poll.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_POLL_H
  3#define _LINUX_POLL_H
  4
  5
  6#include <linux/compiler.h>
  7#include <linux/ktime.h>
  8#include <linux/wait.h>
  9#include <linux/string.h>
 10#include <linux/fs.h>
 11#include <linux/uaccess.h>
 12#include <uapi/linux/poll.h>
 13#include <uapi/linux/eventpoll.h>
 14
 15/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
 16   additional memory. */
 17#define MAX_STACK_ALLOC 832
 18#define FRONTEND_STACK_ALLOC	256
 19#define SELECT_STACK_ALLOC	FRONTEND_STACK_ALLOC
 20#define POLL_STACK_ALLOC	FRONTEND_STACK_ALLOC
 21#define WQUEUES_STACK_ALLOC	(MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
 22#define N_INLINE_POLL_ENTRIES	(WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
 23
 24#define DEFAULT_POLLMASK (EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM)
 25
 26struct poll_table_struct;
 27
 28/*
 29 * structures and helpers for f_op->poll implementations
 30 */
 31typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
 32
 33/*
 34 * Do not touch the structure directly, use the access function
 35 * poll_requested_events() instead.
 36 */
 37typedef struct poll_table_struct {
 38	poll_queue_proc _qproc;
 39	__poll_t _key;
 40} poll_table;
 41
 42static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
 43{
 44	if (p && p->_qproc) {
 45		p->_qproc(filp, wait_address, p);
 46		/*
 47		 * This memory barrier is paired in the wq_has_sleeper().
 48		 * See the comment above prepare_to_wait(), we need to
 49		 * ensure that subsequent tests in this thread can't be
 50		 * reordered with __add_wait_queue() in _qproc() paths.
 51		 */
 52		smp_mb();
 53	}
 54}
 55
 56/*
 57 * Return the set of events that the application wants to poll for.
 58 * This is useful for drivers that need to know whether a DMA transfer has
 59 * to be started implicitly on poll(). You typically only want to do that
 60 * if the application is actually polling for POLLIN and/or POLLOUT.
 61 */
 62static inline __poll_t poll_requested_events(const poll_table *p)
 63{
 64	return p ? p->_key : ~(__poll_t)0;
 65}
 66
 67static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
 68{
 69	pt->_qproc = qproc;
 70	pt->_key   = ~(__poll_t)0; /* all events enabled */
 71}
 72
 73static inline bool file_can_poll(struct file *file)
 74{
 75	return file->f_op->poll;
 76}
 77
 78static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
 79{
 80	if (unlikely(!file->f_op->poll))
 81		return DEFAULT_POLLMASK;
 82	return file->f_op->poll(file, pt);
 83}
 84
 85struct poll_table_entry {
 86	struct file *filp;
 87	__poll_t key;
 88	wait_queue_entry_t wait;
 89	wait_queue_head_t *wait_address;
 90};
 91
 92/*
 93 * Structures and helpers for select/poll syscall
 94 */
 95struct poll_wqueues {
 96	poll_table pt;
 97	struct poll_table_page *table;
 98	struct task_struct *polling_task;
 99	int triggered;
100	int error;
101	int inline_index;
102	struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
103};
104
105extern void poll_initwait(struct poll_wqueues *pwq);
106extern void poll_freewait(struct poll_wqueues *pwq);
107extern u64 select_estimate_accuracy(struct timespec64 *tv);
108
109#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
110
111extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
112			   fd_set __user *exp, struct timespec64 *end_time);
113
114extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
115				   long nsec);
116
117#define __MAP(v, from, to) \
118	(from < to ? (v & from) * (to/from) : (v & from) / (from/to))
119
120static inline __u16 mangle_poll(__poll_t val)
121{
122	__u16 v = (__force __u16)val;
123#define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
124	return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
125		M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
126		M(HUP) | M(RDHUP) | M(MSG);
127#undef M
128}
129
130static inline __poll_t demangle_poll(u16 val)
131{
132#define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
133	return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
134		M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
135		M(HUP) | M(RDHUP) | M(MSG);
136#undef M
137}
138#undef __MAP
139
140
141#endif /* _LINUX_POLL_H */