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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>
7ec37dfd 30#include <linux/syscalls.h>
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31
32struct signalfd_ctx {
fba2afaa 33 sigset_t sigmask;
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34};
35
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36static int signalfd_release(struct inode *inode, struct file *file)
37{
b8fceee1 38 kfree(file->private_data);
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39 return 0;
40}
41
42static unsigned int signalfd_poll(struct file *file, poll_table *wait)
43{
44 struct signalfd_ctx *ctx = file->private_data;
45 unsigned int events = 0;
fba2afaa 46
b8fceee1 47 poll_wait(file, &current->sighand->signalfd_wqh, wait);
fba2afaa 48
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49 spin_lock_irq(&current->sighand->siglock);
50 if (next_signal(&current->pending, &ctx->sigmask) ||
51 next_signal(&current->signal->shared_pending,
52 &ctx->sigmask))
fba2afaa 53 events |= POLLIN;
b8fceee1 54 spin_unlock_irq(&current->sighand->siglock);
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55
56 return events;
57}
58
59/*
60 * Copied from copy_siginfo_to_user() in kernel/signal.c
61 */
62static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
63 siginfo_t const *kinfo)
64{
65 long err;
66
67 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
68
69 /*
14e4a0f2 70 * Unused members should be zero ...
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71 */
72 err = __clear_user(uinfo, sizeof(*uinfo));
73
74 /*
75 * If you change siginfo_t structure, please be sure
76 * this code is fixed accordingly.
77 */
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78 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
79 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
80 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
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81 switch (kinfo->si_code & __SI_MASK) {
82 case __SI_KILL:
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83 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
84 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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85 break;
86 case __SI_TIMER:
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87 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
88 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
89 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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90 break;
91 case __SI_POLL:
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92 err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
93 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
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94 break;
95 case __SI_FAULT:
96358de6 96 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
fba2afaa 97#ifdef __ARCH_SI_TRAPNO
96358de6 98 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
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99#endif
100 break;
101 case __SI_CHLD:
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102 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
103 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
104 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
105 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
106 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
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107 break;
108 case __SI_RT: /* This is not generated by the kernel as of now. */
109 case __SI_MESGQ: /* But this is */
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110 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
111 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
112 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
fba2afaa 113 break;
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114 default:
115 /*
116 * This case catches also the signals queued by sigqueue().
117 */
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118 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
119 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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120 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
121 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
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122 break;
123 }
124
125 return err ? -EFAULT: sizeof(*uinfo);
126}
127
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128static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
129 int nonblock)
130{
131 ssize_t ret;
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132 DECLARE_WAITQUEUE(wait, current);
133
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134 spin_lock_irq(&current->sighand->siglock);
135 ret = dequeue_signal(current, &ctx->sigmask, info);
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136 switch (ret) {
137 case 0:
138 if (!nonblock)
139 break;
140 ret = -EAGAIN;
141 default:
b8fceee1 142 spin_unlock_irq(&current->sighand->siglock);
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143 return ret;
144 }
145
b8fceee1 146 add_wait_queue(&current->sighand->signalfd_wqh, &wait);
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147 for (;;) {
148 set_current_state(TASK_INTERRUPTIBLE);
b8fceee1 149 ret = dequeue_signal(current, &ctx->sigmask, info);
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150 if (ret != 0)
151 break;
152 if (signal_pending(current)) {
153 ret = -ERESTARTSYS;
154 break;
155 }
b8fceee1 156 spin_unlock_irq(&current->sighand->siglock);
b3762bfc 157 schedule();
b8fceee1 158 spin_lock_irq(&current->sighand->siglock);
b3762bfc 159 }
b8fceee1 160 spin_unlock_irq(&current->sighand->siglock);
b3762bfc 161
b8fceee1 162 remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
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163 __set_current_state(TASK_RUNNING);
164
165 return ret;
166}
167
fba2afaa 168/*
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169 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
170 * error code. The "count" parameter must be at least the size of a
171 * "struct signalfd_siginfo".
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172 */
173static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
174 loff_t *ppos)
175{
176 struct signalfd_ctx *ctx = file->private_data;
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177 struct signalfd_siginfo __user *siginfo;
178 int nonblock = file->f_flags & O_NONBLOCK;
179 ssize_t ret, total = 0;
fba2afaa 180 siginfo_t info;
fba2afaa 181
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182 count /= sizeof(struct signalfd_siginfo);
183 if (!count)
fba2afaa 184 return -EINVAL;
fba2afaa 185
b3762bfc 186 siginfo = (struct signalfd_siginfo __user *) buf;
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187 do {
188 ret = signalfd_dequeue(ctx, &info, nonblock);
189 if (unlikely(ret <= 0))
190 break;
191 ret = signalfd_copyinfo(siginfo, &info);
192 if (ret < 0)
193 break;
194 siginfo++;
195 total += ret;
196 nonblock = 1;
197 } while (--count);
198
b8fceee1 199 return total ? total: ret;
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200}
201
202static const struct file_operations signalfd_fops = {
203 .release = signalfd_release,
204 .poll = signalfd_poll,
205 .read = signalfd_read,
206};
207
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208asmlinkage long sys_signalfd4(int ufd, sigset_t __user *user_mask,
209 size_t sizemask, int flags)
fba2afaa 210{
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211 sigset_t sigmask;
212 struct signalfd_ctx *ctx;
fba2afaa 213
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214 /* Check the SFD_* constants for consistency. */
215 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
216 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
217
5fb5e049 218 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
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219 return -EINVAL;
220
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221 if (sizemask != sizeof(sigset_t) ||
222 copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
f50cadaa 223 return -EINVAL;
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224 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
225 signotset(&sigmask);
226
227 if (ufd == -1) {
228 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
229 if (!ctx)
230 return -ENOMEM;
231
fba2afaa 232 ctx->sigmask = sigmask;
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233
234 /*
235 * When we call this, the initialization must be complete, since
236 * anon_inode_getfd() will install the fd.
237 */
7d9dbca3 238 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
5fb5e049 239 flags & (O_CLOEXEC | O_NONBLOCK));
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240 if (ufd < 0)
241 kfree(ctx);
fba2afaa 242 } else {
2030a42c 243 struct file *file = fget(ufd);
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244 if (!file)
245 return -EBADF;
246 ctx = file->private_data;
247 if (file->f_op != &signalfd_fops) {
248 fput(file);
249 return -EINVAL;
250 }
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251 spin_lock_irq(&current->sighand->siglock);
252 ctx->sigmask = sigmask;
253 spin_unlock_irq(&current->sighand->siglock);
254
255 wake_up(&current->sighand->signalfd_wqh);
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256 fput(file);
257 }
258
259 return ufd;
fba2afaa 260}
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261
262asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask,
263 size_t sizemask)
264{
265 return sys_signalfd4(ufd, user_mask, sizemask, 0);
266}