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