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b215e283 DL |
1 | /* |
2 | * fs/timerfd.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * | |
6 | * | |
7 | * Thanks to Thomas Gleixner for code reviews and useful comments. | |
8 | * | |
9 | */ | |
10 | ||
11 | #include <linux/file.h> | |
12 | #include <linux/poll.h> | |
13 | #include <linux/init.h> | |
14 | #include <linux/fs.h> | |
15 | #include <linux/sched.h> | |
16 | #include <linux/kernel.h> | |
5a0e3ad6 | 17 | #include <linux/slab.h> |
b215e283 DL |
18 | #include <linux/list.h> |
19 | #include <linux/spinlock.h> | |
20 | #include <linux/time.h> | |
21 | #include <linux/hrtimer.h> | |
22 | #include <linux/anon_inodes.h> | |
23 | #include <linux/timerfd.h> | |
45cc2b96 | 24 | #include <linux/syscalls.h> |
b215e283 DL |
25 | |
26 | struct timerfd_ctx { | |
27 | struct hrtimer tmr; | |
28 | ktime_t tintv; | |
b215e283 | 29 | wait_queue_head_t wqh; |
4d672e7a | 30 | u64 ticks; |
b215e283 | 31 | int expired; |
4d672e7a | 32 | int clockid; |
b215e283 DL |
33 | }; |
34 | ||
35 | /* | |
36 | * This gets called when the timer event triggers. We set the "expired" | |
37 | * flag, but we do not re-arm the timer (in case it's necessary, | |
4d672e7a | 38 | * tintv.tv64 != 0) until the timer is accessed. |
b215e283 DL |
39 | */ |
40 | static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) | |
41 | { | |
42 | struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); | |
43 | unsigned long flags; | |
44 | ||
18963c01 | 45 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
b215e283 | 46 | ctx->expired = 1; |
4d672e7a | 47 | ctx->ticks++; |
b215e283 | 48 | wake_up_locked(&ctx->wqh); |
18963c01 | 49 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
50 | |
51 | return HRTIMER_NORESTART; | |
52 | } | |
53 | ||
4d672e7a DL |
54 | static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) |
55 | { | |
76369470 | 56 | ktime_t remaining; |
4d672e7a | 57 | |
76369470 | 58 | remaining = hrtimer_expires_remaining(&ctx->tmr); |
4d672e7a DL |
59 | return remaining.tv64 < 0 ? ktime_set(0, 0): remaining; |
60 | } | |
61 | ||
62 | static void timerfd_setup(struct timerfd_ctx *ctx, int flags, | |
b215e283 DL |
63 | const struct itimerspec *ktmr) |
64 | { | |
65 | enum hrtimer_mode htmode; | |
66 | ktime_t texp; | |
67 | ||
68 | htmode = (flags & TFD_TIMER_ABSTIME) ? | |
69 | HRTIMER_MODE_ABS: HRTIMER_MODE_REL; | |
70 | ||
71 | texp = timespec_to_ktime(ktmr->it_value); | |
72 | ctx->expired = 0; | |
4d672e7a | 73 | ctx->ticks = 0; |
b215e283 | 74 | ctx->tintv = timespec_to_ktime(ktmr->it_interval); |
4d672e7a | 75 | hrtimer_init(&ctx->tmr, ctx->clockid, htmode); |
76369470 | 76 | hrtimer_set_expires(&ctx->tmr, texp); |
b215e283 DL |
77 | ctx->tmr.function = timerfd_tmrproc; |
78 | if (texp.tv64 != 0) | |
79 | hrtimer_start(&ctx->tmr, texp, htmode); | |
80 | } | |
81 | ||
82 | static int timerfd_release(struct inode *inode, struct file *file) | |
83 | { | |
84 | struct timerfd_ctx *ctx = file->private_data; | |
85 | ||
86 | hrtimer_cancel(&ctx->tmr); | |
87 | kfree(ctx); | |
88 | return 0; | |
89 | } | |
90 | ||
91 | static unsigned int timerfd_poll(struct file *file, poll_table *wait) | |
92 | { | |
93 | struct timerfd_ctx *ctx = file->private_data; | |
94 | unsigned int events = 0; | |
95 | unsigned long flags; | |
96 | ||
97 | poll_wait(file, &ctx->wqh, wait); | |
98 | ||
18963c01 | 99 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
4d672e7a | 100 | if (ctx->ticks) |
b215e283 | 101 | events |= POLLIN; |
18963c01 | 102 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
103 | |
104 | return events; | |
105 | } | |
106 | ||
107 | static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, | |
108 | loff_t *ppos) | |
109 | { | |
110 | struct timerfd_ctx *ctx = file->private_data; | |
111 | ssize_t res; | |
09828402 | 112 | u64 ticks = 0; |
b215e283 DL |
113 | |
114 | if (count < sizeof(ticks)) | |
115 | return -EINVAL; | |
18963c01 | 116 | spin_lock_irq(&ctx->wqh.lock); |
8120a8aa MN |
117 | if (file->f_flags & O_NONBLOCK) |
118 | res = -EAGAIN; | |
119 | else | |
120 | res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks); | |
4d672e7a DL |
121 | if (ctx->ticks) { |
122 | ticks = ctx->ticks; | |
123 | if (ctx->expired && ctx->tintv.tv64) { | |
b215e283 DL |
124 | /* |
125 | * If tintv.tv64 != 0, this is a periodic timer that | |
126 | * needs to be re-armed. We avoid doing it in the timer | |
127 | * callback to avoid DoS attacks specifying a very | |
128 | * short timer period. | |
129 | */ | |
4d672e7a DL |
130 | ticks += hrtimer_forward_now(&ctx->tmr, |
131 | ctx->tintv) - 1; | |
b215e283 | 132 | hrtimer_restart(&ctx->tmr); |
4d672e7a DL |
133 | } |
134 | ctx->expired = 0; | |
135 | ctx->ticks = 0; | |
b215e283 | 136 | } |
18963c01 | 137 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 | 138 | if (ticks) |
09828402 | 139 | res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); |
b215e283 DL |
140 | return res; |
141 | } | |
142 | ||
143 | static const struct file_operations timerfd_fops = { | |
144 | .release = timerfd_release, | |
145 | .poll = timerfd_poll, | |
146 | .read = timerfd_read, | |
147 | }; | |
148 | ||
4d672e7a DL |
149 | static struct file *timerfd_fget(int fd) |
150 | { | |
151 | struct file *file; | |
152 | ||
153 | file = fget(fd); | |
154 | if (!file) | |
155 | return ERR_PTR(-EBADF); | |
156 | if (file->f_op != &timerfd_fops) { | |
157 | fput(file); | |
158 | return ERR_PTR(-EINVAL); | |
159 | } | |
160 | ||
161 | return file; | |
162 | } | |
163 | ||
836f92ad | 164 | SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags) |
b215e283 | 165 | { |
2030a42c | 166 | int ufd; |
b215e283 | 167 | struct timerfd_ctx *ctx; |
b215e283 | 168 | |
e38b36f3 UD |
169 | /* Check the TFD_* constants for consistency. */ |
170 | BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC); | |
171 | BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK); | |
172 | ||
610d18f4 DL |
173 | if ((flags & ~TFD_CREATE_FLAGS) || |
174 | (clockid != CLOCK_MONOTONIC && | |
175 | clockid != CLOCK_REALTIME)) | |
b215e283 | 176 | return -EINVAL; |
4d672e7a DL |
177 | |
178 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
179 | if (!ctx) | |
180 | return -ENOMEM; | |
181 | ||
182 | init_waitqueue_head(&ctx->wqh); | |
183 | ctx->clockid = clockid; | |
184 | hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS); | |
185 | ||
11fcb6c1 | 186 | ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx, |
628ff7c1 | 187 | O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS)); |
2030a42c | 188 | if (ufd < 0) |
4d672e7a | 189 | kfree(ctx); |
4d672e7a DL |
190 | |
191 | return ufd; | |
192 | } | |
193 | ||
836f92ad HC |
194 | SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, |
195 | const struct itimerspec __user *, utmr, | |
196 | struct itimerspec __user *, otmr) | |
4d672e7a DL |
197 | { |
198 | struct file *file; | |
199 | struct timerfd_ctx *ctx; | |
200 | struct itimerspec ktmr, kotmr; | |
201 | ||
202 | if (copy_from_user(&ktmr, utmr, sizeof(ktmr))) | |
203 | return -EFAULT; | |
204 | ||
610d18f4 DL |
205 | if ((flags & ~TFD_SETTIME_FLAGS) || |
206 | !timespec_valid(&ktmr.it_value) || | |
b215e283 DL |
207 | !timespec_valid(&ktmr.it_interval)) |
208 | return -EINVAL; | |
209 | ||
4d672e7a DL |
210 | file = timerfd_fget(ufd); |
211 | if (IS_ERR(file)) | |
212 | return PTR_ERR(file); | |
213 | ctx = file->private_data; | |
b215e283 | 214 | |
4d672e7a DL |
215 | /* |
216 | * We need to stop the existing timer before reprogramming | |
217 | * it to the new values. | |
218 | */ | |
219 | for (;;) { | |
220 | spin_lock_irq(&ctx->wqh.lock); | |
221 | if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) | |
222 | break; | |
18963c01 | 223 | spin_unlock_irq(&ctx->wqh.lock); |
4d672e7a | 224 | cpu_relax(); |
b215e283 DL |
225 | } |
226 | ||
4d672e7a DL |
227 | /* |
228 | * If the timer is expired and it's periodic, we need to advance it | |
229 | * because the caller may want to know the previous expiration time. | |
230 | * We do not update "ticks" and "expired" since the timer will be | |
231 | * re-programmed again in the following timerfd_setup() call. | |
232 | */ | |
233 | if (ctx->expired && ctx->tintv.tv64) | |
234 | hrtimer_forward_now(&ctx->tmr, ctx->tintv); | |
b215e283 | 235 | |
4d672e7a DL |
236 | kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
237 | kotmr.it_interval = ktime_to_timespec(ctx->tintv); | |
238 | ||
239 | /* | |
240 | * Re-program the timer to the new value ... | |
241 | */ | |
242 | timerfd_setup(ctx, flags, &ktmr); | |
243 | ||
244 | spin_unlock_irq(&ctx->wqh.lock); | |
245 | fput(file); | |
246 | if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr))) | |
247 | return -EFAULT; | |
248 | ||
249 | return 0; | |
250 | } | |
251 | ||
d4e82042 | 252 | SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr) |
4d672e7a DL |
253 | { |
254 | struct file *file; | |
255 | struct timerfd_ctx *ctx; | |
256 | struct itimerspec kotmr; | |
257 | ||
258 | file = timerfd_fget(ufd); | |
259 | if (IS_ERR(file)) | |
260 | return PTR_ERR(file); | |
261 | ctx = file->private_data; | |
262 | ||
263 | spin_lock_irq(&ctx->wqh.lock); | |
264 | if (ctx->expired && ctx->tintv.tv64) { | |
265 | ctx->expired = 0; | |
266 | ctx->ticks += | |
267 | hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1; | |
268 | hrtimer_restart(&ctx->tmr); | |
269 | } | |
270 | kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); | |
271 | kotmr.it_interval = ktime_to_timespec(ctx->tintv); | |
272 | spin_unlock_irq(&ctx->wqh.lock); | |
273 | fput(file); | |
274 | ||
275 | return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0; | |
b215e283 DL |
276 | } |
277 |