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