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