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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/eventfd.c
4 *
5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 *
7 */
8
9#include <linux/file.h>
10#include <linux/poll.h>
11#include <linux/init.h>
12#include <linux/fs.h>
13#include <linux/sched/signal.h>
14#include <linux/kernel.h>
15#include <linux/slab.h>
16#include <linux/list.h>
17#include <linux/spinlock.h>
18#include <linux/anon_inodes.h>
19#include <linux/syscalls.h>
20#include <linux/export.h>
21#include <linux/kref.h>
22#include <linux/eventfd.h>
23#include <linux/proc_fs.h>
24#include <linux/seq_file.h>
25#include <linux/idr.h>
26#include <linux/uio.h>
27
28static DEFINE_IDA(eventfd_ida);
29
30struct eventfd_ctx {
31 struct kref kref;
32 wait_queue_head_t wqh;
33 /*
34 * Every time that a write(2) is performed on an eventfd, the
35 * value of the __u64 being written is added to "count" and a
36 * wakeup is performed on "wqh". If EFD_SEMAPHORE flag was not
37 * specified, a read(2) will return the "count" value to userspace,
38 * and will reset "count" to zero. The kernel side eventfd_signal()
39 * also, adds to the "count" counter and issue a wakeup.
40 */
41 __u64 count;
42 unsigned int flags;
43 int id;
44};
45
46/**
47 * eventfd_signal_mask - Increment the event counter
48 * @ctx: [in] Pointer to the eventfd context.
49 * @mask: [in] poll mask
50 *
51 * This function is supposed to be called by the kernel in paths that do not
52 * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
53 * value, and we signal this as overflow condition by returning a EPOLLERR
54 * to poll(2).
55 */
56void eventfd_signal_mask(struct eventfd_ctx *ctx, __poll_t mask)
57{
58 unsigned long flags;
59
60 /*
61 * Deadlock or stack overflow issues can happen if we recurse here
62 * through waitqueue wakeup handlers. If the caller users potentially
63 * nested waitqueues with custom wakeup handlers, then it should
64 * check eventfd_signal_allowed() before calling this function. If
65 * it returns false, the eventfd_signal() call should be deferred to a
66 * safe context.
67 */
68 if (WARN_ON_ONCE(current->in_eventfd))
69 return;
70
71 spin_lock_irqsave(&ctx->wqh.lock, flags);
72 current->in_eventfd = 1;
73 if (ctx->count < ULLONG_MAX)
74 ctx->count++;
75 if (waitqueue_active(&ctx->wqh))
76 wake_up_locked_poll(&ctx->wqh, EPOLLIN | mask);
77 current->in_eventfd = 0;
78 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
79}
80EXPORT_SYMBOL_GPL(eventfd_signal_mask);
81
82static void eventfd_free_ctx(struct eventfd_ctx *ctx)
83{
84 if (ctx->id >= 0)
85 ida_free(&eventfd_ida, ctx->id);
86 kfree(ctx);
87}
88
89static void eventfd_free(struct kref *kref)
90{
91 struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
92
93 eventfd_free_ctx(ctx);
94}
95
96/**
97 * eventfd_ctx_put - Releases a reference to the internal eventfd context.
98 * @ctx: [in] Pointer to eventfd context.
99 *
100 * The eventfd context reference must have been previously acquired either
101 * with eventfd_ctx_fdget() or eventfd_ctx_fileget().
102 */
103void eventfd_ctx_put(struct eventfd_ctx *ctx)
104{
105 kref_put(&ctx->kref, eventfd_free);
106}
107EXPORT_SYMBOL_GPL(eventfd_ctx_put);
108
109static int eventfd_release(struct inode *inode, struct file *file)
110{
111 struct eventfd_ctx *ctx = file->private_data;
112
113 wake_up_poll(&ctx->wqh, EPOLLHUP);
114 eventfd_ctx_put(ctx);
115 return 0;
116}
117
118static __poll_t eventfd_poll(struct file *file, poll_table *wait)
119{
120 struct eventfd_ctx *ctx = file->private_data;
121 __poll_t events = 0;
122 u64 count;
123
124 poll_wait(file, &ctx->wqh, wait);
125
126 /*
127 * All writes to ctx->count occur within ctx->wqh.lock. This read
128 * can be done outside ctx->wqh.lock because we know that poll_wait
129 * takes that lock (through add_wait_queue) if our caller will sleep.
130 *
131 * The read _can_ therefore seep into add_wait_queue's critical
132 * section, but cannot move above it! add_wait_queue's spin_lock acts
133 * as an acquire barrier and ensures that the read be ordered properly
134 * against the writes. The following CAN happen and is safe:
135 *
136 * poll write
137 * ----------------- ------------
138 * lock ctx->wqh.lock (in poll_wait)
139 * count = ctx->count
140 * __add_wait_queue
141 * unlock ctx->wqh.lock
142 * lock ctx->qwh.lock
143 * ctx->count += n
144 * if (waitqueue_active)
145 * wake_up_locked_poll
146 * unlock ctx->qwh.lock
147 * eventfd_poll returns 0
148 *
149 * but the following, which would miss a wakeup, cannot happen:
150 *
151 * poll write
152 * ----------------- ------------
153 * count = ctx->count (INVALID!)
154 * lock ctx->qwh.lock
155 * ctx->count += n
156 * **waitqueue_active is false**
157 * **no wake_up_locked_poll!**
158 * unlock ctx->qwh.lock
159 * lock ctx->wqh.lock (in poll_wait)
160 * __add_wait_queue
161 * unlock ctx->wqh.lock
162 * eventfd_poll returns 0
163 */
164 count = READ_ONCE(ctx->count);
165
166 if (count > 0)
167 events |= EPOLLIN;
168 if (count == ULLONG_MAX)
169 events |= EPOLLERR;
170 if (ULLONG_MAX - 1 > count)
171 events |= EPOLLOUT;
172
173 return events;
174}
175
176void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
177{
178 lockdep_assert_held(&ctx->wqh.lock);
179
180 *cnt = ((ctx->flags & EFD_SEMAPHORE) && ctx->count) ? 1 : ctx->count;
181 ctx->count -= *cnt;
182}
183EXPORT_SYMBOL_GPL(eventfd_ctx_do_read);
184
185/**
186 * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
187 * @ctx: [in] Pointer to eventfd context.
188 * @wait: [in] Wait queue to be removed.
189 * @cnt: [out] Pointer to the 64-bit counter value.
190 *
191 * Returns %0 if successful, or the following error codes:
192 *
193 * -EAGAIN : The operation would have blocked.
194 *
195 * This is used to atomically remove a wait queue entry from the eventfd wait
196 * queue head, and read/reset the counter value.
197 */
198int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
199 __u64 *cnt)
200{
201 unsigned long flags;
202
203 spin_lock_irqsave(&ctx->wqh.lock, flags);
204 eventfd_ctx_do_read(ctx, cnt);
205 __remove_wait_queue(&ctx->wqh, wait);
206 if (*cnt != 0 && waitqueue_active(&ctx->wqh))
207 wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
208 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
209
210 return *cnt != 0 ? 0 : -EAGAIN;
211}
212EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
213
214static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
215{
216 struct file *file = iocb->ki_filp;
217 struct eventfd_ctx *ctx = file->private_data;
218 __u64 ucnt = 0;
219
220 if (iov_iter_count(to) < sizeof(ucnt))
221 return -EINVAL;
222 spin_lock_irq(&ctx->wqh.lock);
223 if (!ctx->count) {
224 if ((file->f_flags & O_NONBLOCK) ||
225 (iocb->ki_flags & IOCB_NOWAIT)) {
226 spin_unlock_irq(&ctx->wqh.lock);
227 return -EAGAIN;
228 }
229
230 if (wait_event_interruptible_locked_irq(ctx->wqh, ctx->count)) {
231 spin_unlock_irq(&ctx->wqh.lock);
232 return -ERESTARTSYS;
233 }
234 }
235 eventfd_ctx_do_read(ctx, &ucnt);
236 current->in_eventfd = 1;
237 if (waitqueue_active(&ctx->wqh))
238 wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
239 current->in_eventfd = 0;
240 spin_unlock_irq(&ctx->wqh.lock);
241 if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt)))
242 return -EFAULT;
243
244 return sizeof(ucnt);
245}
246
247static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
248 loff_t *ppos)
249{
250 struct eventfd_ctx *ctx = file->private_data;
251 ssize_t res;
252 __u64 ucnt;
253
254 if (count != sizeof(ucnt))
255 return -EINVAL;
256 if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
257 return -EFAULT;
258 if (ucnt == ULLONG_MAX)
259 return -EINVAL;
260 spin_lock_irq(&ctx->wqh.lock);
261 res = -EAGAIN;
262 if (ULLONG_MAX - ctx->count > ucnt)
263 res = sizeof(ucnt);
264 else if (!(file->f_flags & O_NONBLOCK)) {
265 res = wait_event_interruptible_locked_irq(ctx->wqh,
266 ULLONG_MAX - ctx->count > ucnt);
267 if (!res)
268 res = sizeof(ucnt);
269 }
270 if (likely(res > 0)) {
271 ctx->count += ucnt;
272 current->in_eventfd = 1;
273 if (waitqueue_active(&ctx->wqh))
274 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
275 current->in_eventfd = 0;
276 }
277 spin_unlock_irq(&ctx->wqh.lock);
278
279 return res;
280}
281
282#ifdef CONFIG_PROC_FS
283static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
284{
285 struct eventfd_ctx *ctx = f->private_data;
286 __u64 cnt;
287
288 spin_lock_irq(&ctx->wqh.lock);
289 cnt = ctx->count;
290 spin_unlock_irq(&ctx->wqh.lock);
291
292 seq_printf(m,
293 "eventfd-count: %16llx\n"
294 "eventfd-id: %d\n"
295 "eventfd-semaphore: %d\n",
296 cnt,
297 ctx->id,
298 !!(ctx->flags & EFD_SEMAPHORE));
299}
300#endif
301
302static const struct file_operations eventfd_fops = {
303#ifdef CONFIG_PROC_FS
304 .show_fdinfo = eventfd_show_fdinfo,
305#endif
306 .release = eventfd_release,
307 .poll = eventfd_poll,
308 .read_iter = eventfd_read,
309 .write = eventfd_write,
310 .llseek = noop_llseek,
311};
312
313/**
314 * eventfd_fget - Acquire a reference of an eventfd file descriptor.
315 * @fd: [in] Eventfd file descriptor.
316 *
317 * Returns a pointer to the eventfd file structure in case of success, or the
318 * following error pointer:
319 *
320 * -EBADF : Invalid @fd file descriptor.
321 * -EINVAL : The @fd file descriptor is not an eventfd file.
322 */
323struct file *eventfd_fget(int fd)
324{
325 struct file *file;
326
327 file = fget(fd);
328 if (!file)
329 return ERR_PTR(-EBADF);
330 if (file->f_op != &eventfd_fops) {
331 fput(file);
332 return ERR_PTR(-EINVAL);
333 }
334
335 return file;
336}
337EXPORT_SYMBOL_GPL(eventfd_fget);
338
339/**
340 * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
341 * @fd: [in] Eventfd file descriptor.
342 *
343 * Returns a pointer to the internal eventfd context, otherwise the error
344 * pointers returned by the following functions:
345 *
346 * eventfd_fget
347 */
348struct eventfd_ctx *eventfd_ctx_fdget(int fd)
349{
350 CLASS(fd, f)(fd);
351 if (fd_empty(f))
352 return ERR_PTR(-EBADF);
353 return eventfd_ctx_fileget(fd_file(f));
354}
355EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
356
357/**
358 * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
359 * @file: [in] Eventfd file pointer.
360 *
361 * Returns a pointer to the internal eventfd context, otherwise the error
362 * pointer:
363 *
364 * -EINVAL : The @fd file descriptor is not an eventfd file.
365 */
366struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
367{
368 struct eventfd_ctx *ctx;
369
370 if (file->f_op != &eventfd_fops)
371 return ERR_PTR(-EINVAL);
372
373 ctx = file->private_data;
374 kref_get(&ctx->kref);
375 return ctx;
376}
377EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
378
379static int do_eventfd(unsigned int count, int flags)
380{
381 struct eventfd_ctx *ctx;
382 struct file *file;
383 int fd;
384
385 /* Check the EFD_* constants for consistency. */
386 BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
387 BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
388 BUILD_BUG_ON(EFD_SEMAPHORE != (1 << 0));
389
390 if (flags & ~EFD_FLAGS_SET)
391 return -EINVAL;
392
393 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
394 if (!ctx)
395 return -ENOMEM;
396
397 kref_init(&ctx->kref);
398 init_waitqueue_head(&ctx->wqh);
399 ctx->count = count;
400 ctx->flags = flags;
401 ctx->id = ida_alloc(&eventfd_ida, GFP_KERNEL);
402
403 flags &= EFD_SHARED_FCNTL_FLAGS;
404 flags |= O_RDWR;
405 fd = get_unused_fd_flags(flags);
406 if (fd < 0)
407 goto err;
408
409 file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
410 if (IS_ERR(file)) {
411 put_unused_fd(fd);
412 fd = PTR_ERR(file);
413 goto err;
414 }
415
416 file->f_mode |= FMODE_NOWAIT;
417 fd_install(fd, file);
418 return fd;
419err:
420 eventfd_free_ctx(ctx);
421 return fd;
422}
423
424SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
425{
426 return do_eventfd(count, flags);
427}
428
429SYSCALL_DEFINE1(eventfd, unsigned int, count)
430{
431 return do_eventfd(count, 0);
432}
433
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/eventfd.c
4 *
5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 *
7 */
8
9#include <linux/file.h>
10#include <linux/poll.h>
11#include <linux/init.h>
12#include <linux/fs.h>
13#include <linux/sched/signal.h>
14#include <linux/kernel.h>
15#include <linux/slab.h>
16#include <linux/list.h>
17#include <linux/spinlock.h>
18#include <linux/anon_inodes.h>
19#include <linux/syscalls.h>
20#include <linux/export.h>
21#include <linux/kref.h>
22#include <linux/eventfd.h>
23#include <linux/proc_fs.h>
24#include <linux/seq_file.h>
25#include <linux/idr.h>
26
27static DEFINE_IDA(eventfd_ida);
28
29struct eventfd_ctx {
30 struct kref kref;
31 wait_queue_head_t wqh;
32 /*
33 * Every time that a write(2) is performed on an eventfd, the
34 * value of the __u64 being written is added to "count" and a
35 * wakeup is performed on "wqh". A read(2) will return the "count"
36 * value to userspace, and will reset "count" to zero. The kernel
37 * side eventfd_signal() also, adds to the "count" counter and
38 * issue a wakeup.
39 */
40 __u64 count;
41 unsigned int flags;
42 int id;
43};
44
45/**
46 * eventfd_signal - Adds @n to the eventfd counter.
47 * @ctx: [in] Pointer to the eventfd context.
48 * @n: [in] Value of the counter to be added to the eventfd internal counter.
49 * The value cannot be negative.
50 *
51 * This function is supposed to be called by the kernel in paths that do not
52 * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
53 * value, and we signal this as overflow condition by returning a EPOLLERR
54 * to poll(2).
55 *
56 * Returns the amount by which the counter was incremented. This will be less
57 * than @n if the counter has overflowed.
58 */
59__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
60{
61 unsigned long flags;
62
63 spin_lock_irqsave(&ctx->wqh.lock, flags);
64 if (ULLONG_MAX - ctx->count < n)
65 n = ULLONG_MAX - ctx->count;
66 ctx->count += n;
67 if (waitqueue_active(&ctx->wqh))
68 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
69 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
70
71 return n;
72}
73EXPORT_SYMBOL_GPL(eventfd_signal);
74
75static void eventfd_free_ctx(struct eventfd_ctx *ctx)
76{
77 if (ctx->id >= 0)
78 ida_simple_remove(&eventfd_ida, ctx->id);
79 kfree(ctx);
80}
81
82static void eventfd_free(struct kref *kref)
83{
84 struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
85
86 eventfd_free_ctx(ctx);
87}
88
89/**
90 * eventfd_ctx_put - Releases a reference to the internal eventfd context.
91 * @ctx: [in] Pointer to eventfd context.
92 *
93 * The eventfd context reference must have been previously acquired either
94 * with eventfd_ctx_fdget() or eventfd_ctx_fileget().
95 */
96void eventfd_ctx_put(struct eventfd_ctx *ctx)
97{
98 kref_put(&ctx->kref, eventfd_free);
99}
100EXPORT_SYMBOL_GPL(eventfd_ctx_put);
101
102static int eventfd_release(struct inode *inode, struct file *file)
103{
104 struct eventfd_ctx *ctx = file->private_data;
105
106 wake_up_poll(&ctx->wqh, EPOLLHUP);
107 eventfd_ctx_put(ctx);
108 return 0;
109}
110
111static __poll_t eventfd_poll(struct file *file, poll_table *wait)
112{
113 struct eventfd_ctx *ctx = file->private_data;
114 __poll_t events = 0;
115 u64 count;
116
117 poll_wait(file, &ctx->wqh, wait);
118
119 /*
120 * All writes to ctx->count occur within ctx->wqh.lock. This read
121 * can be done outside ctx->wqh.lock because we know that poll_wait
122 * takes that lock (through add_wait_queue) if our caller will sleep.
123 *
124 * The read _can_ therefore seep into add_wait_queue's critical
125 * section, but cannot move above it! add_wait_queue's spin_lock acts
126 * as an acquire barrier and ensures that the read be ordered properly
127 * against the writes. The following CAN happen and is safe:
128 *
129 * poll write
130 * ----------------- ------------
131 * lock ctx->wqh.lock (in poll_wait)
132 * count = ctx->count
133 * __add_wait_queue
134 * unlock ctx->wqh.lock
135 * lock ctx->qwh.lock
136 * ctx->count += n
137 * if (waitqueue_active)
138 * wake_up_locked_poll
139 * unlock ctx->qwh.lock
140 * eventfd_poll returns 0
141 *
142 * but the following, which would miss a wakeup, cannot happen:
143 *
144 * poll write
145 * ----------------- ------------
146 * count = ctx->count (INVALID!)
147 * lock ctx->qwh.lock
148 * ctx->count += n
149 * **waitqueue_active is false**
150 * **no wake_up_locked_poll!**
151 * unlock ctx->qwh.lock
152 * lock ctx->wqh.lock (in poll_wait)
153 * __add_wait_queue
154 * unlock ctx->wqh.lock
155 * eventfd_poll returns 0
156 */
157 count = READ_ONCE(ctx->count);
158
159 if (count > 0)
160 events |= EPOLLIN;
161 if (count == ULLONG_MAX)
162 events |= EPOLLERR;
163 if (ULLONG_MAX - 1 > count)
164 events |= EPOLLOUT;
165
166 return events;
167}
168
169static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
170{
171 *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
172 ctx->count -= *cnt;
173}
174
175/**
176 * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
177 * @ctx: [in] Pointer to eventfd context.
178 * @wait: [in] Wait queue to be removed.
179 * @cnt: [out] Pointer to the 64-bit counter value.
180 *
181 * Returns %0 if successful, or the following error codes:
182 *
183 * -EAGAIN : The operation would have blocked.
184 *
185 * This is used to atomically remove a wait queue entry from the eventfd wait
186 * queue head, and read/reset the counter value.
187 */
188int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
189 __u64 *cnt)
190{
191 unsigned long flags;
192
193 spin_lock_irqsave(&ctx->wqh.lock, flags);
194 eventfd_ctx_do_read(ctx, cnt);
195 __remove_wait_queue(&ctx->wqh, wait);
196 if (*cnt != 0 && waitqueue_active(&ctx->wqh))
197 wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
198 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
199
200 return *cnt != 0 ? 0 : -EAGAIN;
201}
202EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
203
204static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
205 loff_t *ppos)
206{
207 struct eventfd_ctx *ctx = file->private_data;
208 ssize_t res;
209 __u64 ucnt = 0;
210 DECLARE_WAITQUEUE(wait, current);
211
212 if (count < sizeof(ucnt))
213 return -EINVAL;
214
215 spin_lock_irq(&ctx->wqh.lock);
216 res = -EAGAIN;
217 if (ctx->count > 0)
218 res = sizeof(ucnt);
219 else if (!(file->f_flags & O_NONBLOCK)) {
220 __add_wait_queue(&ctx->wqh, &wait);
221 for (;;) {
222 set_current_state(TASK_INTERRUPTIBLE);
223 if (ctx->count > 0) {
224 res = sizeof(ucnt);
225 break;
226 }
227 if (signal_pending(current)) {
228 res = -ERESTARTSYS;
229 break;
230 }
231 spin_unlock_irq(&ctx->wqh.lock);
232 schedule();
233 spin_lock_irq(&ctx->wqh.lock);
234 }
235 __remove_wait_queue(&ctx->wqh, &wait);
236 __set_current_state(TASK_RUNNING);
237 }
238 if (likely(res > 0)) {
239 eventfd_ctx_do_read(ctx, &ucnt);
240 if (waitqueue_active(&ctx->wqh))
241 wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
242 }
243 spin_unlock_irq(&ctx->wqh.lock);
244
245 if (res > 0 && put_user(ucnt, (__u64 __user *)buf))
246 return -EFAULT;
247
248 return res;
249}
250
251static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
252 loff_t *ppos)
253{
254 struct eventfd_ctx *ctx = file->private_data;
255 ssize_t res;
256 __u64 ucnt;
257 DECLARE_WAITQUEUE(wait, current);
258
259 if (count < sizeof(ucnt))
260 return -EINVAL;
261 if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
262 return -EFAULT;
263 if (ucnt == ULLONG_MAX)
264 return -EINVAL;
265 spin_lock_irq(&ctx->wqh.lock);
266 res = -EAGAIN;
267 if (ULLONG_MAX - ctx->count > ucnt)
268 res = sizeof(ucnt);
269 else if (!(file->f_flags & O_NONBLOCK)) {
270 __add_wait_queue(&ctx->wqh, &wait);
271 for (res = 0;;) {
272 set_current_state(TASK_INTERRUPTIBLE);
273 if (ULLONG_MAX - ctx->count > ucnt) {
274 res = sizeof(ucnt);
275 break;
276 }
277 if (signal_pending(current)) {
278 res = -ERESTARTSYS;
279 break;
280 }
281 spin_unlock_irq(&ctx->wqh.lock);
282 schedule();
283 spin_lock_irq(&ctx->wqh.lock);
284 }
285 __remove_wait_queue(&ctx->wqh, &wait);
286 __set_current_state(TASK_RUNNING);
287 }
288 if (likely(res > 0)) {
289 ctx->count += ucnt;
290 if (waitqueue_active(&ctx->wqh))
291 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
292 }
293 spin_unlock_irq(&ctx->wqh.lock);
294
295 return res;
296}
297
298#ifdef CONFIG_PROC_FS
299static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
300{
301 struct eventfd_ctx *ctx = f->private_data;
302
303 spin_lock_irq(&ctx->wqh.lock);
304 seq_printf(m, "eventfd-count: %16llx\n",
305 (unsigned long long)ctx->count);
306 spin_unlock_irq(&ctx->wqh.lock);
307 seq_printf(m, "eventfd-id: %d\n", ctx->id);
308}
309#endif
310
311static const struct file_operations eventfd_fops = {
312#ifdef CONFIG_PROC_FS
313 .show_fdinfo = eventfd_show_fdinfo,
314#endif
315 .release = eventfd_release,
316 .poll = eventfd_poll,
317 .read = eventfd_read,
318 .write = eventfd_write,
319 .llseek = noop_llseek,
320};
321
322/**
323 * eventfd_fget - Acquire a reference of an eventfd file descriptor.
324 * @fd: [in] Eventfd file descriptor.
325 *
326 * Returns a pointer to the eventfd file structure in case of success, or the
327 * following error pointer:
328 *
329 * -EBADF : Invalid @fd file descriptor.
330 * -EINVAL : The @fd file descriptor is not an eventfd file.
331 */
332struct file *eventfd_fget(int fd)
333{
334 struct file *file;
335
336 file = fget(fd);
337 if (!file)
338 return ERR_PTR(-EBADF);
339 if (file->f_op != &eventfd_fops) {
340 fput(file);
341 return ERR_PTR(-EINVAL);
342 }
343
344 return file;
345}
346EXPORT_SYMBOL_GPL(eventfd_fget);
347
348/**
349 * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
350 * @fd: [in] Eventfd file descriptor.
351 *
352 * Returns a pointer to the internal eventfd context, otherwise the error
353 * pointers returned by the following functions:
354 *
355 * eventfd_fget
356 */
357struct eventfd_ctx *eventfd_ctx_fdget(int fd)
358{
359 struct eventfd_ctx *ctx;
360 struct fd f = fdget(fd);
361 if (!f.file)
362 return ERR_PTR(-EBADF);
363 ctx = eventfd_ctx_fileget(f.file);
364 fdput(f);
365 return ctx;
366}
367EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
368
369/**
370 * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
371 * @file: [in] Eventfd file pointer.
372 *
373 * Returns a pointer to the internal eventfd context, otherwise the error
374 * pointer:
375 *
376 * -EINVAL : The @fd file descriptor is not an eventfd file.
377 */
378struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
379{
380 struct eventfd_ctx *ctx;
381
382 if (file->f_op != &eventfd_fops)
383 return ERR_PTR(-EINVAL);
384
385 ctx = file->private_data;
386 kref_get(&ctx->kref);
387 return ctx;
388}
389EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
390
391static int do_eventfd(unsigned int count, int flags)
392{
393 struct eventfd_ctx *ctx;
394 int fd;
395
396 /* Check the EFD_* constants for consistency. */
397 BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
398 BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
399
400 if (flags & ~EFD_FLAGS_SET)
401 return -EINVAL;
402
403 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
404 if (!ctx)
405 return -ENOMEM;
406
407 kref_init(&ctx->kref);
408 init_waitqueue_head(&ctx->wqh);
409 ctx->count = count;
410 ctx->flags = flags;
411 ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL);
412
413 fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
414 O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
415 if (fd < 0)
416 eventfd_free_ctx(ctx);
417
418 return fd;
419}
420
421SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
422{
423 return do_eventfd(count, flags);
424}
425
426SYSCALL_DEFINE1(eventfd, unsigned int, count)
427{
428 return do_eventfd(count, 0);
429}
430