--- /dev/null
+/*
+ * 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.
+ */
+
+#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 {
+ struct list_head lnk;
+ wait_queue_head_t wqh;
+ sigset_t sigmask;
+ struct task_struct *tsk;
+};
+
+struct signalfd_lockctx {
+ struct task_struct *tsk;
+ unsigned long flags;
+};
+
+/*
+ * Tries to acquire the sighand lock. We do not increment the sighand
+ * use count, and we do not even pin the task struct, so we need to
+ * do it inside an RCU read lock, and we must be prepared for the
+ * ctx->tsk going to NULL (in signalfd_deliver()), and for the sighand
+ * being detached. We return 0 if the sighand has been detached, or
+ * 1 if we were able to pin the sighand lock.
+ */
+static int signalfd_lock(struct signalfd_ctx *ctx, struct signalfd_lockctx *lk)
+{
+ struct sighand_struct *sighand = NULL;
+
+ rcu_read_lock();
+ lk->tsk = rcu_dereference(ctx->tsk);
+ if (likely(lk->tsk != NULL))
+ sighand = lock_task_sighand(lk->tsk, &lk->flags);
+ rcu_read_unlock();
+
+ if (sighand && !ctx->tsk) {
+ unlock_task_sighand(lk->tsk, &lk->flags);
+ sighand = NULL;
+ }
+
+ return sighand != NULL;
+}
+
+static void signalfd_unlock(struct signalfd_lockctx *lk)
+{
+ unlock_task_sighand(lk->tsk, &lk->flags);
+}
+
+/*
+ * This must be called with the sighand lock held.
+ */
+void signalfd_deliver(struct task_struct *tsk, int sig)
+{
+ struct sighand_struct *sighand = tsk->sighand;
+ struct signalfd_ctx *ctx, *tmp;
+
+ BUG_ON(!sig);
+ list_for_each_entry_safe(ctx, tmp, &sighand->signalfd_list, lnk) {
+ /*
+ * We use a negative signal value as a way to broadcast that the
+ * sighand has been orphaned, so that we can notify all the
+ * listeners about this. Remember the ctx->sigmask is inverted,
+ * so if the user is interested in a signal, that corresponding
+ * bit will be zero.
+ */
+ if (sig < 0) {
+ if (ctx->tsk == tsk) {
+ ctx->tsk = NULL;
+ list_del_init(&ctx->lnk);
+ wake_up(&ctx->wqh);
+ }
+ } else {
+ if (!sigismember(&ctx->sigmask, sig))
+ wake_up(&ctx->wqh);
+ }
+ }
+}
+
+static void signalfd_cleanup(struct signalfd_ctx *ctx)
+{
+ struct signalfd_lockctx lk;
+
+ /*
+ * This is tricky. If the sighand is gone, we do not need to remove
+ * context from the list, the list itself won't be there anymore.
+ */
+ if (signalfd_lock(ctx, &lk)) {
+ list_del(&ctx->lnk);
+ signalfd_unlock(&lk);
+ }
+ kfree(ctx);
+}
+
+static int signalfd_release(struct inode *inode, struct file *file)
+{
+ signalfd_cleanup(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;
+ struct signalfd_lockctx lk;
+
+ poll_wait(file, &ctx->wqh, wait);
+
+ /*
+ * Let the caller get a POLLIN in this case, ala socket recv() when
+ * the peer disconnects.
+ */
+ if (signalfd_lock(ctx, &lk)) {
+ if (next_signal(&lk.tsk->pending, &ctx->sigmask) > 0 ||
+ next_signal(&lk.tsk->signal->shared_pending,
+ &ctx->sigmask) > 0)
+ events |= POLLIN;
+ signalfd_unlock(&lk);
+ } else
+ events |= POLLIN;
+
+ 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 memebers 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->signo);
+ err |= __put_user(kinfo->si_errno, &uinfo->err);
+ err |= __put_user((short)kinfo->si_code, &uinfo->code);
+ switch (kinfo->si_code & __SI_MASK) {
+ case __SI_KILL:
+ err |= __put_user(kinfo->si_pid, &uinfo->pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->uid);
+ break;
+ case __SI_TIMER:
+ err |= __put_user(kinfo->si_tid, &uinfo->tid);
+ err |= __put_user(kinfo->si_overrun, &uinfo->overrun);
+ err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
+ break;
+ case __SI_POLL:
+ err |= __put_user(kinfo->si_band, &uinfo->band);
+ err |= __put_user(kinfo->si_fd, &uinfo->fd);
+ break;
+ case __SI_FAULT:
+ err |= __put_user((long)kinfo->si_addr, &uinfo->addr);
+#ifdef __ARCH_SI_TRAPNO
+ err |= __put_user(kinfo->si_trapno, &uinfo->trapno);
+#endif
+ break;
+ case __SI_CHLD:
+ err |= __put_user(kinfo->si_pid, &uinfo->pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->uid);
+ err |= __put_user(kinfo->si_status, &uinfo->status);
+ err |= __put_user(kinfo->si_utime, &uinfo->utime);
+ err |= __put_user(kinfo->si_stime, &uinfo->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->pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->uid);
+ err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
+ break;
+ default: /* this is just in case for now ... */
+ err |= __put_user(kinfo->si_pid, &uinfo->pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->uid);
+ break;
+ }
+
+ return err ? -EFAULT: sizeof(*uinfo);
+}
+
+/*
+ * Returns either the size of a "struct signalfd_siginfo", or zero if the
+ * sighand we are attached to, has been orphaned. 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;
+ ssize_t res = 0;
+ int locked, signo;
+ siginfo_t info;
+ struct signalfd_lockctx lk;
+ DECLARE_WAITQUEUE(wait, current);
+
+ if (count < sizeof(struct signalfd_siginfo))
+ return -EINVAL;
+ locked = signalfd_lock(ctx, &lk);
+ if (!locked)
+ return 0;
+ res = -EAGAIN;
+ signo = dequeue_signal(lk.tsk, &ctx->sigmask, &info);
+ if (signo == 0 && !(file->f_flags & O_NONBLOCK)) {
+ add_wait_queue(&ctx->wqh, &wait);
+ for (;;) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ signo = dequeue_signal(lk.tsk, &ctx->sigmask, &info);
+ if (signo != 0)
+ break;
+ if (signal_pending(current)) {
+ res = -ERESTARTSYS;
+ break;
+ }
+ signalfd_unlock(&lk);
+ schedule();
+ locked = signalfd_lock(ctx, &lk);
+ if (unlikely(!locked)) {
+ /*
+ * Let the caller read zero byte, ala socket
+ * recv() when the peer disconnect. This test
+ * must be done before doing a dequeue_signal(),
+ * because if the sighand has been orphaned,
+ * the dequeue_signal() call is going to crash.
+ */
+ res = 0;
+ break;
+ }
+ }
+ remove_wait_queue(&ctx->wqh, &wait);
+ __set_current_state(TASK_RUNNING);
+ }
+ if (likely(locked))
+ signalfd_unlock(&lk);
+ if (likely(signo))
+ res = signalfd_copyinfo((struct signalfd_siginfo __user *) buf,
+ &info);
+
+ return res;
+}
+
+static const struct file_operations signalfd_fops = {
+ .release = signalfd_release,
+ .poll = signalfd_poll,
+ .read = signalfd_read,
+};
+
+/*
+ * Create a file descriptor that is associated with our signal
+ * state. We can pass it around to others if we want to, but
+ * it will always be _our_ signal state.
+ */
+asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
+{
+ int error;
+ sigset_t sigmask;
+ struct signalfd_ctx *ctx;
+ struct sighand_struct *sighand;
+ struct file *file;
+ struct inode *inode;
+ struct signalfd_lockctx lk;
+
+ if (sizemask != sizeof(sigset_t) ||
+ copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
+ return error = -EINVAL;
+ sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
+ signotset(&sigmask);
+
+ if (ufd == -1) {
+ ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ init_waitqueue_head(&ctx->wqh);
+ ctx->sigmask = sigmask;
+ ctx->tsk = current;
+
+ sighand = current->sighand;
+ /*
+ * Add this fd to the list of signal listeners.
+ */
+ spin_lock_irq(&sighand->siglock);
+ list_add_tail(&ctx->lnk, &sighand->signalfd_list);
+ spin_unlock_irq(&sighand->siglock);
+
+ /*
+ * 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;
+ }
+ /*
+ * We need to be prepared of the fact that the sighand this fd
+ * is attached to, has been detched. In that case signalfd_lock()
+ * will return 0, and we'll just skip setting the new mask.
+ */
+ if (signalfd_lock(ctx, &lk)) {
+ ctx->sigmask = sigmask;
+ signalfd_unlock(&lk);
+ }
+ wake_up(&ctx->wqh);
+ fput(file);
+ }
+
+ return ufd;
+
+err_fdalloc:
+ signalfd_cleanup(ctx);
+ return error;
+}
+
--- /dev/null
+/*
+ * include/linux/signalfd.h
+ *
+ * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
+ *
+ */
+
+#ifndef _LINUX_SIGNALFD_H
+#define _LINUX_SIGNALFD_H
+
+
+struct signalfd_siginfo {
+ __u32 signo;
+ __s32 err;
+ __s32 code;
+ __u32 pid;
+ __u32 uid;
+ __s32 fd;
+ __u32 tid;
+ __u32 band;
+ __u32 overrun;
+ __u32 trapno;
+ __s32 status;
+ __s32 svint;
+ __u64 svptr;
+ __u64 utime;
+ __u64 stime;
+ __u64 addr;
+
+ /*
+ * Pad strcture to 128 bytes. Remember to update the
+ * pad size when you add new memebers. We use a fixed
+ * size structure to avoid compatibility problems with
+ * future versions, and we leave extra space for additional
+ * members. We use fixed size members because this strcture
+ * comes out of a read(2) and we really don't want to have
+ * a compat on read(2).
+ */
+ __u8 __pad[48];
+};
+
+
+#ifdef __KERNEL__
+
+#ifdef CONFIG_SIGNALFD
+
+/*
+ * Deliver the signal to listening signalfd. This must be called
+ * with the sighand lock held. Same are the following that end up
+ * calling signalfd_deliver().
+ */
+void signalfd_deliver(struct task_struct *tsk, int sig);
+
+/*
+ * No need to fall inside signalfd_deliver() if no signal listeners
+ * are available.
+ */
+static inline void signalfd_notify(struct task_struct *tsk, int sig)
+{
+ if (unlikely(!list_empty(&tsk->sighand->signalfd_list)))
+ signalfd_deliver(tsk, sig);
+}
+
+/*
+ * The signal -1 is used to notify the signalfd that the sighand
+ * is on its way to be detached.
+ */
+static inline void signalfd_detach_locked(struct task_struct *tsk)
+{
+ if (unlikely(!list_empty(&tsk->sighand->signalfd_list)))
+ signalfd_deliver(tsk, -1);
+}
+
+static inline void signalfd_detach(struct task_struct *tsk)
+{
+ struct sighand_struct *sighand = tsk->sighand;
+
+ if (unlikely(!list_empty(&sighand->signalfd_list))) {
+ spin_lock_irq(&sighand->siglock);
+ signalfd_deliver(tsk, -1);
+ spin_unlock_irq(&sighand->siglock);
+ }
+}
+
+#else /* CONFIG_SIGNALFD */
+
+#define signalfd_deliver(t, s) do { } while (0)
+#define signalfd_notify(t, s) do { } while (0)
+#define signalfd_detach_locked(t) do { } while (0)
+#define signalfd_detach(t) do { } while (0)
+
+#endif /* CONFIG_SIGNALFD */
+
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_SIGNALFD_H */
+
#include <linux/syscalls.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
+#include <linux/signalfd.h>
#include <linux/capability.h>
#include <linux/freezer.h>
#include <linux/pid_namespace.h>
/* Given the mask, find the first available signal that should be serviced. */
-static int
-next_signal(struct sigpending *pending, sigset_t *mask)
+int next_signal(struct sigpending *pending, sigset_t *mask)
{
unsigned long i, *s, *m, x;
int sig = 0;
struct sigqueue * q = NULL;
int ret = 0;
+ /*
+ * Deliver the signal to listening signalfds. This must be called
+ * with the sighand lock held.
+ */
+ signalfd_notify(t, sig);
+
/*
* fast-pathed signals for kernel-internal things like SIGSTOP
* or SIGKILL.
ret = 1;
goto out;
}
+ /*
+ * Deliver the signal to listening signalfds. This must be called
+ * with the sighand lock held.
+ */
+ signalfd_notify(p, sig);
list_add_tail(&q->list, &p->pending.list);
sigaddset(&p->pending.signal, sig);
q->info.si_overrun++;
goto out;
}
+ /*
+ * Deliver the signal to listening signalfds. This must be called
+ * with the sighand lock held.
+ */
+ signalfd_notify(p, sig);
/*
* Put this signal on the shared-pending queue.
/*
* If you change siginfo_t structure, please be sure
* this code is fixed accordingly.
+ * Please remember to update the signalfd_copyinfo() function
+ * inside fs/signalfd.c too, in case siginfo_t changes.
* It should never copy any pad contained in the structure
* to avoid security leaks, but must copy the generic
* 3 ints plus the relevant union member.
projects / linux-2.6 / commitdiff