297 lines
8.1 KiB
C
297 lines
8.1 KiB
C
/*
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* fs/signalfd.c
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*
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* Copyright (C) 2003 Linus Torvalds
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*
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* Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
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* Changed ->read() to return a siginfo strcture instead of signal number.
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* Fixed locking in ->poll().
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* Added sighand-detach notification.
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* Added fd re-use in sys_signalfd() syscall.
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* Now using anonymous inode source.
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* Thanks to Oleg Nesterov for useful code review and suggestions.
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* More comments and suggestions from Arnd Bergmann.
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* Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
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* Retrieve multiple signals with one read() call
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* Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
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* Attach to the sighand only during read() and poll().
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*/
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#include <linux/file.h>
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#include <linux/poll.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/kernel.h>
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#include <linux/signal.h>
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#include <linux/list.h>
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#include <linux/anon_inodes.h>
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#include <linux/signalfd.h>
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#include <linux/syscalls.h>
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void signalfd_cleanup(struct sighand_struct *sighand)
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{
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wait_queue_head_t *wqh = &sighand->signalfd_wqh;
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/*
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* The lockless check can race with remove_wait_queue() in progress,
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* but in this case its caller should run under rcu_read_lock() and
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* sighand_cachep is SLAB_DESTROY_BY_RCU, we can safely return.
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*/
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if (likely(!waitqueue_active(wqh)))
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return;
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/* wait_queue_t->func(POLLFREE) should do remove_wait_queue() */
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wake_up_poll(wqh, POLLHUP | POLLFREE);
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}
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struct signalfd_ctx {
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sigset_t sigmask;
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};
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static int signalfd_release(struct inode *inode, struct file *file)
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{
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kfree(file->private_data);
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return 0;
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}
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static unsigned int signalfd_poll(struct file *file, poll_table *wait)
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{
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struct signalfd_ctx *ctx = file->private_data;
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unsigned int events = 0;
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poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
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spin_lock_irq(¤t->sighand->siglock);
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if (next_signal(¤t->pending, &ctx->sigmask) ||
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next_signal(¤t->signal->shared_pending,
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&ctx->sigmask))
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events |= POLLIN;
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spin_unlock_irq(¤t->sighand->siglock);
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return events;
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}
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/*
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* Copied from copy_siginfo_to_user() in kernel/signal.c
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*/
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static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
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siginfo_t const *kinfo)
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{
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long err;
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BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
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/*
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* Unused members should be zero ...
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*/
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err = __clear_user(uinfo, sizeof(*uinfo));
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/*
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* If you change siginfo_t structure, please be sure
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* this code is fixed accordingly.
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*/
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err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
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err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
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err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
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switch (kinfo->si_code & __SI_MASK) {
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case __SI_KILL:
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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break;
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case __SI_TIMER:
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err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
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err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
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err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
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break;
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case __SI_POLL:
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err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
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err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
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break;
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case __SI_FAULT:
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err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
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#ifdef __ARCH_SI_TRAPNO
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err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
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#endif
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#ifdef BUS_MCEERR_AO
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/*
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* Other callers might not initialize the si_lsb field,
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* so check explicitly for the right codes here.
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*/
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if (kinfo->si_code == BUS_MCEERR_AR ||
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kinfo->si_code == BUS_MCEERR_AO)
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err |= __put_user((short) kinfo->si_addr_lsb,
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&uinfo->ssi_addr_lsb);
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#endif
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break;
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case __SI_CHLD:
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
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err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
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err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
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break;
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case __SI_RT: /* This is not generated by the kernel as of now. */
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case __SI_MESGQ: /* But this is */
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
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break;
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default:
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/*
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* This case catches also the signals queued by sigqueue().
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*/
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
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break;
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}
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return err ? -EFAULT: sizeof(*uinfo);
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}
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static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
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int nonblock)
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{
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ssize_t ret;
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DECLARE_WAITQUEUE(wait, current);
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spin_lock_irq(¤t->sighand->siglock);
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ret = dequeue_signal(current, &ctx->sigmask, info);
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switch (ret) {
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case 0:
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if (!nonblock)
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break;
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ret = -EAGAIN;
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default:
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spin_unlock_irq(¤t->sighand->siglock);
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return ret;
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}
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add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
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for (;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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ret = dequeue_signal(current, &ctx->sigmask, info);
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if (ret != 0)
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break;
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if (signal_pending(current)) {
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ret = -ERESTARTSYS;
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break;
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}
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spin_unlock_irq(¤t->sighand->siglock);
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schedule();
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spin_lock_irq(¤t->sighand->siglock);
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}
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spin_unlock_irq(¤t->sighand->siglock);
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remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
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__set_current_state(TASK_RUNNING);
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return ret;
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}
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/*
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* Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
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* error code. The "count" parameter must be at least the size of a
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* "struct signalfd_siginfo".
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*/
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static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
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loff_t *ppos)
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{
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struct signalfd_ctx *ctx = file->private_data;
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struct signalfd_siginfo __user *siginfo;
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int nonblock = file->f_flags & O_NONBLOCK;
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ssize_t ret, total = 0;
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siginfo_t info;
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count /= sizeof(struct signalfd_siginfo);
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if (!count)
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return -EINVAL;
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siginfo = (struct signalfd_siginfo __user *) buf;
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do {
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ret = signalfd_dequeue(ctx, &info, nonblock);
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if (unlikely(ret <= 0))
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break;
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ret = signalfd_copyinfo(siginfo, &info);
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if (ret < 0)
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break;
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siginfo++;
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total += ret;
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nonblock = 1;
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} while (--count);
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return total ? total: ret;
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}
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static const struct file_operations signalfd_fops = {
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.release = signalfd_release,
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.poll = signalfd_poll,
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.read = signalfd_read,
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.llseek = noop_llseek,
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};
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SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
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size_t, sizemask, int, flags)
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{
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sigset_t sigmask;
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struct signalfd_ctx *ctx;
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/* Check the SFD_* constants for consistency. */
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BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
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BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
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if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
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return -EINVAL;
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if (sizemask != sizeof(sigset_t) ||
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copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
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return -EINVAL;
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sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
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signotset(&sigmask);
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if (ufd == -1) {
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ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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ctx->sigmask = sigmask;
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/*
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* When we call this, the initialization must be complete, since
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* anon_inode_getfd() will install the fd.
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*/
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ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
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O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
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if (ufd < 0)
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kfree(ctx);
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} else {
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int fput_needed;
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struct file *file = fget_light(ufd, &fput_needed);
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if (!file)
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return -EBADF;
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ctx = file->private_data;
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if (file->f_op != &signalfd_fops) {
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fput_light(file, fput_needed);
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return -EINVAL;
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}
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spin_lock_irq(¤t->sighand->siglock);
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ctx->sigmask = sigmask;
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spin_unlock_irq(¤t->sighand->siglock);
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wake_up(¤t->sighand->signalfd_wqh);
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fput_light(file, fput_needed);
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}
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return ufd;
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}
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SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
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size_t, sizemask)
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{
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return sys_signalfd4(ufd, user_mask, sizemask, 0);
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}
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