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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 | break; |
92 | case __SI_POLL: |
93 | err |= __put_user(kinfo->si_band, &uinfo->ssi_band); |
94 | err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd); |
95 | break; |
96 | case __SI_FAULT: |
97 | err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr); |
98 | #ifdef __ARCH_SI_TRAPNO |
99 | err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno); |
100 | #endif |
101 | break; |
102 | case __SI_CHLD: |
103 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); |
104 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); |
105 | err |= __put_user(kinfo->si_status, &uinfo->ssi_status); |
106 | err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); |
107 | err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); |
108 | break; |
109 | case __SI_RT: /* This is not generated by the kernel as of now. */ |
110 | case __SI_MESGQ: /* But this is */ |
111 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); |
112 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); |
113 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); |
114 | break; |
115 | default: |
116 | /* |
117 | * This case catches also the signals queued by sigqueue(). |
118 | */ |
119 | err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); |
120 | err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); |
121 | err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); |
122 | err |= __put_user(kinfo->si_int, &uinfo->ssi_int); |
123 | break; |
124 | } |
125 | |
126 | return err ? -EFAULT: sizeof(*uinfo); |
127 | } |
128 | |
129 | static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, |
130 | int nonblock) |
131 | { |
132 | ssize_t ret; |
133 | DECLARE_WAITQUEUE(wait, current); |
134 | |
135 | spin_lock_irq(¤t->sighand->siglock); |
136 | ret = dequeue_signal(current, &ctx->sigmask, info); |
137 | switch (ret) { |
138 | case 0: |
139 | if (!nonblock) |
140 | break; |
141 | ret = -EAGAIN; |
142 | default: |
143 | spin_unlock_irq(¤t->sighand->siglock); |
144 | return ret; |
145 | } |
146 | |
147 | add_wait_queue(¤t->sighand->signalfd_wqh, &wait); |
148 | for (;;) { |
149 | set_current_state(TASK_INTERRUPTIBLE); |
150 | ret = dequeue_signal(current, &ctx->sigmask, info); |
151 | if (ret != 0) |
152 | break; |
153 | if (signal_pending(current)) { |
154 | ret = -ERESTARTSYS; |
155 | break; |
156 | } |
157 | spin_unlock_irq(¤t->sighand->siglock); |
158 | schedule(); |
159 | spin_lock_irq(¤t->sighand->siglock); |
160 | } |
161 | spin_unlock_irq(¤t->sighand->siglock); |
162 | |
163 | remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); |
164 | __set_current_state(TASK_RUNNING); |
165 | |
166 | return ret; |
167 | } |
168 | |
169 | /* |
170 | * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative |
171 | * error code. The "count" parameter must be at least the size of a |
172 | * "struct signalfd_siginfo". |
173 | */ |
174 | static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, |
175 | loff_t *ppos) |
176 | { |
177 | struct signalfd_ctx *ctx = file->private_data; |
178 | struct signalfd_siginfo __user *siginfo; |
179 | int nonblock = file->f_flags & O_NONBLOCK; |
180 | ssize_t ret, total = 0; |
181 | siginfo_t info; |
182 | |
183 | count /= sizeof(struct signalfd_siginfo); |
184 | if (!count) |
185 | return -EINVAL; |
186 | |
187 | siginfo = (struct signalfd_siginfo __user *) buf; |
188 | do { |
189 | ret = signalfd_dequeue(ctx, &info, nonblock); |
190 | if (unlikely(ret <= 0)) |
191 | break; |
192 | ret = signalfd_copyinfo(siginfo, &info); |
193 | if (ret < 0) |
194 | break; |
195 | siginfo++; |
196 | total += ret; |
197 | nonblock = 1; |
198 | } while (--count); |
199 | |
200 | return total ? total: ret; |
201 | } |
202 | |
203 | static const struct file_operations signalfd_fops = { |
204 | .release = signalfd_release, |
205 | .poll = signalfd_poll, |
206 | .read = signalfd_read, |
207 | }; |
208 | |
209 | SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, |
210 | size_t, sizemask, int, flags) |
211 | { |
212 | sigset_t sigmask; |
213 | struct signalfd_ctx *ctx; |
214 | |
215 | /* Check the SFD_* constants for consistency. */ |
216 | BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); |
217 | BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); |
218 | |
219 | if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) |
220 | return -EINVAL; |
221 | |
222 | if (sizemask != sizeof(sigset_t) || |
223 | copy_from_user(&sigmask, user_mask, sizeof(sigmask))) |
224 | return -EINVAL; |
225 | sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); |
226 | signotset(&sigmask); |
227 | |
228 | if (ufd == -1) { |
229 | ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); |
230 | if (!ctx) |
231 | return -ENOMEM; |
232 | |
233 | ctx->sigmask = sigmask; |
234 | |
235 | /* |
236 | * When we call this, the initialization must be complete, since |
237 | * anon_inode_getfd() will install the fd. |
238 | */ |
239 | ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, |
240 | O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); |
241 | if (ufd < 0) |
242 | kfree(ctx); |
243 | } else { |
244 | struct file *file = fget(ufd); |
245 | if (!file) |
246 | return -EBADF; |
247 | ctx = file->private_data; |
248 | if (file->f_op != &signalfd_fops) { |
249 | fput(file); |
250 | return -EINVAL; |
251 | } |
252 | spin_lock_irq(¤t->sighand->siglock); |
253 | ctx->sigmask = sigmask; |
254 | spin_unlock_irq(¤t->sighand->siglock); |
255 | |
256 | wake_up(¤t->sighand->signalfd_wqh); |
257 | fput(file); |
258 | } |
259 | |
260 | return ufd; |
261 | } |
262 | |
263 | SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, |
264 | size_t, sizemask) |
265 | { |
266 | return sys_signalfd4(ufd, user_mask, sizemask, 0); |
267 | } |
268 |
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