include/linux/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
  26 struct poll_table_struct;
  27
  28 /*
  29  * structures and helpers for f_op->poll implementations
  30  */
  31 typedef 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  */
  37 typedef struct poll_table_struct {
  38         poll_queue_proc _qproc;
  39         __poll_t _key;
  40 } poll_table;
  41
  42 static 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  */
  53 static 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  */
  64 static inline __poll_t poll_requested_events(const poll_table *p)
  65 {
  66         return p ? p->_key : ~(__poll_t)0;
  67 }
  68
  69 static 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
  75 static inline bool file_can_poll(struct file *file)
  76 {
  77         return file->f_op->poll;
  78 }
  79
  80 static 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
  87 struct 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  */
  97 struct 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
 107 extern void poll_initwait(struct poll_wqueues *pwq);
 108 extern void poll_freewait(struct poll_wqueues *pwq);
 109 extern u64 select_estimate_accuracy(struct timespec64 *tv);
 110
 111 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 112
 113 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 114                            fd_set __user *exp, struct timespec64 *end_time);
 115
 116 extern 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
 122 static 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
 132 static 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 */