函数源码

Linux Kernel

v5.5.9

Brick Technologies Co., Ltd

Source File:kernel\signal.c Create Date:2022-07-27 10:15:37
首页 Copyright©Brick

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static int __send_signal(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;
 
    assert_spin_locked(&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);
    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;
}