4 * Copyright (C) 2003 Linus Torvalds
6 * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
7 * Changed ->read() to return a siginfo strcture instead of signal number.
8 * Fixed locking in ->poll().
9 * Added sighand-detach notification.
10 * Added fd re-use in sys_signalfd() syscall.
11 * Now using anonymous inode source.
12 * Thanks to Oleg Nesterov for useful code review and suggestions.
13 * More comments and suggestions from Arnd Bergmann.
14 * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
15 * Retrieve multiple signals with one read() call
16 * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
17 * Attach to the sighand only during read() and poll().
20 #include <linux/file.h>
21 #include <linux/poll.h>
22 #include <linux/init.h>
24 #include <linux/sched.h>
25 #include <linux/slab.h>
26 #include <linux/kernel.h>
27 #include <linux/signal.h>
28 #include <linux/list.h>
29 #include <linux/anon_inodes.h>
30 #include <linux/signalfd.h>
31 #include <linux/syscalls.h>
32 #include <linux/proc_fs.h>
34 void signalfd_cleanup(struct sighand_struct *sighand)
36 wait_queue_head_t *wqh = &sighand->signalfd_wqh;
38 * The lockless check can race with remove_wait_queue() in progress,
39 * but in this case its caller should run under rcu_read_lock() and
40 * sighand_cachep is SLAB_DESTROY_BY_RCU, we can safely return.
42 if (likely(!waitqueue_active(wqh)))
45 /* wait_queue_t->func(POLLFREE) should do remove_wait_queue() */
46 wake_up_poll(wqh, POLLHUP | POLLFREE);
53 static int signalfd_release(struct inode *inode, struct file *file)
55 kfree(file->private_data);
59 static unsigned int signalfd_poll(struct file *file, poll_table *wait)
61 struct signalfd_ctx *ctx = file->private_data;
62 unsigned int events = 0;
64 poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
66 spin_lock_irq(¤t->sighand->siglock);
67 if (next_signal(¤t->pending, &ctx->sigmask) ||
68 next_signal(¤t->signal->shared_pending,
71 spin_unlock_irq(¤t->sighand->siglock);
77 * Copied from copy_siginfo_to_user() in kernel/signal.c
79 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
80 siginfo_t const *kinfo)
84 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
87 * Unused members should be zero ...
89 err = __clear_user(uinfo, sizeof(*uinfo));
92 * If you change siginfo_t structure, please be sure
93 * this code is fixed accordingly.
95 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
96 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
97 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
98 switch (kinfo->si_code & __SI_MASK) {
100 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
101 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
104 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
105 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
106 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
107 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
110 err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
111 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
114 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
115 #ifdef __ARCH_SI_TRAPNO
116 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
120 * Other callers might not initialize the si_lsb field,
121 * so check explicitly for the right codes here.
123 if (kinfo->si_code == BUS_MCEERR_AR ||
124 kinfo->si_code == BUS_MCEERR_AO)
125 err |= __put_user((short) kinfo->si_addr_lsb,
126 &uinfo->ssi_addr_lsb);
130 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
131 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
132 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
133 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
134 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
136 case __SI_RT: /* This is not generated by the kernel as of now. */
137 case __SI_MESGQ: /* But this is */
138 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
139 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
140 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
141 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
145 * This case catches also the signals queued by sigqueue().
147 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
148 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
149 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
150 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
154 return err ? -EFAULT: sizeof(*uinfo);
157 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
161 DECLARE_WAITQUEUE(wait, current);
163 spin_lock_irq(¤t->sighand->siglock);
164 ret = dequeue_signal(current, &ctx->sigmask, info);
171 spin_unlock_irq(¤t->sighand->siglock);
175 add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
177 set_current_state(TASK_INTERRUPTIBLE);
178 ret = dequeue_signal(current, &ctx->sigmask, info);
181 if (signal_pending(current)) {
185 spin_unlock_irq(¤t->sighand->siglock);
187 spin_lock_irq(¤t->sighand->siglock);
189 spin_unlock_irq(¤t->sighand->siglock);
191 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
192 __set_current_state(TASK_RUNNING);
198 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
199 * error code. The "count" parameter must be at least the size of a
200 * "struct signalfd_siginfo".
202 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
205 struct signalfd_ctx *ctx = file->private_data;
206 struct signalfd_siginfo __user *siginfo;
207 int nonblock = file->f_flags & O_NONBLOCK;
208 ssize_t ret, total = 0;
211 count /= sizeof(struct signalfd_siginfo);
215 siginfo = (struct signalfd_siginfo __user *) buf;
217 ret = signalfd_dequeue(ctx, &info, nonblock);
218 if (unlikely(ret <= 0))
220 ret = signalfd_copyinfo(siginfo, &info);
228 return total ? total: ret;
231 #ifdef CONFIG_PROC_FS
232 static int signalfd_show_fdinfo(struct seq_file *m, struct file *f)
234 struct signalfd_ctx *ctx = f->private_data;
237 sigmask = ctx->sigmask;
239 render_sigset_t(m, "sigmask:\t", &sigmask);
245 static const struct file_operations signalfd_fops = {
246 #ifdef CONFIG_PROC_FS
247 .show_fdinfo = signalfd_show_fdinfo,
249 .release = signalfd_release,
250 .poll = signalfd_poll,
251 .read = signalfd_read,
252 .llseek = noop_llseek,
255 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
256 size_t, sizemask, int, flags)
259 struct signalfd_ctx *ctx;
261 /* Check the SFD_* constants for consistency. */
262 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
263 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
265 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
268 if (sizemask != sizeof(sigset_t) ||
269 copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
271 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
275 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
279 ctx->sigmask = sigmask;
282 * When we call this, the initialization must be complete, since
283 * anon_inode_getfd() will install the fd.
285 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
286 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
290 struct fd f = fdget(ufd);
293 ctx = f.file->private_data;
294 if (f.file->f_op != &signalfd_fops) {
298 spin_lock_irq(¤t->sighand->siglock);
299 ctx->sigmask = sigmask;
300 spin_unlock_irq(¤t->sighand->siglock);
302 wake_up(¤t->sighand->signalfd_wqh);
309 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
312 return sys_signalfd4(ufd, user_mask, sizemask, 0);