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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.
b8fceee1 14 * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
b3762bfc 15 * Retrieve multiple signals with one read() call
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16 * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
17 * Attach to the sighand only during read() and poll().
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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/kernel.h>
26#include <linux/signal.h>
27#include <linux/list.h>
28#include <linux/anon_inodes.h>
29#include <linux/signalfd.h>
30
31struct signalfd_ctx {
fba2afaa 32 sigset_t sigmask;
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33};
34
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35static int signalfd_release(struct inode *inode, struct file *file)
36{
b8fceee1 37 kfree(file->private_data);
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38 return 0;
39}
40
41static unsigned int signalfd_poll(struct file *file, poll_table *wait)
42{
43 struct signalfd_ctx *ctx = file->private_data;
44 unsigned int events = 0;
fba2afaa 45
b8fceee1 46 poll_wait(file, &current->sighand->signalfd_wqh, wait);
fba2afaa 47
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48 spin_lock_irq(&current->sighand->siglock);
49 if (next_signal(&current->pending, &ctx->sigmask) ||
50 next_signal(&current->signal->shared_pending,
51 &ctx->sigmask))
fba2afaa 52 events |= POLLIN;
b8fceee1 53 spin_unlock_irq(&current->sighand->siglock);
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54
55 return events;
56}
57
58/*
59 * Copied from copy_siginfo_to_user() in kernel/signal.c
60 */
61static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
62 siginfo_t const *kinfo)
63{
64 long err;
65
66 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
67
68 /*
69 * Unused memebers should be zero ...
70 */
71 err = __clear_user(uinfo, sizeof(*uinfo));
72
73 /*
74 * If you change siginfo_t structure, please be sure
75 * this code is fixed accordingly.
76 */
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77 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
78 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
79 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
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80 switch (kinfo->si_code & __SI_MASK) {
81 case __SI_KILL:
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82 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
83 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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84 break;
85 case __SI_TIMER:
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86 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
87 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
88 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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89 break;
90 case __SI_POLL:
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91 err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
92 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
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93 break;
94 case __SI_FAULT:
96358de6 95 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
fba2afaa 96#ifdef __ARCH_SI_TRAPNO
96358de6 97 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
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98#endif
99 break;
100 case __SI_CHLD:
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101 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
102 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
103 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
104 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
105 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
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106 break;
107 case __SI_RT: /* This is not generated by the kernel as of now. */
108 case __SI_MESGQ: /* But this is */
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109 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
110 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
111 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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112 break;
113 default: /* this is just in case for now ... */
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114 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
115 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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116 break;
117 }
118
119 return err ? -EFAULT: sizeof(*uinfo);
120}
121
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122static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
123 int nonblock)
124{
125 ssize_t ret;
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126 DECLARE_WAITQUEUE(wait, current);
127
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128 spin_lock_irq(&current->sighand->siglock);
129 ret = dequeue_signal(current, &ctx->sigmask, info);
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130 switch (ret) {
131 case 0:
132 if (!nonblock)
133 break;
134 ret = -EAGAIN;
135 default:
b8fceee1 136 spin_unlock_irq(&current->sighand->siglock);
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137 return ret;
138 }
139
b8fceee1 140 add_wait_queue(&current->sighand->signalfd_wqh, &wait);
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141 for (;;) {
142 set_current_state(TASK_INTERRUPTIBLE);
b8fceee1 143 ret = dequeue_signal(current, &ctx->sigmask, info);
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144 if (ret != 0)
145 break;
146 if (signal_pending(current)) {
147 ret = -ERESTARTSYS;
148 break;
149 }
b8fceee1 150 spin_unlock_irq(&current->sighand->siglock);
b3762bfc 151 schedule();
b8fceee1 152 spin_lock_irq(&current->sighand->siglock);
b3762bfc 153 }
b8fceee1 154 spin_unlock_irq(&current->sighand->siglock);
b3762bfc 155
b8fceee1 156 remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
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157 __set_current_state(TASK_RUNNING);
158
159 return ret;
160}
161
fba2afaa 162/*
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163 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
164 * error code. The "count" parameter must be at least the size of a
165 * "struct signalfd_siginfo".
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166 */
167static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
168 loff_t *ppos)
169{
170 struct signalfd_ctx *ctx = file->private_data;
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171 struct signalfd_siginfo __user *siginfo;
172 int nonblock = file->f_flags & O_NONBLOCK;
173 ssize_t ret, total = 0;
fba2afaa 174 siginfo_t info;
fba2afaa 175
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176 count /= sizeof(struct signalfd_siginfo);
177 if (!count)
fba2afaa 178 return -EINVAL;
fba2afaa 179
b3762bfc 180 siginfo = (struct signalfd_siginfo __user *) buf;
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181 do {
182 ret = signalfd_dequeue(ctx, &info, nonblock);
183 if (unlikely(ret <= 0))
184 break;
185 ret = signalfd_copyinfo(siginfo, &info);
186 if (ret < 0)
187 break;
188 siginfo++;
189 total += ret;
190 nonblock = 1;
191 } while (--count);
192
b8fceee1 193 return total ? total: ret;
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194}
195
196static const struct file_operations signalfd_fops = {
197 .release = signalfd_release,
198 .poll = signalfd_poll,
199 .read = signalfd_read,
200};
201
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202asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
203{
204 int error;
205 sigset_t sigmask;
206 struct signalfd_ctx *ctx;
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207 struct file *file;
208 struct inode *inode;
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209
210 if (sizemask != sizeof(sigset_t) ||
211 copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
f50cadaa 212 return -EINVAL;
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213 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
214 signotset(&sigmask);
215
216 if (ufd == -1) {
217 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
218 if (!ctx)
219 return -ENOMEM;
220
fba2afaa 221 ctx->sigmask = sigmask;
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222
223 /*
224 * When we call this, the initialization must be complete, since
225 * anon_inode_getfd() will install the fd.
226 */
227 error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]",
228 &signalfd_fops, ctx);
229 if (error)
230 goto err_fdalloc;
231 } else {
232 file = fget(ufd);
233 if (!file)
234 return -EBADF;
235 ctx = file->private_data;
236 if (file->f_op != &signalfd_fops) {
237 fput(file);
238 return -EINVAL;
239 }
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240 spin_lock_irq(&current->sighand->siglock);
241 ctx->sigmask = sigmask;
242 spin_unlock_irq(&current->sighand->siglock);
243
244 wake_up(&current->sighand->signalfd_wqh);
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245 fput(file);
246 }
247
248 return ufd;
249
250err_fdalloc:
b8fceee1 251 kfree(ctx);
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252 return error;
253}
254