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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  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/task_work.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/cgroup.h>
 #include <linux/audit.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 <asm/syscall.h>    /* for syscall_get_* */
 
 /*
  * 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;
 
     /* Only allow kernel generated signals to this kthread */
     if (unlikely((t->flags & PF_KTHREAD) &&
              (handler == SIG_KTHREAD_KERNEL) && !force))
         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 | JOBCTL_TRAP_FREEZE)) ||
         PENDING(&t->pending, &t->blocked) ||
         PENDING(&t->signal->shared_pending, &t->blocked) ||
         cgroup_task_frozen(t)) {
         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))
         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)
 {
     unsigned long mask = current->jobctl & JOBCTL_STOP_SIGMASK;
     struct signal_struct *sig = current->signal;
 
     if (sig->group_stop_count) {
         sig->group_stop_count++;
         mask |= JOBCTL_STOP_CONSUME;
     } else if (!(sig->flags & SIGNAL_STOP_STOPPED))
         return;
 
     /* Have the new thread join an on-going signal group stop */
     task_set_jobctl_pending(task, mask | JOBCTL_STOP_PENDING);
 }
 
 /*
  * 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 gfp_flags,
          int override_rlimit, const unsigned int sigqueue_flags)
 {
     struct sigqueue *q = NULL;
     struct ucounts *ucounts = NULL;
     long sigpending;
 
     /*
      * Protect access to @t credentials. This can go away when all
      * callers hold rcu read lock.
      *
      * NOTE! A pending signal will hold on to the user refcount,
      * and we get/put the refcount only when the sigpending count
      * changes from/to zero.
      */
     rcu_read_lock();
     ucounts = task_ucounts(t);
     sigpending = inc_rlimit_get_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);
     rcu_read_unlock();
     if (!sigpending)
         return NULL;
 
     if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
         q = kmem_cache_alloc(sigqueue_cachep, gfp_flags);
     } else {
         print_dropped_signal(sig);
     }
 
     if (unlikely(q == NULL)) {
         dec_rlimit_put_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);
     } else {
         INIT_LIST_HEAD(&q->list);
         q->flags = sigqueue_flags;
         q->ucounts = ucounts;
     }
     return q;
 }
 
 static void __sigqueue_free(struct sigqueue *q)
 {
     if (q->flags & SIGQUEUE_PREALLOC)
         return;
     if (q->ucounts) {
         dec_rlimit_put_ucounts(q->ucounts, UCOUNT_RLIMIT_SIGPENDING);
         q->ucounts = NULL;
     }
     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, enum pid_type *type)
 {
     bool resched_timer = false;
     int signr;
 
     /* We only dequeue private signals from ourselves, we don't let
      * signalfd steal them
      */
     *type = PIDTYPE_PID;
     signr = __dequeue_signal(&tsk->pending, mask, info, &resched_timer);
     if (!signr) {
         *type = PIDTYPE_TGID;
         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 positive 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)
 {
     lockdep_assert_held(&t->sighand->siglock);
 
     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;
             fallthrough;
         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));
     lockdep_assert_held(&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) {
         if (signal->core_state)
             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))) {
                 t->jobctl &= ~JOBCTL_STOPPED;
                 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) || !task_sigpending(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->core_state || !(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);
 }
 
 static int __send_signal_locked(int sig, struct kernel_siginfo *info,
                 struct task_struct *t, enum pid_type type, bool force)
 {
     struct sigpending *pending;
     struct sigqueue *q;
     int override_rlimit;
     int ret = 0, result;
 
     lockdep_assert_held(&t->sighand->siglock);
 
     result = TRACE_SIGNAL_IGNORED;
     if (!prepare_signal(sig, t, force))
         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, 0);
 
     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));
             rcu_read_lock();
             q->info.si_uid =
                 from_kuid_munged(task_cred_xxx(t, user_ns),
                          current_uid());
             rcu_read_unlock();
             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);
             break;
         }
     } else if (!is_si_special(info) &&
            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 inline bool has_si_pid_and_uid(struct kernel_siginfo *info)
 {
     bool ret = false;
     switch (siginfo_layout(info->si_signo, info->si_code)) {
     case SIL_KILL:
     case SIL_CHLD:
     case SIL_RT:
         ret = true;
         break;
     case SIL_TIMER:
     case SIL_POLL:
     case SIL_FAULT:
     case SIL_FAULT_TRAPNO:
     case SIL_FAULT_MCEERR:
     case SIL_FAULT_BNDERR:
     case SIL_FAULT_PKUERR:
     case SIL_FAULT_PERF_EVENT:
     case SIL_SYS:
         ret = false;
         break;
     }
     return ret;
 }
 
 int send_signal_locked(int sig, struct kernel_siginfo *info,
                struct task_struct *t, enum pid_type type)
 {
     /* Should SIGKILL or SIGSTOP be received by a pid namespace init? */
     bool force = false;
 
     if (info == SEND_SIG_NOINFO) {
         /* Force if sent from an ancestor pid namespace */
         force = !task_pid_nr_ns(current, task_active_pid_ns(t));
     } else if (info == SEND_SIG_PRIV) {
         /* Don't ignore kernel generated signals */
         force = true;
     } else if (has_si_pid_and_uid(info)) {
         /* SIGKILL and SIGSTOP is special or has ids */
         struct user_namespace *t_user_ns;
 
         rcu_read_lock();
         t_user_ns = task_cred_xxx(t, user_ns);
         if (current_user_ns() != t_user_ns) {
             kuid_t uid = make_kuid(current_user_ns(), info->si_uid);
             info->si_uid = from_kuid_munged(t_user_ns, uid);
         }
         rcu_read_unlock();
 
         /* A kernel generated signal? */
         force = (info->si_code == SI_KERNEL);
 
         /* From an ancestor pid namespace? */
         if (!task_pid_nr_ns(current, task_active_pid_ns(t))) {
             info->si_pid = 0;
             force = true;
         }
     }
     return __send_signal_locked(sig, info, t, type, force);
 }
 
 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 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_locked(sig, info, p, type);
         unlock_task_sighand(p, &flags);
     }
 
     return ret;
 }
 
 enum sig_handler {
     HANDLER_CURRENT, /* If reachable use the current handler */
     HANDLER_SIG_DFL, /* Always use SIG_DFL handler semantics */
     HANDLER_EXIT,    /* Only visible as the process exit code */
 };
 
 /*
  * 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.
  */
 static int
 force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t,
     enum sig_handler handler)
 {
     unsigned long int flags;
     int ret, blocked, ignored;
     struct k_sigaction *action;
     int sig = info->si_signo;
 
     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 || (handler != HANDLER_CURRENT)) {
         action->sa.sa_handler = SIG_DFL;
         if (handler == HANDLER_EXIT)
             action->sa.sa_flags |= SA_IMMUTABLE;
         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. But HANDLER_EXIT is always fatal.
      */
     if (action->sa.sa_handler == SIG_DFL &&
         (!t->ptrace || (handler == HANDLER_EXIT)))
         t->signal->flags &= ~SIGNAL_UNKILLABLE;
     ret = send_signal_locked(sig, info, t, PIDTYPE_PID);
     spin_unlock_irqrestore(&t->sighand->siglock, flags);
 
     return ret;
 }
 
 int force_sig_info(struct kernel_siginfo *info)
 {
     return force_sig_info_to_task(info, current, HANDLER_CURRENT);
 }
 
 /*
  * 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 == rcu_access_pointer(tsk->sighand)))
             break;
         spin_unlock_irqrestore(&sighand->siglock, *flags);
     }
     rcu_read_unlock();
 
     return sighand;
 }
 
 #ifdef CONFIG_LOCKDEP
 void lockdep_assert_task_sighand_held(struct task_struct *task)
 {
     struct sighand_struct *sighand;
 
     rcu_read_lock();
     sighand = rcu_dereference(task->sighand);
     if (sighand)
         lockdep_assert_held(&sighand->siglock);
     else
         WARN_ON_ONCE(1);
     rcu_read_unlock();
 }
 #endif
 
 /*
  * 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);
 }
 
 /*
  * The usb asyncio usage of siginfo is wrong.  The glibc support
  * for asyncio which uses SI_ASYNCIO assumes the layout is SIL_RT.
  * AKA after the generic fields:
  *  kernel_pid_t    si_pid;
  *  kernel_uid32_t  si_uid;
  *  sigval_t    si_value;
  *
  * Unfortunately when usb generates SI_ASYNCIO it assumes the layout
  * after the generic fields is:
  *  void __user     *si_addr;
  *
  * This is a practical problem when there is a 64bit big endian kernel
  * and a 32bit userspace.  As the 32bit address will encoded in the low
  * 32bits of the pointer.  Those low 32bits will be stored at higher
  * address than appear in a 32 bit pointer.  So userspace will not
  * see the address it was expecting for it's completions.
  *
  * There is nothing in the encoding that can allow
  * copy_siginfo_to_user32 to detect this confusion of formats, so
  * handle this by requiring the caller of kill_pid_usb_asyncio to
  * notice when this situration takes place and to store the 32bit
  * pointer in sival_int, instead of sival_addr of the sigval_t addr
  * parameter.
  */
 int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr,
              struct pid *pid, const struct cred *cred)
 {
     struct kernel_siginfo info;
     struct task_struct *p;
     unsigned long flags;
     int ret = -EINVAL;
 
     if (!valid_signal(sig))
         return ret;
 
     clear_siginfo(&info);
     info.si_signo = sig;
     info.si_errno = errno;
     info.si_code = SI_ASYNCIO;
     *((sigval_t *)&info.si_pid) = addr;
 
     rcu_read_lock();
     p = pid_task(pid, PIDTYPE_PID);
     if (!p) {
         ret = -ESRCH;
         goto out_unlock;
     }
     if (!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_locked(sig, &info, p, PIDTYPE_TGID, false);
             unlock_task_sighand(p, &flags);
         } else
             ret = -ESRCH;
     }
 out_unlock:
     rcu_read_unlock();
     return ret;
 }
 EXPORT_SYMBOL_GPL(kill_pid_usb_asyncio);
 
 /*
  * 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)
         return kill_proc_info(sig, info, pid);
 
     /* -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 kernel_siginfo info;
 
     clear_siginfo(&info);
     info.si_signo = sig;
     info.si_errno = 0;
     info.si_code = SI_KERNEL;
     info.si_pid = 0;
     info.si_uid = 0;
     force_sig_info(&info);
 }
 EXPORT_SYMBOL(force_sig);
 
 void force_fatal_sig(int sig)
 {
     struct kernel_siginfo info;
 
     clear_siginfo(&info);
     info.si_signo = sig;
     info.si_errno = 0;
     info.si_code = SI_KERNEL;
     info.si_pid = 0;
     info.si_uid = 0;
     force_sig_info_to_task(&info, current, HANDLER_SIG_DFL);
 }
 
 void force_exit_sig(int sig)
 {
     struct kernel_siginfo info;
 
     clear_siginfo(&info);
     info.si_signo = sig;
     info.si_errno = 0;
     info.si_code = SI_KERNEL;
     info.si_pid = 0;
     info.si_uid = 0;
     force_sig_info_to_task(&info, current, HANDLER_EXIT);
 }
 
 /*
  * 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)
 {
     if (sig == SIGSEGV)
         force_fatal_sig(SIGSEGV);
     else
         force_sig(SIGSEGV);
 }
 
 int force_sig_fault_to_task(int sig, int code, void __user *addr
     ___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 __ia64__
     info.si_imm = imm;
     info.si_flags = flags;
     info.si_isr = isr;
 #endif
     return force_sig_info_to_task(&info, t, HANDLER_CURRENT);
 }
 
 int force_sig_fault(int sig, int code, void __user *addr
     ___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr))
 {
     return force_sig_fault_to_task(sig, code, addr
                        ___ARCH_SI_IA64(imm, flags, isr), current);
 }
 
 int send_sig_fault(int sig, int code, void __user *addr
     ___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 __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 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);
 }
 
 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);
 }
 
 #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);
 }
 #endif
 
 int send_sig_perf(void __user *addr, u32 type, u64 sig_data)
 {
     struct kernel_siginfo info;
 
     clear_siginfo(&info);
     info.si_signo     = SIGTRAP;
     info.si_errno     = 0;
     info.si_code      = TRAP_PERF;
     info.si_addr      = addr;
     info.si_perf_data = sig_data;
     info.si_perf_type = type;
 
     /*
      * Signals generated by perf events should not terminate the whole
      * process if SIGTRAP is blocked, however, delivering the signal
      * asynchronously is better than not delivering at all. But tell user
      * space if the signal was asynchronous, so it can clearly be
      * distinguished from normal synchronous ones.
      */
     info.si_perf_flags = sigismember(&current->blocked, info.si_signo) ?
                      TRAP_PERF_FLAG_ASYNC :
                      0;
 
     return send_sig_info(info.si_signo, &info, current);
 }
 
 /**
  * force_sig_seccomp - signals the task to allow in-process syscall emulation
  * @syscall: syscall number to send to userland
  * @reason: filter-supplied reason code to send to userland (via si_errno)
  * @force_coredump: true to trigger a coredump
  *
  * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
  */
 int force_sig_seccomp(int syscall, int reason, bool force_coredump)
 {
     struct kernel_siginfo info;
 
     clear_siginfo(&info);
     info.si_signo = SIGSYS;
     info.si_code = SYS_SECCOMP;
     info.si_call_addr = (void __user *)KSTK_EIP(current);
     info.si_errno = reason;
     info.si_arch = syscall_get_arch(current);
     info.si_syscall = syscall;
     return force_sig_info_to_task(&info, current,
         force_coredump ? HANDLER_EXIT : HANDLER_CURRENT);
 }
 
 /* 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);
 }
 
 /* For the rare architectures that include trap information using
  * si_trapno.
  */
 int force_sig_fault_trapno(int sig, int code, void __user *addr, int trapno)
 {
     struct kernel_siginfo info;
 
     clear_siginfo(&info);
     info.si_signo = sig;
     info.si_errno = 0;
     info.si_code  = code;
     info.si_addr  = addr;
     info.si_trapno = trapno;
     return force_sig_info(&info);
 }
 
 /* For the rare architectures that include trap information using
  * si_trapno.
  */
 int send_sig_fault_trapno(int sig, int code, void __user *addr, int trapno,
               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;
     info.si_trapno = trapno;
     return send_sig_info(info.si_signo, &info, t);
 }
 
 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)
 {
     return __sigqueue_alloc(-1, current, GFP_KERNEL, 0, SIGQUEUE_PREALLOC);
 }
 
 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;
 }
 
 static void do_notify_pidfd(struct task_struct *task)
 {
     struct pid *pid;
 
     WARN_ON(task->exit_state == 0);
     pid = task_pid(task);
     wake_up_all(&pid->wait_pidfd);
 }
 
 /*
  * 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;
 
     WARN_ON_ONCE(sig == -1);
 
     /* do_notify_parent_cldstop should have been called instead.  */
     WARN_ON_ONCE(task_is_stopped_or_traced(tsk));
 
     WARN_ON_ONCE(!tsk->ptrace &&
            (tsk->group_leader != tsk || !thread_group_empty(tsk)));
 
     /* Wake up all pidfd waiters */
     do_notify_pidfd(tsk);
 
     if (sig != SIGCHLD) {
         /*
          * This is only possible if parent == real_parent.
          * Check if it has changed security domain.
          */
         if (tsk->parent_exec_id != READ_ONCE(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;
     }
     /*
      * Send with __send_signal as si_pid and si_uid are in the
      * parent's namespaces.
      */
     if (valid_signal(sig) && sig)
         __send_signal_locked(sig, &info, tsk->parent, PIDTYPE_TGID, false);
     __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))
         send_signal_locked(SIGCHLD, &info, parent, PIDTYPE_TGID);
     /*
      * Even if SIGCHLD is not generated, we must wake up wait4 calls.
      */
     __wake_up_parent(tsk, parent);
     spin_unlock_irqrestore(&sighand->siglock, flags);
 }
 
 /*
  * 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.
  *
  * Returns the signal the ptracer requested the code resume
  * with.  If the code did not stop because the tracer is gone,
  * the stop signal remains unchanged unless clear_code.
  */
 static int ptrace_stop(int exit_code, int why, unsigned long message,
                kernel_siginfo_t *info)
     __releases(&current->sighand->siglock)
     __acquires(&current->sighand->siglock)
 {
     bool gstop_done = false;
 
     if (arch_ptrace_stop_needed()) {
         /*
          * 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.
          */
         spin_unlock_irq(&current->sighand->siglock);
         arch_ptrace_stop();
         spin_lock_irq(&current->sighand->siglock);
     }
 
     /*
      * After this point ptrace_signal_wake_up or signal_wake_up
      * will clear TASK_TRACED if ptrace_unlink happens or a fatal
      * signal comes in.  Handle previous ptrace_unlinks and fatal
      * signals here to prevent ptrace_stop sleeping in schedule.
      */
     if (!current->ptrace || __fatal_signal_pending(current))
         return exit_code;
 
     set_special_state(TASK_TRACED);
     current->jobctl |= JOBCTL_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->ptrace_message = message;
     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);
     /*
      * 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.
      */
     if (current->ptrace)
         do_notify_parent_cldstop(current, true, why);
     if (gstop_done && (!current->ptrace || 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);
     cgroup_enter_frozen();
     preempt_enable_no_resched();
     freezable_schedule();
     cgroup_leave_frozen(true);
 
     /*
      * 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);
     exit_code = current->exit_code;
     current->last_siginfo = NULL;
     current->ptrace_message = 0;
     current->exit_code = 0;
 
     /* LISTENING can be set only during STOP traps, clear it */
     current->jobctl &= ~(JOBCTL_LISTENING | JOBCTL_PTRACE_FROZEN);
 
     /*
      * 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);
     return exit_code;
 }
 
 static int ptrace_do_notify(int signr, int exit_code, int why, unsigned long message)
 {
     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.  */
     return ptrace_stop(exit_code, why, message, &info);
 }
 
 int ptrace_notify(int exit_code, unsigned long message)
 {
     int signr;
 
     BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
     if (unlikely(task_work_pending(current)))
         task_work_run();
 
     spin_lock_irq(&current->sighand->siglock);
     signr = ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED, message);
     spin_unlock_irq(&current->sighand->siglock);
     return signr;
 }
 
 /**
  * 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(sig->flags & SIGNAL_GROUP_EXIT) ||
             unlikely(sig->group_exec_task))
             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;
 
         current->jobctl |= JOBCTL_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 */
         cgroup_enter_frozen();
         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, 0);
     } else {
         WARN_ON_ONCE(!signr);
         ptrace_stop(signr, CLD_STOPPED, 0, NULL);
     }
 }
 
 /**
  * do_freezer_trap - handle the freezer jobctl trap
  *
  * Puts the task into frozen state, if only the task is not about to quit.
  * In this case it drops JOBCTL_TRAP_FREEZE.
  *
  * CONTEXT:
  * Must be called with @current->sighand->siglock held,
  * which is always released before returning.
  */
 static void do_freezer_trap(void)
     __releases(&current->sighand->siglock)
 {
     /*
      * If there are other trap bits pending except JOBCTL_TRAP_FREEZE,
      * let's make another loop to give it a chance to be handled.
      * In any case, we'll return back.
      */
     if ((current->jobctl & (JOBCTL_PENDING_MASK | JOBCTL_TRAP_FREEZE)) !=
          JOBCTL_TRAP_FREEZE) {
         spin_unlock_irq(&current->sighand->siglock);
         return;
     }
 
     /*
      * Now we're sure that there is no pending fatal signal and no
      * pending traps. Clear TIF_SIGPENDING to not get out of schedule()
      * immediately (if there is a non-fatal signal pending), and
      * put the task into sleep.
      */
     __set_current_state(TASK_INTERRUPTIBLE);
     clear_thread_flag(TIF_SIGPENDING);
     spin_unlock_irq(&current->sighand->siglock);
     cgroup_enter_frozen();
     freezable_schedule();
 }
 
 static int ptrace_signal(int signr, kernel_siginfo_t *info, enum pid_type type)
 {
     /*
      * 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;
     signr = ptrace_stop(signr, CLD_TRAPPED, 0, info);
 
     /* We're back.  Did the debugger cancel the sig?  */
     if (signr == 0)
         return signr;
 
     /*
      * 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) ||
         fatal_signal_pending(current)) {
         send_signal_locked(signr, info, current, type);
         signr = 0;
     }
 
     return signr;
 }
 
 static void hide_si_addr_tag_bits(struct ksignal *ksig)
 {
     switch (siginfo_layout(ksig->sig, ksig->info.si_code)) {
     case SIL_FAULT:
     case SIL_FAULT_TRAPNO:
     case SIL_FAULT_MCEERR:
     case SIL_FAULT_BNDERR:
     case SIL_FAULT_PKUERR:
     case SIL_FAULT_PERF_EVENT:
         ksig->info.si_addr = arch_untagged_si_addr(
             ksig->info.si_addr, ksig->sig, ksig->info.si_code);
         break;
     case SIL_KILL:
     case SIL_TIMER:
     case SIL_POLL:
     case SIL_CHLD:
     case SIL_RT:
     case SIL_SYS:
         break;
     }
 }
 
 bool get_signal(struct ksignal *ksig)
 {
     struct sighand_struct *sighand = current->sighand;
     struct signal_struct *signal = current->signal;
     int signr;
 
     clear_notify_signal();
     if (unlikely(task_work_pending(current)))
         task_work_run();
 
     if (!task_sigpending(current))
         return false;
 
     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;
     }
 
     for (;;) {
         struct k_sigaction *ka;
         enum pid_type type;
 
         /* Has this task already been marked for death? */
         if ((signal->flags & SIGNAL_GROUP_EXIT) ||
              signal->group_exec_task) {
             ksig->info.si_signo = signr = SIGKILL;
             sigdelset(&current->pending.signal, SIGKILL);
             trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
                 &sighand->action[SIGKILL - 1]);
             recalc_sigpending();
             goto fatal;
         }
 
         if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
             do_signal_stop(0))
             goto relock;
 
         if (unlikely(current->jobctl &
                  (JOBCTL_TRAP_MASK | JOBCTL_TRAP_FREEZE))) {
             if (current->jobctl & JOBCTL_TRAP_MASK) {
                 do_jobctl_trap();
                 spin_unlock_irq(&sighand->siglock);
             } else if (current->jobctl & JOBCTL_TRAP_FREEZE)
                 do_freezer_trap();
 
             goto relock;
         }
 
         /*
          * If the task is leaving the frozen state, let's update
          * cgroup counters and reset the frozen bit.
          */
         if (unlikely(cgroup_task_frozen(current))) {
             spin_unlock_irq(&sighand->siglock);
             cgroup_leave_frozen(false);
             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.
          */
         type = PIDTYPE_PID;
         signr = dequeue_synchronous_signal(&ksig->info);
         if (!signr)
             signr = dequeue_signal(current, &current->blocked,
                            &ksig->info, &type);
 
         if (!signr)
             break; /* will return 0 */
 
         if (unlikely(current->ptrace) && (signr != SIGKILL) &&
             !(sighand->action[signr -1].sa.sa_flags & SA_IMMUTABLE)) {
             signr = ptrace_signal(signr, &ksig->info, type);
             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);
         if (unlikely(cgroup_task_frozen(current)))
             cgroup_leave_frozen(true);
 
         /*
          * 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);
         }
 
         /*
          * PF_IO_WORKER threads will catch and exit on fatal signals
          * themselves. They have cleanup that must be performed, so
          * we cannot call do_exit() on their behalf.
          */
         if (current->flags & PF_IO_WORKER)
             goto out;
 
         /*
          * Death signals, no core dump.
          */
         do_group_exit(ksig->info.si_signo);
         /* NOTREACHED */
     }
     spin_unlock_irq(&sighand->siglock);
 out:
     ksig->sig = signr;
 
     if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
         hide_si_addr_tag_bits(ksig);
 
     return ksig->sig > 0;
 }
 
 /**
  * signal_delivered - called after signal delivery to update blocked signals
  * @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);
     if (current->sas_ss_flags & SS_AUTODISARM)
         sas_ss_reset(current);
     if (stepping)
         ptrace_notify(SIGTRAP, 0);
 }
 
 void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
 {
     if (failed)
         force_sigsegv(ksig->sig);
     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 (!task_sigpending(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) || (tsk->signal->flags & SIGNAL_GROUP_EXIT)) {
         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 (!task_sigpending(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 (task_sigpending(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.
  *
  * Note that it does set_restore_sigmask() in advance, so it must be always
  * paired with restore_saved_sigmask_unless() before return from syscall.
  */
 int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize)
 {
     sigset_t kmask;
 
     if (!umask)
         return 0;
     if (sigsetsize != sizeof(sigset_t))
         return -EINVAL;
     if (copy_from_user(&kmask, umask, sizeof(sigset_t)))
         return -EFAULT;
 
     set_restore_sigmask();
     current->saved_sigmask = current->blocked;
     set_current_blocked(&kmask);
 
     return 0;
 }
 
 #ifdef CONFIG_COMPAT
 int set_compat_user_sigmask(const compat_sigset_t __user *umask,
                 size_t sigsetsize)
 {
     sigset_t kmask;
 
     if (!umask)
         return 0;
     if (sigsetsize != sizeof(compat_sigset_t))
         return -EINVAL;
     if (get_compat_sigset(&kmask, umask))
         return -EFAULT;
 
     set_restore_sigmask();
     current->saved_sigmask = current->blocked;
     set_current_blocked(&kmask);
 
     return 0;
 }
 #endif
 
 /**
  *  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 ((sig == SIGTRAP) && (si_code == TRAP_PERF))
                 layout = SIL_FAULT_PERF_EVENT;
             else if (IS_ENABLED(CONFIG_SPARC) &&
                  (sig == SIGILL) && (si_code == ILL_ILLTRP))
                 layout = SIL_FAULT_TRAPNO;
             else if (IS_ENABLED(CONFIG_ALPHA) &&
                  ((sig == SIGFPE) ||
                   ((sig == SIGTRAP) && (si_code == TRAP_UNK))))
                 layout = SIL_FAULT_TRAPNO;
         }
         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
 /**
  * copy_siginfo_to_external32 - copy a kernel siginfo into a compat user siginfo
  * @to: compat siginfo destination
  * @from: kernel siginfo source
  *
  * Note: This function does not work properly for the SIGCHLD on x32, but
  * fortunately it doesn't have to.  The only valid callers for this function are
  * copy_siginfo_to_user32, which is overriden for x32 and the coredump code.
  * The latter does not care because SIGCHLD will never cause a coredump.
  */
 void copy_siginfo_to_external32(struct compat_siginfo *to,
         const struct kernel_siginfo *from)
 {
     memset(to, 0, sizeof(*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 = ptr_to_compat(from->si_addr);
         break;
     case SIL_FAULT_TRAPNO:
         to->si_addr = ptr_to_compat(from->si_addr);
         to->si_trapno = from->si_trapno;
         break;
     case SIL_FAULT_MCEERR:
         to->si_addr = ptr_to_compat(from->si_addr);
         to->si_addr_lsb = from->si_addr_lsb;
         break;
     case SIL_FAULT_BNDERR:
         to->si_addr = ptr_to_compat(from->si_addr);
         to->si_lower = ptr_to_compat(from->si_lower);
         to->si_upper = ptr_to_compat(from->si_upper);
         break;
     case SIL_FAULT_PKUERR:
         to->si_addr = ptr_to_compat(from->si_addr);
         to->si_pkey = from->si_pkey;
         break;
     case SIL_FAULT_PERF_EVENT:
         to->si_addr = ptr_to_compat(from->si_addr);
         to->si_perf_data = from->si_perf_data;
         to->si_perf_type = from->si_perf_type;
         to->si_perf_flags = from->si_perf_flags;
         break;
     case SIL_CHLD:
         to->si_pid = from->si_pid;
         to->si_uid = from->si_uid;
         to->si_status = from->si_status;
         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 = ptr_to_compat(from->si_call_addr);
         to->si_syscall   = from->si_syscall;
         to->si_arch      = from->si_arch;
         break;
     }
 }
 
 int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
                const struct kernel_siginfo *from)
 {
     struct compat_siginfo new;
 
     copy_siginfo_to_external32(&new, from);
     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);
         break;
     case SIL_FAULT_TRAPNO:
         to->si_addr = compat_ptr(from->si_addr);
         to->si_trapno = from->si_trapno;
         break;
     case SIL_FAULT_MCEERR:
         to->si_addr = compat_ptr(from->si_addr);
         to->si_addr_lsb = from->si_addr_lsb;
         break;
     case SIL_FAULT_BNDERR:
         to->si_addr = compat_ptr(from->si_addr);
         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);
         to->si_pkey = from->si_pkey;
         break;
     case SIL_FAULT_PERF_EVENT:
         to->si_addr = compat_ptr(from->si_addr);
         to->si_perf_data = from->si_perf_data;
         to->si_perf_type = from->si_perf_type;
         to->si_perf_flags = from->si_perf_flags;
         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;
     enum pid_type type;
     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, &type);
     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, &type);
     }
     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);
 }
 
 /*
  * 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 __user *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);
 }
 
 static struct pid *pidfd_to_pid(const struct file *file)
 {
     struct pid *pid;
 
     pid = pidfd_pid(file);
     if (!IS_ERR(pid))
         return pid;
 
     return tgid_pidfd_to_pid(file);
 }
 
 /**
  * sys_pidfd_send_signal - Signal a process through a pidfd
  * @pidfd:  file descriptor of the process
  * @sig:    signal to send
  * @info:   signal info
  * @flags:  future flags
  *
  * 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(pidfd);
     if (!f.file)
         return -EBADF;
 
     /* Is this a pidfd? */
     pid = 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;
 
         /* Only allow sending arbitrary signals to yourself. */
         ret = -EPERM;
         if ((task_pid(current) != pid) &&
             (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL))
             goto err;
     } else {
         prepare_kill_siginfo(sig, &kinfo);
     }
 
     ret = kill_pid_info(sig, &kinfo, pid);
 
 err:
     fdput(f);
     return ret;
 }
 
 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 (k->sa.sa_flags & SA_IMMUTABLE) {
         spin_unlock_irq(&p->sighand->siglock);
         return -EINVAL;
     }
     if (oact)
         *oact = *k;
 
     /*
      * Make sure that we never accidentally claim to support SA_UNSUPPORTED,
      * e.g. by having an architecture use the bit in their uapi.
      */
     BUILD_BUG_ON(UAPI_SA_FLAGS & SA_UNSUPPORTED);
 
     /*
      * Clear unknown flag bits in order to allow userspace to detect missing
      * support for flag bits and to allow the kernel to use non-uapi bits
      * internally.
      */
     if (act)
         act->sa.sa_flags &= UAPI_SA_FLAGS;
     if (oact)
         oact->sa.sa_flags &= UAPI_SA_FLAGS;
 
     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;
 }
 
 #ifdef CONFIG_DYNAMIC_SIGFRAME
 static inline void sigaltstack_lock(void)
     __acquires(&current->sighand->siglock)
 {
     spin_lock_irq(&current->sighand->siglock);
 }
 
 static inline void sigaltstack_unlock(void)
     __releases(&current->sighand->siglock)
 {
     spin_unlock_irq(&current->sighand->siglock);
 }
 #else
 static inline void sigaltstack_lock(void) { }
 static inline void sigaltstack_unlock(void) { }
 #endif
 
 static int
 do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp,
         size_t min_ss_size)
 {
     struct task_struct *t = current;
     int ret = 0;
 
     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;
 
         /*
          * Return before taking any locks if no actual
          * sigaltstack changes were requested.
          */
         if (t->sas_ss_sp == (unsigned long)ss_sp &&
             t->sas_ss_size == ss_size &&
             t->sas_ss_flags == ss_flags)
             return 0;
 
         sigaltstack_lock();
         if (ss_mode == SS_DISABLE) {
             ss_size = 0;
             ss_sp = NULL;
         } else {
             if (unlikely(ss_size < min_ss_size))
                 ret = -ENOMEM;
             if (!sigaltstack_size_valid(ss_size))
                 ret = -ENOMEM;
         }
         if (!ret) {
             t->sas_ss_sp = (unsigned long) ss_sp;
             t->sas_ss_size = ss_size;
             t->sas_ss_flags = ss_flags;
         }
         sigaltstack_unlock();
     }
     return ret;
 }
 
 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);
     return err;
 }
 
 #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);
     return err;
 }
 #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_trapno);
     CHECK_OFFSET(si_addr_lsb);
     CHECK_OFFSET(si_lower);
     CHECK_OFFSET(si_upper);
     CHECK_OFFSET(si_pkey);
     CHECK_OFFSET(si_perf_data);
     CHECK_OFFSET(si_perf_type);
     CHECK_OFFSET(si_perf_flags);
 
     /* 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
 
     /* usb asyncio */
     BUILD_BUG_ON(offsetof(struct siginfo, si_pid) !=
              offsetof(struct siginfo, si_addr));
     if (sizeof(int) == sizeof(void __user *)) {
         BUILD_BUG_ON(sizeof_field(struct siginfo, si_pid) !=
                  sizeof(void __user *));
     } else {
         BUILD_BUG_ON((sizeof_field(struct siginfo, si_pid) +
                   sizeof_field(struct siginfo, si_uid)) !=
                  sizeof(void __user *));
         BUILD_BUG_ON(offsetofend(struct siginfo, si_pid) !=
                  offsetof(struct siginfo, si_uid));
     }
 #ifdef CONFIG_COMPAT
     BUILD_BUG_ON(offsetof(struct compat_siginfo, si_pid) !=
              offsetof(struct compat_siginfo, si_addr));
     BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
              sizeof(compat_uptr_t));
     BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
              sizeof_field(struct siginfo, si_pid));
 #endif
 }
 
 void __init signals_init(void)
 {
     siginfo_buildtime_checks();
 
     sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC | SLAB_ACCOUNT);
 }
 
 #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 (!task_is_running(t) && 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_locked(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 */