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 functions
35 * poll_does_not_wait() and 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 && wait_address)
45		p->_qproc(filp, wait_address, p);
46}
47
48/*
49 * Return true if it is guaranteed that poll will not wait. This is the case
50 * if the poll() of another file descriptor in the set got an event, so there
51 * is no need for waiting.
52 */
53static inline bool poll_does_not_wait(const poll_table *p)
54{
55	return p == NULL || p->_qproc == NULL;
56}
57
58/*
59 * Return the set of events that the application wants to poll for.
60 * This is useful for drivers that need to know whether a DMA transfer has
61 * to be started implicitly on poll(). You typically only want to do that
62 * if the application is actually polling for POLLIN and/or POLLOUT.
63 */
64static inline __poll_t poll_requested_events(const poll_table *p)
65{
66	return p ? p->_key : ~(__poll_t)0;
67}
68
69static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
70{
71	pt->_qproc = qproc;
72	pt->_key   = ~(__poll_t)0; /* all events enabled */
73}
74
75static inline bool file_can_poll(struct file *file)
76{
77	return file->f_op->poll;
78}
79
80static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
81{
82	if (unlikely(!file->f_op->poll))
83		return DEFAULT_POLLMASK;
84	return file->f_op->poll(file, pt);
85}
86
87struct poll_table_entry {
88	struct file *filp;
89	__poll_t key;
90	wait_queue_entry_t wait;
91	wait_queue_head_t *wait_address;
92};
93
94/*
95 * Structures and helpers for select/poll syscall
96 */
97struct poll_wqueues {
98	poll_table pt;
99	struct poll_table_page *table;
100	struct task_struct *polling_task;
101	int triggered;
102	int error;
103	int inline_index;
104	struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
105};
106
107extern void poll_initwait(struct poll_wqueues *pwq);
108extern void poll_freewait(struct poll_wqueues *pwq);
109extern u64 select_estimate_accuracy(struct timespec64 *tv);
110
111#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
112
113extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
114			   fd_set __user *exp, struct timespec64 *end_time);
115
116extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
117				   long nsec);
118
119#define __MAP(v, from, to) \
120	(from < to ? (v & from) * (to/from) : (v & from) / (from/to))
121
122static inline __u16 mangle_poll(__poll_t val)
123{
124	__u16 v = (__force __u16)val;
125#define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
126	return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
127		M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
128		M(HUP) | M(RDHUP) | M(MSG);
129#undef M
130}
131
132static inline __poll_t demangle_poll(u16 val)
133{
134#define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
135	return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
136		M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
137		M(HUP) | M(RDHUP) | M(MSG);
138#undef M
139}
140#undef __MAP
141
142
143#endif /* _LINUX_POLL_H */
144