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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#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". A read(2) will return the "count"
37 * value to userspace, and will reset "count" to zero. The kernel
38 * side eventfd_signal() also, adds to the "count" counter and
39 * issue a wakeup.
40 */
41 __u64 count;
42 unsigned int flags;
43 int id;
44};
45
46__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, unsigned mask)
47{
48 unsigned long flags;
49
50 /*
51 * Deadlock or stack overflow issues can happen if we recurse here
52 * through waitqueue wakeup handlers. If the caller users potentially
53 * nested waitqueues with custom wakeup handlers, then it should
54 * check eventfd_signal_allowed() before calling this function. If
55 * it returns false, the eventfd_signal() call should be deferred to a
56 * safe context.
57 */
58 if (WARN_ON_ONCE(current->in_eventfd))
59 return 0;
60
61 spin_lock_irqsave(&ctx->wqh.lock, flags);
62 current->in_eventfd = 1;
63 if (ULLONG_MAX - ctx->count < n)
64 n = ULLONG_MAX - ctx->count;
65 ctx->count += n;
66 if (waitqueue_active(&ctx->wqh))
67 wake_up_locked_poll(&ctx->wqh, EPOLLIN | mask);
68 current->in_eventfd = 0;
69 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
70
71 return n;
72}
73
74/**
75 * eventfd_signal - Adds @n to the eventfd counter.
76 * @ctx: [in] Pointer to the eventfd context.
77 * @n: [in] Value of the counter to be added to the eventfd internal counter.
78 * The value cannot be negative.
79 *
80 * This function is supposed to be called by the kernel in paths that do not
81 * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
82 * value, and we signal this as overflow condition by returning a EPOLLERR
83 * to poll(2).
84 *
85 * Returns the amount by which the counter was incremented. This will be less
86 * than @n if the counter has overflowed.
87 */
88__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
89{
90 return eventfd_signal_mask(ctx, n, 0);
91}
92EXPORT_SYMBOL_GPL(eventfd_signal);
93
94static void eventfd_free_ctx(struct eventfd_ctx *ctx)
95{
96 if (ctx->id >= 0)
97 ida_simple_remove(&eventfd_ida, ctx->id);
98 kfree(ctx);
99}
100
101static void eventfd_free(struct kref *kref)
102{
103 struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
104
105 eventfd_free_ctx(ctx);
106}
107
108/**
109 * eventfd_ctx_put - Releases a reference to the internal eventfd context.
110 * @ctx: [in] Pointer to eventfd context.
111 *
112 * The eventfd context reference must have been previously acquired either
113 * with eventfd_ctx_fdget() or eventfd_ctx_fileget().
114 */
115void eventfd_ctx_put(struct eventfd_ctx *ctx)
116{
117 kref_put(&ctx->kref, eventfd_free);
118}
119EXPORT_SYMBOL_GPL(eventfd_ctx_put);
120
121static int eventfd_release(struct inode *inode, struct file *file)
122{
123 struct eventfd_ctx *ctx = file->private_data;
124
125 wake_up_poll(&ctx->wqh, EPOLLHUP);
126 eventfd_ctx_put(ctx);
127 return 0;
128}
129
130static __poll_t eventfd_poll(struct file *file, poll_table *wait)
131{
132 struct eventfd_ctx *ctx = file->private_data;
133 __poll_t events = 0;
134 u64 count;
135
136 poll_wait(file, &ctx->wqh, wait);
137
138 /*
139 * All writes to ctx->count occur within ctx->wqh.lock. This read
140 * can be done outside ctx->wqh.lock because we know that poll_wait
141 * takes that lock (through add_wait_queue) if our caller will sleep.
142 *
143 * The read _can_ therefore seep into add_wait_queue's critical
144 * section, but cannot move above it! add_wait_queue's spin_lock acts
145 * as an acquire barrier and ensures that the read be ordered properly
146 * against the writes. The following CAN happen and is safe:
147 *
148 * poll write
149 * ----------------- ------------
150 * lock ctx->wqh.lock (in poll_wait)
151 * count = ctx->count
152 * __add_wait_queue
153 * unlock ctx->wqh.lock
154 * lock ctx->qwh.lock
155 * ctx->count += n
156 * if (waitqueue_active)
157 * wake_up_locked_poll
158 * unlock ctx->qwh.lock
159 * eventfd_poll returns 0
160 *
161 * but the following, which would miss a wakeup, cannot happen:
162 *
163 * poll write
164 * ----------------- ------------
165 * count = ctx->count (INVALID!)
166 * lock ctx->qwh.lock
167 * ctx->count += n
168 * **waitqueue_active is false**
169 * **no wake_up_locked_poll!**
170 * unlock ctx->qwh.lock
171 * lock ctx->wqh.lock (in poll_wait)
172 * __add_wait_queue
173 * unlock ctx->wqh.lock
174 * eventfd_poll returns 0
175 */
176 count = READ_ONCE(ctx->count);
177
178 if (count > 0)
179 events |= EPOLLIN;
180 if (count == ULLONG_MAX)
181 events |= EPOLLERR;
182 if (ULLONG_MAX - 1 > count)
183 events |= EPOLLOUT;
184
185 return events;
186}
187
188void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
189{
190 lockdep_assert_held(&ctx->wqh.lock);
191
192 *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
193 ctx->count -= *cnt;
194}
195EXPORT_SYMBOL_GPL(eventfd_ctx_do_read);
196
197/**
198 * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
199 * @ctx: [in] Pointer to eventfd context.
200 * @wait: [in] Wait queue to be removed.
201 * @cnt: [out] Pointer to the 64-bit counter value.
202 *
203 * Returns %0 if successful, or the following error codes:
204 *
205 * -EAGAIN : The operation would have blocked.
206 *
207 * This is used to atomically remove a wait queue entry from the eventfd wait
208 * queue head, and read/reset the counter value.
209 */
210int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
211 __u64 *cnt)
212{
213 unsigned long flags;
214
215 spin_lock_irqsave(&ctx->wqh.lock, flags);
216 eventfd_ctx_do_read(ctx, cnt);
217 __remove_wait_queue(&ctx->wqh, wait);
218 if (*cnt != 0 && waitqueue_active(&ctx->wqh))
219 wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
220 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
221
222 return *cnt != 0 ? 0 : -EAGAIN;
223}
224EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
225
226static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
227{
228 struct file *file = iocb->ki_filp;
229 struct eventfd_ctx *ctx = file->private_data;
230 __u64 ucnt = 0;
231 DECLARE_WAITQUEUE(wait, current);
232
233 if (iov_iter_count(to) < sizeof(ucnt))
234 return -EINVAL;
235 spin_lock_irq(&ctx->wqh.lock);
236 if (!ctx->count) {
237 if ((file->f_flags & O_NONBLOCK) ||
238 (iocb->ki_flags & IOCB_NOWAIT)) {
239 spin_unlock_irq(&ctx->wqh.lock);
240 return -EAGAIN;
241 }
242 __add_wait_queue(&ctx->wqh, &wait);
243 for (;;) {
244 set_current_state(TASK_INTERRUPTIBLE);
245 if (ctx->count)
246 break;
247 if (signal_pending(current)) {
248 __remove_wait_queue(&ctx->wqh, &wait);
249 __set_current_state(TASK_RUNNING);
250 spin_unlock_irq(&ctx->wqh.lock);
251 return -ERESTARTSYS;
252 }
253 spin_unlock_irq(&ctx->wqh.lock);
254 schedule();
255 spin_lock_irq(&ctx->wqh.lock);
256 }
257 __remove_wait_queue(&ctx->wqh, &wait);
258 __set_current_state(TASK_RUNNING);
259 }
260 eventfd_ctx_do_read(ctx, &ucnt);
261 current->in_eventfd = 1;
262 if (waitqueue_active(&ctx->wqh))
263 wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
264 current->in_eventfd = 0;
265 spin_unlock_irq(&ctx->wqh.lock);
266 if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt)))
267 return -EFAULT;
268
269 return sizeof(ucnt);
270}
271
272static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
273 loff_t *ppos)
274{
275 struct eventfd_ctx *ctx = file->private_data;
276 ssize_t res;
277 __u64 ucnt;
278 DECLARE_WAITQUEUE(wait, current);
279
280 if (count < sizeof(ucnt))
281 return -EINVAL;
282 if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
283 return -EFAULT;
284 if (ucnt == ULLONG_MAX)
285 return -EINVAL;
286 spin_lock_irq(&ctx->wqh.lock);
287 res = -EAGAIN;
288 if (ULLONG_MAX - ctx->count > ucnt)
289 res = sizeof(ucnt);
290 else if (!(file->f_flags & O_NONBLOCK)) {
291 __add_wait_queue(&ctx->wqh, &wait);
292 for (res = 0;;) {
293 set_current_state(TASK_INTERRUPTIBLE);
294 if (ULLONG_MAX - ctx->count > ucnt) {
295 res = sizeof(ucnt);
296 break;
297 }
298 if (signal_pending(current)) {
299 res = -ERESTARTSYS;
300 break;
301 }
302 spin_unlock_irq(&ctx->wqh.lock);
303 schedule();
304 spin_lock_irq(&ctx->wqh.lock);
305 }
306 __remove_wait_queue(&ctx->wqh, &wait);
307 __set_current_state(TASK_RUNNING);
308 }
309 if (likely(res > 0)) {
310 ctx->count += ucnt;
311 current->in_eventfd = 1;
312 if (waitqueue_active(&ctx->wqh))
313 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
314 current->in_eventfd = 0;
315 }
316 spin_unlock_irq(&ctx->wqh.lock);
317
318 return res;
319}
320
321#ifdef CONFIG_PROC_FS
322static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
323{
324 struct eventfd_ctx *ctx = f->private_data;
325
326 spin_lock_irq(&ctx->wqh.lock);
327 seq_printf(m, "eventfd-count: %16llx\n",
328 (unsigned long long)ctx->count);
329 spin_unlock_irq(&ctx->wqh.lock);
330 seq_printf(m, "eventfd-id: %d\n", ctx->id);
331}
332#endif
333
334static const struct file_operations eventfd_fops = {
335#ifdef CONFIG_PROC_FS
336 .show_fdinfo = eventfd_show_fdinfo,
337#endif
338 .release = eventfd_release,
339 .poll = eventfd_poll,
340 .read_iter = eventfd_read,
341 .write = eventfd_write,
342 .llseek = noop_llseek,
343};
344
345/**
346 * eventfd_fget - Acquire a reference of an eventfd file descriptor.
347 * @fd: [in] Eventfd file descriptor.
348 *
349 * Returns a pointer to the eventfd file structure in case of success, or the
350 * following error pointer:
351 *
352 * -EBADF : Invalid @fd file descriptor.
353 * -EINVAL : The @fd file descriptor is not an eventfd file.
354 */
355struct file *eventfd_fget(int fd)
356{
357 struct file *file;
358
359 file = fget(fd);
360 if (!file)
361 return ERR_PTR(-EBADF);
362 if (file->f_op != &eventfd_fops) {
363 fput(file);
364 return ERR_PTR(-EINVAL);
365 }
366
367 return file;
368}
369EXPORT_SYMBOL_GPL(eventfd_fget);
370
371/**
372 * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
373 * @fd: [in] Eventfd file descriptor.
374 *
375 * Returns a pointer to the internal eventfd context, otherwise the error
376 * pointers returned by the following functions:
377 *
378 * eventfd_fget
379 */
380struct eventfd_ctx *eventfd_ctx_fdget(int fd)
381{
382 struct eventfd_ctx *ctx;
383 struct fd f = fdget(fd);
384 if (!f.file)
385 return ERR_PTR(-EBADF);
386 ctx = eventfd_ctx_fileget(f.file);
387 fdput(f);
388 return ctx;
389}
390EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
391
392/**
393 * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
394 * @file: [in] Eventfd file pointer.
395 *
396 * Returns a pointer to the internal eventfd context, otherwise the error
397 * pointer:
398 *
399 * -EINVAL : The @fd file descriptor is not an eventfd file.
400 */
401struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
402{
403 struct eventfd_ctx *ctx;
404
405 if (file->f_op != &eventfd_fops)
406 return ERR_PTR(-EINVAL);
407
408 ctx = file->private_data;
409 kref_get(&ctx->kref);
410 return ctx;
411}
412EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
413
414static int do_eventfd(unsigned int count, int flags)
415{
416 struct eventfd_ctx *ctx;
417 struct file *file;
418 int fd;
419
420 /* Check the EFD_* constants for consistency. */
421 BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
422 BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
423
424 if (flags & ~EFD_FLAGS_SET)
425 return -EINVAL;
426
427 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
428 if (!ctx)
429 return -ENOMEM;
430
431 kref_init(&ctx->kref);
432 init_waitqueue_head(&ctx->wqh);
433 ctx->count = count;
434 ctx->flags = flags;
435 ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL);
436
437 flags &= EFD_SHARED_FCNTL_FLAGS;
438 flags |= O_RDWR;
439 fd = get_unused_fd_flags(flags);
440 if (fd < 0)
441 goto err;
442
443 file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
444 if (IS_ERR(file)) {
445 put_unused_fd(fd);
446 fd = PTR_ERR(file);
447 goto err;
448 }
449
450 file->f_mode |= FMODE_NOWAIT;
451 fd_install(fd, file);
452 return fd;
453err:
454 eventfd_free_ctx(ctx);
455 return fd;
456}
457
458SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
459{
460 return do_eventfd(count, flags);
461}
462
463SYSCALL_DEFINE1(eventfd, unsigned int, count)
464{
465 return do_eventfd(count, 0);
466}
467