1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2003 Linus Torvalds
7 * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
8 * Changed ->read() to return a siginfo strcture instead of signal number.
9 * Fixed locking in ->poll().
10 * Added sighand-detach notification.
11 * Added fd re-use in sys_signalfd() syscall.
12 * Now using anonymous inode source.
13 * Thanks to Oleg Nesterov for useful code review and suggestions.
14 * More comments and suggestions from Arnd Bergmann.
15 * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
16 * Retrieve multiple signals with one read() call
17 * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
18 * Attach to the sighand only during read() and poll().
21 #include <linux/file.h>
22 #include <linux/poll.h>
23 #include <linux/init.h>
25 #include <linux/sched.h>
26 #include <linux/slab.h>
27 #include <linux/kernel.h>
28 #include <linux/signal.h>
29 #include <linux/list.h>
30 #include <linux/anon_inodes.h>
31 #include <linux/signalfd.h>
32 #include <linux/syscalls.h>
33 #include <linux/proc_fs.h>
34 #include <linux/compat.h>
36 void signalfd_cleanup(struct sighand_struct *sighand)
38 wait_queue_head_t *wqh = &sighand->signalfd_wqh;
40 * The lockless check can race with remove_wait_queue() in progress,
41 * but in this case its caller should run under rcu_read_lock() and
42 * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return.
44 if (likely(!waitqueue_active(wqh)))
47 /* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */
48 wake_up_poll(wqh, EPOLLHUP | POLLFREE);
55 static int signalfd_release(struct inode *inode, struct file *file)
57 kfree(file->private_data);
61 static __poll_t signalfd_poll(struct file *file, poll_table *wait)
63 struct signalfd_ctx *ctx = file->private_data;
66 poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
68 spin_lock_irq(¤t->sighand->siglock);
69 if (next_signal(¤t->pending, &ctx->sigmask) ||
70 next_signal(¤t->signal->shared_pending,
73 spin_unlock_irq(¤t->sighand->siglock);
79 * Copied from copy_siginfo_to_user() in kernel/signal.c
81 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
82 kernel_siginfo_t const *kinfo)
84 struct signalfd_siginfo new;
86 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
89 * Unused members should be zero ...
91 memset(&new, 0, sizeof(new));
94 * If you change siginfo_t structure, please be sure
95 * this code is fixed accordingly.
97 new.ssi_signo = kinfo->si_signo;
98 new.ssi_errno = kinfo->si_errno;
99 new.ssi_code = kinfo->si_code;
100 switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) {
102 new.ssi_pid = kinfo->si_pid;
103 new.ssi_uid = kinfo->si_uid;
106 new.ssi_tid = kinfo->si_tid;
107 new.ssi_overrun = kinfo->si_overrun;
108 new.ssi_ptr = (long) kinfo->si_ptr;
109 new.ssi_int = kinfo->si_int;
112 new.ssi_band = kinfo->si_band;
113 new.ssi_fd = kinfo->si_fd;
115 case SIL_FAULT_BNDERR:
116 case SIL_FAULT_PKUERR:
118 * Fall through to the SIL_FAULT case. Both SIL_FAULT_BNDERR
119 * and SIL_FAULT_PKUERR are only generated by faults that
120 * deliver them synchronously to userspace. In case someone
121 * injects one of these signals and signalfd catches it treat
125 new.ssi_addr = (long) kinfo->si_addr;
126 #ifdef __ARCH_SI_TRAPNO
127 new.ssi_trapno = kinfo->si_trapno;
130 case SIL_FAULT_MCEERR:
131 new.ssi_addr = (long) kinfo->si_addr;
132 #ifdef __ARCH_SI_TRAPNO
133 new.ssi_trapno = kinfo->si_trapno;
135 new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
138 new.ssi_pid = kinfo->si_pid;
139 new.ssi_uid = kinfo->si_uid;
140 new.ssi_status = kinfo->si_status;
141 new.ssi_utime = kinfo->si_utime;
142 new.ssi_stime = kinfo->si_stime;
146 * This case catches also the signals queued by sigqueue().
148 new.ssi_pid = kinfo->si_pid;
149 new.ssi_uid = kinfo->si_uid;
150 new.ssi_ptr = (long) kinfo->si_ptr;
151 new.ssi_int = kinfo->si_int;
154 new.ssi_call_addr = (long) kinfo->si_call_addr;
155 new.ssi_syscall = kinfo->si_syscall;
156 new.ssi_arch = kinfo->si_arch;
160 if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
163 return sizeof(*uinfo);
166 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
170 DECLARE_WAITQUEUE(wait, current);
172 spin_lock_irq(¤t->sighand->siglock);
173 ret = dequeue_signal(current, &ctx->sigmask, info);
181 spin_unlock_irq(¤t->sighand->siglock);
185 add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
187 set_current_state(TASK_INTERRUPTIBLE);
188 ret = dequeue_signal(current, &ctx->sigmask, info);
191 if (signal_pending(current)) {
195 spin_unlock_irq(¤t->sighand->siglock);
197 spin_lock_irq(¤t->sighand->siglock);
199 spin_unlock_irq(¤t->sighand->siglock);
201 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
202 __set_current_state(TASK_RUNNING);
208 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
209 * error code. The "count" parameter must be at least the size of a
210 * "struct signalfd_siginfo".
212 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
215 struct signalfd_ctx *ctx = file->private_data;
216 struct signalfd_siginfo __user *siginfo;
217 int nonblock = file->f_flags & O_NONBLOCK;
218 ssize_t ret, total = 0;
219 kernel_siginfo_t info;
221 count /= sizeof(struct signalfd_siginfo);
225 siginfo = (struct signalfd_siginfo __user *) buf;
227 ret = signalfd_dequeue(ctx, &info, nonblock);
228 if (unlikely(ret <= 0))
230 ret = signalfd_copyinfo(siginfo, &info);
238 return total ? total: ret;
241 #ifdef CONFIG_PROC_FS
242 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f)
244 struct signalfd_ctx *ctx = f->private_data;
247 sigmask = ctx->sigmask;
249 render_sigset_t(m, "sigmask:\t", &sigmask);
253 static const struct file_operations signalfd_fops = {
254 #ifdef CONFIG_PROC_FS
255 .show_fdinfo = signalfd_show_fdinfo,
257 .release = signalfd_release,
258 .poll = signalfd_poll,
259 .read = signalfd_read,
260 .llseek = noop_llseek,
263 static int do_signalfd4(int ufd, sigset_t *mask, int flags)
265 struct signalfd_ctx *ctx;
267 /* Check the SFD_* constants for consistency. */
268 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
269 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
271 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
274 sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
278 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
282 ctx->sigmask = *mask;
285 * When we call this, the initialization must be complete, since
286 * anon_inode_getfd() will install the fd.
288 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
289 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
293 struct fd f = fdget(ufd);
296 ctx = f.file->private_data;
297 if (f.file->f_op != &signalfd_fops) {
301 spin_lock_irq(¤t->sighand->siglock);
302 ctx->sigmask = *mask;
303 spin_unlock_irq(¤t->sighand->siglock);
305 wake_up(¤t->sighand->signalfd_wqh);
312 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
313 size_t, sizemask, int, flags)
317 if (sizemask != sizeof(sigset_t))
319 if (copy_from_user(&mask, user_mask, sizeof(mask)))
321 return do_signalfd4(ufd, &mask, flags);
324 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
329 if (sizemask != sizeof(sigset_t))
331 if (copy_from_user(&mask, user_mask, sizeof(mask)))
333 return do_signalfd4(ufd, &mask, 0);
337 static long do_compat_signalfd4(int ufd,
338 const compat_sigset_t __user *user_mask,
339 compat_size_t sigsetsize, int flags)
343 if (sigsetsize != sizeof(compat_sigset_t))
345 if (get_compat_sigset(&mask, user_mask))
347 return do_signalfd4(ufd, &mask, flags);
350 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
351 const compat_sigset_t __user *, user_mask,
352 compat_size_t, sigsetsize,
355 return do_compat_signalfd4(ufd, user_mask, sigsetsize, flags);
358 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
359 const compat_sigset_t __user *, user_mask,
360 compat_size_t, sigsetsize)
362 return do_compat_signalfd4(ufd, user_mask, sigsetsize, 0);