Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

[linux-2.6-microblaze.git] / 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>

#define CREATE_TRACE_POINTS
#include <trace/events/signal.h>

#include <asm/param.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
#include <asm/siginfo.h>
#include <asm/cacheflush.h>
#include <asm/syscall.h>        /* for syscall_get_* */

/*
 * SLAB caches for signal bits.
 */

static struct kmem_cache *sigqueue_cachep;

int print_fatal_signals __read_mostly;

static void __user *sig_handler(struct task_struct *t, int sig)
{
        return t->sighand->action[sig - 1].sa.sa_handler;
}

static inline bool sig_handler_ignored(void __user *handler, int sig)
{
        /* Is it explicitly or implicitly ignored? */
        return handler == SIG_IGN ||
               (handler == SIG_DFL && sig_kernel_ignore(sig));
}

static bool sig_task_ignored(struct task_struct *t, int sig, bool force)
{
        void __user *handler;

        handler = sig_handler(t, sig);

        /* SIGKILL and SIGSTOP may not be sent to the global init */
        if (unlikely(is_global_init(t) && sig_kernel_only(sig)))
                return true;

        if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
            handler == SIG_DFL && !(force && sig_kernel_only(sig)))
                return true;

        /* Only allow kernel generated signals to this kthread */
        if (unlikely((t->flags & PF_KTHREAD) &&
                     (handler == SIG_KTHREAD_KERNEL) && !force))
                return true;

        return sig_handler_ignored(handler, sig);
}

static bool sig_ignored(struct task_struct *t, int sig, bool force)
{
        /*
         * Blocked signals are never ignored, since the
         * signal handler may change by the time it is
         * unblocked.
         */
        if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
                return false;

        /*
         * Tracers may want to know about even ignored signal unless it
         * is SIGKILL which can't be reported anyway but can be ignored
         * by SIGNAL_UNKILLABLE task.
         */
        if (t->ptrace && sig != SIGKILL)
                return false;

        return sig_task_ignored(t, sig, force);
}

/*
 * Re-calculate pending state from the set of locally pending
 * signals, globally pending signals, and blocked signals.
 */
static inline bool has_pending_signals(sigset_t *signal, sigset_t *blocked)
{
        unsigned long ready;
        long i;

        switch (_NSIG_WORDS) {
        default:
                for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
                        ready |= signal->sig[i] &~ blocked->sig[i];
                break;

        case 4: ready  = signal->sig[3] &~ blocked->sig[3];
                ready |= signal->sig[2] &~ blocked->sig[2];
                ready |= signal->sig[1] &~ blocked->sig[1];
                ready |= signal->sig[0] &~ blocked->sig[0];
                break;

        case 2: ready  = signal->sig[1] &~ blocked->sig[1];
                ready |= signal->sig[0] &~ blocked->sig[0];
                break;

        case 1: ready  = signal->sig[0] &~ blocked->sig[0];
        }
        return ready != 0;
}

#define PENDING(p,b) has_pending_signals(&(p)->signal, (b))

static bool recalc_sigpending_tsk(struct task_struct *t)
{
        if ((t->jobctl & (JOBCTL_PENDING_MASK | JOBCTL_TRAP_FREEZE)) ||
            PENDING(&t->pending, &t->blocked) ||
            PENDING(&t->signal->shared_pending, &t->blocked) ||
            cgroup_task_frozen(t)) {
                set_tsk_thread_flag(t, TIF_SIGPENDING);
                return true;
        }

        /*
         * We must never clear the flag in another thread, or in current
         * when it's possible the current syscall is returning -ERESTART*.
         * So we don't clear it here, and only callers who know they should do.
         */
        return false;
}

/*
 * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
 * This is superfluous when called on current, the wakeup is a harmless no-op.
 */
void recalc_sigpending_and_wake(struct task_struct *t)
{
        if (recalc_sigpending_tsk(t))
                signal_wake_up(t, 0);
}

void recalc_sigpending(void)
{
        if (!recalc_sigpending_tsk(current) && !freezing(current))
                clear_thread_flag(TIF_SIGPENDING);

}
EXPORT_SYMBOL(recalc_sigpending);

void calculate_sigpending(void)
{
        /* Have any signals or users of TIF_SIGPENDING been delayed
         * until after fork?
         */
        spin_lock_irq(&current->sighand->siglock);
        set_tsk_thread_flag(current, TIF_SIGPENDING);
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);
}

/* Given the mask, find the first available signal that should be serviced. */

#define SYNCHRONOUS_MASK \
        (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
         sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))

int next_signal(struct sigpending *pending, sigset_t *mask)
{
        unsigned long i, *s, *m, x;
        int sig = 0;

        s = pending->signal.sig;
        m = mask->sig;

        /*
         * Handle the first word specially: it contains the
         * synchronous signals that need to be dequeued first.
         */
        x = *s &~ *m;
        if (x) {
                if (x & SYNCHRONOUS_MASK)
                        x &= SYNCHRONOUS_MASK;
                sig = ffz(~x) + 1;
                return sig;
        }

        switch (_NSIG_WORDS) {
        default:
                for (i = 1; i < _NSIG_WORDS; ++i) {
                        x = *++s &~ *++m;
                        if (!x)
                                continue;
                        sig = ffz(~x) + i*_NSIG_BPW + 1;
                        break;
                }
                break;

        case 2:
                x = s[1] &~ m[1];
                if (!x)
                        break;
                sig = ffz(~x) + _NSIG_BPW + 1;
                break;

        case 1:
                /* Nothing to do */
                break;
        }

        return sig;
}

static inline void print_dropped_signal(int sig)
{
        static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);

        if (!print_fatal_signals)
                return;

        if (!__ratelimit(&ratelimit_state))
                return;

        pr_info("%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
                                current->comm, current->pid, sig);
}

/**
 * task_set_jobctl_pending - set jobctl pending bits
 * @task: target task
 * @mask: pending bits to set
 *
 * Clear @mask from @task->jobctl.  @mask must be subset of
 * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK |
 * %JOBCTL_TRAPPING.  If stop signo is being set, the existing signo is
 * cleared.  If @task is already being killed or exiting, this function
 * becomes noop.
 *
 * CONTEXT:
 * Must be called with @task->sighand->siglock held.
 *
 * RETURNS:
 * %true if @mask is set, %false if made noop because @task was dying.
 */
bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
{
        BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
                        JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
        BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK));

        if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING)))
                return false;

        if (mask & JOBCTL_STOP_SIGMASK)
                task->jobctl &= ~JOBCTL_STOP_SIGMASK;

        task->jobctl |= mask;
        return true;
}

/**
 * task_clear_jobctl_trapping - clear jobctl trapping bit
 * @task: target task
 *
 * If JOBCTL_TRAPPING is set, a ptracer is waiting for us to enter TRACED.
 * Clear it and wake up the ptracer.  Note that we don't need any further
 * locking.  @task->siglock guarantees that @task->parent points to the
 * ptracer.
 *
 * CONTEXT:
 * Must be called with @task->sighand->siglock held.
 */
void task_clear_jobctl_trapping(struct task_struct *task)
{
        if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
                task->jobctl &= ~JOBCTL_TRAPPING;
                smp_mb();       /* advised by wake_up_bit() */
                wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
        }
}

/**
 * task_clear_jobctl_pending - clear jobctl pending bits
 * @task: target task
 * @mask: pending bits to clear
 *
 * Clear @mask from @task->jobctl.  @mask must be subset of
 * %JOBCTL_PENDING_MASK.  If %JOBCTL_STOP_PENDING is being cleared, other
 * STOP bits are cleared together.
 *
 * If clearing of @mask leaves no stop or trap pending, this function calls
 * task_clear_jobctl_trapping().
 *
 * CONTEXT:
 * Must be called with @task->sighand->siglock held.
 */
void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
{
        BUG_ON(mask & ~JOBCTL_PENDING_MASK);

        if (mask & JOBCTL_STOP_PENDING)
                mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED;

        task->jobctl &= ~mask;

        if (!(task->jobctl & JOBCTL_PENDING_MASK))
                task_clear_jobctl_trapping(task);
}

/**
 * task_participate_group_stop - participate in a group stop
 * @task: task participating in a group stop
 *
 * @task has %JOBCTL_STOP_PENDING set and is participating in a group stop.
 * Group stop states are cleared and the group stop count is consumed if
 * %JOBCTL_STOP_CONSUME was set.  If the consumption completes the group
 * stop, the appropriate `SIGNAL_*` flags are set.
 *
 * CONTEXT:
 * Must be called with @task->sighand->siglock held.
 *
 * RETURNS:
 * %true if group stop completion should be notified to the parent, %false
 * otherwise.
 */
static bool task_participate_group_stop(struct task_struct *task)
{
        struct signal_struct *sig = task->signal;
        bool consume = task->jobctl & JOBCTL_STOP_CONSUME;

        WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING));

        task_clear_jobctl_pending(task, JOBCTL_STOP_PENDING);

        if (!consume)
                return false;

        if (!WARN_ON_ONCE(sig->group_stop_count == 0))
                sig->group_stop_count--;

        /*
         * Tell the caller to notify completion iff we are entering into a
         * fresh group stop.  Read comment in do_signal_stop() for details.
         */
        if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
                signal_set_stop_flags(sig, SIGNAL_STOP_STOPPED);
                return true;
        }
        return false;
}

void task_join_group_stop(struct task_struct *task)
{
        unsigned long mask = current->jobctl & JOBCTL_STOP_SIGMASK;
        struct signal_struct *sig = current->signal;

        if (sig->group_stop_count) {
                sig->group_stop_count++;
                mask |= JOBCTL_STOP_CONSUME;
        } else if (!(sig->flags & SIGNAL_STOP_STOPPED))
                return;

        /* Have the new thread join an on-going signal group stop */
        task_set_jobctl_pending(task, mask | JOBCTL_STOP_PENDING);
}

/*
 * allocate a new signal queue record
 * - this may be called without locks if and only if t == current, otherwise an
 *   appropriate lock must be held to stop the target task from exiting
 */
static struct sigqueue *
__sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags,
                 int override_rlimit, const unsigned int sigqueue_flags)
{
        struct sigqueue *q = NULL;
        struct ucounts *ucounts = NULL;
        long sigpending;

        /*
         * Protect access to @t credentials. This can go away when all
         * callers hold rcu read lock.
         *
         * NOTE! A pending signal will hold on to the user refcount,
         * and we get/put the refcount only when the sigpending count
         * changes from/to zero.
         */
        rcu_read_lock();
        ucounts = task_ucounts(t);
        sigpending = inc_rlimit_get_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);
        rcu_read_unlock();
        if (!sigpending)
                return NULL;

        if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
                q = kmem_cache_alloc(sigqueue_cachep, gfp_flags);
        } else {
                print_dropped_signal(sig);
        }

        if (unlikely(q == NULL)) {
                dec_rlimit_put_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);
        } else {
                INIT_LIST_HEAD(&q->list);
                q->flags = sigqueue_flags;
                q->ucounts = ucounts;
        }
        return q;
}

static void __sigqueue_free(struct sigqueue *q)
{
        if (q->flags & SIGQUEUE_PREALLOC)
                return;
        if (q->ucounts) {
                dec_rlimit_put_ucounts(q->ucounts, UCOUNT_RLIMIT_SIGPENDING);
                q->ucounts = NULL;
        }
        kmem_cache_free(sigqueue_cachep, q);
}

void flush_sigqueue(struct sigpending *queue)
{
        struct sigqueue *q;

        sigemptyset(&queue->signal);
        while (!list_empty(&queue->list)) {
                q = list_entry(queue->list.next, struct sigqueue , list);
                list_del_init(&q->list);
                __sigqueue_free(q);
        }
}

/*
 * Flush all pending signals for this kthread.
 */
void flush_signals(struct task_struct *t)
{
        unsigned long flags;

        spin_lock_irqsave(&t->sighand->siglock, flags);
        clear_tsk_thread_flag(t, TIF_SIGPENDING);
        flush_sigqueue(&t->pending);
        flush_sigqueue(&t->signal->shared_pending);
        spin_unlock_irqrestore(&t->sighand->siglock, flags);
}
EXPORT_SYMBOL(flush_signals);

#ifdef CONFIG_POSIX_TIMERS
static void __flush_itimer_signals(struct sigpending *pending)
{
        sigset_t signal, retain;
        struct sigqueue *q, *n;

        signal = pending->signal;
        sigemptyset(&retain);

        list_for_each_entry_safe(q, n, &pending->list, list) {
                int sig = q->info.si_signo;

                if (likely(q->info.si_code != SI_TIMER)) {
                        sigaddset(&retain, sig);
                } else {
                        sigdelset(&signal, sig);
                        list_del_init(&q->list);
                        __sigqueue_free(q);
                }
        }

        sigorsets(&pending->signal, &signal, &retain);
}

void flush_itimer_signals(void)
{
        struct task_struct *tsk = current;
        unsigned long flags;

        spin_lock_irqsave(&tsk->sighand->siglock, flags);
        __flush_itimer_signals(&tsk->pending);
        __flush_itimer_signals(&tsk->signal->shared_pending);
        spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
}
#endif

void ignore_signals(struct task_struct *t)
{
        int i;

        for (i = 0; i < _NSIG; ++i)
                t->sighand->action[i].sa.sa_handler = SIG_IGN;

        flush_signals(t);
}

/*
 * Flush all handlers for a task.
 */

void
flush_signal_handlers(struct task_struct *t, int force_default)
{
        int i;
        struct k_sigaction *ka = &t->sighand->action[0];
        for (i = _NSIG ; i != 0 ; i--) {
                if (force_default || ka->sa.sa_handler != SIG_IGN)
                        ka->sa.sa_handler = SIG_DFL;
                ka->sa.sa_flags = 0;
#ifdef __ARCH_HAS_SA_RESTORER
                ka->sa.sa_restorer = NULL;
#endif
                sigemptyset(&ka->sa.sa_mask);
                ka++;
        }
}

bool unhandled_signal(struct task_struct *tsk, int sig)
{
        void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
        if (is_global_init(tsk))
                return true;

        if (handler != SIG_IGN && handler != SIG_DFL)
                return false;

        /* If 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;
                        t = p;
                        do {
                                task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
                                sigaddset(&t->pending.signal, SIGKILL);
                                signal_wake_up(t, 1);
                        } while_each_thread(p, t);
                        return;
                }
        }

        /*
         * The signal is already in the shared-pending queue.
         * Tell the chosen thread to wake up and dequeue it.
         */
        signal_wake_up(t, sig == SIGKILL);
        return;
}

static inline bool legacy_queue(struct sigpending *signals, int sig)
{
        return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
}

static int __send_signal_locked(int sig, struct kernel_siginfo *info,
                                struct task_struct *t, enum pid_type type, bool force)
{
        struct sigpending *pending;
        struct sigqueue *q;
        int override_rlimit;
        int ret = 0, result;

        lockdep_assert_held(&t->sighand->siglock);

        result = TRACE_SIGNAL_IGNORED;
        if (!prepare_signal(sig, t, force))
                goto ret;

        pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;
        /*
         * Short-circuit ignored signals and support queuing
         * exactly one non-rt signal, so that we can get more
         * detailed information about the cause of the signal.
         */
        result = TRACE_SIGNAL_ALREADY_PENDING;
        if (legacy_queue(pending, sig))
                goto ret;

        result = TRACE_SIGNAL_DELIVERED;
        /*
         * Skip useless siginfo allocation for SIGKILL and kernel threads.
         */
        if ((sig == SIGKILL) || (t->flags & PF_KTHREAD))
                goto out_set;

        /*
         * Real-time signals must be queued if sent by sigqueue, or
         * some other real-time mechanism.  It is implementation
         * defined whether kill() does so.  We attempt to do so, on
         * the principle of least surprise, but since kill is not
         * allowed to fail with EAGAIN when low on memory we just
         * make sure at least one signal gets delivered and don't
         * pass on the info struct.
         */
        if (sig < SIGRTMIN)
                override_rlimit = (is_si_special(info) || info->si_code >= 0);
        else
                override_rlimit = 0;

        q = __sigqueue_alloc(sig, t, GFP_ATOMIC, override_rlimit, 0);

        if (q) {
                list_add_tail(&q->list, &pending->list);
                switch ((unsigned long) info) {
                case (unsigned long) SEND_SIG_NOINFO:
                        clear_siginfo(&q->info);
                        q->info.si_signo = sig;
                        q->info.si_errno = 0;
                        q->info.si_code = SI_USER;
                        q->info.si_pid = task_tgid_nr_ns(current,
                                                        task_active_pid_ns(t));
                        rcu_read_lock();
                        q->info.si_uid =
                                from_kuid_munged(task_cred_xxx(t, user_ns),
                                                 current_uid());
                        rcu_read_unlock();
                        break;
                case (unsigned long) SEND_SIG_PRIV:
                        clear_siginfo(&q->info);
                        q->info.si_signo = sig;
                        q->info.si_errno = 0;
                        q->info.si_code = SI_KERNEL;
                        q->info.si_pid = 0;
                        q->info.si_uid = 0;
                        break;
                default:
                        copy_siginfo(&q->info, info);
                        break;
                }
        } else if (!is_si_special(info) &&
                   sig >= SIGRTMIN && info->si_code != SI_USER) {
                /*
                 * Queue overflow, abort.  We may abort if the
                 * signal was rt and sent by user using something
                 * other than kill().
                 */
                result = TRACE_SIGNAL_OVERFLOW_FAIL;
                ret = -EAGAIN;
                goto ret;
        } else {
                /*
                 * This is a silent loss of information.  We still
                 * send the signal, but the *info bits are lost.
                 */
                result = TRACE_SIGNAL_LOSE_INFO;
        }

out_set:
        signalfd_notify(t, sig);
        sigaddset(&pending->signal, sig);

        /* Let multiprocess signals appear after on-going forks */
        if (type > PIDTYPE_TGID) {
                struct multiprocess_signals *delayed;
                hlist_for_each_entry(delayed, &t->signal->multiprocess, node) {
                        sigset_t *signal = &delayed->signal;
                        /* Can't queue both a stop and a continue signal */
                        if (sig == SIGCONT)
                                sigdelsetmask(signal, SIG_KERNEL_STOP_MASK);
                        else if (sig_kernel_stop(sig))
                                sigdelset(signal, SIGCONT);
                        sigaddset(signal, sig);
                }
        }

        complete_signal(sig, t, type);
ret:
        trace_signal_generate(sig, info, t, type != PIDTYPE_PID, result);
        return ret;
}

static inline bool has_si_pid_and_uid(struct kernel_siginfo *info)
{
        bool ret = false;
        switch (siginfo_layout(info->si_signo, info->si_code)) {
        case SIL_KILL:
        case SIL_CHLD:
        case SIL_RT:
                ret = true;
                break;
        case SIL_TIMER:
        case SIL_POLL:
        case SIL_FAULT:
        case SIL_FAULT_TRAPNO:
        case SIL_FAULT_MCEERR:
        case SIL_FAULT_BNDERR:
        case SIL_FAULT_PKUERR:
        case SIL_FAULT_PERF_EVENT:
        case SIL_SYS:
                ret = false;
                break;
        }
        return ret;
}

int send_signal_locked(int sig, struct kernel_siginfo *info,
                       struct task_struct *t, enum pid_type type)
{
        /* Should SIGKILL or SIGSTOP be received by a pid namespace init? */
        bool force = false;

        if (info == SEND_SIG_NOINFO) {
                /* Force if sent from an ancestor pid namespace */
                force = !task_pid_nr_ns(current, task_active_pid_ns(t));
        } else if (info == SEND_SIG_PRIV) {
                /* Don't ignore kernel generated signals */
                force = true;
        } else if (has_si_pid_and_uid(info)) {
                /* SIGKILL and SIGSTOP is special or has ids */
                struct user_namespace *t_user_ns;

                rcu_read_lock();
                t_user_ns = task_cred_xxx(t, user_ns);
                if (current_user_ns() != t_user_ns) {
                        kuid_t uid = make_kuid(current_user_ns(), info->si_uid);
                        info->si_uid = from_kuid_munged(t_user_ns, uid);
                }
                rcu_read_unlock();

                /* A kernel generated signal? */
                force = (info->si_code == SI_KERNEL);

                /* From an ancestor pid namespace? */
                if (!task_pid_nr_ns(current, task_active_pid_ns(t))) {
                        info->si_pid = 0;
                        force = true;
                }
        }
        return __send_signal_locked(sig, info, t, type, force);
}

static void print_fatal_signal(int signr)
{
        struct pt_regs *regs = 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);
                        recalc_sigpending_and_wake(t);
                }
        }
        /*
         * Don't clear SIGNAL_UNKILLABLE for traced tasks, users won't expect
         * debugging to leave init killable. But HANDLER_EXIT is always fatal.
         */
        if (action->sa.sa_handler == SIG_DFL &&
            (!t->ptrace || (handler == HANDLER_EXIT)))
                t->signal->flags &= ~SIGNAL_UNKILLABLE;
        ret = send_signal_locked(sig, info, t, PIDTYPE_PID);
        spin_unlock_irqrestore(&t->sighand->siglock, flags);

        return ret;
}

int force_sig_info(struct kernel_siginfo *info)
{
        return force_sig_info_to_task(info, current, HANDLER_CURRENT);
}

/*
 * Nuke all other threads in the group.
 */
int zap_other_threads(struct task_struct *p)
{
        struct task_struct *t = p;
        int count = 0;

        p->signal->group_stop_count = 0;

        while_each_thread(p, t) {
                task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
                /* Don't require de_thread to wait for the vhost_worker */
                if ((t->flags & (PF_IO_WORKER | PF_USER_WORKER)) != PF_USER_WORKER)
                        count++;

                /* Don't bother with already dead threads */
                if (t->exit_state)
                        continue;
                sigaddset(&t->pending.signal, SIGKILL);
                signal_wake_up(t, 1);
        }

        return count;
}

struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
                                           unsigned long *flags)
{
        struct sighand_struct *sighand;

        rcu_read_lock();
        for (;;) {
                sighand = rcu_dereference(tsk->sighand);
                if (unlikely(sighand == NULL))
                        break;

                /*
                 * This sighand can be already freed and even reused, but
                 * we rely on SLAB_TYPESAFE_BY_RCU and sighand_ctor() which
                 * initializes ->siglock: this slab can't go away, it has
                 * the same object type, ->siglock can't be reinitialized.
                 *
                 * We need to ensure that tsk->sighand is still the same
                 * after we take the lock, we can race with de_thread() or
                 * __exit_signal(). In the latter case the next iteration
                 * must see ->sighand == NULL.
                 */
                spin_lock_irqsave(&sighand->siglock, *flags);
                if (likely(sighand == rcu_access_pointer(tsk->sighand)))
                        break;
                spin_unlock_irqrestore(&sighand->siglock, *flags);
        }
        rcu_read_unlock();

        return sighand;
}

#ifdef CONFIG_LOCKDEP
void lockdep_assert_task_sighand_held(struct task_struct *task)
{
        struct sighand_struct *sighand;

        rcu_read_lock();
        sighand = rcu_dereference(task->sighand);
        if (sighand)
                lockdep_assert_held(&sighand->siglock);
        else
                WARN_ON_ONCE(1);
        rcu_read_unlock();
}
#endif

/*
 * send signal info to all the members of a group
 */
int group_send_sig_info(int sig, struct kernel_siginfo *info,
                        struct task_struct *p, enum pid_type type)
{
        int ret;

        rcu_read_lock();
        ret = check_kill_permission(sig, info, p);
        rcu_read_unlock();

        if (!ret && sig)
                ret = do_send_sig_info(sig, info, p, type);

        return ret;
}

/*
 * __kill_pgrp_info() sends a signal to a process group: this is what the tty
 * control characters do (^C, ^Z etc)
 * - the caller must hold at least a readlock on tasklist_lock
 */
int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp)
{
        struct task_struct *p = NULL;
        int retval, success;

        success = 0;
        retval = -ESRCH;
        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
                int err = group_send_sig_info(sig, info, p, PIDTYPE_PGID);
                success |= !err;
                retval = err;
        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
        return success ? 0 : retval;
}

int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)
{
        int error = -ESRCH;
        struct task_struct *p;

        for (;;) {
                rcu_read_lock();
                p = pid_task(pid, PIDTYPE_PID);
                if (p)
                        error = group_send_sig_info(sig, info, p, PIDTYPE_TGID);
                rcu_read_unlock();
                if (likely(!p || error != -ESRCH))
                        return error;

                /*
                 * The task was unhashed in between, try again.  If it
                 * is dead, pid_task() will return NULL, if we race with
                 * de_thread() it will find the new leader.
                 */
        }
}

static int kill_proc_info(int sig, struct kernel_siginfo *info, pid_t pid)
{
        int error;
        rcu_read_lock();
        error = kill_pid_info(sig, info, find_vpid(pid));
        rcu_read_unlock();
        return error;
}

static inline bool kill_as_cred_perm(const struct cred *cred,
                                     struct task_struct *target)
{
        const struct cred *pcred = __task_cred(target);

        return uid_eq(cred->euid, pcred->suid) ||
               uid_eq(cred->euid, pcred->uid) ||
               uid_eq(cred->uid, pcred->suid) ||
               uid_eq(cred->uid, pcred->uid);
}

/*
 * The usb asyncio usage of siginfo is wrong.  The glibc support
 * for asyncio which uses SI_ASYNCIO assumes the layout is SIL_RT.
 * AKA after the generic fields:
 *      kernel_pid_t    si_pid;
 *      kernel_uid32_t  si_uid;
 *      sigval_t        si_value;
 *
 * Unfortunately when usb generates SI_ASYNCIO it assumes the layout
 * after the generic fields is:
 *      void __user     *si_addr;
 *
 * This is a practical problem when there is a 64bit big endian kernel
 * and a 32bit userspace.  As the 32bit address will encoded in the low
 * 32bits of the pointer.  Those low 32bits will be stored at higher
 * address than appear in a 32 bit pointer.  So userspace will not
 * see the address it was expecting for it's completions.
 *
 * There is nothing in the encoding that can allow
 * copy_siginfo_to_user32 to detect this confusion of formats, so
 * handle this by requiring the caller of kill_pid_usb_asyncio to
 * notice when this situration takes place and to store the 32bit
 * pointer in sival_int, instead of sival_addr of the sigval_t addr
 * parameter.
 */
int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr,
                         struct pid *pid, const struct cred *cred)
{
        struct kernel_siginfo info;
        struct task_struct *p;
        unsigned long flags;
        int ret = -EINVAL;

        if (!valid_signal(sig))
                return ret;

        clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = errno;
        info.si_code = SI_ASYNCIO;
        *((sigval_t *)&info.si_pid) = addr;

        rcu_read_lock();
        p = pid_task(pid, PIDTYPE_PID);
        if (!p) {
                ret = -ESRCH;
                goto out_unlock;
        }
        if (!kill_as_cred_perm(cred, p)) {
                ret = -EPERM;
                goto out_unlock;
        }
        ret = security_task_kill(p, &info, sig, cred);
        if (ret)
                goto out_unlock;

        if (sig) {
                if (lock_task_sighand(p, &flags)) {
                        ret = __send_signal_locked(sig, &info, p, PIDTYPE_TGID, false);
                        unlock_task_sighand(p, &flags);
                } else
                        ret = -ESRCH;
        }
out_unlock:
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(kill_pid_usb_asyncio);

/*
 * kill_something_info() interprets pid in interesting ways just like kill(2).
 *
 * POSIX specifies that kill(-1,sig) is unspecified, but what we have
 * is probably wrong.  Should make it like BSD or SYSV.
 */

static int kill_something_info(int sig, struct kernel_siginfo *info, pid_t pid)
{
        int ret;

        if (pid > 0)
                return kill_proc_info(sig, info, pid);

        /* -INT_MIN is undefined.  Exclude this case to avoid a UBSAN warning */
        if (pid == INT_MIN)
                return -ESRCH;

        read_lock(&tasklist_lock);
        if (pid != -1) {
                ret = __kill_pgrp_info(sig, info,
                                pid ? find_vpid(-pid) : task_pgrp(current));
        } else {
                int retval = 0, count = 0;
                struct task_struct * p;

                for_each_process(p) {
                        if (task_pid_vnr(p) > 1 &&
                                        !same_thread_group(p, current)) {
                                int err = group_send_sig_info(sig, info, p,
                                                              PIDTYPE_MAX);
                                ++count;
                                if (err != -EPERM)
                                        retval = err;
                        }
                }
                ret = count ? retval : -ESRCH;
        }
        read_unlock(&tasklist_lock);

        return ret;
}

/*
 * These are for backward compatibility with the rest of the kernel source.
 */

int send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p)
{
        /*
         * Make sure legacy kernel users don't send in bad values
         * (normal paths check this in check_kill_permission).
         */
        if (!valid_signal(sig))
                return -EINVAL;

        return do_send_sig_info(sig, info, p, PIDTYPE_PID);
}
EXPORT_SYMBOL(send_sig_info);

#define __si_special(priv) \
        ((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)

int
send_sig(int sig, struct task_struct *p, int priv)
{
        return send_sig_info(sig, __si_special(priv), p);
}
EXPORT_SYMBOL(send_sig);

void force_sig(int sig)
{
        struct kernel_siginfo info;

        clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        info.si_code = SI_KERNEL;
        info.si_pid = 0;
        info.si_uid = 0;
        force_sig_info(&info);
}
EXPORT_SYMBOL(force_sig);

void force_fatal_sig(int sig)
{
        struct kernel_siginfo info;

        clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        info.si_code = SI_KERNEL;
        info.si_pid = 0;
        info.si_uid = 0;
        force_sig_info_to_task(&info, current, HANDLER_SIG_DFL);
}

void force_exit_sig(int sig)
{
        struct kernel_siginfo info;

        clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        info.si_code = SI_KERNEL;
        info.si_pid = 0;
        info.si_uid = 0;
        force_sig_info_to_task(&info, current, HANDLER_EXIT);
}

/*
 * When things go south during signal handling, we
 * will force a SIGSEGV. And if the signal that caused
 * the problem was already a SIGSEGV, we'll want to
 * make sure we don't even try to deliver the signal..
 */
void force_sigsegv(int sig)
{
        if (sig == SIGSEGV)
                force_fatal_sig(SIGSEGV);
        else
                force_sig(SIGSEGV);
}

int force_sig_fault_to_task(int sig, int code, void __user *addr,
                            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);
}

int kill_pgrp(struct pid *pid, int sig, int priv)
{
        int ret;

        read_lock(&tasklist_lock);
        ret = __kill_pgrp_info(sig, __si_special(priv), pid);
        read_unlock(&tasklist_lock);

        return ret;
}
EXPORT_SYMBOL(kill_pgrp);

int kill_pid(struct pid *pid, int sig, int priv)
{
        return kill_pid_info(sig, __si_special(priv), pid);
}
EXPORT_SYMBOL(kill_pid);

/*
 * These functions support sending signals using preallocated sigqueue
 * structures.  This is needed "because realtime applications cannot
 * afford to lose notifications of asynchronous events, like timer
 * expirations or I/O completions".  In the case of POSIX Timers
 * we allocate the sigqueue structure from the timer_create.  If this
 * allocation fails we are able to report the failure to the application
 * with an EAGAIN error.
 */
struct sigqueue *sigqueue_alloc(void)
{
        return __sigqueue_alloc(-1, current, GFP_KERNEL, 0, SIGQUEUE_PREALLOC);
}

void sigqueue_free(struct sigqueue *q)
{
        unsigned long flags;
        spinlock_t *lock = &current->sighand->siglock;

        BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
        /*
         * We must hold ->siglock while testing q->list
         * to serialize with collect_signal() or with
         * __exit_signal()->flush_sigqueue().
         */
        spin_lock_irqsave(lock, flags);
        q->flags &= ~SIGQUEUE_PREALLOC;
        /*
         * If it is queued it will be freed when dequeued,
         * like the "regular" sigqueue.
         */
        if (!list_empty(&q->list))
                q = NULL;
        spin_unlock_irqrestore(lock, flags);

        if (q)
                __sigqueue_free(q);
}

int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
{
        int sig = q->info.si_signo;
        struct sigpending *pending;
        struct task_struct *t;
        unsigned long flags;
        int ret, result;

        BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));

        ret = -1;
        rcu_read_lock();

        /*
         * 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;
}

static void do_notify_pidfd(struct task_struct *task)
{
        struct pid *pid;

        WARN_ON(task->exit_state == 0);
        pid = task_pid(task);
        wake_up_all(&pid->wait_pidfd);
}

/*
 * Let a parent know about the death of a child.
 * For a stopped/continued status change, use do_notify_parent_cldstop instead.
 *
 * Returns true if our parent ignored us and so we've switched to
 * self-reaping.
 */
bool do_notify_parent(struct task_struct *tsk, int sig)
{
        struct kernel_siginfo info;
        unsigned long flags;
        struct sighand_struct *psig;
        bool autoreap = false;
        u64 utime, stime;

        WARN_ON_ONCE(sig == -1);

        /* do_notify_parent_cldstop should have been called instead.  */
        WARN_ON_ONCE(task_is_stopped_or_traced(tsk));

        WARN_ON_ONCE(!tsk->ptrace &&
               (tsk->group_leader != tsk || !thread_group_empty(tsk)));

        /* Wake up all pidfd waiters */
        do_notify_pidfd(tsk);

        if (sig != SIGCHLD) {
                /*
                 * This is only possible if parent == real_parent.
                 * Check if it has changed security domain.
                 */
                if (tsk->parent_exec_id != READ_ONCE(tsk->parent->self_exec_id))
                        sig = SIGCHLD;
        }

        clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        /*
         * We are under tasklist_lock here so our parent is tied to
         * us and cannot change.
         *
         * task_active_pid_ns will always return the same pid namespace
         * until a task passes through release_task.
         *
         * write_lock() currently calls preempt_disable() which is the
         * same as rcu_read_lock(), but according to Oleg, this is not
         * correct to rely on this
         */
        rcu_read_lock();
        info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent));
        info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns),
                                       task_uid(tsk));
        rcu_read_unlock();

        task_cputime(tsk, &utime, &stime);
        info.si_utime = nsec_to_clock_t(utime + tsk->signal->utime);
        info.si_stime = nsec_to_clock_t(stime + tsk->signal->stime);

        info.si_status = tsk->exit_code & 0x7f;
        if (tsk->exit_code & 0x80)
                info.si_code = CLD_DUMPED;
        else if (tsk->exit_code & 0x7f)
                info.si_code = CLD_KILLED;
        else {
                info.si_code = CLD_EXITED;
                info.si_status = tsk->exit_code >> 8;
        }

        psig = tsk->parent->sighand;
        spin_lock_irqsave(&psig->siglock, flags);
        if (!tsk->ptrace && sig == SIGCHLD &&
            (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
             (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
                /*
                 * We are exiting and our parent doesn't care.  POSIX.1
                 * defines special semantics for setting SIGCHLD to SIG_IGN
                 * or setting the SA_NOCLDWAIT flag: we should be reaped
                 * automatically and not left for our parent's wait4 call.
                 * Rather than having the parent do it as a magic kind of
                 * signal handler, we just set this to tell do_exit that we
                 * can be cleaned up without becoming a zombie.  Note that
                 * we still call __wake_up_parent in this case, because a
                 * blocked sys_wait4 might now return -ECHILD.
                 *
                 * Whether we send SIGCHLD or not for SA_NOCLDWAIT
                 * is implementation-defined: we do (if you don't want
                 * it, just use SIG_IGN instead).
                 */
                autoreap = true;
                if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
                        sig = 0;
        }
        /*
         * Send with __send_signal as si_pid and si_uid are in the
         * parent's namespaces.
         */
        if (valid_signal(sig) && sig)
                __send_signal_locked(sig, &info, tsk->parent, PIDTYPE_TGID, false);
        __wake_up_parent(tsk, tsk->parent);
        spin_unlock_irqrestore(&psig->siglock, flags);

        return autoreap;
}

/**
 * do_notify_parent_cldstop - notify parent of stopped/continued state change
 * @tsk: task reporting the state change
 * @for_ptracer: the notification is for ptracer
 * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
 *
 * Notify @tsk's parent that the stopped/continued state has changed.  If
 * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
 * If %true, @tsk reports to @tsk->parent which should be the ptracer.
 *
 * CONTEXT:
 * Must be called with tasklist_lock at least read locked.
 */
static void do_notify_parent_cldstop(struct task_struct *tsk,
                                     bool for_ptracer, int why)
{
        struct kernel_siginfo info;
        unsigned long flags;
        struct task_struct *parent;
        struct sighand_struct *sighand;
        u64 utime, stime;

        if (for_ptracer) {
                parent = tsk->parent;
        } else {
                tsk = tsk->group_leader;
                parent = tsk->real_parent;
        }

        clear_siginfo(&info);
        info.si_signo = SIGCHLD;
        info.si_errno = 0;
        /*
         * see comment in do_notify_parent() about the following 4 lines
         */
        rcu_read_lock();
        info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(parent));
        info.si_uid = from_kuid_munged(task_cred_xxx(parent, user_ns), task_uid(tsk));
        rcu_read_unlock();

        task_cputime(tsk, &utime, &stime);
        info.si_utime = nsec_to_clock_t(utime);
        info.si_stime = nsec_to_clock_t(stime);

        info.si_code = why;
        switch (why) {
        case CLD_CONTINUED:
                info.si_status = SIGCONT;
                break;
        case CLD_STOPPED:
                info.si_status = tsk->signal->group_exit_code & 0x7f;
                break;
        case CLD_TRAPPED:
                info.si_status = tsk->exit_code & 0x7f;
                break;
        default:
                BUG();
        }

        sighand = parent->sighand;
        spin_lock_irqsave(&sighand->siglock, flags);
        if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
            !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
                send_signal_locked(SIGCHLD, &info, parent, PIDTYPE_TGID);
        /*
         * Even if SIGCHLD is not generated, we must wake up wait4 calls.
         */
        __wake_up_parent(tsk, parent);
        spin_unlock_irqrestore(&sighand->siglock, flags);
}

/*
 * This must be called with current->sighand->siglock held.
 *
 * This should be the path for all ptrace stops.
 * We always set current->last_siginfo while stopped here.
 * That makes it a way to test a stopped process for
 * being ptrace-stopped vs being job-control-stopped.
 *
 * Returns the signal the ptracer requested the code resume
 * with.  If the code did not stop because the tracer is gone,
 * the stop signal remains unchanged unless clear_code.
 */
static int ptrace_stop(int exit_code, int why, unsigned long message,
                       kernel_siginfo_t *info)
        __releases(&current->sighand->siglock)
        __acquires(&current->sighand->siglock)
{
        bool gstop_done = false;

        if (arch_ptrace_stop_needed()) {
                /*
                 * The arch code has something special to do before a
                 * ptrace stop.  This is allowed to block, e.g. for faults
                 * on user stack pages.  We can't keep the siglock while
                 * calling arch_ptrace_stop, so we must release it now.
                 * To preserve proper semantics, we must do this before
                 * any signal bookkeeping like checking group_stop_count.
                 */
                spin_unlock_irq(&current->sighand->siglock);
                arch_ptrace_stop();
                spin_lock_irq(&current->sighand->siglock);
        }

        /*
         * After this point ptrace_signal_wake_up or signal_wake_up
         * will clear TASK_TRACED if ptrace_unlink happens or a fatal
         * signal comes in.  Handle previous ptrace_unlinks and fatal
         * signals here to prevent ptrace_stop sleeping in schedule.
         */
        if (!current->ptrace || __fatal_signal_pending(current))
                return exit_code;

        set_special_state(TASK_TRACED);
        current->jobctl |= JOBCTL_TRACED;

        /*
         * We're committing to trapping.  TRACED should be visible before
         * TRAPPING is cleared; otherwise, the tracer might fail do_wait().
         * Also, transition to TRACED and updates to ->jobctl should be
         * atomic with respect to siglock and should be done after the arch
         * hook as siglock is released and regrabbed across it.
         *
         *     TRACER                               TRACEE
         *
         *     ptrace_attach()
         * [L]   wait_on_bit(JOBCTL_TRAPPING)   [S] set_special_state(TRACED)
         *     do_wait()
         *       set_current_state()                smp_wmb();
         *       ptrace_do_wait()
         *         wait_task_stopped()
         *           task_stopped_code()
         * [L]         task_is_traced()         [S] task_clear_jobctl_trapping();
         */
        smp_wmb();

        current->ptrace_message = message;
        current->last_siginfo = info;
        current->exit_code = exit_code;

        /*
         * If @why is CLD_STOPPED, we're trapping to participate in a group
         * stop.  Do the bookkeeping.  Note that if SIGCONT was delievered
         * across siglock relocks since INTERRUPT was scheduled, PENDING
         * could be clear now.  We act as if SIGCONT is received after
         * TASK_TRACED is entered - ignore it.
         */
        if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))
                gstop_done = task_participate_group_stop(current);

        /* any trap clears pending STOP trap, STOP trap clears NOTIFY */
        task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP);
        if (info && info->si_code >> 8 == PTRACE_EVENT_STOP)
                task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY);

        /* entering a trap, clear TRAPPING */
        task_clear_jobctl_trapping(current);

        spin_unlock_irq(&current->sighand->siglock);
        read_lock(&tasklist_lock);
        /*
         * Notify parents of the stop.
         *
         * While ptraced, there are two parents - the ptracer and
         * the real_parent of the group_leader.  The ptracer should
         * know about every stop while the real parent is only
         * interested in the completion of group stop.  The states
         * for the two don't interact with each other.  Notify
         * separately unless they're gonna be duplicates.
         */
        if (current->ptrace)
                do_notify_parent_cldstop(current, true, why);
        if (gstop_done && (!current->ptrace || ptrace_reparented(current)))
                do_notify_parent_cldstop(current, false, why);

        /*
         * 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++;

                t = current;
                while_each_thread(current, t) {
                        /*
                         * Setting state to TASK_STOPPED for a group
                         * stop is always done with the siglock held,
                         * so this check has no races.
                         */
                        if (!task_is_stopped(t) &&
                            task_set_jobctl_pending(t, signr | gstop)) {
                                sig->group_stop_count++;
                                if (likely(!(t->ptrace & PT_SEIZED)))
                                        signal_wake_up(t, 0);
                                else
                                        ptrace_trap_notify(t);
                        }
                }
        }

        if (likely(!current->ptrace)) {
                int notify = 0;

                /*
                 * If there are no other threads in the group, or if there
                 * is a group stop in progress and we are the last to stop,
                 * report to the parent.
                 */
                if (task_participate_group_stop(current))
                        notify = CLD_STOPPED;

                current->jobctl |= JOBCTL_STOPPED;
                set_special_state(TASK_STOPPED);
                spin_unlock_irq(&current->sighand->siglock);

                /*
                 * Notify the parent of the group stop completion.  Because
                 * we're not holding either the siglock or tasklist_lock
                 * here, ptracer may attach inbetween; however, this is for
                 * group stop and should always be delivered to the real
                 * parent of the group leader.  The new ptracer will get
                 * its notification when this task transitions into
                 * TASK_TRACED.
                 */
                if (notify) {
                        read_lock(&tasklist_lock);
                        do_notify_parent_cldstop(current, false, notify);
                        read_unlock(&tasklist_lock);
                }

                /* Now we don't run again until woken by SIGCONT or SIGKILL */
                cgroup_enter_frozen();
                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();
}

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) {
                        clear_siginfo(&ksig->info);
                        ksig->info.si_signo = signr = SIGKILL;
                        sigdelset(&current->pending.signal, SIGKILL);
                        trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
                                &sighand->action[SIGKILL - 1]);
                        recalc_sigpending();
                        goto fatal;
                }

                if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
                    do_signal_stop(0))
                        goto relock;

                if (unlikely(current->jobctl &
                             (JOBCTL_TRAP_MASK | JOBCTL_TRAP_FREEZE))) {
                        if (current->jobctl & JOBCTL_TRAP_MASK) {
                                do_jobctl_trap();
                                spin_unlock_irq(&sighand->siglock);
                        } else if (current->jobctl & JOBCTL_TRAP_FREEZE)
                                do_freezer_trap();

                        goto relock;
                }

                /*
                 * If the task is leaving the frozen state, let's update
                 * cgroup counters and reset the frozen bit.
                 */
                if (unlikely(cgroup_task_frozen(current))) {
                        spin_unlock_irq(&sighand->siglock);
                        cgroup_leave_frozen(false);
                        goto relock;
                }

                /*
                 * Signals generated by the execution of an instruction
                 * need to be delivered before any other pending signals
                 * so that the instruction pointer in the signal stack
                 * frame points to the faulting instruction.
                 */
                type = PIDTYPE_PID;
                signr = dequeue_synchronous_signal(&ksig->info);
                if (!signr)
                        signr = dequeue_signal(current, &current->blocked,
                                               &ksig->info, &type);

                if (!signr)
                        break; /* will return 0 */

                if (unlikely(current->ptrace) && (signr != SIGKILL) &&
                    !(sighand->action[signr -1].sa.sa_flags & SA_IMMUTABLE)) {
                        signr = ptrace_signal(signr, &ksig->info, type);
                        if (!signr)
                                continue;
                }

                ka = &sighand->action[signr-1];

                /* Trace actually delivered signals. */
                trace_signal_deliver(signr, &ksig->info, ka);

                if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
                        continue;
                if (ka->sa.sa_handler != SIG_DFL) {
                        /* Run the handler.  */
                        ksig->ka = *ka;

                        if (ka->sa.sa_flags & SA_ONESHOT)
                                ka->sa.sa_handler = SIG_DFL;

                        break; /* will return non-zero "signr" value */
                }

                /*
                 * Now we are doing the default action for this signal.
                 */
                if (sig_kernel_ignore(signr)) /* Default is nothing. */
                        continue;

                /*
                 * Global init gets no signals it doesn't want.
                 * Container-init gets no signals it doesn't want from same
                 * container.
                 *
                 * Note that if global/container-init sees a sig_kernel_only()
                 * signal here, the signal must have been generated internally
                 * or must have come from an ancestor namespace. In either
                 * case, the signal cannot be dropped.
                 */
                if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
                                !sig_kernel_only(signr))
                        continue;

                if (sig_kernel_stop(signr)) {
                        /*
                         * The default action is to stop all threads in
                         * the thread group.  The job control signals
                         * do nothing in an orphaned pgrp, but SIGSTOP
                         * always works.  Note that siglock needs to be
                         * dropped during the call to is_orphaned_pgrp()
                         * because of lock ordering with tasklist_lock.
                         * This allows an intervening SIGCONT to be posted.
                         * We need to check for that and bail out if necessary.
                         */
                        if (signr != SIGSTOP) {
                                spin_unlock_irq(&sighand->siglock);

                                /* signals can be posted during this window */

                                if (is_current_pgrp_orphaned())
                                        goto relock;

                                spin_lock_irq(&sighand->siglock);
                        }

                        if (likely(do_signal_stop(ksig->info.si_signo))) {
                                /* It released the siglock.  */
                                goto relock;
                        }

                        /*
                         * We didn't actually stop, due to a race
                         * with SIGCONT or something like that.
                         */
                        continue;
                }

        fatal:
                spin_unlock_irq(&sighand->siglock);
                if (unlikely(cgroup_task_frozen(current)))
                        cgroup_leave_frozen(true);

                /*
                 * Anything else is fatal, maybe with a core dump.
                 */
                current->flags |= PF_SIGNALED;

                if (sig_kernel_coredump(signr)) {
                        if (print_fatal_signals)
                                print_fatal_signal(ksig->info.si_signo);
                        proc_coredump_connector(current);
                        /*
                         * If it was able to dump core, this kills all
                         * other threads in the group and synchronizes with
                         * their demise.  If we lost the race with another
                         * thread getting here, it set group_exit_code
                         * first and our do_group_exit call below will use
                         * that value and ignore the one we pass it.
                         */
                        do_coredump(&ksig->info);
                }

                /*
                 * PF_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.
                 */
                if (current->flags & PF_USER_WORKER)
                        goto out;

                /*
                 * Death signals, no core dump.
                 */
                do_group_exit(ksig->info.si_signo);
                /* NOTREACHED */
        }
        spin_unlock_irq(&sighand->siglock);
out:
        ksig->sig = signr;

        if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
                hide_si_addr_tag_bits(ksig);

        return ksig->sig > 0;
}

/**
 * signal_delivered - called after signal delivery to update blocked signals
 * @ksig:               kernel signal struct
 * @stepping:           nonzero if debugger single-step or block-step in use
 *
 * This function should be called when a signal has successfully been
 * delivered. It updates the blocked signals accordingly (@ksig->ka.sa.sa_mask
 * is always blocked), and the signal itself is blocked unless %SA_NODEFER
 * is set in @ksig->ka.sa.sa_flags.  Tracing is notified.
 */
static void signal_delivered(struct ksignal *ksig, int stepping)
{
        sigset_t blocked;

        /* A signal was successfully delivered, and the
           saved sigmask was stored on the signal frame,
           and will be restored by sigreturn.  So we can
           simply clear the restore sigmask flag.  */
        clear_restore_sigmask();

        sigorsets(&blocked, &current->blocked, &ksig->ka.sa.sa_mask);
        if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
                sigaddset(&blocked, ksig->sig);
        set_current_blocked(&blocked);
        if (current->sas_ss_flags & SS_AUTODISARM)
                sas_ss_reset(current);
        if (stepping)
                ptrace_notify(SIGTRAP, 0);
}

void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
{
        if (failed)
                force_sigsegv(ksig->sig);
        else
                signal_delivered(ksig, stepping);
}

/*
 * It could be that complete_signal() picked us to notify about the
 * group-wide signal. Other threads should be notified now to take
 * the shared signals in @which since we will not.
 */
static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
{
        sigset_t retarget;
        struct task_struct *t;

        sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
        if (sigisemptyset(&retarget))
                return;

        t = tsk;
        while_each_thread(tsk, t) {
                if (t->flags & PF_EXITING)
                        continue;

                if (!has_pending_signals(&retarget, &t->blocked))
                        continue;
                /* Remove the signals this thread can handle. */
                sigandsets(&retarget, &retarget, &t->blocked);

                if (!task_sigpending(t))
                        signal_wake_up(t, 0);

                if (sigisemptyset(&retarget))
                        break;
        }
}

void exit_signals(struct task_struct *tsk)
{
        int group_stop = 0;
        sigset_t unblocked;

        /*
         * @tsk is about to have PF_EXITING set - lock out users which
         * expect stable threadgroup.
         */
        cgroup_threadgroup_change_begin(tsk);

        if (thread_group_empty(tsk) || (tsk->signal->flags & SIGNAL_GROUP_EXIT)) {
                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 inline void prepare_kill_siginfo(int sig, struct kernel_siginfo *info)
{
        clear_siginfo(info);
        info->si_signo = sig;
        info->si_errno = 0;
        info->si_code = SI_USER;
        info->si_pid = task_tgid_vnr(current);
        info->si_uid = from_kuid_munged(current_user_ns(), current_uid());
}

/**
 *  sys_kill - send a signal to a process
 *  @pid: the PID of the process
 *  @sig: signal to be sent
 */
SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
{
        struct kernel_siginfo info;

        prepare_kill_siginfo(sig, &info);

        return kill_something_info(sig, &info, pid);
}

/*
 * Verify that the signaler and signalee either are in the same pid namespace
 * or that the signaler's pid namespace is an ancestor of the signalee's pid
 * namespace.
 */
static bool access_pidfd_pidns(struct pid *pid)
{
        struct pid_namespace *active = task_active_pid_ns(current);
        struct pid_namespace *p = ns_of_pid(pid);

        for (;;) {
                if (!p)
                        return false;
                if (p == active)
                        break;
                p = p->parent;
        }

        return true;
}

static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo,
                siginfo_t __user *info)
{
#ifdef CONFIG_COMPAT
        /*
         * Avoid hooking up compat syscalls and instead handle necessary
         * conversions here. Note, this is a stop-gap measure and should not be
         * considered a generic solution.
         */
        if (in_compat_syscall())
                return copy_siginfo_from_user32(
                        kinfo, (struct compat_siginfo __user *)info);
#endif
        return copy_siginfo_from_user(kinfo, info);
}

static struct pid *pidfd_to_pid(const struct file *file)
{
        struct pid *pid;

        pid = pidfd_pid(file);
        if (!IS_ERR(pid))
                return pid;

        return tgid_pidfd_to_pid(file);
}

/**
 * sys_pidfd_send_signal - Signal a process through a pidfd
 * @pidfd:  file descriptor of the process
 * @sig:    signal to send
 * @info:   signal info
 * @flags:  future flags
 *
 * The syscall currently only signals via PIDTYPE_PID which covers
 * kill(<positive-pid>, <signal>. It does not signal threads or process
 * groups.
 * In order to extend the syscall to threads and process groups the @flags
 * argument should be used. In essence, the @flags argument will determine
 * what is signaled and not the file descriptor itself. Put in other words,
 * grouping is a property of the flags argument not a property of the file
 * descriptor.
 *
 * Return: 0 on success, negative errno on failure
 */
SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
                siginfo_t __user *, info, unsigned int, flags)
{
        int ret;
        struct fd f;
        struct pid *pid;
        kernel_siginfo_t kinfo;

        /* Enforce flags be set to 0 until we add an extension. */
        if (flags)
                return -EINVAL;

        f = fdget(pidfd);
        if (!f.file)
                return -EBADF;

        /* Is this a pidfd? */
        pid = pidfd_to_pid(f.file);
        if (IS_ERR(pid)) {
                ret = PTR_ERR(pid);
                goto err;
        }

        ret = -EINVAL;
        if (!access_pidfd_pidns(pid))
                goto err;

        if (info) {
                ret = copy_siginfo_from_user_any(&kinfo, info);
                if (unlikely(ret))
                        goto err;

                ret = -EINVAL;
                if (unlikely(sig != kinfo.si_signo))
                        goto err;

                /* Only allow sending arbitrary signals to yourself. */
                ret = -EPERM;
                if ((task_pid(current) != pid) &&
                    (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL))
                        goto err;
        } else {
                prepare_kill_siginfo(sig, &kinfo);
        }

        ret = kill_pid_info(sig, &kinfo, pid);

err:
        fdput(f);
        return ret;
}

static int
do_send_specific(pid_t tgid, pid_t pid, int sig, struct kernel_siginfo *info)
{
        struct task_struct *p;
        int error = -ESRCH;

        rcu_read_lock();
        p = find_task_by_vpid(pid);
        if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
                error = check_kill_permission(sig, info, p);
                /*
                 * The null signal is a permissions and process existence
                 * probe.  No signal is actually delivered.
                 */
                if (!error && sig) {
                        error = do_send_sig_info(sig, info, p, PIDTYPE_PID);
                        /*
                         * If lock_task_sighand() failed we pretend the task
                         * dies after receiving the signal. The window is tiny,
                         * and the signal is private anyway.
                         */
                        if (unlikely(error == -ESRCH))
                                error = 0;
                }
        }
        rcu_read_unlock();

        return error;
}

static int do_tkill(pid_t tgid, pid_t pid, int sig)
{
        struct kernel_siginfo info;

        clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        info.si_code = SI_TKILL;
        info.si_pid = task_tgid_vnr(current);
        info.si_uid = from_kuid_munged(current_user_ns(), current_uid());

        return do_send_specific(tgid, pid, sig, &info);
}

/**
 *  sys_tgkill - send signal to one specific thread
 *  @tgid: the thread group ID of the thread
 *  @pid: the PID of the thread
 *  @sig: signal to be sent
 *
 *  This syscall also checks the @tgid and returns -ESRCH even if the PID
 *  exists but it's not belonging to the target process anymore. This
 *  method solves the problem of threads exiting and PIDs getting reused.
 */
SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
{
        /* This is only valid for single tasks */
        if (pid <= 0 || tgid <= 0)
                return -EINVAL;

        return do_tkill(tgid, pid, sig);
}

/**
 *  sys_tkill - send signal to one specific task
 *  @pid: the PID of the task
 *  @sig: signal to be sent
 *
 *  Send a signal to only one task, even if it's a CLONE_THREAD task.
 */
SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
{
        /* This is only valid for single tasks */
        if (pid <= 0)
                return -EINVAL;

        return do_tkill(0, pid, sig);
}

static int do_rt_sigqueueinfo(pid_t pid, int sig, kernel_siginfo_t *info)
{
        /* Not even root can pretend to send signals from the kernel.
         * Nor can they impersonate a kill()/tgkill(), which adds source info.
         */
        if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
            (task_pid_vnr(current) != pid))
                return -EPERM;

        /* POSIX.1b doesn't mention process groups.  */
        return kill_proc_info(sig, info, pid);
}

/**
 *  sys_rt_sigqueueinfo - send signal information to a signal
 *  @pid: the PID of the thread
 *  @sig: signal to be sent
 *  @uinfo: signal info to be sent
 */
SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
                siginfo_t __user *, uinfo)
{
        kernel_siginfo_t info;
        int ret = __copy_siginfo_from_user(sig, &info, uinfo);
        if (unlikely(ret))
                return ret;
        return do_rt_sigqueueinfo(pid, sig, &info);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
                        compat_pid_t, pid,
                        int, sig,
                        struct compat_siginfo __user *, uinfo)
{
        kernel_siginfo_t info;
        int ret = __copy_siginfo_from_user32(sig, &info, uinfo);
        if (unlikely(ret))
                return ret;
        return do_rt_sigqueueinfo(pid, sig, &info);
}
#endif

static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, kernel_siginfo_t *info)
{
        /* This is only valid for single tasks */
        if (pid <= 0 || tgid <= 0)
                return -EINVAL;

        /* Not even root can pretend to send signals from the kernel.
         * Nor can they impersonate a kill()/tgkill(), which adds source info.
         */
        if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
            (task_pid_vnr(current) != pid))
                return -EPERM;

        return do_send_specific(tgid, pid, sig, info);
}

SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
                siginfo_t __user *, uinfo)
{
        kernel_siginfo_t info;
        int ret = __copy_siginfo_from_user(sig, &info, uinfo);
        if (unlikely(ret))
                return ret;
        return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
                        compat_pid_t, tgid,
                        compat_pid_t, pid,
                        int, sig,
                        struct compat_siginfo __user *, uinfo)
{
        kernel_siginfo_t info;
        int ret = __copy_siginfo_from_user32(sig, &info, uinfo);
        if (unlikely(ret))
                return ret;
        return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
}
#endif

/*
 * For kthreads only, must not be used if cloned with CLONE_SIGHAND
 */
void kernel_sigaction(int sig, __sighandler_t action)
{
        spin_lock_irq(&current->sighand->siglock);
        current->sighand->action[sig - 1].sa.sa_handler = action;
        if (action == SIG_IGN) {
                sigset_t mask;

                sigemptyset(&mask);
                sigaddset(&mask, sig);

                flush_sigqueue_mask(&mask, &current->signal->shared_pending);
                flush_sigqueue_mask(&mask, &current->pending);
                recalc_sigpending();
        }
        spin_unlock_irq(&current->sighand->siglock);
}
EXPORT_SYMBOL(kernel_sigaction);

void __weak sigaction_compat_abi(struct k_sigaction *act,
                struct k_sigaction *oact)
{
}

int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
{
        struct task_struct *p = current, *t;
        struct k_sigaction *k;
        sigset_t mask;

        if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
                return -EINVAL;

        k = &p->sighand->action[sig-1];

        spin_lock_irq(&p->sighand->siglock);
        if (k->sa.sa_flags & SA_IMMUTABLE) {
                spin_unlock_irq(&p->sighand->siglock);
                return -EINVAL;
        }
        if (oact)
                *oact = *k;

        /*
         * Make sure that we never accidentally claim to support SA_UNSUPPORTED,
         * e.g. by having an architecture use the bit in their uapi.
         */
        BUILD_BUG_ON(UAPI_SA_FLAGS & SA_UNSUPPORTED);

        /*
         * Clear unknown flag bits in order to allow userspace to detect missing
         * support for flag bits and to allow the kernel to use non-uapi bits
         * internally.
         */
        if (act)
                act->sa.sa_flags &= UAPI_SA_FLAGS;
        if (oact)
                oact->sa.sa_flags &= UAPI_SA_FLAGS;

        sigaction_compat_abi(act, oact);

        if (act) {
                sigdelsetmask(&act->sa.sa_mask,
                              sigmask(SIGKILL) | sigmask(SIGSTOP));
                *k = *act;
                /*
                 * POSIX 3.3.1.3:
                 *  "Setting a signal action to SIG_IGN for a signal that is
                 *   pending shall cause the pending signal to be discarded,
                 *   whether or not it is blocked."
                 *
                 *  "Setting a signal action to SIG_DFL for a signal that is
                 *   pending and whose default action is to ignore the signal
                 *   (for example, SIGCHLD), shall cause the pending signal to
                 *   be discarded, whether or not it is blocked"
                 */
                if (sig_handler_ignored(sig_handler(p, sig), sig)) {
                        sigemptyset(&mask);
                        sigaddset(&mask, sig);
                        flush_sigqueue_mask(&mask, &p->signal->shared_pending);
                        for_each_thread(p, t)
                                flush_sigqueue_mask(&mask, &t->pending);
                }
        }

        spin_unlock_irq(&p->sighand->siglock);
        return 0;
}

#ifdef CONFIG_DYNAMIC_SIGFRAME
static inline void sigaltstack_lock(void)
        __acquires(&current->sighand->siglock)
{
        spin_lock_irq(&current->sighand->siglock);
}

static inline void sigaltstack_unlock(void)
        __releases(&current->sighand->siglock)
{
        spin_unlock_irq(&current->sighand->siglock);
}
#else
static inline void sigaltstack_lock(void) { }
static inline void sigaltstack_unlock(void) { }
#endif

static int
do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp,
                size_t min_ss_size)
{
        struct task_struct *t = current;
        int ret = 0;

        if (oss) {
                memset(oss, 0, sizeof(stack_t));
                oss->ss_sp = (void __user *) t->sas_ss_sp;
                oss->ss_size = t->sas_ss_size;
                oss->ss_flags = sas_ss_flags(sp) |
                        (current->sas_ss_flags & SS_FLAG_BITS);
        }

        if (ss) {
                void __user *ss_sp = ss->ss_sp;
                size_t ss_size = ss->ss_size;
                unsigned ss_flags = ss->ss_flags;
                int ss_mode;

                if (unlikely(on_sig_stack(sp)))
                        return -EPERM;

                ss_mode = ss_flags & ~SS_FLAG_BITS;
                if (unlikely(ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
                                ss_mode != 0))
                        return -EINVAL;

                /*
                 * Return before taking any locks if no actual
                 * sigaltstack changes were requested.
                 */
                if (t->sas_ss_sp == (unsigned long)ss_sp &&
                    t->sas_ss_size == ss_size &&
                    t->sas_ss_flags == ss_flags)
                        return 0;

                sigaltstack_lock();
                if (ss_mode == SS_DISABLE) {
                        ss_size = 0;
                        ss_sp = NULL;
                } else {
                        if (unlikely(ss_size < min_ss_size))
                                ret = -ENOMEM;
                        if (!sigaltstack_size_valid(ss_size))
                                ret = -ENOMEM;
                }
                if (!ret) {
                        t->sas_ss_sp = (unsigned long) ss_sp;
                        t->sas_ss_size = ss_size;
                        t->sas_ss_flags = ss_flags;
                }
                sigaltstack_unlock();
        }
        return ret;
}

SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)
{
        stack_t new, old;
        int err;
        if (uss && copy_from_user(&new, uss, sizeof(stack_t)))
                return -EFAULT;
        err = do_sigaltstack(uss ? &new : NULL, uoss ? &old : NULL,
                              current_user_stack_pointer(),
                              MINSIGSTKSZ);
        if (!err && uoss && copy_to_user(uoss, &old, sizeof(stack_t)))
                err = -EFAULT;
        return err;
}

int restore_altstack(const stack_t __user *uss)
{
        stack_t new;
        if (copy_from_user(&new, uss, sizeof(stack_t)))
                return -EFAULT;
        (void)do_sigaltstack(&new, NULL, current_user_stack_pointer(),
                             MINSIGSTKSZ);
        /* squash all but EFAULT for now */
        return 0;
}

int __save_altstack(stack_t __user *uss, unsigned long sp)
{
        struct task_struct *t = current;
        int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
                __put_user(t->sas_ss_flags, &uss->ss_flags) |
                __put_user(t->sas_ss_size, &uss->ss_size);
        return err;
}

#ifdef CONFIG_COMPAT
static int do_compat_sigaltstack(const compat_stack_t __user *uss_ptr,
                                 compat_stack_t __user *uoss_ptr)
{
        stack_t uss, uoss;
        int ret;

        if (uss_ptr) {
                compat_stack_t uss32;
                if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
                        return -EFAULT;
                uss.ss_sp = compat_ptr(uss32.ss_sp);
                uss.ss_flags = uss32.ss_flags;
                uss.ss_size = uss32.ss_size;
        }
        ret = do_sigaltstack(uss_ptr ? &uss : NULL, &uoss,
                             compat_user_stack_pointer(),
                             COMPAT_MINSIGSTKSZ);
        if (ret >= 0 && uoss_ptr)  {
                compat_stack_t old;
                memset(&old, 0, sizeof(old));
                old.ss_sp = ptr_to_compat(uoss.ss_sp);
                old.ss_flags = uoss.ss_flags;
                old.ss_size = uoss.ss_size;
                if (copy_to_user(uoss_ptr, &old, sizeof(compat_stack_t)))
                        ret = -EFAULT;
        }
        return ret;
}

COMPAT_SYSCALL_DEFINE2(sigaltstack,
                        const compat_stack_t __user *, uss_ptr,
                        compat_stack_t __user *, uoss_ptr)
{
        return do_compat_sigaltstack(uss_ptr, uoss_ptr);
}

int compat_restore_altstack(const compat_stack_t __user *uss)
{
        int err = do_compat_sigaltstack(uss, NULL);
        /* squash all but -EFAULT for now */
        return err == -EFAULT ? err : 0;
}

int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
{
        int err;
        struct task_struct *t = current;
        err = __put_user(ptr_to_compat((void __user *)t->sas_ss_sp),
                         &uss->ss_sp) |
                __put_user(t->sas_ss_flags, &uss->ss_flags) |
                __put_user(t->sas_ss_size, &uss->ss_size);
        return err;
}
#endif

#ifdef __ARCH_WANT_SYS_SIGPENDING

/**
 *  sys_sigpending - examine pending signals
 *  @uset: where mask of pending signal is returned
 */
SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, uset)
{
        sigset_t set;

        if (sizeof(old_sigset_t) > sizeof(*uset))
                return -EINVAL;

        do_sigpending(&set);

        if (copy_to_user(uset, &set, sizeof(old_sigset_t)))
                return -EFAULT;

        return 0;
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE1(sigpending, compat_old_sigset_t __user *, set32)
{
        sigset_t set;

        do_sigpending(&set);

        return put_user(set.sig[0], set32);
}
#endif

#endif

#ifdef __ARCH_WANT_SYS_SIGPROCMASK
/**
 *  sys_sigprocmask - examine and change blocked signals
 *  @how: whether to add, remove, or set signals
 *  @nset: signals to add or remove (if non-null)
 *  @oset: previous value of signal mask if non-null
 *
 * Some platforms have their own version with special arguments;
 * others support only sys_rt_sigprocmask.
 */

SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
                old_sigset_t __user *, oset)
{
        old_sigset_t old_set, new_set;
        sigset_t new_blocked;

        old_set = current->blocked.sig[0];

        if (nset) {
                if (copy_from_user(&new_set, nset, sizeof(*nset)))
                        return -EFAULT;

                new_blocked = current->blocked;

                switch (how) {
                case SIG_BLOCK:
                        sigaddsetmask(&new_blocked, new_set);
                        break;
                case SIG_UNBLOCK:
                        sigdelsetmask(&new_blocked, new_set);
                        break;
                case SIG_SETMASK:
                        new_blocked.sig[0] = new_set;
                        break;
                default:
                        return -EINVAL;
                }

                set_current_blocked(&new_blocked);
        }

        if (oset) {
                if (copy_to_user(oset, &old_set, sizeof(*oset)))
                        return -EFAULT;
        }

        return 0;
}
#endif /* __ARCH_WANT_SYS_SIGPROCMASK */

#ifndef CONFIG_ODD_RT_SIGACTION
/**
 *  sys_rt_sigaction - alter an action taken by a process
 *  @sig: signal to be sent
 *  @act: new sigaction
 *  @oact: used to save the previous sigaction
 *  @sigsetsize: size of sigset_t type
 */
SYSCALL_DEFINE4(rt_sigaction, int, sig,
                const struct sigaction __user *, act,
                struct sigaction __user *, oact,
                size_t, sigsetsize)
{
        struct k_sigaction new_sa, old_sa;
        int ret;

        /* XXX: Don't preclude handling different sized sigset_t's.  */
        if (sigsetsize != sizeof(sigset_t))
                return -EINVAL;

        if (act && copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
                return -EFAULT;

        ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
        if (ret)
                return ret;

        if (oact && copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
                return -EFAULT;

        return 0;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
                const struct compat_sigaction __user *, act,
                struct compat_sigaction __user *, oact,
                compat_size_t, sigsetsize)
{
        struct k_sigaction new_ka, old_ka;
#ifdef __ARCH_HAS_SA_RESTORER
        compat_uptr_t restorer;
#endif
        int ret;

        /* XXX: Don't preclude handling different sized sigset_t's.  */
        if (sigsetsize != sizeof(compat_sigset_t))
                return -EINVAL;

        if (act) {
                compat_uptr_t handler;
                ret = get_user(handler, &act->sa_handler);
                new_ka.sa.sa_handler = compat_ptr(handler);
#ifdef __ARCH_HAS_SA_RESTORER
                ret |= get_user(restorer, &act->sa_restorer);
                new_ka.sa.sa_restorer = compat_ptr(restorer);
#endif
                ret |= get_compat_sigset(&new_ka.sa.sa_mask, &act->sa_mask);
                ret |= get_user(new_ka.sa.sa_flags, &act->sa_flags);
                if (ret)
                        return -EFAULT;
        }

        ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
        if (!ret && oact) {
                ret = put_user(ptr_to_compat(old_ka.sa.sa_handler), 
                               &oact->sa_handler);
                ret |= put_compat_sigset(&oact->sa_mask, &old_ka.sa.sa_mask,
                                         sizeof(oact->sa_mask));
                ret |= put_user(old_ka.sa.sa_flags, &oact->sa_flags);
#ifdef __ARCH_HAS_SA_RESTORER
                ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer),
                                &oact->sa_restorer);
#endif
        }
        return ret;
}
#endif
#endif /* !CONFIG_ODD_RT_SIGACTION */

#ifdef CONFIG_OLD_SIGACTION
SYSCALL_DEFINE3(sigaction, int, sig,
                const struct old_sigaction __user *, act,
                struct old_sigaction __user *, oact)
{
        struct k_sigaction new_ka, old_ka;
        int ret;

        if (act) {
                old_sigset_t mask;
                if (!access_ok(act, sizeof(*act)) ||
                    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
                    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
                    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
                    __get_user(mask, &act->sa_mask))
                        return -EFAULT;
#ifdef __ARCH_HAS_KA_RESTORER
                new_ka.ka_restorer = NULL;
#endif
                siginitset(&new_ka.sa.sa_mask, mask);
        }

        ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

        if (!ret && oact) {
                if (!access_ok(oact, sizeof(*oact)) ||
                    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
                    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
                    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
                    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
                        return -EFAULT;
        }

        return ret;
}
#endif
#ifdef CONFIG_COMPAT_OLD_SIGACTION
COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
                const struct compat_old_sigaction __user *, act,
                struct compat_old_sigaction __user *, oact)
{
        struct k_sigaction new_ka, old_ka;
        int ret;
        compat_old_sigset_t mask;
        compat_uptr_t handler, restorer;

        if (act) {
                if (!access_ok(act, sizeof(*act)) ||
                    __get_user(handler, &act->sa_handler) ||
                    __get_user(restorer, &act->sa_restorer) ||
                    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
                    __get_user(mask, &act->sa_mask))
                        return -EFAULT;

#ifdef __ARCH_HAS_KA_RESTORER
                new_ka.ka_restorer = NULL;
#endif
                new_ka.sa.sa_handler = compat_ptr(handler);
                new_ka.sa.sa_restorer = compat_ptr(restorer);
                siginitset(&new_ka.sa.sa_mask, mask);
        }

        ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

        if (!ret && oact) {
                if (!access_ok(oact, sizeof(*oact)) ||
                    __put_user(ptr_to_compat(old_ka.sa.sa_handler),
                               &oact->sa_handler) ||
                    __put_user(ptr_to_compat(old_ka.sa.sa_restorer),
                               &oact->sa_restorer) ||
                    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
                    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
                        return -EFAULT;
        }
        return ret;
}
#endif

#ifdef CONFIG_SGETMASK_SYSCALL

/*
 * For backwards compatibility.  Functionality superseded by sigprocmask.
 */
SYSCALL_DEFINE0(sgetmask)
{
        /* SMP safe */
        return current->blocked.sig[0];
}

SYSCALL_DEFINE1(ssetmask, int, newmask)
{
        int old = current->blocked.sig[0];
        sigset_t newset;

        siginitset(&newset, newmask);
        set_current_blocked(&newset);

        return old;
}
#endif /* CONFIG_SGETMASK_SYSCALL */

#ifdef __ARCH_WANT_SYS_SIGNAL
/*
 * For backwards compatibility.  Functionality superseded by sigaction.
 */
SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
{
        struct k_sigaction new_sa, old_sa;
        int ret;

        new_sa.sa.sa_handler = handler;
        new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
        sigemptyset(&new_sa.sa.sa_mask);

        ret = do_sigaction(sig, &new_sa, &old_sa);

        return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
}
#endif /* __ARCH_WANT_SYS_SIGNAL */

#ifdef __ARCH_WANT_SYS_PAUSE

SYSCALL_DEFINE0(pause)
{
        while (!signal_pending(current)) {
                __set_current_state(TASK_INTERRUPTIBLE);
                schedule();
        }
        return -ERESTARTNOHAND;
}

#endif

static int sigsuspend(sigset_t *set)
{
        current->saved_sigmask = current->blocked;
        set_current_blocked(set);

        while (!signal_pending(current)) {
                __set_current_state(TASK_INTERRUPTIBLE);
                schedule();
        }
        set_restore_sigmask();
        return -ERESTARTNOHAND;
}

/**
 *  sys_rt_sigsuspend - replace the signal mask for a value with the
 *      @unewset value until a signal is received
 *  @unewset: new signal mask value
 *  @sigsetsize: size of sigset_t type
 */
SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
{
        sigset_t newset;

        /* XXX: Don't preclude handling different sized sigset_t's.  */
        if (sigsetsize != sizeof(sigset_t))
                return -EINVAL;

        if (copy_from_user(&newset, unewset, sizeof(newset)))
                return -EFAULT;
        return sigsuspend(&newset);
}
 
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(rt_sigsuspend, compat_sigset_t __user *, unewset, compat_size_t, sigsetsize)
{
        sigset_t newset;

        /* XXX: Don't preclude handling different sized sigset_t's.  */
        if (sigsetsize != sizeof(sigset_t))
                return -EINVAL;

        if (get_compat_sigset(&newset, unewset))
                return -EFAULT;
        return sigsuspend(&newset);
}
#endif

#ifdef CONFIG_OLD_SIGSUSPEND
SYSCALL_DEFINE1(sigsuspend, old_sigset_t, mask)
{
        sigset_t blocked;
        siginitset(&blocked, mask);
        return sigsuspend(&blocked);
}
#endif
#ifdef CONFIG_OLD_SIGSUSPEND3
SYSCALL_DEFINE3(sigsuspend, int, unused1, int, unused2, old_sigset_t, mask)
{
        sigset_t blocked;
        siginitset(&blocked, mask);
        return sigsuspend(&blocked);
}
#endif

__weak const char *arch_vma_name(struct vm_area_struct *vma)
{
        return NULL;
}

static inline void siginfo_buildtime_checks(void)
{
        BUILD_BUG_ON(sizeof(struct siginfo) != SI_MAX_SIZE);

        /* Verify the offsets in the two siginfos match */
#define CHECK_OFFSET(field) \
        BUILD_BUG_ON(offsetof(siginfo_t, field) != offsetof(kernel_siginfo_t, field))

        /* kill */
        CHECK_OFFSET(si_pid);
        CHECK_OFFSET(si_uid);

        /* timer */
        CHECK_OFFSET(si_tid);
        CHECK_OFFSET(si_overrun);
        CHECK_OFFSET(si_value);

        /* rt */
        CHECK_OFFSET(si_pid);
        CHECK_OFFSET(si_uid);
        CHECK_OFFSET(si_value);

        /* sigchld */
        CHECK_OFFSET(si_pid);
        CHECK_OFFSET(si_uid);
        CHECK_OFFSET(si_status);
        CHECK_OFFSET(si_utime);
        CHECK_OFFSET(si_stime);

        /* sigfault */
        CHECK_OFFSET(si_addr);
        CHECK_OFFSET(si_trapno);
        CHECK_OFFSET(si_addr_lsb);
        CHECK_OFFSET(si_lower);
        CHECK_OFFSET(si_upper);
        CHECK_OFFSET(si_pkey);
        CHECK_OFFSET(si_perf_data);
        CHECK_OFFSET(si_perf_type);
        CHECK_OFFSET(si_perf_flags);

        /* sigpoll */
        CHECK_OFFSET(si_band);
        CHECK_OFFSET(si_fd);

        /* sigsys */
        CHECK_OFFSET(si_call_addr);
        CHECK_OFFSET(si_syscall);
        CHECK_OFFSET(si_arch);
#undef CHECK_OFFSET

        /* usb asyncio */
        BUILD_BUG_ON(offsetof(struct siginfo, si_pid) !=
                     offsetof(struct siginfo, si_addr));
        if (sizeof(int) == sizeof(void __user *)) {
                BUILD_BUG_ON(sizeof_field(struct siginfo, si_pid) !=
                             sizeof(void __user *));
        } else {
                BUILD_BUG_ON((sizeof_field(struct siginfo, si_pid) +
                              sizeof_field(struct siginfo, si_uid)) !=
                             sizeof(void __user *));
                BUILD_BUG_ON(offsetofend(struct siginfo, si_pid) !=
                             offsetof(struct siginfo, si_uid));
        }
#ifdef CONFIG_COMPAT
        BUILD_BUG_ON(offsetof(struct compat_siginfo, si_pid) !=
                     offsetof(struct compat_siginfo, si_addr));
        BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
                     sizeof(compat_uptr_t));
        BUILD_BUG_ON(sizeof_field(struct compat_siginfo, si_pid) !=
                     sizeof_field(struct siginfo, si_pid));
#endif
}

#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 */