave the mm pointing to a possibly
 361	 * freed task structure.
 362	 */
 363	if (atomic_read(&mm->mm_users) <= 1) {
 364		WRITE_ONCE(mm->owner, NULL);
 365		return;
 366	}
 367
 368	read_lock(&tasklist_lock);
 369	/*
 370	 * Search in the children
 371	 */
 372	list_for_each_entry(c, &p->children, sibling) {
 373		if (c->mm == mm)
 374			goto assign_new_owner;
 375	}
 376
 377	/*
 378	 * Search in the siblings
 379	 */
 380	list_for_each_entry(c, &p->real_parent->children, sibling) {
 381		if (c->mm == mm)
 382			goto assign_new_owner;
 383	}
 384
 385	/*
 386	 * Search through everything else, we should not get here often.
 387	 */
 388	for_each_process(g) {
 389		if (g->flags & PF_KTHREAD)
 390			continue;
 391		for_each_thread(g, c) {
 392			if (c->mm == mm)
 393				goto assign_new_owner;
 394			if (c->mm)
 395				break;
 396		}
 397	}
 398	read_unlock(&tasklist_lock);
 399	/*
 400	 * We found no owner yet mm_users > 1: this implies that we are
 401	 * most likely racing with swapoff (try_to_unuse()) or /proc or
 402	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 403	 */
 404	WRITE_ONCE(mm->owner, NULL);
 405	return;
 406
 407assign_new_owner:
 408	BUG_ON(c == p);
 409	get_task_struct(c);
 410	/*
 411	 * The task_lock protects c->mm from changing.
 412	 * We always want mm->owner->mm == mm
 413	 */
 414	task_lock(c);
 415	/*
 416	 * Delay read_unlock() till we have the task_lock()
 417	 * to ensure that c does not slip away underneath us
 418	 */
 419	read_unlock(&tasklist_lock);
 420	if (c->mm != mm) {
 421		task_unlock(c);
 422		put_task_struct(c);
 423		goto retry;
 424	}
 425	WRITE_ONCE(mm->owner, c);
 426	task_unlock(c);
 427	put_task_struct(c);
 428}
 429#endif /* CONFIG_MEMCG */
 430
 431/*
 432 * Turn us into a lazy TLB process if we
 433 * aren't already..
 434 */
 435static void exit_mm(void)
 436{
 437	struct mm_struct *mm = current->mm;
 438	struct core_state *core_state;
 439
 440	mm_release(current, mm);
 441	if (!mm)
 442		return;
 443	sync_mm_rss(mm);
 444	/*
 445	 * Serialize with any possible pending coredump.
 446	 * We must hold mmap_sem around checking core_state
 447	 * and clearing tsk->mm.  The core-inducing thread
 448	 * will increment ->nr_threads for each thread in the
 449	 * group with ->mm != NULL.
 450	 */
 451	down_read(&mm->mmap_sem);
 452	core_state = mm->core_state;
 453	if (core_state) {
 454		struct core_thread self;
 455
 456		up_read(&mm->mmap_sem);
 457
 458		self.task = current;
 459		self.next = xchg(&core_state->dumper.next, &self);
 460		/*
 461		 * Implies mb(), the result of xchg() must be visible
 462		 * to core_state->dumper.
 463		 */
 464		if (atomic_dec_and_test(&core_state->nr_threads))
 465			complete(&core_state->startup);
 466
 467		for (;;) {
 468			set_current_state(TASK_UNINTERRUPTIBLE);
 469			if (!self.task) /* see coredump_finish() */
 470				break;
 471			freezable_schedule();
 472		}
 473		__set_current_state(TASK_RUNNING);
 474		down_read(&mm->mmap_sem);
 475	}
 476	mmgrab(mm);
 477	BUG_ON(mm != current->active_mm);
 478	/* more a memory barrier than a real lock */
 479	task_lock(current);
 480	current->mm = NULL;
 481	up_read(&mm->mmap_sem);
 482	enter_lazy_tlb(mm, current);
 483	task_unlock(current);
 484	mm_update_next_owner(mm);
 485	mmput(mm);
 486	if (test_thread_flag(TIF_MEMDIE))
 487		exit_oom_victim();
 488}
 489
 490static struct task_struct *find_alive_thread(struct task_struct *p)
 491{
 492	struct task_struct *t;
 493
 494	for_each_thread(p, t) {
 495		if (!(t->flags & PF_EXITING))
 496			return t;
 497	}
 498	return NULL;
 499}
 500
 501static struct task_struct *find_child_reaper(struct task_struct *father,
 502						struct list_head *dead)
 503	__releases(&tasklist_lock)
 504	__acquires(&tasklist_lock)
 505{
 506	struct pid_namespace *pid_ns = task_active_pid_ns(father);
 507	struct task_struct *reaper = pid_ns->child_reaper;
 508	struct task_struct *p, *n;
 509
 510	if (likely(reaper != father))
 511		return reaper;
 512
 513	reaper = find_alive_thread(father);
 514	if (reaper) {
 515		pid_ns->child_reaper = reaper;
 516		return reaper;
 517	}
 518
 519	write_unlock_irq(&tasklist_lock);
 520	if (unlikely(pid_ns == &init_pid_ns)) {
 521		panic("Attempted to kill init! exitcode=0x%08x\n",
 522			father->signal->group_exit_code ?: father->exit_code);
 523	}
 524
 525	list_for_each_entry_safe(p, n, dead, ptrace_entry) {
 526		list_del_init(&p->ptrace_entry);
 527		release_task(p);
 528	}
 529
 530	zap_pid_ns_processes(pid_ns);
 531	write_lock_irq(&tasklist_lock);
 532
 533	return father;
 534}
 535
 536/*
 537 * When we die, we re-parent all our children, and try to:
 538 * 1. give them to another thread in our thread group, if such a member exists
 539 * 2. give it to the first ancestor process which prctl'd itself as a
 540 *    child_subreaper for its children (like a service manager)
 541 * 3. give it to the init process (PID 1) in our pid namespace
 542 */
 543static struct task_struct *find_new_reaper(struct task_struct *father,
 544					   struct task_struct *child_reaper)
 545{
 546	struct task_struct *thread, *reaper;
 547
 548	thread = find_alive_thread(father);
 549	if (thread)
 550		return thread;
 551
 552	if (father->signal->has_child_subreaper) {
 553		unsigned int ns_level = task_pid(father)->level;
 554		/*
 555		 * Find the first ->is_child_subreaper ancestor in our pid_ns.
 556		 * We can't check reaper != child_reaper to ensure we do not
 557		 * cross the namespaces, the exiting parent could be injected
 558		 * by setns() + fork().
 559		 * We check pid->level, this is slightly more efficient than
 560		 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
 561		 */
 562		for (reaper = father->real_parent;
 563		     task_pid(reaper)->level == ns_level;
 564		     reaper = reaper->real_parent) {
 565			if (reaper == &init_task)
 566				break;
 567			if (!reaper->signal->is_child_subreaper)
 568				continue;
 569			thread = find_alive_thread(reaper);
 570			if (thread)
 571				return thread;
 572		}
 573	}
 574
 575	return child_reaper;
 576}
 577
 578/*
 579* Any that need to be release_task'd are put on the @dead list.
 580 */
 581static void reparent_leader(struct task_struct *father, struct task_struct *p,
 582				struct list_head *dead)
 583{
 584	if (unlikely(p->exit_state == EXIT_DEAD))
 585		return;
 586
 587	/* We don't want people slaying init. */
 588	p->exit_signal = SIGCHLD;
 589
 590	/* If it has exited notify the new parent about this child's death. */
 591	if (!p->ptrace &&
 592	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 593		if (do_notify_parent(p, p->exit_signal)) {
 594			p->exit_state = EXIT_DEAD;
 595			list_add(&p->ptrace_entry, dead);
 596		}
 597	}
 598
 599	kill_orphaned_pgrp(p, father);
 600}
 601
 602/*
 603 * This does two things:
 604 *
 605 * A.  Make init inherit all the child processes
 606 * B.  Check to see if any process groups have become orphaned
 607 *	as a result of our exiting, and if they have any stopped
 608 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 609 */
 610static void forget_original_parent(struct task_struct *father,
 611					struct list_head *dead)
 612{
 613	struct task_struct *p, *t, *reaper;
 614
 615	if (unlikely(!list_empty(&father->ptraced)))
 616		exit_ptrace(father, dead);
 617
 618	/* Can drop and reacquire tasklist_lock */
 619	reaper = find_child_reaper(father, dead);
 620	if (list_empty(&father->children))
 621		return;
 622
 623	reaper = find_new_reaper(father, reaper);
 624	list_for_each_entry(p, &father->children, sibling) {
 625		for_each_thread(p, t) {
 626			t->real_parent = reaper;
 627			BUG_ON((!t->ptrace) != (t->parent == father));
 628			if (likely(!t->ptrace))
 629				t->parent = t->real_parent;
 630			if (t->pdeath_signal)
 631				group_send_sig_info(t->pdeath_signal,
 632						    SEND_SIG_NOINFO, t,
 633						    PIDTYPE_TGID);
 634		}
 635		/*
 636		 * If this is a threaded reparent there is no need to
 637		 * notify anyone anything has happened.
 638		 */
 639		if (!same_thread_group(reaper, father))
 640			reparent_leader(father, p, dead);
 641	}
 642	list_splice_tail_init(&father->children, &reaper->children);
 643}
 644
 645/*
 646 * Send signals to all our closest relatives so that they know
 647 * to properly mourn us..
 648 */
 649static void exit_notify(struct task_struct *tsk, int group_dead)
 650{
 651	bool autoreap;
 652	struct task_struct *p, *n;
 653	LIST_HEAD(dead);
 654
 655	write_lock_irq(&tasklist_lock);
 656	forget_original_parent(tsk, &dead);
 657
 658	if (group_dead)
 659		kill_orphaned_pgrp(tsk->group_leader, NULL);
 660
 661	tsk->exit_state = EXIT_ZOMBIE;
 662	if (unlikely(tsk->ptrace)) {
 663		int sig = thread_group_leader(tsk) &&
 664				thread_group_empty(tsk) &&
 665				!ptrace_reparented(tsk) ?
 666			tsk->exit_signal : SIGCHLD;
 667		autoreap = do_notify_parent(tsk, sig);
 668	} else if (thread_group_leader(tsk)) {
 669		autoreap = thread_group_empty(tsk) &&
 670			do_notify_parent(tsk, tsk->exit_signal);
 671	} else {
 672		autoreap = true;
 673	}
 674
 675	if (autoreap) {
 676		tsk->exit_state = EXIT_DEAD;
 677		list_add(&tsk->ptrace_entry, &dead);
 678	}
 679
 680	/* mt-exec, de_thread() is waiting for group leader */
 681	if (unlikely(tsk->signal->notify_count < 0))
 682		wake_up_process(tsk->signal->group_exit_task);
 683	write_unlock_irq(&tasklist_lock);
 684
 685	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
 686		list_del_init(&p->ptrace_entry);
 687		release_task(p);
 688	}
 689}
 690
 691#ifdef CONFIG_DEBUG_STACK_USAGE
 692static void check_stack_usage(void)
 693{
 694	static DEFINE_SPINLOCK(low_water_lock);
 695	static int lowest_to_date = THREAD_SIZE;
 696	unsigned long free;
 697
 698	free = stack_not_used(current);
 699
 700	if (free >= lowest_to_date)
 701		return;
 702
 703	spin_lock(&low_water_lock);
 704	if (free < lowest_to_date) {
 705		pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
 706			current->comm, task_pid_nr(current), free);
 707		lowest_to_date = free;
 708	}
 709	spin_unlock(&low_water_lock);
 710}
 711#else
 712static inline void check_stack_usage(void) {}
 713#endif
 714
 715void __noreturn do_exit(long code)
 716{
 717	struct task_struct *tsk = current;
 718	int group_dead;
 719
 720	profile_task_exit(tsk);
 721	kcov_task_exit(tsk);
 722
 723	WARN_ON(blk_needs_flush_plug(tsk));
 724
 725	if (unlikely(in_interrupt()))
 726		panic("Aiee, killing interrupt handler!");
 727	if (unlikely(!tsk->pid))
 728		panic("Attempted to kill the idle task!");
 729
 730	/*
 731	 * If do_exit is called because this processes oopsed, it's possible
 732	 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
 733	 * continuing. Amongst other possible reasons, this is to prevent
 734	 * mm_release()->clear_child_tid() from writing to a user-controlled
 735	 * kernel address.
 736	 */
 737	set_fs(USER_DS);
 738
 739	ptrace_event(PTRACE_EVENT_EXIT, code);
 740
 741	validate_creds_for_do_exit(tsk);
 742
 743	/*
 744	 * We're taking recursive faults here in do_exit. Safest is to just
 745	 * leave this task alone and wait for reboot.
 746	 */
 747	if (unlikely(tsk->flags & PF_EXITING)) {
 748		pr_alert("Fixing recursive fault but reboot is needed!\n");
 749		/*
 750		 * We can do this unlocked here. The futex code uses
 751		 * this flag just to verify whether the pi state
 752		 * cleanup has been done or not. In the worst case it
 753		 * loops once more. We pretend that the cleanup was
 754		 * done as there is no way to return. Either the
 755		 * OWNER_DIED bit is set by now or we push the blocked
 756		 * task into the wait for ever nirwana as well.
 757		 */
 758		tsk->flags |= PF_EXITPIDONE;
 759		set_current_state(TASK_UNINTERRUPTIBLE);
 760		schedule();
 761	}
 762
 763	exit_signals(tsk);  /* sets PF_EXITING */
 764	/*
 765	 * Ensure that all new tsk->pi_lock acquisitions must observe
 766	 * PF_EXITING. Serializes against futex.c:attach_to_pi_owner().
 767	 */
 768	smp_mb();
 769	/*
 770	 * Ensure that we must observe the pi_state in exit_mm() ->
 771	 * mm_release() -> exit_pi_state_list().
 772	 */
 773	raw_spin_lock_irq(&tsk->pi_lock);
 774	raw_spin_unlock_irq(&tsk->pi_lock);
 775
 776	if (unlikely(in_atomic())) {
 777		pr_info("note: %s[%d] exited with preempt_count %d\n",
 778			current->comm, task_pid_nr(current),
 779			preempt_count());
 780		preempt_count_set(PREEMPT_ENABLED);
 781	}
 782
 783	/* sync mm's RSS info before statistics gathering */
 784	if (tsk->mm)
 785		sync_mm_rss(tsk->mm);
 786	acct_update_integrals(tsk);
 787	group_dead = atomic_dec_and_test(&tsk->signal->live);
 788	if (group_dead) {
 789#ifdef CONFIG_POSIX_TIMERS
 790		hrtimer_cancel(&tsk->signal->real_timer);
 791		exit_itimers(tsk->signal);
 792#endif
 793		if (tsk->mm)
 794			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
 795	}
 796	acct_collect(code, group_dead);
 797	if (group_dead)
 798		tty_audit_exit();
 799	audit_free(tsk);
 800
 801	tsk->exit_code = code;
 802	taskstats_exit(tsk, group_dead);
 803
 804	exit_mm();
 805
 806	if (group_dead)
 807		acct_process();
 808	trace_sched_process_exit(tsk);
 809
 810	exit_sem(tsk);
 811	exit_shm(tsk);
 812	exit_files(tsk);
 813	exit_fs(tsk);
 814	if (group_dead)
 815		disassociate_ctty(1);
 816	exit_task_namespaces(tsk);
 817	exit_task_work(tsk);
 818	exit_thread(tsk);
 819	exit_umh(tsk);
 820
 821	/*
 822	 * Flush inherited counters to the parent - before the parent
 823	 * gets woken up by child-exit notifications.
 824	 *
 825	 * because of cgroup mode, must be called before cgroup_exit()
 826	 */
 827	perf_event_exit_task(tsk);
 828
 829	sched_autogroup_exit_task(tsk);
 830	cgroup_exit(tsk);
 831
 832	/*
 833	 * FIXME: do that only when needed, using sched_exit tracepoint
 834	 */
 835	flush_ptrace_hw_breakpoint(tsk);
 836
 837	exit_tasks_rcu_start();
 838	exit_notify(tsk, group_dead);
 839	proc_exit_connector(tsk);
 840	mpol_put_task_policy(tsk);
 841#ifdef CONFIG_FUTEX
 842	if (unlikely(current->pi_state_cache))
 843		kfree(current->pi_state_cache);
 844#endif
 845	/*
 846	 * Make sure we are holding no locks:
 847	 */
 848	debug_check_no_locks_held();
 849	/*
 850	 * We can do this unlocked here. The futex code uses this flag
 851	 * just to verify whether the pi state cleanup has been done
 852	 * or not. In the worst case it loops once more.
 853	 */
 854	tsk->flags |= PF_EXITPIDONE;
 855
 856	if (tsk->io_context)
 857		exit_io_context(tsk);
 858
 859	if (tsk->splice_pipe)
 860		free_pipe_info(tsk->splice_pipe);
 861
 862	if (tsk->task_frag.page)
 863		put_page(tsk->task_frag.page);
 864
 865	validate_creds_for_do_exit(tsk);
 866
 867	check_stack_usage();
 868	preempt_disable();
 869	if (tsk->nr_dirtied)
 870		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
 871	exit_rcu();
 872	exit_tasks_rcu_finish();
 873
 874	lockdep_free_task(tsk);
 875	do_task_dead();
 876}
 877EXPORT_SYMBOL_GPL(do_exit);
 878
 879void complete_and_exit(struct completion *comp, long code)
 880{
 881	if (comp)
 882		complete(comp);
 883
 884	do_exit(code);
 885}
 886EXPORT_SYMBOL(complete_and_exit);
 887
 888SYSCALL_DEFINE1(exit, int, error_code)
 889{
 890	do_exit((error_code&0xff)<<8);
 891}
 892
 893/*
 894 * Take down every thread in the group.  This is called by fatal signals
 895 * as well as by sys_exit_group (below).
 896 */
 897void
 898do_group_exit(int exit_code)
 899{
 900	struct signal_struct *sig = current->signal;
 901
 902	BUG_ON(exit_code & 0x80); /* core dumps don't get here */
 903
 904	if (signal_group_exit(sig))
 905		exit_code = sig->group_exit_code;
 906	else if (!thread_group_empty(current)) {
 907		struct sighand_struct *const sighand = current->sighand;
 908
 909		spin_lock_irq(&sighand->siglock);
 910		if (signal_group_exit(sig))
 911			/* Another thread got here before we took the lock.  */
 912			exit_code = sig->group_exit_code;
 913		else {
 914			sig->group_exit_code = exit_code;
 915			sig->flags = SIGNAL_GROUP_EXIT;
 916			zap_other_threads(current);
 917		}
 918		spin_unlock_irq(&sighand->siglock);
 919	}
 920
 921	do_exit(exit_code);
 922	/* NOTREACHED */
 923}
 924
 925/*
 926 * this kills every thread in the thread group. Note that any externally
 927 * wait4()-ing process will get the correct exit code - even if this
 928 * thread is not the thread group leader.
 929 */
 930SYSCALL_DEFINE1(exit_group, int, error_code)
 931{
 932	do_group_exit((error_code & 0xff) << 8);
 933	/* NOTREACHED */
 934	return 0;
 935}
 936
 937struct waitid_info {
 938	pid_t pid;
 939	uid_t uid;
 940	int status;
 941	int cause;
 942};
 943
 944struct wait_opts {
 945	enum pid_type		wo_type;
 946	int			wo_flags;
 947	struct pid		*wo_pid;
 948
 949	struct waitid_info	*wo_info;
 950	int			wo_stat;
 951	struct rusage		*wo_rusage;
 952
 953	wait_queue_entry_t		child_wait;
 954	int			notask_error;
 955};
 956
 
 
 
 
 
 
 
 
 957static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
 958{
 959	return	wo->wo_type == PIDTYPE_MAX ||
 960		task_pid_type(p, wo->wo_type) == wo->wo_pid;
 961}
 962
 963static int
 964eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
 965{
 966	if (!eligible_pid(wo, p))
 967		return 0;
 968
 969	/*
 970	 * Wait for all children (clone and not) if __WALL is set or
 971	 * if it is traced by us.
 972	 */
 973	if (ptrace || (wo->wo_flags & __WALL))
 974		return 1;
 975
 976	/*
 977	 * Otherwise, wait for clone children *only* if __WCLONE is set;
 978	 * otherwise, wait for non-clone children *only*.
 979	 *
 980	 * Note: a "clone" child here is one that reports to its parent
 981	 * using a signal other than SIGCHLD, or a non-leader thread which
 982	 * we can only see if it is traced by us.
 983	 */
 984	if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
 985		return 0;
 986
 987	return 1;
 988}
 989
 990/*
 991 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
 992 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
 993 * the lock and this task is uninteresting.  If we return nonzero, we have
 994 * released the lock and the system call should return.
 995 */
 996static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 997{
 998	int state, status;
 999	pid_t pid = task_pid_vnr(p);
1000	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1001	struct waitid_info *infop;
1002
1003	if (!likely(wo->wo_flags & WEXITED))
1004		return 0;
1005
1006	if (unlikely(wo->wo_flags & WNOWAIT)) {
1007		status = p->exit_code;
1008		get_task_struct(p);
1009		read_unlock(&tasklist_lock);
1010		sched_annotate_sleep();
1011		if (wo->wo_rusage)
1012			getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1013		put_task_struct(p);
1014		goto out_info;
1015	}
1016	/*
1017	 * Move the task's state to DEAD/TRACE, only one thread can do this.
1018	 */
1019	state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1020		EXIT_TRACE : EXIT_DEAD;
1021	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1022		return 0;
1023	/*
1024	 * We own this thread, nobody else can reap it.
1025	 */
1026	read_unlock(&tasklist_lock);
1027	sched_annotate_sleep();
1028
1029	/*
1030	 * Check thread_group_leader() to exclude the traced sub-threads.
1031	 */
1032	if (state == EXIT_DEAD && thread_group_leader(p)) {
1033		struct signal_struct *sig = p->signal;
1034		struct signal_struct *psig = current->signal;
1035		unsigned long maxrss;
1036		u64 tgutime, tgstime;
1037
1038		/*
1039		 * The resource counters for the group leader are in its
1040		 * own task_struct.  Those for dead threads in the group
1041		 * are in its signal_struct, as are those for the child
1042		 * processes it has previously reaped.  All these
1043		 * accumulate in the parent's signal_struct c* fields.
1044		 *
1045		 * We don't bother to take a lock here to protect these
1046		 * p->signal fields because the whole thread group is dead
1047		 * and nobody can change them.
1048		 *
1049		 * psig->stats_lock also protects us from our sub-theads
1050		 * which can reap other children at the same time. Until
1051		 * we change k_getrusage()-like users to rely on this lock
1052		 * we have to take ->siglock as well.
1053		 *
1054		 * We use thread_group_cputime_adjusted() to get times for
1055		 * the thread group, which consolidates times for all threads
1056		 * in the group including the group leader.
1057		 */
1058		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1059		spin_lock_irq(&current->sighand->siglock);
1060		write_seqlock(&psig->stats_lock);
1061		psig->cutime += tgutime + sig->cutime;
1062		psig->cstime += tgstime + sig->cstime;
1063		psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1064		psig->cmin_flt +=
1065			p->min_flt + sig->min_flt + sig->cmin_flt;
1066		psig->cmaj_flt +=
1067			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1068		psig->cnvcsw +=
1069			p->nvcsw + sig->nvcsw + sig->cnvcsw;
1070		psig->cnivcsw +=
1071			p->nivcsw + sig->nivcsw + sig->cnivcsw;
1072		psig->cinblock +=
1073			task_io_get_inblock(p) +
1074			sig->inblock + sig->cinblock;
1075		psig->coublock +=
1076			task_io_get_oublock(p) +
1077			sig->oublock + sig->coublock;
1078		maxrss = max(sig->maxrss, sig->cmaxrss);
1079		if (psig->cmaxrss < maxrss)
1080			psig->cmaxrss = maxrss;
1081		task_io_accounting_add(&psig->ioac, &p->ioac);
1082		task_io_accounting_add(&psig->ioac, &sig->ioac);
1083		write_sequnlock(&psig->stats_lock);
1084		spin_unlock_irq(&current->sighand->siglock);
1085	}
1086
1087	if (wo->wo_rusage)
1088		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1089	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1090		? p->signal->group_exit_code : p->exit_code;
1091	wo->wo_stat = status;
1092
1093	if (state == EXIT_TRACE) {
1094		write_lock_irq(&tasklist_lock);
1095		/* We dropped tasklist, ptracer could die and untrace */
1096		ptrace_unlink(p);
1097
1098		/* If parent wants a zombie, don't release it now */
1099		state = EXIT_ZOMBIE;
1100		if (do_notify_parent(p, p->exit_signal))
1101			state = EXIT_DEAD;
1102		p->exit_state = state;
1103		write_unlock_irq(&tasklist_lock);
1104	}
1105	if (state == EXIT_DEAD)
1106		release_task(p);
1107
1108out_info:
1109	infop = wo->wo_info;
1110	if (infop) {
1111		if ((status & 0x7f) == 0) {
1112			infop->cause = CLD_EXITED;
1113			infop->status = status >> 8;
1114		} else {
1115			infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1116			infop->status = status & 0x7f;
1117		}
1118		infop->pid = pid;
1119		infop->uid = uid;
1120	}
1121
1122	return pid;
1123}
1124
1125static int *task_stopped_code(struct task_struct *p, bool ptrace)
1126{
1127	if (ptrace) {
1128		if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1129			return &p->exit_code;
1130	} else {
1131		if (p->signal->flags & SIGNAL_STOP_STOPPED)
1132			return &p->signal->group_exit_code;
1133	}
1134	return NULL;
1135}
1136
1137/**
1138 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1139 * @wo: wait options
1140 * @ptrace: is the wait for ptrace
1141 * @p: task to wait for
1142 *
1143 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1144 *
1145 * CONTEXT:
1146 * read_lock(&tasklist_lock), which is released if return value is
1147 * non-zero.  Also, grabs and releases @p->sighand->siglock.
1148 *
1149 * RETURNS:
1150 * 0 if wait condition didn't exist and search for other wait conditions
1151 * should continue.  Non-zero return, -errno on failure and @p's pid on
1152 * success, implies that tasklist_lock is released and wait condition
1153 * search should terminate.
1154 */
1155static int wait_task_stopped(struct wait_opts *wo,
1156				int ptrace, struct task_struct *p)
1157{
1158	struct waitid_info *infop;
1159	int exit_code, *p_code, why;
1160	uid_t uid = 0; /* unneeded, required by compiler */
1161	pid_t pid;
1162
1163	/*
1164	 * Traditionally we see ptrace'd stopped tasks regardless of options.
1165	 */
1166	if (!ptrace && !(wo->wo_flags & WUNTRACED))
1167		return 0;
1168
1169	if (!task_stopped_code(p, ptrace))
1170		return 0;
1171
1172	exit_code = 0;
1173	spin_lock_irq(&p->sighand->siglock);
1174
1175	p_code = task_stopped_code(p, ptrace);
1176	if (unlikely(!p_code))
1177		goto unlock_sig;
1178
1179	exit_code = *p_code;
1180	if (!exit_code)
1181		goto unlock_sig;
1182
1183	if (!unlikely(wo->wo_flags & WNOWAIT))
1184		*p_code = 0;
1185
1186	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1187unlock_sig:
1188	spin_unlock_irq(&p->sighand->siglock);
1189	if (!exit_code)
1190		return 0;
1191
1192	/*
1193	 * Now we are pretty sure this task is interesting.
1194	 * Make sure it doesn't get reaped out from under us while we
1195	 * give up the lock and then examine it below.  We don't want to
1196	 * keep holding onto the tasklist_lock while we call getrusage and
1197	 * possibly take page faults for user memory.
1198	 */
1199	get_task_struct(p);
1200	pid = task_pid_vnr(p);
1201	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1202	read_unlock(&tasklist_lock);
1203	sched_annotate_sleep();
1204	if (wo->wo_rusage)
1205		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1206	put_task_struct(p);
1207
1208	if (likely(!(wo->wo_flags & WNOWAIT)))
1209		wo->wo_stat = (exit_code << 8) | 0x7f;
1210
1211	infop = wo->wo_info;
1212	if (infop) {
1213		infop->cause = why;
1214		infop->status = exit_code;
1215		infop->pid = pid;
1216		infop->uid = uid;
1217	}
1218	return pid;
1219}
1220
1221/*
1222 * Handle do_wait work for one task in a live, non-stopped state.
1223 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1224 * the lock and this task is uninteresting.  If we return nonzero, we have
1225 * released the lock and the system call should return.
1226 */
1227static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1228{
1229	struct waitid_info *infop;
1230	pid_t pid;
1231	uid_t uid;
1232
1233	if (!unlikely(wo->wo_flags & WCONTINUED))
1234		return 0;
1235
1236	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1237		return 0;
1238
1239	spin_lock_irq(&p->sighand->siglock);
1240	/* Re-check with the lock held.  */
1241	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1242		spin_unlock_irq(&p->sighand->siglock);
1243		return 0;
1244	}
1245	if (!unlikely(wo->wo_flags & WNOWAIT))
1246		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1247	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1248	spin_unlock_irq(&p->sighand->siglock);
1249
1250	pid = task_pid_vnr(p);
1251	get_task_struct(p);
1252	read_unlock(&tasklist_lock);
1253	sched_annotate_sleep();
1254	if (wo->wo_rusage)
1255		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1256	put_task_struct(p);
1257
1258	infop = wo->wo_info;
1259	if (!infop) {
1260		wo->wo_stat = 0xffff;
1261	} else {
1262		infop->cause = CLD_CONTINUED;
1263		infop->pid = pid;
1264		infop->uid = uid;
1265		infop->status = SIGCONT;
1266	}
1267	return pid;
1268}
1269
1270/*
1271 * Consider @p for a wait by @parent.
1272 *
1273 * -ECHILD should be in ->notask_error before the first call.
1274 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1275 * Returns zero if the search for a child should continue;
1276 * then ->notask_error is 0 if @p is an eligible child,
1277 * or still -ECHILD.
1278 */
1279static int wait_consider_task(struct wait_opts *wo, int ptrace,
1280				struct task_struct *p)
1281{
1282	/*
1283	 * We can race with wait_task_zombie() from another thread.
1284	 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1285	 * can't confuse the checks below.
1286	 */
1287	int exit_state = READ_ONCE(p->exit_state);
1288	int ret;
1289
1290	if (unlikely(exit_state == EXIT_DEAD))
1291		return 0;
1292
1293	ret = eligible_child(wo, ptrace, p);
1294	if (!ret)
1295		return ret;
1296
1297	if (unlikely(exit_state == EXIT_TRACE)) {
1298		/*
1299		 * ptrace == 0 means we are the natural parent. In this case
1300		 * we should clear notask_error, debugger will notify us.
1301		 */
1302		if (likely(!ptrace))
1303			wo->notask_error = 0;
1304		return 0;
1305	}
1306
1307	if (likely(!ptrace) && unlikely(p->ptrace)) {
1308		/*
1309		 * If it is traced by its real parent's group, just pretend
1310		 * the caller is ptrace_do_wait() and reap this child if it
1311		 * is zombie.
1312		 *
1313		 * This also hides group stop state from real parent; otherwise
1314		 * a single stop can be reported twice as group and ptrace stop.
1315		 * If a ptracer wants to distinguish these two events for its
1316		 * own children it should create a separate process which takes
1317		 * the role of real parent.
1318		 */
1319		if (!ptrace_reparented(p))
1320			ptrace = 1;
1321	}
1322
1323	/* slay zombie? */
1324	if (exit_state == EXIT_ZOMBIE) {
1325		/* we don't reap group leaders with subthreads */
1326		if (!delay_group_leader(p)) {
1327			/*
1328			 * A zombie ptracee is only visible to its ptracer.
1329			 * Notification and reaping will be cascaded to the
1330			 * real parent when the ptracer detaches.
1331			 */
1332			if (unlikely(ptrace) || likely(!p->ptrace))
1333				return wait_task_zombie(wo, p);
1334		}
1335
1336		/*
1337		 * Allow access to stopped/continued state via zombie by
1338		 * falling through.  Clearing of notask_error is complex.
1339		 *
1340		 * When !@ptrace:
1341		 *
1342		 * If WEXITED is set, notask_error should naturally be
1343		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1344		 * so, if there are live subthreads, there are events to
1345		 * wait for.  If all subthreads are dead, it's still safe
1346		 * to clear - this function will be called again in finite
1347		 * amount time once all the subthreads are released and
1348		 * will then return without clearing.
1349		 *
1350		 * When @ptrace:
1351		 *
1352		 * Stopped state is per-task and thus can't change once the
1353		 * target task dies.  Only continued and exited can happen.
1354		 * Clear notask_error if WCONTINUED | WEXITED.
1355		 */
1356		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1357			wo->notask_error = 0;
1358	} else {
1359		/*
1360		 * @p is alive and it's gonna stop, continue or exit, so
1361		 * there always is something to wait for.
1362		 */
1363		wo->notask_error = 0;
1364	}
1365
1366	/*
1367	 * Wait for stopped.  Depending on @ptrace, different stopped state
1368	 * is used and the two don't interact with each other.
1369	 */
1370	ret = wait_task_stopped(wo, ptrace, p);
1371	if (ret)
1372		return ret;
1373
1374	/*
1375	 * Wait for continued.  There's only one continued state and the
1376	 * ptracer can consume it which can confuse the real parent.  Don't
1377	 * use WCONTINUED from ptracer.  You don't need or want it.
1378	 */
1379	return wait_task_continued(wo, p);
1380}
1381
1382/*
1383 * Do the work of do_wait() for one thread in the group, @tsk.
1384 *
1385 * -ECHILD should be in ->notask_error before the first call.
1386 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1387 * Returns zero if the search for a child should continue; then
1388 * ->notask_error is 0 if there were any eligible children,
1389 * or still -ECHILD.
1390 */
1391static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1392{
1393	struct task_struct *p;
1394
1395	list_for_each_entry(p, &tsk->children, sibling) {
1396		int ret = wait_consider_task(wo, 0, p);
1397
1398		if (ret)
1399			return ret;
1400	}
1401
1402	return 0;
1403}
1404
1405static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1406{
1407	struct task_struct *p;
1408
1409	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1410		int ret = wait_consider_task(wo, 1, p);
1411
1412		if (ret)
1413			return ret;
1414	}
1415
1416	return 0;
1417}
1418
1419static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
1420				int sync, void *key)
1421{
1422	struct wait_opts *wo = container_of(wait, struct wait_opts,
1423						child_wait);
1424	struct task_struct *p = key;
1425
1426	if (!eligible_pid(wo, p))
1427		return 0;
1428
1429	if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1430		return 0;
1431
1432	return default_wake_function(wait, mode, sync, key);
1433}
1434
1435void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1436{
1437	__wake_up_sync_key(&parent->signal->wait_chldexit,
1438				TASK_INTERRUPTIBLE, 1, p);
1439}
1440
1441static long do_wait(struct wait_opts *wo)
1442{
1443	struct task_struct *tsk;
1444	int retval;
1445
1446	trace_sched_process_wait(wo->wo_pid);
1447
1448	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1449	wo->child_wait.private = current;
1450	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1451repeat:
1452	/*
1453	 * If there is nothing that can match our criteria, just get out.
1454	 * We will clear ->notask_error to zero if we see any child that
1455	 * might later match our criteria, even if we are not able to reap
1456	 * it yet.
1457	 */
1458	wo->notask_error = -ECHILD;
1459	if ((wo->wo_type < PIDTYPE_MAX) &&
1460	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1461		goto notask;
1462
1463	set_current_state(TASK_INTERRUPTIBLE);
1464	read_lock(&tasklist_lock);
1465	tsk = current;
1466	do {
1467		retval = do_wait_thread(wo, tsk);
1468		if (retval)
1469			goto end;
1470
1471		retval = ptrace_do_wait(wo, tsk);
1472		if (retval)
1473			goto end;
1474
1475		if (wo->wo_flags & __WNOTHREAD)
1476			break;
1477	} while_each_thread(current, tsk);
1478	read_unlock(&tasklist_lock);
1479
1480notask:
1481	retval = wo->notask_error;
1482	if (!retval && !(wo->wo_flags & WNOHANG)) {
1483		retval = -ERESTARTSYS;
1484		if (!signal_pending(current)) {
1485			schedule();
1486			goto repeat;
1487		}
1488	}
1489end:
1490	__set_current_state(TASK_RUNNING);
1491	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1492	return retval;
1493}
1494
1495static struct pid *pidfd_get_pid(unsigned int fd)
1496{
1497	struct fd f;
1498	struct pid *pid;
1499
1500	f = fdget(fd);
1501	if (!f.file)
1502		return ERR_PTR(-EBADF);
1503
1504	pid = pidfd_pid(f.file);
1505	if (!IS_ERR(pid))
1506		get_pid(pid);
1507
1508	fdput(f);
1509	return pid;
1510}
1511
1512static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
1513			  int options, struct rusage *ru)
1514{
1515	struct wait_opts wo;
1516	struct pid *pid = NULL;
1517	enum pid_type type;
1518	long ret;
1519
1520	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1521			__WNOTHREAD|__WCLONE|__WALL))
1522		return -EINVAL;
1523	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1524		return -EINVAL;
1525
1526	switch (which) {
1527	case P_ALL:
1528		type = PIDTYPE_MAX;
1529		break;
1530	case P_PID:
1531		type = PIDTYPE_PID;
1532		if (upid <= 0)
1533			return -EINVAL;
1534
1535		pid = find_get_pid(upid);
1536		break;
1537	case P_PGID:
1538		type = PIDTYPE_PGID;
1539		if (upid < 0)
1540			return -EINVAL;
1541
1542		if (upid)
1543			pid = find_get_pid(upid);
1544		else
1545			pid = get_task_pid(current, PIDTYPE_PGID);
1546		break;
1547	case P_PIDFD:
1548		type = PIDTYPE_PID;
1549		if (upid < 0)
1550			return -EINVAL;
1551
1552		pid = pidfd_get_pid(upid);
1553		if (IS_ERR(pid))
1554			return PTR_ERR(pid);
1555		break;
1556	default:
1557		return -EINVAL;
1558	}
1559
 
 
 
1560	wo.wo_type	= type;
1561	wo.wo_pid	= pid;
1562	wo.wo_flags	= options;
1563	wo.wo_info	= infop;
1564	wo.wo_rusage	= ru;
1565	ret = do_wait(&wo);
1566
1567	put_pid(pid);
1568	return ret;
1569}
1570
1571SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1572		infop, int, options, struct rusage __user *, ru)
1573{
1574	struct rusage r;
1575	struct waitid_info info = {.status = 0};
1576	long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
1577	int signo = 0;
1578
1579	if (err > 0) {
1580		signo = SIGCHLD;
1581		err = 0;
1582		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1583			return -EFAULT;
1584	}
1585	if (!infop)
1586		return err;
1587
1588	if (!user_access_begin(infop, sizeof(*infop)))
1589		return -EFAULT;
1590
 
1591	unsafe_put_user(signo, &infop->si_signo, Efault);
1592	unsafe_put_user(0, &infop->si_errno, Efault);
1593	unsafe_put_user(info.cause, &infop->si_code, Efault);
1594	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1595	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1596	unsafe_put_user(info.status, &infop->si_status, Efault);
1597	user_access_end();
1598	return err;
1599Efault:
1600	user_access_end();
1601	return -EFAULT;
1602}
1603
1604long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
1605		  struct rusage *ru)
1606{
1607	struct wait_opts wo;
1608	struct pid *pid = NULL;
1609	enum pid_type type;
1610	long ret;
1611
1612	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1613			__WNOTHREAD|__WCLONE|__WALL))
1614		return -EINVAL;
1615
1616	/* -INT_MIN is not defined */
1617	if (upid == INT_MIN)
1618		return -ESRCH;
1619
1620	if (upid == -1)
1621		type = PIDTYPE_MAX;
1622	else if (upid < 0) {
1623		type = PIDTYPE_PGID;
1624		pid = find_get_pid(-upid);
1625	} else if (upid == 0) {
1626		type = PIDTYPE_PGID;
1627		pid = get_task_pid(current, PIDTYPE_PGID);
1628	} else /* upid > 0 */ {
1629		type = PIDTYPE_PID;
1630		pid = find_get_pid(upid);
1631	}
1632
1633	wo.wo_type	= type;
1634	wo.wo_pid	= pid;
1635	wo.wo_flags	= options | WEXITED;
1636	wo.wo_info	= NULL;
1637	wo.wo_stat	= 0;
1638	wo.wo_rusage	= ru;
1639	ret = do_wait(&wo);
1640	put_pid(pid);
1641	if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
1642		ret = -EFAULT;
1643
1644	return ret;
1645}
1646
1647SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1648		int, options, struct rusage __user *, ru)
1649{
1650	struct rusage r;
1651	long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
1652
1653	if (err > 0) {
1654		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1655			return -EFAULT;
1656	}
1657	return err;
1658}
1659
1660#ifdef __ARCH_WANT_SYS_WAITPID
1661
1662/*
1663 * sys_waitpid() remains for compatibility. waitpid() should be
1664 * implemented by calling sys_wait4() from libc.a.
1665 */
1666SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1667{
1668	return kernel_wait4(pid, stat_addr, options, NULL);
1669}
1670
1671#endif
1672
1673#ifdef CONFIG_COMPAT
1674COMPAT_SYSCALL_DEFINE4(wait4,
1675	compat_pid_t, pid,
1676	compat_uint_t __user *, stat_addr,
1677	int, options,
1678	struct compat_rusage __user *, ru)
1679{
1680	struct rusage r;
1681	long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
1682	if (err > 0) {
1683		if (ru && put_compat_rusage(&r, ru))
1684			return -EFAULT;
1685	}
1686	return err;
1687}
1688
1689COMPAT_SYSCALL_DEFINE5(waitid,
1690		int, which, compat_pid_t, pid,
1691		struct compat_siginfo __user *, infop, int, options,
1692		struct compat_rusage __user *, uru)
1693{
1694	struct rusage ru;
1695	struct waitid_info info = {.status = 0};
1696	long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
1697	int signo = 0;
1698	if (err > 0) {
1699		signo = SIGCHLD;
1700		err = 0;
1701		if (uru) {
1702			/* kernel_waitid() overwrites everything in ru */
1703			if (COMPAT_USE_64BIT_TIME)
1704				err = copy_to_user(uru, &ru, sizeof(ru));
1705			else
1706				err = put_compat_rusage(&ru, uru);
1707			if (err)
1708				return -EFAULT;
1709		}
1710	}
1711
1712	if (!infop)
1713		return err;
1714
1715	if (!user_access_begin(infop, sizeof(*infop)))
1716		return -EFAULT;
1717
 
1718	unsafe_put_user(signo, &infop->si_signo, Efault);
1719	unsafe_put_user(0, &infop->si_errno, Efault);
1720	unsafe_put_user(info.cause, &infop->si_code, Efault);
1721	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1722	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1723	unsafe_put_user(info.status, &infop->si_status, Efault);
1724	user_access_end();
1725	return err;
1726Efault:
1727	user_access_end();
1728	return -EFAULT;
1729}
1730#endif
1731
1732__weak void abort(void)
1733{
1734	BUG();
1735
1736	/* if that doesn't kill us, halt */
1737	panic("Oops failed to kill thread");
1738}
1739EXPORT_SYMBOL(abort);