/* * 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> 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, ¤t->sighand->signalfd_wqh, wait); spin_lock_irq(¤t->sighand->siglock); if (next_signal(¤t->pending, &ctx->sigmask) || next_signal(¤t->signal->shared_pending, &ctx->sigmask)) events |= POLLIN; spin_unlock_irq(¤t->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 is just in case for now ... */ err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 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(¤t->sighand->siglock); ret = dequeue_signal(current, &ctx->sigmask, info); switch (ret) { case 0: if (!nonblock) break; ret = -EAGAIN; default: spin_unlock_irq(¤t->sighand->siglock); return ret; } add_wait_queue(¤t->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(¤t->sighand->siglock); schedule(); spin_lock_irq(¤t->sighand->siglock); } spin_unlock_irq(¤t->sighand->siglock); remove_wait_queue(¤t->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_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask) { int error; sigset_t sigmask; struct signalfd_ctx *ctx; struct file *file; struct inode *inode; 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. */ error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]", &signalfd_fops, ctx); if (error) goto err_fdalloc; } else { file = fget(ufd); if (!file) return -EBADF; ctx = file->private_data; if (file->f_op != &signalfd_fops) { fput(file); return -EINVAL; } spin_lock_irq(¤t->sighand->siglock); ctx->sigmask = sigmask; spin_unlock_irq(¤t->sighand->siglock); wake_up(¤t->sighand->signalfd_wqh); fput(file); } return ufd; err_fdalloc: kfree(ctx); return error; }