TOMOYO Linux Cross Reference
Linux/kernel/signal.c

   // 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/mm.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>
  #include <linux/sysctl.h>
  #include <uapi/linux/pidfd.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;
 }
 
 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;
         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 dying, we handle all new signals by ignoring them */
         if (fatal_signal_pending(tsk))
                 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, drop the signal.
                  */
                 return false;
         } 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.
          *
          * Try the suggested task first (may or may not be the main thread).
          */
         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;
                         __for_each_thread(signal, t) {
                                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
                                 sigaddset(&t->pending.signal, SIGKILL);
                                 signal_wake_up(t, 1);
                         }
                         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 = task_pt_regs(current);
         struct file *exe_file;
 
         exe_file = get_task_exe_file(current);
         if (exe_file) {
                 pr_info("%pD: %s: potentially unexpected fatal signal %d.\n",
                         exe_file, current->comm, signr);
                 fput(exe_file);
         } else {
                 pr_info("%s: potentially unexpected fatal signal %d.\n",
                         current->comm, 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);
         }
         /*
          * 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);
         /* This can happen if the signal was already pending and blocked */
         if (!task_sigpending(t))
                 signal_wake_up(t, 0);
         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;
         int count = 0;
 
         p->signal->group_stop_count = 0;
 
         for_other_threads(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 thread group or to the
  * individual thread if type == PIDTYPE_PID.
  */
 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 ret = -ESRCH;
 
         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
                 int err = group_send_sig_info(sig, info, p, PIDTYPE_PGID);
                 /*
                  * If group_send_sig_info() succeeds at least once ret
                  * becomes 0 and after that the code below has no effect.
                  * Otherwise we return the last err or -ESRCH if this
                  * process group is empty.
                  */
                 if (ret)
                         ret = err;
         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 
         return ret;
 }
 
 static int kill_pid_info_type(int sig, struct kernel_siginfo *info,
                                 struct pid *pid, enum pid_type type)
 {
         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, type);
                 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.
                  */
         }
 }
 
 int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)
 {
         return kill_pid_info_type(sig, info, pid, PIDTYPE_TGID);
 }
 
 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,
                             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;
         return force_sig_info_to_task(&info, t, HANDLER_CURRENT);
 }
 
 int force_sig_fault(int sig, int code, void __user *addr)
 {
         return force_sig_fault_to_task(sig, code, addr, current);
 }
 
 int send_sig_fault(int sig, int code, void __user *addr, 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;
         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);
 }
 
 static int kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp)
 {
         int ret;
         read_lock(&tasklist_lock);
         ret = __kill_pgrp_info(sig, info, pgrp);
         read_unlock(&tasklist_lock);
         return ret;
 }
 
 int kill_pgrp(struct pid *pid, int sig, int priv)
 {
         return kill_pgrp_info(sig, __si_special(priv), pid);
 }
 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();
 
         /*
          * This function is used by POSIX timers to deliver a timer signal.
          * Where type is PIDTYPE_PID (such as for timers with SIGEV_THREAD_ID
          * set), the signal must be delivered to the specific thread (queues
          * into t->pending).
          *
          * Where type is not PIDTYPE_PID, signals must be delivered to the
          * process. In this case, prefer to deliver to current if it is in
          * the same thread group as the target process, which avoids
          * unnecessarily waking up a potentially idle task.
          */
         t = pid_task(pid, type);
         if (!t)
                 goto ret;
         if (type != PIDTYPE_PID && same_thread_group(t, current))
                 t = current;
         if (!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;
 }
 
 void do_notify_pidfd(struct task_struct *task)
 {
         struct pid *pid = task_pid(task);
 
         WARN_ON(task->exit_state == 0);
 
         __wake_up(&pid->wait_pidfd, TASK_NORMAL, 0,
                         poll_to_key(EPOLLIN | EPOLLRDNORM));
 }
 
 /*
  * 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)));
         /*
          * tsk is a group leader and has no threads, wake up the
          * non-PIDFD_THREAD waiters.
          */
         if (thread_group_empty(tsk))
                 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);
 
         /*
          * The previous do_notify_parent_cldstop() invocation woke ptracer.
          * One a PREEMPTION kernel this can result in preemption requirement
          * which will be fulfilled after read_unlock() and the ptracer will be
          * put on the CPU.
          * The ptracer is in wait_task_inactive(, __TASK_TRACED) waiting for
          * this task wait in schedule(). If this task gets preempted then it
          * remains enqueued on the runqueue. The ptracer will observe this and
          * then sleep for a delay of one HZ tick. In the meantime this task
          * gets scheduled, enters schedule() and will wait for the ptracer.
          *
          * This preemption point is not bad from a correctness point of
          * view but extends the runtime by one HZ tick time due to the
          * ptracer's sleep.  The preempt-disable section ensures that there
          * will be no preemption between unlock and schedule() and so
          * improving the performance since the ptracer will observe that
          * the tracee is scheduled out once it gets on the CPU.
          *
          * On PREEMPT_RT locking tasklist_lock does not disable preemption.
          * Therefore the task can be preempted after do_notify_parent_cldstop()
          * before unlocking tasklist_lock so there is no benefit in doing this.
          *
          * In fact disabling preemption is harmful on PREEMPT_RT because
          * the spinlock_t in cgroup_enter_frozen() must not be acquired
          * with preemption disabled due to the 'sleeping' spinlock
          * substitution of RT.
          */
         if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                 preempt_disable();
         read_unlock(&tasklist_lock);
         cgroup_enter_frozen();
         if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                 preempt_enable_no_resched();
         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++;
 
                 for_other_threads(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();
                 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|TASK_FREEZABLE);
         clear_thread_flag(TIF_SIGPENDING);
         spin_unlock_irq(&current->sighand->siglock);
         cgroup_enter_frozen();
         schedule();
 
         /*
          * We could've been woken by task_work, run it to clear
          * TIF_NOTIFY_SIGNAL. The caller will retry if necessary.
          */
         clear_notify_signal();
         if (unlikely(task_work_pending(current)))
                 task_work_run();
 }
 
 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) {
                         signr = SIGKILL;
                         sigdelset(&current->pending.signal, SIGKILL);
                         trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
                                              &sighand->action[SIGKILL-1]);
                         recalc_sigpending();
                         /*
                          * implies do_group_exit() or return to PF_USER_WORKER,
                          * no need to initialize ksig->info/etc.
                          */
                         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(signr))) {
                                 /* 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(signr);
                         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_USER_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. Note that ksig won't
                  * be properly initialized, PF_USER_WORKER's shouldn't use it.
                  */
                 if (current->flags & PF_USER_WORKER)
                         goto out;
 
                 /*
                  * Death signals, no core dump.
                  */
                 do_group_exit(signr);
                 /* NOTREACHED */
         }
         spin_unlock_irq(&sighand->siglock);
 
         ksig->sig = signr;
 
         if (signr && !(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
                 hide_si_addr_tag_bits(ksig);
 out:
         return signr > 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;
 
         for_other_threads(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)) {
                 sched_mm_cid_exit_signals(tsk);
                 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().
          */
         sched_mm_cid_exit_signals(tsk);
         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|TASK_FREEZABLE);
                 ret = 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 void prepare_kill_siginfo(int sig, struct kernel_siginfo *info,
                                  enum pid_type type)
 {
         clear_siginfo(info);
         info->si_signo = sig;
         info->si_errno = 0;
         info->si_code = (type == PIDTYPE_PID) ? SI_TKILL : 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;
         if (ccs_kill_permission(pid, sig))
                 return -EPERM;
 
         prepare_kill_siginfo(sig, &info, PIDTYPE_TGID);
 
         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);
 }
 
 #define PIDFD_SEND_SIGNAL_FLAGS                            \
         (PIDFD_SIGNAL_THREAD | PIDFD_SIGNAL_THREAD_GROUP | \
          PIDFD_SIGNAL_PROCESS_GROUP)
 
 /**
  * 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
  *
  * Send the signal to the thread group or to the individual thread depending
  * on PIDFD_THREAD.
  * In the future extension to @flags may be used to override the default scope
  * of @pidfd.
  *
  * 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;
         enum pid_type type;
 
         /* Enforce flags be set to 0 until we add an extension. */
         if (flags & ~PIDFD_SEND_SIGNAL_FLAGS)
                 return -EINVAL;
 
         /* Ensure that only a single signal scope determining flag is set. */
         if (hweight32(flags & PIDFD_SEND_SIGNAL_FLAGS) > 1)
                 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;
 
         {
                 struct task_struct *task;
                 int id = 0;
 
                 rcu_read_lock();
                 task = pid_task(pid, PIDTYPE_PID);
                 if (task)
                         id = task_pid_vnr(task);
                 rcu_read_unlock();
                 if (task && ccs_kill_permission(id, sig)) {
                         ret = -EPERM;
                         goto err;
                 }
         }
 
         switch (flags) {
         case 0:
                 /* Infer scope from the type of pidfd. */
                 if (f.file->f_flags & PIDFD_THREAD)
                         type = PIDTYPE_PID;
                 else
                         type = PIDTYPE_TGID;
                 break;
         case PIDFD_SIGNAL_THREAD:
                 type = PIDTYPE_PID;
                 break;
         case PIDFD_SIGNAL_THREAD_GROUP:
                 type = PIDTYPE_TGID;
                 break;
         case PIDFD_SIGNAL_PROCESS_GROUP:
                 type = PIDTYPE_PGID;
                 break;
         }
 
         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 || type > PIDTYPE_TGID) &&
                     (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL))
                         goto err;
         } else {
                 prepare_kill_siginfo(sig, &kinfo, type);
         }
 
         if (type == PIDTYPE_PGID)
                 ret = kill_pgrp_info(sig, &kinfo, pid);
         else
                 ret = kill_pid_info_type(sig, &kinfo, pid, type);
 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;
 
         prepare_kill_siginfo(sig, &info, PIDTYPE_PID);
 
         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;
         if (ccs_tgkill_permission(tgid, pid, sig))
                 return -EPERM;
 
         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;
         if (ccs_tkill_permission(pid, sig))
                 return -EPERM;
 
         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;
         if (ccs_sigqueue_permission(pid, sig))
                 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;
         if (ccs_tgsigqueue_permission(tgid, pid, sig))
                 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
 }
 
 #if defined(CONFIG_SYSCTL)
 static struct ctl_table signal_debug_table[] = {
 #ifdef CONFIG_SYSCTL_EXCEPTION_TRACE
         {
                 .procname       = "exception-trace",
                 .data           = &show_unhandled_signals,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec
         },
 #endif
 };
 
 static int __init init_signal_sysctls(void)
 {
         register_sysctl_init("debug", signal_debug_table);
         return 0;
 }
 early_initcall(init_signal_sysctls);
 #endif /* CONFIG_SYSCTL */
 
 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 */