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 function
  35  * 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) {
  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  */
  62 static inline __poll_t poll_requested_events(const poll_table *p)
  63 {
  64         return p ? p->_key : ~(__poll_t)0;
  65 }
  66
  67 static 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
  73 static inline bool file_can_poll(struct file *file)
  74 {
  75         return file->f_op->poll;
  76 }
  77
  78 static 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
  85 struct 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  */
  95 struct 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
 105 extern void poll_initwait(struct poll_wqueues *pwq);
 106 extern void poll_freewait(struct poll_wqueues *pwq);
 107 extern u64 select_estimate_accuracy(struct timespec64 *tv);
 108
 109 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 110
 111 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 112                            fd_set __user *exp, struct timespec64 *end_time);
 113
 114 extern 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
 120 static 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
 130 static 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 */