Root/fs/signalfd.c

1/*
2 * fs/signalfd.c
3 *
4 * Copyright (C) 2003 Linus Torvalds
5 *
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().
18 */
19
20#include <linux/file.h>
21#include <linux/poll.h>
22#include <linux/init.h>
23#include <linux/fs.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
33struct signalfd_ctx {
34    sigset_t sigmask;
35};
36
37static int signalfd_release(struct inode *inode, struct file *file)
38{
39    kfree(file->private_data);
40    return 0;
41}
42
43static unsigned int signalfd_poll(struct file *file, poll_table *wait)
44{
45    struct signalfd_ctx *ctx = file->private_data;
46    unsigned int events = 0;
47
48    poll_wait(file, &current->sighand->signalfd_wqh, wait);
49
50    spin_lock_irq(&current->sighand->siglock);
51    if (next_signal(&current->pending, &ctx->sigmask) ||
52        next_signal(&current->signal->shared_pending,
53            &ctx->sigmask))
54        events |= POLLIN;
55    spin_unlock_irq(&current->sighand->siglock);
56
57    return events;
58}
59
60/*
61 * Copied from copy_siginfo_to_user() in kernel/signal.c
62 */
63static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
64                 siginfo_t const *kinfo)
65{
66    long err;
67
68    BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
69
70    /*
71     * Unused members should be zero ...
72     */
73    err = __clear_user(uinfo, sizeof(*uinfo));
74
75    /*
76     * If you change siginfo_t structure, please be sure
77     * this code is fixed accordingly.
78     */
79    err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
80    err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
81    err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
82    switch (kinfo->si_code & __SI_MASK) {
83    case __SI_KILL:
84        err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
85        err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
86        break;
87    case __SI_TIMER:
88         err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
89         err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
90         err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
91        break;
92    case __SI_POLL:
93        err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
94        err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
95        break;
96    case __SI_FAULT:
97        err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
98#ifdef __ARCH_SI_TRAPNO
99        err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
100#endif
101        break;
102    case __SI_CHLD:
103        err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
104        err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
105        err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
106        err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
107        err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
108        break;
109    case __SI_RT: /* This is not generated by the kernel as of now. */
110    case __SI_MESGQ: /* But this is */
111        err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
112        err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
113        err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
114        break;
115    default:
116        /*
117         * This case catches also the signals queued by sigqueue().
118         */
119        err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
120        err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
121        err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
122        err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
123        break;
124    }
125
126    return err ? -EFAULT: sizeof(*uinfo);
127}
128
129static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
130                int nonblock)
131{
132    ssize_t ret;
133    DECLARE_WAITQUEUE(wait, current);
134
135    spin_lock_irq(&current->sighand->siglock);
136    ret = dequeue_signal(current, &ctx->sigmask, info);
137    switch (ret) {
138    case 0:
139        if (!nonblock)
140            break;
141        ret = -EAGAIN;
142    default:
143        spin_unlock_irq(&current->sighand->siglock);
144        return ret;
145    }
146
147    add_wait_queue(&current->sighand->signalfd_wqh, &wait);
148    for (;;) {
149        set_current_state(TASK_INTERRUPTIBLE);
150        ret = dequeue_signal(current, &ctx->sigmask, info);
151        if (ret != 0)
152            break;
153        if (signal_pending(current)) {
154            ret = -ERESTARTSYS;
155            break;
156        }
157        spin_unlock_irq(&current->sighand->siglock);
158        schedule();
159        spin_lock_irq(&current->sighand->siglock);
160    }
161    spin_unlock_irq(&current->sighand->siglock);
162
163    remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
164    __set_current_state(TASK_RUNNING);
165
166    return ret;
167}
168
169/*
170 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
171 * error code. The "count" parameter must be at least the size of a
172 * "struct signalfd_siginfo".
173 */
174static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
175                 loff_t *ppos)
176{
177    struct signalfd_ctx *ctx = file->private_data;
178    struct signalfd_siginfo __user *siginfo;
179    int nonblock = file->f_flags & O_NONBLOCK;
180    ssize_t ret, total = 0;
181    siginfo_t info;
182
183    count /= sizeof(struct signalfd_siginfo);
184    if (!count)
185        return -EINVAL;
186
187    siginfo = (struct signalfd_siginfo __user *) buf;
188    do {
189        ret = signalfd_dequeue(ctx, &info, nonblock);
190        if (unlikely(ret <= 0))
191            break;
192        ret = signalfd_copyinfo(siginfo, &info);
193        if (ret < 0)
194            break;
195        siginfo++;
196        total += ret;
197        nonblock = 1;
198    } while (--count);
199
200    return total ? total: ret;
201}
202
203static const struct file_operations signalfd_fops = {
204    .release = signalfd_release,
205    .poll = signalfd_poll,
206    .read = signalfd_read,
207};
208
209SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
210        size_t, sizemask, int, flags)
211{
212    sigset_t sigmask;
213    struct signalfd_ctx *ctx;
214
215    /* Check the SFD_* constants for consistency. */
216    BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
217    BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
218
219    if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
220        return -EINVAL;
221
222    if (sizemask != sizeof(sigset_t) ||
223        copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
224        return -EINVAL;
225    sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
226    signotset(&sigmask);
227
228    if (ufd == -1) {
229        ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
230        if (!ctx)
231            return -ENOMEM;
232
233        ctx->sigmask = sigmask;
234
235        /*
236         * When we call this, the initialization must be complete, since
237         * anon_inode_getfd() will install the fd.
238         */
239        ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
240                       O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
241        if (ufd < 0)
242            kfree(ctx);
243    } else {
244        struct file *file = fget(ufd);
245        if (!file)
246            return -EBADF;
247        ctx = file->private_data;
248        if (file->f_op != &signalfd_fops) {
249            fput(file);
250            return -EINVAL;
251        }
252        spin_lock_irq(&current->sighand->siglock);
253        ctx->sigmask = sigmask;
254        spin_unlock_irq(&current->sighand->siglock);
255
256        wake_up(&current->sighand->signalfd_wqh);
257        fput(file);
258    }
259
260    return ufd;
261}
262
263SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
264        size_t, sizemask)
265{
266    return sys_signalfd4(ufd, user_mask, sizemask, 0);
267}
268

Archive Download this file



interactive