root/fs/signalfd.c

DEFINITIONS

1. signalfd_release
2. signalfd_poll
3. signalfd_copyinfo
4. signalfd_dequeue
5. signalfd_read
6. sys_signalfd4
7. sys_signalfd

/*
 *  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/kernel.h>
#include <linux/signal.h>
#include <linux/list.h>
#include <linux/anon_inodes.h>
#include <linux/signalfd.h>
#include <linux/syscalls.h>

struct signalfd_ctx {
        sigset_t sigmask;
};

static int signalfd_release(struct inode *inode, struct file *file)
{
        kfree(file->private_data);
        return 0;
}

static unsigned int signalfd_poll(struct file *file, poll_table *wait)
{
        struct signalfd_ctx *ctx = file->private_data;
        unsigned int 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 |= POLLIN;
        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,
                             siginfo_t const *kinfo)
{
        long err;

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

        /*
         * Unused members should be zero ...
         */
        err = __clear_user(uinfo, sizeof(*uinfo));

        /*
         * If you change siginfo_t structure, please be sure
         * this code is fixed accordingly.
         */
        err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
        err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
        err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
        switch (kinfo->si_code & __SI_MASK) {
        case __SI_KILL:
                err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
                err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
                break;
        case __SI_TIMER:
                 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
                 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
                 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
                break;
        case __SI_POLL:
                err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
                err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
                break;
        case __SI_FAULT:
                err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
#ifdef __ARCH_SI_TRAPNO
                err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
#endif
                break;
        case __SI_CHLD:
                err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
                err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
                err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
                err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
                err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
                break;
        case __SI_RT: /* This is not generated by the kernel as of now. */
        case __SI_MESGQ: /* But this is */
                err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
                err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
                err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
                break;
        default:
                /*
                 * This case catches also the signals queued by sigqueue().
                 */
                err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
                err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
                err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
                err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
                break;
        }

        return err ? -EFAULT: sizeof(*uinfo);
}

static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
                                int nonblock)
{
        ssize_t ret;
        DECLARE_WAITQUEUE(wait, current);

        spin_lock_irq(&current->sighand->siglock);
        ret = dequeue_signal(current, &ctx->sigmask, info);
        switch (ret) {
        case 0:
                if (!nonblock)
                        break;
                ret = -EAGAIN;
        default:
                spin_unlock_irq(&current->sighand->siglock);
                return ret;
        }

        add_wait_queue(&current->sighand->signalfd_wqh, &wait);
        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);
                ret = dequeue_signal(current, &ctx->sigmask, info);
                if (ret != 0)
                        break;
                if (signal_pending(current)) {
                        ret = -ERESTARTSYS;
                        break;
                }
                spin_unlock_irq(&current->sighand->siglock);
                schedule();
                spin_lock_irq(&current->sighand->siglock);
        }
        spin_unlock_irq(&current->sighand->siglock);

        remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
        __set_current_state(TASK_RUNNING);

        return ret;
}

/*
 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
 * error code. The "count" parameter must be at least the size of a
 * "struct signalfd_siginfo".
 */
static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
                             loff_t *ppos)
{
        struct signalfd_ctx *ctx = file->private_data;
        struct signalfd_siginfo __user *siginfo;
        int nonblock = file->f_flags & O_NONBLOCK;
        ssize_t ret, total = 0;
        siginfo_t info;

        count /= sizeof(struct signalfd_siginfo);
        if (!count)
                return -EINVAL;

        siginfo = (struct signalfd_siginfo __user *) buf;
        do {
                ret = signalfd_dequeue(ctx, &info, nonblock);
                if (unlikely(ret <= 0))
                        break;
                ret = signalfd_copyinfo(siginfo, &info);
                if (ret < 0)
                        break;
                siginfo++;
                total += ret;
                nonblock = 1;
        } while (--count);

        return total ? total: ret;
}

static const struct file_operations signalfd_fops = {
        .release        = signalfd_release,
        .poll           = signalfd_poll,
        .read           = signalfd_read,
};

asmlinkage long sys_signalfd4(int ufd, sigset_t __user *user_mask,
                              size_t sizemask, int flags)
{
        sigset_t sigmask;
        struct signalfd_ctx *ctx;

        /* Check the SFD_* constants for consistency.  */
        BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
        BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);

        if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
                return -EINVAL;

        if (sizemask != sizeof(sigset_t) ||
            copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
                return -EINVAL;
        sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
        signotset(&sigmask);

        if (ufd == -1) {
                ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
                if (!ctx)
                        return -ENOMEM;

                ctx->sigmask = sigmask;

                /*
                 * When we call this, the initialization must be complete, since
                 * anon_inode_getfd() will install the fd.
                 */
                ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
                                       flags & (O_CLOEXEC | O_NONBLOCK));
                if (ufd < 0)
                        kfree(ctx);
        } else {
                struct file *file = fget(ufd);
                if (!file)
                        return -EBADF;
                ctx = file->private_data;
                if (file->f_op != &signalfd_fops) {
                        fput(file);
                        return -EINVAL;
                }
                spin_lock_irq(&current->sighand->siglock);
                ctx->sigmask = sigmask;
                spin_unlock_irq(&current->sighand->siglock);

                wake_up(&current->sighand->signalfd_wqh);
                fput(file);
        }

        return ufd;
}

asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask,
                             size_t sizemask)
{
        return sys_signalfd4(ufd, user_mask, sizemask, 0);
}