text: /*
   *  linux/kernel/signal.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  1997-11-02  Modified for POSIX.1b signals by Richard Henderson
   *
   *  2003-06-02  Jim Houston - Concurrent Computer Corp.
   *		Changes to use preallocated sigqueue structures
   *		to allow signals to be sent reliably.
   */
  
  #include <linux/slab.h>
  #include <linux/export.h>
  #include <linux/init.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/user.h>
  #include <linux/sched/debug.h>
  #include <linux/sched/task.h>
  #include <linux/sched/task_stack.h>
  #include <linux/sched/cputime.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/proc_fs.h>
  #include <linux/tty.h>
  #include <linux/binfmts.h>
  #include <linux/coredump.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/ptrace.h>
  #include <linux/signal.h>
  #include <linux/signalfd.h>
  #include <linux/ratelimit.h>
  #include <linux/tracehook.h>
  #include <linux/capability.h>
  #include <linux/freezer.h>
  #include <linux/pid_namespace.h>
  #include <linux/nsproxy.h>
  #include <linux/user_namespace.h>
  #include <linux/uprobes.h>
  #include <linux/compat.h>
  #include <linux/cn_proc.h>
  #include <linux/compiler.h>
  #include <linux/posix-timers.h>
  #include <linux/livepatch.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/signal.h>
  
  #include <asm/param.h>
  #include <linux/uaccess.h>
  #include <asm/unistd.h>
  #include <asm/siginfo.h>
  #include <asm/cacheflush.h>
  #include "audit.h"	/* audit_signal_info() */
  
  /*
   * SLAB caches for signal bits.
   */
  
  static struct kmem_cache *sigqueue_cachep;
  
  int print_fatal_signals __read_mostly;
  
  static void __user *sig_handler(struct task_struct *t, int sig)
  {
  	return t->sighand->action[sig - 1].sa.sa_handler;
  }
  
  static inline bool sig_handler_ignored(void __user *handler, int sig)
  {
  	/* Is it explicitly or implicitly ignored? */
  	return handler == SIG_IGN ||
  	       (handler == SIG_DFL && sig_kernel_ignore(sig));
  }
  
  static bool sig_task_ignored(struct task_struct *t, int sig, bool force)
  {
  	void __user *handler;
  
  	handler = sig_handler(t, sig);
  
  	/* SIGKILL and SIGSTOP may not be sent to the global init */
  	if (unlikely(is_global_init(t) && sig_kernel_only(sig)))
  		return true;
  
  	if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
  	    handler == SIG_DFL && !(force && sig_kernel_only(sig)))
  		return true;
  
  	return sig_handler_ignored(handler, sig);
  }
  
  static bool sig_ignored(struct task_struct *t, int sig, bool force)
  {
  	/*
  	 * Blocked signals are never ignored, since the
  	 * signal handler may change by the time it is
  	 * unblocked.
  	 */
  	if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
  		return false;
  
  	/*
  	 * Tracers may want to know about even ignored signal unless it
  	 * is SIGKILL which can't be reported anyway but can be ignored
  	 * by SIGNAL_UNKILLABLE task.
  	 */
  	if (t->ptrace && sig != SIGKILL)
  		return false;
  
  	return sig_task_ignored(t, sig, force);
  }
  
  /*
   * Re-calculate pending state from the set of locally pending
   * signals, globally pending signals, and blocked signals.
   */
  static inline bool has_pending_signals(sigset_t *signal, sigset_t *blocked)
  {
  	unsigned long ready;
  	long i;
  
  	switch (_NSIG_WORDS) {
  	default:
  		for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
  			ready |= signal->sig[i] &~ blocked->sig[i];
  		break;
  
  	case 4: ready  = signal->sig[3] &~ blocked->sig[3];
  		ready |= signal->sig[2] &~ blocked->sig[2];
  		ready |= signal->sig[1] &~ blocked->sig[1];
  		ready |= signal->sig[0] &~ blocked->sig[0];
  		break;
  
  	case 2: ready  = signal->sig[1] &~ blocked->sig[1];
  		ready |= signal->sig[0] &~ blocked->sig[0];
  		break;
  
  	case 1: ready  = signal->sig[0] &~ blocked->sig[0];
  	}
  	return ready !=	0;
  }
  
  #define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
  
  static bool recalc_sigpending_tsk(struct task_struct *t)
  {
  	if ((t->jobctl & JOBCTL_PENDING_MASK) ||
  	    PENDING(&t->pending, &t->blocked) ||
  	    PENDING(&t->signal->shared_pending, &t->blocked)) {
  		set_tsk_thread_flag(t, TIF_SIGPENDING);
  		return true;
  	}
  
  	/*
  	 * We must never clear the flag in another thread, or in current
  	 * when it's possible the current syscall is returning -ERESTART*.
  	 * So we don't clear it here, and only callers who know they should do.
  	 */
  	return false;
  }
  
  /*
   * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
   * This is superfluous when called on current, the wakeup is a harmless no-op.
   */
  void recalc_sigpending_and_wake(struct task_struct *t)
  {
  	if (recalc_sigpending_tsk(t))
  		signal_wake_up(t, 0);
  }
  
  void recalc_sigpending(void)
  {
  	if (!recalc_sigpending_tsk(current) && !freezing(current) &&
  	    !klp_patch_pending(current))
  		clear_thread_flag(TIF_SIGPENDING);
  
  }
  EXPORT_SYMBOL(recalc_sigpending);
  
  void calculate_sigpending(void)
  {
  	/* Have any signals or users of TIF_SIGPENDING been delayed
  	 * until after fork?
  	 */
  	spin_lock_irq(&current->sighand->siglock);
  	set_tsk_thread_flag(current, TIF_SIGPENDING);
  	recalc_sigpending();
  	spin_unlock_irq(&current->sighand->siglock);
  }
  
  /* Given the mask, find the first available signal that should be serviced. */
  
  #define SYNCHRONOUS_MASK \
  	(sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
  	 sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))
  
  int next_signal(struct sigpending *pending, sigset_t *mask)
  {
  	unsigned long i, *s, *m, x;
  	int sig = 0;
  
  	s = pending->signal.sig;
  	m = mask->sig;
  
  	/*
  	 * Handle the first word specially: it contains the
  	 * synchronous signals that need to be dequeued first.
  	 */
  	x = *s &~ *m;
  	if (x) {
  		if (x & SYNCHRONOUS_MASK)
  			x &= SYNCHRONOUS_MASK;
  		sig = ffz(~x) + 1;
  		return sig;
  	}
  
  	switch (_NSIG_WORDS) {
  	default:
  		for (i = 1; i < _NSIG_WORDS; ++i) {
  			x = *++s &~ *++m;
  			if (!x)
  				continue;
  			sig = ffz(~x) + i*_NSIG_BPW + 1;
  			break;
  		}
  		break;
  
  	case 2:
  		x = s[1] &~ m[1];
  		if (!x)
  			break;
  		sig = ffz(~x) + _NSIG_BPW + 1;
  		break;
  
  	case 1:
  		/* Nothing to do */
  		break;
  	}
  
  	return sig;
  }
  
  static inline void print_dropped_signal(int sig)
  {
  	static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
  
  	if (!print_fatal_signals)
  		return;
  
  	if (!__ratelimit(&ratelimit_state))
  		return;
  
  	pr_info("%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
  				current->comm, current->pid, sig);
  }
  
  /**
   * task_set_jobctl_pending - set jobctl pending bits
   * @task: target task
   * @mask: pending bits to set
   *
   * Clear @mask from @task->jobctl.  @mask must be subset of
   * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK |
   * %JOBCTL_TRAPPING.  If stop signo is being set, the existing signo is
   * cleared.  If @task is already being killed or exiting, this function
   * becomes noop.
   *
   * CONTEXT:
   * Must be called with @task->sighand->siglock held.
   *
   * RETURNS:
   * %true if @mask is set, %false if made noop because @task was dying.
   */
  bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
  {
  	BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
  			JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
  	BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK));
  
  	if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING)))
  		return false;
  
  	if (mask & JOBCTL_STOP_SIGMASK)
  		task->jobctl &= ~JOBCTL_STOP_SIGMASK;
  
  	task->jobctl |= mask;
  	return true;
  }
  
  /**
   * task_clear_jobctl_trapping - clear jobctl trapping bit
   * @task: target task
   *
   * If JOBCTL_TRAPPING is set, a ptracer is waiting for us to enter TRACED.
   * Clear it and wake up the ptracer.  Note that we don't need any further
   * locking.  @task->siglock guarantees that @task->parent points to the
   * ptracer.
   *
   * CONTEXT:
   * Must be called with @task->sighand->siglock held.
   */
  void task_clear_jobctl_trapping(struct task_struct *task)
  {
  	if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
  		task->jobctl &= ~JOBCTL_TRAPPING;
  		smp_mb();	/* advised by wake_up_bit() */
  		wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
  	}
  }
  
  /**
   * task_clear_jobctl_pending - clear jobctl pending bits
   * @task: target task
   * @mask: pending bits to clear
   *
   * Clear @mask from @task->jobctl.  @mask must be subset of
   * %JOBCTL_PENDING_MASK.  If %JOBCTL_STOP_PENDING is being cleared, other
   * STOP bits are cleared together.
   *
   * If clearing of @mask leaves no stop or trap pending, this function calls
   * task_clear_jobctl_trapping().
   *
   * CONTEXT:
   * Must be called with @task->sighand->siglock held.
   */
  void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
  {
  	BUG_ON(mask & ~JOBCTL_PENDING_MASK);
  
  	if (mask & JOBCTL_STOP_PENDING)
  		mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED;
  
  	task->jobctl &= ~mask;
  
  	if (!(task->jobctl & JOBCTL_PENDING_MASK))
  		task_clear_jobctl_trapping(task);
  }
  
  /**
   * task_participate_group_stop - participate in a group stop
   * @task: task participating in a group stop
   *
   * @task has %JOBCTL_STOP_PENDING set and is participating in a group stop.
   * Group stop states are cleared and the group stop count is consumed if
   * %JOBCTL_STOP_CONSUME was set.  If the consumption completes the group
   * stop, the appropriate %SIGNAL_* flags are set.
   *
   * CONTEXT:
   * Must be called with @task->sighand->siglock held.
   *
   * RETURNS:
   * %true if group stop completion should be notified to the parent, %false
   * otherwise.
   */
  static bool task_participate_group_stop(struct task_struct *task)
  {
  	struct signal_struct *sig = task->signal;
  	bool consume = task->jobctl & JOBCTL_STOP_CONSUME;
  
  	WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING));
  
  	task_clear_jobctl_pending(task, JOBCTL_STOP_PENDING);
  
  	if (!consume)
  		return false;
  
  	if (!WARN_ON_ONCE(sig->group_stop_count == 0))
  		sig->group_stop_count--;
  
  	/*
  	 * Tell the caller to notify completion iff we are entering into a
  	 * fresh group stop.  Read comment in do_signal_stop() for details.
  	 */
  	if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
  		signal_set_stop_flags(sig, SIGNAL_STOP_STOPPED);
  		return true;
  	}
  	return false;
  }
  
  void task_join_group_stop(struct task_struct *task)
  {
  	/* Have the new thread join an on-going signal group stop */
  	unsigned long jobctl = current->jobctl;
  	if (jobctl & JOBCTL_STOP_PENDING) {
  		struct signal_struct *sig = current->signal;
  		unsigned long signr = jobctl & JOBCTL_STOP_SIGMASK;
  		unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
  		if (task_set_jobctl_pending(task, signr | gstop)) {
  			sig->group_stop_count++;
  		}
  	}
  }
  
  /*
   * allocate a new signal queue record
   * - this may be called without locks if and only if t == current, otherwise an
   *   appropriate lock must be held to stop the target task from exiting
   */
  static struct sigqueue *
  __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
  {
  	struct sigqueue *q = NULL;
  	struct user_struct *user;
  
  	/*
  	 * Protect access to @t credentials. This can go away when all
  	 * callers hold rcu read lock.
  	 */
  	rcu_read_lock();
  	user = get_uid(__task_cred(t)->user);
  	atomic_inc(&user->sigpending);
  	rcu_read_unlock();
  
  	if (override_rlimit ||
  	    atomic_read(&user->sigpending) <=
  			task_rlimit(t, RLIMIT_SIGPENDING)) {
  		q = kmem_cache_alloc(sigqueue_cachep, flags);
  	} else {
  		print_dropped_signal(sig);
  	}
  
  	if (unlikely(q == NULL)) {
  		atomic_dec(&user->sigpending);
  		free_uid(user);
  	} else {
  		INIT_LIST_HEAD(&q->list);
  		q->flags = 0;
  		q->user = user;
  	}
  
  	return q;
  }
  
  static void __sigqueue_free(struct sigqueue *q)
  {
  	if (q->flags & SIGQUEUE_PREALLOC)
  		return;
  	atomic_dec(&q->user->sigpending);
  	free_uid(q->user);
  	kmem_cache_free(sigqueue_cachep, q);
  }
  
  void flush_sigqueue(struct sigpending *queue)
  {
  	struct sigqueue *q;
  
  	sigemptyset(&queue->signal);
  	while (!list_empty(&queue->list)) {
  		q = list_entry(queue->list.next, struct sigqueue , list);
  		list_del_init(&q->list);
  		__sigqueue_free(q);
  	}
  }
  
  /*
   * Flush all pending signals for this kthread.
   */
  void flush_signals(struct task_struct *t)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&t->sighand->siglock, flags);
  	clear_tsk_thread_flag(t, TIF_SIGPENDING);
  	flush_sigqueue(&t->pending);
  	flush_sigqueue(&t->signal->shared_pending);
  	spin_unlock_irqrestore(&t->sighand->siglock, flags);
  }
  EXPORT_SYMBOL(flush_signals);
  
  #ifdef CONFIG_POSIX_TIMERS
  static void __flush_itimer_signals(struct sigpending *pending)
  {
  	sigset_t signal, retain;
  	struct sigqueue *q, *n;
  
  	signal = pending->signal;
  	sigemptyset(&retain);
  
  	list_for_each_entry_safe(q, n, &pending->list, list) {
  		int sig = q->info.si_signo;
  
  		if (likely(q->info.si_code != SI_TIMER)) {
  			sigaddset(&retain, sig);
  		} else {
  			sigdelset(&signal, sig);
  			list_del_init(&q->list);
  			__sigqueue_free(q);
  		}
  	}
  
  	sigorsets(&pending->signal, &signal, &retain);
  }
  
  void flush_itimer_signals(void)
  {
  	struct task_struct *tsk = current;
  	unsigned long flags;
  
  	spin_lock_irqsave(&tsk->sighand->siglock, flags);
  	__flush_itimer_signals(&tsk->pending);
  	__flush_itimer_signals(&tsk->signal->shared_pending);
  	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
  }
  #endif
  
  void ignore_signals(struct task_struct *t)
  {
  	int i;
  
  	for (i = 0; i < _NSIG; ++i)
  		t->sighand->action[i].sa.sa_handler = SIG_IGN;
  
  	flush_signals(t);
  }
  
  /*
   * Flush all handlers for a task.
   */
  
  void
  flush_signal_handlers(struct task_struct *t, int force_default)
  {
  	int i;
  	struct k_sigaction *ka = &t->sighand->action[0];
  	for (i = _NSIG ; i != 0 ; i--) {
  		if (force_default || ka->sa.sa_handler != SIG_IGN)
  			ka->sa.sa_handler = SIG_DFL;
  		ka->sa.sa_flags = 0;
  #ifdef __ARCH_HAS_SA_RESTORER
  		ka->sa.sa_restorer = NULL;
  #endif
  		sigemptyset(&ka->sa.sa_mask);
  		ka++;
  	}
  }
  
  bool unhandled_signal(struct task_struct *tsk, int sig)
  {
  	void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
  	if (is_global_init(tsk))
  		return true;
  
  	if (handler != SIG_IGN && handler != SIG_DFL)
  		return false;
  
  	/* if ptraced, let the tracer determine */
  	return !tsk->ptrace;
  }
  
  static void collect_signal(int sig, struct sigpending *list, kernel_siginfo_t *info,
  			   bool *resched_timer)
  {
  	struct sigqueue *q, *first = NULL;
  
  	/*
  	 * Collect the siginfo appropriate to this signal.  Check if
  	 * there is another siginfo for the same signal.
  	*/
  	list_for_each_entry(q, &list->list, list) {
  		if (q->info.si_signo == sig) {
  			if (first)
  				goto still_pending;
  			first = q;
  		}
  	}
  
  	sigdelset(&list->signal, sig);
  
  	if (first) {
  still_pending:
  		list_del_init(&first->list);
  		copy_siginfo(info, &first->info);
  
  		*resched_timer =
  			(first->flags & SIGQUEUE_PREALLOC) &&
  			(info->si_code == SI_TIMER) &&
  			(info->si_sys_private);
  
  		__sigqueue_free(first);
  	} else {
  		/*
  		 * Ok, it wasn't in the queue.  This must be
  		 * a fast-pathed signal or we must have been
  		 * out of queue space.  So zero out the info.
  		 */
  		clear_siginfo(info);
  		info->si_signo = sig;
  		info->si_errno = 0;
  		info->si_code = SI_USER;
  		info->si_pid = 0;
  		info->si_uid = 0;
  	}
  }
  
  static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
  			kernel_siginfo_t *info, bool *resched_timer)
  {
  	int sig = next_signal(pending, mask);
  
  	if (sig)
  		collect_signal(sig, pending, info, resched_timer);
  	return sig;
  }
  
  /*
   * Dequeue a signal and return the element to the caller, which is
   * expected to free it.
   *
   * All callers have to hold the siglock.
   */
  int dequeue_signal(struct task_struct *tsk, sigset_t *mask, kernel_siginfo_t *info)
  {
  	bool resched_timer = false;
  	int signr;
  
  	/* We only dequeue private signals from ourselves, we don't let
  	 * signalfd steal them
  	 */
  	signr = __dequeue_signal(&tsk->pending, mask, info, &resched_timer);
  	if (!signr) {
  		signr = __dequeue_signal(&tsk->signal->shared_pending,
  					 mask, info, &resched_timer);
  #ifdef CONFIG_POSIX_TIMERS
  		/*
  		 * itimer signal ?
  		 *
  		 * itimers are process shared and we restart periodic
  		 * itimers in the signal delivery path to prevent DoS
  		 * attacks in the high resolution timer case. This is
  		 * compliant with the old way of self-restarting
  		 * itimers, as the SIGALRM is a legacy signal and only
  		 * queued once. Changing the restart behaviour to
  		 * restart the timer in the signal dequeue path is
  		 * reducing the timer noise on heavy loaded !highres
  		 * systems too.
  		 */
  		if (unlikely(signr == SIGALRM)) {
  			struct hrtimer *tmr = &tsk->signal->real_timer;
  
  			if (!hrtimer_is_queued(tmr) &&
  			    tsk->signal->it_real_incr != 0) {
  				hrtimer_forward(tmr, tmr->base->get_time(),
  						tsk->signal->it_real_incr);
  				hrtimer_restart(tmr);
  			}
  		}
  #endif
  	}
  
  	recalc_sigpending();
  	if (!signr)
  		return 0;
  
  	if (unlikely(sig_kernel_stop(signr))) {
  		/*
  		 * Set a marker that we have dequeued a stop signal.  Our
  		 * caller might release the siglock and then the pending
  		 * stop signal it is about to process is no longer in the
  		 * pending bitmasks, but must still be cleared by a SIGCONT
  		 * (and overruled by a SIGKILL).  So those cases clear this
  		 * shared flag after we've set it.  Note that this flag may
  		 * remain set after the signal we return is ignored or
  		 * handled.  That doesn't matter because its only purpose
  		 * is to alert stop-signal processing code when another
  		 * processor has come along and cleared the flag.
  		 */
  		current->jobctl |= JOBCTL_STOP_DEQUEUED;
  	}
  #ifdef CONFIG_POSIX_TIMERS
  	if (resched_timer) {
  		/*
  		 * Release the siglock to ensure proper locking order
  		 * of timer locks outside of siglocks.  Note, we leave
  		 * irqs disabled here, since the posix-timers code is
  		 * about to disable them again anyway.
  		 */
  		spin_unlock(&tsk->sighand->siglock);
  		posixtimer_rearm(info);
  		spin_lock(&tsk->sighand->siglock);
  
  		/* Don't expose the si_sys_private value to userspace */
  		info->si_sys_private = 0;
  	}
  #endif
  	return signr;
  }
  EXPORT_SYMBOL_GPL(dequeue_signal);
  
  static int dequeue_synchronous_signal(kernel_siginfo_t *info)
  {
  	struct task_struct *tsk = current;
  	struct sigpending *pending = &tsk->pending;
  	struct sigqueue *q, *sync = NULL;
  
  	/*
  	 * Might a synchronous signal be in the queue?
  	 */
  	if (!((pending->signal.sig[0] & ~tsk->blocked.sig[0]) & SYNCHRONOUS_MASK))
  		return 0;
  
  	/*
  	 * Return the first synchronous signal in the queue.
  	 */
  	list_for_each_entry(q, &pending->list, list) {
  		/* Synchronous signals have a postive si_code */
  		if ((q->info.si_code > SI_USER) &&
  		    (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK)) {
  			sync = q;
  			goto next;
  		}
  	}
  	return 0;
  next:
  	/*
  	 * Check if there is another siginfo for the same signal.
  	 */
  	list_for_each_entry_continue(q, &pending->list, list) {
  		if (q->info.si_signo == sync->info.si_signo)
  			goto still_pending;
  	}
  
  	sigdelset(&pending->signal, sync->info.si_signo);
  	recalc_sigpending();
  still_pending:
  	list_del_init(&sync->list);
  	copy_siginfo(info, &sync->info);
  	__sigqueue_free(sync);
  	return info->si_signo;
  }
  
  /*
   * Tell a process that it has a new active signal..
   *
   * NOTE! we rely on the previous spin_lock to
   * lock interrupts for us! We can only be called with
   * "siglock" held, and the local interrupt must
   * have been disabled when that got acquired!
   *
   * No need to set need_resched since signal event passing
   * goes through ->blocked
   */
  void signal_wake_up_state(struct task_struct *t, unsigned int state)
  {
  	set_tsk_thread_flag(t, TIF_SIGPENDING);
  	/*
  	 * TASK_WAKEKILL also means wake it up in the stopped/traced/killable
  	 * case. We don't check t->state here because there is a race with it
  	 * executing another processor and just now entering stopped state.
  	 * By using wake_up_state, we ensure the process will wake up and
  	 * handle its death signal.
  	 */
  	if (!wake_up_state(t, state | TASK_INTERRUPTIBLE))
  		kick_process(t);
  }
  
  /*
   * Remove signals in mask from the pending set and queue.
   * Returns 1 if any signals were found.
   *
   * All callers must be holding the siglock.
   */
  static void flush_sigqueue_mask(sigset_t *mask, struct sigpending *s)
  {
  	struct sigqueue *q, *n;
  	sigset_t m;
  
  	sigandsets(&m, mask, &s->signal);
  	if (sigisemptyset(&m))
  		return;
  
  	sigandnsets(&s->signal, &s->signal, mask);
  	list_for_each_entry_safe(q, n, &s->list, list) {
  		if (sigismember(mask, q->info.si_signo)) {
  			list_del_init(&q->list);
  			__sigqueue_free(q);
  		}
  	}
  }
  
  static inline int is_si_special(const struct kernel_siginfo *info)
  {
  	return info <= SEND_SIG_PRIV;
  }
  
  static inline bool si_fromuser(const struct kernel_siginfo *info)
  {
  	return info == SEND_SIG_NOINFO ||
  		(!is_si_special(info) && SI_FROMUSER(info));
  }
  
  /*
   * called with RCU read lock from check_kill_permission()
   */
  static bool kill_ok_by_cred(struct task_struct *t)
  {
  	const struct cred *cred = current_cred();
  	const struct cred *tcred = __task_cred(t);
  
  	return uid_eq(cred->euid, tcred->suid) ||
  	       uid_eq(cred->euid, tcred->uid) ||
  	       uid_eq(cred->uid, tcred->suid) ||
  	       uid_eq(cred->uid, tcred->uid) ||
  	       ns_capable(tcred->user_ns, CAP_KILL);
  }
  
  /*
   * Bad permissions for sending the signal
   * - the caller must hold the RCU read lock
   */
  static int check_kill_permission(int sig, struct kernel_siginfo *info,
  				 struct task_struct *t)
  {
  	struct pid *sid;
  	int error;
  
  	if (!valid_signal(sig))
  		return -EINVAL;
  
  	if (!si_fromuser(info))
  		return 0;
  
  	error = audit_signal_info(sig, t); /* Let audit system see the signal */
  	if (error)
  		return error;
  
  	if (!same_thread_group(current, t) &&
  	    !kill_ok_by_cred(t)) {
  		switch (sig) {
  		case SIGCONT:
  			sid = task_session(t);
  			/*
  			 * We don't return the error if sid == NULL. The
  			 * task was unhashed, the caller must notice this.
  			 */
  			if (!sid || sid == task_session(current))
  				break;
  		default:
  			return -EPERM;
  		}
  	}
  
  	return security_task_kill(t, info, sig, NULL);
  }
  
  /**
   * ptrace_trap_notify - schedule trap to notify ptracer
   * @t: tracee wanting to notify tracer
   *
   * This function schedules sticky ptrace trap which is cleared on the next
   * TRAP_STOP to notify ptracer of an event.  @t must have been seized by
   * ptracer.
   *
   * If @t is running, STOP trap will be taken.  If trapped for STOP and
   * ptracer is listening for events, tracee is woken up so that it can
   * re-trap for the new event.  If trapped otherwise, STOP trap will be
   * eventually taken without returning to userland after the existing traps
   * are finished by PTRACE_CONT.
   *
   * CONTEXT:
   * Must be called with @task->sighand->siglock held.
   */
  static void ptrace_trap_notify(struct task_struct *t)
  {
  	WARN_ON_ONCE(!(t->ptrace & PT_SEIZED));
  	assert_spin_locked(&t->sighand->siglock);
  
  	task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY);
  	ptrace_signal_wake_up(t, t->jobctl & JOBCTL_LISTENING);
  }
  
  /*
   * Handle magic process-wide effects of stop/continue signals. Unlike
   * the signal actions, these happen immediately at signal-generation
   * time regardless of blocking, ignoring, or handling.  This does the
   * actual continuing for SIGCONT, but not the actual stopping for stop
   * signals. The process stop is done as a signal action for SIG_DFL.
   *
   * Returns true if the signal should be actually delivered, otherwise
   * it should be dropped.
   */
  static bool prepare_signal(int sig, struct task_struct *p, bool force)
  {
  	struct signal_struct *signal = p->signal;
  	struct task_struct *t;
  	sigset_t flush;
  
  	if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
  		if (!(signal->flags & SIGNAL_GROUP_EXIT))
  			return sig == SIGKILL;
  		/*
  		 * The process is in the middle of dying, nothing to do.
  		 */
  	} else if (sig_kernel_stop(sig)) {
  		/*
  		 * This is a stop signal.  Remove SIGCONT from all queues.
  		 */
  		siginitset(&flush, sigmask(SIGCONT));
  		flush_sigqueue_mask(&flush, &signal->shared_pending);
  		for_each_thread(p, t)
  			flush_sigqueue_mask(&flush, &t->pending);
  	} else if (sig == SIGCONT) {
  		unsigned int why;
  		/*
  		 * Remove all stop signals from all queues, wake all threads.
  		 */
  		siginitset(&flush, SIG_KERNEL_STOP_MASK);
  		flush_sigqueue_mask(&flush, &signal->shared_pending);
  		for_each_thread(p, t) {
  			flush_sigqueue_mask(&flush, &t->pending);
  			task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
  			if (likely(!(t->ptrace & PT_SEIZED)))
  				wake_up_state(t, __TASK_STOPPED);
  			else
  				ptrace_trap_notify(t);
  		}
  
  		/*
  		 * Notify the parent with CLD_CONTINUED if we were stopped.
  		 *
  		 * If we were in the middle of a group stop, we pretend it
  		 * was already finished, and then continued. Since SIGCHLD
  		 * doesn't queue we report only CLD_STOPPED, as if the next
  		 * CLD_CONTINUED was dropped.
  		 */
  		why = 0;
  		if (signal->flags & SIGNAL_STOP_STOPPED)
  			why |= SIGNAL_CLD_CONTINUED;
  		else if (signal->group_stop_count)
  			why |= SIGNAL_CLD_STOPPED;
  
  		if (why) {
  			/*
  			 * The first thread which returns from do_signal_stop()
  			 * will take ->siglock, notice SIGNAL_CLD_MASK, and
  			 * notify its parent. See get_signal().
  			 */
  			signal_set_stop_flags(signal, why | SIGNAL_STOP_CONTINUED);
  			signal->group_stop_count = 0;
  			signal->group_exit_code = 0;
  		}
  	}
  
  	return !sig_ignored(p, sig, force);
  }
  
  /*
   * Test if P wants to take SIG.  After we've checked all threads with this,
   * it's equivalent to finding no threads not blocking SIG.  Any threads not
   * blocking SIG were ruled out because they are not running and already
   * have pending signals.  Such threads will dequeue from the shared queue
   * as soon as they're available, so putting the signal on the shared queue
   * will be equivalent to sending it to one such thread.
   */
  static inline bool wants_signal(int sig, struct task_struct *p)
  {
  	if (sigismember(&p->blocked, sig))
  		return false;
  
  	if (p->flags & PF_EXITING)
  		return false;
  
  	if (sig == SIGKILL)
  		return true;
  
  	if (task_is_stopped_or_traced(p))
  		return false;
  
  	return task_curr(p) || !signal_pending(p);
  }
  
  static void complete_signal(int sig, struct task_struct *p, enum pid_type type)
  {
  	struct signal_struct *signal = p->signal;
  	struct task_struct *t;
  
  	/*
  	 * Now find a thread we can wake up to take the signal off the queue.
  	 *
  	 * If the main thread wants the signal, it gets first crack.
  	 * Probably the least surprising to the average bear.
  	 */
  	if (wants_signal(sig, p))
  		t = p;
  	else if ((type == PIDTYPE_PID) || thread_group_empty(p))
  		/*
  		 * There is just one thread and it does not need to be woken.
  		 * It will dequeue unblocked signals before it runs again.
  		 */
  		return;
  	else {
  		/*
  		 * Otherwise try to find a suitable thread.
  		 */
  		t = signal->curr_target;
  		while (!wants_signal(sig, t)) {
  			t = next_thread(t);
  			if (t == signal->curr_target)
  				/*
  				 * No thread needs to be woken.
  				 * Any eligible threads will see
  				 * the signal in the queue soon.
  				 */
  				return;
  		}
  		signal->curr_target = t;
  	}
  
  	/*
  	 * Found a killable thread.  If the signal will be fatal,
  	 * then start taking the whole group down immediately.
  	 */
  	if (sig_fatal(p, sig) &&
  	    !(signal->flags & SIGNAL_GROUP_EXIT) &&
  	    !sigismember(&t->real_blocked, sig) &&
  	    (sig == SIGKILL || !p->ptrace)) {
  		/*
  		 * This signal will be fatal to the whole group.
  		 */
  		if (!sig_kernel_coredump(sig)) {
  			/*
  			 * Start a group exit and wake everybody up.
  			 * This way we don't have other threads
  			 * running and doing things after a slower
  			 * thread has the fatal signal pending.
  			 */
  			signal->flags = SIGNAL_GROUP_EXIT;
  			signal->group_exit_code = sig;
  			signal->group_stop_count = 0;
  			t = p;
  			do {
  				task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
  				sigaddset(&t->pending.signal, SIGKILL);
  				signal_wake_up(t, 1);
  			} while_each_thread(p, t);
  			return;
  		}
  	}
  
  	/*
  	 * The signal is already in the shared-pending queue.
  	 * Tell the chosen thread to wake up and dequeue it.
  	 */
  	signal_wake_up(t, sig == SIGKILL);
  	return;
  }
  
  static inline bool legacy_queue(struct sigpending *signals, int sig)
  {
  	return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
  }
  
  #ifdef CONFIG_USER_NS
  static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t)
  {
  	if (current_user_ns() == task_cred_xxx(t, user_ns))
  		return;
  
  	if (SI_FROMKERNEL(info))
  		return;
  
  	rcu_read_lock();
  	info->si_uid = from_kuid_munged(task_cred_xxx(t, user_ns),
  					make_kuid(current_user_ns(), info->si_uid));
  	rcu_read_unlock();
  }
  #else
  static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t)
  {
  	return;
  }
  #endif
  
  static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
  			enum pid_type type, int from_ancestor_ns)
  {
  	struct sigpending *pending;
  	struct sigqueue *q;
  	int override_rlimit;
  	int ret = 0, result;
  
  	assert_spin_locked(&t->sighand->siglock);
  
  	result = TRACE_SIGNAL_IGNORED;
  	if (!prepare_signal(sig, t,
  			from_ancestor_ns || (info == SEND_SIG_PRIV)))
  		goto ret;
  
  	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
  	/*
  	 * Short-circuit ignored signals and support queuing
  	 * exactly one non-rt signal, so that we can get more
  	 * detailed information about the cause of the signal.
  	 */
  	result = TRACE_SIGNAL_ALREADY_PENDING;
  	if (legacy_queue(pending, sig))
  		goto ret;
  
  	result = TRACE_SIGNAL_DELIVERED;
  	/*
  	 * Skip useless siginfo allocation for SIGKILL and kernel threads.
  	 */
  	if ((sig == SIGKILL) || (t->flags & PF_KTHREAD))
  		goto out_set;
  
  	/*
  	 * Real-time signals must be queued if sent by sigqueue, or
  	 * some other real-time mechanism.  It is implementation
  	 * defined whether kill() does so.  We attempt to do so, on
  	 * the principle of least surprise, but since kill is not
  	 * allowed to fail with EAGAIN when low on memory we just
  	 * make sure at least one signal gets delivered and don't
  	 * pass on the info struct.
  	 */
  	if (sig < SIGRTMIN)
  		override_rlimit = (is_si_special(info) || info->si_code >= 0);
  	else
  		override_rlimit = 0;
  
  	q = __sigqueue_alloc(sig, t, GFP_ATOMIC, override_rlimit);
  	if (q) {
  		list_add_tail(&q->list, &pending->list);
  		switch ((unsigned long) info) {
  		case (unsigned long) SEND_SIG_NOINFO:
  			clear_siginfo(&q->info);
  			q->info.si_signo = sig;
  			q->info.si_errno = 0;
  			q->info.si_code = SI_USER;
  			q->info.si_pid = task_tgid_nr_ns(current,
  							task_active_pid_ns(t));
  			q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
  			break;
  		case (unsigned long) SEND_SIG_PRIV:
  			clear_siginfo(&q->info);
  			q->info.si_signo = sig;
  			q->info.si_errno = 0;
  			q->info.si_code = SI_KERNEL;
  			q->info.si_pid = 0;
  			q->info.si_uid = 0;
  			break;
  		default:
  			copy_siginfo(&q->info, info);
  			if (from_ancestor_ns)
  				q->info.si_pid = 0;
  			break;
  		}
  
  		userns_fixup_signal_uid(&q->info, t);
  
  	} else if (!is_si_special(info)) {
  		if (sig >= SIGRTMIN && info->si_code != SI_USER) {
  			/*
  			 * Queue overflow, abort.  We may abort if the
  			 * signal was rt and sent by user using something
  			 * other than kill().
  			 */
  			result = TRACE_SIGNAL_OVERFLOW_FAIL;
  			ret = -EAGAIN;
  			goto ret;
  		} else {
  			/*
  			 * This is a silent loss of information.  We still
  			 * send the signal, but the *info bits are lost.
  			 */
  			result = TRACE_SIGNAL_LOSE_INFO;
  		}
  	}
  
  out_set:
  	signalfd_notify(t, sig);
  	sigaddset(&pending->signal, sig);
  
  	/* Let multiprocess signals appear after on-going forks */
  	if (type > PIDTYPE_TGID) {
  		struct multiprocess_signals *delayed;
  		hlist_for_each_entry(delayed, &t->signal->multiprocess, node) {
  			sigset_t *signal = &delayed->signal;
  			/* Can't queue both a stop and a continue signal */
  			if (sig == SIGCONT)
  				sigdelsetmask(signal, SIG_KERNEL_STOP_MASK);
  			else if (sig_kernel_stop(sig))
  				sigdelset(signal, SIGCONT);
  			sigaddset(signal, sig);
  		}
  	}
  
  	complete_signal(sig, t, type);
  ret:
  	trace_signal_generate(sig, info, t, type != PIDTYPE_PID, result);
  	return ret;
  }
  
  static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
  			enum pid_type type)
  {
  	int from_ancestor_ns = 0;
  
  #ifdef CONFIG_PID_NS
  	from_ancestor_ns = si_fromuser(info) &&
  			   !task_pid_nr_ns(current, task_active_pid_ns(t));
  #endif
  
  	return __send_signal(sig, info, t, type, from_ancestor_ns);
  }
  
  static void print_fatal_signal(int signr)
  {
  	struct pt_regs *regs = signal_pt_regs();
  	pr_info("potentially unexpected fatal signal %d.\n", signr);
  
  #if defined(__i386__) && !defined(__arch_um__)
  	pr_info("code at %08lx: ", regs->ip);
  	{
  		int i;
  		for (i = 0; i < 16; i++) {
  			unsigned char insn;
  
  			if (get_user(insn, (unsigned char *)(regs->ip + i)))
  				break;
  			pr_cont("%02x ", insn);
  		}
  	}
  	pr_cont("\n");
  #endif
  	preempt_disable();
  	show_regs(regs);
  	preempt_enable();
  }
  
  static int __init setup_print_fatal_signals(char *str)
  {
  	get_option (&str, &print_fatal_signals);
  
  	return 1;
  }
  
  __setup("print-fatal-signals=", setup_print_fatal_signals);
  
  int
  __group_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p)
  {
  	return send_signal(sig, info, p, PIDTYPE_TGID);
  }
  
  int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p,
  			enum pid_type type)
  {
  	unsigned long flags;
  	int ret = -ESRCH;
  
  	if (lock_task_sighand(p, &flags)) {
  		ret = send_signal(sig, info, p, type);
  		unlock_task_sighand(p, &flags);
  	}
  
  	return ret;
  }
  
  /*
   * Force a signal that the process can't ignore: if necessary
   * we unblock the signal and change any SIG_IGN to SIG_DFL.
   *
   * Note: If we unblock the signal, we always reset it to SIG_DFL,
   * since we do not want to have a signal handler that was blocked
   * be invoked when user space had explicitly blocked it.
   *
   * We don't want to have recursive SIGSEGV's etc, for example,
   * that is why we also clear SIGNAL_UNKILLABLE.
   */
  int
  force_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *t)
  {
  	unsigned long int flags;
  	int ret, blocked, ignored;
  	struct k_sigaction *action;
  
  	spin_lock_irqsave(&t->sighand->siglock, flags);
  	action = &t->sighand->action[sig-1];
  	ignored = action->sa.sa_handler == SIG_IGN;
  	blocked = sigismember(&t->blocked, sig);
  	if (blocked || ignored) {
  		action->sa.sa_handler = SIG_DFL;
  		if (blocked) {
  			sigdelset(&t->blocked, sig);
  			recalc_sigpending_and_wake(t);
  		}
  	}
  	/*
  	 * Don't clear SIGNAL_UNKILLABLE for traced tasks, users won't expect
  	 * debugging to leave init killable.
  	 */
  	if (action->sa.sa_handler == SIG_DFL && !t->ptrace)
  		t->signal->flags &= ~SIGNAL_UNKILLABLE;
  	ret = send_signal(sig, info, t, PIDTYPE_PID);
  	spin_unlock_irqrestore(&t->sighand->siglock, flags);
  
  	return ret;
  }
  
  /*
   * Nuke all other threads in the group.
   */
  int zap_other_threads(struct task_struct *p)
  {
  	struct task_struct *t = p;
  	int count = 0;
  
  	p->signal->group_stop_count = 0;
  
  	while_each_thread(p, t) {
  		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
  		count++;
  
  		/* Don't bother with already dead threads */
  		if (t->exit_state)
  			continue;
  		sigaddset(&t->pending.signal, SIGKILL);
  		signal_wake_up(t, 1);
  	}
  
  	return count;
  }
  
  struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
  					   unsigned long *flags)
  {
  	struct sighand_struct *sighand;
  
  	rcu_read_lock();
  	for (;;) {
  		sighand = rcu_dereference(tsk->sighand);
  		if (unlikely(sighand == NULL))
  			break;
  
  		/*
  		 * This sighand can be already freed and even reused, but
  		 * we rely on SLAB_TYPESAFE_BY_RCU and sighand_ctor() which
  		 * initializes ->siglock: this slab can't go away, it has
  		 * the same object type, ->siglock can't be reinitialized.
  		 *
  		 * We need to ensure that tsk->sighand is still the same
  		 * after we take the lock, we can race with de_thread() or
  		 * __exit_signal(). In the latter case the next iteration
  		 * must see ->sighand == NULL.
  		 */
  		spin_lock_irqsave(&sighand->siglock, *flags);
  		if (likely(sighand == tsk->sighand))
  			break;
  		spin_unlock_irqrestore(&sighand->siglock, *flags);
  	}
  	rcu_read_unlock();
  
  	return sighand;
  }
  
  /*
   * send signal info to all the members of a group
   */
  int group_send_sig_info(int sig, struct kernel_siginfo *info,
  			struct task_struct *p, enum pid_type type)
  {
  	int ret;
  
  	rcu_read_lock();
  	ret = check_kill_permission(sig, info, p);
  	rcu_read_unlock();
  
  	if (!ret && sig)
  		ret = do_send_sig_info(sig, info, p, type);
  
  	return ret;
  }
  
  /*
   * __kill_pgrp_info() sends a signal to a process group: this is what the tty
   * control characters do (^C, ^Z etc)
   * - the caller must hold at least a readlock on tasklist_lock
   */
  int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp)
  {
  	struct task_struct *p = NULL;
  	int retval, success;
  
  	success = 0;
  	retval = -ESRCH;
  	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
  		int err = group_send_sig_info(sig, info, p, PIDTYPE_PGID);
  		success |= !err;
  		retval = err;
  	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
  	return success ? 0 : retval;
  }
  
  int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)
  {
  	int error = -ESRCH;
  	struct task_struct *p;
  
  	for (;;) {
  		rcu_read_lock();
  		p = pid_task(pid, PIDTYPE_PID);
  		if (p)
  			error = group_send_sig_info(sig, info, p, PIDTYPE_TGID);
  		rcu_read_unlock();
  		if (likely(!p || error != -ESRCH))
  			return error;
  
  		/*
  		 * The task was unhashed in between, try again.  If it
  		 * is dead, pid_task() will return NULL, if we race with
  		 * de_thread() it will find the new leader.
  		 */
  	}
  }
  
  static int kill_proc_info(int sig, struct kernel_siginfo *info, pid_t pid)
  {
  	int error;
  	rcu_read_lock();
  	error = kill_pid_info(sig, info, find_vpid(pid));
  	rcu_read_unlock();
  	return error;
  }
  
  static inline bool kill_as_cred_perm(const struct cred *cred,
  				     struct task_struct *target)
  {
  	const struct cred *pcred = __task_cred(target);
  
  	return uid_eq(cred->euid, pcred->suid) ||
  	       uid_eq(cred->euid, pcred->uid) ||
  	       uid_eq(cred->uid, pcred->suid) ||
  	       uid_eq(cred->uid, pcred->uid);
  }
  
  /* like kill_pid_info(), but doesn't use uid/euid of "current" */
  int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
  			 const struct cred *cred)
  {
  	int ret = -EINVAL;
  	struct task_struct *p;
  	unsigned long flags;
  
  	if (!valid_signal(sig))
  		return ret;
  
  	rcu_read_lock();
  	p = pid_task(pid, PIDTYPE_PID);
  	if (!p) {
  		ret = -ESRCH;
  		goto out_unlock;
  	}
  	if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
  		ret = -EPERM;
  		goto out_unlock;
  	}
  	ret = security_task_kill(p, info, sig, cred);
  	if (ret)
  		goto out_unlock;
  
  	if (sig) {
  		if (lock_task_sighand(p, &flags)) {
  			ret = __send_signal(sig, info, p, PIDTYPE_TGID, 0);
  			unlock_task_sighand(p, &flags);
  		} else
  			ret = -ESRCH;
  	}
  out_unlock:
  	rcu_read_unlock();
  	return ret;
  }
  EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
  
  /*
   * kill_something_info() interprets pid in interesting ways just like kill(2).
   *
   * POSIX specifies that kill(-1,sig) is unspecified, but what we have
   * is probably wrong.  Should make it like BSD or SYSV.
   */
  
  static int kill_something_info(int sig, struct kernel_siginfo *info, pid_t pid)
  {
  	int ret;
  
  	if (pid > 0) {
  		rcu_read_lock();
  		ret = kill_pid_info(sig, info, find_vpid(pid));
  		rcu_read_unlock();
  		return ret;
  	}
  
  	/* -INT_MIN is undefined.  Exclude this case to avoid a UBSAN warning */
  	if (pid == INT_MIN)
  		return -ESRCH;
  
  	read_lock(&tasklist_lock);
  	if (pid != -1) {
  		ret = __kill_pgrp_info(sig, info,
  				pid ? find_vpid(-pid) : task_pgrp(current));
  	} else {
  		int retval = 0, count = 0;
  		struct task_struct * p;
  
  		for_each_process(p) {
  			if (task_pid_vnr(p) > 1 &&
  					!same_thread_group(p, current)) {
  				int err = group_send_sig_info(sig, info, p,
  							      PIDTYPE_MAX);
  				++count;
  				if (err != -EPERM)
  					retval = err;
  			}
  		}
  		ret = count ? retval : -ESRCH;
  	}
  	read_unlock(&tasklist_lock);
  
  	return ret;
  }
  
  /*
   * These are for backward compatibility with the rest of the kernel source.
   */
  
  int send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p)
  {
  	/*
  	 * Make sure legacy kernel users don't send in bad values
  	 * (normal paths check this in check_kill_permission).
  	 */
  	if (!valid_signal(sig))
  		return -EINVAL;
  
  	return do_send_sig_info(sig, info, p, PIDTYPE_PID);
  }
  EXPORT_SYMBOL(send_sig_info);
  
  #define __si_special(priv) \
  	((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)
  
  int
  send_sig(int sig, struct task_struct *p, int priv)
  {
  	return send_sig_info(sig, __si_special(priv), p);
  }
  EXPORT_SYMBOL(send_sig);
  
  void force_sig(int sig, struct task_struct *p)
  {
  	force_sig_info(sig, SEND_SIG_PRIV, p);
  }
  EXPORT_SYMBOL(force_sig);
  
  /*
   * When things go south during signal handling, we
   * will force a SIGSEGV. And if the signal that caused
   * the problem was already a SIGSEGV, we'll want to
   * make sure we don't even try to deliver the signal..
   */
  void force_sigsegv(int sig, struct task_struct *p)
  {
  	if (sig == SIGSEGV) {
  		unsigned long flags;
  		spin_lock_irqsave(&p->sighand->siglock, flags);
  		p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
  		spin_unlock_irqrestore(&p->sighand->siglock, flags);
  	}
  	force_sig(SIGSEGV, p);
  }
  
  int force_sig_fault(int sig, int code, void __user *addr
  	___ARCH_SI_TRAPNO(int trapno)
  	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
  	, struct task_struct *t)
  {
  	struct kernel_siginfo info;
  
  	clear_siginfo(&info);
  	info.si_signo = sig;
  	info.si_errno = 0;
  	info.si_code  = code;
  	info.si_addr  = addr;
  #ifdef __ARCH_SI_TRAPNO
  	info.si_trapno = trapno;
  #endif
  #ifdef __ia64__
  	info.si_imm = imm;
  	info.si_flags = flags;
  	info.si_isr = isr;
  #endif
  	return force_sig_info(info.si_signo, &info, t);
  }
  
  int send_sig_fault(int sig, int code, void __user *addr
  	___ARCH_SI_TRAPNO(int trapno)
  	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
  	, struct task_struct *t)
  {
  	struct kernel_siginfo info;
  
  	clear_siginfo(&info);
  	info.si_signo = sig;
  	info.si_errno = 0;
  	info.si_code  = code;
  	info.si_addr  = addr;
  #ifdef __ARCH_SI_TRAPNO
  	info.si_trapno = trapno;
  #endif
  #ifdef __ia64__
  	info.si_imm = imm;
  	info.si_flags = flags;
  	info.si_isr = isr;
  #endif
  	return send_sig_info(info.si_signo, &info, t);
  }
  
  int force_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
  {
  	struct kernel_siginfo info;
  
  	WARN_ON((code != BUS_MCEERR_AO) && (code != BUS_MCEERR_AR));
  	clear_siginfo(&info);
  	info.si_signo = SIGBUS;
  	info.si_errno = 0;
  	info.si_code = code;
  	info.si_addr = addr;
  	info.si_addr_lsb = lsb;
  	return force_sig_info(info.si_signo, &info, t);
  }
  
  int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
  {
  	struct kernel_siginfo info;
  
  	WARN_ON((code != BUS_MCEERR_AO) && (code != BUS_MCEERR_AR));
  	clear_siginfo(&info);
  	info.si_signo = SIGBUS;
  	info.si_errno = 0;
  	info.si_code = code;
  	info.si_addr = addr;
  	info.si_addr_lsb = lsb;
  	return send_sig_info(info.si_signo, &info, t);
  }
  EXPORT_SYMBOL(send_sig_mceerr);
  
  int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
  {
  	struct kernel_siginfo info;
  
  	clear_siginfo(&info);
  	info.si_signo = SIGSEGV;
  	info.si_errno = 0;
  	info.si_code  = SEGV_BNDERR;
  	info.si_addr  = addr;
  	info.si_lower = lower;
  	info.si_upper = upper;
  	return force_sig_info(info.si_signo, &info, current);
  }
  
  #ifdef SEGV_PKUERR
  int force_sig_pkuerr(void __user *addr, u32 pkey)
  {
  	struct kernel_siginfo info;
  
  	clear_siginfo(&info);
  	info.si_signo = SIGSEGV;
  	info.si_errno = 0;
  	info.si_code  = SEGV_PKUERR;
  	info.si_addr  = addr;
  	info.si_pkey  = pkey;
  	return force_sig_info(info.si_signo, &info, current);
  }
  #endif
  
  /* For the crazy architectures that include trap information in
   * the errno field, instead of an actual errno value.
   */
  int force_sig_ptrace_errno_trap(int errno, void __user *addr)
  {
  	struct kernel_siginfo info;
  
  	clear_siginfo(&info);
  	info.si_signo = SIGTRAP;
  	info.si_errno = errno;
  	info.si_code  = TRAP_HWBKPT;
  	info.si_addr  = addr;
  	return force_sig_info(info.si_signo, &info, current);
  }
  
  int kill_pgrp(struct pid *pid, int sig, int priv)
  {
  	int ret;
  
  	read_lock(&tasklist_lock);
  	ret = __kill_pgrp_info(sig, __si_special(priv), pid);
  	read_unlock(&tasklist_lock);
  
  	return ret;
  }
  EXPORT_SYMBOL(kill_pgrp);
  
  int kill_pid(struct pid *pid, int sig, int priv)
  {
  	return kill_pid_info(sig, __si_special(priv), pid);
  }
  EXPORT_SYMBOL(kill_pid);
  
  /*
   * These functions support sending signals using preallocated sigqueue
   * structures.  This is needed "because realtime applications cannot
   * afford to lose notifications of asynchronous events, like timer
   * expirations or I/O completions".  In the case of POSIX Timers
   * we allocate the sigqueue structure from the timer_create.  If this
   * allocation fails we are able to report the failure to the application
   * with an EAGAIN error.
   */
  struct sigqueue *sigqueue_alloc(void)
  {
  	struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
  
  	if (q)
  		q->flags |= SIGQUEUE_PREALLOC;
  
  	return q;
  }
  
  void sigqueue_free(struct sigqueue *q)
  {
  	unsigned long flags;
  	spinlock_t *lock = &current->sighand->siglock;
  
  	BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
  	/*
  	 * We must hold ->siglock while testing q->list
  	 * to serialize with collect_signal() or with
  	 * __exit_signal()->flush_sigqueue().
  	 */
  	spin_lock_irqsave(lock, flags);
  	q->flags &= ~SIGQUEUE_PREALLOC;
  	/*
  	 * If it is queued it will be freed when dequeued,
  	 * like the "regular" sigqueue.
  	 */
  	if (!list_empty(&q->list))
  		q = NULL;
  	spin_unlock_irqrestore(lock, flags);
  
  	if (q)
  		__sigqueue_free(q);
  }
  
  int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
  {
  	int sig = q->info.si_signo;
  	struct sigpending *pending;
  	struct task_struct *t;
  	unsigned long flags;
  	int ret, result;
  
  	BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
  
  	ret = -1;
  	rcu_read_lock();
  	t = pid_task(pid, type);
  	if (!t || !likely(lock_task_sighand(t, &flags)))
  		goto ret;
  
  	ret = 1; /* the signal is ignored */
  	result = TRACE_SIGNAL_IGNORED;
  	if (!prepare_signal(sig, t, false))
  		goto out;
  
  	ret = 0;
  	if (unlikely(!list_empty(&q->list))) {
  		/*
  		 * If an SI_TIMER entry is already queue just increment
  		 * the overrun count.
  		 */
  		BUG_ON(q->info.si_code != SI_TIMER);
  		q->info.si_overrun++;
  		result = TRACE_SIGNAL_ALREADY_PENDING;
  		goto out;
  	}
  	q->info.si_overrun = 0;
  
  	signalfd_notify(t, sig);
  	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
  	list_add_tail(&q->list, &pending->list);
  	sigaddset(&pending->signal, sig);
  	complete_signal(sig, t, type);
  	result = TRACE_SIGNAL_DELIVERED;
  out:
  	trace_signal_generate(sig, &q->info, t, type != PIDTYPE_PID, result);
  	unlock_task_sighand(t, &flags);
  ret:
  	rcu_read_unlock();
  	return ret;
  }
  
  /*
   * Let a parent know about the death of a child.
   * For a stopped/continued status change, use do_notify_parent_cldstop instead.
   *
   * Returns true if our parent ignored us and so we've switched to
   * self-reaping.
   */
  bool do_notify_parent(struct task_struct *tsk, int sig)
  {
  	struct kernel_siginfo info;
  	unsigned long flags;
  	struct sighand_struct *psig;
  	bool autoreap = false;
  	u64 utime, stime;
  
  	BUG_ON(sig == -1);
  
   	/* do_notify_parent_cldstop should have been called instead.  */
   	BUG_ON(task_is_stopped_or_traced(tsk));
  
  	BUG_ON(!tsk->ptrace &&
  	       (tsk->group_leader != tsk || !thread_group_empty(tsk)));
  
  	if (sig != SIGCHLD) {
  		/*
  		 * This is only possible if parent == real_parent.
  		 * Check if it has changed security domain.
  		 */
  		if (tsk->parent_exec_id != tsk->parent->self_exec_id)
  			sig = SIGCHLD;
  	}
  
  	clear_siginfo(&info);
  	info.si_signo = sig;
  	info.si_errno = 0;
  	/*
  	 * We are under tasklist_lock here so our parent is tied to
  	 * us and cannot change.
  	 *
  	 * task_active_pid_ns will always return the same pid namespace
  	 * until a task passes through release_task.
  	 *
  	 * write_lock() currently calls preempt_disable() which is the
  	 * same as rcu_read_lock(), but according to Oleg, this is not
  	 * correct to rely on this
  	 */
  	rcu_read_lock();
  	info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent));
  	info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns),
  				       task_uid(tsk));
  	rcu_read_unlock();
  
  	task_cputime(tsk, &utime, &stime);
  	info.si_utime = nsec_to_clock_t(utime + tsk->signal->utime);
  	info.si_stime = nsec_to_clock_t(stime + tsk->signal->stime);
  
  	info.si_status = tsk->exit_code & 0x7f;
  	if (tsk->exit_code & 0x80)
  		info.si_code = CLD_DUMPED;
  	else if (tsk->exit_code & 0x7f)
  		info.si_code = CLD_KILLED;
  	else {
  		info.si_code = CLD_EXITED;
  		info.si_status = tsk->exit_code >> 8;
  	}
  
  	psig = tsk->parent->sighand;
  	spin_lock_irqsave(&psig->siglock, flags);
  	if (!tsk->ptrace && sig == SIGCHLD &&
  	    (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
  	     (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
  		/*
  		 * We are exiting and our parent doesn't care.  POSIX.1
  		 * defines special semantics for setting SIGCHLD to SIG_IGN
  		 * or setting the SA_NOCLDWAIT flag: we should be reaped
  		 * automatically and not left for our parent's wait4 call.
  		 * Rather than having the parent do it as a magic kind of
  		 * signal handler, we just set this to tell do_exit that we
  		 * can be cleaned up without becoming a zombie.  Note that
  		 * we still call __wake_up_parent in this case, because a
  		 * blocked sys_wait4 might now return -ECHILD.
  		 *
  		 * Whether we send SIGCHLD or not for SA_NOCLDWAIT
  		 * is implementation-defined: we do (if you don't want
  		 * it, just use SIG_IGN instead).
  		 */
  		autoreap = true;
  		if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
  			sig = 0;
  	}
  	if (valid_signal(sig) && sig)
  		__group_send_sig_info(sig, &info, tsk->parent);
  	__wake_up_parent(tsk, tsk->parent);
  	spin_unlock_irqrestore(&psig->siglock, flags);
  
  	return autoreap;
  }
  
  /**
   * do_notify_parent_cldstop - notify parent of stopped/continued state change
   * @tsk: task reporting the state change
   * @for_ptracer: the notification is for ptracer
   * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
   *
   * Notify @tsk's parent that the stopped/continued state has changed.  If
   * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
   * If %true, @tsk reports to @tsk->parent which should be the ptracer.
   *
   * CONTEXT:
   * Must be called with tasklist_lock at least read locked.
   */
  static void do_notify_parent_cldstop(struct task_struct *tsk,
  				     bool for_ptracer, int why)
  {
  	struct kernel_siginfo info;
  	unsigned long flags;
  	struct task_struct *parent;
  	struct sighand_struct *sighand;
  	u64 utime, stime;
  
  	if (for_ptracer) {
  		parent = tsk->parent;
  	} else {
  		tsk = tsk->group_leader;
  		parent = tsk->real_parent;
  	}
  
  	clear_siginfo(&info);
  	info.si_signo = SIGCHLD;
  	info.si_errno = 0;
  	/*
  	 * see comment in do_notify_parent() about the following 4 lines
  	 */
  	rcu_read_lock();
  	info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(parent));
  	info.si_uid = from_kuid_munged(task_cred_xxx(parent, user_ns), task_uid(tsk));
  	rcu_read_unlock();
  
  	task_cputime(tsk, &utime, &stime);
  	info.si_utime = nsec_to_clock_t(utime);
  	info.si_stime = nsec_to_clock_t(stime);
  
   	info.si_code = why;
   	switch (why) {
   	case CLD_CONTINUED:
   		info.si_status = SIGCONT;
   		break;
   	case CLD_STOPPED:
   		info.si_status = tsk->signal->group_exit_code & 0x7f;
   		break;
   	case CLD_TRAPPED:
   		info.si_status = tsk->exit_code & 0x7f;
   		break;
   	default:
   		BUG();
   	}
  
  	sighand = parent->sighand;
  	spin_lock_irqsave(&sighand->siglock, flags);
  	if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
  	    !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
  		__group_send_sig_info(SIGCHLD, &info, parent);
  	/*
  	 * Even if SIGCHLD is not generated, we must wake up wait4 calls.
  	 */
  	__wake_up_parent(tsk, parent);
  	spin_unlock_irqrestore(&sighand->siglock, flags);
  }
  
  static inline bool may_ptrace_stop(void)
  {
  	if (!likely(current->ptrace))
  		return false;
  	/*
  	 * Are we in the middle of do_coredump?
  	 * If so and our tracer is also part of the coredump stopping
  	 * is a deadlock situation, and pointless because our tracer
  	 * is dead so don't allow us to stop.
  	 * If SIGKILL was already sent before the caller unlocked
  	 * ->siglock we must see ->core_state != NULL. Otherwise it
  	 * is safe to enter schedule().
  	 *
  	 * This is almost outdated, a task with the pending SIGKILL can't
  	 * block in TASK_TRACED. But PTRACE_EVENT_EXIT can be reported
  	 * after SIGKILL was already dequeued.
  	 */
  	if (unlikely(current->mm->core_state) &&
  	    unlikely(current->mm == current->parent->mm))
  		return false;
  
  	return true;
  }
  
  /*
   * Return non-zero if there is a SIGKILL that should be waking us up.
   * Called with the siglock held.
   */
  static bool sigkill_pending(struct task_struct *tsk)
  {
  	return sigismember(&tsk->pending.signal, SIGKILL) ||
  	       sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
  }
  
  /*
   * This must be called with current->sighand->siglock held.
   *
   * This should be the path for all ptrace stops.
   * We always set current->last_siginfo while stopped here.
   * That makes it a way to test a stopped process for
   * being ptrace-stopped vs being job-control-stopped.
   *
   * If we actually decide not to stop at all because the tracer
   * is gone, we keep current->exit_code unless clear_code.
   */
  static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t *info)
  	__releases(&current->sighand->siglock)
  	__acquires(&current->sighand->siglock)
  {
  	bool gstop_done = false;
  
  	if (arch_ptrace_stop_needed(exit_code, info)) {
  		/*
  		 * The arch code has something special to do before a
  		 * ptrace stop.  This is allowed to block, e.g. for faults
  		 * on user stack pages.  We can't keep the siglock while
  		 * calling arch_ptrace_stop, so we must release it now.
  		 * To preserve proper semantics, we must do this before
  		 * any signal bookkeeping like checking group_stop_count.
  		 * Meanwhile, a SIGKILL could come in before we retake the
  		 * siglock.  That must prevent us from sleeping in TASK_TRACED.
  		 * So after regaining the lock, we must check for SIGKILL.
  		 */
  		spin_unlock_irq(&current->sighand->siglock);
  		arch_ptrace_stop(exit_code, info);
  		spin_lock_irq(&current->sighand->siglock);
  		if (sigkill_pending(current))
  			return;
  	}
  
  	set_special_state(TASK_TRACED);
  
  	/*
  	 * We're committing to trapping.  TRACED should be visible before
  	 * TRAPPING is cleared; otherwise, the tracer might fail do_wait().
  	 * Also, transition to TRACED and updates to ->jobctl should be
  	 * atomic with respect to siglock and should be done after the arch
  	 * hook as siglock is released and regrabbed across it.
  	 *
  	 *     TRACER				    TRACEE
  	 *
  	 *     ptrace_attach()
  	 * [L]   wait_on_bit(JOBCTL_TRAPPING)	[S] set_special_state(TRACED)
  	 *     do_wait()
  	 *       set_current_state()                smp_wmb();
  	 *       ptrace_do_wait()
  	 *         wait_task_stopped()
  	 *           task_stopped_code()
  	 * [L]         task_is_traced()		[S] task_clear_jobctl_trapping();
  	 */
  	smp_wmb();
  
  	current->last_siginfo = info;
  	current->exit_code = exit_code;
  
  	/*
  	 * If @why is CLD_STOPPED, we're trapping to participate in a group
  	 * stop.  Do the bookkeeping.  Note that if SIGCONT was delievered
  	 * across siglock relocks since INTERRUPT was scheduled, PENDING
  	 * could be clear now.  We act as if SIGCONT is received after
  	 * TASK_TRACED is entered - ignore it.
  	 */
  	if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))
  		gstop_done = task_participate_group_stop(current);
  
  	/* any trap clears pending STOP trap, STOP trap clears NOTIFY */
  	task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP);
  	if (info && info->si_code >> 8 == PTRACE_EVENT_STOP)
  		task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY);
  
  	/* entering a trap, clear TRAPPING */
  	task_clear_jobctl_trapping(current);
  
  	spin_unlock_irq(&current->sighand->siglock);
  	read_lock(&tasklist_lock);
  	if (may_ptrace_stop()) {
  		/*
  		 * Notify parents of the stop.
  		 *
  		 * While ptraced, there are two parents - the ptracer and
  		 * the real_parent of the group_leader.  The ptracer should
  		 * know about every stop while the real parent is only
  		 * interested in the completion of group stop.  The states
  		 * for the two don't interact with each other.  Notify
  		 * separately unless they're gonna be duplicates.
  		 */
  		do_notify_parent_cldstop(current, true, why);
  		if (gstop_done && ptrace_reparented(current))
  			do_notify_parent_cldstop(current, false, why);
  
  		/*
  		 * Don't want to allow preemption here, because
  		 * sys_ptrace() needs this task to be inactive.
  		 *
  		 * XXX: implement read_unlock_no_resched().
  		 */
  		preempt_disable();
  		read_unlock(&tasklist_lock);
  		preempt_enable_no_resched();
  		freezable_schedule();
  	} else {
  		/*
  		 * By the time we got the lock, our tracer went away.
  		 * Don't drop the lock yet, another tracer may come.
  		 *
  		 * If @gstop_done, the ptracer went away between group stop
  		 * completion and here.  During detach, it would have set
  		 * JOBCTL_STOP_PENDING on us and we'll re-enter
  		 * TASK_STOPPED in do_signal_stop() on return, so notifying
  		 * the real parent of the group stop completion is enough.
  		 */
  		if (gstop_done)
  			do_notify_parent_cldstop(current, false, why);
  
  		/* tasklist protects us from ptrace_freeze_traced() */
  		__set_current_state(TASK_RUNNING);
  		if (clear_code)
  			current->exit_code = 0;
  		read_unlock(&tasklist_lock);
  	}
  
  	/*
  	 * We are back.  Now reacquire the siglock before touching
  	 * last_siginfo, so that we are sure to have synchronized with
  	 * any signal-sending on another CPU that wants to examine it.
  	 */
  	spin_lock_irq(&current->sighand->siglock);
  	current->last_siginfo = NULL;
  
  	/* LISTENING can be set only during STOP traps, clear it */
  	current->jobctl &= ~JOBCTL_LISTENING;
  
  	/*
  	 * Queued signals ignored us while we were stopped for tracing.
  	 * So check for any that we should take before resuming user mode.
  	 * This sets TIF_SIGPENDING, but never clears it.
  	 */
  	recalc_sigpending_tsk(current);
  }
  
  static void ptrace_do_notify(int signr, int exit_code, int why)
  {
  	kernel_siginfo_t info;
  
  	clear_siginfo(&info);
  	info.si_signo = signr;
  	info.si_code = exit_code;
  	info.si_pid = task_pid_vnr(current);
  	info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
  
  	/* Let the debugger run.  */
  	ptrace_stop(exit_code, why, 1, &info);
  }
  
  void ptrace_notify(int exit_code)
  {
  	BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
  	if (unlikely(current->task_works))
  		task_work_run();
  
  	spin_lock_irq(&current->sighand->siglock);
  	ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED);
  	spin_unlock_irq(&current->sighand->siglock);
  }
  
  /**
   * do_signal_stop - handle group stop for SIGSTOP and other stop signals
   * @signr: signr causing group stop if initiating
   *
   * If %JOBCTL_STOP_PENDING is not set yet, initiate group stop with @signr
   * and participate in it.  If already set, participate in the existing
   * group stop.  If participated in a group stop (and thus slept), %true is
   * returned with siglock released.
   *
   * If ptraced, this function doesn't handle stop itself.  Instead,
   * %JOBCTL_TRAP_STOP is scheduled and %false is returned with siglock
   * untouched.  The caller must ensure that INTERRUPT trap handling takes
   * places afterwards.
   *
   * CONTEXT:
   * Must be called with @current->sighand->siglock held, which is released
   * on %true return.
   *
   * RETURNS:
   * %false if group stop is already cancelled or ptrace trap is scheduled.
   * %true if participated in group stop.
   */
  static bool do_signal_stop(int signr)
  	__releases(&current->sighand->siglock)
  {
  	struct signal_struct *sig = current->signal;
  
  	if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
  		unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
  		struct task_struct *t;
  
  		/* signr will be recorded in task->jobctl for retries */
  		WARN_ON_ONCE(signr & ~JOBCTL_STOP_SIGMASK);
  
  		if (!likely(current->jobctl & JOBCTL_STOP_DEQUEUED) ||
  		    unlikely(signal_group_exit(sig)))
  			return false;
  		/*
  		 * There is no group stop already in progress.  We must
  		 * initiate one now.
  		 *
  		 * While ptraced, a task may be resumed while group stop is
  		 * still in effect and then receive a stop signal and
  		 * initiate another group stop.  This deviates from the
  		 * usual behavior as two consecutive stop signals can't
  		 * cause two group stops when !ptraced.  That is why we
  		 * also check !task_is_stopped(t) below.
  		 *
  		 * The condition can be distinguished by testing whether
  		 * SIGNAL_STOP_STOPPED is already set.  Don't generate
  		 * group_exit_code in such case.
  		 *
  		 * This is not necessary for SIGNAL_STOP_CONTINUED because
  		 * an intervening stop signal is required to cause two
  		 * continued events regardless of ptrace.
  		 */
  		if (!(sig->flags & SIGNAL_STOP_STOPPED))
  			sig->group_exit_code = signr;
  
  		sig->group_stop_count = 0;
  
  		if (task_set_jobctl_pending(current, signr | gstop))
  			sig->group_stop_count++;
  
  		t = current;
  		while_each_thread(current, t) {
  			/*
  			 * Setting state to TASK_STOPPED for a group
  			 * stop is always done with the siglock held,
  			 * so this check has no races.
  			 */
  			if (!task_is_stopped(t) &&
  			    task_set_jobctl_pending(t, signr | gstop)) {
  				sig->group_stop_count++;
  				if (likely(!(t->ptrace & PT_SEIZED)))
  					signal_wake_up(t, 0);
  				else
  					ptrace_trap_notify(t);
  			}
  		}
  	}
  
  	if (likely(!current->ptrace)) {
  		int notify = 0;
  
  		/*
  		 * If there are no other threads in the group, or if there
  		 * is a group stop in progress and we are the last to stop,
  		 * report to the parent.
  		 */
  		if (task_participate_group_stop(current))
  			notify = CLD_STOPPED;
  
  		set_special_state(TASK_STOPPED);
  		spin_unlock_irq(&current->sighand->siglock);
  
  		/*
  		 * Notify the parent of the group stop completion.  Because
  		 * we're not holding either the siglock or tasklist_lock
  		 * here, ptracer may attach inbetween; however, this is for
  		 * group stop and should always be delivered to the real
  		 * parent of the group leader.  The new ptracer will get
  		 * its notification when this task transitions into
  		 * TASK_TRACED.
  		 */
  		if (notify) {
  			read_lock(&tasklist_lock);
  			do_notify_parent_cldstop(current, false, notify);
  			read_unlock(&tasklist_lock);
  		}
  
  		/* Now we don't run again until woken by SIGCONT or SIGKILL */
  		freezable_schedule();
  		return true;
  	} else {
  		/*
  		 * While ptraced, group stop is handled by STOP trap.
  		 * Schedule it and let the caller deal with it.
  		 */
  		task_set_jobctl_pending(current, JOBCTL_TRAP_STOP);
  		return false;
  	}
  }
  
  /**
   * do_jobctl_trap - take care of ptrace jobctl traps
   *
   * When PT_SEIZED, it's used for both group stop and explicit
   * SEIZE/INTERRUPT traps.  Both generate PTRACE_EVENT_STOP trap with
   * accompanying siginfo.  If stopped, lower eight bits of exit_code contain
   * the stop signal; otherwise, %SIGTRAP.
   *
   * When !PT_SEIZED, it's used only for group stop trap with stop signal
   * number as exit_code and no siginfo.
   *
   * CONTEXT:
   * Must be called with @current->sighand->siglock held, which may be
   * released and re-acquired before returning with intervening sleep.
   */
  static void do_jobctl_trap(void)
  {
  	struct signal_struct *signal = current->signal;
  	int signr = current->jobctl & JOBCTL_STOP_SIGMASK;
  
  	if (current->ptrace & PT_SEIZED) {
  		if (!signal->group_stop_count &&
  		    !(signal->flags & SIGNAL_STOP_STOPPED))
  			signr = SIGTRAP;
  		WARN_ON_ONCE(!signr);
  		ptrace_do_notify(signr, signr | (PTRACE_EVENT_STOP << 8),
  				 CLD_STOPPED);
  	} else {
  		WARN_ON_ONCE(!signr);
  		ptrace_stop(signr, CLD_STOPPED, 0, NULL);
  		current->exit_code = 0;
  	}
  }
  
  static int ptrace_signal(int signr, kernel_siginfo_t *info)
  {
  	/*
  	 * We do not check sig_kernel_stop(signr) but set this marker
  	 * unconditionally because we do not know whether debugger will
  	 * change signr. This flag has no meaning unless we are going
  	 * to stop after return from ptrace_stop(). In this case it will
  	 * be checked in do_signal_stop(), we should only stop if it was
  	 * not cleared by SIGCONT while we were sleeping. See also the
  	 * comment in dequeue_signal().
  	 */
  	current->jobctl |= JOBCTL_STOP_DEQUEUED;
  	ptrace_stop(signr, CLD_TRAPPED, 0, info);
  
  	/* We're back.  Did the debugger cancel the sig?  */
  	signr = current->exit_code;
  	if (signr == 0)
  		return signr;
  
  	current->exit_code = 0;
  
  	/*
  	 * Update the siginfo structure if the signal has
  	 * changed.  If the debugger wanted something
  	 * specific in the siginfo structure then it should
  	 * have updated *info via PTRACE_SETSIGINFO.
  	 */
  	if (signr != info->si_signo) {
  		clear_siginfo(info);
  		info->si_signo = signr;
  		info->si_errno = 0;
  		info->si_code = SI_USER;
  		rcu_read_lock();
  		info->si_pid = task_pid_vnr(current->parent);
  		info->si_uid = from_kuid_munged(current_user_ns(),
  						task_uid(current->parent));
  		rcu_read_unlock();
  	}
  
  	/* If the (new) signal is now blocked, requeue it.  */
  	if (sigismember(&current->blocked, signr)) {
  		send_signal(signr, info, current, PIDTYPE_PID);
  		signr = 0;
  	}
  
  	return signr;
  }
  
  bool get_signal(struct ksignal *ksig)
  {
  	struct sighand_struct *sighand = current->sighand;
  	struct signal_struct *signal = current->signal;
  	int signr;
  
  	if (unlikely(current->task_works))
  		task_work_run();
  
  	if (unlikely(uprobe_deny_signal()))
  		return false;
  
  	/*
  	 * Do this once, we can't return to user-mode if freezing() == T.
  	 * do_signal_stop() and ptrace_stop() do freezable_schedule() and
  	 * thus do not need another check after return.
  	 */
  	try_to_freeze();
  
  relock:
  	spin_lock_irq(&sighand->siglock);
  	/*
  	 * Every stopped thread goes here after wakeup. Check to see if
  	 * we should notify the parent, prepare_signal(SIGCONT) encodes
  	 * the CLD_ si_code into SIGNAL_CLD_MASK bits.
  	 */
  	if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
  		int why;
  
  		if (signal->flags & SIGNAL_CLD_CONTINUED)
  			why = CLD_CONTINUED;
  		else
  			why = CLD_STOPPED;
  
  		signal->flags &= ~SIGNAL_CLD_MASK;
  
  		spin_unlock_irq(&sighand->siglock);
  
  		/*
  		 * Notify the parent that we're continuing.  This event is
  		 * always per-process and doesn't make whole lot of sense
  		 * for ptracers, who shouldn't consume the state via
  		 * wait(2) either, but, for backward compatibility, notify
  		 * the ptracer of the group leader too unless it's gonna be
  		 * a duplicate.
  		 */
  		read_lock(&tasklist_lock);
  		do_notify_parent_cldstop(current, false, why);
  
  		if (ptrace_reparented(current->group_leader))
  			do_notify_parent_cldstop(current->group_leader,
  						true, why);
  		read_unlock(&tasklist_lock);
  
  		goto relock;
  	}
  
  	/* Has this task already been marked for death? */
  	if (signal_group_exit(signal)) {
  		ksig->info.si_signo = signr = SIGKILL;
  		sigdelset(&current->pending.signal, SIGKILL);
  		recalc_sigpending();
  		goto fatal;
  	}
  
  	for (;;) {
  		struct k_sigaction *ka;
  
  		if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
  		    do_signal_stop(0))
  			goto relock;
  
  		if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
  			do_jobctl_trap();
  			spin_unlock_irq(&sighand->siglock);
  			goto relock;
  		}
  
  		/*
  		 * Signals generated by the execution of an instruction
  		 * need to be delivered before any other pending signals
  		 * so that the instruction pointer in the signal stack
  		 * frame points to the faulting instruction.
  		 */
  		signr = dequeue_synchronous_signal(&ksig->info);
  		if (!signr)
  			signr = dequeue_signal(current, &current->blocked, &ksig->info);
  
  		if (!signr)
  			break; /* will return 0 */
  
  		if (unlikely(current->ptrace) && signr != SIGKILL) {
  			signr = ptrace_signal(signr, &ksig->info);
  			if (!signr)
  				continue;
  		}
  
  		ka = &sighand->action[signr-1];
  
  		/* Trace actually delivered signals. */
  		trace_signal_deliver(signr, &ksig->info, ka);
  
  		if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
  			continue;
  		if (ka->sa.sa_handler != SIG_DFL) {
  			/* Run the handler.  */
  			ksig->ka = *ka;
  
  			if (ka->sa.sa_flags & SA_ONESHOT)
  				ka->sa.sa_handler = SIG_DFL;
  
  			break; /* will return non-zero "signr" value */
  		}
  
  		/*
  		 * Now we are doing the default action for this signal.
  		 */
  		if (sig_kernel_ignore(signr)) /* Default is nothing. */
  			continue;
  
  		/*
  		 * Global init gets no signals it doesn't want.
  		 * Container-init gets no signals it doesn't want from same
  		 * container.
  		 *
  		 * Note that if global/container-init sees a sig_kernel_only()
  		 * signal here, the signal must have been generated internally
  		 * or must have come from an ancestor namespace. In either
  		 * case, the signal cannot be dropped.
  		 */
  		if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
  				!sig_kernel_only(signr))
  			continue;
  
  		if (sig_kernel_stop(signr)) {
  			/*
  			 * The default action is to stop all threads in
  			 * the thread group.  The job control signals
  			 * do nothing in an orphaned pgrp, but SIGSTOP
  			 * always works.  Note that siglock needs to be
  			 * dropped during the call to is_orphaned_pgrp()
  			 * because of lock ordering with tasklist_lock.
  			 * This allows an intervening SIGCONT to be posted.
  			 * We need to check for that and bail out if necessary.
  			 */
  			if (signr != SIGSTOP) {
  				spin_unlock_irq(&sighand->siglock);
  
  				/* signals can be posted during this window */
  
  				if (is_current_pgrp_orphaned())
  					goto relock;
  
  				spin_lock_irq(&sighand->siglock);
  			}
  
  			if (likely(do_signal_stop(ksig->info.si_signo))) {
  				/* It released the siglock.  */
  				goto relock;
  			}
  
  			/*
  			 * We didn't actually stop, due to a race
  			 * with SIGCONT or something like that.
  			 */
  			continue;
  		}
  
  	fatal:
  		spin_unlock_irq(&sighand->siglock);
  
  		/*
  		 * Anything else is fatal, maybe with a core dump.
  		 */
  		current->flags |= PF_SIGNALED;
  
  		if (sig_kernel_coredump(signr)) {
  			if (print_fatal_signals)
  				print_fatal_signal(ksig->info.si_signo);
  			proc_coredump_connector(current);
  			/*
  			 * If it was able to dump core, this kills all
  			 * other threads in the group and synchronizes with
  			 * their demise.  If we lost the race with another
  			 * thread getting here, it set group_exit_code
  			 * first and our do_group_exit call below will use
  			 * that value and ignore the one we pass it.
  			 */
  			do_coredump(&ksig->info);
  		}
  
  		/*
  		 * Death signals, no core dump.
  		 */
  		do_group_exit(ksig->info.si_signo);
  		/* NOTREACHED */
  	}
  	spin_unlock_irq(&sighand->siglock);
  
  	ksig->sig = signr;
  	return ksig->sig > 0;
  }
  
  /**
   * signal_delivered - 
   * @ksig:		kernel signal struct
   * @stepping:		nonzero if debugger single-step or block-step in use
   *
   * This function should be called when a signal has successfully been
   * delivered. It updates the blocked signals accordingly (@ksig->ka.sa.sa_mask
   * is always blocked, and the signal itself is blocked unless %SA_NODEFER
   * is set in @ksig->ka.sa.sa_flags.  Tracing is notified.
   */
  static void signal_delivered(struct ksignal *ksig, int stepping)
  {
  	sigset_t blocked;
  
  	/* A signal was successfully delivered, and the
  	   saved sigmask was stored on the signal frame,
  	   and will be restored by sigreturn.  So we can
  	   simply clear the restore sigmask flag.  */
  	clear_restore_sigmask();
  
  	sigorsets(&blocked, &current->blocked, &ksig->ka.sa.sa_mask);
  	if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
  		sigaddset(&blocked, ksig->sig);
  	set_current_blocked(&blocked);
  	tracehook_signal_handler(stepping);
  }
  
  void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
  {
  	if (failed)
  		force_sigsegv(ksig->sig, current);
  	else
  		signal_delivered(ksig, stepping);
  }
  
  /*
   * It could be that complete_signal() picked us to notify about the
   * group-wide signal. Other threads should be notified now to take
   * the shared signals in @which since we will not.
   */
  static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
  {
  	sigset_t retarget;
  	struct task_struct *t;
  
  	sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
  	if (sigisemptyset(&retarget))
  		return;
  
  	t = tsk;
  	while_each_thread(tsk, t) {
  		if (t->flags & PF_EXITING)
  			continue;
  
  		if (!has_pending_signals(&retarget, &t->blocked))
  			continue;
  		/* Remove the signals this thread can handle. */
  		sigandsets(&retarget, &retarget, &t->blocked);
  
  		if (!signal_pending(t))
  			signal_wake_up(t, 0);
  
  		if (sigisemptyset(&retarget))
  			break;
  	}
  }
  
  void exit_signals(struct task_struct *tsk)
  {
  	int group_stop = 0;
  	sigset_t unblocked;
  
  	/*
  	 * @tsk is about to have PF_EXITING set - lock out users which
  	 * expect stable threadgroup.
  	 */
  	cgroup_threadgroup_change_begin(tsk);
  
  	if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
  		tsk->flags |= PF_EXITING;
  		cgroup_threadgroup_change_end(tsk);
  		return;
  	}
  
  	spin_lock_irq(&tsk->sighand->siglock);
  	/*
  	 * From now this task is not visible for group-wide signals,
  	 * see wants_signal(), do_signal_stop().
  	 */
  	tsk->flags |= PF_EXITING;
  
  	cgroup_threadgroup_change_end(tsk);
  
  	if (!signal_pending(tsk))
  		goto out;
  
  	unblocked = tsk->blocked;
  	signotset(&unblocked);
  	retarget_shared_pending(tsk, &unblocked);
  
  	if (unlikely(tsk->jobctl & JOBCTL_STOP_PENDING) &&
  	    task_participate_group_stop(tsk))
  		group_stop = CLD_STOPPED;
  out:
  	spin_unlock_irq(&tsk->sighand->siglock);
  
  	/*
  	 * If group stop has completed, deliver the notification.  This
  	 * should always go to the real parent of the group leader.
  	 */
  	if (unlikely(group_stop)) {
  		read_lock(&tasklist_lock);
  		do_notify_parent_cldstop(tsk, false, group_stop);
  		read_unlock(&tasklist_lock);
  	}
  }
  
  /*
   * System call entry points.
   */
  
  /**
   *  sys_restart_syscall - restart a system call
   */
  SYSCALL_DEFINE0(restart_syscall)
  {
  	struct restart_block *restart = &current->restart_block;
  	return restart->fn(restart);
  }
  
  long do_no_restart_syscall(struct restart_block *param)
  {
  	return -EINTR;
  }
  
  static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
  {
  	if (signal_pending(tsk) && !thread_group_empty(tsk)) {
  		sigset_t newblocked;
  		/* A set of now blocked but previously unblocked signals. */
  		sigandnsets(&newblocked, newset, &current->blocked);
  		retarget_shared_pending(tsk, &newblocked);
  	}
  	tsk->blocked = *newset;
  	recalc_sigpending();
  }
  
  /**
   * set_current_blocked - change current->blocked mask
   * @newset: new mask
   *
   * It is wrong to change ->blocked directly, this helper should be used
   * to ensure the process can't miss a shared signal we are going to block.
   */
  void set_current_blocked(sigset_t *newset)
  {
  	sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP));
  	__set_current_blocked(newset);
  }
  
  void __set_current_blocked(const sigset_t *newset)
  {
  	struct task_struct *tsk = current;
  
  	/*
  	 * In case the signal mask hasn't changed, there is nothing we need
  	 * to do. The current->blocked shouldn't be modified by other task.
  	 */
  	if (sigequalsets(&tsk->blocked, newset))
  		return;
  
  	spin_lock_irq(&tsk->sighand->siglock);
  	__set_task_blocked(tsk, newset);
  	spin_unlock_irq(&tsk->sighand->siglock);
  }
  
  /*
   * This is also useful for kernel threads that want to temporarily
   * (or permanently) block certain signals.
   *
   * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
   * interface happily blocks "unblockable" signals like SIGKILL
   * and friends.
   */
  int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
  {
  	struct task_struct *tsk = current;
  	sigset_t newset;
  
  	/* Lockless, only current can change ->blocked, never from irq */
  	if (oldset)
  		*oldset = tsk->blocked;
  
  	switch (how) {
  	case SIG_BLOCK:
  		sigorsets(&newset, &tsk->blocked, set);
  		break;
  	case SIG_UNBLOCK:
  		sigandnsets(&newset, &tsk->blocked, set);
  		break;
  	case SIG_SETMASK:
  		newset = *set;
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	__set_current_blocked(&newset);
  	return 0;
  }
  EXPORT_SYMBOL(sigprocmask);
  
  /*
   * The api helps set app-provided sigmasks.
   *
   * This is useful for syscalls such as ppoll, pselect, io_pgetevents and
   * epoll_pwait where a new sigmask is passed from userland for the syscalls.
   */
  int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set,
  		     sigset_t *oldset, size_t sigsetsize)
  {
  	if (!usigmask)
  		return 0;
  
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  	if (copy_from_user(set, usigmask, sizeof(sigset_t)))
  		return -EFAULT;
  
  	*oldset = current->blocked;
  	set_current_blocked(set);
  
  	return 0;
  }
  EXPORT_SYMBOL(set_user_sigmask);
  
  #ifdef CONFIG_COMPAT
  int set_compat_user_sigmask(const compat_sigset_t __user *usigmask,
  			    sigset_t *set, sigset_t *oldset,
  			    size_t sigsetsize)
  {
  	if (!usigmask)
  		return 0;
  
  	if (sigsetsize != sizeof(compat_sigset_t))
  		return -EINVAL;
  	if (get_compat_sigset(set, usigmask))
  		return -EFAULT;
  
  	*oldset = current->blocked;
  	set_current_blocked(set);
  
  	return 0;
  }
  EXPORT_SYMBOL(set_compat_user_sigmask);
  #endif
  
  /*
   * restore_user_sigmask:
   * usigmask: sigmask passed in from userland.
   * sigsaved: saved sigmask when the syscall started and changed the sigmask to
   *           usigmask.
   *
   * This is useful for syscalls such as ppoll, pselect, io_pgetevents and
   * epoll_pwait where a new sigmask is passed in from userland for the syscalls.
   */
  void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
  {
  
  	if (!usigmask)
  		return;
  	/*
  	 * When signals are pending, do not restore them here.
  	 * Restoring sigmask here can lead to delivering signals that the above
  	 * syscalls are intended to block because of the sigmask passed in.
  	 */
  	if (signal_pending(current)) {
  		current->saved_sigmask = *sigsaved;
  		set_restore_sigmask();
  		return;
  	}
  
  	/*
  	 * This is needed because the fast syscall return path does not restore
  	 * saved_sigmask when signals are not pending.
  	 */
  	set_current_blocked(sigsaved);
  }
  EXPORT_SYMBOL(restore_user_sigmask);
  
  /**
   *  sys_rt_sigprocmask - change the list of currently blocked signals
   *  @how: whether to add, remove, or set signals
   *  @nset: stores pending signals
   *  @oset: previous value of signal mask if non-null
   *  @sigsetsize: size of sigset_t type
   */
  SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
  		sigset_t __user *, oset, size_t, sigsetsize)
  {
  	sigset_t old_set, new_set;
  	int error;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	old_set = current->blocked;
  
  	if (nset) {
  		if (copy_from_user(&new_set, nset, sizeof(sigset_t)))
  			return -EFAULT;
  		sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
  
  		error = sigprocmask(how, &new_set, NULL);
  		if (error)
  			return error;
  	}
  
  	if (oset) {
  		if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
  			return -EFAULT;
  	}
  
  	return 0;
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
  		compat_sigset_t __user *, oset, compat_size_t, sigsetsize)
  {
  	sigset_t old_set = current->blocked;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (nset) {
  		sigset_t new_set;
  		int error;
  		if (get_compat_sigset(&new_set, nset))
  			return -EFAULT;
  		sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
  
  		error = sigprocmask(how, &new_set, NULL);
  		if (error)
  			return error;
  	}
  	return oset ? put_compat_sigset(oset, &old_set, sizeof(*oset)) : 0;
  }
  #endif
  
  static void do_sigpending(sigset_t *set)
  {
  	spin_lock_irq(&current->sighand->siglock);
  	sigorsets(set, &current->pending.signal,
  		  &current->signal->shared_pending.signal);
  	spin_unlock_irq(&current->sighand->siglock);
  
  	/* Outside the lock because only this thread touches it.  */
  	sigandsets(set, &current->blocked, set);
  }
  
  /**
   *  sys_rt_sigpending - examine a pending signal that has been raised
   *			while blocked
   *  @uset: stores pending signals
   *  @sigsetsize: size of sigset_t type or larger
   */
  SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, uset, size_t, sigsetsize)
  {
  	sigset_t set;
  
  	if (sigsetsize > sizeof(*uset))
  		return -EINVAL;
  
  	do_sigpending(&set);
  
  	if (copy_to_user(uset, &set, sigsetsize))
  		return -EFAULT;
  
  	return 0;
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE2(rt_sigpending, compat_sigset_t __user *, uset,
  		compat_size_t, sigsetsize)
  {
  	sigset_t set;
  
  	if (sigsetsize > sizeof(*uset))
  		return -EINVAL;
  
  	do_sigpending(&set);
  
  	return put_compat_sigset(uset, &set, sigsetsize);
  }
  #endif
  
  static const struct {
  	unsigned char limit, layout;
  } sig_sicodes[] = {
  	[SIGILL]  = { NSIGILL,  SIL_FAULT },
  	[SIGFPE]  = { NSIGFPE,  SIL_FAULT },
  	[SIGSEGV] = { NSIGSEGV, SIL_FAULT },
  	[SIGBUS]  = { NSIGBUS,  SIL_FAULT },
  	[SIGTRAP] = { NSIGTRAP, SIL_FAULT },
  #if defined(SIGEMT)
  	[SIGEMT]  = { NSIGEMT,  SIL_FAULT },
  #endif
  	[SIGCHLD] = { NSIGCHLD, SIL_CHLD },
  	[SIGPOLL] = { NSIGPOLL, SIL_POLL },
  	[SIGSYS]  = { NSIGSYS,  SIL_SYS },
  };
  
  static bool known_siginfo_layout(unsigned sig, int si_code)
  {
  	if (si_code == SI_KERNEL)
  		return true;
  	else if ((si_code > SI_USER)) {
  		if (sig_specific_sicodes(sig)) {
  			if (si_code <= sig_sicodes[sig].limit)
  				return true;
  		}
  		else if (si_code <= NSIGPOLL)
  			return true;
  	}
  	else if (si_code >= SI_DETHREAD)
  		return true;
  	else if (si_code == SI_ASYNCNL)
  		return true;
  	return false;
  }
  
  enum siginfo_layout siginfo_layout(unsigned sig, int si_code)
  {
  	enum siginfo_layout layout = SIL_KILL;
  	if ((si_code > SI_USER) && (si_code < SI_KERNEL)) {
  		if ((sig < ARRAY_SIZE(sig_sicodes)) &&
  		    (si_code <= sig_sicodes[sig].limit)) {
  			layout = sig_sicodes[sig].layout;
  			/* Handle the exceptions */
  			if ((sig == SIGBUS) &&
  			    (si_code >= BUS_MCEERR_AR) && (si_code <= BUS_MCEERR_AO))
  				layout = SIL_FAULT_MCEERR;
  			else if ((sig == SIGSEGV) && (si_code == SEGV_BNDERR))
  				layout = SIL_FAULT_BNDERR;
  #ifdef SEGV_PKUERR
  			else if ((sig == SIGSEGV) && (si_code == SEGV_PKUERR))
  				layout = SIL_FAULT_PKUERR;
  #endif
  		}
  		else if (si_code <= NSIGPOLL)
  			layout = SIL_POLL;
  	} else {
  		if (si_code == SI_TIMER)
  			layout = SIL_TIMER;
  		else if (si_code == SI_SIGIO)
  			layout = SIL_POLL;
  		else if (si_code < 0)
  			layout = SIL_RT;
  	}
  	return layout;
  }
  
  static inline char __user *si_expansion(const siginfo_t __user *info)
  {
  	return ((char __user *)info) + sizeof(struct kernel_siginfo);
  }
  
  int copy_siginfo_to_user(siginfo_t __user *to, const kernel_siginfo_t *from)
  {
  	char __user *expansion = si_expansion(to);
  	if (copy_to_user(to, from , sizeof(struct kernel_siginfo)))
  		return -EFAULT;
  	if (clear_user(expansion, SI_EXPANSION_SIZE))
  		return -EFAULT;
  	return 0;
  }
  
  static int post_copy_siginfo_from_user(kernel_siginfo_t *info,
  				       const siginfo_t __user *from)
  {
  	if (unlikely(!known_siginfo_layout(info->si_signo, info->si_code))) {
  		char __user *expansion = si_expansion(from);
  		char buf[SI_EXPANSION_SIZE];
  		int i;
  		/*
  		 * An unknown si_code might need more than
  		 * sizeof(struct kernel_siginfo) bytes.  Verify all of the
  		 * extra bytes are 0.  This guarantees copy_siginfo_to_user
  		 * will return this data to userspace exactly.
  		 */
  		if (copy_from_user(&buf, expansion, SI_EXPANSION_SIZE))
  			return -EFAULT;
  		for (i = 0; i < SI_EXPANSION_SIZE; i++) {
  			if (buf[i] != 0)
  				return -E2BIG;
  		}
  	}
  	return 0;
  }
  
  static int __copy_siginfo_from_user(int signo, kernel_siginfo_t *to,
  				    const siginfo_t __user *from)
  {
  	if (copy_from_user(to, from, sizeof(struct kernel_siginfo)))
  		return -EFAULT;
  	to->si_signo = signo;
  	return post_copy_siginfo_from_user(to, from);
  }
  
  int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from)
  {
  	if (copy_from_user(to, from, sizeof(struct kernel_siginfo)))
  		return -EFAULT;
  	return post_copy_siginfo_from_user(to, from);
  }
  
  #ifdef CONFIG_COMPAT
  int copy_siginfo_to_user32(struct compat_siginfo __user *to,
  			   const struct kernel_siginfo *from)
  #if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
  {
  	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
  }
  int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
  			     const struct kernel_siginfo *from, bool x32_ABI)
  #endif
  {
  	struct compat_siginfo new;
  	memset(&new, 0, sizeof(new));
  
  	new.si_signo = from->si_signo;
  	new.si_errno = from->si_errno;
  	new.si_code  = from->si_code;
  	switch(siginfo_layout(from->si_signo, from->si_code)) {
  	case SIL_KILL:
  		new.si_pid = from->si_pid;
  		new.si_uid = from->si_uid;
  		break;
  	case SIL_TIMER:
  		new.si_tid     = from->si_tid;
  		new.si_overrun = from->si_overrun;
  		new.si_int     = from->si_int;
  		break;
  	case SIL_POLL:
  		new.si_band = from->si_band;
  		new.si_fd   = from->si_fd;
  		break;
  	case SIL_FAULT:
  		new.si_addr = ptr_to_compat(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		new.si_trapno = from->si_trapno;
  #endif
  		break;
  	case SIL_FAULT_MCEERR:
  		new.si_addr = ptr_to_compat(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		new.si_trapno = from->si_trapno;
  #endif
  		new.si_addr_lsb = from->si_addr_lsb;
  		break;
  	case SIL_FAULT_BNDERR:
  		new.si_addr = ptr_to_compat(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		new.si_trapno = from->si_trapno;
  #endif
  		new.si_lower = ptr_to_compat(from->si_lower);
  		new.si_upper = ptr_to_compat(from->si_upper);
  		break;
  	case SIL_FAULT_PKUERR:
  		new.si_addr = ptr_to_compat(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		new.si_trapno = from->si_trapno;
  #endif
  		new.si_pkey = from->si_pkey;
  		break;
  	case SIL_CHLD:
  		new.si_pid    = from->si_pid;
  		new.si_uid    = from->si_uid;
  		new.si_status = from->si_status;
  #ifdef CONFIG_X86_X32_ABI
  		if (x32_ABI) {
  			new._sifields._sigchld_x32._utime = from->si_utime;
  			new._sifields._sigchld_x32._stime = from->si_stime;
  		} else
  #endif
  		{
  			new.si_utime = from->si_utime;
  			new.si_stime = from->si_stime;
  		}
  		break;
  	case SIL_RT:
  		new.si_pid = from->si_pid;
  		new.si_uid = from->si_uid;
  		new.si_int = from->si_int;
  		break;
  	case SIL_SYS:
  		new.si_call_addr = ptr_to_compat(from->si_call_addr);
  		new.si_syscall   = from->si_syscall;
  		new.si_arch      = from->si_arch;
  		break;
  	}
  
  	if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
  		return -EFAULT;
  
  	return 0;
  }
  
  static int post_copy_siginfo_from_user32(kernel_siginfo_t *to,
  					 const struct compat_siginfo *from)
  {
  	clear_siginfo(to);
  	to->si_signo = from->si_signo;
  	to->si_errno = from->si_errno;
  	to->si_code  = from->si_code;
  	switch(siginfo_layout(from->si_signo, from->si_code)) {
  	case SIL_KILL:
  		to->si_pid = from->si_pid;
  		to->si_uid = from->si_uid;
  		break;
  	case SIL_TIMER:
  		to->si_tid     = from->si_tid;
  		to->si_overrun = from->si_overrun;
  		to->si_int     = from->si_int;
  		break;
  	case SIL_POLL:
  		to->si_band = from->si_band;
  		to->si_fd   = from->si_fd;
  		break;
  	case SIL_FAULT:
  		to->si_addr = compat_ptr(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		to->si_trapno = from->si_trapno;
  #endif
  		break;
  	case SIL_FAULT_MCEERR:
  		to->si_addr = compat_ptr(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		to->si_trapno = from->si_trapno;
  #endif
  		to->si_addr_lsb = from->si_addr_lsb;
  		break;
  	case SIL_FAULT_BNDERR:
  		to->si_addr = compat_ptr(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		to->si_trapno = from->si_trapno;
  #endif
  		to->si_lower = compat_ptr(from->si_lower);
  		to->si_upper = compat_ptr(from->si_upper);
  		break;
  	case SIL_FAULT_PKUERR:
  		to->si_addr = compat_ptr(from->si_addr);
  #ifdef __ARCH_SI_TRAPNO
  		to->si_trapno = from->si_trapno;
  #endif
  		to->si_pkey = from->si_pkey;
  		break;
  	case SIL_CHLD:
  		to->si_pid    = from->si_pid;
  		to->si_uid    = from->si_uid;
  		to->si_status = from->si_status;
  #ifdef CONFIG_X86_X32_ABI
  		if (in_x32_syscall()) {
  			to->si_utime = from->_sifields._sigchld_x32._utime;
  			to->si_stime = from->_sifields._sigchld_x32._stime;
  		} else
  #endif
  		{
  			to->si_utime = from->si_utime;
  			to->si_stime = from->si_stime;
  		}
  		break;
  	case SIL_RT:
  		to->si_pid = from->si_pid;
  		to->si_uid = from->si_uid;
  		to->si_int = from->si_int;
  		break;
  	case SIL_SYS:
  		to->si_call_addr = compat_ptr(from->si_call_addr);
  		to->si_syscall   = from->si_syscall;
  		to->si_arch      = from->si_arch;
  		break;
  	}
  	return 0;
  }
  
  static int __copy_siginfo_from_user32(int signo, struct kernel_siginfo *to,
  				      const struct compat_siginfo __user *ufrom)
  {
  	struct compat_siginfo from;
  
  	if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo)))
  		return -EFAULT;
  
  	from.si_signo = signo;
  	return post_copy_siginfo_from_user32(to, &from);
  }
  
  int copy_siginfo_from_user32(struct kernel_siginfo *to,
  			     const struct compat_siginfo __user *ufrom)
  {
  	struct compat_siginfo from;
  
  	if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo)))
  		return -EFAULT;
  
  	return post_copy_siginfo_from_user32(to, &from);
  }
  #endif /* CONFIG_COMPAT */
  
  /**
   *  do_sigtimedwait - wait for queued signals specified in @which
   *  @which: queued signals to wait for
   *  @info: if non-null, the signal's siginfo is returned here
   *  @ts: upper bound on process time suspension
   */
  static int do_sigtimedwait(const sigset_t *which, kernel_siginfo_t *info,
  		    const struct timespec64 *ts)
  {
  	ktime_t *to = NULL, timeout = KTIME_MAX;
  	struct task_struct *tsk = current;
  	sigset_t mask = *which;
  	int sig, ret = 0;
  
  	if (ts) {
  		if (!timespec64_valid(ts))
  			return -EINVAL;
  		timeout = timespec64_to_ktime(*ts);
  		to = &timeout;
  	}
  
  	/*
  	 * Invert the set of allowed signals to get those we want to block.
  	 */
  	sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
  	signotset(&mask);
  
  	spin_lock_irq(&tsk->sighand->siglock);
  	sig = dequeue_signal(tsk, &mask, info);
  	if (!sig && timeout) {
  		/*
  		 * None ready, temporarily unblock those we're interested
  		 * while we are sleeping in so that we'll be awakened when
  		 * they arrive. Unblocking is always fine, we can avoid
  		 * set_current_blocked().
  		 */
  		tsk->real_blocked = tsk->blocked;
  		sigandsets(&tsk->blocked, &tsk->blocked, &mask);
  		recalc_sigpending();
  		spin_unlock_irq(&tsk->sighand->siglock);
  
  		__set_current_state(TASK_INTERRUPTIBLE);
  		ret = freezable_schedule_hrtimeout_range(to, tsk->timer_slack_ns,
  							 HRTIMER_MODE_REL);
  		spin_lock_irq(&tsk->sighand->siglock);
  		__set_task_blocked(tsk, &tsk->real_blocked);
  		sigemptyset(&tsk->real_blocked);
  		sig = dequeue_signal(tsk, &mask, info);
  	}
  	spin_unlock_irq(&tsk->sighand->siglock);
  
  	if (sig)
  		return sig;
  	return ret ? -EINTR : -EAGAIN;
  }
  
  /**
   *  sys_rt_sigtimedwait - synchronously wait for queued signals specified
   *			in @uthese
   *  @uthese: queued signals to wait for
   *  @uinfo: if non-null, the signal's siginfo is returned here
   *  @uts: upper bound on process time suspension
   *  @sigsetsize: size of sigset_t type
   */
  SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
  		siginfo_t __user *, uinfo,
  		const struct __kernel_timespec __user *, uts,
  		size_t, sigsetsize)
  {
  	sigset_t these;
  	struct timespec64 ts;
  	kernel_siginfo_t info;
  	int ret;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (copy_from_user(&these, uthese, sizeof(these)))
  		return -EFAULT;
  
  	if (uts) {
  		if (get_timespec64(&ts, uts))
  			return -EFAULT;
  	}
  
  	ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
  
  	if (ret > 0 && uinfo) {
  		if (copy_siginfo_to_user(uinfo, &info))
  			ret = -EFAULT;
  	}
  
  	return ret;
  }
  
  #ifdef CONFIG_COMPAT_32BIT_TIME
  SYSCALL_DEFINE4(rt_sigtimedwait_time32, const sigset_t __user *, uthese,
  		siginfo_t __user *, uinfo,
  		const struct old_timespec32 __user *, uts,
  		size_t, sigsetsize)
  {
  	sigset_t these;
  	struct timespec64 ts;
  	kernel_siginfo_t info;
  	int ret;
  
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (copy_from_user(&these, uthese, sizeof(these)))
  		return -EFAULT;
  
  	if (uts) {
  		if (get_old_timespec32(&ts, uts))
  			return -EFAULT;
  	}
  
  	ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
  
  	if (ret > 0 && uinfo) {
  		if (copy_siginfo_to_user(uinfo, &info))
  			ret = -EFAULT;
  	}
  
  	return ret;
  }
  #endif
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(rt_sigtimedwait_time64, compat_sigset_t __user *, uthese,
  		struct compat_siginfo __user *, uinfo,
  		struct __kernel_timespec __user *, uts, compat_size_t, sigsetsize)
  {
  	sigset_t s;
  	struct timespec64 t;
  	kernel_siginfo_t info;
  	long ret;
  
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (get_compat_sigset(&s, uthese))
  		return -EFAULT;
  
  	if (uts) {
  		if (get_timespec64(&t, uts))
  			return -EFAULT;
  	}
  
  	ret = do_sigtimedwait(&s, &info, uts ? &t : NULL);
  
  	if (ret > 0 && uinfo) {
  		if (copy_siginfo_to_user32(uinfo, &info))
  			ret = -EFAULT;
  	}
  
  	return ret;
  }
  
  #ifdef CONFIG_COMPAT_32BIT_TIME
  COMPAT_SYSCALL_DEFINE4(rt_sigtimedwait_time32, compat_sigset_t __user *, uthese,
  		struct compat_siginfo __user *, uinfo,
  		struct old_timespec32 __user *, uts, compat_size_t, sigsetsize)
  {
  	sigset_t s;
  	struct timespec64 t;
  	kernel_siginfo_t info;
  	long ret;
  
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (get_compat_sigset(&s, uthese))
  		return -EFAULT;
  
  	if (uts) {
  		if (get_old_timespec32(&t, uts))
  			return -EFAULT;
  	}
  
  	ret = do_sigtimedwait(&s, &info, uts ? &t : NULL);
  
  	if (ret > 0 && uinfo) {
  		if (copy_siginfo_to_user32(uinfo, &info))
  			ret = -EFAULT;
  	}
  
  	return ret;
  }
  #endif
  #endif
  
  static inline void prepare_kill_siginfo(int sig, struct kernel_siginfo *info)
  {
  	clear_siginfo(info);
  	info->si_signo = sig;
  	info->si_errno = 0;
  	info->si_code = SI_USER;
  	info->si_pid = task_tgid_vnr(current);
  	info->si_uid = from_kuid_munged(current_user_ns(), current_uid());
  }
  
  /**
   *  sys_kill - send a signal to a process
   *  @pid: the PID of the process
   *  @sig: signal to be sent
   */
  SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
  {
  	struct kernel_siginfo info;
  
  	prepare_kill_siginfo(sig, &info);
  
  	return kill_something_info(sig, &info, pid);
  }
  
  #ifdef CONFIG_PROC_FS
  /*
   * Verify that the signaler and signalee either are in the same pid namespace
   * or that the signaler's pid namespace is an ancestor of the signalee's pid
   * namespace.
   */
  static bool access_pidfd_pidns(struct pid *pid)
  {
  	struct pid_namespace *active = task_active_pid_ns(current);
  	struct pid_namespace *p = ns_of_pid(pid);
  
  	for (;;) {
  		if (!p)
  			return false;
  		if (p == active)
  			break;
  		p = p->parent;
  	}
  
  	return true;
  }
  
  static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, siginfo_t *info)
  {
  #ifdef CONFIG_COMPAT
  	/*
  	 * Avoid hooking up compat syscalls and instead handle necessary
  	 * conversions here. Note, this is a stop-gap measure and should not be
  	 * considered a generic solution.
  	 */
  	if (in_compat_syscall())
  		return copy_siginfo_from_user32(
  			kinfo, (struct compat_siginfo __user *)info);
  #endif
  	return copy_siginfo_from_user(kinfo, info);
  }
  
  /**
   * sys_pidfd_send_signal - send a signal to a process through a task file
   *                          descriptor
   * @pidfd:  the file descriptor of the process
   * @sig:    signal to be sent
   * @info:   the signal info
   * @flags:  future flags to be passed
   *
   * The syscall currently only signals via PIDTYPE_PID which covers
   * kill(<positive-pid>, <signal>. It does not signal threads or process
   * groups.
   * In order to extend the syscall to threads and process groups the @flags
   * argument should be used. In essence, the @flags argument will determine
   * what is signaled and not the file descriptor itself. Put in other words,
   * grouping is a property of the flags argument not a property of the file
   * descriptor.
   *
   * Return: 0 on success, negative errno on failure
   */
  SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
  		siginfo_t __user *, info, unsigned int, flags)
  {
  	int ret;
  	struct fd f;
  	struct pid *pid;
  	kernel_siginfo_t kinfo;
  
  	/* Enforce flags be set to 0 until we add an extension. */
  	if (flags)
  		return -EINVAL;
  
  	f = fdget_raw(pidfd);
  	if (!f.file)
  		return -EBADF;
  
  	/* Is this a pidfd? */
  	pid = tgid_pidfd_to_pid(f.file);
  	if (IS_ERR(pid)) {
  		ret = PTR_ERR(pid);
  		goto err;
  	}
  
  	ret = -EINVAL;
  	if (!access_pidfd_pidns(pid))
  		goto err;
  
  	if (info) {
  		ret = copy_siginfo_from_user_any(&kinfo, info);
  		if (unlikely(ret))
  			goto err;
  
  		ret = -EINVAL;
  		if (unlikely(sig != kinfo.si_signo))
  			goto err;
  
  		if ((task_pid(current) != pid) &&
  		    (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)) {
  			/* Only allow sending arbitrary signals to yourself. */
  			ret = -EPERM;
  			if (kinfo.si_code != SI_USER)
  				goto err;
  
  			/* Turn this into a regular kill signal. */
  			prepare_kill_siginfo(sig, &kinfo);
  		}
  	} else {
  		prepare_kill_siginfo(sig, &kinfo);
  	}
  
  	ret = kill_pid_info(sig, &kinfo, pid);
  
  err:
  	fdput(f);
  	return ret;
  }
  #endif /* CONFIG_PROC_FS */
  
  static int
  do_send_specific(pid_t tgid, pid_t pid, int sig, struct kernel_siginfo *info)
  {
  	struct task_struct *p;
  	int error = -ESRCH;
  
  	rcu_read_lock();
  	p = find_task_by_vpid(pid);
  	if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
  		error = check_kill_permission(sig, info, p);
  		/*
  		 * The null signal is a permissions and process existence
  		 * probe.  No signal is actually delivered.
  		 */
  		if (!error && sig) {
  			error = do_send_sig_info(sig, info, p, PIDTYPE_PID);
  			/*
  			 * If lock_task_sighand() failed we pretend the task
  			 * dies after receiving the signal. The window is tiny,
  			 * and the signal is private anyway.
  			 */
  			if (unlikely(error == -ESRCH))
  				error = 0;
  		}
  	}
  	rcu_read_unlock();
  
  	return error;
  }
  
  static int do_tkill(pid_t tgid, pid_t pid, int sig)
  {
  	struct kernel_siginfo info;
  
  	clear_siginfo(&info);
  	info.si_signo = sig;
  	info.si_errno = 0;
  	info.si_code = SI_TKILL;
  	info.si_pid = task_tgid_vnr(current);
  	info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
  
  	return do_send_specific(tgid, pid, sig, &info);
  }
  
  /**
   *  sys_tgkill - send signal to one specific thread
   *  @tgid: the thread group ID of the thread
   *  @pid: the PID of the thread
   *  @sig: signal to be sent
   *
   *  This syscall also checks the @tgid and returns -ESRCH even if the PID
   *  exists but it's not belonging to the target process anymore. This
   *  method solves the problem of threads exiting and PIDs getting reused.
   */
  SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
  {
  	/* This is only valid for single tasks */
  	if (pid <= 0 || tgid <= 0)
  		return -EINVAL;
  
  	return do_tkill(tgid, pid, sig);
  }
  
  /**
   *  sys_tkill - send signal to one specific task
   *  @pid: the PID of the task
   *  @sig: signal to be sent
   *
   *  Send a signal to only one task, even if it's a CLONE_THREAD task.
   */
  SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
  {
  	/* This is only valid for single tasks */
  	if (pid <= 0)
  		return -EINVAL;
  
  	return do_tkill(0, pid, sig);
  }
  
  static int do_rt_sigqueueinfo(pid_t pid, int sig, kernel_siginfo_t *info)
  {
  	/* Not even root can pretend to send signals from the kernel.
  	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
  	 */
  	if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
  	    (task_pid_vnr(current) != pid))
  		return -EPERM;
  
  	/* POSIX.1b doesn't mention process groups.  */
  	return kill_proc_info(sig, info, pid);
  }
  
  /**
   *  sys_rt_sigqueueinfo - send signal information to a signal
   *  @pid: the PID of the thread
   *  @sig: signal to be sent
   *  @uinfo: signal info to be sent
   */
  SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
  		siginfo_t __user *, uinfo)
  {
  	kernel_siginfo_t info;
  	int ret = __copy_siginfo_from_user(sig, &info, uinfo);
  	if (unlikely(ret))
  		return ret;
  	return do_rt_sigqueueinfo(pid, sig, &info);
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
  			compat_pid_t, pid,
  			int, sig,
  			struct compat_siginfo __user *, uinfo)
  {
  	kernel_siginfo_t info;
  	int ret = __copy_siginfo_from_user32(sig, &info, uinfo);
  	if (unlikely(ret))
  		return ret;
  	return do_rt_sigqueueinfo(pid, sig, &info);
  }
  #endif
  
  static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, kernel_siginfo_t *info)
  {
  	/* This is only valid for single tasks */
  	if (pid <= 0 || tgid <= 0)
  		return -EINVAL;
  
  	/* Not even root can pretend to send signals from the kernel.
  	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
  	 */
  	if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
  	    (task_pid_vnr(current) != pid))
  		return -EPERM;
  
  	return do_send_specific(tgid, pid, sig, info);
  }
  
  SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
  		siginfo_t __user *, uinfo)
  {
  	kernel_siginfo_t info;
  	int ret = __copy_siginfo_from_user(sig, &info, uinfo);
  	if (unlikely(ret))
  		return ret;
  	return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
  			compat_pid_t, tgid,
  			compat_pid_t, pid,
  			int, sig,
  			struct compat_siginfo __user *, uinfo)
  {
  	kernel_siginfo_t info;
  	int ret = __copy_siginfo_from_user32(sig, &info, uinfo);
  	if (unlikely(ret))
  		return ret;
  	return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
  }
  #endif
  
  /*
   * For kthreads only, must not be used if cloned with CLONE_SIGHAND
   */
  void kernel_sigaction(int sig, __sighandler_t action)
  {
  	spin_lock_irq(&current->sighand->siglock);
  	current->sighand->action[sig - 1].sa.sa_handler = action;
  	if (action == SIG_IGN) {
  		sigset_t mask;
  
  		sigemptyset(&mask);
  		sigaddset(&mask, sig);
  
  		flush_sigqueue_mask(&mask, &current->signal->shared_pending);
  		flush_sigqueue_mask(&mask, &current->pending);
  		recalc_sigpending();
  	}
  	spin_unlock_irq(&current->sighand->siglock);
  }
  EXPORT_SYMBOL(kernel_sigaction);
  
  void __weak sigaction_compat_abi(struct k_sigaction *act,
  		struct k_sigaction *oact)
  {
  }
  
  int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
  {
  	struct task_struct *p = current, *t;
  	struct k_sigaction *k;
  	sigset_t mask;
  
  	if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
  		return -EINVAL;
  
  	k = &p->sighand->action[sig-1];
  
  	spin_lock_irq(&p->sighand->siglock);
  	if (oact)
  		*oact = *k;
  
  	sigaction_compat_abi(act, oact);
  
  	if (act) {
  		sigdelsetmask(&act->sa.sa_mask,
  			      sigmask(SIGKILL) | sigmask(SIGSTOP));
  		*k = *act;
  		/*
  		 * POSIX 3.3.1.3:
  		 *  "Setting a signal action to SIG_IGN for a signal that is
  		 *   pending shall cause the pending signal to be discarded,
  		 *   whether or not it is blocked."
  		 *
  		 *  "Setting a signal action to SIG_DFL for a signal that is
  		 *   pending and whose default action is to ignore the signal
  		 *   (for example, SIGCHLD), shall cause the pending signal to
  		 *   be discarded, whether or not it is blocked"
  		 */
  		if (sig_handler_ignored(sig_handler(p, sig), sig)) {
  			sigemptyset(&mask);
  			sigaddset(&mask, sig);
  			flush_sigqueue_mask(&mask, &p->signal->shared_pending);
  			for_each_thread(p, t)
  				flush_sigqueue_mask(&mask, &t->pending);
  		}
  	}
  
  	spin_unlock_irq(&p->sighand->siglock);
  	return 0;
  }
  
  static int
  do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp,
  		size_t min_ss_size)
  {
  	struct task_struct *t = current;
  
  	if (oss) {
  		memset(oss, 0, sizeof(stack_t));
  		oss->ss_sp = (void __user *) t->sas_ss_sp;
  		oss->ss_size = t->sas_ss_size;
  		oss->ss_flags = sas_ss_flags(sp) |
  			(current->sas_ss_flags & SS_FLAG_BITS);
  	}
  
  	if (ss) {
  		void __user *ss_sp = ss->ss_sp;
  		size_t ss_size = ss->ss_size;
  		unsigned ss_flags = ss->ss_flags;
  		int ss_mode;
  
  		if (unlikely(on_sig_stack(sp)))
  			return -EPERM;
  
  		ss_mode = ss_flags & ~SS_FLAG_BITS;
  		if (unlikely(ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
  				ss_mode != 0))
  			return -EINVAL;
  
  		if (ss_mode == SS_DISABLE) {
  			ss_size = 0;
  			ss_sp = NULL;
  		} else {
  			if (unlikely(ss_size < min_ss_size))
  				return -ENOMEM;
  		}
  
  		t->sas_ss_sp = (unsigned long) ss_sp;
  		t->sas_ss_size = ss_size;
  		t->sas_ss_flags = ss_flags;
  	}
  	return 0;
  }
  
  SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)
  {
  	stack_t new, old;
  	int err;
  	if (uss && copy_from_user(&new, uss, sizeof(stack_t)))
  		return -EFAULT;
  	err = do_sigaltstack(uss ? &new : NULL, uoss ? &old : NULL,
  			      current_user_stack_pointer(),
  			      MINSIGSTKSZ);
  	if (!err && uoss && copy_to_user(uoss, &old, sizeof(stack_t)))
  		err = -EFAULT;
  	return err;
  }
  
  int restore_altstack(const stack_t __user *uss)
  {
  	stack_t new;
  	if (copy_from_user(&new, uss, sizeof(stack_t)))
  		return -EFAULT;
  	(void)do_sigaltstack(&new, NULL, current_user_stack_pointer(),
  			     MINSIGSTKSZ);
  	/* squash all but EFAULT for now */
  	return 0;
  }
  
  int __save_altstack(stack_t __user *uss, unsigned long sp)
  {
  	struct task_struct *t = current;
  	int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
  		__put_user(t->sas_ss_flags, &uss->ss_flags) |
  		__put_user(t->sas_ss_size, &uss->ss_size);
  	if (err)
  		return err;
  	if (t->sas_ss_flags & SS_AUTODISARM)
  		sas_ss_reset(t);
  	return 0;
  }
  
  #ifdef CONFIG_COMPAT
  static int do_compat_sigaltstack(const compat_stack_t __user *uss_ptr,
  				 compat_stack_t __user *uoss_ptr)
  {
  	stack_t uss, uoss;
  	int ret;
  
  	if (uss_ptr) {
  		compat_stack_t uss32;
  		if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
  			return -EFAULT;
  		uss.ss_sp = compat_ptr(uss32.ss_sp);
  		uss.ss_flags = uss32.ss_flags;
  		uss.ss_size = uss32.ss_size;
  	}
  	ret = do_sigaltstack(uss_ptr ? &uss : NULL, &uoss,
  			     compat_user_stack_pointer(),
  			     COMPAT_MINSIGSTKSZ);
  	if (ret >= 0 && uoss_ptr)  {
  		compat_stack_t old;
  		memset(&old, 0, sizeof(old));
  		old.ss_sp = ptr_to_compat(uoss.ss_sp);
  		old.ss_flags = uoss.ss_flags;
  		old.ss_size = uoss.ss_size;
  		if (copy_to_user(uoss_ptr, &old, sizeof(compat_stack_t)))
  			ret = -EFAULT;
  	}
  	return ret;
  }
  
  COMPAT_SYSCALL_DEFINE2(sigaltstack,
  			const compat_stack_t __user *, uss_ptr,
  			compat_stack_t __user *, uoss_ptr)
  {
  	return do_compat_sigaltstack(uss_ptr, uoss_ptr);
  }
  
  int compat_restore_altstack(const compat_stack_t __user *uss)
  {
  	int err = do_compat_sigaltstack(uss, NULL);
  	/* squash all but -EFAULT for now */
  	return err == -EFAULT ? err : 0;
  }
  
  int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
  {
  	int err;
  	struct task_struct *t = current;
  	err = __put_user(ptr_to_compat((void __user *)t->sas_ss_sp),
  			 &uss->ss_sp) |
  		__put_user(t->sas_ss_flags, &uss->ss_flags) |
  		__put_user(t->sas_ss_size, &uss->ss_size);
  	if (err)
  		return err;
  	if (t->sas_ss_flags & SS_AUTODISARM)
  		sas_ss_reset(t);
  	return 0;
  }
  #endif
  
  #ifdef __ARCH_WANT_SYS_SIGPENDING
  
  /**
   *  sys_sigpending - examine pending signals
   *  @uset: where mask of pending signal is returned
   */
  SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, uset)
  {
  	sigset_t set;
  
  	if (sizeof(old_sigset_t) > sizeof(*uset))
  		return -EINVAL;
  
  	do_sigpending(&set);
  
  	if (copy_to_user(uset, &set, sizeof(old_sigset_t)))
  		return -EFAULT;
  
  	return 0;
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE1(sigpending, compat_old_sigset_t __user *, set32)
  {
  	sigset_t set;
  
  	do_sigpending(&set);
  
  	return put_user(set.sig[0], set32);
  }
  #endif
  
  #endif
  
  #ifdef __ARCH_WANT_SYS_SIGPROCMASK
  /**
   *  sys_sigprocmask - examine and change blocked signals
   *  @how: whether to add, remove, or set signals
   *  @nset: signals to add or remove (if non-null)
   *  @oset: previous value of signal mask if non-null
   *
   * Some platforms have their own version with special arguments;
   * others support only sys_rt_sigprocmask.
   */
  
  SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
  		old_sigset_t __user *, oset)
  {
  	old_sigset_t old_set, new_set;
  	sigset_t new_blocked;
  
  	old_set = current->blocked.sig[0];
  
  	if (nset) {
  		if (copy_from_user(&new_set, nset, sizeof(*nset)))
  			return -EFAULT;
  
  		new_blocked = current->blocked;
  
  		switch (how) {
  		case SIG_BLOCK:
  			sigaddsetmask(&new_blocked, new_set);
  			break;
  		case SIG_UNBLOCK:
  			sigdelsetmask(&new_blocked, new_set);
  			break;
  		case SIG_SETMASK:
  			new_blocked.sig[0] = new_set;
  			break;
  		default:
  			return -EINVAL;
  		}
  
  		set_current_blocked(&new_blocked);
  	}
  
  	if (oset) {
  		if (copy_to_user(oset, &old_set, sizeof(*oset)))
  			return -EFAULT;
  	}
  
  	return 0;
  }
  #endif /* __ARCH_WANT_SYS_SIGPROCMASK */
  
  #ifndef CONFIG_ODD_RT_SIGACTION
  /**
   *  sys_rt_sigaction - alter an action taken by a process
   *  @sig: signal to be sent
   *  @act: new sigaction
   *  @oact: used to save the previous sigaction
   *  @sigsetsize: size of sigset_t type
   */
  SYSCALL_DEFINE4(rt_sigaction, int, sig,
  		const struct sigaction __user *, act,
  		struct sigaction __user *, oact,
  		size_t, sigsetsize)
  {
  	struct k_sigaction new_sa, old_sa;
  	int ret;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (act && copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
  		return -EFAULT;
  
  	ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
  	if (ret)
  		return ret;
  
  	if (oact && copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
  		return -EFAULT;
  
  	return 0;
  }
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
  		const struct compat_sigaction __user *, act,
  		struct compat_sigaction __user *, oact,
  		compat_size_t, sigsetsize)
  {
  	struct k_sigaction new_ka, old_ka;
  #ifdef __ARCH_HAS_SA_RESTORER
  	compat_uptr_t restorer;
  #endif
  	int ret;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(compat_sigset_t))
  		return -EINVAL;
  
  	if (act) {
  		compat_uptr_t handler;
  		ret = get_user(handler, &act->sa_handler);
  		new_ka.sa.sa_handler = compat_ptr(handler);
  #ifdef __ARCH_HAS_SA_RESTORER
  		ret |= get_user(restorer, &act->sa_restorer);
  		new_ka.sa.sa_restorer = compat_ptr(restorer);
  #endif
  		ret |= get_compat_sigset(&new_ka.sa.sa_mask, &act->sa_mask);
  		ret |= get_user(new_ka.sa.sa_flags, &act->sa_flags);
  		if (ret)
  			return -EFAULT;
  	}
  
  	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
  	if (!ret && oact) {
  		ret = put_user(ptr_to_compat(old_ka.sa.sa_handler), 
  			       &oact->sa_handler);
  		ret |= put_compat_sigset(&oact->sa_mask, &old_ka.sa.sa_mask,
  					 sizeof(oact->sa_mask));
  		ret |= put_user(old_ka.sa.sa_flags, &oact->sa_flags);
  #ifdef __ARCH_HAS_SA_RESTORER
  		ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer),
  				&oact->sa_restorer);
  #endif
  	}
  	return ret;
  }
  #endif
  #endif /* !CONFIG_ODD_RT_SIGACTION */
  
  #ifdef CONFIG_OLD_SIGACTION
  SYSCALL_DEFINE3(sigaction, int, sig,
  		const struct old_sigaction __user *, act,
  	        struct old_sigaction __user *, oact)
  {
  	struct k_sigaction new_ka, old_ka;
  	int ret;
  
  	if (act) {
  		old_sigset_t mask;
  		if (!access_ok(act, sizeof(*act)) ||
  		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
  		    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
  		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
  		    __get_user(mask, &act->sa_mask))
  			return -EFAULT;
  #ifdef __ARCH_HAS_KA_RESTORER
  		new_ka.ka_restorer = NULL;
  #endif
  		siginitset(&new_ka.sa.sa_mask, mask);
  	}
  
  	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
  
  	if (!ret && oact) {
  		if (!access_ok(oact, sizeof(*oact)) ||
  		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
  		    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
  		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
  		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
  			return -EFAULT;
  	}
  
  	return ret;
  }
  #endif
  #ifdef CONFIG_COMPAT_OLD_SIGACTION
  COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
  		const struct compat_old_sigaction __user *, act,
  	        struct compat_old_sigaction __user *, oact)
  {
  	struct k_sigaction new_ka, old_ka;
  	int ret;
  	compat_old_sigset_t mask;
  	compat_uptr_t handler, restorer;
  
  	if (act) {
  		if (!access_ok(act, sizeof(*act)) ||
  		    __get_user(handler, &act->sa_handler) ||
  		    __get_user(restorer, &act->sa_restorer) ||
  		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
  		    __get_user(mask, &act->sa_mask))
  			return -EFAULT;
  
  #ifdef __ARCH_HAS_KA_RESTORER
  		new_ka.ka_restorer = NULL;
  #endif
  		new_ka.sa.sa_handler = compat_ptr(handler);
  		new_ka.sa.sa_restorer = compat_ptr(restorer);
  		siginitset(&new_ka.sa.sa_mask, mask);
  	}
  
  	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
  
  	if (!ret && oact) {
  		if (!access_ok(oact, sizeof(*oact)) ||
  		    __put_user(ptr_to_compat(old_ka.sa.sa_handler),
  			       &oact->sa_handler) ||
  		    __put_user(ptr_to_compat(old_ka.sa.sa_restorer),
  			       &oact->sa_restorer) ||
  		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
  		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
  			return -EFAULT;
  	}
  	return ret;
  }
  #endif
  
  #ifdef CONFIG_SGETMASK_SYSCALL
  
  /*
   * For backwards compatibility.  Functionality superseded by sigprocmask.
   */
  SYSCALL_DEFINE0(sgetmask)
  {
  	/* SMP safe */
  	return current->blocked.sig[0];
  }
  
  SYSCALL_DEFINE1(ssetmask, int, newmask)
  {
  	int old = current->blocked.sig[0];
  	sigset_t newset;
  
  	siginitset(&newset, newmask);
  	set_current_blocked(&newset);
  
  	return old;
  }
  #endif /* CONFIG_SGETMASK_SYSCALL */
  
  #ifdef __ARCH_WANT_SYS_SIGNAL
  /*
   * For backwards compatibility.  Functionality superseded by sigaction.
   */
  SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
  {
  	struct k_sigaction new_sa, old_sa;
  	int ret;
  
  	new_sa.sa.sa_handler = handler;
  	new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
  	sigemptyset(&new_sa.sa.sa_mask);
  
  	ret = do_sigaction(sig, &new_sa, &old_sa);
  
  	return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
  }
  #endif /* __ARCH_WANT_SYS_SIGNAL */
  
  #ifdef __ARCH_WANT_SYS_PAUSE
  
  SYSCALL_DEFINE0(pause)
  {
  	while (!signal_pending(current)) {
  		__set_current_state(TASK_INTERRUPTIBLE);
  		schedule();
  	}
  	return -ERESTARTNOHAND;
  }
  
  #endif
  
  static int sigsuspend(sigset_t *set)
  {
  	current->saved_sigmask = current->blocked;
  	set_current_blocked(set);
  
  	while (!signal_pending(current)) {
  		__set_current_state(TASK_INTERRUPTIBLE);
  		schedule();
  	}
  	set_restore_sigmask();
  	return -ERESTARTNOHAND;
  }
  
  /**
   *  sys_rt_sigsuspend - replace the signal mask for a value with the
   *	@unewset value until a signal is received
   *  @unewset: new signal mask value
   *  @sigsetsize: size of sigset_t type
   */
  SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
  {
  	sigset_t newset;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (copy_from_user(&newset, unewset, sizeof(newset)))
  		return -EFAULT;
  	return sigsuspend(&newset);
  }
   
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE2(rt_sigsuspend, compat_sigset_t __user *, unewset, compat_size_t, sigsetsize)
  {
  	sigset_t newset;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (get_compat_sigset(&newset, unewset))
  		return -EFAULT;
  	return sigsuspend(&newset);
  }
  #endif
  
  #ifdef CONFIG_OLD_SIGSUSPEND
  SYSCALL_DEFINE1(sigsuspend, old_sigset_t, mask)
  {
  	sigset_t blocked;
  	siginitset(&blocked, mask);
  	return sigsuspend(&blocked);
  }
  #endif
  #ifdef CONFIG_OLD_SIGSUSPEND3
  SYSCALL_DEFINE3(sigsuspend, int, unused1, int, unused2, old_sigset_t, mask)
  {
  	sigset_t blocked;
  	siginitset(&blocked, mask);
  	return sigsuspend(&blocked);
  }
  #endif
  
  __weak const char *arch_vma_name(struct vm_area_struct *vma)
  {
  	return NULL;
  }
  
  static inline void siginfo_buildtime_checks(void)
  {
  	BUILD_BUG_ON(sizeof(struct siginfo) != SI_MAX_SIZE);
  
  	/* Verify the offsets in the two siginfos match */
  #define CHECK_OFFSET(field) \
  	BUILD_BUG_ON(offsetof(siginfo_t, field) != offsetof(kernel_siginfo_t, field))
  
  	/* kill */
  	CHECK_OFFSET(si_pid);
  	CHECK_OFFSET(si_uid);
  
  	/* timer */
  	CHECK_OFFSET(si_tid);
  	CHECK_OFFSET(si_overrun);
  	CHECK_OFFSET(si_value);
  
  	/* rt */
  	CHECK_OFFSET(si_pid);
  	CHECK_OFFSET(si_uid);
  	CHECK_OFFSET(si_value);
  
  	/* sigchld */
  	CHECK_OFFSET(si_pid);
  	CHECK_OFFSET(si_uid);
  	CHECK_OFFSET(si_status);
  	CHECK_OFFSET(si_utime);
  	CHECK_OFFSET(si_stime);
  
  	/* sigfault */
  	CHECK_OFFSET(si_addr);
  	CHECK_OFFSET(si_addr_lsb);
  	CHECK_OFFSET(si_lower);
  	CHECK_OFFSET(si_upper);
  	CHECK_OFFSET(si_pkey);
  
  	/* sigpoll */
  	CHECK_OFFSET(si_band);
  	CHECK_OFFSET(si_fd);
  
  	/* sigsys */
  	CHECK_OFFSET(si_call_addr);
  	CHECK_OFFSET(si_syscall);
  	CHECK_OFFSET(si_arch);
  #undef CHECK_OFFSET
  }
  
  void __init signals_init(void)
  {
  	siginfo_buildtime_checks();
  
  	sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
  }
  
  #ifdef CONFIG_KGDB_KDB
  #include <linux/kdb.h>
  /*
   * kdb_send_sig - Allows kdb to send signals without exposing
   * signal internals.  This function checks if the required locks are
   * available before calling the main signal code, to avoid kdb
   * deadlocks.
   */
  void kdb_send_sig(struct task_struct *t, int sig)
  {
  	static struct task_struct *kdb_prev_t;
  	int new_t, ret;
  	if (!spin_trylock(&t->sighand->siglock)) {
  		kdb_printf("Can't do kill command now.\n"
  			   "The sigmask lock is held somewhere else in "
  			   "kernel, try again later\n");
  		return;
  	}
  	new_t = kdb_prev_t != t;
  	kdb_prev_t = t;
  	if (t->state != TASK_RUNNING && new_t) {
  		spin_unlock(&t->sighand->siglock);
  		kdb_printf("Process is not RUNNING, sending a signal from "
  			   "kdb risks deadlock\n"
  			   "on the run queue locks. "
  			   "The signal has _not_ been sent.\n"
  			   "Reissue the kill command if you want to risk "
  			   "the deadlock.\n");
  		return;
  	}
  	ret = send_signal(sig, SEND_SIG_PRIV, t, PIDTYPE_PID);
  	spin_unlock(&t->sighand->siglock);
  	if (ret)
  		kdb_printf("Fail to deliver Signal %d to process %d.\n",
  			   sig, t->pid);
  	else
  		kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
  }
  #endif	/* CONFIG_KGDB_KDB */
  