linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 *  fs/signalfd.c

 *

 *  Copyright (C) 2003  Linus Torvalds

 *

 *  Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>

 *      Changed ->read() to return a siginfo strcture instead of signal number.

 *      Fixed locking in ->poll().

 *      Added sighand-detach notification.

 *      Added fd re-use in sys_signalfd() syscall.

 *      Now using anonymous inode source.

 *      Thanks to Oleg Nesterov for useful code review and suggestions.

 *      More comments and suggestions from Arnd Bergmann.

 *  Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>

 *      Retrieve multiple signals with one read() call

 *  Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>

 *      Attach to the sighand only during read() and poll().

 */

​

#include <linux/file.h>

#include <linux/poll.h>

#include <linux/init.h>

#include <linux/fs.h>

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/kernel.h>

#include <linux/signal.h>

#include <linux/list.h>

#include <linux/anon_inodes.h>

#include <linux/signalfd.h>

#include <linux/syscalls.h>

#include <linux/proc_fs.h>

#include <linux/compat.h>

​

void signalfd_cleanup(struct sighand_struct *sighand)

{

    wait_queue_head_t *wqh = &sighand->signalfd_wqh;

    /*

     * The lockless check can race with remove_wait_queue() in progress,

     * but in this case its caller should run under rcu_read_lock() and

     * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return.

     */

    if (likely(!waitqueue_active(wqh)))

        return;

​

    /* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */

    wake_up_poll(wqh, EPOLLHUP | POLLFREE);

}

​

struct signalfd_ctx {

    sigset_t sigmask;

};

​

static int signalfd_release(struct inode *inode, struct file *file)

{

    kfree(file->private_data);

    return 0;

}

​

static __poll_t signalfd_poll(struct file *file, poll_table *wait)

{

    struct signalfd_ctx *ctx = file->private_data;

    __poll_t events = 0;

​

    poll_wait(file, &current->sighand->signalfd_wqh, wait);

​

    spin_lock_irq(&current->sighand->siglock);

    if (next_signal(&current->pending, &ctx->sigmask) ||

        next_signal(&current->signal->shared_pending,

            &ctx->sigmask))

        events |= EPOLLIN;

    spin_unlock_irq(&current->sighand->siglock);

​

    return events;

}

​

/*

 * Copied from copy_siginfo_to_user() in kernel/signal.c

 */

static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,

                 kernel_siginfo_t const *kinfo)

{

    struct signalfd_siginfo new;

​

    BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);

​

    /*

     * Unused members should be zero ...

     */

    memset(&new, 0, sizeof(new));

​