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/sysctl.h>
  12 #include <linux/uaccess.h>
  13 #include <uapi/linux/poll.h>
  14 #include <uapi/linux/eventpoll.h>
  15
  16 extern struct ctl_table epoll_table[]; /* for sysctl */
  17 /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
  18    additional memory. */
  19 #define MAX_STACK_ALLOC 832
  20 #define FRONTEND_STACK_ALLOC    256
  21 #define SELECT_STACK_ALLOC      FRONTEND_STACK_ALLOC
  22 #define POLL_STACK_ALLOC        FRONTEND_STACK_ALLOC
  23 #define WQUEUES_STACK_ALLOC     (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
  24 #define N_INLINE_POLL_ENTRIES   (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
  25
  26 #define DEFAULT_POLLMASK (EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM)
  27
  28 struct poll_table_struct;
  29
  30 /*
  31  * structures and helpers for f_op->poll implementations
  32  */
  33 typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
  34
  35 /*
  36  * Do not touch the structure directly, use the access functions
  37  * poll_does_not_wait() and poll_requested_events() instead.
  38  */
  39 typedef struct poll_table_struct {
  40         poll_queue_proc _qproc;
  41         __poll_t _key;
  42 } poll_table;
  43
  44 static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
  45 {
  46         if (p && p->_qproc && wait_address)
  47                 p->_qproc(filp, wait_address, p);
  48 }
  49
  50 /*
  51  * Return true if it is guaranteed that poll will not wait. This is the case
  52  * if the poll() of another file descriptor in the set got an event, so there
  53  * is no need for waiting.
  54  */
  55 static inline bool poll_does_not_wait(const poll_table *p)
  56 {
  57         return p == NULL || p->_qproc == NULL;
  58 }
  59
  60 /*
  61  * Return the set of events that the application wants to poll for.
  62  * This is useful for drivers that need to know whether a DMA transfer has
  63  * to be started implicitly on poll(). You typically only want to do that
  64  * if the application is actually polling for POLLIN and/or POLLOUT.
  65  */
  66 static inline __poll_t poll_requested_events(const poll_table *p)
  67 {
  68         return p ? p->_key : ~(__poll_t)0;
  69 }
  70
  71 static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
  72 {
  73         pt->_qproc = qproc;
  74         pt->_key   = ~(__poll_t)0; /* all events enabled */
  75 }
  76
  77 static inline bool file_can_poll(struct file *file)
  78 {
  79         return file->f_op->poll;
  80 }
  81
  82 static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
  83 {
  84         if (unlikely(!file->f_op->poll))
  85                 return DEFAULT_POLLMASK;
  86         return file->f_op->poll(file, pt);
  87 }
  88
  89 struct poll_table_entry {
  90         struct file *filp;
  91         __poll_t key;
  92         wait_queue_entry_t wait;
  93         wait_queue_head_t *wait_address;
  94 };
  95
  96 /*
  97  * Structures and helpers for select/poll syscall
  98  */
  99 struct poll_wqueues {
 100         poll_table pt;
 101         struct poll_table_page *table;
 102         struct task_struct *polling_task;
 103         int triggered;
 104         int error;
 105         int inline_index;
 106         struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
 107 };
 108
 109 extern void poll_initwait(struct poll_wqueues *pwq);
 110 extern void poll_freewait(struct poll_wqueues *pwq);
 111 extern u64 select_estimate_accuracy(struct timespec64 *tv);
 112
 113 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 114
 115 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 116                            fd_set __user *exp, struct timespec64 *end_time);
 117
 118 extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
 119                                    long nsec);
 120
 121 #define __MAP(v, from, to) \
 122         (from < to ? (v & from) * (to/from) : (v & from) / (from/to))
 123
 124 static inline __u16 mangle_poll(__poll_t val)
 125 {
 126         __u16 v = (__force __u16)val;
 127 #define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
 128         return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
 129                 M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
 130                 M(HUP) | M(RDHUP) | M(MSG);
 131 #undef M
 132 }
 133
 134 static inline __poll_t demangle_poll(u16 val)
 135 {
 136 #define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
 137         return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
 138                 M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
 139                 M(HUP) | M(RDHUP) | M(MSG);
 140 #undef M
 141 }
 142 #undef __MAP
 143
 144
 145 #endif /* _LINUX_POLL_H */