include/linux/uio.h

   1 /*
   2  *      Berkeley style UIO structures   -       Alan Cox 1994.
   3  *
   4  *              This program is free software; you can redistribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License, or (at your option) any later version.
   8  */
   9 #ifndef __LINUX_UIO_H
  10 #define __LINUX_UIO_H
  11
  12 #include <linux/kernel.h>
  13 #include <uapi/linux/uio.h>
  14
  15 struct page;
  16
  17 struct kvec {
  18         void *iov_base; /* and that should *never* hold a userland pointer */
  19         size_t iov_len;
  20 };
  21
  22 enum {
  23         ITER_IOVEC = 0,
  24         ITER_KVEC = 2,
  25         ITER_BVEC = 4,
  26 };
  27
  28 struct iov_iter {
  29         int type;
  30         size_t iov_offset;
  31         size_t count;
  32         union {
  33                 const struct iovec *iov;
  34                 const struct bio_vec *bvec;
  35         };
  36         unsigned long nr_segs;
  37 };
  38
  39 /*
  40  * Total number of bytes covered by an iovec.
  41  *
  42  * NOTE that it is not safe to use this function until all the iovec's
  43  * segment lengths have been validated.  Because the individual lengths can
  44  * overflow a size_t when added together.
  45  */
  46 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  47 {
  48         unsigned long seg;
  49         size_t ret = 0;
  50
  51         for (seg = 0; seg < nr_segs; seg++)
  52                 ret += iov[seg].iov_len;
  53         return ret;
  54 }
  55
  56 static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
  57 {
  58         return (struct iovec) {
  59                 .iov_base = iter->iov->iov_base + iter->iov_offset,
  60                 .iov_len = min(iter->count,
  61                                iter->iov->iov_len - iter->iov_offset),
  62         };
  63 }
  64
  65 #define iov_for_each(iov, iter, start)                          \
  66         if (!((start).type & ITER_BVEC))                        \
  67         for (iter = (start);                                    \
  68              (iter).count &&                                    \
  69              ((iov = iov_iter_iovec(&(iter))), 1);              \
  70              iov_iter_advance(&(iter), (iov).iov_len))
  71
  72 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  73
  74 size_t iov_iter_copy_from_user_atomic(struct page *page,
  75                 struct iov_iter *i, unsigned long offset, size_t bytes);
  76 void iov_iter_advance(struct iov_iter *i, size_t bytes);
  77 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
  78 size_t iov_iter_single_seg_count(const struct iov_iter *i);
  79 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
  80                          struct iov_iter *i);
  81 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
  82                          struct iov_iter *i);
  83 unsigned long iov_iter_alignment(const struct iov_iter *i);
  84 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
  85                         unsigned long nr_segs, size_t count);
  86 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
  87                         size_t maxsize, unsigned maxpages, size_t *start);
  88 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
  89                         size_t maxsize, size_t *start);
  90 int iov_iter_npages(const struct iov_iter *i, int maxpages);
  91
  92 static inline size_t iov_iter_count(struct iov_iter *i)
  93 {
  94         return i->count;
  95 }
  96
  97 /*
  98  * Cap the iov_iter by given limit; note that the second argument is
  99  * *not* the new size - it's upper limit for such.  Passing it a value
 100  * greater than the amount of data in iov_iter is fine - it'll just do
 101  * nothing in that case.
 102  */
 103 static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
 104 {
 105         /*
 106          * count doesn't have to fit in size_t - comparison extends both
 107          * operands to u64 here and any value that would be truncated by
 108          * conversion in assignement is by definition greater than all
 109          * values of size_t, including old i->count.
 110          */
 111         if (i->count > count)
 112                 i->count = count;
 113 }
 114
 115 /*
 116  * reexpand a previously truncated iterator; count must be no more than how much
 117  * we had shrunk it.
 118  */
 119 static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 120 {
 121         i->count = count;
 122 }
 123
 124 int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
 125 int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len);
 126 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 127                         int offset, int len);
 128 int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
 129                       int offset, int len);
 130
 131 #endif