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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_DESTROY_BY_RCU, we can safely return. |
42 | */ |
43 | if (likely(!waitqueue_active(wqh))) |
44 | return; |
45 | |
46 | /* wait_queue_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((short) kinfo->si_code, &uinfo->ssi_code); |
99 | switch (kinfo->si_code & __SI_MASK) { |
100 | case __SI_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 __SI_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 __SI_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 __SI_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_code == BUS_MCEERR_AR || |
125 | kinfo->si_code == BUS_MCEERR_AO) |
126 | err |= __put_user((short) kinfo->si_addr_lsb, |
127 | &uinfo->ssi_addr_lsb); |
128 | #endif |
129 | break; |
130 | case __SI_CHLD: |
131 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); |
132 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); |
133 | err |= __put_user(kinfo->si_status, &uinfo->ssi_status); |
134 | err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); |
135 | err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); |
136 | break; |
137 | case __SI_RT: /* This is not generated by the kernel as of now. */ |
138 | case __SI_MESGQ: /* But this is */ |
139 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); |
140 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); |
141 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); |
142 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); |
143 | break; |
144 | default: |
145 | /* |
146 | * This case catches also the signals queued by sigqueue(). |
147 | */ |
148 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); |
149 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); |
150 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); |
151 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); |
152 | break; |
153 | } |
154 | |
155 | return err ? -EFAULT: sizeof(*uinfo); |
156 | } |
157 | |
158 | static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, |
159 | int nonblock) |
160 | { |
161 | ssize_t ret; |
162 | DECLARE_WAITQUEUE(wait, current); |
163 | |
164 | spin_lock_irq(¤t->sighand->siglock); |
165 | ret = dequeue_signal(current, &ctx->sigmask, info); |
166 | switch (ret) { |
167 | case 0: |
168 | if (!nonblock) |
169 | break; |
170 | ret = -EAGAIN; |
171 | default: |
172 | spin_unlock_irq(¤t->sighand->siglock); |
173 | return ret; |
174 | } |
175 | |
176 | add_wait_queue(¤t->sighand->signalfd_wqh, &wait); |
177 | for (;;) { |
178 | set_current_state(TASK_INTERRUPTIBLE); |
179 | ret = dequeue_signal(current, &ctx->sigmask, info); |
180 | if (ret != 0) |
181 | break; |
182 | if (signal_pending(current)) { |
183 | ret = -ERESTARTSYS; |
184 | break; |
185 | } |
186 | spin_unlock_irq(¤t->sighand->siglock); |
187 | schedule(); |
188 | spin_lock_irq(¤t->sighand->siglock); |
189 | } |
190 | spin_unlock_irq(¤t->sighand->siglock); |
191 | |
192 | remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); |
193 | __set_current_state(TASK_RUNNING); |
194 | |
195 | return ret; |
196 | } |
197 | |
198 | /* |
199 | * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative |
200 | * error code. The "count" parameter must be at least the size of a |
201 | * "struct signalfd_siginfo". |
202 | */ |
203 | static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, |
204 | loff_t *ppos) |
205 | { |
206 | struct signalfd_ctx *ctx = file->private_data; |
207 | struct signalfd_siginfo __user *siginfo; |
208 | int nonblock = file->f_flags & O_NONBLOCK; |
209 | ssize_t ret, total = 0; |
210 | siginfo_t info; |
211 | |
212 | count /= sizeof(struct signalfd_siginfo); |
213 | if (!count) |
214 | return -EINVAL; |
215 | |
216 | siginfo = (struct signalfd_siginfo __user *) buf; |
217 | do { |
218 | ret = signalfd_dequeue(ctx, &info, nonblock); |
219 | if (unlikely(ret <= 0)) |
220 | break; |
221 | ret = signalfd_copyinfo(siginfo, &info); |
222 | if (ret < 0) |
223 | break; |
224 | siginfo++; |
225 | total += ret; |
226 | nonblock = 1; |
227 | } while (--count); |
228 | |
229 | return total ? total: ret; |
230 | } |
231 | |
232 | #ifdef CONFIG_PROC_FS |
233 | static int signalfd_show_fdinfo(struct seq_file *m, struct file *f) |
234 | { |
235 | struct signalfd_ctx *ctx = f->private_data; |
236 | sigset_t sigmask; |
237 | |
238 | sigmask = ctx->sigmask; |
239 | signotset(&sigmask); |
240 | render_sigset_t(m, "sigmask:\t", &sigmask); |
241 | |
242 | return 0; |
243 | } |
244 | #endif |
245 | |
246 | static const struct file_operations signalfd_fops = { |
247 | #ifdef CONFIG_PROC_FS |
248 | .show_fdinfo = signalfd_show_fdinfo, |
249 | #endif |
250 | .release = signalfd_release, |
251 | .poll = signalfd_poll, |
252 | .read = signalfd_read, |
253 | .llseek = noop_llseek, |
254 | }; |
255 | |
256 | SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, |
257 | size_t, sizemask, int, flags) |
258 | { |
259 | sigset_t sigmask; |
260 | struct signalfd_ctx *ctx; |
261 | |
262 | /* Check the SFD_* constants for consistency. */ |
263 | BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); |
264 | BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); |
265 | |
266 | if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) |
267 | return -EINVAL; |
268 | |
269 | if (sizemask != sizeof(sigset_t) || |
270 | copy_from_user(&sigmask, user_mask, sizeof(sigmask))) |
271 | return -EINVAL; |
272 | sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); |
273 | signotset(&sigmask); |
274 | |
275 | if (ufd == -1) { |
276 | ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); |
277 | if (!ctx) |
278 | return -ENOMEM; |
279 | |
280 | ctx->sigmask = sigmask; |
281 | |
282 | /* |
283 | * When we call this, the initialization must be complete, since |
284 | * anon_inode_getfd() will install the fd. |
285 | */ |
286 | ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, |
287 | O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); |
288 | if (ufd < 0) |
289 | kfree(ctx); |
290 | } else { |
291 | struct fd f = fdget(ufd); |
292 | if (!f.file) |
293 | return -EBADF; |
294 | ctx = f.file->private_data; |
295 | if (f.file->f_op != &signalfd_fops) { |
296 | fdput(f); |
297 | return -EINVAL; |
298 | } |
299 | spin_lock_irq(¤t->sighand->siglock); |
300 | ctx->sigmask = sigmask; |
301 | spin_unlock_irq(¤t->sighand->siglock); |
302 | |
303 | wake_up(¤t->sighand->signalfd_wqh); |
304 | fdput(f); |
305 | } |
306 | |
307 | return ufd; |
308 | } |
309 | |
310 | SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, |
311 | size_t, sizemask) |
312 | { |
313 | return sys_signalfd4(ufd, user_mask, sizemask, 0); |
314 | } |
315 | |
316 | #ifdef CONFIG_COMPAT |
317 | COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, |
318 | const compat_sigset_t __user *,sigmask, |
319 | compat_size_t, sigsetsize, |
320 | int, flags) |
321 | { |
322 | compat_sigset_t ss32; |
323 | sigset_t tmp; |
324 | sigset_t __user *ksigmask; |
325 | |
326 | if (sigsetsize != sizeof(compat_sigset_t)) |
327 | return -EINVAL; |
328 | if (copy_from_user(&ss32, sigmask, sizeof(ss32))) |
329 | return -EFAULT; |
330 | sigset_from_compat(&tmp, &ss32); |
331 | ksigmask = compat_alloc_user_space(sizeof(sigset_t)); |
332 | if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) |
333 | return -EFAULT; |
334 | |
335 | return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); |
336 | } |
337 | |
338 | COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, |
339 | const compat_sigset_t __user *,sigmask, |
340 | compat_size_t, sigsetsize) |
341 | { |
342 | return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); |
343 | } |
344 | #endif |
345 |
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