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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. | |
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 | #include <linux/proc_fs.h> | |
33 | #include <linux/compat.h> | |
34 | ||
35 | void signalfd_cleanup(struct sighand_struct *sighand) | |
36 | { | |
37 | wait_queue_head_t *wqh = &sighand->signalfd_wqh; | |
38 | /* | |
39 | * The lockless check can race with remove_wait_queue() in progress, | |
40 | * but in this case its caller should run under rcu_read_lock() and | |
41 | * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return. | |
42 | */ | |
43 | if (likely(!waitqueue_active(wqh))) | |
44 | return; | |
45 | ||
46 | /* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */ | |
47 | wake_up_poll(wqh, POLLHUP | POLLFREE); | |
48 | } | |
49 | ||
50 | struct signalfd_ctx { | |
51 | sigset_t sigmask; | |
52 | }; | |
53 | ||
54 | static int signalfd_release(struct inode *inode, struct file *file) | |
55 | { | |
56 | kfree(file->private_data); | |
57 | return 0; | |
58 | } | |
59 | ||
60 | static unsigned int signalfd_poll(struct file *file, poll_table *wait) | |
61 | { | |
62 | struct signalfd_ctx *ctx = file->private_data; | |
63 | unsigned int events = 0; | |
64 | ||
65 | poll_wait(file, ¤t->sighand->signalfd_wqh, wait); | |
66 | ||
67 | spin_lock_irq(¤t->sighand->siglock); | |
68 | if (next_signal(¤t->pending, &ctx->sigmask) || | |
69 | next_signal(¤t->signal->shared_pending, | |
70 | &ctx->sigmask)) | |
71 | events |= POLLIN; | |
72 | spin_unlock_irq(¤t->sighand->siglock); | |
73 | ||
74 | return events; | |
75 | } | |
76 | ||
77 | /* | |
78 | * Copied from copy_siginfo_to_user() in kernel/signal.c | |
79 | */ | |
80 | static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, | |
81 | siginfo_t const *kinfo) | |
82 | { | |
83 | long err; | |
84 | ||
85 | BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); | |
86 | ||
87 | /* | |
88 | * Unused members should be zero ... | |
89 | */ | |
90 | err = __clear_user(uinfo, sizeof(*uinfo)); | |
91 | ||
92 | /* | |
93 | * If you change siginfo_t structure, please be sure | |
94 | * this code is fixed accordingly. | |
95 | */ | |
96 | err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo); | |
97 | err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno); | |
98 | err |= __put_user(kinfo->si_code, &uinfo->ssi_code); | |
99 | switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) { | |
100 | case SIL_KILL: | |
101 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); | |
102 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); | |
103 | break; | |
104 | case SIL_TIMER: | |
105 | err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid); | |
106 | err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun); | |
107 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); | |
108 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); | |
109 | break; | |
110 | case SIL_POLL: | |
111 | err |= __put_user(kinfo->si_band, &uinfo->ssi_band); | |
112 | err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd); | |
113 | break; | |
114 | case SIL_FAULT: | |
115 | err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr); | |
116 | #ifdef __ARCH_SI_TRAPNO | |
117 | err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno); | |
118 | #endif | |
119 | #ifdef BUS_MCEERR_AO | |
120 | /* | |
121 | * Other callers might not initialize the si_lsb field, | |
122 | * so check explicitly for the right codes here. | |
123 | */ | |
124 | if (kinfo->si_signo == SIGBUS && | |
125 | (kinfo->si_code == BUS_MCEERR_AR || | |
126 | kinfo->si_code == BUS_MCEERR_AO)) | |
127 | err |= __put_user((short) kinfo->si_addr_lsb, | |
128 | &uinfo->ssi_addr_lsb); | |
129 | #endif | |
130 | break; | |
131 | case SIL_CHLD: | |
132 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); | |
133 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); | |
134 | err |= __put_user(kinfo->si_status, &uinfo->ssi_status); | |
135 | err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); | |
136 | err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); | |
137 | break; | |
138 | case SIL_RT: | |
139 | default: | |
140 | /* | |
141 | * This case catches also the signals queued by sigqueue(). | |
142 | */ | |
143 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); | |
144 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); | |
145 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); | |
146 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); | |
147 | break; | |
148 | } | |
149 | ||
150 | return err ? -EFAULT: sizeof(*uinfo); | |
151 | } | |
152 | ||
153 | static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, | |
154 | int nonblock) | |
155 | { | |
156 | ssize_t ret; | |
157 | DECLARE_WAITQUEUE(wait, current); | |
158 | ||
159 | spin_lock_irq(¤t->sighand->siglock); | |
160 | ret = dequeue_signal(current, &ctx->sigmask, info); | |
161 | switch (ret) { | |
162 | case 0: | |
163 | if (!nonblock) | |
164 | break; | |
165 | ret = -EAGAIN; | |
166 | default: | |
167 | spin_unlock_irq(¤t->sighand->siglock); | |
168 | return ret; | |
169 | } | |
170 | ||
171 | add_wait_queue(¤t->sighand->signalfd_wqh, &wait); | |
172 | for (;;) { | |
173 | set_current_state(TASK_INTERRUPTIBLE); | |
174 | ret = dequeue_signal(current, &ctx->sigmask, info); | |
175 | if (ret != 0) | |
176 | break; | |
177 | if (signal_pending(current)) { | |
178 | ret = -ERESTARTSYS; | |
179 | break; | |
180 | } | |
181 | spin_unlock_irq(¤t->sighand->siglock); | |
182 | schedule(); | |
183 | spin_lock_irq(¤t->sighand->siglock); | |
184 | } | |
185 | spin_unlock_irq(¤t->sighand->siglock); | |
186 | ||
187 | remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); | |
188 | __set_current_state(TASK_RUNNING); | |
189 | ||
190 | return ret; | |
191 | } | |
192 | ||
193 | /* | |
194 | * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative | |
195 | * error code. The "count" parameter must be at least the size of a | |
196 | * "struct signalfd_siginfo". | |
197 | */ | |
198 | static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, | |
199 | loff_t *ppos) | |
200 | { | |
201 | struct signalfd_ctx *ctx = file->private_data; | |
202 | struct signalfd_siginfo __user *siginfo; | |
203 | int nonblock = file->f_flags & O_NONBLOCK; | |
204 | ssize_t ret, total = 0; | |
205 | siginfo_t info; | |
206 | ||
207 | count /= sizeof(struct signalfd_siginfo); | |
208 | if (!count) | |
209 | return -EINVAL; | |
210 | ||
211 | siginfo = (struct signalfd_siginfo __user *) buf; | |
212 | do { | |
213 | ret = signalfd_dequeue(ctx, &info, nonblock); | |
214 | if (unlikely(ret <= 0)) | |
215 | break; | |
216 | ret = signalfd_copyinfo(siginfo, &info); | |
217 | if (ret < 0) | |
218 | break; | |
219 | siginfo++; | |
220 | total += ret; | |
221 | nonblock = 1; | |
222 | } while (--count); | |
223 | ||
224 | return total ? total: ret; | |
225 | } | |
226 | ||
227 | #ifdef CONFIG_PROC_FS | |
228 | static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) | |
229 | { | |
230 | struct signalfd_ctx *ctx = f->private_data; | |
231 | sigset_t sigmask; | |
232 | ||
233 | sigmask = ctx->sigmask; | |
234 | signotset(&sigmask); | |
235 | render_sigset_t(m, "sigmask:\t", &sigmask); | |
236 | } | |
237 | #endif | |
238 | ||
239 | static const struct file_operations signalfd_fops = { | |
240 | #ifdef CONFIG_PROC_FS | |
241 | .show_fdinfo = signalfd_show_fdinfo, | |
242 | #endif | |
243 | .release = signalfd_release, | |
244 | .poll = signalfd_poll, | |
245 | .read = signalfd_read, | |
246 | .llseek = noop_llseek, | |
247 | }; | |
248 | ||
249 | SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, | |
250 | size_t, sizemask, int, flags) | |
251 | { | |
252 | sigset_t sigmask; | |
253 | struct signalfd_ctx *ctx; | |
254 | ||
255 | /* Check the SFD_* constants for consistency. */ | |
256 | BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); | |
257 | BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); | |
258 | ||
259 | if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) | |
260 | return -EINVAL; | |
261 | ||
262 | if (sizemask != sizeof(sigset_t) || | |
263 | copy_from_user(&sigmask, user_mask, sizeof(sigmask))) | |
264 | return -EINVAL; | |
265 | sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
266 | signotset(&sigmask); | |
267 | ||
268 | if (ufd == -1) { | |
269 | ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); | |
270 | if (!ctx) | |
271 | return -ENOMEM; | |
272 | ||
273 | ctx->sigmask = sigmask; | |
274 | ||
275 | /* | |
276 | * When we call this, the initialization must be complete, since | |
277 | * anon_inode_getfd() will install the fd. | |
278 | */ | |
279 | ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, | |
280 | O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); | |
281 | if (ufd < 0) | |
282 | kfree(ctx); | |
283 | } else { | |
284 | struct fd f = fdget(ufd); | |
285 | if (!f.file) | |
286 | return -EBADF; | |
287 | ctx = f.file->private_data; | |
288 | if (f.file->f_op != &signalfd_fops) { | |
289 | fdput(f); | |
290 | return -EINVAL; | |
291 | } | |
292 | spin_lock_irq(¤t->sighand->siglock); | |
293 | ctx->sigmask = sigmask; | |
294 | spin_unlock_irq(¤t->sighand->siglock); | |
295 | ||
296 | wake_up(¤t->sighand->signalfd_wqh); | |
297 | fdput(f); | |
298 | } | |
299 | ||
300 | return ufd; | |
301 | } | |
302 | ||
303 | SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, | |
304 | size_t, sizemask) | |
305 | { | |
306 | return sys_signalfd4(ufd, user_mask, sizemask, 0); | |
307 | } | |
308 | ||
309 | #ifdef CONFIG_COMPAT | |
310 | COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, | |
311 | const compat_sigset_t __user *,sigmask, | |
312 | compat_size_t, sigsetsize, | |
313 | int, flags) | |
314 | { | |
315 | compat_sigset_t ss32; | |
316 | sigset_t tmp; | |
317 | sigset_t __user *ksigmask; | |
318 | ||
319 | if (sigsetsize != sizeof(compat_sigset_t)) | |
320 | return -EINVAL; | |
321 | if (copy_from_user(&ss32, sigmask, sizeof(ss32))) | |
322 | return -EFAULT; | |
323 | sigset_from_compat(&tmp, &ss32); | |
324 | ksigmask = compat_alloc_user_space(sizeof(sigset_t)); | |
325 | if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) | |
326 | return -EFAULT; | |
327 | ||
328 | return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); | |
329 | } | |
330 | ||
331 | COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, | |
332 | const compat_sigset_t __user *,sigmask, | |
333 | compat_size_t, sigsetsize) | |
334 | { | |
335 | return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); | |
336 | } | |
337 | #endif |